JP2014010217A - Antireflective laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an antireflection performance even when an incident angle of light is large.SOLUTION: An antireflection laminate relating to the present invention includes, from a substrate side, a plurality of thin film layers and a rugged part. In the antireflection laminate, the refractive index of at least one thin film layer is higher than the refractive index of the substrate; and the rugged part has an average pitch smaller than a wavelength of light as a target for use, in which the most recessed part reaches the thin film layers.

Description

  The present invention relates to an antireflection laminate that is provided on the surface of a base material in order to suppress reflection of incident light, and particularly relates to an antireflection laminate that includes a plurality of thin film layers and uneven portions. Is.

  2. Description of the Related Art Conventionally, an antireflection structure has been employed to prevent ambient ambient light and the like from being reflected in a display or the like, or to prevent stray light in an optical element such as a camera lens. As such an antireflection structure, a moth-eye structure in which fine irregularities are periodically provided is known.

  As an antireflection structure having such a moth-eye structure, Patent Document 1 discloses an antireflection structure by disposing a low refractive index layer having a lower refractive index than the base material between the base material and the antireflection layer. An antireflective structure that improves the degree of freedom of material selection that can be used for the periodic structure layer within the layer is disclosed. Patent Document 2 discloses an antireflection article in which a first layer having a fine concavo-convex structure is provided on one surface of a transparent substrate via one or more intermediate layers. In this antireflection article, the refractive index difference between all adjacent layers is set to 0.01 or more and 0.11 or less, and the refractive index ns of the transparent substrate and the refractive index n1 of the first layer are set to predetermined values. By providing the difference, the reflectance is reduced.

International Publication No. 2008/102882 JP 2009-31764 A

  An object of the present invention is to provide an antireflection laminate in which antireflection performance is improved in an antireflection structure having an uneven portion (moth eye structure) provided periodically.

Therefore, the antireflection laminate according to the present invention is
In the antireflection laminate provided on the incident light side of the substrate,
In order from the base material side, it has a plurality of thin film layers and uneven portions,
The refractive index of at least one of the thin film layers is higher than the refractive index of the substrate,
The average pitch of the concave and convex portions is equal to or less than the wavelength of light to be used, and the most concave portion reaches the thin film layer.

Furthermore, in the antireflection laminate according to the present invention,
The cross-sectional shape of the uneven portion with respect to the incident direction of incident light is a trapezoid.

Furthermore, in the antireflection laminate according to the present invention,
The shape of the concavo-convex part is characterized in that the upper base is 0.1 P or less and the lower base is 0.9 P or more with respect to the average pitch P of the concavo-convex part.

Furthermore, in the antireflection laminate according to the present invention,
The thin film layer located closest to the substrate has a refractive index higher than that of the substrate.

Furthermore, in the antireflection laminate according to the present invention,
The plurality of thin film layers have a refractive index that increases as they are positioned on the substrate side.

Furthermore, in the antireflection laminate according to the present invention,
The uneven portion is provided with a coating layer covering the uneven portion.

  In the present invention, the refractive index of at least one thin film layer is set to be higher than the refractive index of the base material, the average pitch of the concavo-convex portions is equal to or less than the wavelength of light to be used, and the most concave portion By adopting the configuration reaching the thin film layer, it is possible to improve the antireflection performance, particularly when the incident angle is increased.

The schematic diagram which shows the mode of arrangement | positioning of the reflection preventing laminated body which concerns on embodiment of this invention. The schematic diagram (Example 1) which shows the detail (side cross section) of the reflection preventing laminated body which concerns on embodiment of this invention. The schematic diagram which shows the detail (side cross section) of the reflection preventing laminated body which concerns on embodiment of this invention (modified example of Example 1) The schematic diagram which shows the detail (upper surface) of the antireflection laminated body which concerns on embodiment of this invention Schematic diagram showing a conventional antireflection structure (side cross section) (Comparative Example 1) Schematic diagram showing antireflection structure (side cross section) (Comparative Example 2) The schematic diagram (Example 2) which shows the detail (side cross section) of the reflection preventing laminated body which concerns on embodiment of this invention. The figure which shows the reflective 0th-order diffraction efficiency of Example 1 The figure which shows the reflective 0th-order diffraction efficiency of Example 2 Schematic diagram showing details (side cross-section) of an antireflection laminate according to an embodiment of the present invention (Example 3)

  Now, the antireflection laminate according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a state of arrangement of the antireflection laminate 2 according to the embodiment of the present invention. FIG. 1 shows a cross-sectional state of the antireflection laminate 2 provided on the substrate 1. The antireflection laminate 2 of the present embodiment includes a display surface of a display device such as a display, a surface of various optical elements such as a lens, or a surface of a solar cell material such as silicon (Si) constituting the solar cell, It is disposed on the surface of the substrate 1 that needs to prevent reflection of incident light. Here, the incident angle α with respect to the antireflection laminate 2 is defined as an angle formed with a perpendicular to the surface of the antireflection laminate 2.

  In recent years, for example, displays and the like have a high-performance antireflection performance in which the incident angle α is within ± 40 ° (within + 40 ° when considering symmetry) and the reflectance is 0.1% or less over the entire visible wavelength range. It has been demanded. In particular, it is required to improve the antireflection performance for incident light from an oblique direction with a large incident angle α. In the present embodiment, in view of such a situation, even when the incident angle of incident light with respect to the antireflection laminate 2 is increased, the reflectance is suppressed and the antireflection performance is improved.

Example 1
FIG. 2 is a schematic diagram showing details (side cross-section) of the antireflection laminate according to the embodiment of the present invention. FIG. 2 is a schematic diagram in which the vicinity of the surface of FIG. 1 is enlarged and displayed. The antireflection laminate 2 includes a second thin film layer 23, a first thin film layer 22, and an uneven portion 21 in order from the base material 1 side. The base material 1, the first thin film layer 22, the second thin film layer 23, and the concavo-convex portion 21 are all made of a material having transparency at the wavelength of light to be used. In this embodiment, it has transparency in visible light.

A transparent material having a refractive index of 1.5 is used for the substrate 1. A plurality of thin film layers are provided on the surface of the substrate 1. In the present embodiment, the first thin film layer 22 and the second thin film layer 23 are constituted by two thin film layers. In the present embodiment, silicon oxide (SiO ₂ ) is used for the first thin film layer 22, and titanium oxide (TiO ₂ ) is used for the second thin film layer 23. In the present embodiment, the film thickness of the first thin film layer 22 is 0.060 μm, and the film thickness of the second thin film layer 23 is 0.002 μm.

  In order to improve the antireflection performance, any one of the plurality of thin film layers 22 and 23 is set to have a higher refractive index than the refractive index of the substrate 1. In the present embodiment, in particular, the second thin film layer 23 is in contact with the base material 1 so that the refractive index of the second thin film layer 23 is higher than the refractive index of the base material 1 at the wavelength of light to be used. Material is selected. Furthermore, it is preferable that the refractive indexes in the plurality of thin film layers 22 and 23 are set to be higher as they are located on the substrate 1 side.

  The concavo-convex portion 21 of the present embodiment provided on the surface of the first thin film layer 22 has a two-dimensional periodic structure, and one concavo-convex portion 11 has a quadrangular pyramid shape with a vertex portion cut off. Yes (moth eye structure). Therefore, as shown in FIG. 2, the cross section of the concavo-convex portion 21 in the incident direction of incident light has a trapezoidal shape. It should be noted that the valley portion 21 b corresponding to the most recessed portion of the uneven portion 21 needs to reach the first thin film layer 22. The uneven portion 21 is formed by, for example, forming a flat layer with a photocurable resin and curing the photocurable resin by irradiating UV light in a state where the mold of the uneven portion 21 is pressed thereon (in). Printing) and the like. At that time, in order to reach the valley portion 21b to the first thin film layer 22, after imprinting, the valley portion 21b of the uneven portion 21 may be cut by etching or the like. Although the cross section of the concavo-convex portion 21 is trapezoidal, the width of the trapezoidal top portion 21a may be 0, that is, a triangular shape.

  Adjacent irregularities 21 are arranged with a pitch P to form a periodic structure. The pitch P is set to be equal to or less than the wavelength of light to be used (visible light in the present embodiment). In the present embodiment, the pitch P is constant, but the pitch P may be random. In that case, the average pitch is set to be equal to or less than the wavelength of light to be used. 4 shows a top view of the antireflection laminate 2 in FIG. The side cross section shown in FIG. 2 is exactly the state when cut along AA including the top 21a of FIG. Even when cut between BB in FIG. 4, a side cross section similar to that in FIG. 2 appears. In the present embodiment, the pitch P of the uneven portions 21 is 0.18 μm, and the height H of the uneven portions 21 is 0.45 μm. Further, a transparent material having a refractive index of 1.5 is used for the uneven portion 21.

In the embodiment of FIG. 2, the shape of the uneven portion 21 is equal to the pitch P and the length of the lower base B of the uneven portion 21, but the shape of the uneven portion 21 can be freely changed within the range described below. Is possible. The length T of the upper base of the concavo-convex portion 21 is preferably set to be 0.1 times or less with respect to the pitch P, that is, T ≦ 0.1P. In addition, the length B of the bottom of the concavo-convex portion 21 is preferably set to be 0.9 times or more with respect to the pitch P, that is, B ≧ 0.9P. FIG. 3 schematically shows the cross-sectional shape of the embodiment in which the bottom of the uneven portion 21 is made smaller than the pitch P. When the lower bottom P has a length smaller than the pitch P, the first thin film layer 22 is partially exposed in the valley portion 21b.

  Comparative examples for comparing the reflection efficiency of the antireflection laminate of this embodiment are shown in FIGS. In any of the comparative examples, the transparent material having the same refractive index of 1.5 as that of Example 1 is used for the substrate 1.

The comparative example 1 shown in FIG. 5 is configured to have an antireflection structure 3 composed only of the concavo-convex portions 31 on the base material 1. The uneven portion 31 in the comparative example 1 has the same configuration as that of the first embodiment shown in FIG. 2 (the pitch P of the uneven portion 31 is 0.18 μm and the height H of the uneven portion 31 is 0.45 μm). Further, a transparent material having a refractive index of 1.5 is used for the uneven portion 21. On the other hand, Comparative Example 2 in FIG. 6 is a case where the antireflection structure 3 is formed by the thin film layer 32 composed of one layer and the uneven portion 31. Also in the comparative example 2, the uneven portion 31 has the same configuration as that of the first embodiment (the pitch P of the uneven portion 31 is 0.18 μm, and the height H of the uneven portion 31 is 0.45 μm). The thin film layer 32 is made of silicon oxide (SiO ₂ ) having a thickness of 0.013 μm.

  Table 1 shows the results of the antireflection performance of Example 1 and Comparative Examples 1 and 2. Here, the average reflection zero-order diffraction efficiency (unit:%) at each incident angle when random polarized light having a wavelength of 0.4 to 0.7 μm is used as incident light is shown. The reflection zero-order diffraction efficiency is 0.1% or less at any incident angle in Comparative Examples 1 and 2, but Example 1 has a reflection zero-order diffraction efficiency higher than that of Comparative Examples 1 and 2. It can be seen that the anti-reflection performance is improved.

  FIG. 8 is a graph showing the reflection zero-order diffraction efficiency in Example 1. As can be seen from this graph, when the incident angle is 40 ° or less, the reflection zero-order diffraction efficiency is suppressed to 0.1 [%] or less at any wavelength, and the antireflection performance is improved.

(Example 2)
The schematic diagram which shows the detail (side cross section) of the reflection preventing laminated body which concerns on embodiment of this invention is shown by FIG. In Example 1, two thin film layers including the first thin film layer 22 and the second thin film layer 23 are provided between the base material 1 and the uneven portion 21, but the number of these thin film layers is further increased. It's also good. In the second embodiment, by providing the first thin film layer 22, the second thin film layer 23, the third thin film layer 24, and the three thin film layers, the antireflection performance is further improved as compared with the first embodiment. . The thin film layer may be three or more layers.

In the present embodiment, magnesium fluoride (MgF ₂ ) is used for the first thin film layer 22, and the film thickness is 0.016 μm. Silicon oxide (SiO ₂ ) is used for the second thin film layer 23, and the film thickness is 0.005 μm. Further, a UV curable resin (trade name: PAK-01) having a film thickness of 0.013 μm is used for the third thin film layer 24. Moreover, the uneven | corrugated | grooved part 21 of this embodiment is the same structure as Example 1 (The pitch P of the uneven | corrugated | grooved part 21 is set to 0.0.
18 μm, the height H of the concavo-convex portion 21 is 0.45 μm, and the refractive index is 1.5).

  Also in Example 2, the refractive index of any one of the plurality of thin film layers 22, 23, 24 is required to be higher than the refractive index of the substrate 1. In Example 2, the material of the third thin film layer 24 is made so that the refractive index of the third thin film layer 24 in contact with the base material 1 is higher than the refractive index of the base material 1 at the wavelength of light to be used. Selected. Furthermore, it is preferable to set the refractive indexes of the plurality of thin film layers 22, 23, and 24 so as to increase as they are positioned on the substrate 1 side.

  Table 1 shows the results of the antireflection performance of Example 2. Here, the average reflection zero-order diffraction efficiency (unit:%) at each incident angle when random polarized light having a wavelength of 0.4 to 0.7 μm is used as incident light is shown. In Example 1, the reflected 0th-order diffraction efficiency was suppressed more than in Comparative Examples 1 and 2, but in Example 2, the reflected 0th-order diffraction efficiency was further suppressed as compared with Example 1. It can be seen that the antireflection performance is improved.

  FIG. 9 is a graph showing the reflection zero-order diffraction efficiency in Example 2. As in Example 1, when the incident angle is 40 ° or less, the reflection zero-order diffraction efficiency is suppressed to 0.1 [%] or less at any wavelength. Further, it can be seen that, compared with the graph of Example 1 shown in FIG. 8, the reflection zero-order diffraction efficiency is improved particularly at a wavelength of 0.50 μm or more and an incident angle of 40 ° or less.

(Example 3)
The schematic diagram which shows the detail (side cross section) of the reflection preventing laminated body which concerns on embodiment of this invention is shown by FIG. In this embodiment, the coating layer 25 is provided on the surface of the concavo-convex portion 21 of Example 1 described in FIG. In this case, the refractive index of the covering layer 25 is preferably set to be smaller than the refractive index of the uneven portion 21.

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Antireflection laminated body, 21 ... Uneven part, 21a ... Top part, 21b ... Valley part, 22 ... 1st thin film layer, 23 ... 2nd thin film layer, 24 ... 3rd thin film layer, 25 ... Coating Layer 3, antireflection structure 31, uneven portion 32, thin film layer

Claims (6)

In the antireflection laminate provided on the incident light side of the substrate,
In order from the base material side, it has a plurality of thin film layers and uneven portions,
The refractive index of at least one of the thin film layers is higher than the refractive index of the substrate,
The average pitch of the concavo-convex portions is equal to or less than the wavelength of light to be used, and the most recessed portion reaches the thin film layer. The antireflection laminate according to claim 1, wherein a cross-sectional shape of the concavo-convex portion in the incident direction of incident light is a trapezoid. The antireflection laminate according to claim 2, wherein the shape of the concavo-convex portion is 0.1 P or less in the upper base and 0.9 P or more in the lower base with respect to the average pitch P of the concavo-convex portions. . The antireflection laminate according to any one of claims 1 to 3, wherein a refractive index of a thin film layer positioned closest to the substrate side is higher than a refractive index of the substrate. The antireflection laminate according to any one of claims 1 to 4, wherein the plurality of thin film layers have a higher refractive index as they are positioned on the substrate side. The antireflection laminate according to any one of claims 1 to 5, wherein the uneven portion is provided with a coating layer that covers the uneven portion.

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