WO2015145829A1

WO2015145829A1 - Antireflective article, image display device, mold for manufacturing antireflective article, and method for manufacturing mold for manufacturing antireflective article

Info

Publication number: WO2015145829A1
Application number: PCT/JP2014/076463
Authority: WO
Inventors: 祐一宮崎; 増淵　暢; 松藤　和夫; ゆり下嵜; 洋一郎大橋
Original assignee: 大日本印刷株式会社
Priority date: 2014-03-28
Filing date: 2014-10-02
Publication date: 2015-10-01
Also published as: JP5644974B2; JP2014209232A

Abstract

The purpose of this invention is to improve, relative to existing antireflective articles, the abrasion resistance and antireflective functionality of an antireflective article that has a moth-eye structure. Said antireflective article, in which tiny protrusions are densely arrayed and the spacing between adjacent tiny protrusions is less than or equal to the shortest wavelength in the wavelength band of electromagnetic waves to prevent the reflection of, is characterized in that: said tiny protrusions comprise multi-peak tiny protrusions that each have a plurality of apices and single-peak tiny protrusions that each have a single apex; and letting m represent the mean height (H) of the frequency distribution of the heights (H) of the tiny protrusions and letting σ represent the standard deviation of said frequency distribution, the ratio (Nm/Nt) of the number (Nm) of multi-peak tiny protrusions in a given region, namely a low-height region, i.e. the region in which H < m−σ, a medium-height region, i.e. the region in which m−σ ≤ H ≤ m+σ, or a high-height region, i.e. the region in which m+σ < H, to the total number (Nt) of tiny protrusions in the entire frequency distribution is higher for the medium-height region than for either the low-height region or the high-height region.

Description

Antireflection article, image display device, antireflection article manufacturing mold, and antireflection article manufacturing mold manufacturing method

The present invention relates to an antireflection article for preventing reflection by closely arranging a large number of minute protrusions at an interval equal to or shorter than the shortest wavelength of an electromagnetic wave wavelength band for preventing reflection.

In recent years, regarding an antireflection film, which is a film-shaped antireflection article, there has been proposed a method for preventing reflection by arranging a large number of microprotrusions closely on the surface of a transparent substrate (transparent film) (patent) Reference 1 to 3). This method uses the principle of the so-called moth-eye structure, and continuously changes the refractive index for incident light in the thickness direction of the substrate, thereby discontinuous interface of the refractive index. Is eliminated to prevent reflection.

In the antireflection article according to this moth-eye structure, the microprojections are closely arranged so that the interval d between adjacent microprojections is equal to or less than the shortest wavelength Λmin (d ≦ Λmin) of the wavelength band of the electromagnetic wave to prevent reflection. . Moreover, each microprotrusion is produced so that a cross-sectional area may become small gradually toward the front end side from a transparent base material so that it may be planted on a transparent base material.

Various uses have been proposed for such antireflection articles. For example, it can be placed on the light exit surface of various image display devices to reduce external light reflection such as sunlight on the screen to improve image visibility, or to form the microprojections on a sheet or plate-like transparent substrate Furthermore, by constructing a touch panel using an electrode in which a transparent conductive film such as ITO (indium tin oxide) is formed on the microprojection group, light reflection between the touch panel electrode and various adjacent members is performed. It has been proposed to reduce the occurrence of interference fringes, ghost images, and the like.

Further, Patent Document 4 discloses a sufficient antireflection function for this type of antireflection article, even when a plurality of vertices are created at the tops of the microprojections due to poor filling of the resin during the molding process. It is described that it can be secured.

By the way, the antireflection article according to this kind of moth-eye structure has a problem that the scratch resistance is still insufficient in practice. That is, for example, when an anti-reflective article comes into contact with another object, the anti-reflective function is locally deteriorated, and white turbidity, scratches, etc. occur at the contact location, resulting in poor appearance.
Further, such an antireflection article is required to further improve the antireflection function.

Japanese Patent Laid-Open No. 50-70040 Special Table 2003-531962 Japanese Patent No. 4632589 JP 2012-037670 A

The present invention has been made in view of such a situation, and an object of the present invention is to improve the anti-reflection function and improve the anti-reflection function of the anti-reflection article according to the moth-eye structure.

The present inventor has intensively studied to solve the above-mentioned problems, and has arrived at the idea that microprojections having a plurality of vertices (called multimodal microprojections) are provided in a predetermined distribution, thereby completing the present invention. It came to. In the following, a microprojection having only one vertex is referred to as a single-peak microprojection in comparison with a multimodal microprojection. Further, in the following, when simply referred to as a microprojection, both a single-peak microprojection and a multimodal microprojection are included. Moreover, each convex part which forms each vertex which concerns on a multimodal microprotrusion and a monomodal microprotrusion is called a peak suitably.

Specifically, the present invention provides the following:

(1) In an antireflection article in which microprotrusions are closely arranged and the interval between adjacent microprotrusions is equal to or less than the shortest wavelength of the wavelength band of electromagnetic waves for antireflection, the microprotrusions have a plurality of vertices. It is composed of a ridge-shaped microprojection and a single-peaked microprojection whose apex is one, the average value of the height H in the frequency distribution of the height H of the microprojection is m, the standard deviation is σ, and H <m When the region of −σ is a low altitude region, the region of m−σ ≦ H ≦ m + σ is a medium altitude region, and the region of m + σ <H is a high altitude region, the multi-peak microprojections in each region The ratio between the number Nm and the total number Nt of the microprotrusions in the entire frequency distribution is as follows: Nm / Nt in the middle altitude region> Nm / Nt in the low altitude region and Nm / Nt in the middle altitude region> Nm in the high altitude region / Nt is an antireflection article characterized by satisfying the relationship with Nt .

According to (1), the antireflection article has a low ratio (Nm / Nt) between the number of multi-peak microprojections in the middle altitude region (Nm) and the total number of microprojections (Nt) in the entire frequency distribution. Since it is larger than the ratio (Nm / Nt) between the number of altitude regions and the number of multi-peak microprojections in the high altitude region and the total number of microprojections (Nt) in the entire frequency distribution, it is possible to increase the bandwidth of the antireflection function. it can. Unlike the multimodal microprotrusions caused by poor filling of the resin after the molding process, the multimodal microprotrusions having such a shape are produced by a mold for molding process having a corresponding shape. Thus, the height distribution as designed can be set to ensure uniform and high mass productivity. Furthermore, by setting the distance between the protrusions wider than in the case of defective filling, the scratch resistance can be sufficiently improved, and further the optical characteristics can be improved.
In addition, by providing microprotrusions with superior mechanical strength compared to unimodal microprotrusions, when impact force is applied, the protuberances will not be damaged compared to unimodal microprotrusions alone. As a result, local deterioration of the antireflection function can be reduced, and the occurrence of poor appearance can be reduced. Further, even if the microprojection is damaged, the area of the damaged portion can be reduced, and this can also reduce the local deterioration of the antireflection function and further reduce the appearance defect.

(2) The frequency distribution of the height H of the microprojections is bimodal due to two distributions, and the height that becomes the boundary between the two distributions is Hs, and the height H of the microprojections in a distribution less than Hs The average value is m1, the standard deviation is σ1, the region of H <m1−σ1 is the low altitude region, the region of m1−σ1 ≦ H ≦ m1 + σ1 is the medium altitude region, and the region of m1 + σ1 <H <Hs is the high altitude In the case of the region, the ratio of the number Nm1 of the multi-peak microprojections in each region in the distribution below Hs to the total number Nt of microprojections in the entire frequency distribution is Nm1 / Nt> Nm1 / Nt in the low altitude region and Nm1 / Nt in the medium altitude region> Nm1 / Nt in the high altitude region satisfying the relationship, and the average value of the height H of the microprotrusions in a distribution of Hs or higher is m2. The deviation is σ2 and Hs <H <m When the region of −σ2 is the low altitude region, the region of m2−σ2 ≦ H ≦ m2 + σ2 is the medium altitude region, and the region of m2 + σ2 <H is the high altitude region, the above-mentioned multiple in each region in the distribution of Hs or higher The ratio between the number Nm2 of peak microprojections and the total number Nt of microprojections in the entire frequency distribution is determined as follows: Nm2 / Nt in the middle altitude region> Nm2 / Nt in the low altitude region and Nm2 / Nt in the middle altitude region> The antireflection article according to (1), characterized by satisfying a relationship with Nm2 / Nt in a high altitude region.

According to (2), the distribution of the multimodal microprojections in each distribution can be concentrated in the vicinity of the top of each distribution, and the optical characteristics from the oblique direction can be improved to improve the wide viewing angle characteristics. In addition, the antireflection function having a wider band can be further improved.

(3) In the image display device, the antireflection article described in (1) or (2) is disposed on the light exit surface of the image display panel.

According to (3), it is possible to provide an image display device using an antireflection article having improved scratch resistance and antireflection function.

(4) A mold for manufacturing an antireflective article used for manufacturing an antireflective article, wherein the antireflective article has minute protrusions arranged in close contact with each other, and an interval between adjacent minute protrusions prevents reflection. The frequency is equal to or less than the shortest wavelength in the wavelength band of electromagnetic waves, and the microprotrusions are composed of a plurality of multimodal microprotrusions with a single vertex and a single-peak microprotrusion with a single apex. The average value of height H in the distribution is m, the standard deviation is σ, the region of H <m−σ is the low altitude region, the region of m−σ ≦ H ≦ m + σ is the medium altitude region, and m + σ <H. When the region is a high altitude region, the ratio between the number Nm of the multi-peaked microprojections in each region and the total number Nt of the microprojections in the entire frequency distribution is Nm / Nt> low in the medium altitude region. Nm / Nt in the altitude region and Nm / Nt in the middle altitude region> high altitude region The mold for manufacturing the antireflection article satisfying the relationship with Nm / Nt is a mold for manufacturing the antireflection article characterized in that the minute holes corresponding to the minute protrusions are closely formed. is there.

According to (4), the anti-reflective article manufactured with the mold has a ratio (Nm) of the number of multi-peak microprotrusions in the medium-altitude region to the total number of microprotrusions (Nt) in the entire frequency distribution ( Nm / Nt) is larger than the ratio (Nm / Nt) of the number of multi-peak microprojections in the low altitude region or high altitude region and the total number of microprojections (Nt) in the entire frequency distribution, so that the antireflection function Can be widened. Unlike the multimodal microprotrusions caused by poor filling of the resin after the molding process, the multimodal microprotrusions having such a shape are produced by a mold for molding process having a corresponding shape. Thus, the height distribution as designed can be set to ensure uniform and high mass productivity. Furthermore, by setting the distance between the protrusions wider than in the case of defective filling, the scratch resistance can be sufficiently improved, and further the optical characteristics can be improved.
In addition, when a microprojection having excellent mechanical strength compared to a single-peak microprojection is provided in the antireflection article, when an impact force is applied to the antireflection article, only in the case of a single peak microprojection. In comparison, it is possible to prevent the protrusions from being damaged, thereby reducing local deterioration of the antireflection function and further reducing the occurrence of appearance defects. Further, even if the microprojection is damaged, the area of the damaged portion can be reduced, and this can also reduce the local deterioration of the antireflection function and further reduce the appearance defect.

(5) A method for manufacturing a mold for manufacturing an antireflective article for manufacturing a mold for manufacturing an antireflective article according to (4), wherein the first voltage is applied and an anodizing process is performed, followed by an etching process And performing a flat microhole forming step for forming a microhole having a substantially flat bottom surface on the surface of the plate, and applying a second voltage lower than the first voltage to perform the anodizing process A method of manufacturing a mold for manufacturing an antireflective article, comprising performing an etching process and forming a multi-hole projection micro-hole forming step for forming a plurality of micro-holes on a bottom surface of the micro-hole having a substantially flat bottom surface. is there.

According to (5), a fine hole whose bottom surface is substantially flat is formed on the surface of the plate by the flat fine hole forming step, and the bottom surface is substantially flat formed by the multi-hole projection micro hole forming step. Since a plurality of fine holes are formed on the bottom surface of the hole, it is possible to manufacture a mold for manufacturing an antireflective article in which multimodal microprotrusions have a predetermined distribution.

As for the antireflection article having the moth-eye structure, it is possible to improve the scratch resistance and improve the antireflection function as compared with the conventional one.

1 is a conceptual perspective view showing an antireflection article according to a first embodiment of the present invention. It is a figure where it uses for description of an adjacent protrusion. It is a figure where it uses for description of the maximum point. It is a figure which shows a Delaunay figure. It is a frequency distribution figure with which it uses for description of the measurement of the distance between adjacent protrusions. It is a frequency distribution figure with which it uses for description of minute height. It is a figure which shows the example of the frequency distribution of the height H of the microprotrusion formed in the antireflection article of the present invention. It is a figure which shows the manufacturing process of the antireflection article | item of FIG. It is a figure which shows the roll plate which concerns on the reflection preventing article of FIG. It is a figure which shows the preparation process of the roll plate of FIG. It is a schematic diagram which shows the fine hole produced by the anodic oxidation process and etching process in the manufacturing process of the shaping die. It is a figure with which it uses for preparation of the fine hole from which depth differs. It is a figure which shows frequency distribution of the height H of the microprotrusion of the antireflection article which concerns on Example 1 of this invention. It is a figure which shows frequency distribution of the height H of the microprotrusion of the antireflection article concerning Example 2 of the present invention. It is a figure where it uses for description of a microprotrusion. It is a photograph of multimodal microprojections. It is a perspective view which shows the shape of the microprotrusion of this invention. FIG. 18 is a plan view, a front view, and a side view of FIG. 17. It is a perspective view which shows the shape of the microprotrusion of this invention different from FIG. FIG. 20 is a plan view, a front view, and a side view of FIG. 19. It is a perspective view which shows the shape of the microprotrusion of this invention different from FIG.17 and FIG.19. It is the top view of FIG. 21, a front view, and a side view. It is a conceptual sectional view showing the form in which the envelope surface of the valley bottom of the microprojection exhibits an uneven surface (waviness).

[First Embodiment]
FIG. 1 is a diagram (conceptual perspective view) showing an antireflection article according to a first embodiment of the present invention. This antireflection article 1 is an antireflection film whose overall shape is formed by a film shape. In the image display apparatus according to this embodiment, the antireflection article 1 is held by being attached to the front side surface of the image display panel, and the reflection of external light such as sunlight and electric light on the screen is reduced by the antireflection article 1. And improve visibility. The antireflection article is not limited to a flat film shape, but may be a flat sheet shape or a flat plate shape (referred to as a film, a sheet, or a plate in order of relatively small thickness). In addition, instead of a flat shape, a curved shape, a three-dimensional film shape, a sheet shape, or a plate shape can be used, and various lenses, prisms, and other three-dimensional shapes are appropriately used depending on the application. Can be adopted.

Here, the antireflection article 1 is produced by closely arranging a large number of

microprotrusions

5, 5A, 5B on the surface of the substrate 2 in the shape (form) of a transparent film. A plurality of closely arranged microprotrusions is collectively referred to as a microprotrusion group. Here, the base material 2 is, for example, a cellulose resin such as TAC (Triacetylcellulose), an acrylic resin such as PMMA (polymethyl methacrylate), a polyester resin such as PET (Polyethylene terephthalate), or PP (polypropylene). Polyolefin resins such as PVC, vinyl resins such as PVC (polyvinyl chloride), and various transparent resin films such as PC (polycarbonate) can be applied. As described above, the shape of the antireflection article is not limited to the film shape, and various shapes can be employed. Depending on the shape of such an antireflection article, the base material 2 is made of various transparent materials such as soda glass, potassium glass, lead glass, ceramics such as PLZT, quartz, meteorite, etc. An inorganic material or the like can be applied.

The anti-reflective article 1 forms an uncured resin layer 4 (hereinafter referred to as a receiving layer as appropriate) 4 which forms a fine uneven receiving layer composed of a group of minute protrusions on a base material 2. 4 is subjected to a molding treatment and hardened, whereby the fine protrusions are placed in close contact with the surface of the substrate 2. In this embodiment, an acrylate-based ultraviolet curable resin, which is one of the molding resins used for the molding process, is applied to the receiving layer 4 to form the ultraviolet curable resin layer 4 on the substrate 2. . The antireflection article 1 is manufactured so that the refractive index gradually changes in the thickness direction due to the uneven shape by the microprotrusions, and reduces the reflection of incident light in a wide wavelength range by the principle of the moth-eye structure.

In this way, the microprotrusions produced in the antireflection article 1 are closely arranged so that the distance d between adjacent microprotrusions is equal to or less than the shortest wavelength Λmin (d ≦ Λmin) of the wavelength band of the electromagnetic wave to prevent reflection. The In this embodiment, since the main purpose is to improve visibility by arranging the image display panel, the shortest wavelength is set to the shortest wavelength (380 nm) in the visible light region in consideration of individual differences and viewing conditions. The distance d is set to 100 to 300 nm in consideration of variation. The adjacent minute protrusions related to the distance d are so-called adjacent minute protrusions, which are in contact with the hem portions of the minute protrusions, which are the base portions on the base 2 side. In the anti-reflective article 1, the minute projections are closely arranged so that when a line segment is created so as to sequentially follow the valleys between the minute projections, a large number of polygonal regions surrounding each minute projection are connected in plan view. Thus, a mesh-like pattern is produced. The adjacent minute protrusions related to the distance d are protrusions that share a part of the line segments constituting the mesh pattern. The more accurate definition of “adjacent” or “adjacent” is based on the following.

Note that the minute protrusions are defined in more detail as follows. In the antireflection by the moth-eye structure, the effective refractive index at the interface between the transparent substrate surface and the adjacent medium is continuously changed in the thickness direction to prevent reflection. It is necessary to satisfy the following conditions. With respect to the protrusion spacing, which is one of these conditions, when the minute protrusions are regularly arranged with a constant period as disclosed in, for example, Japanese Patent Application Laid-Open No. 50-70040, Japanese Patent No. 4632589, etc. The interval d between the minute projections to be performed is the projection arrangement period P (d = P). Thus, when the longest wavelength in the visible light band is λmax and the shortest wavelength is λmin, the minimum necessary condition that can exhibit the antireflection effect at the longest wavelength in the visible light band is Λmin = λmax. P ≦ λmax, and the necessary and sufficient condition that can exhibit the antireflection effect for all wavelengths in the visible light band is Λmin = λmin, and therefore P ≦ λmin.

Note that the wavelengths λmax and λmin may vary depending on observation conditions, light intensity (luminance), individual differences, and the like, but are typically λmax = 780 nm and λmin = 380 nm. A preferable condition that can more reliably exhibit an antireflection effect for all wavelengths in the visible light band is d ≦ 300 nm, and a more preferable condition is d ≦ 200 nm. Note that the lower limit value of the period d is usually d ≧ 50 nm, preferably d ≧ 100 nm, for reasons such as the expression of the antireflection effect and the securing of the isotropic (low angle dependency) of the reflectance. On the other hand, the height H of the protrusion is set to H ≧ 0.2 × λmax = 156 nm (assuming λmax = 780 nm) from the viewpoint of exhibiting a sufficient antireflection effect.

However, when the minute protrusions are irregularly arranged as in this embodiment, the distance d between the adjacent minute protrusions varies. More specifically, as shown in FIG. 2, when viewed from the normal direction of the front or back surface of the substrate, when the microprojections are not regularly arranged at a constant period, the repetition period P of the protrusions In some cases, the distance d between adjacent protrusions cannot be defined, and even the concept of adjacent protrusions is suspicious. Therefore, in such a case, it is calculated as follows.

(1) That is, first, an in-plane arrangement of projections (projection arrangement) using an atomic force microscope (hereinafter referred to as AFM) or a scanning electron microscope (hereinafter referred to as SEM). ) Is detected. FIG. 2 is an enlarged photograph actually obtained by an atomic force microscope, and is a photograph showing height by luminance. Since the AFM data is accompanied by the in-plane distribution data of the height of the microprojections, this photo can be said to be a photo showing the in-plane distribution of height by luminance. 2 to 6 (photographs and frequency distribution graphs) are measured and calculated for the microprojection group according to the second embodiment of the present invention, but here, between the projections of the microprojections. This is used to explain the principle and method for calculating the distance and height.

(2) Subsequently, a maximum point of the height of each protrusion (hereinafter simply referred to as a maximum point) is detected from the obtained in-plane arrangement. The maximum point means a point where the height is larger (maximum value) than any point around the vicinity. There are various methods for obtaining the maximum point, such as a method of sequentially comparing the planar view shape and the enlarged photograph of the corresponding cross-sectional shape to obtain the maximum point, and a method of obtaining the maximum point by image processing of the plan view enlarged photo. Can be applied. FIG. 3 is a diagram showing the detection result of the maximum point by the processing of the image data relating to the enlarged photograph shown in FIG. 2, and the portions indicated by black dots in this figure are the maximum points of the respective protrusions. In this process, image data is processed in advance by a low-pass filter having a Gaussian characteristic of 4.5 × 4.5 pixels, thereby preventing erroneous detection of the maximum point due to noise. Further, a maximum point was obtained in units of 1 nm (= 1 pixel) by sequentially scanning a filter for detecting a maximum value of 8 pixels × 8 pixels.

(3) Create a Delaunay diagram (Delaunary Diagram) with the detected local maximum as the base point. Here, Delaunay diagram is obtained by dividing the Voronoi region adjacent to the Voronoi region when the Voronoi division is performed with each local maximum as the generating point, and connecting the adjacent generating points with line segments. This is a net-like figure made up of triangular aggregates. Each triangle is called a Delaunay triangle, and a side of each triangle (a line segment connecting adjacent generating points) is called a Delaunay line. FIG. 4 is a diagram in which the Delaunay diagram (represented by white line segments) obtained from FIG. 3 is superimposed on the original image of FIG. The Delaunay diagram has a dual relationship with the Voronoi diagram. Voronoi division means that a plane is divided by a net-like figure made up of a closed polygon aggregate defined by perpendicular bisectors of line segments (Droney lines) connecting between adjacent generating points. A network figure obtained by Voronoi division is a Voronoi diagram, and each closed region is a Voronoi region.

(4) Next, the frequency distribution of the line segment length of each Delaunay line, that is, the frequency distribution of the distance between adjacent maximum points (hereinafter referred to as the distance between adjacent protrusions) is obtained. FIG. 5 is a histogram of the frequency distribution created from the Delaunay diagram of FIG. As shown in FIG. 2 and FIG. 15, when there is a groove-like recess at the top of the projection, or the top is divided into a plurality of peaks, the distribution of such projection is determined from the obtained frequency distribution. A frequency distribution is created by removing data resulting from a fine structure having a concave portion at the top and a fine structure in which the top is split into a plurality of peaks, and selecting only the data of the projection body itself.

Specifically, in the fine structure in which there is a concave portion on the top of the protrusion, or in the fine structure related to the multi-peak microprotrusion in which the top is divided into a plurality of peaks, the single-peak property that does not have such a fine structure From the numerical range in the case of a microprotrusion, the distance between adjacent maximum points is clearly greatly different. Thus, by removing the corresponding data using this feature, only the data of the projection body itself is selected and the frequency distribution is detected. More specifically, for example, about 5 to 20 adjacent single-peaked microprojections are selected from a magnified photograph of a microprojection (group) in plan view as shown in FIG. 2, and the distance between adjacent maximum points is selected. Is sampled, and a value that deviates from the numerical range obtained by sampling to a value that is clearly smaller outside (usually, the value is 1/2 of the average distance between adjacent maximum points obtained by sampling) The frequency distribution is detected by excluding the following data. In the example of FIG. 5, data having a distance between adjacent maximal points of 56 nm or less (the leftmost small mountain indicated by the arrow A) is excluded. FIG. 5 shows a frequency distribution before performing such exclusion processing. Incidentally, such exclusion processing may be executed by setting the above-described maximum inspection filter.

(5) The average value d _AVG and the standard deviation σ are obtained from the frequency distribution of the distance d between adjacent protrusions thus obtained. Here, when the frequency distribution obtained in this way is regarded as a normal distribution and the average value d _AVG and the standard deviation σ are obtained, the average value d _AVG = 158 nm and the standard deviation σ = 38 nm are obtained in the example of FIG. As a result, the maximum value of the distance d between adjacent protrusions is set to dmax = d _AVG + 2σ, and in this example, dmax = 234 nm.

The same method is applied to define the height of the protrusion. In this case, a relative height difference of each local maximum point position from a specific reference position is acquired from the local maximum point obtained by the above (2), and is histogrammed. FIG. 6 is a diagram showing a histogram of the frequency distribution of the protrusion height H with the protrusion root position obtained in this way as a reference (height 0). The average value _HAVG of the protrusion height and the standard deviation σ are obtained from the frequency distribution based on the histogram. Here in the example of FIG. 6, the mean value _H AVG = 178 nm, the standard deviation sigma = 30 nm. Thus in this example, the height of the projections is an average value _H AVG = 178 nm. In the histogram of the protrusion height H shown in FIG. 6, in the case of a multi-peak microprotrusion, the plurality of data are mixed for one protrusion because of having a plurality of vertices. Therefore, in this case, the frequency distribution is obtained by adopting the vertex having the highest height from among the plurality of vertices belonging to the same microprotrusion as the protuberance.

Note that the reference position for measuring the height of the protrusion described above is based on the bottom of the valley (minimum point of height) between the adjacent minute protrusions as a reference of height 0. However, when the height of the valley bottom itself varies depending on the location (for example, as described later with reference to FIG. 23, when the height of the valley bottom has undulation with a period larger than the distance between adjacent projections of the microprojections, etc.) (1) First, the average value of the height of each valley bottom measured from the front surface or the back surface of the base material 2 is calculated within an area sufficient for the average value to converge. (2) Next, a surface having the height of the average value and parallel to the front surface or the back surface of the substrate 2 is considered as a reference surface. (3) Then, the height of each microprotrusion from the reference surface is calculated by setting the reference surface to a height of 0 again.

If the protrusions are irregularly arranged, when this way the maximum value of the adjacent protrusions distance obtained by dmax = d AVG ₊ 2σ, average H _AVG height of projections are arranged regularly It has been found necessary to satisfy the above conditions. Specifically, the condition of the distance between the microprotrusions that exhibits the antireflection effect is dmax ≦ Λmin. The minimum necessary condition that can exhibit the antireflection effect at the longest wavelength in the visible light band is Λmin = λmax, and therefore dmax ≦ λmax, and the antireflection effect can be achieved for all wavelengths in the visible light band. The necessary and sufficient condition is Λmin = λmin, and therefore dmax ≦ λmin. A preferable condition that can more reliably exhibit the antireflection effect for all wavelengths in the visible light band is dmax ≦ 300 nm, and a more preferable condition is dmax ≦ 200 nm. Also, dmax ≧ 50 nm is usually satisfied and dmax ≧ 100 nm is preferable because of the antireflection effect and ensuring the isotropic (low angle dependency) of the reflectance. The height of the protrusion is set to _HAVG ≧ 0.2 × λmax = 156 nm (assuming λmax = 780 nm) in order to exhibit a sufficient antireflection effect. However, from the viewpoint of ensuring the antireflection function to a practically sufficient level, the average inter-protrusion distance dave may be set so that dave ≦ λmin.

2 to 6, dmax = 234 nm ≦ λmax = 780 nm, and it can be seen that the antireflection effect can be sufficiently achieved by satisfying the condition of dmax ≦ λmax. In addition, since the shortest wavelength λmin in the visible light band is 380 nm, it can be seen that the sufficient condition dmax ≦ λmin for exhibiting the antireflection effect in all visible light wavelength bands is also satisfied. Since dave ≦ dmax, it can be seen that the condition of dave ≦ λmin is also satisfied. When the average protrusion the height _H AVG = 178 nm Also, the average projection height _{H AVG} ≧ 0.2 × λmax = _156nm becomes (as the longest wavelength .lambda.max = 780 nm in the visible light wavelength band), realizing a sufficient antireflection effect It can be seen that the conditions regarding the height of the protrusions to satisfy are also satisfied. Since the standard deviation σ = 30 nm, the relational expression H _AVG -σ = 148 nm <0.2 × λmax = 156 nm is established, and therefore, statistically, 50% or more and 84% or less of all protrusions It can be seen that the condition of the height of the protrusion (178 nm or more) is satisfied. In addition, from the observation result by AFM and SEM and the analysis result of the height distribution of the microprojections, the multi-peak microprojections tend to be generated more frequently in the microprojections having a higher height than the microprojections having a relatively low height. It has been found.

As in this embodiment, when monomodal microprojections and multimodal microprojections are mixed, as in the case where monomodal microprojections having different aspect ratios are mixed, low reflection in a wide wavelength band. The rate can be secured. The aspect ratio is defined as H / W, which is a ratio obtained by dividing the height H of the minute protrusions by the diameter W (also referred to as width or thickness) at the bottom of the valley. Here, the diameter at the bottom of the valley coincides with the diameter (at the bottom) of the column if the shape of the microprotrusion near the bottom of the valley is a column. If the shape of the vicinity of the valley bottom of the microprojection is not a cylinder and the diameter of the bottom surface obtained by crossing the virtual plane connecting the valley bottom and the microprojection differs depending on the in-plane direction, the maximum value is set to the microprojection. Of the diameter. For example, when the bottom shape of the microprojection is an ellipse, the diameter is the major axis. In addition, when the bottom surface shape of the minute protrusion is a polygon, the diameter is the maximum diagonal length. In addition, when the width of the bottom of the valley (region consisting of the minimum point of the height) is smaller than the diameter and 20% or less, the average value (H / W) ave of the aspect ratio H / W of each microprotrusion is In terms of design, it can be substantially regarded as Have / dave.

That is, when a fine hole is produced by anodizing treatment, as already known in Japanese Patent Laid-Open No. 2003-43203, etc., the distance between adjacent fine holes (corresponding to a pitch when there is no constant distribution) and fine It is proportional to the depth of the hole. Thus, when a mold for molding is produced by repeating anodization treatment and etching treatment, and this type of antireflection article is produced by molding process using this mold for molding, a single peak produced The aspect ratio, which is the ratio between the width and height of the base portion, is maintained substantially constant in the sexual microprojections.

The anti-reflective function of the anti-reflective article depends not only on the interval between the microprojections but also on the aspect ratio, and when the aspect ratio is constant, for example, even when a sufficiently low reflectance can be secured in the visible light range, However, the reflectance increases as compared with the visible light region, and the antireflection function is insufficient. If the distance between adjacent protrusions is further reduced so that a sufficient antireflection function can be secured in the ultraviolet region, the antireflection function will be lowered in the infrared region.

However, in a group of microprojections including multimodal microprojections, the distance between the peaks existing near the top of the same microprojection is smaller than the distance between adjacent projections (usually about 100 to 200 nm) (usually about 10 to 50 nm). Due to the contribution of the distance between the peaks, it is possible to ensure an antireflection function that reduces the effective spacing between adjacent projections compared to a group of minute projections consisting only of single-peaked microprojections having the same distance between adjacent projections. Thereby, a low reflectance can be ensured in a wide wavelength band by mixing the multimodal microprojections and the monomodal microprojections. When a sufficiently small reflectance is ensured in a wide wavelength band centered on the visible light region, the distance between adjacent protrusions that contributes to the antireflection performance for light in the wavelength range of 480 to 660 nm in the visible light region, that is, d ≦ It is desirable to mix multimodal microprojections and monomodal microprojections in microprojections with 400 nm, preferably d ≦ 300 nm.

Here, the multimodal microprotrusions formed on the antireflection article need to be formed so as to satisfy the following conditions in order to improve the antireflection function for incident light in the visible light region described above. is there.
FIG. 7 is a diagram illustrating an example of the frequency distribution of the height H of the fine protrusions formed on the antireflection article. As shown in FIG. 7, the average value of the height in the frequency distribution of the height H of the microprojections is m, the standard deviation is σ, the region of H <m−σ is the low altitude region of the microprojections, and m− When the region of σ ≦ H ≦ m + σ is a medium altitude region and the region of m + σ <H is a high altitude region, the number Nm of multimodal microprojections in each region and the total number Nt of microprojections in the entire frequency distribution It is necessary for the ratio to satisfy the following relationships (a) and (b).
(A) Nm / Nt in the middle altitude region> Nm / Nt in the low altitude region
(B) Nm / Nt in middle altitude region> Nm / Nt in high altitude region

FIG. 8 is a diagram showing a manufacturing process of the antireflection article 1. In the manufacturing process 10, in the resin supply process, an uncured and liquid ultraviolet curable resin that forms a microprojection-shaped receiving layer is applied to the base material 2 in the form of a belt-shaped film by the die 12. In addition, about application | coating of an ultraviolet curable resin, not only the case by the die | dye 12 but various methods are applicable. Subsequently, in this manufacturing process 10, the substrate 2 is pressed and pressed onto the peripheral side surface of the roll plate 13 which is a mold for shaping the antireflection article by the pressing roller 14, and thereby the substrate 2 is uncured. The liquid acrylate-based ultraviolet curable resin is brought into close contact, and the fine concavo-convex recesses formed on the peripheral side surface of the roll plate 13 are sufficiently filled with the ultraviolet curable resin. In this state, in this manufacturing process, the ultraviolet curable resin is cured by irradiation with ultraviolet rays, and thereby a microprojection group is produced on the surface of the substrate 2. In this manufacturing process, the substrate 2 is peeled off from the roll plate 13 through the peeling roller 15 together with the cured ultraviolet curable resin. In the production process 10, an anti-reflection article 1 is produced by producing an adhesive layer or the like on the substrate 2 as necessary, and then cutting it into a desired size. Accordingly, the antireflection article 1 is mass-produced efficiently by sequentially molding the fine shape produced on the peripheral side surface of the roll plate 13 which is a mold for molding on the long base material 2 made of a roll material. The

FIG. 9 is a perspective view showing the configuration of the roll plate 13. The roll plate 13 has a fine concavo-convex shape formed on the peripheral side surface of the base material, which is a cylindrical metal material, by repeating anodizing treatment and etching treatment, and the fine concavo-convex shape is formed on the substrate 2 as described above. It is shaped. For this reason, a columnar or cylindrical member in which a high-purity aluminum layer is provided at least on the peripheral side surface is used as the base material. More specifically, in this embodiment, a hollow stainless steel pipe is applied to the base material, and a high-purity aluminum layer is provided directly or via various intermediate layers. In addition, it may replace with a stainless steel pipe and may apply pipe materials, such as copper and aluminum. In the roll plate 13, fine holes are densely formed on the peripheral side surface of the base material by repeating the anodizing treatment and the etching treatment, and the fine holes are dug, and the diameter of the roll plate 13 increases as it approaches the opening. The concavo-convex shape is produced by gradually increasing the diameter of the fine holes. As a result, the roll plate 13 is closely formed with fine holes whose diameter gradually decreases in the depth direction, and the diameter of the antireflection article 1 gradually decreases as it approaches the top corresponding to the fine holes. A fine concavo-convex shape is produced by a microprojection group consisting of a large number of microprojections. At that time, by appropriately adjusting various conditions such as the purity (impurity amount), bath concentration, crystal grain size, anodizing treatment and / or etching treatment of the aluminum layer, the shape of the fine protrusion unique to the present invention is obtained.

[Anodic oxidation treatment, etching treatment]
FIG. 10 is a diagram illustrating a manufacturing process of the roll plate 13. In this manufacturing process, the peripheral side surface of the base material is made into a super mirror surface by an electrolytic composite polishing method that combines electrolytic elution action and abrasion action by abrasive grains (electrolytic polishing). Subsequently, in this step, in the aluminum layer forming step, aluminum is sputtered on the peripheral side surface of the base material to produce a high-purity aluminum layer. Subsequently, in this process, the base material is processed by alternately repeating the anodic oxidation processes A1,..., AN, and the etching processes E1,.

In this manufacturing process, in the anodizing step A1,..., AN, a fine hole is produced on the peripheral side surface of the base material by an anodizing method, and the produced fine hole is further dug. Here, in the anodic oxidation step, various methods applied to the anodic oxidation of aluminum can be widely applied, for example, when a carbon rod, a stainless steel plate, or the like is used for the negative electrode. Further, as the solution, various neutral and acidic solutions can be used, and more specifically, for example, sulfuric acid aqueous solution, oxalic acid aqueous solution, phosphoric acid aqueous solution and the like can be used. In the manufacturing steps A1,..., AN, the fine holes are formed in shapes corresponding to the target depth and the shape of the fine protrusions, respectively, by managing the liquid temperature, the applied voltage, the time for anodization, and the like.

In the subsequent etching process E1,..., EN, the mold is immersed in an etching solution, the hole diameter of the fine hole produced and dug in the anodizing process A1,. These fine holes are shaped so that the hole diameter becomes smaller and smoother. As the etching solution, various etching solutions that are applied to this type of treatment can be widely applied. More specifically, for example, a sulfuric acid aqueous solution, an oxalic acid aqueous solution, a phosphoric acid aqueous solution, or the like can be used. Note that the same solution as the solution used for the anodic oxidation treatment may be used without applying a voltage so that the solution can be used also as an etching solution. As a result, in this manufacturing process, the anodizing process and the etching process are alternately performed a plurality of times, so that fine holes for forming are formed on the peripheral side surface of the base material.

[Formation process of minute holes to form minute protrusions]
Next, a method for forming multi-peaked microprojections and forming fine holes in which the height distribution of the microprojections is controlled will be described. As described above, the fine hole formed in the shaping mold (roll plate) is formed by alternately repeating the anodizing treatment and the etching treatment, and the applied voltage in the repeated anodizing treatment is varied. Thus, the depth of the fine holes (the height distribution of the fine protrusions) can be controlled. Here, since the applied voltage in the anodizing process and the interval (pitch) between the fine holes to be formed are in a proportional relationship, the applied voltage of the anodizing process can be varied in the repetition of the anodizing process and the etching process. For example, it is possible to mix fine holes having different times for digging in the depth direction and control the ratio.

In addition, in the case where the applied voltage in the anodizing process is varied in this way, a plurality of micro holes are created on the bottom surface of the micro hole having a large thickness (diameter), and the micro hole related to the multimodal micro protrusion is formed. It can be. By controlling the height of the fine hole having a large thickness, the height distribution can be controlled also for the multimodal microprojections.

FIG. 11 is a schematic diagram for explaining the microholes related to the multimodal microprojections, and is a diagram showing the microholes produced by the anodic oxidation process and the etching process in the molding die manufacturing process.
As described above, the relationship between the applied voltage in the anodic oxidation process and the pitch of the fine holes is proportional, but in practice, the pitch of the fine holes varies due to the grain boundaries of the aluminum used for the treatment. However, in FIG. 11, it is assumed that the fine holes are formed in a regular arrangement, assuming that this variation does not exist. In FIGS. 11 (a) to 11 (e), the left figure shows an enlarged view of the surface of the roll plate 13, and the right figure shows an aa cross-sectional view in the left figure.

(First step)
As shown in FIG. 11A, first, the voltage V1 is applied to the aluminum layer on the surface of the shaping mold to perform the anodic oxidation step A1, and then the etching step E1 is performed to form the fine holes f1. Form. Here, the anodic oxidation step A1 is to create a trigger for the anodic oxidation treatment that follows the flat surface of aluminum. In this case, the etching process may be omitted as appropriate.

(Second step)
Next, after applying the voltage V2 (V2> V1) higher than the voltage V1 to execute the anodic oxidation step A2, the etching step E2 is executed. As a result, in the anodizing step A2, as shown in FIG. 11B, among the fine holes f1 formed in the previous anodizing step A1, the fine holes f1 having an interval corresponding to the anodizing step A2 are further dug down. .
In the present embodiment, a process of digging every two fine holes f1 formed in the previous anodizing process A1 is performed by the anodizing process A2. Therefore, the surface of the shaping mold is formed with fine holes f2 that are dug wide and deep every other two, and the surface of the roll plate 13 has a mixture of the fine holes f1 and f2. Become.

(Third step)
Subsequently, after applying the voltage V3 (V3> V2) higher than the voltage V2 to execute the anodic oxidation step A3, the etching step E3 is executed. In this step, fine holes with different pitches are produced. Specifically, when the voltage to be applied is gradually increased from the voltage V2 to the voltage V3, and the increase in the applied voltage is executed discretely (stepwise), the height distribution of the fine protrusions (depth distribution of the fine holes) ) Can be produced discretely, and when the applied voltage is continuously increased, the height distribution of the microprotrusions can be set to a normal distribution. Therefore, in this embodiment, the application time of the applied voltage in the anodizing step A3 and the processing time of the etching step are set longer than those in the first step and the second step described above, as shown in FIG. As described above, two fine holes f1 formed in the first anodic oxidation step A1 are dug wide and deep so as to be combined into one, and the bottom surface of the fine hole f3 integrated into one is substantially flat. (Flat fine hole forming step). Here, “substantially flat” means not only a state where the bottom surface of the fine hole is flat but also a state where the bottom surface is curved with a large curvature radius.

(Fourth process)
Subsequently, after applying the voltage V4 (V4> V3) higher than the voltage V3 to execute the anodic oxidation step A4, the etching step E4 is executed. In this step, fine holes are created with a pitch based on the desired interprotrusion spacing. Also in this anodizing step A4, the applied voltage is gradually increased from the voltage V3 to the voltage V4. As a result, a part of the fine hole f3 dug by the third step is further dug, and as a result, as shown in FIG. 11 (d), the fine hole f4 is formed. High unimodal microprotrusions are formed.

(Fifth step)
Subsequently, after changing the applied voltage to the voltage V1 in the first step and performing the anodic oxidation step A5, the etching step E5 is performed. In this step, as shown in FIG. 11 (e), on the bottom surface of the fine hole f3 formed in the anodizing step A3 and not affected by the anodizing step A4 of the fourth step, A plurality of fine holes are formed to form a fine hole f5 corresponding to the multi-peak microprotrusions (a multi-hole protrusion micro-hole forming step). Here, by adjusting the magnitude of the voltage V1 to be applied, the number of fine holes formed in the bottom surface of the fine hole f5 can be increased or decreased, and the interval between the fine holes can be adjusted.

As described above, the fine holes f1, f2, and f4 for forming the minute protrusions having different heights and the minute holes f5 for forming the multimodal minute protrusions are formed on the surface of the molding die.
Here, in this series of steps, the fine holes f1 and f2 having different depths produced in the first step and the second step are dug in the third step to form a substantially flat fine hole f3 on the bottom surface. In the fourth step, the minute hole f3 is dug to produce the minute hole f4 related to the single-peaked minute protrusion. In the fifth step, the bottom surface of the minute hole f3 is processed to obtain a large number of holes. The minute hole f5 related to the ridge-like minute protrusion is produced. Here, by controlling the application time, the processing time, the processing time of the etching process, etc. of the anodizing process according to the first to fourth processes, the depth of the fine hole produced in each process is controlled. Thus, it is possible to control the height distribution of the microprojections and the height distribution of the multimodal microprojections. Note that the above-described first to fifth steps can be omitted or repeated as necessary, or the steps can be integrated.

FIG. 12 is a diagram for explaining the process of forming micro holes with different depths related to the control of the height distribution of the microprotrusions in comparison with FIG.

(First step)
Here, as shown in FIG. 12A, in the first step, first, the voltage V1 is applied to the aluminum layer on the surface of the molding die to perform the anodizing step A1, and then the etching step E1. To form a fine hole f1. Here, the anodic oxidation step A1 is to create a trigger for the anodic oxidation treatment that follows the flat surface of aluminum. In this case, the etching process may be omitted as appropriate.

(Second step)
Next, after applying the voltage V2 (V2> V1) higher than the voltage V1 to execute the anodic oxidation step A2, the etching step E2 is executed. As a result, in the anodizing step A2, as shown in FIG. 12B, among the fine holes f1 formed in the previous anodizing step A1, fine holes f1 having a distance corresponding to the anodizing step A2 are formed. Dig further.

Here, when the applied voltage V2 is set to V2 = 2 × V1, a process of digging every other minute hole f1 formed in the previous anodizing process A1 is performed by the anodizing process A2. Accordingly, every other wide and deeply drilled fine hole f2 is formed on the surface of the molding die, and the minute hole f1 and the minute hole 2 are mixed on the surface of the mold. It becomes a state.

(Third step)
Subsequently, after applying the voltage V3 (V2>V3> V1) between the voltage V1 and the voltage V2 to execute the anodic oxidation step A3, the etching step E3 is executed. In this step, fine holes with different pitches are produced. Specifically, the voltage to be applied is set to the voltage V3, and every other specific minute hole f1 as illustrated between the minute holes f2 arranged in the plane vertically and horizontally is dug wide and deep. Here, when the applied voltage V3 is set to V3 = (V1) ^1/2 , the application time of the applied voltage in the anodizing step A3 and the processing time of the etching step are set longer than those in the first step described above. As shown in FIG. 11 (c), among the fine holes f1 formed in the first anodic oxidation step A1, the fine hole f1 located at the center of the smallest square surrounded by the four fine holes f2 is selected. Deeply digging deeply. At the same time, among the fine holes f2 formed in the second anodic oxidation step A2, a part of the fine holes f2 having the positional relationship shown in FIG. 12C is further dug down to become fine holes f3.

As a result, as shown in FIG. 12C, fine holes f2 and f3 (medium respectively) deeper than f1 around the fine hole f1 (which corresponds to the minute protrusion having the lowest height). And a mold having a surface structure in which a group of holes surrounded by a small projection having a high height is arranged in a plane.

In this way, the depth of the micro holes can be greatly varied by changing the micro holes to be drilled by switching the applied voltage in multiple times of anodizing treatment, thereby controlling the height of the micro protrusions by the intended distribution can do.

Next, an example of the antireflection article manufactured by the shaping mold manufactured by the above-described method will be described.
[Example 1]
FIG. 13 is a diagram showing a frequency distribution of the height H of the microprojections of the antireflection article of Example 1.
The shaping mold for producing the antireflection article of Example 1 is obtained by continuously changing the applied voltage of the anodizing treatment in the second step, the third step, and the fourth step. In the fifth step, the voltage is reduced from the applied voltage in the fourth step.

More specifically, the example of FIG. 13 is a case where the anodizing step and the etching step are repeated five times, and the applied voltage of the first anodizing step is V1 (a constant voltage in the range of 15V to 35V). ), The applied voltages in the second, third, fourth, and fifth anodic oxidation steps are 2V1, 3.5V1, 5V1, and V1, respectively. The anodizing treatment was performed for 100 seconds using an oxalic acid aqueous solution having a concentration of 0.02M. In the etching step, an etching process was performed for 45 seconds using an aqueous oxalic acid solution having a concentration of 0.02M, and then an etching process was performed for 110 seconds using an aqueous solution of phosphoric acid having a concentration of 1.0M.

In the antireflection article manufactured by this mold, the height distribution of the microprojections shows a normal distribution, and in a relatively narrow range centered on the vertical line of the surface on which the microprojections are formed, A good antireflection function can be ensured. Also, at this time, in such a height distribution, the multimodal microprojections (two and three vertices are indicated by two peaks and three peaks, respectively) also have a normal distribution in which the average values of the heights are almost the same. Accordingly, the scratch resistance function and the optical property improvement function of the multi-modal microprotrusions can be efficiently exhibited. Thereby, it can be used for a small display used in a mobile phone, a portable game machine, and the like.

As shown in FIG. 13, the antireflection article of Example 1 manufactured by the above-described method has an average height of minute protrusions of m = 145.7 nm and a standard deviation of σ = 22.1 nm. is there.
Here, in the frequency distribution of the height H of the microprotrusions, the low altitude region is H <m−σ = 123.6 nm, and the middle altitude region is m−σ = 13.6 nm ≦ H ≦ m + σ = 167.8 nm. Thus, the high altitude region is H> m + σ = 167.8 nm.
The total number Nt of microprojections in the entire frequency distribution is 263. Further, since the number Nm of multi-modal microprotrusions in the middle altitude region is 23, Nm / Nt in the middle altitude region is 0.087. Since the number Nm of the multimodal microprotrusions in the low altitude region is two, Nm / Nt in the low altitude region is 0.008. Since the number Nm of multimodal microprojections in the high altitude region is 5, the Nm / Nt in the high altitude region is 0.019.

Therefore, the antireflection article of the present example has the above-described relationships (a) and (b), that is,
(A) Nm / Nt in the middle altitude region = 0.087> Nm / Nt = 0.008 in the low altitude region
(B) Nm / Nt = 0.087 in the medium altitude region> Nm / Nt = 0.19 in the high altitude region
Satisfied.

As described above, in the antireflection article of Example 1, the ratio (Nm / Nt) of the number (Nm) of multimodal microprotrusions in the medium altitude region and the total number of microprotrusions (Nt) in the frequency distribution is low in the low altitude region. Since the multi-peak microprotrusions are formed so as to be larger than the ratio of the high altitude region, the reflectance for incident light in the visible light region can be reduced, and the antireflection product has a wide antireflection function. Can be achieved.
In addition, this antireflection article has such a height distribution that the average value of the heights of the multimodal microprotrusions (two and three vertices are indicated by two peaks and three peaks, respectively) is almost the same. Since the matched normal distribution can be obtained, the viewing angle characteristic can be limited, and it can be used for a small display used in a mobile phone, a portable game machine, or the like. In addition, the scratch resistance of the multimodal microprotrusions can be improved efficiently.
Further, by adopting the above-described configuration, the antireflection article has a small ratio of multi-peak microprojections distributed in microprojections having a high height (180 nm or more) and a large ratio of single-peak microprojections. Even if the object is in frictional contact with the microprotrusions, the high unimodal microprotrusions come into contact first, and the contact with the multimodal microprotrusions that mainly improve the antireflection function is suppressed. can do.

[Example 2]
FIG. 14 is a diagram showing a frequency distribution of the height H of the microprojections of the antireflection article of Example 2.
The shaping mold for producing the antireflection article of Example 2 performs the anodizing process by gradually changing the applied voltage, and in the fourth step, it is more than the maximum voltage according to the example of FIG. The anodizing treatment is performed with a high voltage.

More specifically, in the example of FIG. 14, the anodizing process and the etching process were performed with the same number of repetitions, solution, and processing time as in the example of FIG. 13. In the example of FIG. 14, when the applied voltage in the first anodic oxidation step is V1 (a constant voltage in the range of 15V to 35V), the second, third, fourth, In this example, the voltages applied in the second anodic oxidation step are 2.5 V1, 4 V1, 6 V1, and V1 ^1/2 to V1, respectively. In the second to fourth anodic oxidation steps, the start voltage of the second anodic oxidation treatment and the end voltage of the fourth anodic oxidation treatment are set to 2.5 V1 and 6 V1, respectively, and the applied voltage is gradually increased. Increased.

In the example of FIG. 14, the height distribution of the microprotrusions having distribution peaks on the high side and the low side is discrete, that is, a bimodal distribution. Corresponding to the distribution of multimodal microprojections.

In the antireflection article of Example 2, the frequency distribution has a bimodal distribution, the average height of the microprojections of the entire frequency distribution is m = 195.7 nm, and the standard deviation is σ = 57.2 nm. is there.

Here, in the frequency distribution of the height H of the microprojections, the low altitude region is H <m−σ = 138.5 nm, and the middle altitude region is m−σ = 138.5 nm ≦ H ≦ m + σ = 252.9 nm. Thus, the high altitude region is H> m + σ = 254.7 nm.
The total number Nt of fine protrusions in the entire frequency distribution is 131. In addition, since the number Nm of multimodal microprotrusions in the middle altitude region is 21, the Nm / Nt in the middle altitude region is 0.160. Since the number Nm of the multimodal microprotrusions in the low altitude region is 3, Nm / Nt in the low altitude region is 0.023. Since the number Nm of multimodal microprojections in the high altitude region is 0, Nm / Nt in the high altitude region is 0.
Therefore, the antireflection article of the present example has the above-described relationships (a) and (b), that is,
(A) Nm / Nt = 0.160 in the middle altitude region> Nm / Nt = 0.024 in the low altitude region
(B) Nm / Nt = 0.160 in the middle altitude region> Nm / Nt = 0 in the high altitude region
Satisfied.

Also, as described above, the frequency distribution of the height H of the microprojections of the antireflection article of Example 2 is bimodal, that is, there are two distribution peaks. In this case, a low altitude region, a medium altitude region, and a high altitude region are also defined for the peaks of each distribution, and the number of multi-peak microprojections in each region of each peak and the total number Nt of microprojections in the entire frequency distribution, It is necessary to evaluate the size of the ratio.

Specifically, when the height of the boundary between the peaks is Hs, the average value of the height H is m1 for the peaks of the distribution below Hs (the peaks of the distribution on the lower side), When the standard deviation is σ1, the region of H <m1−σ1 is the low altitude region, the region of m1−σ1 ≦ H ≦ m1 + σ1 is the medium altitude region, and the region of m1 + σ1 <H <Hs is the high altitude region, The ratio between the number Nm1 of the multimodal microprojections in each region in the peak of the distribution below Hs and the total number Nt of microprojections in the entire frequency distribution needs to satisfy the following relationships (c) and (d). .
(C) Nm1 / Nt in the middle altitude region> Nm1 / Nt in the low altitude region
(D) Nm1 / Nt in the medium altitude region> Nm1 / Nt in the high altitude region

For a distribution higher than Hs (distribution on the higher side), the average value of height H is m2, the standard deviation is σ2, the region where Hs <H <m2-σ2 is the low altitude region, and m2 When the region of −σ2 ≦ H ≦ m2 + σ2 is a medium altitude region and the region of m2 + σ2 <H is a high altitude region, the number Nm2 of multimodal microprotrusions in each region in the distribution of Hs or higher and the entire frequency distribution The ratio with the total number Nt of microprojections needs to satisfy the following relationships (e) and (f).
(E) Nm2 / Nt in the middle altitude region> Nm2 / Nt in the low altitude region
(F) Nm2 / Nt in the middle altitude region> Nm2 / Nt in the high altitude region

Here, the average value of the heights H of the fine protrusions in the distribution of less than Hs (the lower side) is m1 = 52.9 nm, and the standard deviation is σ1 = 24.8 nm. The boundary of each distribution is obtained as Hs = 100 nm by statistically processing the data of the height of the frequency distribution.
Therefore, the low altitude region of the distribution below Hs is H <m1-σ1 = 28.1 nm, the middle altitude region is m1-σ1 = 28.1 nm ≦ H ≦ m1 + σ1 = 77.7 nm, and the high altitude region is m1 + σ1 = 77.7 nm <H <Hs = 100 nm.
In addition, since the number Nm1 of the multi-modal microprotrusions in the middle altitude region is two, Nm1 / Nt in the middle altitude region is 0.015. Since the number Nm1 of the multi-modal microprojections in the low altitude region is 0, Nm1 / Nt in the low altitude region is 0. Since the number Nm1 of the multimodal microprotrusions in the high altitude region is 0, Nm1 / Nt in the high altitude region is 0.
Therefore, the antireflective article of this example has a relationship of (c) and (d) above in a distribution less than Hs, that is,
(C) Nm1 / Nt = 0.015 in the middle altitude region> Nm1 / Nt = 0 in the low altitude region
(D) Nm1 / Nt = 0.015 in the middle altitude region> Nm1 / Nt = 0 in the high altitude region
Satisfy the relationship.

In addition, for the fine protrusions having a distribution of Hs or higher (higher height side), the average value of the height H is m2 = 209.2 nm, and the standard deviation is σ2 = 39.4 nm.
Therefore, the low altitude region with a distribution of Hs or higher is Hs = 100 nm ≦ H <m2−σ2 = 169.9 nm, and the middle altitude region is m2−σ2 = 169.9 nm ≦ H ≦ m2 + σ2 = 248.7 nm. The altitude region is m + σ = 248.7 nm <H.
Further, since the number Nm2 of the multi-modal microprotrusions in the middle altitude region is 19, Nm2 / Nt in the middle altitude region is 0.145. Since the number Nm2 of the multimodal microprojections in the low altitude region is 3, Nm2 / Nt in the low altitude region is 0.023. Since the number Nm2 of multimodal microprojections in the high altitude region is 0, Nm2 / Nt in the high altitude region is 0.
Therefore, the antireflective article of this example has the relationship of (e) and (f) above even in the distribution of Hs or higher, that is,
(E) Nm2 / Nt = 0.145 in the middle altitude region> Nm2 / Nt = 0.024 in the low altitude region
(F) Nm2 / Nt = 0.145 in the middle altitude region> Nm2 / Nt = 0 in the high altitude region
Satisfy the relationship.

From the above, in the antireflection article of Example 2, the ratio (Nm / Nt) of the number (Nm) of multimodal microprojections in the medium altitude region and the total number of microprojections (Nt) in the frequency distribution is low in the low altitude region. Since the multi-peak microprotrusions are formed so as to be larger than the ratio of the high altitude region, the reflectance for incident light in the visible light region can be reduced, and the antireflection product has a wide antireflection function. Can be achieved.
In addition, the antireflection article of Example 2 has a bimodal distribution of frequencies and satisfies the above relationships (c) to (f). It can be concentrated near the top. Thereby, the optical characteristic from an oblique direction can be improved and the wide viewing angle characteristic can be improved. In addition, the antireflection function in the ultraviolet region is improved by the multimodal microprotrusions on the lower side distribution, and the antireflection function in the visible light region is improved by the multimodal microprojections present on the higher side distribution. Therefore, the antireflection function having a wider band can be further improved.

Further, for the infrared region, it is necessary to form single-peaked microprojections having a wide arrangement interval (pitch) and a high height in order to ensure the antireflection function. Since the ratio of the multimodal microprotrusions distributed to the microprojections having a high height is small, it is possible to prevent the deterioration of the antireflection function in the infrared region due to the presence of the multimodal microprotrusions.
In addition, with such a configuration, even if another object comes into frictional contact with the microprotrusions, the high single-peak microprotrusions come into contact first, and the contact with the multimodal microprotrusions is suppressed. can do.

The characteristics of these multimodal microprotrusions are unique characteristics of the multimodal microprotrusions produced by the microholes having the corresponding shape of the shaping mold, and Japanese Patent Application Laid-Open No. 2012-037670 discloses. This is a feature that cannot be obtained by the multimodal microprotrusions caused by poor filling of the disclosed resin. That is, the multi-peak microprotrusions due to poor filling of the resin are produced by not sufficiently filling the fine holes that are originally produced as single-peak microprotrusions, so the distance between the vertices is extremely small. Thus, it is difficult to sufficiently improve the scratch resistance, and it is also difficult to improve the optical characteristics as described above.

In addition, the multi-peak microprotrusions due to poor filling also have the disadvantage that the reproducibility is poor, thereby making it impossible to mass-produce a uniform product, whereas the multi-peak microprotrusions according to this embodiment are so-called High reproducibility can be ensured by the mold. Further, as described in detail for the above-described embodiments, the height distribution of the multimodal microprotrusions can be controlled, while such control is difficult for the poorly filled multimodal microprotrusions.

[Improved scratch resistance]
By the way, when the anti-reflective article was produced by producing fine holes by alternately repeating the anodizing treatment and the etching treatment, there was room for improvement in the scratch resistance as described above. Therefore, when the antireflection article was observed in detail, it consists only of single-peaked microprojections having only one apex, such as a polygonal pyramid shape and a rotating paraboloid shape, as in this type of conventional antireflection article, If the height of each vertex is also made uniform, for example, when another object comes into contact, the shape of the microprojections is uniformly damaged over a wide range, thereby locally deteriorating the antireflection function. In addition, it was found that white spots, scratches, etc. occurred at the contact points, resulting in poor appearance. However, it has been found that such scratch resistance is improved by changing the production conditions of the roll plate.

When the surface shape of such an antireflection article with improved scratch resistance was observed with an AFM (Atomic Force Microscope) and an SEM (Scanning Electron Microscope), a large number of microprojections were observed. It was found that there are multimodal microprojections having a plurality of vertices. Although various types of microscopes are provided here for observing the fine shape, AFM and SEM are suitable for observing the surface shape of the antireflection article without damaging the fine structure. Yes.

Here, the multimodal microprotrusions not only have a plurality of vertices, but when the microprotrusions are viewed in plan from the tip side, they are divided into a plurality of regions by grooves formed outward from the center, Each of the plurality of regions is formed to be a peak related to each vertex. In addition, this multimodal microprotrusion is produced by a molding process of microholes having a corresponding shape, and the microholes related to such multimodal microprotrusions are repeated in the anodizing process and the etching process. Fine holes made in close proximity are produced integrally by an etching process. As a result, the multimodal microprotrusions are formed such that the perimeter when the microprotrusions are viewed in plan from the tip side is longer than that of the single-peak microprotrusions. This point can be seen from FIG. 16 described later. The shape of these multimodal microprojections is different from the multimodal microprotrusions caused by poor filling of the resin during the molding process disclosed in Japanese Patent Application Laid-Open No. 2012-037670.

FIG. 15 is a cross-sectional view (FIG. 15 (a)), a perspective view (FIG. 15 (b)), and a plan view (FIG. 15 (c)) for explaining the multimodal microprotrusions having a plurality of vertices. Note that FIG. 15 is a diagram schematically showing for easy understanding, and FIG. 15A is a diagram showing a cross section by a broken line connecting the vertices of continuous minute protrusions. In FIGS. 15B and 15C, the xy direction is the in-plane direction of the substrate 2, and the z direction is the height direction of the microprojections. In the antireflection article 1, many microprotrusions 5 are gradually cut along a cross-sectional area (a plane perpendicular to the height direction (a plane parallel to the XY plane in FIG. 15) as they move away from the base material 2 toward the top. The cross-sectional area) is reduced, and one vertex is produced. However, in some cases, as if a plurality of microprotrusions were combined, a groove g was formed at the tip, and the apex was two (5A), the apex was three (5B), Furthermore, there were those having four or more vertices (not shown). The shape of the unimodal microprotrusions 5 can be approximated by a round shape at the top like a paraboloid of revolution or a sharp shape at the apex like a cone. On the other hand, the shape of the

multimodal microprotrusions

5A and 5B is approximately approximated by a shape in which a groove-shaped recess is cut in the vicinity of the top of the single-peak microprotrusion 5 and the top is divided into a plurality of peaks. The shape of the multi-peak microprotrusions 5A and 5B, or the vertical cross-sectional shape when cutting along a virtual cut surface including a plurality of peaks and including the height direction (Z-axis direction in FIG. 15), has a plurality of maximum points. The shape is approximated by an algebraic curve Z = a ₂ X ² + a ₄ X ⁴ +... + A _2n X ²ⁿ +.

In such multi-peak microprojections having a plurality of vertices, the thickness of the skirt portion relative to the size in the vicinity of the vertices is relatively thicker than that of the single-peak microprojections. Thereby, it can be said that the multimodal microprotrusions are superior in mechanical strength to the single-peak microprotrusions. As a result, when there are multi-modal microprotrusions having a plurality of vertices, it is considered that the anti-reflective article has improved scratch resistance as compared to the case of using only monomodal micro-protrusions. Furthermore, when external force is applied to the anti-reflective article specifically, compared to the case of only a single-peaked microprojection, the external force is distributed and received at more vertices, so the external force applied to each vertex is reduced. The microprotrusions can be made difficult to be damaged, thereby reducing the local deterioration of the antireflection function and further reducing the appearance defects. Moreover, even if a microprotrusion is damaged, the area of the damaged portion can be reduced. Furthermore, about half of the multi-peak microprojections have the highest peak height (the height of the highest peak belonging to the same microprojection in the ridge) in the microprojections whose average height _{HAVG is} higher than the projection height, First, each peak portion is received and sacrificially damaged, thereby preventing wear of the main body portion lower than the peak of the microprojection and the microprojection having a height lower than that of the multi-peak microprojection. This also reduces local deterioration of the antireflection function and further reduces the occurrence of appearance defects.

2 to 6 described above are the measurement results of the antireflection article according to the present embodiment. In the frequency distribution shown in FIG. 5, the distance d between adjacent protrusions (value on the horizontal axis) is There are two types of local maxima, short maxima of 20 nm and 40 nm and long maxima of 120 nm and 164 nm. Among these maximum values, the maximum value of the long distance corresponds to the arrangement of the microprojection bodies (the part from the middle to the heel below the top part), while the maximum value of the short distance exists in the vicinity of the top part. Corresponds to the apex (peak) of. As a result, the presence of multimodal microprotrusions can also be seen from the frequency distribution of the distance between the maximal points.

Needless to say, although the multimodal microprotrusions can improve the scratch resistance due to their presence, if they do not exist sufficiently, the effect of improving the scratch resistance cannot be fully exhibited. From such a viewpoint, in the present invention, the ratio of the number of multimodal microprotrusions in all the microprotrusions existing on the surface is 10% or more. In particular, in order to sufficiently exhibit the effect of improving the scratch resistance by the multimodal microprojections, the ratio of the multimodal microprojections is set to 30% or more, preferably 50% or more. Further, since the difficulty of managing the manufacturing process increases as the ratio of the multimodal microprotrusions increases, the ratio is preferably 90% or less, more preferably 80% or less.

Further, in the antireflection article having the microprotrusion group (5, 5A, 5B,...) Including the

multimodal microprotrusions

5A and 5B, the microprotrusions whose height is controlled are formed as described above. In addition, fine protrusions having different heights are distributed. Here, as described above, the height of each microprotrusion is the height of the peak (highest peak) having the highest height at the top of a specific microprotrusion that shares the ridge (root). To tell. In the case of a single-peak microprojection such as the microprojection 5 in FIG. 15A, the height of the only peak (maximum point) at the top is the projection height of the microprojection. Further, in the case of multi-peak microprotrusions such as the

microprotrusions

5A and 5B in FIG. 15A, the height of the microprotrusions has the height of the highest peak among a plurality of peaks sharing the ridge at the top. Say it. Moreover, when all the peaks which share a collar part are the same height, let it be the height of this microprotrusion with the same height. In this way, when the heights of the microprojections are variously different, for example, even when the shape of the microprojections having a high height is damaged by contact with an object, the shape is maintained in the microprojections having a low height. It will be. Also in this case, in the antireflection article, local deterioration of the antireflection function can be reduced, and furthermore, occurrence of defective appearance can be reduced, and as a result, scratch resistance can be improved.

Further, when dust adheres between the microprojection group on the surface of the antireflection article and the object, when the article slides relative to the antireflection article, the dust functions as an abrasive to form microprojections ( Group) wear and damage are promoted. In this case, if there is a difference in height between the microprojections constituting the microprojection group, the dust strongly contacts the microprojections having a high height and is damaged. On the other hand, the contact with the low-height microprotrusions is weakened, and damage to the low-height microprotrusions is reduced, and the antireflection performance is maintained by the low-height microprotrusions that remain intact or light.

In addition to this, the microprotrusion group with distribution (height difference) in the height of each microprotrusion has a broad antireflection performance and has light with multiple wavelengths such as white light or a broadband spectrum. For light, it is advantageous to realize a low reflectance in the entire spectral band. This is because the wavelength band in which good antireflection performance can be exhibited by such a microprojection group depends not only on the distance d between adjacent projections but also on the projection height.

Further, in this case, only the high microprojections out of the many microprojections come into contact with the surface of various members arranged to face the antireflection article 1, for example. Thereby, it is possible to remarkably improve the slip as compared with the case where only the minute protrusions having the same height are used, and it is possible to easily handle the antireflection article in the manufacturing process or the like. From the viewpoint of improving the slip as described above, the variation needs to be 10 nm or more when defined by the standard deviation. However, when the variation is larger than 50 nm, the surface becomes rough. Therefore, the height variation is preferably 10 nm or more and 50 nm or less.

In addition, when multi-peak microprojections coexist in this way, the antireflection performance can be improved as compared with the case of using only single-peak microprojections. That is, the

multimodal microprotrusions

5A, 5B, etc. as shown in FIG. 2, FIG. 15, FIG. 16, etc., even when the distance between adjacent protrusions is the same or when the protrusion height is the same, Compared with a single-peak microprojection, the reflectance of light is further reduced. The reason for this is that the

multimodal microprotrusions

5A, 5B, etc. have a smaller change rate in the height direction of the effective refractive index in the vicinity of the apex than the single-peak microprotrusions below the apex (in the middle and the heel). It is to become.

That is, in FIG. 15, assuming that z = 0 is set to height H = 0, and it is assumed that the

minute protrusions

5, 5 </ b> A, etc. are cut at a virtual cutting plane Z = z orthogonal to the height direction (Z-axis direction). The effective refractive index n _ef obtained as an average value of the refractive indexes of the microprojections on the surface Z = z and the surrounding medium (usually air) is the refraction of the surrounding medium (here, air) on the cut surface Z = z. The refractive index of the constituent material of n _A = 1, the

minute protrusions

5, 5A,... Is n _M > 1, and the total value of the sectional area of the peripheral medium (air) is S _A (z). When the total value of the cross-sectional areas of 5A,... Is S _M (z),
n _ef (z) = 1 × S _A (z) / (S _A (z) + S _M (z)) + n _A × S _M (z) / (S _A (z) + S _M (z)) (Formula 1 )
It is represented by This is because the refractive index n _A of the peripheral medium and the refractive index n _M of the constituent material of the microprojections are respectively expressed as a total sectional area S _A (z) of the peripheral medium and a total value S _M (z) of the total sectional area of the microprojections. The value is proportionally distributed by the ratio of.

Here, when considered on the basis of the single-peak microprotrusions 5, the multi-peak microprotrusions 5A, 5B,... Are split into a plurality of peaks near the top. Therefore, in the virtual cutting plane Z = z that cuts the vicinity of the apex, the

multimodal microprotrusions

5A, 5B,... Have a lower refractive index than the single-peak microprotrusions 5,. The ratio of the total cross-sectional area S _A (z) of the medium is further increased as compared with the ratio of the total cross-sectional area S _M (z) of the microprojections having a relatively high refractive index.

As a result, the effective refractive index n _ef (z) at the virtual cut surface Z = z is more peripheral in the

multimodal microprotrusions

5A, 5B,. It becomes close to the refractive index n _{A of the} medium. The difference between the refractive index of the effective refractive index and the surrounding medium multimodal microprotrusions in the plane _{_{Z = z | n ef (z}} ) -n A (z) | multi, effective refractive index and surrounding unimodal microprojection When _{mono, |} a difference between the refractive index of the medium _{_{| n ef (z) -n a}} (z)
| N _ef (z) −n _A (z) | _multi <| n _ef (z) −n _A (z) | _mono (Expression 2)
It becomes. Here, if n _A (z) = 1,
| N _ef (z) -1 | _multi <| n _ef (z) -1 | _mono (Formula 2A)
It becomes.

As a result, in the vicinity of the top portion, the effective refractive index and the peripheral area of the microprojection group including the multimodal microprojections (including the peripheral medium between the microprojections) is smaller than that of the projection group including only the single-peak microprojections. The difference from the refractive index of the medium (air), more specifically, the rate of change of the refractive index per unit distance in the height direction of the microprojections is further reduced, in other words, the direction of the refractive index in the height direction. It can be seen that the continuity of change can be further increased.

In general, when light is incident on an interface between an adjacent medium having a refractive index n _{0 and} a medium having a refractive index n ₁ , the reflectance R of the light at the interface is set as an incident angle = 0.
R = (n ₁ −n ₀ ) ² / (n ₁ + n ₀ ) ² (Formula 3)
It becomes. From this formula, the smaller the refractive index difference n ₁ -n ₀ between the media on both sides of the interface, the smaller the reflectivity R of the light at the interface, and when (n ₁ -n ₀ ) approaches 0, R also approaches 0. It will be.

From (Formula 2), (Formula 2A), and (Formula 3), for the microprojection group including the

multimodal microprotrusions

5A, 5B,. The light reflectance is reduced as compared with the projection group consisting only of the projections 5.

Even if a microprojection group consisting of only the single-peak microprojections 5 is used, it is sufficient to make the maximum value dmax of the distance between adjacent projections sufficiently small below the shortest wavelength λmin of the wavelength band of the electromagnetic wave for preventing reflection. It is possible to exhibit an excellent antireflection effect. However, in this case, since the distance between adjacent peaks and the distance between adjacent minute protrusions are the same, a phenomenon (so-called sticking) in which adjacent minute protrusions are brought into contact with each other and integrated together is likely to occur. When sticking occurs, the substantial distance d between adjacent protrusions increases by the number of minute protrusions integrated together.

For example, when four microprojections with d = 200 nm are stuck, the size of the stuck and integrated projection is substantially d = 4 × 200 nm = 800 nm> the longest wavelength in the visible light band (780 nm). The antireflection effect is locally impaired.

On the other hand, in the case of a microprotrusion group consisting of

multimodal microprotrusions

5A, 5B,..., The distance between adjacent protrusions d ^PEAK between each peak near the top is the distance between adjacent protrusions of the microprotrusion main body from the heel to the middle. It becomes smaller than d _BASE (d ^PEAK <d _BASE ), and is usually about d ^PEAK = d _BASE / 4 to d _BASE / 2. Therefore, sufficient antireflection performance can be obtained by setting the distance d ^PEAK << λmin between adjacent protrusions between the peaks. However, each peak of the multi-peak microprojection has a small ratio of the height of the peak to the width of the buttocks, which is 1/2 to the ratio of the height of the apex to the width of the buttocks of the single-peak microprojection. It is about 1/10. Therefore, for the same external force, the peak of the multimodal microprotrusions is less likely to deform than the single-peak microprotrusions. In addition, the main body itself of the multimodal microprotrusions has a greater distance between adjacent protrusions and a greater strength than the ridges. Therefore, after all, the microprojection group composed of multimodal microprotrusions can easily achieve both stickiness and low reflectivity compared to the projection group composed of monomodal microprojections.

In addition, even if it is other uses for antireflection of visible light, or under a visible light environment, the antireflection material depends on the assumed antireflection wavelength depending on the environmental conditions where the antireflection material is installed and used. By forming a moth-eye structure and having a height distribution, as described above, even when using materials that are more resistant to abrasion than conventional products and have low hardness due to process requirements, etc., prevent sticking to each other In addition, it is possible to produce an antireflection material having both optically required performance. For example, when it is desired to obtain antireflection performance in the ultraviolet region around 380 nm, the height of the moth eye can be about 50 n. Similarly, the infrared region around 700 nm is about 150 nm to 400 nm in consideration of practical use. Is possible. As described above, it is possible to find manufacturing conditions that saturate the height of the arrangement pitch of the moth-eye, and to effectively control the reflectance of the moth-eye. In addition, the top structure of the moth-eye can be improved from the conventional single peak to achieve both height and reflectivity, and it is difficult to cause physical sticking and can effectively reduce reflectivity. Yes.

FIG. 16 is a photograph showing a plurality of minute protrusions at the apex, and FIG. 16 is an example of a minute protrusion different from that of the embodiment, but FIG. 16A is based on AFM, and FIG. (B) and (c) are by SEM. In FIG. 16 (a), a groove g and a microprotrusion having three vertices and a microprotrusion having a groove g and two vertices can be seen, and in FIG. 16 (b), the groove g and four vertices are present. A microprotrusion and a microprotrusion having a groove g and two vertices can be seen, and in FIG. 16C, a microprotrusion having a groove g and three vertices, a microprotrusion having a groove g and two vertices can be seen. be able to. In FIG. 16, an aqueous oxalic acid solution having a water temperature of 20 ° C. and a concentration of 0.02 M is applied, and an anodizing process is executed for 120 seconds with an applied voltage of 40V. In the etching process, an anodic oxidation solution was applied to the first step, and an aqueous phosphoric acid solution having a water temperature of 20 ° C. and a concentration of 1.0 M was applied to the second step. The number of times of anodizing treatment and etching treatment is 3 (~ 5) times.

16 and 17 are a perspective view (FIG. 16), a plan view (FIG. 17 (a)), a front view (FIG. 17 (b)), and a side view (FIG. 17 (c)). These FIG.16 and FIG.17 is a contour map. As described above, by switching the applied voltage in a plurality of anodic oxidation treatments, in the microprotrusions according to FIGS. 16 and 17, three peaks having greatly different heights are combined to form one microprotrusion. It can be seen that microprojections are produced by dividing the region into three peak areas by three radial grooves (swelled local minimum portions) formed outward from the center. FIG. 16 and FIG. 17 show data in detail by partially selecting data based on measurement results by AFM. The unit of the numbers in FIGS. 16 and 17 is nm. The X coordinate and the Y coordinate are coordinate values from a predetermined reference position.

FIGS. 18 and 19 are diagrams showing other measurement results of the microprotrusions in the present embodiment in comparison with FIGS. 16 and 17. In the microprotrusions of FIGS. 18 and 19, three ridges having substantially the same height are combined to form one microprotrusion, and the three ridges extend outward from the substantially central portion of the top. It can be seen that it is divided by three radial grooves.

20 and 21 are diagrams showing the measurement results of other microprotrusions in the same embodiment in the same manner as in comparison with FIGS. 16 to 19. 20 and FIG. 21 is formed in a shape as if a plurality of microprojections arranged in a row horizontally are combined, and the aspect ratio between the arrangement direction and the direction orthogonal to the arrangement direction is the same. Created differently. In the antireflection article by the fine protrusions having different aspect ratios depending on the direction, the antireflection characteristic can be given directionality. In this microprotrusion, the grooves between the peaks extend in a direction perpendicular to the alignment direction.

In addition, according to the results observed in this manner, the roughness of the surface is observed to be rougher than the outer side of each peak, and the inner side and the outer side of the peak are thus observed. Due to the difference in roughness, it is possible to see the difference from the multimodal microprotrusions caused by poor filling of the resin during the shaping process. In these perspective views and the like, portions where no contour lines are represented are portions where data is not obtained for convenience of measurement.

[Evaluation of scratch resistance]
Table 1 shows the evaluation results of the scratch resistance. The antireflective article according to the example of FIGS. 13 and 14 was compared with an antireflective article having a similar protrusion height distribution using only single-peaked microprotrusions. In addition, the anti-reflective article only of the single peak microprotrusion produced the applied voltage of the repetition anodizing process as the same constant voltage as the 1st process also after the 2nd process. In addition, an antireflection article having a bimodal characteristic distribution using only unimodal microprotrusions was produced by executing an applied voltage of repeated anodizing treatment by switching between two stages.

In Table 1, the column of steel wool is the result of visually confirming the change in the surface after the steel wool was pressed and reciprocated with a pressing force of 100 g and 200 g. The double circle mark was evaluated to be visually invisible and no turbidity was observed, and the triangle mark was visually visible to 1 to 5 scratches. In the case of x, six or more scratches are observed visually. The evaluation range is a rectangular area with a side of 5 cm. It can be seen that the scratch resistance is sufficiently improved by the multimodal microprotrusions.

Also, the column of dry wiping shows 5 ° regular reflectance (ΔY (%)) when fingerprints are attached and then wiped 50 times in a dry state containing no solvent using a nonwoven fabric. With the fingerprint attached, the 5 ° regular reflectance was set to 4%. As the nonwoven fabric, Savina Minimax (registered trademark) 150 mm □ manufactured by KB Seiren Co., Ltd. was used. In addition, the initial value of the 5 ° regular reflectance in a state where no dirt due to fingerprints was attached was 0.5%. According to the results of this study, it was found that the dirt attached by the multimodal microprotrusions was easily wiped off, and the antireflection performance was restored to a state close to that before the fingerprint attachment. In the case where it is provided, it is considered that the dirt does not penetrate deeply into the base side of the minute protrusion.

According to the above configuration, the scratch resistance can be improved as compared with the prior art by mixing a multi-peak microprojection having a plurality of vertices and a single-peak microprojection having one vertex. In addition, the stain resistance (easy wiping property) against fingerprints is also improved.

Furthermore, the slipperiness can be improved by giving a distribution to the heights of the microprojections.

[Other Embodiments]
The specific configuration suitable for the implementation of the present invention has been described in detail above. However, the present invention can be variously modified from the configuration of the above-described embodiment without departing from the spirit of the present invention, and further the conventional configuration. Can be combined.

That is, in the above-described embodiment, the case where the number of repetitions of the anodizing process and the etching process is set to 3 (to 5) each is described. However, the present invention is not limited to this, and the number of repetitions is set to other numbers. In addition, the present invention can be widely applied to the case where the process is repeated a plurality of times and the final process is anodizing.

Further, in the above-described embodiment, the case where the antireflection article is arranged on the front side surface of various image display panels such as a liquid crystal display panel, an electroluminescent display panel, a plasma display panel, and the like is described, but the present invention is described. However, the present invention is not limited to this. For example, it can be widely applied to a case where the reflection loss of incident light from the backlight to the liquid crystal display panel is reduced by reducing the reflection loss of incident light from the backlight (increasing incident light utilization efficiency). it can. Here, the surface side of the image display panel is a light output surface of the image display panel and also a surface on the image observer side. The back side of the image display panel is the opposite side of the surface of the image display panel. In the case of a transmissive image display apparatus using a backlight (back light source), the incident light from the backlight is incident. It is also a surface.

In the above-described embodiment, the case where an acrylate-based ultraviolet curable resin is applied to the shaping resin has been described. However, the present invention is not limited thereto, and various ultraviolet curable resins such as epoxy-based and polyester-based resins, or Also when using various materials such as acrylate-based, epoxy-based, polyester-based electron beam curable resins, urethane-based, epoxy-based, polysiloxane-based thermosetting resins, and various types of curing resins The present invention can be widely applied. Further, for example, the present invention can also be widely applied in the case of molding by pressing a thermoplastic resin such as a heated acrylic resin, polycarbonate resin, or polystyrene resin.

Further, in the above-described embodiment, as shown in FIG. 1, microprojections are formed on the receiving layer 4 of the laminate formed by laminating the receiving layer (ultraviolet curable resin layer) 4 on one surface of the substrate 2. The

groups

5, 5A, 5B,... Are shaped and the receiving layer 4 is cured to form the antireflection article 1. The layer structure is a two-layer laminate. However, the present invention is not limited to such a form. Although not shown, the antireflection article 1 of the present invention is a single layer in which the

microprojections

5, 5A, 5B,... Are directly formed on one surface of the substrate 2 without interposing another layer. It may be a configuration. Alternatively, one or more intermediate layers on one surface of the substrate 2 (layers that improve substrate surface performance such as interlayer adhesion, coating suitability, surface smoothness, etc. Also referred to as primer layer, anchor layer, etc. .) May be formed, and a laminate of three or more layers in which the

microprotrusions

5, 5A, 5B,... Are formed on the surface of the receptor layer may be used.

Further, in the above-described embodiment, as shown in FIG. 1, the

microprojections

5, 5A, 5B,... Are formed only on one surface of the base material 2 (directly or via another layer). However, the present invention is not limited to such a form. The

microprojection groups

5, 5A, 5B,... May be formed on both surfaces of the substrate 2 (directly or via other layers). In the case of the form having the

microprojection groups

5, 5A, 5B,... On both surfaces of the substrate 2, the antireflection performance is larger than the form in which the microprojection group is provided only on one surface. improves. For example, when the reflectance of light at the interface between air and the substrate 2 itself is 4% and the reflectance of light at the interface between the minute protrusions and the air is 0.2%, The total reflectance of the front and back surfaces with respect to light transmitted from the front (or back) surface to the back (or front) surface of 2 is the reflectance at the interface between the layer having the fine protrusion group (receiving layer 4) and the substrate 2 Assuming that the contribution of is 0%,
(1) 8% when there are no microprojections on both sides of the substrate.
(2) 4.2% when the microprojection group is provided only on one surface of the substrate.
(3) 0.4% in the case of having microprojections on both the front and back surfaces of the substrate.
It becomes.
Although not shown, in the antireflection article 1 of the present invention as shown in FIG. 1 and the like, the surface opposite to the surface on which the microprojections are formed of the substrate 2 (the lower surface of the substrate 2 in FIG. 1). Various adhesive layers are formed on the adhesive layer, and a release film (release paper) is laminated on the surface of the adhesive layer so as to be peelable. In such a form, the release film is peeled and removed to expose the adhesive layer, and the antireflection article 1 of the present invention can be laminated and laminated on the desired surface of the desired article by the adhesive layer. The antireflection performance can be easily imparted to a desired article. As the adhesive, various types of known adhesive forms such as a pressure-sensitive adhesive (pressure-sensitive adhesive), a two-component curable adhesive, an ultraviolet curable adhesive, a thermosetting adhesive, and a hot melt adhesive can be used. .

Although not shown, in the antireflection article 1 of the present invention as shown in FIG. 1 etc., the

microprojections

5, 5 A, 5 B,... The protective film may be peeled and removed at an appropriate time after carrying, carrying, buying and selling, post-processing or construction. In such a form, it is possible to prevent the antireflection performance from being deteriorated due to damage or contamination of the microprojection group during storage, transportation and the like.

Further, in the above-described embodiment, as shown in FIGS. 1 and 15A, the surface connecting the valley bottoms (minimum points of height) between the adjacent minute protrusions is a flat surface having a constant height. However, the present invention is not limited to this, and as shown in FIG. 23, the envelope surface connecting the valley bottoms between the microprojections has a period D (that is, D> λmax) that is equal to or longer than the longest wavelength λmax of the visible light band. It is good also as a structure. The periodic undulation is constant in only one direction (for example, the X direction) on the XY plane (see FIGS. 15 and 23) parallel to the front and back surfaces of the substrate 2 and in a direction orthogonal to the direction (for example, the Y direction). The height may be sufficient, or the two directions (X direction and Y direction) in the XY plane may have undulations. The uneven surface 6 that undulates with a period D satisfying D> λmax is superimposed on a microprojection group composed of a large number of microprojections, so that the reflected light remaining without being completely prevented from being reflected by the microprojection group is scattered, so that Reflected light, particularly specularly reflected light, can be made more difficult to visually recognize, and the antireflection effect can be further improved.

In addition, when the period D of the uneven surface 6 is not constant over the entire surface and has a distribution, the frequency distribution of the distance between the protrusions is obtained for the uneven surface, and the average value is D _AVG and the standard deviation is Σ. When
D _MIN = D _AVG -2Σ
Designed as an alternative to period D with a minimum inter-protrusion distance defined as That is, conditions that can sufficiently exhibit the scattering effect of the reflected light of the microprojections are as follows:
D _MIN > λmax
Also, the Rz value (10-point average roughness) defined in JIS B0601 (1994) corresponding to the height difference of the unevenness is
Rz ≧ λmin
It is. Usually, D or D _MIN is 1 to 600 μm, preferably 10 to 300 μm. Usually, Rz is 0.4 to 5 μm.
An example of a specific manufacturing method for forming a concavo-convex microprojection group having an uneven surface 6 in which the envelope surface connecting the valley bottoms of each microprojection is D (or D _MIN )> λmax is as follows. is there. That is, in the manufacturing process of the roll plate 13, a concavo-convex shape corresponding to the concavo-convex shape of the concavo-convex surface 6 is formed on the surface of a cylindrical (or columnar) base material by sandblasting or mat (matte) plating. Next, an appropriate intermediate layer is formed directly or if necessary on the uneven surface, and then an aluminum layer is laminated. Thereafter, an aluminum layer formed with a surface shape corresponding to the uneven surface is subjected to anodizing treatment and etching treatment in the same manner as in the above embodiment to form a microprojection

group including microprojections

5, 5A, 5B. To do.

In the above-described embodiment, the case where the mold for the shaping process is manufactured by repeating the anodizing process and the etching process has been described. However, the present invention is not limited to this, and the photolithography technique is applied. The present invention can also be widely applied to molds for mold processing.

Moreover, although the above-mentioned embodiment described the case where the anti-reflective article by a film shape was produced by the shaping process using a roll plate, this invention is not limited to this, The transparent base material which concerns on the shape of an anti-reflective article Depending on the shape, for example, when creating an antireflection article by processing a sheet using a shaping mold with a specific curved shape, such as a flat plate, the process related to the shaping process, the mold is the antireflection article It can change suitably according to the shape of the transparent base material which concerns on a shape.

In the above-described embodiment, the case where the antireflection article with the film shape is arranged on the front side surface of the image display panel or the incident surface of the illumination light has been described. However, the present invention is not limited to this and is applied to various applications. be able to. Specifically, it should be applied to applications that are placed on the back surface (image display panel side) of the surface side member such as a touch panel, various window materials, various optical filters, etc. installed on the screen of the image display panel through a gap. Can do. In this case, it is possible to prevent interference fringes such as Newton rings due to light interference between the image display panel and the surface side member, and between the light emission surface of the image display panel and the light incident surface side of the surface side member. Thus, it is possible to prevent ghost images due to multiple reflections, and to achieve effects such as reduction of reflection loss with respect to image light emitted from the screen and entering these surface side members.

Alternatively, a transparent electrode constituting the touch panel is formed on a film or plate-like transparent substrate with a group of microprojections specific to the present invention, and a transparent conductive film such as ITO (indium tin oxide) is further formed on the group of microprojections. The formed one can be used. In this case, it is possible to prevent light reflection between the touch panel electrode and the counter electrode or various members adjacent to the touch panel electrode, thereby reducing the occurrence of interference fringes, ghost images, and the like.

In addition, it is arranged on the glass plate surface (external side) used for the store show window and product display box of the store, the display window and display box of the exhibition of the museum, or both of the front and back surfaces (product or display side). May be. In this case, it is possible to improve the visibility for customers and spectators of products, artworks, etc. by preventing light reflection on the surface of the glass plate.

Also, it can be widely applied to the case where it is arranged on the surface of a lens or prism used in various optical devices such as glasses, a telescope, a camera, a video camera, a gun sighting mirror (sniper scope), binoculars, a periscope. In this case, the visibility by preventing light reflection on the lens or prism surface can be improved. Furthermore, it can also be applied to the case where it is arranged on the surface of a printed part (characters, photos, drawings, etc.) of a book to prevent light reflection on the surface of characters and the like and improve the visibility of characters and the like. In addition, it should be placed on the surface of signs (posters, posters, various other stores, streets, exterior walls, etc.) (road guidance, maps, smoking cessation, entrances, emergency exits, no entry, etc.) to improve visibility. Can do. In addition, a light entrance surface of a window material for a lighting fixture using incandescent bulbs, light emitting diodes, fluorescent lamps, mercury lamps, EL (electroluminescence), etc. (in some cases, it also serves as a diffuser plate, condenser lens, optical filter, etc.) By arranging it on the side, it is possible to prevent the light reflection of the light incident surface of the window material, reduce the reflection loss of the light source light, and improve the light utilization efficiency. Furthermore, it can arrange | position on the display window surface (display observer side) of a timepiece and other various measuring devices, the light reflection of these display window surfaces can be prevented, and visibility can be improved.

Furthermore, it is placed on the inside, outside, or both sides of the windows of the cockpits (driver's cabs, wheelhouses) of vehicles such as automobiles, railway vehicles, ships, and aircraft to prevent reflection of indoor and outdoor light from the windows. Thus, it is possible to improve the visibility of the outside world of the driver (driver, driver). Furthermore, it can be arranged on the surface of a night vision device lens or window material used for crime prevention monitoring, gun sighting, astronomical observation, etc. to improve visibility at night and in the dark.

Furthermore, the surface of the transparent substrate (window glass, etc.) that constitutes windows, doors, partitions, wall surfaces, etc. of buildings such as houses, stores, offices, schools, hospitals, etc. (inside, outside, or both sides) It is possible to improve the visibility of the outside world or the daylighting efficiency. Furthermore, it stores products or exhibits used in various stores, museums, museums, etc., and arranges them on the front, back, or both sides of the transparent window (or door) of various display boxes or showcases to be displayed, It is possible to improve the visibility of products to be displayed or exhibits. Furthermore, it can arrange | position on the surface of a greenhouse, the transparent sheet | seat of an agricultural greenhouse, or a transparent board (window material), and can improve the sunlight lighting efficiency. Furthermore, it can arrange | position on the solar cell surface and can improve the utilization efficiency (power generation efficiency) of sunlight.

Furthermore, in the above-described embodiment, the wavelength band of the electromagnetic wave for preventing reflection is exclusively the visible light band (all or part of the visible light band), but the present invention is not limited to this, and the electromagnetic wave for preventing reflection. May be set to a wavelength band other than visible light rays such as infrared rays and ultraviolet rays. In that case, the shortest wavelength Λmin in the wavelength band of the electromagnetic wave may be set to the shortest wavelength in which the antireflection effect in the wavelength band of infrared rays, ultraviolet rays, etc. is desired in each conditional expression. For example, when it is desired to prevent reflection in the infrared band where the shortest wavelength Λmin is 850 nm, the distance d between adjacent protrusions (or its maximum value dmax) may be designed to be 850 nm or less, for example, d (dmax) = 800 nm. . In this case, an antireflection effect cannot be expected in the visible light band (380 to 780 nm), and an antireflection article exhibiting an antireflection effect for infrared rays having a wavelength of 850 nm or more can be obtained.

In the various exemplary embodiments described above, when the film-shaped antireflection article of the present invention is disposed on the front surface, back surface, or both front and back surfaces of a transparent substrate such as a glass plate, it is disposed and covered over the entire surface of the transparent substrate. In addition, it can be arranged only in a partial area. As an example of this, for example, for a single window glass, a film-shaped antireflection article is attached to the indoor side surface only with an adhesive in a square area at the center, and an antireflection article is provided in the other areas. The case where it does not stick can be mentioned. In the case where the antireflection article is arranged only in a partial area of the transparent substrate, it is easy to visually recognize the presence of the transparent substrate without special display or a collision prevention fence, etc. The effect of reducing the risk of collision and injury, and the effect that both the prevention of peeping indoors (indoors) and the transparency of the transparent substrate (in the region where the antireflection article is disposed) can be achieved.

DESCRIPTION OF SYMBOLS 1 Anti-reflective article 2 Base material 4 Ultraviolet curable resin layer, receiving

layer

5, 5A, 5B Minute protrusion 6 Uneven surface 10 Manufacturing process 12 Die 13

Roll plate

14, 15 Roller g Groove

Claims

In the antireflection article in which the microprotrusions are closely arranged and the interval between the adjacent microprotrusions is equal to or less than the shortest wavelength of the wavelength band of the electromagnetic wave to prevent reflection,
The microprotrusions are composed of a plurality of multimodal microprojections having a plurality of vertices and a unimodal microprojection having one apex,
The average value of the height H in the frequency distribution of the height H of the microprotrusions is m, the standard deviation is σ,
The region where H <m−σ is the low altitude region,
The region of m−σ ≦ H ≦ m + σ is defined as the middle altitude region,
When the region of m + σ <H is a high altitude region,
The ratio between the number Nm of the multi-peaked microprojections in each region and the total number Nt of the microprojections in the entire frequency distribution is as follows:
Nm / Nt in middle altitude region> Nm / Nt in low altitude region,
Satisfying the relationship of Nm / Nt in the middle altitude region> Nm / Nt in the high altitude region,
An antireflection article characterized by
The frequency distribution of the height H of the microprotrusions is bimodal due to two distributions, where Hs is the height that becomes the boundary between the two distributions, and the average value of the heights H of the microprotrusions in a distribution less than Hs. m1,
The region of H <m1-σ1 is defined as a low altitude region,
The region of m1−σ1 ≦ H ≦ m1 + σ1 is defined as a medium altitude region,
When the region of m1 + σ1 <H <Hs is a high altitude region,
The ratio between the number Nm1 of the multi-modal microprojections in each region in the distribution of less than Hs and the total number Nt of microprojections in the entire frequency distribution is:
Nm1 / Nt in the middle altitude region> Nm1 / Nt in the low altitude region,
Satisfying the relationship of Nm1 / Nt in the middle altitude region> Nm1 / Nt in the high altitude region,
In the distribution of Hs or more, the average value of the height H of the microprojections is m2, the standard deviation is σ2,
The region where Hs <H <m2-σ2 is set as the low altitude region,
The region of m2−σ2 ≦ H ≦ m2 + σ2 is defined as a medium altitude region,
When the area of m2 + σ2 <H is a high altitude area,
The ratio between the number Nm2 of the multi-modal microprojections in each region in the distribution of Hs or higher and the total number Nt of the microprojections in the entire frequency distribution is as follows:
Nm2 / Nt in the middle altitude region> Nm2 / Nt in the low altitude region,
Satisfying the relationship of Nm2 / Nt in the middle altitude region> Nm2 / Nt in the high altitude region,
The antireflection article according to claim 1.
An image display device in which the antireflection article according to claim 1 or 2 is disposed on a light exit surface of an image display panel.
A mold for manufacturing an antireflective article for use in manufacturing an antireflective article,
The antireflective article is
The microprotrusions are closely placed,
The interval between the adjacent minute protrusions is equal to or less than the shortest wavelength of the wavelength band of the electromagnetic wave for preventing reflection,
The microprotrusions are composed of multi-peak microprojections having a plurality of vertices and a single unimodal microprojection having a single vertex,
The average value of the height H in the frequency distribution of the height H of the microprotrusions is m, the standard deviation is σ,
The region where H <m−σ is the low altitude region,
The region of m−σ ≦ H ≦ m + σ is defined as the middle altitude region,
When the region of m + σ <H is a high altitude region,
The ratio between the number Nm of the multi-peaked microprojections in each region and the total number Nt of the microprojections in the entire frequency distribution is as follows:
Nm / Nt in middle altitude region> Nm / Nt in low altitude region,
Satisfying the relationship of Nm / Nt in the middle altitude region> Nm / Nt in the high altitude region,
The mold for manufacturing the antireflection article is:
The minute holes corresponding to the minute protrusions are made closely,
A mold for manufacturing an antireflective article.
A method of manufacturing a mold for manufacturing an antireflective article for manufacturing a mold for manufacturing an antireflective article according to claim 4,
A flat micro-hole forming step of performing an etching process after applying the first voltage and performing an anodizing process to form a micro-hole having a substantially flat bottom surface on the surface of the plate;
An anodizing process is performed after applying a second voltage lower than the first voltage, and then an etching process is performed to form a plurality of micro holes on the bottom surface of the micro hole having a substantially flat bottom surface. Micro-hole forming process for multimodal protrusions,
A method of manufacturing a mold for manufacturing an antireflection article comprising: