JP2007264613A - Reflection preventing structure and light emitting element having the reflection preventing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively obtain irregularities giving high total light transmittance at an interface, diffuse reflecting or diffuse transmitting incident light moderately and having low wavelength dependency of the total light transmittance and a diffusion angle. <P>SOLUTION: In a reflection preventing structure, the irregularities have an average groove width Λ and an average depth d satisfying formula (1):0.45×Λ<d and formula (2):3<Λ/λ1<120, wherein λ1>λ2, when wavelengths in an medium 1 and in an medium 2 are defined as λ1 and λ2, respectively, when light is made incident vertically to the surface of the medium 2 in the interface having the irregularities between the medium 1 and the medium 2 and the total light reflectance in the interface is reduced by continuously changing an average refractive index in the depth direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antireflection structure that can be used for various flat displays, white light emitting elements, and the like, and a light emitting element having the antireflection structure.

  Antireflection films are used in many applications, particularly in displays. Further, in recent years, an antireflection structure that can cope with a wide wavelength range has been developed. This antireflection structure is characterized by having a groove width equal to or less than the wavelength, and many people have been working on this antireflection structure (see Non-Patent Documents 1, 2, and 3).

  However, the antireflection structure is difficult to manufacture because the groove width is fine below the wavelength, and is not necessarily widespread. In order to solve this, an antireflection structure may be formed in a resonance region having a groove width equal to or greater than the wavelength. Here, the resonance region refers to a region having a groove width several to several tens of times the wavelength. In fact, there is a document that focuses on the resonance region in the literature on the antireflection structure (see Non-Patent Document 4). However, the reflectance is around 2%, which is inferior to conventional antireflection films and antireflection structures, and has a reflectance wavelength dependency.

  In order to further apply the antireflection structure in the resonance region to white light of a display or illumination, it is important to suppress the wavelength dependency of the emission angle and the reflectance. In order to eliminate chromatic dispersion in antireflection applications, the groove width is not constant as described in Non-Patent Document 1 above, or the groove width is shortened as described in Non-Patent Document 2 and only zero-order light is used. Or a multilayer film (see Non-Patent Document 5) has been employed. However, no attempt has been made to eliminate the wavelength dispersion of the antireflection structure in the resonance region.

  The inventors aimed to fully utilize the low reflectance of the resonance region, and considered reducing the wavelength dependency of the emission angle and the reflectance in this region. The reason for focusing on the resonance region is that machining, which is an inexpensive optical element creation method, can be applied. In addition, when the groove width is large, even if the aspect ratio (aspect ratio) is increased, the structure is less likely to be deformed by the influence of heat and moisture (see Non-Patent Document 6). Therefore, the range of material selection is widened and it can be used for various purposes.

  However, on the other hand, in a structure where the groove width is too large, moire due to interference with a periodic pixel often becomes a problem (see Non-Patent Document 7). Therefore, an optical design that considers not only wavelength dependence but also moire suppression is necessary.

  By the way, it is known that a reflection diffraction grating made of a metal film having a groove width in the resonance region has no significant change in the emission angle distribution even if the wavelength of light incident from an oblique direction is changed (see Non-Patent Document 8). ). In addition, there is an optical element in which the wavelength dependency is eliminated by using a speckle pattern, such as a hologram diffuser, for diffusion purposes, but this diffuser also has a groove width in the resonance region (see Non-Patent Document 9). These are hints as a technique for reducing chromatic dispersion.

 In recent years, attempts have been made to produce irregularities on the surface of the organic EL as an attempt to lower the reflectance in display applications. (See Non-Patent Document 10) Further, attempts have been made to increase the light extraction efficiency by forming irregularities on the surface of the semiconductor light emitting device. Thus, the antireflection structure is industrially useful.

FUJIMOTO Akira and ASAKAWA Koji: “Higher Luminescence LED Using Nanostructured Surface Fabricated by Self-Assembled Block Copolymer Lithography”, Toshiba Review, Vol.60, No.10, 2005, p.32-p.35 Y. Kanamori, M. Sasaki and K. Hane: “Broadband antireflection gratings fabricated upon silicon substrates.”, Optics Letters, Volume 24, Issue 20, 1999, p.1422-p.1424 Ping Sheng, A. N. Bloch and R. S. Stepleman: “Wavelength-selective absorption enhancement in thin-film solar cells”, Applied Physics Letters, 15, 1983, Volume 43, Issue 6, p.579-p.581. L. Escoubas, JJ Simon, M. Loli, G. Berginc, F. Flory and H. Giovannini: “An antireflective silicon grating working in the resonance domain for the near infrared spectral region.”, Optics Communications, Volume 226, 2003 Year, p. 81 to p. 88 H. A. MacLeod: “Thin Film Optical Filters Second Edition”, ADAM HILGER LTD, (UK), (1986), p.85-p.156 Pere Roca-Cusachs, Fe'lix Rico, Elena Marti'nez, Jordi Toset, Ramon Farre 'and Daniel Navajas: “Stability of Microfabricated High Aspect Ratio Structures in Poly (dimethylsiloxane)”, Langmuir, Volume 21, 2005, p. 5542〜p .5548 Makoto Okui, Masaki Kobayashi, Jun Arai and Fumio Okano: “Moire fringe reduction by optical filters in integral three-dimensional imaging on a color flat-panel display”, APPLIED OPTICS, Vol. 44, No. 21, 2005, p. .4475 ~ p .4483 Hiroyuki Ichikawa: “Numerical analysis of microretroreflectors: Transition reflection to diffraction.” Journal of Optics A: Pure Applied Optics, Vol.6, 2004, p.S121-p.S127 Sien Chia: “Fabrication of light-shaping diffusion screens Ying Tsung Lua”, Optics Communications, Vol.214, 2002, p.55-p.63 Toshitaka Nakamura, Naoto Tsutsumi, Noriyuki Juni and Hironaka Fujii: “Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate”, JOURNAL OF APPLIED PHYSICS, Vol. 97, Issue 054505, 2005, p.1. ~ P .5 No. 2003-174191 2005-223100 gazette

  An object of the present invention is to realize an antireflection structure that does not have the above-mentioned problems that occur in the prior art. When a light is incident on a surface of a transmissive diffraction grating that is incident from the vertical, It is an object to design and manufacture a region having a period and depth in which the reflectance is sufficiently small, and the reflection diffraction angle distribution and the transmission diffraction angle distribution, and further, the total reflectance does not vary greatly depending on the wavelength. It is another object of the present invention to eliminate moire by reducing the groove width appropriately to provide a diffusion effect or by making it non-periodic.

Furthermore, the problem of the present invention will be specifically described as follows.
(1) As one of the means for suppressing the wavelength dependency, the depth and the groove width are optimized using the wavelength dependency of the total reflectance as an index. The total reflectance is given by (1−total transmittance) if absorption at the interface is ignored.

(2) As another means for suppressing the wavelength dependence, the second is to optimize the groove width distribution. The diffraction angle interval can be obtained by Fourier transforming the position of the uneven mountain (see Toyohiko Tanida: “Light and Fourier Transform”, Asakura Shoten, 1992, p. 1 to p. 30). If the position is periodic and the diffraction angles are too discrete, a rainbow is likely to occur due to wavelength dispersion. Therefore, it is better to vary the groove width to some extent, but on the other hand, if the variation width is too large, the production becomes difficult. Therefore, it is an object to obtain a fluctuation range that can cope with these conditions.

(3) The lattice shape is optimized so as to reduce the total reflectance. Here, in the resonance region, the transmittance varies greatly depending on whether the tip of the grating is pointed or rounded.

(4) The refractive index of the medium adjacent to the antireflection structure is designed so that the total reflectance becomes small. Even if the reflectance of the antireflection structure alone is small, if there is a large reflection between adjacent media, it will not be useful for antireflection.

In order to solve the above-described problems, the present invention solves the above-described problem, when light is incident on the interface between the medium 1 and the medium 2 having irregularities, the average groove width of the irregularities is Λ, the average depth is d, and the wavelength in the medium 1 Is λ1, the wavelength in the medium 2 is λ2, and has an average groove width Λ and an average depth d satisfying the conditions of the following expressions (1) and (2), and the average refractive index in the depth direction is continuously Provided is an antireflection structure corresponding to a plurality of wavelengths, characterized in that the total reflectance at the interface is reduced by changing.
(1) 0.45 × Λ <d
(2) 4 <Λ / λ1 <120
However, λ1> λ2

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problem, when light is incident on the interface between the transparent medium 1 having the unevenness and the transparent medium 2, the average groove width of the unevenness is Λ, the average depth is d, and the medium Λ1 is the wavelength at 1 and λ2 is the wavelength at the medium 2, and the average groove width Λ and the average depth d satisfy the conditions of the following equations (3) and (4). When the average refractive index in the depth direction is 96 ° or less and continuously changes to prevent reflection of light entering the medium 2 from the medium 1, the surface opposite to the interface of the medium 2 is in contact with the surface. Provided is an antireflection structure for white light in which the refractive index of the medium 3 is different from that of the medium 2 by 0.2 or less, or only one of the orthogonal polarized light is used.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problem, when light is incident on the interface between the transparent medium 1 having the unevenness and the transparent medium 2, the average groove width of the unevenness is Λ, the average depth is d, and the medium Λ1 is the wavelength at 1 and λ2 is the wavelength at the medium 2, and the average groove width Λ and the average depth d satisfy the conditions of the following equations (3) and (4). 96 ° or less, and in the case of preventing reflection of light incident on the medium 1 from the medium 2, the medium 2 itself is a light emitter, or the refractive index of the medium from the medium 2 to the light source is higher than that of the medium 2 An antireflection structure for white light characterized by being equal to each other is provided.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

In the antireflection structure, 80% or more of the groove width of the unevenness is in Λ ± 4%, and the groove width and depth satisfying the conditions of the following expressions (5) and (6) are satisfied at the interface. The total reflection factor may be reduced.
(5) 0.45 × Λ <d
(6) 8 <Λ / λ1 <40

  In the antireflection structure, 80% or more of the uneven groove width falls within the range of average groove width × {1 ± λ1 / Λ}, and more than 50% of the groove width is average groove width × {1 ± λ1 / A configuration that does not fall within the range of (5 · Λ)} may be adopted.

In the antireflection structure for white light, when light is incident on the interface between the medium 1 and the medium 2 having irregularities, the average groove width of the irregularities is Λ, the average depth is d, and the wavelength in the medium 1 is λ1. The wavelength in the medium 2 is λ2, the average groove width Λ and the average depth d satisfying the conditions of the following formulas (3) and (4), the apex angle of the convex portion of the medium 2 is 96 ° or less, The cross-sectional shape is a triangular shape that narrows toward the tip of the convex portion of the medium 2 and the total refractive index at the interface is reduced by continuously changing the average refractive index in the depth direction. It is good.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

  In the antireflection structure for white light, the ratio of the outermost surface of the unevenness of the interface or the flat part of the valley bottom may be 5% or less.

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problem, when light is incident on the interface between the medium 1 and the medium 2 having periodic unevenness, the average groove width of the unevenness is Λ, the average depth is d, Where λ1 is the wavelength at λ2, λ2 is the wavelength at the medium 2, and the average groove width Λ and average depth d satisfying the conditions of the following equations (3) and (4) are satisfied, and the apex angle of the groove is 96 ° or less. In addition, the average refractive index in the depth direction is continuously changed to reduce the total reflectivity at the interface, and the concave / convex shape in which both ends of one period of the concave / convex are substantially axisymmetric triangles on both sides is formed. For variables a, b, and c that define, when a is the base of the left triangle, b is the base of the right triangle, and c is the distance between the peaks when the triangles at both ends are translated, Providing an antireflection structure for white light that includes irregularities on the interface that satisfy the following equations (7) and (8) at both ends of one cycle. Provide.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2
(7) 0.8 <a / b <1.2
(8) c / (a + b)> 1.2 or c / (a + b) <0.8

  The antireflection structure may be configured such that the uneven slope of the interface has an average roughness Ra of λ or less.

  In the present invention, in order to solve the above-described problem, the surface of the medium 2 opposite to the uneven surface of the interface is attached to the surface on the viewer side of the front panel of the display via an adhesive or adhesive. An antireflection structure, wherein the thickness of the adhesive or adhesive is 200λ1 or less, and the refractive index difference between the opposite surface and the adhesive or adhesive is 0.2 or less. Provide a display with.

  In order to solve the above-mentioned problems, the present invention uses the surface opposite to the uneven surface of the interface by being attached to the light emitting surface of the organic or inorganic light emitting element via an adhesive or an adhesive, An antireflection structure, wherein the thickness of the adhesive or adhesive is 20λ1 or less, and the difference in refractive index between the uneven surface of the interface and the opposite surface is 0.01 or more and 0.6 or less Provided is a light-emitting element having

  In the medium 2 having the antireflection structure, the average in a cross section having a value obtained by subtracting the average depth d from the distance between the surface with the unevenness at the interface with the medium 1 and the opposite side is 4λ1 or more and 100λ1 or less. The medium 2 may have a refractive index different by 0.1 or more between the medium 3 and the medium 3 in contact with the medium 2 on the surface opposite to the uneven surface of the medium 1.

  According to the antireflection structure of the present invention, high transmittance at the interface between two different media is given, and at the same time, reflection or transmission diffusion is appropriately performed, and unevenness having small wavelength dependency of transmittance and diffusion angle is provided. It becomes possible to give.

That is, the following effects are produced.
(1) For irregularities having an average groove width equal to or greater than the wavelength, the chromatic dispersion is small even in a periodic structure, and the chromatic dispersion can be further reduced by making the aperiodic.
(2) The groove width can be formed relatively large, the reflectance can be made sufficiently small, and the diffusibility is not impaired. Therefore, an antireflection structure that is easy to manufacture, has a low cost and has a large antireflection effect can be obtained.
(3) By controlling the groove width and depth, a diffuser with a further reduced reflectance can be formed.

(4) From these effects, for example, there are the following advantages. That is, when the incident light is not monochromatic but has a plurality of wavelengths, the same or similar groove shape can be applied to the antireflection for those wavelengths. Since the same or similar groove shape can be applied to a plurality of wavelengths, there is a merit that a plurality of wavelengths can be handled with a tool having the same shape in terms of manufacturing a mold.

  Further, the unevenness transferred from the mold has an advantage that the same unevenness can cope with a plurality of wavelengths. Furthermore, there is an advantage that the unevenness corresponding to each pixel does not need to be used in the case where the unevenness is applied where different colors are arranged like a color filter.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out an antireflection structure according to the present invention will be described in various embodiments (embodiments), and will be described below with reference to the drawings based on examples.

(Summary of Invention)
The present invention relates to a transmissive diffraction grating that is incident from the vertical direction, and has a sufficiently small reflectance when light is incident on the surface perpendicularly. Moreover, the reflection diffraction angle distribution, the transmission diffraction angle distribution, and the total reflectance are Design and manufacture regions with a period and depth that do not vary greatly with wavelength, and further reduce the moiré by making the groove width small enough to have a diffusion effect or by making it aperiodic. It is what.

  In the process of intensively developing a configuration that solves the above problems, the inventors of the present invention have a wavelength of the medium 1 and a wavelength of the medium 2 of λ1 and λ2, respectively, λ1> λ2, and light from the medium 1 to the medium 2 In the case of advancing, the resonance region can be sufficiently used as an antireflection structure, for example, the knowledge that the aspect ratio is 1 or more and the reflectance can be reduced to 0.2% or less is obtained by calculation considering the diffraction effect, It was found that the polarization and the refractive index of the medium can be appropriately controlled.

  On the other hand, when light travels from the medium 2 to the medium 1, the resonance region can be sufficiently used as an antireflection structure. For example, the knowledge that the aspect ratio is 3 or more and the reflectance can be reduced to 1% or less is obtained. In this study, new knowledge was obtained about how to make the lattice shape for controlling the distribution and transmittance of transmitted light.

  Further, in the case where light travels from the medium 1 to the medium 2 and when light travels from the medium 2 to the medium 1, the groove width configuration in which the wavelength dependence of the antireflection structure in the resonance region becomes small in the visible light region. As a result of visual observation, changes in color dispersion and coloring at different periods were clarified using several types of diffraction gratings in the resonance region with similar grating shapes and different periods.

  These findings can also be applied to an uneven structure having a groove width larger than that of the resonance region, which has been mainly based on physico-optical calculations, without considering the diffraction effect. On the other hand, by calculating the relationship between the electric field strength distribution and the reflectance in the resonance region when the groove width and depth change, and by conducting an electric field analysis, we have obtained knowledge to suppress the wavelength dependence of the total reflectance. It was. Based on the above findings, the inventors have conceived the following invention.

That is, in the antireflection structure of the present invention, when light is incident on the interface between the medium 1 and the medium 2 having the unevenness, the average groove width of the unevenness is Λ, the average depth is d, and the wavelength in the medium 1 is set. With λ1 and wavelength of medium 2 as λ2, the average groove width Λ and the average depth d satisfying the conditions of the following formulas (1) and (2) are satisfied, and the average refractive index in the depth direction changes continuously. In this way, the total reflectance at the interface is reduced.
(1) 0.45 × Λ <d
(2) 4 <Λ / λ1 <120
However, λ1> λ2

Furthermore, in the antireflection structure for white light according to the present invention, when light is incident on the interface between the transparent medium 1 having the unevenness and the transparent medium 2, the average groove width of the unevenness is Λ and the average depth is d. The wavelength of the medium 1 is λ1, the wavelength of the medium 2 is λ2, and the average groove width Λ and the average depth d satisfying the conditions of the following expressions (3) and (4) are satisfied. When the angle is 96 ° or less and the average refractive index in the depth direction continuously changes to prevent reflection of light entering the medium 2 from the medium 1, the surface opposite to the interface of the medium 2 The refractive index of the medium 3 in contact with the medium 2 differs from that of the medium 2 by 0.2 or less, or only one of orthogonally polarized light is used.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

  Here, the white light may be white in human eyes for display and lighting applications. For example, it may be a red-blue-green stripe like a color filter. The term “transparent” means that the total light transmittance of the mediums 1 and 2 having the antireflection structure is 80% or more excluding Fresnel loss.

  By reducing the difference between the refractive index of the medium 3 and the refractive index of the medium 2, the total reflectance can be reduced. This refractive index difference is more preferably 0.2 or less, and still more preferably 0.1 or less. By setting it to 0.2 or less, the reflectance can be reduced to 1/4 or less, and by setting it to 0.1 or less, the reflectance can be further reduced to 1/4 or less. The grounds for these numerical values are all based on numerical simulations performed by the present inventors. Also, when the unevenness is striped, in the TM mode where the electric field is perpendicular to the stripe, the reflectance is small even if the refractive index difference is large, but in the TE mode where the electric field is parallel to the stripe, the reflectance is small. growing.

  When layers 1, 3, 4,... Are stacked in order, and light passes from medium 3 to medium 4 onward without medium 3 diffusing incident light, diffusion or light is also applied to medium 4 onward. When there is no absorption effect and there is a possibility that light is reflected on the back surface opposite to the respective incident surfaces, the refractive index difference between adjacent media is preferably 0.2 or less, more preferably Is 0.1 or less. Reflection can be suppressed by reducing the refractive index difference.

  The aspect ratio (average depth d / average groove width Λ) is preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more. The larger the aspect ratio, the lower the reflectivity, and it can be used in a wide range.

  Λ / λ1 is more preferably 4 or more and 120 or less, more preferably 5 or more and 60 or less, still more preferably 10 or more and 40 or less, and even more preferably 15 or more and 30 or less. The larger the wavelength, the less the wavelength dispersion of the diffraction angle due to spectroscopy, but moire tends to occur due to interference with the color filter, for example. When Λ / λ1 is 5 or less or 4 or less, the number of rainbows can be reduced by designing the period and depth as described later.

  When the groove is striped, polarized light whose electric field is parallel to the groove is TE mode (see Reference 1 below, which corresponds to H mode in Reference 1), and polarized light whose electric field is perpendicular to the groove is TM mode ( (Refer to Reference Document 2 below, which corresponds to the H mode of Reference Document 2.) If the difference in refractive index between the media 2 and 3 is large, the TM mode has a low reflectivity. In the case where it is desired to reduce the reflected light in the TM mode, the above antireflection structure can be used.

Reference 1: MG Moharam and TK Gaylord, “Diffraction analysis of dielectric surface-relief gratings”, J. Opt. Soc. Am., Vol. 46, No. 72, 1982, p. 1385-p.
Reference 2: MG Moharam and TK Gaylord: “Rigorous coupled-wave analysis of grating diffraction E-mode polarization and losses,” Optics Communications, Vol. 73, 1983, p. 451-p.

Further, in the antireflection structure for white light according to the present invention, when light is incident on the interface between the transparent medium 1 and the transparent medium 2 having unevenness, the average groove width of the unevenness is Λ and the average depth is d. The wavelength of the medium 1 is λ1, the wavelength of the medium 2 is λ2, and the average groove width Λ and the average depth d satisfying the conditions of the following expressions (3) and (4) are satisfied. The angle is 96 ° or less and the average refractive index in the depth direction continuously changes, preventing reflection of light incident on the medium 1 from the medium 2, and the medium 2 itself is a light emitter, or Provided is an antireflection structure for white light, characterized in that the refractive index of the medium from the medium 2 to the light emitting source is higher than or equal to that of the medium 2.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

  Here, d / Λ is preferably 0.5 or more, more preferably 2 or more, and even more preferably 3 or more. The larger the aspect ratio, the lower the reflectivity, and it can be used in a wide range. Λ / λ1 is more preferably 5 or more and 60 or less, further preferably 10 or more and 40 or less, and still more preferably 15 or more and 30 or less. The larger the wavelength, the less the wavelength dispersion of the diffraction angle due to spectroscopy, but moire tends to occur due to interference with the color filter, for example. When Λ / λ1 is 5 or less or 4 or less, the number of rainbows can be reduced by designing the period and depth as described later.

Further, in order to solve the above-mentioned problems, the present invention has a groove width and depth satisfying the conditions of the following formulas (5) and (6) in which 80% or more of the groove width of the unevenness is in Λ ± 4%. The antireflection structure according to claim 1, wherein the total reflectance at the interface is reduced by having a thickness.
(5) 0.45 × Λ <d
(6) 8 <Λ / λ1 <40

  d / Λ is preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more. The larger the aspect ratio, the lower the reflectivity, and it can be used in a wide range. Λ / λ1 is more preferably 9 or more and 60 or less, further preferably 10 or more and 40 or less, and even more preferably 15 or more and 30 or less. The larger the wavelength, the less the wavelength dispersion of the diffraction angle due to spectroscopy, but moire tends to occur due to interference with the color filter, for example.

  When λ1> λ2, 80% or more of the uneven groove width falls within the range of average groove width × {1 ± λ1 / Λ}, and more than 50% of the groove width is average groove width × {1 ± A configuration that does not fall within the range of λ1 / (5 · Λ)} is preferable. These numerical ranges are the results of numerical simulations performed by the present inventors.

  Lattice grooves can be easily manufactured by providing a sufficient manufacturing accuracy such that 80% or more of the uneven groove width falls within Λ ± 4%. There are two conditions: the accuracy when the mold is machined may vary by Λ ± 4%, and if 80% or more of the groove width is within the accuracy, there is no problem in practical use. Determined from the side. It is more preferable that 90% or more of the groove width is included in the accuracy, and it is more preferable that 95% or more of the groove width is included in the accuracy.

  Furthermore, it is more preferable that 80% or more of the groove width of the unevenness falls within the range of average groove width × {1 ± λ2 / Λ}. Since it is easier to produce a groove whose variation in the groove width is not too large, it is only necessary to vary by a necessary and sufficient λ2. Further, it is preferable that not only the groove width but also the groove depth varies within the range of the average groove depth d × {1 ± λ2 / d}. This variation is particularly effective when the average groove width Λ / λ1 is 3 or more and 9 or less, which is highly wavelength-dependent. By varying the groove width, it is possible to produce irregularities with little dependency on reflectance wavelength.

Further, in the antireflection structure for white light according to the present invention, when light is incident on the interface between the medium 1 and the medium 2 having unevenness, the average groove width of the unevenness is Λ, the average depth is d, and the medium 1 The wavelength is λ1, the wavelength at the medium 2 is λ2, the average groove width Λ and the average depth d satisfying the conditions of the following formulas (3) and (4), and the apex angle of the convex portion of the medium 2 is 96 ° or less. And the cross-sectional shape is a triangular shape converging toward the tip of the convex portion of the medium 2, and the average refractive index in the depth direction is continuously changed to thereby change the total reflectance at the interface. It is characterized by reducing.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2

  d / Λ is preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more. The larger the aspect ratio, the lower the reflectivity, and it can be used in a wide range. Λ / λ1 is more preferably 5 or more and 60 or less, further preferably 10 or more and 40 or less, and still more preferably 15 or more and 30 or less. The larger the wavelength, the less the wavelength dispersion of the diffraction angle due to spectroscopy, but moire tends to occur due to interference with the color filter, for example.

  With such a shape, the transmittance of incident light is improved and the wavelength dependency is also reduced. Incident light is, for example, an image on a display, sunlight on a solar cell panel, and light emitted on a light emitting element.

  It is preferable that the ratio of the outermost surface of the unevenness of the interface or the flat part of the valley bottom is 5% or less. This is because the transmittance is lowered when the flat portion is large. The apex angle of the convex portion of the medium 2 is evaluated by an angle formed by two sides sandwiching the flat portion.

In the antireflection structure for white light according to the present invention, when light is incident on the interface between the medium 1 and the medium 2 having periodic irregularities, the light is incident on the interface between the medium 1 and the medium 2 having irregularities. An average satisfying the conditions of the following formulas (3) and (4) where λ is the average groove width of the irregularities, λ is the average depth, λ1 is the wavelength in the medium 1, and λ2 is the wavelength in the medium 2 when incident. It has a groove width Λ and an average depth d, the apex angle of the groove is 96 ° or less, and the average refractive index in the depth direction is continuously changed to reduce the total reflectance at the interface. As a feature, for variables a, b, and c that define an uneven shape in which both ends of one cycle of unevenness are asymmetric triangles that are axisymmetric to the left and right, a is the base of the left triangle, and b is the base of the right triangle. , C represents the distance between the peaks when the triangles at both ends are attached by translation, the following equations (7) and (8) The irregularities of the interface satisfying the above are included at both ends of one cycle.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
(7) 0.5 <a / b <2
(8) c / (a + b)> 1.2 or c / (a + b) <0.8
However, λ1> λ2

  Here, d / Λ is preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more. The larger the aspect ratio, the lower the reflectivity, and it can be used in a wide range.

  Λ / λ1 is more preferably 5 or more and 60 or less, further preferably 10 or more and 40 or less, and still more preferably 15 or more and 30 or less. The larger the wavelength, the less the wavelength dispersion of the diffraction angle due to spectroscopy, but moire tends to occur due to interference with the color filter, for example.

  When the angle distribution of incident light is only about 10 ° in the half-value width of the luminance distribution in the horizontal direction or the vertical and horizontal directions when viewed from the observer, the luminance distribution through the antireflection structure may not be uniform. At that time, as shown in FIG. 1, the luminance distribution can be made to be uniform by using an asymmetric concavo-convex shape so as to be symmetrical as a whole.

Here, it is preferable that the variable a, b, c defining the uneven shape of FIG. 1 is an antireflection structure having unevenness of the interface satisfying the following expressions (7) and (8).
(7) 0.5 <a / b <2
(8) c / (a + b)> 1.2 or c / (a + b) <0.8

  When there are three or more irregularities to form one cycle, formulas (7) and (8) are applied to the irregularities at both ends of one cycle. The number m in FIG. 1 is preferably 0 or 1 in order to reduce the production cost. When light is required to be emitted symmetrically with respect to the groove, it is more preferable that 0.8 <a / b <1.2.

  6. The antireflection structure according to claim 1, wherein the uneven slope of the interface has an average roughness Ra of λ or less. This is because if the surface is rough, the transmittance is reduced because of irregular reflection at that portion. More preferably, it is 0.5λ or less, and further preferably 0.25λ or less. λ may be 0.55 μm, which is the center wavelength of light in a vacuum in a display or white illumination.

  The surface opposite to the uneven surface of the interface is used by being attached to the surface on the viewer side of the front panel of the display via an adhesive or adhesive, and the thickness of the adhesive or adhesive is 200λ1 or less. In addition, it is preferable that the difference in refractive index between the surface adjacent to the pressure-sensitive adhesive or adhesive on the side not having the unevenness of the interface and the pressure-sensitive adhesive or adhesive is 0.2 or less.

  Here, the transmittance can be increased by setting the thickness of the adhesive to 200λ1 or less. Reflection can be suppressed by setting the difference in refractive index to 0.2 or less.

  Furthermore, the present invention is directed to a light emitting element having the above antireflection structure. That is, this light-emitting element is used by attaching the surface opposite to the uneven surface of the antireflection structure on the emission surface of the organic or inorganic light-emitting element via an adhesive or an adhesive. A light-emitting element having an antireflection structure in which the thickness of an adhesive or an adhesive is 20 μm or less, and the difference in refractive index between the uneven surface and the opposite surface is 0.01 to 0.6 is there.

  Here, the transmittance can be increased by setting the thickness of the adhesive to 200λ1 or less. By making the refractive index difference 0.01 or more and 0.6 or less, reflection of light from the light emitting element can be suppressed.

  The average of the cross section having a value obtained by subtracting the average depth d from the distance between the surface of the medium 2 opposite to the uneven surface and the surface opposite to the medium 1 is 4λ1 or more and 100λ1 or less. It is preferable to adopt an antireflection structure having a refractive index different by 0.1 or more between the medium 3 in contact with the medium 2 on the surface opposite to the uneven surface of the medium.

  When the light-emitting element is in contact with the medium 3 as the medium 4, the light-emitting element generally has a high refractive index. The rate difference is large. Therefore, the average thickness is preferably 8λ1 or more, more preferably 16λ1 or more, in order to fill the difference in refractive index and reduce the reflectance, while reducing the transmittance wavelength dependency of the antireflection structure. On the other hand, in order to increase the light transmittance and increase the uniformity of the inter-interface distance, it is preferably 50λ1 or less, more preferably 32λ1 or less.

(Embodiment 1)
FIG. 2 is a diagram showing a cross section at the interface 60 of two types of media. In FIG. 2A, at the interface 60 between the two types of media 1 and 2, in FIG. 2B, the medium 1 is air and at the interface 60 with the medium 2 (surface of the medium 2). Such a concavo-convex shape is formed. 2 (a) and 2 (b) are shown as enlarged parts in FIG. 2 (c).

  The first embodiment is characterized in that the relationship between the average depth d and the average groove width Λ of the lattice grooves formed by the unevenness at the interface 60 is formed in a range as will be described later. In FIG. 2C, when the wavelength of light in vacuum is λ, the refractive indexes of the medium 1 and the medium 2 are n1 and n2, respectively, and n1 = λ / λ1 and n2 = λ / λ2. However, λ1> λ2. A refractive index can be measured about the cut-out sample using a differential interference microscope and an electron microscope.

  The value of λ varies depending on the purpose of using the antireflection structure, but may be 550 nm, which is the center wavelength, for home displays, solar cells, and general lighting. Antireflection is effective both when light enters medium 1 from medium 1 and when it enters medium 1 from medium 2.

  Here, the “average groove width” in the unevenness of the interface 60 is defined as follows. That is, when the average groove width is a certain cross section at the interface 60 between the medium 1 and the medium 2, the “mountain of the surface” (the “surface” here is located at the lower position in FIG. 2C). The distance from the medium 2 toward the medium 1 side to the adjacent “mountain on the surface” again is defined as a plurality of intervals adjacent to each other in the interface direction (left-right direction in FIG. 2C). This is the sum of the mountains and the average of them. In short, the “average groove width” is an average of groove widths 70 that are intervals (peak intervals) between a plurality of “surface peaks” adjacent to each other in the interface direction.

  Then, the “outermost surface” of the interface 60 is defined as follows. In the cross section of the interface 60 (for example, the cross section shown in FIG. 2C) at a predetermined length in the interface direction (left and right direction in FIG. 2C), vertices A of the top three peaks among the surface peaks. , B, and C from the average height line 10 in the depth direction (the direction toward the lower medium 2 in FIG. 2C), the line 20 having the height of 1.5 × λ A region that falls within the range up to the surface average value −λ × 1.5) is defined as “outermost surface”.

  The line 40 (showing the valley bottom) of the height of the valley farthest from the line 10 (the line showing the outermost average value) of the average values of the heights A, B, and C of the tops of the top three highest peaks A line 30 (a line having a depth of 1/2) is drawn at a height that is half the distance to the line. A locally high place (not a vertex) of each convex portion above the line 30 is defined as a “surface mountain”. When the surface is curved like a lens, it is difficult to simply define a “surface peak” with this definition, but the shape of the reference surface is appropriately defined according to the application.

  The “average depth d” of the grating grooves is the distance between the line drawn through the peak of each surface peak parallel to the line drawn to the average height of the surface peaks and the valley bottom. Note that the straight line connecting the average values of the heights of the mountains is determined by approximating the positions of the peaks at the least squares.

  The medium 1 and the medium 2 are a combination of air and an organic polymer, or an organic polymer and an inorganic compound.

  The shape of the interface 60 is an uneven shape typified by a sawtooth diffraction grating. The pattern seen from the top can be various patterns such as stripes, grids, crater patterns with random holes, and checkered patterns.

  The total reflectance is a ratio of all light that has not transmitted through the interface 60 with respect to incident light when light absorption is ignored. In the present invention, the main object is a wave that behaves linearly with respect to space-time and follows the following wave equation (7) in a one-dimensional system (Toyohiko Yadagai: “Light and Fourier Transform”, Asakura Shoten, 1992, p. 1-p.30).

∂ ² Φ / ∂t ² = c ² × ∂ ² Φ / ∂x ² (7)
Here, Φ is a wave function, t is time, and x is a coordinate indicating the traveling direction of the wave. c is the traveling speed of the wave. The left side is the second partial derivative with respect to time and the right side with respect to the distance.

  The average refractive index in the depth direction changes continuously, because the shape changes smoothly in the depth direction like a triangle or bowl shape instead of a top hat shape as shown in FIG. This means that the change in the average refractive index of each slice when it is cut in parallel is small.

  Further, the surface roughness of the triangular or bowl-shaped slope is preferably less than λ / 4, more preferably less than λ / 8, in terms of the centerline average roughness Ra. The reason is that if the surface is rough, the transmittance is reduced because of irregular reflection at that portion. This Ra is calculated based on the JIS standard, and the cut-off value is ½ of the average groove width Λ and the reference length is 3-4 Λ.

  In the antireflection structure of the present invention, it is not necessary to provide an optical thin film (dielectric multilayer film, etc.) for preventing reflection or fine unevenness having a period equal to or shorter than the wavelength on the slope of the unevenness.

  In the antireflection structure of the present invention configured as described above, the characteristic features of the present invention are as follows. That is, assuming that the average groove width of the irregularities at the interface 60 between the medium 1 and the medium 2 is Λ and the average depth is d, the relationship between the average depth d of the lattice grooves and the average groove width Λ is in the following range. A configuration is preferred. This range is 0.45 × Λ <d, more preferably 0.55 × Λ <d, even more preferably Λ <d, and even more preferably 2 × Λ <d.

  By setting 0.45 × Λ <d, the minimum antireflection function can be achieved. By setting 0.55 × Λ <d, the total reflectivity can be made equivalent to a structure having an average groove width Λ equal to or less than the wavelength. By setting Λ <d, when light is incident on the medium 2 from the medium 1, the total reflectance can be reduced to 0.2% or less, which can be used in a wide range of applications.

  By setting 2 × Λ <d, when light is incident on the medium 2 from the medium 1, the total reflectance can be reduced to 0.1% or less, and an unprecedented transmittance can be obtained in a wide wavelength range. .

  Regarding the wavelength and the average groove width Λ, the following ranges are preferable. This range is 3 <Λ / λ1 <120, more preferably 8 <Λ / λ1 <40, and even more preferably 8 <Λ / λ1 <30.

  By setting 8 <Λ / λ1 <40, the average groove width is increased and the formation becomes easier. By setting 8 <Λ / λ1 <30, the average groove width is shortened and the degree of diffusion is increased, so that moire can be completely prevented.

  If the average depth d is too deep with respect to the average groove width Λ, the wavelength dependence of the total reflectance and the emission angle tends to occur. In addition, this wavelength dependence increases as the period decreases. Therefore, by setting 17 × d / Λ−Λ / λ1 <30, it is possible to prevent the occurrence of rainbows and color unevenness.

  For applications such as a display where it is desired to suppress the occurrence of rainbows and color unevenness, it is better to set 17 × d / Λ−Λ / λ1 <15. The main situation considered here is the case where light that behaves linearly with respect to space-time is incident on the surface perpendicularly.

As described above, in the first embodiment, when light is incident on the interface 60 between the transparent medium 1 and the transparent medium 2 having unevenness, the average groove width of the unevenness is Λ, the average depth is d, The wavelength in the medium 1 is λ1, the wavelength in the medium 2 is λ2, and the average groove width Λ and the average depth d satisfying the following formulas (1) and (2) are satisfied, and the apex angle of the groove is 96 ° or less. In addition, when the average refractive index in the depth direction continuously changes and reflection of light entering the medium 2 from the medium 1 is prevented, the medium 3 in contact with the surface opposite to the interface of the medium 2 (FIG. 20). The refractive index of the light source is different from that of the medium 2 by 0.4 or less, or only one of the orthogonal polarized lights is used, or reflection of light incident on the medium 1 from the medium 2 is prevented. A transparent medium characterized in that the refractive index of the medium from the medium 2 to the light-emitting source is higher than or equal to that of the medium 2 The antireflection structure for white light consisting of the bodies 1 and 2 is preferable.
(1) 0.45 × Λ <d
(2) 3 <Λ / λ1 <120
However, λ1> λ2

  Further, assuming that the valley bottom position (lattice tip position) of the grating grooves is at a position divided into a: b in the width direction of the grating grooves as shown in FIG. The average is desirably in the vicinity of a: b of 0.5: 0.5. This is because the deviation of the angular distribution of the emitted light is reduced.

(Embodiment 2)
The second embodiment is characterized in that all the groove widths 70 are made constant, and the relationship between the average depth d of the grating grooves and the groove width 70 is in the same range as in the first embodiment. In short, in the first embodiment, a constant groove width is used instead of the average groove width. Here, when the groove width is constant, this groove width is called a period. If the groove width 70 is constant, the shape is easier to produce, but if the period is large, moire occurs due to interference with pixels in the display. Therefore, the size of the period is reduced to some extent to give diffusion characteristics.

  By making 80% or more of the uneven groove width into Λ ± 4%, it becomes easy to manufacture a lattice groove. This condition is that the accuracy when machining the mold may vary by Λ ± 4% for the purpose of making the period constant, and if more than 80% of the groove width is included in the accuracy It is determined from two aspects that there is no problem in practical use. It is more preferable that 90% or more of the groove width is included in the accuracy, and it is more preferable that 95% or more of the groove width is included in the accuracy. At this time, if Λ / λ1 <40, moiré is likely to occur. On the other hand, if 8 <Λ / λ1, rainbow is likely to occur.

Also in the second embodiment, as in the first embodiment, when light is incident on the interface 60 between the medium 1 and the medium 2 having the unevenness, the groove width 70 of the unevenness is Λ and the depth is d. The wavelength in the medium 1 is λ1, the wavelength in the medium 2 is λ2, the groove width Λ and the average depth d satisfying the conditions of the following formulas (1) and (2), and the average refraction in the depth direction. An antireflection structure characterized by reducing the total reflectance at the interface 60 by continuously changing the rate is preferred.
(1) 0.45 × Λ <d
(2) 3 <Λ / λ1 <120
However, λ1> λ2

(Embodiment 3)
The third embodiment is characterized in that the groove width is a non-periodic diffraction grating and the groove width distribution is defined as described later. This will be described below. FIG. 5 is a diagram showing the definitions of the incident angle θi, the reflection angle θr, and the angle θt of the transmitted diffracted light 110 with respect to the incident light 90 and the reflected light 100 incident on the antireflection structure in the present invention.

  FIG. 5 is a diagram schematically illustrating the distribution of the diffraction order m of the normal incident light 120. At this time, it is known that the refractive index n1, n2 and the angle generally have the following relationship (Hiroyuki Ichikawa: “Numerical analysis of microretroreflectors: Transition reflection to diffraction.” Journal of Optics A : Pure Applied Optics, Vol.6, 2004, p.S121 to p.S127).

  n1 · sin (θi) −n2 · sin (θt) = m · λ / Λ (8)

When the light is incident perpendicularly to the surface from the medium 1 toward the medium 2 and is emitted substantially parallel to the surface, the diffraction order m emitted in parallel changes from Equation (8) as the period increases. At that time, if m is not 1, how much the period has changed is calculated according to the following equations (9) and (10).
n1 · 0 − n2 · 1 = m · λ / Λ (9)
Here, since m = −n2 · Λ / λ,
1 / m = -λ / (n2 · Λ)
= -Λ2 / Λ (10)

  Therefore, in this case, if m is different from 1, the period has changed by about λ2 / Λ. When the light enters the medium 1 from the medium 2, the index is λ1 / Λ. If the mountain positions are periodic and the diffraction angles are too discrete, a rainbow is likely to occur due to wavelength dispersion. In order to prevent this, it is only necessary to change the groove width to smooth the emission angle distribution.

  From the above examination, it can be seen that if the average groove width × {1 ± λ1 / Λ} fluctuates, the exit angle distribution can be made sufficiently smooth rather than discrete. It is practically sufficient that 80% or more of the groove width of the unevenness fluctuates within this range. Further, it is practically desirable that the fluctuation width is at least the average groove width × {1 ± λ1 / (5 · Λ)}.

  In the above description, how much the variation of the groove width should be increased from the emission angle has been described. However, for the total reflectivity, how much the variation of the groove width should be increased was examined, and as a result, the FDTD method ( From the calculation of the electric field intensity distribution by the time domain difference method) and the calculation of the total reflectance by the RCWA method (strict coupling wave analysis method), we have found that there is a close relationship between the electric field intensity distribution and the reflectance.

  The reason for changing the groove width is that the wavelength dependence can be suppressed because the intensity distribution of the electric field can be controlled by controlling the period and the depth. In the following, a diffraction grating is taken as an example of the medium 2 having unevenness, and the effect of suppressing the wavelength dependency due to the variation of the groove width will be described. The electric field of the diffraction grating film was calculated by changing the grating period, aspect ratio, and substrate thickness, and the influence on the reflection was examined.

  FIG. 8 is a calculation example of the intensity distribution of the scattered light in the TE mode, and one lattice of FIG. 7 is extracted and enlarged. The groove shape of the lattice is an isosceles triangle, the aspect ratio is 1, and the period is 9 times the wavelength λ1. The refractive indexes of the media 1 and 3 are 1 and the media 2 is a diffraction grating film of 1.5.

A), b), a diffraction grating film (a) shown in c), b, c in FIG. 8, substrate thickness _{d s} are different. It can be seen that there are six white areas that are separated from the top and bottom of the lattice base and have high strength. In the diffraction grating films a and c, the white region overlaps the bottom, but the diffraction grating film b does not overlap and the region is not disturbed and has a low reflectance. When the size of the lattice and the thickness of the base material are changed, the reflectance is considered to increase when the white region overlaps the bottom. Thus, the intensity distribution and the reflectance are closely related.

  In the same calculation, the number of white areas is determined by the grating depth and the substrate thickness in the vertical direction and the grating period in the horizontal direction. These numbers are the periodicity of the total reflectance described later with respect to the wavelength calculated by the RCWA method. It turns out that it corresponds to. Since the size of the white region is about 2 · λ2, the wavelength dependency of the reflectance can be reduced by changing the size of the grating with a variation width as large as λ2.

  In the case of a periodic structure, moire does not occur due to the diffusion effect if Λ / λ is 20 or less, but moire occurs when Λ / λ greatly exceeds 20. Therefore, in this case, it is necessary to use an aperiodic diffraction grating. The second embodiment can also be applied as the non-periodic groove width condition. Here, the term “periodic structure” means irregularities having a constant groove width, and the term “non-periodic structure” means a structure where the groove width is not constant. In the present invention, when 80% or more of the groove width of the unevenness falls within Λ ± 4%, it is considered periodic.

(Embodiment 4)
The fourth embodiment is characterized in that the shape of the lattice groove is a triangular “tip concavity” toward the valley bottom of the lattice groove. Here, as shown in FIG. 9, the groove of the “tip concavity” is a triangular hypotenuse that connects a mountain and a valley bottom with a straight line, and the uneven interface 60 comes on or in the side of the triangle. 10 is a groove having a shape as shown in FIG.

  With such a shape, the transmittance of incident light is improved and the wavelength dependency is also reduced. The incident light is, for example, an image on a display, sunlight on a solar cell panel, and light emitted on a light emitting diode.

In FIG. 10, the hypotenuse consists of a curve, and s is less than 1 as the average depth d in the following equation (11) in the xy coordinates.
| 2x / Λ | ^ s + | y / d | ^ s = 1 (11)
However, y <0.

(Embodiment 5)
FIG. 9 shows an example of the fifth embodiment. The lattice groove of this antireflection structure is composed of two straight lines with hypotenuses at the position of a line 140 that is ½ of the depth of the lattice groove. Along the line, only p is inside the line 130 connecting the uneven peaks and valleys.

  In any of the embodiments of the antireflection structure of the present invention, the transmittance can be increased if the grating groove has a configuration that does not leave a flat portion on the top or bottom of the top surface. Here, the valley bottom is a portion connecting the deepest portions of the groove as seen in the cross section with the groove. Specifically, it is preferable that the ratio of the outermost surface or the flat part of the valley bottom is 5% or less.

(Embodiment 6)
The sixth embodiment is a configuration related to the use of the antireflection structure of the present invention. In the sixth embodiment, as shown in FIG. 11, the surface of the antireflection structure that does not have the unevenness of the interface 60 is disposed on the front surface of the front panel (display panel 180) via an adhesive film or adhesive material 170. The configuration is applied to an antireflection structure such as a display. The material of the antireflection structure is preferably an antifouling fluororesin. Alternatively, it is desirable that the resin contains a metal oxide for preventing charging so that dust does not easily adhere.

(Embodiment 7)
This Embodiment 7 is also a structure which concerns on the use of the reflection preventing structure of this invention. In the seventh embodiment, as shown in FIG. 12, the antireflection structure has an adhesive film or adhesive material on the surface of the light emitting diode 19 in which the surface of the interface 60 that does not have irregularities is formed of an organic or inorganic material. It is the structure which is affixed through 170 and used as a diffuser.

  It is desirable that the adhesive film, the pressure-sensitive adhesive film, and the base material serving as an antireflection structure with unevenness have heat resistance. It is preferable that the change in reflectance is 10% or less in a standing test at a temperature of 85 ° C. and a humidity of 85%. Therefore, the glass transition temperature of these materials is preferably 100 ° C. or higher.

  Hereinafter, the present invention will be specifically described with reference to examples. The antireflection structure can be designed only by simulating how the total reflectance changes according to the groove width and aspect ratio as in the present invention.

  A condition was examined in which the fluctuation of the total reflectance is small, moire does not occur, and the wavelength dispersion of the diffraction angle is suppressed by using higher-order diffracted light. As a result, the inventors have obtained the knowledge that the present invention can be implemented by designing and manufacturing as follows.

(Shape design)
Here, the shape design is performed as follows. Commercially available RCWA (Rigorous Coupled Wave Analysis) software can be used to calculate the periodic structure. Other than that, for example, DIFFRACT MOD manufactured by RSOFT or GSOLVER manufactured by Grating Solver Development can be used.

  For the following wavelengths, λ1 described in the first embodiment is used. The design is performed as follows. First, the range of the wavelength used is determined.

  For an isosceles triangular lattice groove, d / Λ is changed from 0.5 to 5 in increments of 0.5. For each d / Λ, the total reflectance is calculated with the horizontal axis Λ / λ. For polarization, it is better to calculate for both TE and TM modes and use the average. The incident direction is calculated by normal incidence with respect to the surface, and the chromaticity is evaluated as an average in the range of ± 5 ° for the strongest diffraction efficiency angle.

  For simplicity, the shape may be determined by calculating only the TE mode. Further, the incident direction is calculated under the condition that the light enters from the medium 1 to the medium 2 and vice versa, and the shape that satisfies both characteristics is searched. For example, the product of both reflectivities is minimized. The change in total reflectance from the shortest wavelength λa to the longest wavelength λb is examined. The incident angle is set to be perpendicular to the surfaces of the media 1 and 2.

In the display, λa is 367 nm, λb is 734 nm, and the like. The standard deviation is calculated by setting Λ / λ to the wavelength as uniform as possible. For example, the calculation is performed in the following increments.
Λ / λ = (11.4, 10.1, 9.09, 8.26, 7.58, 6.99, 6.49, 6.06, 5.68, 5.35, 5.05, 4 .78, 4.55, 4.13, 3.79, 3.50, 3.25, 3.03, 2.84, 2.67, 2.53, 2.39, 2.27)

  In this case, the standard deviation is calculated within a range of 9.09 to 4.55 or 4.55 to 2.27. Within the region of the first embodiment, a condition that the standard deviation / average value is 0.9 or less, preferably 0.3 or less is searched for the total reflectance in the wavelength range. A condition is found where this value is small and Λ is also somewhat small. If it is 0.3 or less, coloring is lost.

Whether it is colored or not can be evaluated with the naked eye, but more objectively. In the CIE 1976 uniform color space L ^* u ^* v ^* with a 2 ° or 10 ° field of view, the chromaticity uv is within u ± 0.8 and v ± 0.8 when the light source gives white of equal energy. It is desirable. When whiteness is required from a television or the like, it is desirable that it is within u ± 0.4 and v ± 0.4.

  FIGS. 13 and 14 show the results of calculating the reflectance by changing d / Λ from 0.5 to 5.0 in increments of 0.5 in the TE mode. FIG. 13 shows the case where light travels from the medium refractive index 1 to the medium refractive index 1.5 region, and FIG. 14 shows the opposite case. At this time, the standard deviation / average value is as shown in Table 1 in FIG. 15 within a range of Λ / λ from 9.09 to 4.55. In Table 1, “Case A” and “Case B” correspond to FIGS. 13 and 14, respectively.

  In the present invention, Case A means that light travels from medium 1 to medium 2, and Case B means that light travels from medium 2 to medium 1. Although the reflectance varies between Λ / λ of 10 and 40, Λ / λ is not significantly different from 9. In FIGS. 13 and 14, periodicity is observed in the variation of total reflectance in the region where Λ / λ is 1 to 5, and Λ / λ peaks in the vicinity of the integer value.

  When the groove width and the average depth d are determined from the ease of manufacturing conditions and diffusion conditions, the shape is determined. In the shape of FIG. 10 or FIG. 9, the groove width and depth are fixed, and the above-mentioned parameters, p or s, are simulated, and an optimum structure is determined from the viewpoint of ease of production and reflectivity. λ is (λa + λb) / 2, and p / Λ is changed from 0 to 0.1 in steps of 0.02. s is varied from 1 to 0.5 in increments of 0.1. Among these, three having a low total reflectivity are selected and a shape that is easy to manufacture is selected.

  Furthermore, a calculation example of design for controlling the diffusion pattern and the reflectance according to the application will be shown. There are the following methods for making the light distribution uniform. In the following, the refractive index n of the diffraction grating is 1.5, and the following cases (1) and (2) are both in the case B. The polarized light is in the TE mode, and the light is incident on the surface perpendicularly.

  (1) Mix lattices with different groove widths, similar to isosceles triangles as shown in FIG. FIG. 17 is a comparison of diffraction angle distributions of diffraction gratings having the same period and different periods. The calculation results are connected by auxiliary lines. s-trans is a lattice having the same groove width, Λ / λ is 9, and d-trans is a groove having different groove widths, and the groove width / λ is 7.2 and 10.8. It can be seen that the ratio of the emission angles distributed in the direction perpendicular to the surface increases with d-trans of different groove widths.

  (2) Using unequal triangles as shown in FIG. 18 and arranging them symmetrically in one cycle. FIG. 19 is a comparison of diffraction angle distributions of diffraction gratings of an isosceles triangle and an unequal triangle. The calculation results are connected by auxiliary lines. The isosceles triangle has Λ / λ of 9 and an aspect ratio of 1. The inequilateral triangle has Λ / λ of 18, d / Λ of 1, and a: b: c of 5: 2: 5. It can be seen that the transmitted light distribution in the direction perpendicular to the surface of the emission angle increases in the unequal triangle as compared to the isosceles triangle.

  In addition, a specific calculation example for increasing the transmittance is shown. In the following description, the refractive index of the medium 1 is 1, the refractive index of the medium 2 is 1.5, the refractive index of the medium 3 is 1.0 to 1.6, and light is incident on the grating surface perpendicularly with Case A.

  FIG. 20 shows a diffraction grating with a back surface on which media 1, 2, and 3 exist. The boundary between each of the media 1 and 3 is considered to be only the interface with the medium 2. When the refractive index difference between the lattice back surfaces of the medium 3 and the medium 2 is reduced, the reflection is reduced.

FIG. 21 shows the total reflectance when the refractive index of the medium 3 in contact with the uneven surface of the medium 2 is changed. The calculation was performed for _ds / λ of medium 3 of 0.55 and 0.65. The isosceles triangle of the lattice has Λ / λ of 9.1 and an aspect ratio of 1. The refractive index of the medium 4 is 1.5. When the refractive index of the medium 3 is within ± 0.2 of the refractive index of the medium 2, a reflectance of 2% or less is obtained.

  The transmittance can be increased by increasing the aspect ratio and making the slope a steep angle. FIG. 23 is a diagram showing a change in reflectance when the aspect ratio is changed. Λ / λ is 9.1 or 18.2, and the polarization is TE or TM mode. As shown in FIG. 22, θ is an incident angle with respect to the inclined surface. It can be seen that the reflectance is lower when the aspect is higher and θ is larger.

  FIG. 25 shows the result of calculating the total reflectivity in the TE mode for three conditions where the lattice shape is an isosceles triangle, a sine curve, and a constriction. The calculation results are connected by auxiliary lines. As shown in FIG. 24, the shape of the tip is y1 = y2, and U = x1 / Λ determines the shape of the tip. 'Sine' is a sinusoidal curve.

  In both cases, n of the medium 1 is 1.5 and d / Λ is 1. The refractive index of medium 0 and medium 2 is 1. The total reflectivity is higher in the order of 'U = 0.35' <'U = 0.25' <'sine', and it can be seen that the total reflectivity is lower in the tapered portion.

  The calculation of the aperiodic structure was performed using calculation software “FDTD software FullWAVE” manufactured by RSOFT or the calculation software “OptiFDTD” manufactured by Cybernet.

  Alternatively, FDTD programs (for example, Saswatee Banerjee, Toyohiko Yatagai and James B. Cole: “Boosting light transmission through interfaces using subwavelength Moth-eye structuring: nonstandard FDTD simulations”, 11th Microoptics Conference (MOC'05), H48, (See p. 212 to p. 213 in 2005), and may be used to calculate aperiodic structures.

  About the obtained shape, the shape which changed the obtained groove width and depth similarly is arranged. For example, the shapes are arranged as shown in FIG. About 10 grating grooves arranged, calculation is performed by FDTD, and it is confirmed that the reflectance is sufficiently small. In addition, another 10 arrangements are calculated. Repeat this to make about 10 pairs in total. While changing this combination at random, a large-area lattice groove is designed.

(Design verification experiment by RCWA)
Furthermore, the relationship between the period, aspect ratio, reflectance, and rainbow was verified by RCWA (strict coupled wave analysis) experiments. Consider the case where light enters the surface irregularities of the medium 2 from the air of the medium 1 as shown in FIG. 6 and the effective interface is only the surface irregularities. FIG. 27 is a diagram showing a method of measuring the total reflectance when only the media 1 and 2 are used. In order to prevent reflection from the back surface of the medium 2, a dove prism having a refractive index difference of 0.1 or less is pasted with an adhesive having a refractive index difference of 0.1 or less.

  As the material of the prism, crystal or general transparent glass can be used. As the adhesive, UV curable resin Sunrad RC-610R can be used. When UV curable resin (Sunrad RC-610R), water, and hexane are sandwiched as the medium 3 between the quartz dove prism and the back surface of the PMMA diffraction grating, the reflectivity of water and hexane is clear compared to UV curable resin. It was visually confirmed that the size was increased.

  Since the refractive index is quartz 1.46, PMMA 1.49, hexane 1.375, and UV curable resin 1.52, the experimental results confirm the calculation results of FIG. Further, the reflectance is measured as follows. An intense light of 514.5 nm is made incident by an argon laser. The unevenness is appropriately rotated in consideration of anisotropy, and measured at a plurality of rotation angles if necessary.

  A polarizer is put in the middle, and the case where the electric field is parallel to and perpendicular to the short axis of anisotropy is measured and averaged later. The short axis of anisotropy is the axis with the shortest average period. Measure with a power meter at regular intervals in a semicircular shape. The interval should be sufficiently short to reduce the error. Considering the distance from the reflection point on the surface and the size of the light receiving element of the power meter, the total reflectance of each point is calculated. When the diffraction pattern is clear, the position of the power meter is adjusted to each diffraction angle. Calculate the sum of each diffraction efficiency.

  Ignore the specular reflection measurement position, or tilt the concavo-convex surface by 5.6 ° and measure the specular reflection light to obtain an alternative value. The background correction of measured values is performed as appropriate. This measurement was tested on a striped acrylic diffraction grating whose lattice shape is an isosceles triangle with a period of 10 μm and a depth of 7 μm, a base material thickness of 2 mm, and a centerline average surface roughness of 60 nm. Went to. As a result, the average of the TE mode and the TM mode has a sufficiently low reflectance of 0.4% for antireflection use. This value coincided with the RCWA calculation result of 0.4%.

  FIG. 28 is a diagram showing a method for measuring coloring and rainbow by diffraction. The rainbow was evaluated visually. Use the light emitted from the illuminator through the flexible light guide. The light is condensed through the iris diaphragm, the lens 1 and the lens 2 and applied to the diffraction grating. The lens 1 collimated the light. The lens 2 has a focal length of 100 mm and a diameter of 80 mm. The light was transmitted and reflected by a diffraction grating and applied to a white paper.

  The illuminator uses a halogen lamp to increase the light intensity and bring it closer to white. The light emitted from the halogen lamp of the illuminator is irradiated with a white paper placed at a distance of 10 cm from the diffraction grating, and the color in the range of ± 5 ° is observed from the brightest place. When a rainbow appears, white light appears to be separated into green, red, and blue due to the angular dispersion of the light. The medium 2 is a diffraction grating, the shape of the grating is an isosceles triangle, and the thickness of the substrate is 2 mm. The medium 1 is air.

  When the incident light was diffused light, a diffuser was inserted as close to the diffraction grating as possible, and ground glass from Edmund Optics was used as the diffuser. The change in coloring caused by diffraction gratings with different periods was visually examined. The results are summarized in Table 2 in FIG. The aspect ratio of the grating is 0.7 when the period is 10 μm and 0.48 otherwise.

  Regarding Case A and Case B, the case where the incident light was parallel / diffused, reflected / transmitted, perpendicularly incident / obliquely incident at 45 ° was examined. In normal incidence, light was incident perpendicular to the surface of the diffraction grating. The case where the diffuser was not put in the optical path was defined as “parallel”. When the period is 3 μm, the diffracted light is white only with respect to the diffused light. For example, the diffused light can be used for preventing the diffused light from being reflected, but it cannot be used for a general display. On the other hand, it can be seen that it can be used for most purposes with a period of 5 μm or more. In the experiment, when the aspect ratio is 1 or less, the wavelength dependence of the reflectance is small when Λ / λ is in the vicinity of 9, so the calculation results of FIGS.

  FIG. 30 shows a reflectance measurement method when the interface is the uneven surface of the medium 2 and its back surface. Media 1 and 3 are air. The calculation of the reflectance is the same as when there is no back surface. The lattice is an isosceles triangle, the aspect ratio is 0.48, and the period and the substrate thickness are different. It is a striped diffraction grating made of UV-cured acrylic resin and has a refractive index of 1.52. Light enters the irregularities on the surface of the medium 2 from the air of the medium 1.

  A strong light of 632.8 nm is made incident by a He-Ne laser. As a result of measuring the ratio of the TE mode to the TM mode with respect to the total reflectance excluding regular reflection, it was as shown in Table 3 of FIG. The results agree well with the calculation results, and in both cases, the TE mode has a reflectance approximately twice as large as that of the TM mode. Therefore, this unevenness can be used when only TM mode transmitted light is required.

  This ratio can be increased by increasing the aspect ratio, and the ratio can be increased to about 10 when the aspect ratio is 2. The film thickness was measured with a confocal microscope, and the film thickness with which the TE / TM ratio matched well between the experiment and the calculation was searched for within the measured value ± 0.1 μm. The calculated TE / TM total reflectance was calculated by averaging three points including two points of ± 0.05 μm in consideration of variations in film thickness. The film thickness was as shown in Table 4 of FIG.

(Examination of the effect of refractive index by RCWA)
By changing the refractive index, the total reflectance at the interface between the medium 1 and the medium 2 under different conditions such as the incident direction, shape, incident angle range, and polarized light was examined, and the influence of the refractive index was verified. FIG. 33 shows the Case A having a rectangular lattice shape.

  Table 5 in FIG. 34 shows the result of calculation under the condition of only the interface between the medium 1 and the medium 2 where the medium 1 is a grating having a refractive index of 1 and the medium 2 is a grating having a refractive index of 1.5 or 3. Saw teeth and rectangles having the same depth d / period Λ were studied. Even if the refractive index changes, it can be seen that, for both Case A and B, the sawtooth for parallel light has a smaller total reflectance than the rectangular shape. As for diffused light, in Case A, the sawtooth has a smaller total reflectance than the rectangle.

(Production)
Next, a method for creating an antireflection structure will be described below. This production method comprises a series of steps of producing a diffraction grating mold, transferring it to the UV curable resin 150, curing it, and attaching it to the front panel of the display. Hereinafter, each step will be described in more detail.

  (1) The mold is produced as follows. When creating by machining, for example, FANUC, TOSHIBA MACHINE, Nagase Integrex ultra-precision fine grooving machine can be used. The diamond tool used for machining is appropriately processed according to the groove shape. More specifically, for example, it can be processed as follows.

  The apparatus uses a Nagase Integrex NIC-200 having a non-contact hydrostatic bearing. The temperature is 23 ± 0.1 ° C. and the humidity is 40 ± 10%. The material of the mold is copper or Ni-P. Copper is plated with a thickness of around 0.5 microns to prevent corrosion after cutting.

  (2) Transfer is performed as follows. Unevenness is transferred from the mold using the UV curable resin 150. The UV curable resin 150 is preferably 10 μm thick after curing and a haze of 1% or less. For example, Sanyo Kasei Sun-Rad or Hitachi Chemical Kogyo Hitachiroid can be used. Use a solvent-free type that cures one part. Furthermore, when heat resistance of the resin is required, FX-V550, which is a silicone insulating transparent coating material manufactured by Asahi Denka, may be used.

  (3) UV curing is performed using an ultraviolet exposure device, and the exposure device can be a Harrison Toshiba writing ultraviolet exposure device or a Dainippon Screen mask aligner. The light source is a high-pressure mercury lamp. As shown in FIGS. 11 and 12, as the base film 160 on which the ultraviolet curable resin 150 is placed, Teijin DuPont film FT3 or Toyobo PET film A4300 can be used.

  (4) In UV curing, after a resin is put into a mold, a base film is placed, the surface of the film is rubbed, and exposure by ultraviolet irradiation is performed. In the case of a resin having oxygen inhibition, exposure is performed in a nitrogen stream. More specifically, for example, the following is performed. The apparatus uses a mask aligner M-2L manufactured by Mikasa Corporation. The lamp current of the ultra-high pressure mercury lamp is 6.3 A, and the lamp voltage is 40V. The exposure time is 35 seconds.

  (5) The uneven shape is measured as follows. A section of the transferred film is cut out using a focused ion beam in addition to a cutter and scissors. The film may be solidified with liquid nitrogen, and the cross section cut out with a cutter.

  (6) Next, the depth and shape of this cross section are measured with a scanning electron microscope (SEM). Technique. ”, Optical Review, Volume 9, Issue 5, 2002, p.183-p.185). As SEM, Hitachi scanning electron microscope S-3600N and TINY-SEM manufactured by Technex Co. Ltd can be used.

  (7) On the other hand, AFM (Atomic Force Microscopy) is used to measure the period and surface roughness. AFM can use Nanopics from Seico Instruments. When measuring the surface roughness, the measurement length is 3 to 4 times the average period. In the case of a striped diffraction grating, the average period is determined in the direction perpendicular to the stripe. On the other hand, the surface roughness is determined in a direction parallel to the stripes. Roughness is measured parallel to the groove at the middle of the mountain and valley. In the case of a grid-like diffraction grating, the value of the period is determined so that the average period becomes the shortest.

  (8) The surface roughness is measured in a direction perpendicular to the direction in which the average period is the shortest. The cut-off value is half of the average period, and the measured total length is 3 to 4 times the average period. The surface roughness used here is the centerline average surface roughness. The definition here is based on Japanese Industrial Standard JIS except for the measurement length and the cutoff value.

  (9) As shown in FIG. 12, when using the antireflection structure, a transparent adhesive film or adhesive 170 is used to attach the light emitting surfaces of the base film 160 and the light emitting diode 190. The pressure-sensitive adhesive film preferably has a thickness of 1 μm and a haze of 1% or less. The refractive index is preferably about the average of the base film 160 and the light emitting surface in order to reduce the reflectance.

  For example, a transparent double-sided adhesive tape made by Lintec or an adhesive film for optical function sheets made by Hitachi Chemical Co., Ltd. can be used. If heat resistance is required, Sumitomo 3M acrylic adhesive Y-9479 and Toray Dow Corning addition reaction type silicone adhesive SD4592 can be used. These are affixed using a roll laminator or a rubber roller so that bubbles do not enter.

  If the final use form is a fine element, it is further cut out using a dicer.

(Comparison with comparative example)
The uneven surface 60 obtained by the above manufacturing process diffuses light, has a low reflectance, does not visually recognize a rainbow even when exposed to white light, and causes moiré due to interference with a pixel such as a color filter matrix. Absent. In comparison, the characteristics of conventional diffraction gratings and diffusers are as follows.

(1) A periodic diffraction grating having a groove width of 1/2 or less of the wavelength does not diffuse light.
(2) The hologram diffuser has a light reflectance of 2% or more at the interface.
(3) A prism sheet having a periodic grating groove having a period of 60λ or more interferes with the color filter of the pixel to generate moire.

  On the other hand, as can be seen from Table 2, there is no rainbow at a period of 1.8 or more. Further, as can be seen from the measurement result of FIG. 30, a total reflectance of 0.4% and a reflectance sufficient for preventing reflection can be obtained. In addition, moire does not occur due to interference with the color filter of the liquid crystal display.

  The best mode for carrying out the present invention has been described based on the embodiment and the examples. However, the present invention is not limited to such an embodiment and examples, and Needless to say, there are various embodiments within the scope of the technical matters described in (1).

  The antireflection structure according to the present invention having the above configuration can be applied in a wide range of fields such as various flat displays, solar cell panels, and light emitting elements. In particular, it is useful as a large-area or inexpensive antireflection structure. By applying the antireflection structure according to any one of claims 1 to 5 to an emission surface of an organic or inorganic light emitting element via an adhesive or an adhesive film, it can be applied as a light emitting element with reduced interface reflectance.

It is a figure explaining the principle of this invention, and is a figure which prescribes | regulates the vertex of each unevenness | corrugation in the case where two different unevenness | corrugations are made into 1 period. It is a figure which shows how to draw the auxiliary line for determining the average groove width and average depth d of an unevenness | corrugation. It is a figure explaining Embodiment 1, and is a figure which shows the unevenness | corrugation which changes a refractive index discontinuously in the depth direction. It is a figure explaining Embodiment 1, and is a figure which shows the position of the width direction of the trough bottom of a groove | channel. It is a figure explaining Embodiment 3, and is a figure which shows an incident angle, a reflection angle, and a transmission diffraction angle. It is a figure which shows the diffraction order of a transmission diffraction angle. Is a view for explaining the third and fourth embodiments, the period is lambda, substrate thickness groove depth in d _g is a sectional view showing a lattice film of d _s. It is a figure explaining Embodiment 3, and is a figure which shows the electric field strength distribution of the scattered light of the grating | lattice film of the same base, but different groove | channel thickness. It is a figure explaining Embodiment 4, and is a figure which shows the shape of a groove | channel. It is a figure explaining Embodiment 4, and is a figure which shows the shape of a groove | channel. It is a figure explaining Embodiment 6, and is a figure which shows the unevenness | corrugation stuck on the display front panel. It is a figure explaining Embodiment 7, and is a figure which shows the unevenness | corrugation stuck on the light emitting element surface. It is a figure explaining the Example of this invention, and is a figure which shows the periodicity of the reflectance with respect to each d / (LAMBDA) when light advances from the medium of refractive index 1 to the medium of 1.5. It is a figure explaining the Example of this invention, and is a figure which shows the periodicity of the reflectance with respect to each d / (LAMBDA) as light advances from the medium of refractive index 1.5 to 1 medium. It is a figure explaining the Example of this invention, and is Table 1 which shows the value of the standard deviation / average about each d / (LAMBDA) when the range of (LAMBDA) / (lambda) is 4.5-9. It is a figure explaining the Example of this invention, and is sectional drawing which shows the grating | lattice of the similar shape from which a period is (LAMBDA) and groove width differs. It is a figure explaining the Example of this invention, and is a figure which shows the comparison of the diffraction angle distribution of the diffraction grating which makes the same triangle 1 period, and the diffraction grating which makes 2 types of different triangles 1 period. It is a figure explaining the Example of this invention, and is sectional drawing which shows the grating | lattice of the unequal triangular triangle symmetrical in one period. It is a figure explaining the Example of this invention, and is a figure which shows the comparison of the diffraction angle distribution of the diffraction grating of an isosceles triangle and an unequal triangle. FIG. 4 is a diagram illustrating an embodiment of the present invention, and is a cross-sectional view illustrating a diffraction grating with a back surface of a medium 2 and layers of the media 3 and 4. It is a figure explaining the Example of this invention, and is a figure which shows the total reflectance when changing the refractive index of the medium 3 which touches the back surface of the unevenness | corrugation of the medium. It is a figure explaining the Example of this invention, and is sectional drawing which shows the relationship between the incident angle to a groove | channel and a slope. It is a figure explaining the Example of this invention, and is a figure which shows the reflectance change when an aspect ratio is changed. It is a figure explaining the Example of this invention, and the shape of a tip It is a figure explaining the Example of this invention, and the result of having calculated the reflectance about three conditions of a constriction It is a figure explaining the Example of this invention, and is a figure which shows the unevenness | corrugation which makes a similar triangle one period. It is a figure explaining the Example of this invention, and is a figure which shows the measuring method of a total reflectance in case an interface is only an uneven surface. It is a figure explaining the Example of this invention, and is a figure which shows the coloring and the rainbow measuring method by diffraction. It is a figure explaining the Example of this invention, and is Table 2 which shows the change of coloring by the diffraction grating from which a period differs. It is a figure explaining the Example of this invention, and is a figure which shows the measuring method of a reflectance in case an interface is the uneven | corrugated surface of the medium 2, and its back surface. It is a figure explaining the Example of this invention, and is Table 3 which shows the result of having measured the ratio of TE mode and TM mode about the total reflectance except regular reflection. It is a figure explaining the Example of this invention, and is Table 4 which shows the measurement and calculation result of thickness ds of a base material. It is sectional drawing of a rectangular lattice shape. 6 is a table 5 showing total reflectance at the interface between the medium 1 and the medium 2 under different conditions such as an incident direction, a shape, a refractive index, an incident angle range, and polarized light.

Explanation of symbols

10 outermost surface average value 20 outermost surface average value -λ × 1.5
30 Line of depth 1/2 40 Line of valley bottom 50 Circle indicating valley bottom 60 Concavity and convexity at interface between media 1 and 2 61 m Triangular symmetrical triangle 60 Convex and concave interface 70 Groove width 80 Discontinuous refractive index Change 90 Incident light 100 Reflected light 110 Transmitted diffracted light 120 Vertical incident light 130 Line connecting uneven peaks and valleys 140 1/2 line 150 Medium 2 UV curable resin 160 Medium 3 base film (PET film, etc.)
170 Adhesive film or adhesive of medium 4 180 Display panel of medium 5 190 Light emitting element 200 Medium 2 of diffraction grating film
210 Medium 3 with variable refractive index
215 Diffraction grating with zero substrate thickness 220 Dove prism 230 UV curable resin 240 Reflected light 250 Transmitted light 260 Illuminator 270 Flexible light guide 280 Iris stop 290 Lens 1
300 Lens 2
310 diffuser 320 diffraction grating 330 light spot 340 white paper 350 rectangular grating medium 2
θi Incident angle θr Reflection angle θt Transmission diffraction angle

Claims (12)

When light is incident on the interface between the uneven medium 1 and the medium 2, the average groove width of the unevenness is Λ, the average depth is d, the wavelength in the medium 1 is λ1, and the wavelength in the medium 2 is λ2. , Having an average groove width Λ and an average depth d satisfying the conditions of the following formulas (1) and (2), and continuously changing the average refractive index in the depth direction, the total reflectance at the interface is An antireflection structure corresponding to a plurality of wavelengths characterized by being reduced.
(1) 0.45 × Λ <d
(2) 4 <Λ / λ1 <120
However, λ1> λ2 When light is incident on the interface between the transparent medium 1 having the irregularities and the transparent medium 2, the average groove width of the irregularities is Λ, the average depth is d, the wavelength in the medium 1 is λ1, and the wavelength in the medium 2 is The wavelength is λ2, the average groove width Λ and the average depth d satisfying the conditions of the following expressions (3) and (4), the apex angle of the convex portion of the medium 2 is 96 ° or less, and in the depth direction When the average refractive index of the medium 3 continuously changes and reflection of light entering the medium 2 from the medium 1 is prevented, the refractive index of the medium 3 in contact with the surface of the medium 2 opposite to the interface is 0. 2. An antireflection structure for white light using only one of polarized light that is different by 2 or less or is orthogonal.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2 When light is incident on the interface between the transparent medium 1 having the irregularities and the transparent medium 2, the average groove width of the irregularities is Λ, the average depth is d, the wavelength in the medium 1 is λ1, and the wavelength in the medium 2 is The wavelength is λ2, the average groove width Λ and the average depth d satisfy the conditions of the following formulas (3) and (4), the apex angle of the convex portion of the medium 2 is 96 ° or less, and the medium 2 to the medium 1 In order to prevent reflection of light incident on the medium, the medium 2 itself is a light emitter, or the refractive index of the medium from the medium 2 to the light source is higher or equal to that of the medium 2, and is reflected for white light Prevention structure.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2 Over 80% of the uneven groove width is within Λ ± 4%, and the total reflectance at the interface is reduced by having the groove width and depth satisfying the conditions of the following formulas (5) and (6). The antireflection structure according to claim 1, 2, or 3.
(5) 0.45 × Λ <d
(6) 8 <Λ / λ1 <40   80% or more of the uneven groove width falls within the range of average groove width × {1 ± λ1 / Λ}, and more than 50% of the groove width is average groove width × {1 ± λ1 / (5 · Λ)}. The antireflection structure according to claim 1, 2 or 3, wherein the antireflection structure does not fall within the range. When light is incident on the interface between the uneven medium 1 and the medium 2, the average groove width of the unevenness is Λ, the average depth is d, the wavelength in the medium 1 is λ1, and the wavelength in the medium 2 is λ2. The average groove width Λ and the average depth d satisfying the conditions of the following formulas (3) and (4), the apex angle of the convex portion of the medium 2 is 96 ° or less, and the cross-sectional shape is the convex portion of the medium 2 Anti-reflection structure for white light, which is a triangle with a tapered tip toward the tip of the light source, and the total refractive index at the interface is reduced by continuously changing the average refractive index in the depth direction .
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2   The antireflection structure according to any one of claims 1 to 5, wherein a ratio of an outermost surface of the unevenness of the interface or a flat portion of the valley bottom is 5% or less. When light is incident on the interface between the medium 1 and the medium 2 having periodic irregularities, the average groove width of the irregularities is Λ, the average depth is d, the wavelength in the medium 1 is λ1, and the wavelength in the medium 2 Is λ2, the average groove width Λ and the average depth d satisfying the conditions of the following expressions (3) and (4), the apex angle of the groove is 96 ° or less, and the average refractive index in the depth direction is For variables a, b, and c that reduce the total reflectivity at the interface by continuously changing, and define the uneven shape in which both ends of one cycle of the unevenness are substantially asymmetric triangles on the left and right, Is the base of the left triangle, b is the base of the right triangle, and c is the distance between the peaks when the triangles at both ends are translated, the following equations (7) and (8) An antireflection structure for white light that includes satisfactory interface irregularities at both ends of one cycle.
(3) 0.45 × Λ <d
(4) 3 <Λ / λ1 <120
However, λ1> λ2
(7) 0.8 <a / b <1.2
(8) c / (a + b)> 1.2 or c / (a + b) <0.8   The antireflection structure according to any one of claims 1 to 8, wherein the uneven slope of the interface has an average roughness Ra of λ or less.   The surface of the medium 2 opposite to the uneven surface of the interface is used by being attached to the surface on the viewer side of the front panel of the display via an adhesive or adhesive, and the thickness of the adhesive or adhesive is used. The antireflection structure according to claim 1, wherein a difference in refractive index between the opposite surface and the adhesive or adhesive is 0.2 or less. With display.   The surface opposite to the uneven surface of the interface is used by being attached to the emission surface of the organic or inorganic light emitting element via an adhesive or an adhesive, and the thickness of the adhesive or adhesive is 20λ1 or less. The reflection according to any one of claims 1 to 8, wherein a difference in refractive index between the uneven surface of the interface and the surface on the opposite side is 0.01 or more and 0.6 or less. Light-emitting element with a prevention structure.   In the medium 2, the average in a cross section having a value obtained by subtracting the average depth d from the distance between the surface having the irregularities at the interface with the medium 1 and the surface on the opposite side is 4λ1 to 100λ1, The refractive index of the medium 3 contacting the medium 2 on the surface opposite to the uneven surface of the interface with the medium 1 is different by 0.1 or more. Anti-reflection structure.

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