WO2016084745A1

WO2016084745A1 - Mold, method for manufacturing mold, and antireflective film

Info

Publication number: WO2016084745A1
Application number: PCT/JP2015/082735
Authority: WO
Inventors: 隆裕中原; 美穂山田; 箕浦　潔
Original assignee: シャープ株式会社
Priority date: 2014-11-25
Filing date: 2015-11-20
Publication date: 2016-06-02
Also published as: JPWO2016084745A1; JP6458051B2

Abstract

This antireflective film (32A) has a plurality of first protrusions (32a) which, viewed from the direction of the normal line of the surface, has a two-dimensional size of 50 nm to less than 300 nm, and a height of 50-300 nm. The plurality of first protrusions (32a) include a plurality of ring-shaped protrusion groups in each of which a plurality of the first protrusions (32a) are arrayed in a ring shape at interproximal distances of 50 nm to less than 300 nm. A plurality of areas respectively enclosed by the plurality of ring-shaped protrusion groups include a plurality of first regions (R1) in which the average value of the major axis and the minor axis is more than 300 nm but not more than 800 nm.

Description

Mold, mold manufacturing method and antireflection film

The present invention relates to a mold, a method for manufacturing the mold, and an antireflection film. The “mold” here includes molds used in various processing methods (stamping and casting), and is sometimes referred to as a stamper. It can also be used for printing (including nanoprinting).

2. Description of the Related Art An optical element such as a display device or a camera lens used for a television or a mobile phone is usually provided with an antireflection technique in order to reduce surface reflection and increase light transmission. For example, when light passes through the interface of a medium with a different refractive index, such as when light enters the interface between air and glass, the amount of transmitted light is reduced due to Fresnel reflection, etc., and visibility is reduced. is there.

In recent years, attention has been paid to a method of forming a fine uneven pattern on the substrate surface, in which the period of the unevenness is controlled to a wavelength of visible light (λ = 380 nm to 780 nm) or less as an antireflection technique (see Patent Documents 1 to 4). reference). The two-dimensional size of the convex portions constituting the concavo-convex pattern expressing the antireflection function is 10 nm or more and less than 500 nm.

This method utilizes the principle of a so-called moth-eye structure, and the refractive index for light incident on the substrate is determined from the refractive index of the incident medium along the depth direction of the irregularities. By continuously changing the refractive index, the reflection in the wavelength region to be prevented from being reflected is suppressed.

The moth-eye structure has an advantage that it can exhibit an antireflection effect with a small incident angle dependency over a wide wavelength range, can be applied to many materials, and can form an uneven pattern directly on a substrate. As a result, a low-cost and high-performance antireflection film (or antireflection surface) can be provided.

As a method for producing a moth-eye structure, a method using an anodized porous alumina layer obtained by anodizing aluminum has attracted attention (Patent Documents 2 to 4).

Here, the anodized porous alumina layer obtained by anodizing aluminum will be briefly described. Conventionally, a method for producing a porous structure using anodization has attracted attention as a simple method capable of forming regularly ordered nano-sized cylindrical pores (fine concave portions). When a substrate is immersed in an acidic or alkaline electrolyte such as sulfuric acid, oxalic acid, or phosphoric acid, and a voltage is applied using this as an anode, oxidation and dissolution proceed simultaneously on the surface of the substrate, and pores are formed on the surface. An oxide film having the following can be formed. These cylindrical pores are oriented perpendicular to the oxide film and exhibit self-organized regularity under certain conditions (voltage, type of electrolyte, temperature, etc.). Is expected.

The porous alumina layer formed under specific conditions takes an array in which almost regular hexagonal cells are two-dimensionally filled with the highest density when viewed from the direction perpendicular to the film surface. Each cell has a pore in the center, and the arrangement of the pores has periodicity. The cell is formed as a result of local dissolution and growth of the film, and dissolution and growth of the film proceed simultaneously at the bottom of the pores called a barrier layer. At this time, it is known that the cell size, that is, the distance between adjacent pores (center-to-center distance) corresponds to approximately twice the thickness of the barrier layer and is approximately proportional to the voltage during anodization. In addition, although the diameter of the pores depends on the type, concentration, temperature, etc. of the electrolytic solution, it is usually 1/3 of the cell size (the length of the longest diagonal line when viewed from the direction perpendicular to the film surface). It is known to be a degree. The pores of such porous alumina have an arrangement with high regularity (having periodicity) under a specific condition, an arrangement with irregularity to some extent or an irregularity (having no periodicity) depending on the conditions. ).

Patent Document 2 discloses a method of forming an antireflection film (antireflection surface) using a stamper having an anodized porous alumina film on the surface.

Further, Patent Document 3 discloses a technique for forming a tapered concave portion in which the pore diameter continuously changes by repeating aluminum anodization and pore diameter enlargement processing.

Patent Document 4 discloses a technique for forming an antireflection film using an alumina layer in which fine concave portions have stepped side surfaces.

Further, as described in

Patent Documents

1, 2, and 4, an antireflection film (antireflection surface) is provided by providing a concavo-convex structure (macro structure) larger than the moth eye structure in addition to the moth eye structure (micro structure). ) Can be given an anti-glare (anti-glare) function. The two-dimensional size of the convex portion constituting the concave and convex that exhibits the antiglare function is 1 μm or more and less than 100 μm. The entire disclosures of

Patent Documents

1, 2, and 4 are incorporated herein by reference. Here, the “two-dimensional size” of the convex portion refers to the area equivalent circle diameter of the convex portion when viewed from the normal direction of the surface. For example, when the convex portion has a conical shape, The two-dimensional size corresponds to the diameter of the bottom surface of the cone. The same applies to the “two-dimensional size” of the recess.

By using the anodized porous alumina film, a mold for forming a moth-eye structure on the surface (hereinafter referred to as “moth-eye mold”) can be easily manufactured. In particular, as described in Patent Documents 2 and 4, when the surface of an anodized aluminum film is used as it is as a mold, the effect of reducing the manufacturing cost is great. The surface structure of the moth-eye mold that can form the moth-eye structure is referred to as an “inverted moth-eye structure”.

As a method for producing an antireflection film using a moth-eye mold, a method using a photocurable resin is known. First, a photocurable resin is applied on the substrate. Subsequently, the uneven surface of the moth-eye mold subjected to the release treatment is pressed against the photocurable resin in a vacuum. Thereafter, a photocurable resin is filled into the concavo-convex structure. Subsequently, the photocurable resin in the concavo-convex structure is irradiated with ultraviolet rays to cure the photocurable resin. Thereafter, by separating the moth-eye mold from the substrate, a cured product layer of a photocurable resin to which the concavo-convex structure of the moth-eye mold is transferred is formed on the surface of the substrate. A method for producing an antireflection film using a photocurable resin is described in Patent Document 4, for example.

In the method of manufacturing a mold for manufacturing an antireflection film in which a moth-eye structure is superimposed on an anti-glare structure described in

Patent Documents

1, 2, and 4, the anti-glare structure is previously formed separately from the step of forming the inverted moth-eye structure. It is necessary to perform a step of forming a concavo-convex structure for forming. For example, in Patent Document 1, a concavo-convex structure for forming an antiglare structure is formed by mechanical means such as sand blasting or shot peening with a glass beat, in addition to the process of forming an inverted moth-eye structure. It is described to do.

JP-T-2001-517319 Special Table 2003-531962 JP 2005-156695 A International Publication No. 2006/059686 International Publication No. 2011/052652 International Publication No. 2012/137664 International Publication No. 2013/183576

Therefore, the present applicant discloses in Patent Document 5 a method for easily manufacturing a mold for manufacturing an antireflection film in which a moth-eye structure is superimposed on an antiglare structure. According to Patent Document 5, a mold suitable for producing an antireflection film having a haze value of 1% or more and 5% or less can be produced.

On the other hand, the present applicant, together with other applicants, discloses a method for producing a mold substrate having an aluminum alloy layer having high specularity in Patent Documents 6 and 7. In the present specification, the “mold substrate” refers to an object to be anodized and etched in the mold manufacturing process. When the molds described in Patent Documents 6 and 7 are used, an antireflection film having no unnecessary haze can be formed. The entire disclosure of Patent Documents 5 to 7 is incorporated herein by reference.

An object of the present invention is to provide an antireflection film having a novel structure, a mold suitably used for producing such an antireflection film, and a method for producing the mold.

An antireflection film according to an embodiment of the present invention includes a plurality of first protrusions having a two-dimensional size of 50 nm or more and less than 300 nm and a height of 50 nm or more and 300 nm or less when viewed from the normal direction of the surface. Each of the plurality of first protrusions includes a plurality of annular protrusion groups in which the plurality of first protrusions are annularly arranged at a distance between adjacent ones of 50 nm or more and less than 300 nm. The plurality of regions surrounded by each of the annular convex group includes a plurality of first regions having an average value of a major axis and a minor axis of more than 300 nm and not more than 800 nm.

In one embodiment, the plurality of first regions do not have the plurality of first protrusions.

In one embodiment, the plurality of first regions include a first region having two or more second protrusions that are smaller in height than the plurality of first protrusions.

A mold according to another embodiment of the present invention has a porous alumina layer on the surface, and the porous alumina layer has a two-dimensional size of 50 nm or more and less than 300 nm when viewed from the normal direction of the surface, A plurality of first recesses having a length of 50 nm or more and 300 nm or less, each of the plurality of first recesses having a plurality of first recesses arranged in an annular shape with an inter-adjacent distance of 50 nm or more and less than 300 nm. And a plurality of regions surrounded by each of the plurality of annular recess groups includes a plurality of first regions having an average value of a major axis and a minor axis of more than 300 nm and not more than 800 nm.

In one embodiment, the mold further includes an aluminum alloy layer under the porous alumina layer, and the aluminum alloy layer includes aluminum and titanium.

In one embodiment, the total thickness of the aluminum alloy layer and the porous alumina layer is 2 μm or more.

In one embodiment, the mold further has an inorganic underlayer under the aluminum alloy layer. The inorganic underlayer is a silicon oxide layer, a tantalum oxide layer, or a titanium oxide layer. In one embodiment, the thickness of the inorganic underlayer is preferably 50 nm or more and 300 nm or less.

The mold further includes a buffer layer between the inorganic base layer and the aluminum alloy layer, and the buffer layer includes aluminum, titanium, and oxygen or nitrogen.

A mold manufacturing method according to still another embodiment of the present invention is a method for manufacturing the mold according to any one of the above, wherein (a) an aluminum alloy layer having a thickness of 2 μm or more is formed on a substrate. (B) forming a porous alumina layer having a plurality of fine recesses by partially anodizing the aluminum alloy layer; and (c) after the step (b), the porous alumina. A step of bringing the layer into contact with an etching solution to enlarge the plurality of fine concave portions of the porous alumina layer; and (d) further anodizing after the step (c), thereby Growing a concave portion.

The electrolyte used in the step of forming the porous alumina layer is, for example, an aqueous solution containing an acid selected from the group consisting of oxalic acid, tartaric acid, phosphoric acid, chromic acid, citric acid, and malic acid. As the etching solution, for example, an aqueous solution of 10% by mass of phosphoric acid, an organic acid such as formic acid, acetic acid or citric acid, or a mixed solution of chromium phosphoric acid can be used.

According to the embodiment of the present invention, an antireflection film having a novel structure, a mold suitably used for producing such an antireflection film, and a method for manufacturing the mold are provided. According to the embodiments of the present invention, for example, an antireflection film having a haze value of 1% or more and 12% or less, a mold suitably used for producing such an antireflection film, and a method of manufacturing the mold are provided. .

(A) is a surface SEM image of the antireflection film (Example 1) according to the embodiment of the present invention, (b) is a schematic plan view showing the surface structure of the antireflection film, and (c). FIG. 4B is a schematic cross-sectional view taken along line 1C-1C ′ in FIG. (A) And (b) is a schematic diagram for demonstrating the manufacturing method of the type | mold by embodiment of this invention. (A) is a surface SEM image of a mold substrate, (b) is a surface SEM image of a moth-eye mold, and (c) is a surface SEM image of an antireflection film (Example 1). (A) to (c) are surface SEM images of the antireflection films (Examples 2 to 4) according to the embodiment of the present invention. It is a surface SEM image of the antireflection film of a comparative example. It is a SEM image of the mold base material from which the thickness of an aluminum alloy layer differs, (a) and (b) are 6 micrometers in thickness (Example 1), (c) and (d) are 4 micrometers in thickness (Example) 2), (e), and (f) are an SEM image of a surface of a mold substrate having an aluminum alloy layer having a thickness of 3 μm (Example 4) and an SEM image of a cross section. It is the surface SEM image of the anti-reflective film formed using the type | mold for moth eyes produced using the type | mold base material from which the thickness of an aluminum alloy layer differs, (a) And (b) is 6 micrometers in thickness (Example) 1), (c) and (d) are 4 μm (Example 2), and (e) and (f) are mold substrates having an aluminum alloy layer having a thickness of 3 μm (Example 4). It is the surface SEM image of the anti-reflective film formed using the produced mold for moth eyes. It is the surface SEM image of the anti-reflective film formed using the type | mold for moth eyes produced using the type | mold base material from which the thickness of an aluminum alloy layer differs, (a) is thickness 6 micrometers (Example 1), ( b) is a surface SEM image of an antireflection film formed using a moth-eye mold produced using a mold substrate having an aluminum alloy layer having a thickness of 4 μm (Example 2). It is the surface SEM image of the anti-reflective film formed using the mold for moth-eye produced using the mold base material from which the thickness of an aluminum alloy layer differs, (a) is 4 micrometers in thickness (Example 3), ( b) is a surface SEM image of an antireflection film formed using a moth-eye mold produced using a mold substrate having an aluminum alloy layer having a thickness of 3 μm (Example 4). 6 is a graph showing the relationship between the average diameter and the haze value of the region surrounded by the annular convex group of antireflection films of Examples 1 to 4 and Comparative Example. (A) is the surface SEM image of the antireflection film of Example 1, and (b) is the surface SEM image of the antireflection film of Example 5. (A) And (b) is a schematic diagram for demonstrating the manufacturing method of the type | mold for manufacturing the antireflection film by which the moth-eye structure was superimposed on the anti-glare structure of patent document 5, (c) These are the schematic diagrams for demonstrating the manufacturing method of the anti-reflective film using the type | mold. (A) is a cross-sectional SEM image of a high-purity aluminum layer having a thickness of 4 μm, (b) is a surface SEM image of a high-purity aluminum layer having a thickness of 2 μm, and (c) is a high-temperature having a thickness of 4 μm. It is the surface SEM image of the anti-reflective film formed using the type | mold for moth eyes produced using the type | mold base material which has a purity aluminum layer.

Hereinafter, an antireflection film according to an embodiment of the present invention, a mold suitably used for producing such an antireflection film, and a method of manufacturing the mold will be described with reference to the drawings. Embodiments of the present invention are not limited to the embodiments exemplified below.

First, a moth-eye mold described in Patent Document 5, a manufacturing method thereof, and a method of manufacturing an antireflection film using the moth-eye mold will be described. The mold substrate used for the production of the moth-eye mold is different from the embodiment according to the present invention, but the method for producing the moth-eye mold by alternately performing the anodic oxidation and the etching or the moth-eye mold is used. The method of forming the antireflection film is common to the embodiment according to the present invention. In the method for producing a moth-eye mold described in Patent Document 5, a mold substrate having an aluminum film (a high purity aluminum film) is used.

In the mold manufacturing method described in Patent Document 5, first, as shown in FIG. 12A, an aluminum film 18p deposited on a substrate 12 is prepared. The aluminum film 18p is formed of high purity aluminum, for example, with a purity of 99.99% by mass or more. The thickness of the aluminum film 18p is 0.5 μm or more and 5 μm or less, and a plurality of crystal grains 18pa having an average crystal grain size of 200 nm or more and 5 μm or less exist on the surface 18ps of the aluminum film 18p. FIG. 12A schematically shows a crystal grain boundary 18pb existing on the surface 18ps of the aluminum film 18p. The aluminum film 18p can be formed using, for example, a vacuum film forming method such as a sputtering method or an electron beam evaporation method.

Next, anodic oxidation (AO) and etching (Et) are alternately repeated a plurality of times on the aluminum film 18p, thereby obtaining the moth-eye mold 900A having the porous alumina layer 22 shown in FIG.

First, a porous alumina layer 22 having fine recesses (pores) 22p is formed by anodizing the surface of the aluminum film 18p. FIG. 12 (b) shows the structure of the finally obtained porous alumina layer 22, but here, for the sake of simplicity, a common structure is used regardless of changes in the shape and size of the fine recesses 22p. Indicated by reference numerals.

The porous alumina layer 22 is formed corresponding to the uneven shape of the surface 18 ps of the aluminum film 18 p. That is, the surface of the porous alumina layer 22 has a plurality of convex portions corresponding to the plurality of crystal grains 18pa of the aluminum film 18p. Further, the fine recess 22p of the porous alumina layer 22 is formed at a position corresponding to the surface of the crystal grain 18pa and the crystal grain boundary 18pb. That is, the fine recess 22p is formed between the plurality of protrusions and on the surface of the plurality of protrusions. For example, the porous alumina layer 22 is formed by anodizing the surface 18 ps of the aluminum film 18 p with an oxalic acid aqueous solution (concentration 0.06 mass%, liquid temperature 5 ° C.) at an applied voltage of 80 V for 30 seconds. . By adjusting the anodic oxidation conditions (for example, the type of electrolytic solution, the applied voltage, and the anodic oxidation time), the interval between the minute recesses, the depth of the minute recesses, and the like can be adjusted. The electrolytic solution used in the step of forming the porous alumina layer is, for example, an aqueous solution containing an acid selected from the group consisting of oxalic acid, tartaric acid, phosphoric acid, chromic acid, citric acid, and malic acid.

Next, the porous alumina layer 22 obtained by anodic oxidation is brought into contact with an alumina etchant so as to be etched by a predetermined amount, thereby enlarging the hole diameter of the fine recess 22p. Here, by employing wet etching, the side surfaces (also referred to as pore walls) of the fine recesses 22p and the barrier layer can be etched almost isotropically. The amount of etching (that is, the size and depth of the fine recess 22p) can be controlled by adjusting the type, concentration, and etching time of the etching solution. For example, the fine recesses 22p are enlarged by performing etching for 25 minutes using phosphoric acid (concentration 1 mol / L, liquid temperature 30 ° C.). In addition, for example, an aqueous solution of an organic acid such as formic acid, acetic acid, or citric acid or a mixed aqueous solution of chromium phosphoric acid can be used as the etching solution.

Thereafter, if necessary, the aluminum film 18p is partially anodized again to grow a fine recess 22p in the depth direction and to thicken the porous alumina layer 22. Here, since the growth of the fine recess 22p starts from the bottom of the already formed fine recess 22p, the side surface of the fine recess 22p is stepped.

Thereafter, if necessary, the pore diameter of the fine concave portion 22p is further expanded by etching the porous alumina layer 22 by bringing it into contact with an alumina etchant.

Thus, by repeating the anodizing step and the etching step, the moth-eye mold 900A (FIG. 12B) is obtained. In the moth-eye mold 900A, as a result of the porous alumina layer 22 being formed on the surface 18ps of the aluminum film 18p, a plurality of convex portions corresponding to the surface shapes of the plurality of crystal grains 18pa of the aluminum film 18p are formed on the surface. . Accordingly, the surface of the moth-eye mold 900A has a plurality of fine spaces between the plurality of convex portions (the portion corresponding to the crystal grain boundary 18pb) and between the plurality of convex portions (the portion corresponding to the surface of the crystal grain 18pa). A concave portion 22p is formed.

Since the moth-eye mold 900A has a shape in which the moth-eye structure inverted with the concavo-convex structure having a two-dimensional size of 200 nm or more and 5 μm or less is superimposed, when an antireflection film is produced using the moth-eye mold 900A, A shape in which the concavo-convex structure having a two-dimensional size of 200 nm to 5 μm on the surface of the moth-eye mold 900A is inverted is formed. This shape can exhibit an antiglare function. That is, by using the moth-eye mold 900A, an antireflection film capable of exhibiting an antiglare function can be produced.

As described above, for example, in the mold manufacturing method for manufacturing the antireflection film in which the moth-eye structure is superimposed on the antiglare structure described in

Patent Documents

1, 2, and 4, an inverted moth-eye structure is formed. In addition to the steps, it is necessary to perform a step of forming a concavo-convex structure for forming an antiglare structure. According to the method for manufacturing a moth-eye mold described in Patent Document 5, since an aluminum film having an uneven structure for forming an antiglare structure is used in the step of depositing an aluminum film, the unevenness for forming the antiglare structure is used. A moth-eye mold for manufacturing an antireflection film in which a moth-eye structure is superimposed on an anti-glare structure can be easily manufactured without performing a separate step of forming the structure.

In order to produce an antireflection film with excellent antireflection performance, the fine recess 22p preferably has a two-dimensional size of 50 nm or more and less than 500 nm when viewed from the normal direction of the surface. . In the moth-eye mold 900A, the two-dimensional size (opening diameter: D _p ) of the fine concave portions 22p and the distance between the fine concave portions 22p (inter-adjacent distance D _int ) are approximately the same. That is, the fine concave portions 22p are densely packed, and assuming that the shape of the fine concave portions 22p when viewed from the normal direction of the surface is a circle, the adjacent circles overlap each other, and the adjacent fine concave portions 22p A collar may be formed between them. The depth (D _depth ) of the fine recess 22p is about 10 nm or more and less than 1000 nm (1 μm). In general, since the interval between minute recesses is almost proportional to the magnitude of the applied voltage, in order to form a pore having a two-dimensional size of 50 nm or more and less than 500 nm, the pore interval is 50 nm or more and less than 500 nm. What is necessary is just to apply the voltage in which a fine recessed part is formed.

According to Patent Document 5, by adjusting the film formation conditions when forming an aluminum film having a thickness of 0.5 μm or more, a plurality of crystal grains having an average crystal grain size of 200 nm to 5 μm are formed on the surface. An existing aluminum film can be formed. The upper limit of the aluminum film thickness is preferably 5 μm or less from the viewpoint of productivity.

For example, an aluminum film having a total thickness of 1 μm and an average crystal grain size of 200 nm (Example 1) or a thickness by performing a process of forming an aluminum layer having a thickness of 200 nm by a sputtering method five times. An aluminum film having a total thickness of 4.2 μm and an average crystal grain size of 700 nm is produced by performing the step of forming an aluminum layer having a thickness of 420 nm by sputtering 10 times.

Using the moth-eye mold 900A, an antireflection film can be produced as follows.

As shown in FIG. 12C, the ultraviolet curable resin 32C is irradiated with ultraviolet rays through the moth-eye mold 900A in a state where the ultraviolet curable resin 32C is applied between the surface of the workpiece 42 and the moth-eye mold 900A. The ultraviolet curable resin 32C is cured by irradiating (UV). The ultraviolet curable resin 32C may be applied to the surface of the workpiece 42 or may be applied to the mold surface (surface having a moth-eye structure) of the moth-eye mold 900A. As the ultraviolet curable resin, for example, an acrylic resin can be used.

Thereafter, by separating the moth-eye mold 900A from the workpiece 42, the concavo-convex structure of the moth-eye mold 900A (a structure in which the inverted moth-eye structure is superimposed on the concavo-convex structure constituted by a plurality of convex portions) is transferred. A cured product layer of the cured UV curable resin 32 </ b> C is formed on the surface of the workpiece 42. In this way, an antireflection film is obtained in which the moth-eye structure is superimposed on the concavo-convex structure in which the concavo-convex structure constituted by a plurality of convex portions having an average two-dimensional size of 200 nm to 5 μm is inverted. That is, an antireflection film in which the moth-eye structure is superimposed on the concavo-convex structure exhibiting an antiglare function having an average two-dimensional size of 200 nm to 5 μm is obtained.

As described in Patent Document 5, although the haze value of the obtained antireflection film can be controlled by controlling the crystal grain size and distribution of the aluminum layer, for example, the haze value is 2% or more. It is not easy to control to 6% or less. This is because the structure of the high-purity aluminum layer is easily changed depending on the deposition conditions.

For example, as shown in FIGS. 13A and 13B, a high-purity aluminum layer having a thickness of 4 μm or 2 μm has discontinuously large crystal grains (“abnormal particles”) compared to most crystal grains. Are easily formed, and gaps are formed around the abnormal particles. When such an aluminum layer is alternately subjected to anodic oxidation and etching, fine concave portions are also formed on the side surfaces (surfaces facing the gaps) of the abnormal particles. Therefore, when an antireflection film is formed using a mold having such a porous alumina layer, large convex portions having small convex portions on the side surfaces are formed as shown in FIG. Large convex portions correspond to gaps formed around abnormal particles. Such relatively large convex portions of the antireflection film are easily broken by friction, and reduce the scratch resistance of the antireflection film. Moreover, the haze of such an antireflection film is relatively large. For example, it is not easy to mass-produce an antireflection film having a haze value of 12% or less with good reproducibility.

On the other hand, Patent Documents 6 and 7 disclose a method of forming an aluminum alloy layer having a highly specular surface and a method of manufacturing a moth-eye mold using a mold substrate having such an aluminum alloy layer. ing. When the moth-eye molds described in Patent Documents 6 and 7 are used, an antireflection film having no unnecessary haze can be formed.

The present inventor has studied a method for producing a moth-eye mold capable of producing an antireflection film having an appropriate haze value using a mold substrate having an aluminum alloy layer described in Patent Document 6. The appropriate haze value is, for example, 2% or more and 6% or less, and when pasted on a recent high-definition display panel, it does not deteriorate a high-definition image and has clearness and anti-glare property. Is expressed.

The structure of the antireflection film according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a surface SEM image of the antireflection film according to the embodiment (Example 1 described later), and FIG. 1B is a schematic plan view showing the surface structure of the antireflection film according to the embodiment. FIG. 1C is a schematic cross-sectional view taken along line 1C-1C ′ of FIG.

As understood from the comparison between the SEM photograph of FIG. 1A and the schematic diagram of FIG. 1B, the antireflection film 32A according to the embodiment of the present invention is as viewed from the normal direction of the surface. It has a plurality of first protrusions 32a having a two-dimensional size of 50 nm or more and less than 300 nm and a height of 50 nm or more and 300 nm or less, and each of the plurality of first protrusions 32a is adjacent to each other by 50 nm or more and less than 300 nm. The plurality of first convex portions 32a arranged in a ring at an inter-distance includes a plurality of annular convex portion groups, and the plurality of regions surrounded by each of the plurality of annular convex portion groups is an average of a major axis and a minor axis A plurality of first regions R1 having a value greater than 300 nm and less than or equal to 800 nm are included. The major axis and minor axis of each first region R1 are substantially elliptical shapes passing through the apex of the first convex part 32a constituting the annular convex part group in the SEM image (see the broken lines in FIGS. 1A and 1B). ) And can be obtained as the longest and shortest diameters of the substantially elliptical shape. When the annular convex portion group includes the first convex portions 32a arranged in a double annular shape, the major axis and the minor axis are obtained based on a substantially elliptical shape passing through the apex of the inner first convex portion 32a. Typically, the first convex portion 32a does not exist in the first region R1.

In the plurality of first regions R1, there are a first region R1 having a second convex portion 32b having a height smaller than that of the first convex portion 32a and a first region R1 having no second convex portion 32b. Further, in the first region R1 having the second convex portion 32b, there is a first region R1 having two or more second convex portions 32b.

As schematically shown in FIG. 1C, the first convex portion 32a and the second convex portion 32b are basically formed on a flat support portion 32s. The conventional antireflection film having an antiglare function, such as Patent Document 5, has a structure in which a moth-eye structure is superimposed on a relatively large uneven structure that exhibits the antiglare function, whereas the antireflection film 32A according to the embodiment is used. Does not have a relatively large uneven structure that exhibits an antiglare function. In the antireflection film 32A, a plurality of first regions R1 in which the average value of the major axis and the minor axis formed by the first convex portion 32a is greater than 300 nm and less than or equal to 800 nm are arranged to form the first region R1. The first convex portion 32a is considered to exhibit an antiglare function.

An example of a mold manufacturing method capable of forming an antireflection film 32A having a characteristic moth-eye surface structure having a plurality of first regions R1 will be described with reference to FIG. FIGS. 2A and 2B are schematic views for explaining a mold manufacturing method according to an embodiment of the present invention.

First, as shown in FIG. 2A, the substrate 12 includes an inorganic base layer 14 formed on the substrate 12 as necessary, and an aluminum alloy layer 18 formed on the inorganic base layer 14. A mold substrate is prepared. The surface of the substrate 12 may be, for example, any one of a plane, a curved surface, and a roll surface. The material of the substrate 12 may be an acid-resistant insulator such as glass, ceramic, or plastic. Moreover, the base material 12 may be an aluminum material, for example. Or what provided the insulator on the metal which is not aluminum, for example may be used. From the viewpoint of mass productivity, it is preferable to use a roll-shaped aluminum substrate. The inorganic underlayer 14 is, for example, a silicon oxide layer, a tantalum oxide layer, or a titanium oxide layer. The thickness of the inorganic underlayer 14 is preferably 50 nm or more and 300 nm or less.

The aluminum alloy layer 18 contains aluminum (Al) and titanium (Ti). Hereinafter, an alloy containing aluminum and titanium may be referred to as “Al—Ti”. The Ti content in the aluminum alloy layer 18 is preferably more than 0% by mass and less than 2.0% by mass, and more preferably more than 0% by mass and less than 1.0% by mass. When the Ti content is 1.0% by mass or more, it may be difficult to form the annular convex group, and the Ti content is most preferably about 0.5% by mass.

Nd (neodymium) can be used instead of titanium. The thickness of the aluminum alloy layer 18 is 2 μm or more. In such a thick aluminum alloy layer 18, V-shaped depressions are formed between crystal grains as schematically shown in FIG. The size of the crystal grains is approximately over 300 nm. As described in Patent Document 7, the aluminum alloy layer 18 may further contain N (nitrogen). N can be introduced into the aluminum alloy layer, for example, by mixing it in an atmospheric gas when depositing the aluminum alloy layer by sputtering. When the aluminum alloy layer contains nitrogen (Examples 1 to 3), the nitrogen content preferably does not exceed 5.7% by mass, and is further 1.2% by mass to 2.0% by mass. preferable.

A porous alumina layer 22 obtained by alternately repeating anodic oxidation and etching on the surface of such an aluminum alloy layer 18 is a comparison formed on the surface forming V-shaped depressions between crystal grains. The first recess 22a is large (deep) and the second recess 22b is relatively small (shallow) formed on the flat surface of the crystal grains. When viewed from the normal direction of the surface of the plurality of first recesses 22a, the two-dimensional size is 50 nm or more and less than 300 nm, and the depth is 50 nm or more and 300 nm or less. Each of the plurality of first recesses 22a includes a plurality of annular recess groups in which the plurality of first recesses 22a are annularly arranged at a distance between adjacent portions of 50 nm or more and less than 300 nm.

Since the first recess 22a is formed on the surface forming the V-shaped depression, two types of first recesses 22a extending in opposite directions are formed at one crystal grain boundary. The first convex portion 32a of the antireflection film 32A corresponds to the structure in which the first concave portion 22a is transferred. 1 (a) and 1 (b), it can be seen that the first protrusions 32a are arranged in a double ring shape. It can also be seen that the first region R1 in the antireflection film 32A is formed corresponding to the crystal grains of the aluminum alloy layer 18. Therefore, the size of the first region R1 in the antireflection film 32A can be controlled by controlling the size of the crystal grains in the aluminum alloy layer 18.

As will become clear from the examples and comparative examples described below, the size of the crystal grains can be controlled by controlling the thickness of the aluminum alloy layer. Of course, depending on the composition of the aluminum alloy layer (Ti content) and film formation conditions, according to the study of the present inventors, the size of the crystal grains is controlled by controlling the thickness of the aluminum alloy layer. Is considered the most suitable for mass production.

In the following Examples 1 to 4 and Comparative Examples, an aluminum alloy layer containing 0.5% by mass of Ti (Examples 1 to 3 further includes N of 1.2% by mass to 2.0% by mass). A mold substrate having aluminum alloy layers having different thicknesses was used, and anodization (0.3 mass% oxalic acid aqueous solution, 10 ° C., 80 V) and etching (10 mass% phosphoric acid aqueous solution) were used. , 30 [deg.] C.) alternately, and anodizing 5 times and etching 4 times, a moth-eye mold 100A (see FIG. 2B) was produced. As the substrate 12, a glass substrate or an aluminum pipe (rolled aluminum substrate) was used. As the inorganic underlayer 14, a tantalum oxide (Ta ₂ O ₅ ) layer having a thickness of 200 nm was formed. The aluminum alloy layer 18 was formed by using a DC magnetron sputtering apparatus and introducing nitrogen gas (N ₂ ) in addition to argon (Ar) gas as a sputtering gas as necessary. During sputtering, the surface temperature of the inorganic underlayer 14 was controlled at 80 ° C. Typical conditions are a sputtering gas (Ar gas) flow rate of 440 sccm, a vacuum degree during sputtering of 0.4 Pa, and a nitrogen gas flow rate when nitrogen gas is introduced is 10 sccm (for details, see Patent Reference 7). Individual conditions such as anodizing time and etching time are also shown in Table 1 below. Since the sample form of the comparative example is different from those of Examples 1 to 4, conditions such as anodizing time and etching time cannot be directly compared, but the anodizing time is about 33 seconds and the etching time is about 25. Minutes.

Each antireflection film was produced by the method described with reference to FIG. As the workpiece 42, a TAC (triacetyl cellulose) film was used. Table 1 shows the haze value of each antireflection film. The haze value was measured using an integrating sphere turbidimeter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. The projection was parallel light. The sum of the straight transmitted light and the diffuse transmitted light was defined as the total light transmitted light, and the ratio of the diffuse transmitted light to the total light transmitted light was defined as the haze value.

3A shows an SEM image of the surface of the mold substrate used in Example 1, FIG. 3B shows an SEM image of the surface of the moth-eye mold of Example 1, and FIG. Shows an SEM image of the surface of the antireflection film.

The mold base material of Example 1 shown in FIG. 3A has an aluminum alloy layer with a thickness of 6 μm. Particles having a particularly large particle size that are visible in the center and lower right of the SEM image in FIG. 3A are abnormal particles. The composition of an aluminum alloy containing 0.5% by mass of Ti and 1.2% by mass or more and 2.0% by mass or less of N with the remainder being Al, completely suppresses the generation of abnormal particles. However, the generation of abnormal particles is less than that of the high-purity aluminum layer, and the gap around the abnormal particles observed in the high-purity aluminum layer (see FIGS. 13A and 13B) is I couldn't see it.

The porous alumina layer on the surface of the moth-eye mold of Example 1 shown in FIG. 3B has a two-dimensional size of 50 nm or more and less than 300 nm and a depth of 50 nm or more when viewed from the normal direction of the surface. It has a plurality of first recesses of 300 nm or less. Each of the plurality of first recesses includes a plurality of annular recess groups in which the plurality of first recesses are annularly arranged at a distance between adjacent portions of 50 nm or more and less than 300 nm. The first recesses are randomly and uniformly formed on the surface of the abnormal particles.

As described with reference to FIG. 1A, the antireflection film of Example 1 shown in FIG. 3C has a two-dimensional size of 50 nm or more and 300 nm when viewed from the normal direction of the surface. And a plurality of first convex portions 32a having a height of 50 nm or more and 300 nm or less. Each of the plurality of first convex portions 32a includes a plurality of annular convex portion groups in which the plurality of first convex portions 32a are annularly arranged at an adjacent distance of 50 nm or more and less than 300 nm. The plurality of regions surrounded by each include a plurality of first regions R1 having an average value of a major axis and a minor axis of more than 300 nm and 800 nm or less. In the SEM image shown in FIG. 1 (a), the annular convex group composed of the first convex part 32a whose broken line passes substantially through the apex has an average size, and is surrounded by this annular convex group. The major axis of the first region (the region within the broken line) was 850 nm, the minor axis was 650 nm, and the average value of the major axis and the minor axis was 750 nm. That is, it can be said that the plurality of first regions in the antireflection film of Example 1 includes many first regions having an average value of the major axis and the minor axis of 750 nm. In addition, although the average diameter of the cyclic | annular area | region shown in Table 1 is also an average value of the major axis and minor axis of a 1st area | region, how to obtain | require is different. The value of the average diameter of the annular region in Table 1 will be described in detail later. The average diameter of the annular region in Table 1 of Example 1 was 723.8 nm, and the haze value of the antireflection film was 11.48%.

FIGS. 4 (a) to 4 (c) show SEM images of the surfaces of the antireflection films according to Examples 2 to 4. FIG. The thicknesses of the aluminum alloy layers of the mold base materials used for producing the moth-eye molds of Examples 2 to 4 are 4 μm, 4 μm, and 3 μm, respectively. In Examples 2 and 3, aluminum alloy layers having the same thickness were used, but the film forming conditions were different.

In the antireflection film of Example 2 shown in FIG. 4A, the major axis of the first region (the region within the dashed line) surrounded by the annular convex portion group indicated by the broken line passing through the apex is 800 nm, and the minor axis is 500 nm. The average value of the major axis and the minor axis was 650 nm. The average diameter of the annular region in Table 1 of Example 2 was 572 nm, and the haze value of the antireflection film was 4.38%.

On the other hand, in the antireflection film of Example 3 shown in FIG. 4B, the major axis of the first region (the region within the broken line) surrounded by the annular convex group indicated by the broken line passing through the apex is 600 nm and the minor diameter. Was 450 nm, and the average value of the major axis and the minor axis was 525 nm. The average diameter of the annular region in Table 1 of Example 3 was 514.8 nm, and the haze value of the antireflection film of Example 3 was 5.63%.

Example 2 and Example 3 differ in the film forming conditions of the aluminum alloy layer. In Example 2, two targets (two sources) were used in sputtering and left for a fixed time each time a film having a thickness of 200 nm was formed, thereby suppressing an increase in the temperature of the surface of the mold substrate during sputtering. In Example 3, using one target (one source) in sputtering, the film was allowed to stand for a certain time each time a film having a thickness of 1000 nm was formed, thereby suppressing an increase in the temperature of the surface of the mold substrate during sputtering. This difference in the film forming conditions is considered to be the difference in the size of the crystal grains of the aluminum alloy layer.

In the antireflection film of Example 4 shown in FIG. 4C, the major axis of the first region (the region within the dashed line) surrounded by the annular convex portion group indicated by the broken line passing through the apex is 350 nm, and the minor axis is 250 nm. The average value of the major axis and the minor axis was 300 nm. The average diameter of the annular region in Table 1 of Example 4 was 543.4 nm, and the haze value of the antireflection film of Example 4 was 2.29%.

FIG. 5 is a surface SEM image of the antireflection film of the comparative example. The anti-reflection film of the comparative example is a clear-type anti-reflection film that is currently on the market and does not have an anti-glare function, and the first protrusions are irregularly arranged and the first region is not formed. . For comparison, the size of the area indicated by the broken line in FIG. 5 is about 200 nm, which is substantially equal to the distance between the adjacent first convex portions. The haze value of the antireflection film of the comparative example is as very small as 0.52%.

Next, with reference to FIGS. 6 and 7, the relationship between the thickness of the aluminum alloy layer and abnormal particles will be described. FIG. 6 shows SEM images of mold bases having different thicknesses of aluminum alloy layers. FIGS. 6 (a) and 6 (b) show a thickness of 6 μm (Example 1), and FIGS. 6 (c) and 6 (d). Is a SEM image of a mold substrate having an aluminum alloy layer having a thickness of 4 μm (Example 2) and FIGS. 6E and 6F having a thickness of 3 μm (Example 4). It is a SEM image of an image and a section. FIG. 7 is a surface SEM image of an antireflection film formed using a moth-eye mold produced using mold bases having different thicknesses of aluminum alloy layers. FIGS. 7 (a) and 7 (b) are thicknesses. 7 μm (Example 1), FIGS. 7 (c) and (d) are aluminum with a thickness of 4 μm (Example 2), and FIGS. 7 (e) and (f) are aluminum with a thickness of 3 μm (Example 4). It is the surface SEM image of the anti-reflective film formed using the type | mold for moth eyes produced using the type | mold base material which has an alloy layer.

As can be seen from the SEM images of FIGS. 6A and 6B, the aluminum alloy layer having a thickness of 6 μm has large abnormal particles. In contrast, the aluminum alloy layer having a thickness of 4 μm has abnormal particles as can be seen from the SEM images of FIGS. 6C and 6D, but the size is 6 μm. Much smaller than the size of abnormal particles in the aluminum alloy layer. As can be seen from the SEM images in FIGS. 6E and 6F, the aluminum alloy layer having a thickness of 3 μm does not have abnormal particles. Thus, when the thickness of the aluminum alloy layer exceeds 3 μm, abnormal particles are included, and as the thickness of the aluminum alloy layer increases, the abnormal particles also increase.

When the surface SEM images of the antireflection film shown in FIGS. 7A, 7B, 7C, and 7D are viewed, the moth-eye for the moth eye manufactured using the mold base material having the aluminum alloy layer containing abnormal particles is shown. In the antireflection film formed using the mold, a recess having a size corresponding to abnormal particles is formed. In particular, as shown in FIGS. 7A and 7B, abnormal particles contained in an aluminum alloy layer having a thickness of 6 μm are very large (area circle equivalent diameter is 3 μm or more). An annular ridge is formed. 7C and 7D, a recess having a size corresponding to the abnormal particle is formed, but an annular ridge is not seen. This is presumably because the area equivalent circle diameter of the abnormal particles contained in the aluminum alloy layer having a thickness of 4 μm is relatively small, less than 2 μm. Further, as can be seen from FIGS. 7 (e) and (f), when a moth-eye mold produced using an aluminum alloy layer that does not contain abnormal particles is used, naturally, a recess having a size corresponding to the abnormal particles is also present. An annular ridge is not formed.

7A and 7B have a drawback that the antireflection film having an annular ridge has low scratch resistance. That is, if the surface of the antireflection film is rubbed with, for example, a cloth (for example, Savina MX manufactured by KB Seiren Co., Ltd., savina is a registered trademark), the annular ridge is destroyed, and the surface may appear cloudy. is there. Therefore, such an antireflection film is not preferable for applications requiring scratch resistance (for example, portable terminals such as smartphones).

7A to 7D, when the concave portion has a size corresponding to abnormal particles, the photocurable resin is used for the moth-eye mold in the transfer process when forming the antireflection film. It tends to remain in the recess, and as a result, it may be difficult to use the moth-eye mold continuously. For example, when the antireflection film is formed by the roll-to-roll method, there is a problem that the length of the continuous formation of the antireflection film is shortened and the production efficiency is lowered.

From the above, in order to suppress the occurrence of the annular bulge, the thickness of the aluminum alloy layer of the mold base is preferably less than 6 μm, and more preferably 4 μm or less. Moreover, in order to suppress the formation of a recess having a size corresponding to abnormal particles, the thickness of the aluminum alloy layer is preferably 3 μm or less.

Next, referring to FIG. 8, FIG. 9, and FIG. 10, the region (first region in Examples 1 to 4) surrounded by the annular convex group of the antireflection films of Examples 1 to 4 and the comparative example is described. The relationship between the average diameter and the haze value will be described. FIG. 8 is a surface SEM image of the antireflection film formed using a moth-eye mold produced using mold bases having different thicknesses of the aluminum alloy layer, and FIG. 8A shows a thickness of 6 μm ( Example 1), FIG. 8B is a surface SEM image of an antireflection film formed using a moth-eye mold produced using a mold substrate having an aluminum alloy layer having a thickness of 4 μm (Example 2). It is. FIG. 9 is a surface SEM image of an antireflection film formed by using a moth-eye mold produced using mold bases having different thicknesses of aluminum alloy layers, and FIG. 9A shows a thickness of 4 μm ( Example 3), FIG. 9B is a surface SEM image of an antireflection film formed using a moth-eye mold produced using a mold substrate having an aluminum alloy layer having a thickness of 3 μm (Example 4). It is. FIG. 10 is a graph showing the relationship between the average diameter and the haze value of the region surrounded by the annular convex portions of the antireflection films of Examples 1 to 4 and Comparative Example.

With reference to FIGS. 4 and 5, the relationship between the antireflection coating structures of Examples 1 to 4 and the comparative example (representative first region size) and the haze value has been described. An attempt was made to increase the accuracy of the size of the first region by obtaining the size of the one region as follows.

Select a 5 μm × 5 μm square area from the SEM image of the surface of the antireflection film. At this time, a target region is selected so as not to include a region where a structure corresponding to abnormal particles is formed. Among the selected areas, 10 are selected from the larger ones of the first areas, and the lengths of the major axis and the minor axis are measured. For the ten first regions, the average value of the major axis and the minor axis was determined. The obtained results are shown in Table 1 (average value of the annular region). Further, the relationship between the average value of the major axis and minor axis of the first region (= the average diameter of the region surrounded by the annular convex portion group) and the haze value is shown in the graph of FIG.

As can be seen from the graph of FIG. 10, it is recognized that the haze value tends to increase as the average value of the major axis and minor axis of the first region increases. In addition, the haze value of the antireflection film of Examples 2 and 3 is larger than the haze value of the antireflection film of Example 4. The antireflection films of Examples 2 and 3 are compared with abnormal particles. This is presumably because there is a large structure (area circle equivalent diameter exceeds 1 μm), and the haze value increases accordingly.

In the antireflection films of Examples 2 to 4, the average value of the major axis and the minor axis of the first region is in the range of 500 nm to 600 nm, and the haze value is in the range of 2% to 6%. . The antireflection films of Examples 2 to 4 have clearness and exhibit antiglare properties, and are preferably used for high-definition display panels.

Of course, the antireflection film of Example 1 can also be suitably used for applications or users that require relatively high antiglare properties. FIG. 11A shows a surface SEM image of the antireflection film of Example 1, and FIG. 11B shows a surface SEM image of the antireflection film of Example 5. In Example 5, an antireflection film was formed using a moth-eye mold produced in the same manner as in Example 1 (anodization time 33 seconds) except that the anodic oxidation time in the moth-eye mold manufacturing process was 45 seconds. Produced.

As can be seen from FIG. 11A, the height of the first protrusions in the antireflection film of Example 1 is 100 nm to 150 nm, and the height of the second protrusions in the region surrounded by the first protrusions. Is about 10 nm. Further, as can be seen from FIG. 11B, the height of the first convex portion in the antireflection film of Example 5 is 200 nm to 250 nm, and the second convex portion in the region surrounded by the first convex portion. The height is about 50 nm.

As described above, in the antireflection film according to the embodiment of the present invention, the first region surrounded by the first protrusions has an average value of the major axis and the minor axis of more than 300 nm and not more than 800 nm. In addition, the antiglare property can be exhibited while having clearness. The first convex portion and the second convex portion exhibit an antireflection function similarly to the conventional antireflection film having a moth-eye structure.

The present invention is used for an antireflection film, a mold suitably used for the production of such an antireflection film, and a method for manufacturing the mold. According to the present invention, the antireflection film is suitably used for a high-definition display panel.

32A Anti-reflective film 32s Support part 32a 1st convex part 32b 2nd convex part R1 1st area | region (annular area | region)

Claims

A plurality of first protrusions having a two-dimensional size of 50 nm or more and less than 300 nm and a height of 50 nm or more and 300 nm or less when viewed from the normal direction of the surface;
Each of the plurality of first protrusions includes a plurality of annular protrusion groups in which each of the plurality of first protrusions is arranged in an annular shape with an adjacent distance of 50 nm or more and less than 300 nm,
The plurality of regions surrounded by each of the plurality of annular convex groups includes an antireflection film including a plurality of first regions having an average value of a major axis and a minor axis of more than 300 nm and not more than 800 nm.
The antireflection film according to claim 1, wherein the plurality of first regions do not have the plurality of first protrusions.
3. The antireflection film according to claim 1, wherein the plurality of first regions include a first region having two or more second protrusions that are smaller in height than the plurality of first protrusions.
Having a porous alumina layer on the surface;
The porous alumina layer has a plurality of first recesses having a two-dimensional size of 50 nm or more and less than 300 nm and a depth of 50 nm or more and 300 nm or less when viewed from the normal direction of the surface,
Each of the plurality of first recesses includes a plurality of annular recess groups in which the plurality of first recesses are annularly arranged at an adjacent distance of 50 nm or more and less than 300 nm,
The plurality of regions surrounded by each of the plurality of annular recess groups includes a plurality of first regions having an average value of a major axis and a minor axis of more than 300 nm and not more than 800 nm.
Further comprising an aluminum alloy layer under the porous alumina layer;
The mold according to claim 4, wherein the aluminum alloy layer includes aluminum and titanium.
The mold according to claim 5, wherein the total thickness of the aluminum alloy layer and the porous alumina layer is 2 µm or more.
The mold according to claim 5 or 6, further comprising an inorganic underlayer under the aluminum alloy layer.
A method for producing a mold according to any one of claims 5 to 7,
(A) forming an aluminum alloy layer having a thickness of 2 μm or more on the substrate;
(B) forming a porous alumina layer having a plurality of fine recesses by partially anodizing the aluminum alloy layer;
(C) After the step (b), the porous alumina layer is brought into contact with an etching solution to enlarge the plurality of fine recesses of the porous alumina layer;
(D) After the said process (c), the process of growing the said several fine recessed part by further anodizing, The manufacturing method of a type | mold.