JP2015034835A - Anti-reflection structure, and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-reflection structure excelling in suppression of reflection and resistance to scratches.SOLUTION: In an anti-reflection structure 10 having periodic convexo-concave parts 20 on its surface, any random convex 21-1, which is not the outermost convex 21, and six convexes 21-2 to 21-7 whose total of distances from the random convex 21-1 is the smallest are so arranged that: (1) between each of four convexes 21-2, 21-3, 21-5 and 21-6 out of six convexes 21-2 to 21-7 and the random convex 21-1, there is a linking part 23, in a position lower than the apex 21a of the convex 21 but higher than the bottom point 22a of the concave 22, to link the convexes, and (2) between each of the remaining two convexes 21-4 and 21-7 of the six convexes 21-2 to 21-7 and the random convex 21-1, there is a concave 22.

Description

  The present invention relates to an antireflection structure and a method for manufacturing the antireflection structure.

  In recent years, an antireflection structure having a periodic concavo-convex portion on the surface thereof has been developed for a display device such as a liquid crystal display (LCD) or a solar cell (see, for example, Patent Document 1). The antireflection structure is a so-called moth-eye type, and since the pitch of the convex portions is equal to or less than the wavelength of visible light, the light reflectance can be reduced and the light transmittance can be improved in a wide wavelength range.

International Publication No. 2011/027909

  The concavo-convex portion of the conventional antireflection structure has a structure in which a large number of conical protrusions are arranged on a plane. In order to increase the filling rate of the protrusions, the protrusions are periodically arranged in a hexagonal lattice shape or a tetragonal lattice shape.

  In order to further improve the filling rate of the protrusions for the purpose of improving the low reflectivity of the antireflection structure, the lower portions of the protrusions may be arranged so as to overlap each other.

  However, if the lower portions of the protrusions are excessively overlapped, the difference in height between the top of the convex portion and the bottom point of the concave portion is reduced, which adversely affects low reflectivity.

  In addition, since the antireflection structure has an uneven portion on the surface, there is also a problem that the antireflection structure is easily damaged when the surface is rubbed.

  This invention is made | formed in view of the said subject, Comprising: It aims at provision of the manufacturing method of an antireflection structure excellent in low reflectivity and abrasion resistance, and an antireflection structure.

In order to solve the above object, an antireflection structure according to an aspect of the present invention is provided.
In the antireflection structure having periodic irregularities on the surface,
Arbitrary convex portions excluding the outermost convex portion and the six convex portions having the shortest sum of the distances from the arbitrary convex portions are (1) four of the six convex portions. Between each of the convex portions and the arbitrary convex portion, there is a connecting portion that connects the convex portions at a position lower than the top of the convex portion and higher than the bottom point of the concave portion, and (2) the six It arrange | positions so that a recessed part may exist between each of the remaining two said convex parts of a convex part, and the said arbitrary convex parts, It is characterized by the above-mentioned.

Furthermore, the manufacturing method of the antireflection structure according to another aspect of the present invention includes:
In the manufacturing method of the antireflection structure having the step of manufacturing the antireflection structure having the periodic irregularities on the surface, using the prototype having the periodic irregularities on the surface,
In the prototype, an arbitrary convex portion excluding the outermost convex portion and six convex portions having the shortest total distance from the arbitrary convex portion are (1) of the six convex portions. Between each of the four convex portions and the arbitrary convex portion, there is a connecting portion that connects the convex portions at a position lower than the vertex of the convex portion and higher than the bottom point of the concave portion, (2) The six convex portions are arranged such that a concave portion exists between each of the remaining two convex portions and the arbitrary convex portion.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the antireflection structure excellent in low reflectivity and abrasion resistance and an antireflection structure is provided.

It is a perspective view which shows a part of antireflection structure body by the 1st Embodiment of this invention. It is a top view (1) which shows typically the unevenness | corrugation of the surface of the antireflection structure of FIG. It is a figure which shows the unevenness | corrugation of the surface of the reflection preventing structure of FIG. It is a top view (2) which shows typically the unevenness | corrugation of the surface of the antireflection structure of FIG. It is explanatory drawing (1) of the manufacturing method of the reflection preventing structure by the 1st Embodiment of this invention. It is explanatory drawing (2) of the manufacturing method of the reflection preventing structure by the 1st Embodiment of this invention. It is explanatory drawing (3) of the manufacturing method of the reflection preventing structure by the 1st Embodiment of this invention. It is a top view which shows typically the unevenness | corrugation of the surface of the prototype of FIG. It is a perspective view which shows a part of antireflection structure body by the 2nd Embodiment of this invention. It is a top view which shows typically the unevenness | corrugation of the surface of the reflection preventing structure of FIG. It is a figure which shows the unevenness | corrugation of the surface of the reflection preventing structure of FIG. 6 is an explanatory diagram illustrating a method for producing an analysis model according to Example 1. FIG. It is explanatory drawing which shows the preparation methods of the analysis model by Comparative Examples 1-3. It is a figure which shows the analysis result of the reflectance by Example 1 and Comparative Examples 1-3.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

[First Embodiment]
FIG. 1 is a perspective view showing a part of an antireflection structure according to a first embodiment of the present invention. In FIG. 1, contour lines are shown by thin lines in order to express irregularities on the surface of the antireflection structure. FIG. 2 is a plan view (1) schematically showing irregularities on the surface of the antireflection structure of FIG. FIG. 2A shows an array of lattices connecting the vertices of the convex portions, and FIG. 2B shows a part of FIG. In FIG. 2, in order to make the drawing easier to see, the convex portions and the connecting portions are indicated by different dot patterns, the vertexes of the convex portions are black circles, the bottom points of the concave portions are white circles, and the grids connecting the vertexes of the convex portions are indicated by bold lines. FIG. 3 is a view showing irregularities on the surface of the antireflection structure of FIG. 1. 3A is unevenness in the cross section along line AA in FIG. 2, FIG. 3B is unevenness in the cross section along line BB in FIG. 2, and FIG. 3C is C in FIG. FIG. 3D shows the unevenness in the cross section along the line DD in FIG. 2.

  The antireflection structure 10 is of a so-called moth-eye type, and includes a base 12 and a resin layer 14 formed on the base 12 as shown in FIG. The base 12 and the resin layer 14 may have translucency. Periodic uneven portions 20 are formed on the surface of the resin layer 14. In addition, the antireflection structure 10 may be configured by only the resin layer 14.

  The base 12 is formed in a sheet shape, a plate shape, or a block shape, for example. Although the material of the base | substrate 12 is not specifically limited, For example, glass or a plastics etc. are used.

  As the glass, for example, soda lime glass, non-alkali glass, quartz glass or the like is used. As a glass forming method, for example, a float method, a fusion method or the like is used.

  Examples of plastics include (meth) acrylic resins such as polymethyl methacrylate, methyl methacrylate and other alkyl (meth) acrylates, and copolymers of vinyl monomers such as styrene; polycarbonate, diethylene glycol bisallyl carbonate (CR-39) (Brominated) bisphenol A type di (meth) acrylate homopolymer or copolymer, (brominated) polymer of urethane-modified monomer of bisphenol A mono (meth) acrylate and copolymer Thermosetting (meth) acrylic resins such as coalescence; polyesters, especially polyethylene terephthalate, polyethylene naphthalate and unsaturated polyesters, acrylonitrile-styrene copolymers, polyvinyl chloride, polyurethane, epoxy Shi resins, polyarylate, polyether sulfone, polyether ketone, cycloolefin polymer (trade name: ARTON, ZEONOR) and the like are preferable. In addition, an aramid resin considering heat resistance can be used.

  The resin layer 14 is formed, for example, by applying a thermosetting or photocurable resin on the substrate 12 and curing it. An uneven portion 20 is formed on the surface of the resin layer 14.

  As shown in FIG. 1 and FIG. 2, the concavo-convex portion 20 is formed between the predetermined convex portions 21 at a position lower than the convex portion 21, the concave portion 22, and the vertex 22 a of the convex portion 21 and higher than the bottom point 22 a of the concave portion 22. And a connecting portion 23 for connecting the two. A plurality of convex portions 21, a plurality of concave portions 22, and a plurality of connecting portions 23 are two-dimensionally arranged.

  The convex portions 21 are periodically arranged in, for example, a regular hexagonal lattice shape, a quasi-hexagonal lattice shape, a regular tetragonal lattice shape, or a quasi-tetragonal lattice shape (a regular hexagonal lattice shape in FIGS. 1 and 2). In order to increase the filling rate of the convex portions 21, the convex portions 21 are preferably periodically arranged in a hexagonal lattice shape. Hereinafter, a case where the convex portions 21 are periodically arranged in a hexagonal lattice shape will be described. Note that the case where the convex portions 21 are periodically arranged in a tetragonal lattice pattern will be described in the second embodiment.

  “Periodically arranged in a regular hexagonal lattice” means that, as shown in FIG. 2, the arbitrary convex portion 21-1 is disposed around the arbitrary convex portion 21-1 excluding the outermost convex portion 21. Means that six convex portions 21-2 to 21-7 that are the shortest and the same distance from each other are arranged. The vertices of the six convex portions 21-2 to 21-7 are arranged at an equal pitch with an interval of 60 ° around the vertex of the convex portion 21-1, and constitute a regular hexagonal lattice.

  “Periodically arranged in a quasi-hexagonal lattice shape” means that they are periodically arranged in a shape that conforms to a regular hexagonal lattice. The shape conforming to the regular hexagonal lattice is a shape obtained by distorting a regular hexagonal lattice such as a shape obtained by stretching a regular hexagonal lattice in a predetermined direction. A lattice having a shape obtained by distorting a regular hexagonal lattice may be continuously arranged in a linear shape, a curved shape, or a meandering shape.

In the present embodiment, as shown in FIG. 2, there are six convex portions 21-1 excluding the outermost convex portion 21, and the total (sum) of the distances from the convex portions 21-1 being the shortest. The convex portions 21-2 to 21-7 are arranged so as to satisfy the following (1) and (2).
(1) Between each of the four convex portions 21-2, 21-3, 21-5, 21-6 among the six convex portions 21-2 to 21-7 and the convex portion 21-1. There is a connecting portion 23.
(2) A concave portion 22 exists between each of the remaining two convex portions 21-4 and 21-7 among the six convex portions 21-2 to 21-7 and the convex portion 21-1. .

  “Distance” is the distance between the vertices 21 a of the convex portions 21. When there are a plurality of combinations of six convex portions having the shortest total distance, the above (1) and (2) are established for all combinations. In the present embodiment, there is only one combination of six convex portions with the shortest total distance.

  When the above (1) and (2) are established, as shown in FIG. 2, for example, along three directions intersecting around an arbitrary convex portion 21-1, along two directions (F1 direction and F2 direction). The convex portions 21 and the connecting portions 23 are alternately arranged, and the convex portions 21 and the concave portions 22 are alternately arranged along the remaining one direction (F3 direction). The pitch P1 (see FIGS. 3A and 3B) of the convex portions 21 arranged at intervals in the F1 direction, the F2 direction, and F3 may be set to a length equal to or shorter than the wavelength of visible light. The pitch P2 (see FIG. 3C) of the convex portions 21 arranged at intervals in the direction perpendicular to the F3 direction is larger than the pitch P1. Concave portions 22 and connecting portions 23 are alternately arranged along a direction parallel to the F1 direction (see FIGS. 2 and 3D).

  Thus, the direction where the convex part 21 and the recessed part 22 are arrange | positioned alternately differs from the direction where the convex part 21 and the connection part 23 are arrange | positioned alternately. Therefore, the height difference H1 (see FIG. 3B) between the vertex 21a of the convex portion 21 and the bottom point 22a of the concave portion 22, and the vertex 21a of the convex portion 21 and the predetermined portion 23a of the connecting portion 23 (see FIG. 1). The height difference H2 (see FIG. 3A) can be designed independently. Therefore, the height difference H1 and the height difference H2 can be optimized independently. Here, the predetermined portion 23 a of the connecting portion 23 is the lowest portion between the vertices 21 a of the convex portions 21 and is the highest portion between the bottom points 22 a of the concave portions 22.

  In order to optimize the height difference H1 and the height difference H2, first, the range of the pitch P1 may be set. As described above, the pitch P1 is set to a length equal to or shorter than the wavelength of visible light, and may be, for example, 400 nm or less (preferably 300 nm or less). The pitch P1 may be, for example, 50 nm or more (preferably 100 nm or more) from the viewpoint of productivity. Therefore, the pitch P1 may be 50 to 400 nm.

  Next, the range of the aspect ratio of the uneven portion 20 is set. The aspect ratio of the concavo-convex portion 20 is represented by a ratio H1 / P1 between the height difference H1 between the apex 21a of the convex portion 21 and the bottom point 22a of the concave portion 22 and the pitch P1 of the convex portion 21. The aspect ratio H1 / P1 is, for example, 0.5 or more (preferably 0.7 or more, more preferably 1 or more) from the viewpoint of low reflectivity of the antireflection structure 10. The aspect ratio H1 / P1 is, for example, 4 or less (preferably 3 or less, more preferably 2 or less) from the viewpoint of productivity. In addition, when the pitch in the F1 direction of the convex part 21, the pitch in the F2 direction of the convex part 21, and the pitch in the F3 direction of the convex part 21 are different, the aspect ratio is obtained with the shortest pitch. Since the aspect ratio H1 / P1 is 0.5 to 4, the height difference H1 may be 100 to 500 nm, for example.

  Next, a ratio H2 / H1 between the height difference H1 and the height difference H2 is set. As the ratio H2 / H1 increases, the height of the predetermined portion 23a of the connecting portion 23 decreases, so that the low reflectivity of the antireflection structure 10 is improved. The ratio H2 / H1 is, for example, 0.1 or more (preferably 0.2 or more, more preferably 0.3 or more). On the other hand, as the ratio H2 / H1 is decreased, the height of the predetermined portion 23a of the connecting portion 23 is increased and the convex portion 21 is reinforced, so that the anti-reflection structure 10 has better scratch resistance. The ratio H2 / H1 is, for example, 0.9 or less (preferably 0.7 or less, more preferably 0.5 or less). Since the ratio H2 / H1 is 0.1 to 0.9, the height difference H2 may be 30 to 300 nm, for example.

  In this embodiment, since the height difference H1 and the height difference H2 can be optimized independently, the aspect ratio H1 / P1 and the ratio H2 / H1 can be optimized independently. Both low reflectivity and scratch resistance are possible.

  The pitch P1, the height difference H1, the height difference H2, and the like are obtained from an AFM image taken with an atomic force microscope (AFM) and a cross-sectional profile thereof.

  In the present embodiment, the convex portions 21 and the connecting portions 23 are alternately arranged along the F1 direction and the F2 direction which are linear directions, and the convex portions 21 and the concave portions 22 are arranged along the F3 direction which is a linear direction. Although alternately arranged, the present invention is not limited to this as long as the above (1) and (2) are established. For example, when hexagonal lattices are arranged in a curved shape, the convex portions 21 and the connecting portions 23 may be alternately arranged along a predetermined curved direction.

  In the present embodiment, attention is paid to the arrangement of the convex portions 21, but attention may be paid to the arrangement of the concave portions 22.

  FIG. 4 is a plan view (2) schematically showing irregularities on the surface of the antireflection structure of FIG. FIG. 4A shows an array of grids connecting the bottoms of the recesses, and FIG. 4B shows a part of FIG. In FIG. 4, in order to make the drawing easy to see, the convex portions and the connecting portions are indicated by different dot patterns, the vertexes of the convex portions are indicated by black circles, the bottom points of the concave portions are indicated by white circles, and the grids connecting the bottom points of the concave portions are indicated by bold lines.

As shown in FIG. 4, six concave portions 22-2 to 22-7 having the shortest sum (sum) of arbitrary concave portions 22-1 except the outermost concave portion 22 and the distance from the concave portion 22-1. Are arranged so as to satisfy the following (3) and (4).
(3) A connecting portion between each of the four recesses 22-2, 22-3, 22-5, 22-6 of the six recesses 22-2 to 22-7 and the recess 22-1. 23 exists.
(4) The convex part 21 exists between each of the remaining two concave parts 22-4 and 22-7 of the six concave parts 22-2 to 22-7 and the concave part 22-1.

  “Distance” is the distance between the bottom points 22 a of the recesses 22. When there are a plurality of combinations of the six recesses 22 having the shortest total distance, the above (3) and (4) are established for all the combinations. In the present embodiment, there is only one combination of the six recesses 22 having the shortest total distance.

  5-6 is explanatory drawing (1)-(2) of the manufacturing method of the reflection preventing structure by the 1st Embodiment of this invention. FIG. 5 shows a first step of producing a replica using a prototype, and FIG. 6 shows a second step of producing an antireflection structure using the replica.

  The manufacturing method of the antireflection structure includes a step of manufacturing the antireflection structure 10 having the periodic uneven portions 20 on the surface by using the prototype 50 having the periodic uneven portions 60 on the surface. This step includes, for example, a first step of producing a replica 70 having a concavo-convex portion 80 on which the shape of the concavo-convex portion 60 of the prototype 50 is transferred, and a concavo-convex portion obtained by inverting and transferring the shape of the uneven portion 80 of the replica 70 And a second step of producing the antireflection structure 10 having 20 on the surface. The prototype 50 can be used repeatedly in the first step, and the replica 70 can be used repeatedly in the second step.

  The first step includes, for example, a step of preparing the prototype 50 (see FIG. 5A), and a step of forming a replica 70 by forming a metal film on the uneven portion 60 of the prototype 50 (FIG. 5B). )) And a step of peeling the replica 70 from the master 50 (see FIG. 5C). The replica 70 is formed, for example, by forming a conductive film on the concavo-convex portion 60 of the prototype 50 and then forming a metal film such as Ni on the conductive film by electroforming. As a method for forming the conductive film, PVD methods such as electroless plating, sputtering, and vacuum deposition are used.

  In the second step, for example, a step of applying a curable resin onto the base 12 (see FIG. 6A), and the coating layer 13 is cured in a state where the concavo-convex portion 80 of the replica 70 is pressed against the surface of the coating layer 13. And a step of peeling the replica 70 from the resin layer 14 formed by curing the coating layer 13 (see FIG. 6C). As the curable resin, for example, a thermosetting resin or a photocurable resin is used. As a method for applying the curable resin, for example, a general method such as a spin coating method, a die coating method, or an ink jet method is used.

  In this way, the antireflection structure 10 is manufactured. Since the uneven portion 20 of the antireflection structure 10 has a shape obtained by inverting the shape of the uneven portion 60 of the prototype 50 twice, it has substantially the same shape and substantially the same dimensions as the uneven portion 60 of the prototype 50.

  FIG. 7 is a plan view schematically showing irregularities on the surface of the prototype of FIG. FIG. 7A shows an array of lattices connecting the vertices of the convex portions, and FIG. 7B shows a part of FIG. In FIG. 7, in order to make the drawing easier to see, the convex portions and the connecting portions are indicated by different dot patterns, the vertexes of the convex portions are indicated by black circles, the bottom points of the concave portions are indicated by white circles, and the grids connecting the vertexes of the convex portions are indicated by bold lines.

  As shown in FIG. 7, the concavo-convex part 60 of the prototype 50 is lower than the convex part 61, the concave part 62, and the apex 61 a of the convex part 61, as in the concave-convex part 20 of the antireflection structure 10. It has the connection part 63 which connects predetermined convex parts 61 in the position higher than the point 62a. A plurality of convex portions 61, a plurality of concave portions 62, and a plurality of connecting portions 63 are two-dimensionally arranged.

  The convex portions 61 are periodically arranged, for example, in a regular hexagonal lattice shape, a quasi-hexagonal lattice shape, a regular tetragonal lattice shape, or a quasi-tetragonal lattice shape (in this embodiment, a regular hexagonal lattice shape). In order to increase the filling rate of the convex portions 61, the convex portions 61 are preferably arranged periodically in a hexagonal lattice shape.

  When the convex portions 61 are periodically arranged in a regular hexagonal lattice shape, the distance from the arbitrary convex portion 61-1 is the shortest around the arbitrary convex portion 61-1 excluding the outermost convex portion 61. And six equal convex parts 61-2 to 61-7 are arranged. The vertices of the six convex portions 61-2 to 61-7 are arranged at an equal pitch with an interval of 60 ° around the vertex of the convex portion 61-1, and constitute a regular hexagonal lattice.

In the present embodiment, as shown in FIG. 7, there are six arbitrary convex portions 61-1 excluding the outermost convex portion 61 and the total (sum) of the distances from the convex portions 61-1. The convex portions 61-2 to 61-7 are arranged so as to satisfy the following (5) and (6).
(5) Between each of four convex parts 61-2, 61-3, 61-5, 61-6 of the six convex parts 61-2 to 61-7 and the convex part 61-1. There is a connecting portion 63.
(6) A concave portion 62 exists between each of the remaining two convex portions 61-4 and 61-7 among the six convex portions 61-2 to 61-7 and the convex portion 61-1. .

  In the present embodiment, there is only one combination of six convex portions with the shortest total distance.

  When the above (5) and (6) are established, for example, the convex portion 61 and the connecting portion along two directions (F1 direction and F2 direction) among three directions intersecting with an arbitrary convex portion 61-1. 63 are alternately arranged, and the convex portions 61 and the concave portions 62 are alternately arranged along the remaining one direction (F3 direction). Concave portions 62 and connecting portions 63 are alternately arranged along a direction parallel to the F1 direction.

  Thus, in the prototype 50, the direction in which the convex portions 61 and the concave portions 62 are alternately arranged is different from the direction in which the convex portions 61 and the connecting portions 63 are alternately arranged. Therefore, the height difference between the apex 61a of the convex portion 61 and the bottom point 62a of the concave portion 62, and the predetermined portion of the apex 61a of the convex portion 61 and the connecting portion 63 (corresponding to the predetermined portion 23a of the connecting portion 23 of the antireflection structure 10). It is possible to design the difference in height with respect to the portion). Accordingly, in the antireflection structure 10 shown in FIGS. 1 to 4, the height difference H1 between the vertex 21a of the convex portion 21 and the bottom point 22a of the concave portion 22, the vertex 21a of the convex portion 21 and the predetermined portion 23a of the connecting portion 23, The height difference H2 can be designed independently. Therefore, since the height difference H1 and the height difference H2 can be optimized independently, both low reflectivity and scratch resistance can be achieved.

  In the present embodiment, the concavo-convex portion 20 of the antireflection structure 10 has a shape obtained by inverting the shape of the concavo-convex portion 60 of the prototype 50 twice, but the shape of the concavo-convex portion 60 of the prototype 50 is inverted one or more times. It is only necessary to have a shape, and the coating layer 13 may be cured in a state in which the uneven portion 60 of the prototype 50 is pressed against the surface of the coating layer 13 (see FIG. 6). Regardless of the number of times of reversal transfer, the convex portion 21 of the antireflection structure 10 satisfies the above (1) and (2), so that both low reflectivity and scratch resistance can be achieved.

  FIG. 8 is an explanatory view (3) of the manufacturing method of the antireflection structure according to the first embodiment of the present invention. FIG. 8 shows a process of manufacturing a prototype.

  The method for manufacturing the antireflection structure may further include a step of manufacturing the prototype 50. This step includes, for example, a step of forming a resist film 52 on the substrate 51 (see FIGS. 5 and 6), and a step of changing the light intensity on the surface of the resist film 52 in the first direction (G1 direction). A step of exposing one interference fringe (see FIG. 8A), and a second interference whose light intensity changes on the surface of the resist film 52 in a second direction (G2 direction) intersecting the first direction. A step of exposing the stripes (see FIG. 8B) and a step of developing the resist film 52 after the exposure of the first and second interference fringes.

  The base | substrate 51 (refer FIG.5 and FIG.6) is formed in a sheet form, plate shape, block shape, or roll shape, for example. Although the material of the base | substrate 51 is not specifically limited, For example, a silicon | silicone, quartz glass, soda glass, an alkali free glass etc. are used.

  As a material of the resist film 52, a general material is used, and either a negative type or a positive type can be used. A developing solution is selected according to the material of the resist film 52.

  The first interference fringes are formed by a two-beam interference exposure method. A plurality of photosensitive portions 53 exposed by the first interference fringes are arranged at intervals in the first direction (G1 direction). As a light source for the interference wave, a general laser oscillator such as a He—Cd laser (wavelength: 325 nm) is used.

  The second interference fringes are formed by the two-beam interference exposure method after rotating the resist film 52 in the same manner as the first interference fringes. A plurality of photosensitive portions 54 exposed by the first interference fringes are arranged at intervals in the second direction (G2 direction).

  In the present embodiment, the exposure of the first interference fringe and the exposure of the second interference fringe are performed separately, but may be performed simultaneously.

  The development of the resist film 52 is performed after the exposure of the first and second interference fringes. By developing the resist film 52, a resin layer 56 (see FIG. 5A) having periodic uneven portions 60 on the surface is obtained.

  When the resist film 52 is a negative type, the more strongly exposed part tends to remain after development. Therefore, the intersection 55 between the photosensitive portion 53 and the photosensitive portion 54 becomes the convex portion 61 after development. The convex portion 61 is formed in a tapered shape toward the vertex 61a. The portions other than the intersecting portion 55 of the photosensitive portions 53 and 54 become the connecting portion 63 after development.

  In addition, when the resist film 52 is a positive type, a strongly exposed portion is easily removed by development. Therefore, a crossing portion 55 between the photosensitive portion 53 and the photosensitive portion 54 becomes a concave portion 62 after development. The recess 62 is formed in a tapered shape toward the bottom point 62a. The portions other than the intersecting portion 55 of the photosensitive portions 53 and 54 become the connecting portion 63 after development.

  In this way, the prototype 50 is produced. When the angle θ formed by the first direction and the second direction is 60 °, the convex portions 61 are periodically arranged in a regular hexagonal lattice shape. When the angle θ formed by the first direction and the second direction is 90 °, the convex portions 61 are periodically arranged in a regular tetragonal lattice shape.

  In addition, although the prototype 50 of this embodiment is produced by exposing the interference fringes to the resist film 52 by the two-beam interference exposure method, the production method of the prototype 50 is not particularly limited. For example, the concavo-convex portion 60 may be formed on the surface of the substrate 51 by photolithography, electron beam (EB) drawing, laser drawing, or the like.

[Second Embodiment]
FIG. 9 is a perspective view showing a part of the antireflection structure according to the second embodiment of the present invention. In FIG. 9, contour lines are shown by thin lines in order to express irregularities on the surface of the antireflection structure. FIG. 10 is a plan view schematically showing irregularities on the surface of the antireflection structure of FIG. FIG. 10A shows an array of lattices connecting the vertices of the convex portions, and FIG. 10B shows a part of FIG. In FIG. 10, in order to make the drawing easy to see, the convex portions and the connecting portions are indicated by different dot patterns, the vertexes of the convex portions are indicated by black circles, the bottom points of the concave portions are indicated by white circles, and the lattices connecting the vertexes of the convex portions are indicated by bold lines. FIG. 11 is a view showing irregularities on the surface of the antireflection structure of FIG. 9. 11A is unevenness in the cross section along line AA in FIG. 10, FIG. 11B is unevenness in the cross section along line BB in FIG. 10, and FIG. 11C is C in FIG. The unevenness | corrugation in the cross section along -C line | wire is shown.

  The antireflection structure 110 is a so-called moth-eye type, and includes a base 112 and a resin layer 114 formed on the base 112 as in the first embodiment, as shown in FIG. Periodic uneven portions 120 are formed on the surface of the resin layer 114. Note that the antireflection structure 110 may be formed of only the resin layer 114.

  The concavo-convex part 120 includes a convex part 121, a concave part 122, and a connecting part 123 that connects the predetermined convex parts 121 to each other at a position lower than the vertex 121 a of the convex part 121 and higher than the bottom point 122 a of the concave part 122. A plurality of convex portions 121, a plurality of concave portions 122, and a plurality of connecting portions 123 are two-dimensionally arranged.

  The convex portions 121 are periodically arranged in a regular tetragonal lattice shape, for example. “Periodically arranged in the form of a tetragonal lattice” means that, as shown in FIG. 10, the distance from any recess 122 is shortest around any recess 122 except the outermost recess 122. It means that four equal convex portions 121 are arranged. The vertices 121a of the four convex portions 121 are arranged at equal pitches at 90 ° intervals around the bottom point 122a of the concave portion 122, and constitute a regular tetragonal lattice.

  The convex portions 121 may be periodically arranged in a quasi-tetragonal lattice shape. “Periodically arranged in a quasi-tetragonal lattice shape” means periodically arranged in a shape that conforms to a regular tetragonal lattice. The shape conforming to the tetragonal lattice is a shape obtained by distorting a regular tetragonal lattice such as a shape obtained by stretching a regular tetragonal lattice in a predetermined direction. A lattice having a shape obtained by distorting a regular tetragonal lattice may be continuously arranged in a linear shape, a curved shape, or a meandering shape.

In the present embodiment, as shown in FIG. 10, there are six arbitrary convex portions 121-1 excluding the outermost convex portion 121 and the total (sum) of the distances from the convex portions 121-1 being the shortest. The convex portions (for example, convex portions 121-2 to 121-7) are arranged so as to satisfy the following (7) and (8).
(7) Between the four convex portions 121-2, 121-3, 121-5, 121-6 of the six convex portions 121-2 to 121-7 and the convex portion 121-1. There is a connecting portion 123.
(8) A concave portion 122 exists between each of the remaining two convex portions 121-4 and 121-7 among the six convex portions 121-2 to 121-7 and the convex portion 121-1. .

  “Distance” refers to the distance between the vertices 121 a of the convex portions 121. When there are a plurality of combinations of six convex portions with the shortest total distance, the above (7) and (8) are established for all combinations. In this embodiment, there are four convex portions with the shortest and equal distance from the convex portion 121-1, and there are four convex portions with the next shortest and equal distance from the convex portion 121-1. There are six combinations of six convex portions with the shortest total distance from -1. The above (7) and (8) hold for all six combinations.

  When the above (7) and (8) are established, for example, the convex portion 121 and the connecting portion along two directions (the J1 direction and the J2 direction) among the three directions intersecting around the arbitrary convex portion 121-1. 123 are alternately arranged, and the convex portions 121 and the concave portions 122 are alternately arranged along the remaining one direction (J3 direction). The pitch P11 (see FIG. 11A) of the convex portions 121 arranged at intervals in the J1 direction and the J2 direction may be set to a length equal to or shorter than the wavelength of visible light. The pitch P12 (see FIG. 11B) of the protrusions 121 arranged at intervals in the J3 direction is larger than the pitch P11. Concave portions 122 and connecting portions 123 are alternately arranged along a direction parallel to the J1 direction (see FIGS. 10 and 11C).

  Thus, the direction where the convex part 121 and the recessed part 122 are arrange | positioned alternately differs from the direction where the convex part 121 and the connection part 123 are arrange | positioned alternately. Therefore, the height difference H11 (see FIG. 11B) between the vertex 121a of the convex portion 121 and the bottom point 122a of the concave portion 122, the vertex 121a of the convex portion 121, and the predetermined portion 123a of the connecting portion 123 (see FIG. 9). The height difference H12 (see FIG. 11A) can be designed independently. Therefore, the height difference H11 and the height difference H12 can be optimized independently. Here, the predetermined portion 123 a of the connecting portion 123 is the lowest portion between the vertices 121 a of the convex portions 121 and the highest portion between the bottom points 122 a of the concave portions 122.

  In order to optimize the height difference H11 and the height difference H12, first, the range of the pitch P11 may be set. As described above, the pitch P11 is set to a length equal to or shorter than the wavelength of visible light, and may be, for example, 400 nm or less (preferably 300 nm or less). Further, the pitch P11 may be, for example, 50 nm or more (preferably 100 nm or more) from the viewpoint of productivity. Therefore, the pitch P11 may be 50 to 400 nm.

  Next, the range of the aspect ratio of the uneven portion 120 is set. The aspect ratio of the concavo-convex portion 120 is represented by a ratio H11 / P11 between the height difference H11 between the apex 121a of the convex portion 121 and the bottom point 122a of the concave portion 122 and the pitch P11 of the convex portion 121. The aspect ratio H11 / P11 is, for example, 0.5 or more (preferably 0.7 or more, more preferably 1 or more) from the viewpoint of low reflectivity of the antireflection structure 110. The aspect ratio H11 / P11 is, for example, 4 or less (preferably 3 or less, more preferably 2 or less) from the viewpoint of productivity. When the pitch of the convex portion 121 in the J1 direction is different from the pitch of the convex portion 21 in the J2 direction, the aspect ratio is obtained with the shortest pitch. Since the aspect ratio H11 / P11 is 0.5 to 4, the height difference H11 may be, for example, 100 to 500 nm.

  Next, a ratio H12 / H11 between the height difference H11 and the height difference H12 is set. As the ratio H12 / H11 increases, the height of the predetermined portion 123a of the connecting portion 123 decreases, so that the low reflectivity of the antireflection structure 110 improves. The ratio H12 / H11 is, for example, 0.1 or more (preferably 0.2 or more, more preferably 0.3 or more). On the other hand, as the ratio H12 / H11 decreases, the height of the predetermined portion 123a of the connecting portion 123 increases and the convex portion 121 is reinforced, so that the anti-reflection structure 110 has better scratch resistance. The ratio H12 / H11 is, for example, 0.9 or less (preferably 0.7 or less, more preferably 0.5 or less). Since the ratio H12 / H11 is 0.1 to 0.9, the height difference H12 may be, for example, 30 to 300 nm.

  In this embodiment, since the height difference H11 and the height difference H12 can be optimized independently, the aspect ratio H11 / P11 and the ratio H12 / H11 can be optimized independently. Both low reflectivity and scratch resistance are possible.

  In the present embodiment, attention is paid to the arrangement of the convex portions 121. However, the arrangement of the concave portions 122 may be noted, as in the first embodiment.

  Since the manufacturing method of the antireflection structure 110 having the above-described configuration is the same as the manufacturing method of the antireflection structure 10 according to the first embodiment, the description thereof is omitted.

  As mentioned above, although the 1st-2nd embodiment of this invention was described, this invention is not restrict | limited to said embodiment. Various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the present invention.

  For example, a low-reflection layer may be provided on the back surface of the antireflection structure (the surface facing the surface on which the moth-eye type uneven portion is formed). The low reflection layer has translucency. The low reflection layer may reduce the reflectance by the interference action of light, or may reduce the reflectance by absorption of light. The low reflection layer is formed of an organic material and / or an inorganic material. As a method for forming the low reflection layer, dry coating such as PVD method or CVD method, wet coating such as die coating method, spray coating method, ink jet method or spin coating method is used. When the antireflection structure is used for a touch panel, the low reflection layer may be disposed on the outer side and the moth-eye type uneven portion may be disposed on the inner side.

  Moreover, although the convex part of the said embodiment is a taper shape toward the top, a convex part may have a flat top part. In this case, the “distance” in the claims is the distance between the center points of the tops of the convex portions. Similarly, although the recessed part of the said embodiment is tapered toward the bottom point, the recessed part may have a flat bottom part.

  EXAMPLES The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to these examples.

[Example 1]
In Example 1, a model for analysis of the antireflection structure having the uneven portions shown in FIGS. 1 to 3 on the surface was prepared, and simulation analysis was performed using a computer.

  As shown in FIG. 12, the analysis model was prepared by overlapping two ridge portions 91 having a sinusoidal cross section on a virtual plane 92 (only one is shown in FIG. 12). It is considered that when the interference fringes are exposed to the resist film once and developed, an uneven surface having a sinusoidal cross section is formed. The overlapping portion of the two protruding strip group 91 corresponds to the protruding portion 21 shown in FIGS. The crossing angle of the two convex stripe groups 91 was set to 60 ° so that the convex portions were periodically arranged in a regular hexagonal lattice pattern. The height difference H1 (see FIG. 3B) between the vertex of the convex portion and the bottom point of the concave portion (virtual plane 92) is 300 nm, and the height difference H2 between the vertex of the convex portion and a predetermined portion of the connecting portion (FIG. 3A). )) Was 150 nm, and the pitch P1 of the protrusions (see FIGS. 3A and 3B) was 250 nm. As a physical property value (for example, a refractive index, a Young's modulus, etc.) of the ridge portion group 91, a physical property value of an acrylic resin was used.

  The reflectance on the concavo-convex portion of the analysis model was analyzed by the FDTD method (finite difference time domain method). As the analysis software, “Poying for Optics” manufactured by CYBERNET was used. The results are shown in FIG. In FIG. 14, the horizontal axis represents the light wavelength, and the vertical axis represents the light reflectance. Moreover, in FIG. 14, L1 represents the analysis result of Example 1, L11-L13 represents the analysis result of Comparative Examples 1-3 mentioned later. In the reflectance analysis, the surface of the substrate having a thickness of 0.7 μm was used instead of the virtual plane 92. As the physical property value (for example, the refractive index) of the substrate, the physical property value of the acrylic resin was used in the same manner as the physical property value of the protruding strip group 91.

  As the scratch resistance of the analysis model, the maximum stress generated in the convex portion when an external force in a direction perpendicular to the height direction of each convex portion is applied to the vertex of each convex portion was analyzed by a finite element method. “Solid Works Simulation” manufactured by Solid Works was used as the analysis software. A smaller maximum stress means higher scratch resistance. Table 1 shows the relative value of the maximum stress (the maximum stress of Comparative Example 1 described later is 1). The reason for the relative value is that the length of the model for stress analysis (for example, height difference H1, H2, pitch P1, etc.) is set to 1000 times the actual length due to software restrictions.

[Comparative Example 1]
In Comparative Example 1, a model for analysis of an antireflection structure having a concavo-convex portion similar to the conventional one was produced, and simulation analysis was performed using a computer in the same manner as in Example 1.

  As shown in FIG. 13, the analysis model is arranged on the virtual plane 92 periodically in a regular hexagonal lattice pattern at a pitch of 250 nm (see FIG. 13A, in FIG. 13). Only the three truncated cones 93 are shown), and the corners of the top surface 93b and the tapered surface 93c of each truncated cone 93 are rounded, and the tip portion is formed by a protrusion 94 composed of a part of a spherical surface (FIG. 13). (See (B)). The height (the height difference between the bottom surface 94a and the apex 94b) H21 of the protrusion 94 was set to 300 nm, and the pitch P21 of the apex 94b of the protrusion 94 was set to 250 nm. The radius R of the bottom surface 94a was set to 120 nm so that the bottom surfaces 94a of the protrusions 94 were separated from each other. The radius r of the cut surface when the protrusion 94 was cut at the center in the height direction was 94 nm. An angle α (see FIG. 13A) formed by the bottom surface 93a of the truncated cone 93 and the tapered surface 93c was set to 80 °. As the physical property values (for example, refractive index and Young's modulus) of the protrusions 94, the physical property values of acrylic resin were used. FIG. 14 shows the analysis result of the light reflectance, and Table 1 shows the analysis result of the stress.

[Comparative Example 2]
In Comparative Example 2, the angle α (see FIG. 13A) formed by the bottom surface 93a of the truncated cone 93 and the tapered surface 93c is 70 °, the radius R of the bottom surface 94a of the protrusion 94 is 150 nm, and FIG. The analysis model of the antireflection structure is produced in the same manner as in Comparative Example 1 except that the bottom surfaces 94a of the protrusions 94 are partially overlapped to form the flanges 95 between the apexes 94b of the protrusions 94 as shown in FIG. In the same manner as in Example 1, simulation analysis was performed using a computer. The height difference H22 between the apex 94b of the protrusion 94 and the flange 95 is 160 nm, and the radius r of the cut surface when the protrusion 94 is cut at the center in the height direction is 124 nm. FIG. 14 shows the analysis result of the light reflectance, and Table 1 shows the analysis result of the stress.

[Comparative Example 3]
In Comparative Example 3, the height difference H22 between the apex 94b of the protrusion 94 and the flange 95 is set by setting the angle α (see FIG. 13A) formed by the bottom surface 93a of the truncated cone 93 and the tapered surface 93c to 80 °. A model for analysis of the antireflection structure was prepared in the same manner as in Comparative Example 2 except that the thickness was set to 230 nm, and simulation analysis was performed using a computer in the same manner as in Example 1. The radius r of the cut surface when the protrusion 94 was cut at the center in the height direction was 95 nm. FIG. 14 shows the analysis result of the light reflectance, and Table 1 shows the analysis result of the stress.

図１４及び表１から、実施例１の構造は、比較例１〜３の構造と異なり、低反射性及び耐擦傷性の両方を有していることがわかる。比較例１では、突起部９４の底面９４ａ同士が離れており、鞍部９５が形成されないため、耐擦傷性が悪い。比較例２及び比較例３では、反射防止構造体の凹凸部が上記の（１）及び（２）を満たしておらず、低反射性が悪い。比較例２及び比較例３では、鞍部９５が形成されるように突起部９４の底面９４ａ同士が一部重なるので、反射防止構造体の凹部の底点が仮想平面９２から離れ、凹部の底点と凸部の頂点との高低差が小さくなるためである。

14 and Table 1, it can be seen that the structure of Example 1 has both low reflectivity and scratch resistance, unlike the structures of Comparative Examples 1 to 3. In Comparative Example 1, since the bottom surfaces 94a of the protrusions 94 are separated from each other and the flange portion 95 is not formed, the scratch resistance is poor. In Comparative Example 2 and Comparative Example 3, the uneven portion of the antireflection structure does not satisfy the above (1) and (2), and the low reflectivity is poor. In Comparative Example 2 and Comparative Example 3, the bottom surfaces 94a of the protrusions 94 partially overlap each other so that the flange portion 95 is formed, so that the bottom point of the concave portion of the antireflection structure is separated from the virtual plane 92, This is because the difference in height between the top and the top of the convex portion becomes small.

DESCRIPTION OF SYMBOLS 10 Antireflection structure 20 Concavity and convexity 21 Convex part 21a Vertex 22 Concave part 22a Bottom point 23 Connecting part 23a Predetermined part 50 of connecting part Original 51 Base 52 Resist film 53, 54

Claims (9)

In the antireflection structure having periodic irregularities on the surface,
Arbitrary convex portions excluding the outermost convex portion and the six convex portions having the shortest sum of the distances from the arbitrary convex portions are (1) four of the six convex portions. Between each of the convex portions and the arbitrary convex portion, there is a connecting portion that connects the convex portions at a position lower than the top of the convex portion and higher than the bottom point of the concave portion, and (2) the six An antireflection structure, wherein a concave portion exists between each of the remaining two convex portions of the convex portions and the arbitrary convex portion.   Among the three directions intersecting with the arbitrary convex portion as the center, the convex portions and the connecting portions are alternately arranged along two directions, and the convex portions and the concave portions are arranged along the remaining one direction. The antireflection structure according to claim 1, wherein the antireflection structures are arranged alternately.   The antireflection structure according to claim 1, wherein the convex portions are periodically arranged in a regular hexagonal lattice shape.   The antireflection structure according to claim 1, wherein the convex portions are periodically arranged in a regular tetragonal lattice shape. In the manufacturing method of the antireflection structure having the step of manufacturing the antireflection structure having the periodic irregularities on the surface, using the prototype having the periodic irregularities on the surface,
In the prototype, any convex portion excluding the outermost convex portion and the six convex portions having the shortest total distance from the arbitrary convex portion are (1) of the six convex portions. Between each of the four convex portions and the arbitrary convex portion, there is a connecting portion that connects the convex portions at a position lower than the vertex of the convex portion and higher than the bottom point of the concave portion, (2) Manufacturing of an antireflection structure, characterized in that a concave portion exists between each of the remaining two convex portions of the six convex portions and the arbitrary convex portion. Method.   Among the three directions intersecting with the arbitrary convex portion as the center, the convex portions and the connecting portions are alternately arranged along two directions, and the convex portions and the concave portions are arranged along the remaining one direction. The manufacturing method of the antireflection structure according to claim 5 arranged alternately. Further comprising the step of producing the prototype,
The process
Forming a resist film on the substrate;
Exposing the surface of the resist film with a first interference fringe whose light intensity varies along a first direction;
Exposing the surface of the resist film with a second interference fringe whose light intensity varies along a second direction intersecting the first direction;
The method for manufacturing an antireflection structure according to claim 5, further comprising: developing the resist film after the exposure of the first and second interference fringes.   The method for manufacturing an antireflection structure according to claim 7, wherein an angle formed by the first direction and the second direction is 60 °.   The method for manufacturing an antireflection structure according to claim 7, wherein an angle formed by the first direction and the second direction is 90 °.

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