component

Abstract

To provide a member which is excellent in antireflection performance and contains a resin base material without using a vacuum process.SOLUTION: A member has a resin base material 1 having a fine uneven structure thereon, and a porous layer 2 which is positioned on the resin base material 1 on the fine uneven structure side and is composed of a porous material containing particles, wherein the porous layer 2 is composed of a filling part 2a where the cavity of the fine uneven structure is filled with the porous material, and a surface layer 20b on the fine even structure, in the fine uneven structure, columnar projections 1a or columnar recesses are periodically arranged in a two-dimensional manner, the thickness of the surface layer 20b is 80 nm or more and 150 nm or less, intervals between the projections 1a or the recesses are 20 nm or more and 300 nm or less, and the heights of the projections 1a or the depths of the recesses are 10 nm or more and 120 nm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a component that has an anti-reflective structure and is used as an optical element. [Background technology]

[0002] In recent years, plastic lenses have become widely used due to their lower cost compared to glass materials, lighter weight, and superior impact resistance. Lenses require an anti-reflective coating to reduce surface reflection, and as described in Patent Document 1, a multilayer anti-reflective coating of metal oxide formed by vapor deposition is common. Patent Document 2 describes a method for forming an anti-reflective layer using a coating solution in which hydrolysates of silane compounds and silica-based fine particles are dispersed in an organic solvent. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2005-241740 [Patent Document 2] Japanese Patent Publication No. 2008-116348 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, multilayer anti-reflective coatings produced by vapor deposition, such as those described in Patent Document 1, require a vacuum process, resulting in a long cycle time. Coating films like those described in Patent Document 2 are preferable because they do not require a vacuum process, but their anti-reflective performance is not entirely satisfactory. The objective of this invention is to realize a component including a resin substrate with excellent anti-reflective properties without using a vacuum process. [Means for solving the problem]

[0005] The first aspect of the present invention is a member comprising a resin substrate having a fine uneven structure on its surface, and a porous layer made of a porous material containing particles, located on the resin substrate on the side with the fine uneven structure, The porous layer consists of a filling portion in which the porous material is filled into the voids of the fine uneven structure, and a surface layer on the fine uneven structure. The aforementioned fine uneven structure has columnar protrusions or columnar recesses arranged periodically in a two-dimensional manner. The thickness of the aforementioned surface layer is 80 nm or more and 150 nm or less. The distance between the protrusions or recesses is 20 nm or more and 300 nm or less, and the height of the protrusions or the depth of the recesses is 10 nm or more and 120 nm or less. [Effects of the Invention]

[0006] According to the present invention, a component including a resin substrate with excellent anti-reflective properties can be realized without using a vacuum process. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of an embodiment in which the component of the present invention is used as an optical element. [Figure 2] This is a schematic cross-sectional view showing the basic configuration of the component of the present invention. [Figure 3] This is a schematic perspective view showing an example of a fine uneven structure of a resin substrate according to the present invention. [Figure 4] This is a schematic cross-sectional view showing the porous layer of the anti-reflective structure according to the present invention. [Figure 5] This is a schematic cross-sectional view of another embodiment of the member of the present invention. [Figure 6] This is a schematic cross-sectional view showing the process for manufacturing a mold for a resin substrate according to the present invention. [Figure 7] This is a schematic cross-sectional diagram illustrating the injection molding process of a resin substrate according to the present invention. [Figure 8] This is a schematic diagram showing the refractive index model of the component of the present invention. [Modes for carrying out the invention]

[0008] The present invention relates to a member having a resin substrate with a fine concavo-convex structure on its surface and a porous layer made of a porous material located on the resin substrate on the fine concavo-convex structure side. In the present invention, the porous layer includes particles and consists of a filling portion in which the porous material is filled in the voids of the fine concavo-convex structure and a surface layer on the fine concavo-convex structure. The fine concavo-convex structure is formed by periodically arranging columnar convex portions or columnar concave portions two-dimensionally. Further, the thickness of the surface layer is 80 nm or more and 150 nm or less, the interval between the convex portions or concave portions of the fine concavo-convex structure is 20 nm or more and 300 nm or less, and the height of the convex portion or the depth of the concave portion is 10 nm or more and 120 nm or less.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and modifications and improvements can be appropriately made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention, and such modified and improved embodiments are also included in the scope of the present invention.

[0010] FIG. 1(a) is a schematic cross-sectional view in the thickness direction of an embodiment in which the member of the present invention is used as an optical element. Such an optical element includes an antireflection structure 20 on at least one surface of the base material layer 10. FIG. 1(a) is a configuration example having the antireflection structure 20 on both surfaces of the base material layer 10. Further, FIG. 1(b) is a schematic cross-sectional view in the thickness direction of another embodiment, which is an optical element in which the base material layer 10 is laminated on a glass base material generally called a replica lens, and the base material layer 10 is laminated on both surfaces of the glass base material 30, and an antireflection structure 20 is provided on its surface.

[0011] FIG. 2 is a schematic cross-sectional view in the thickness direction showing the basic configuration of the member of the present invention. The member of the present invention includes a resin substrate 1 and a porous layer 2, and the antireflection structure 20 refers to a portion composed of the fine concavo-convex structure and the porous layer 2 in a member in which the resin substrate 1 having a fine concavo-convex structure on its surface has the porous layer 2 on the fine concavo-convex structure side. [[ID=十六]] The fine concavo-convex structure formed on the surface of the resin substrate 1 according to the present invention has portions that are recessed columnarly or protrude columnarly with respect to the reference plane B, as shown in the perspective views of FIGS. 3(a) and (b). Hereinafter, the portion that protrudes columnarly is referred to as the convex portion 1a, and the portion that is recessed columnarly is referred to as the concave portion 1b.

[0012] The porous layer 2 according to the present invention is made of a porous material. In FIG. 2, the porous material is filled in the gaps between a plurality of convex portions 1a protruding from the reference plane B of the fine concavo-convex structure to constitute the filled portion 2a. Further, the porous material is also disposed on the fine concavo-convex structure to constitute the surface layer 20b. That is, the porous layer 2 is composed of the surface layer 20b and the filled portion 2a. In the present invention, the region composed of the fine concavo-convex structure and the filled portion 2a, that is, the region composed of the convex portion 1a of the resin substrate 1 and the filled portion 2a of the porous layer 2 is, for convenience, referred to as the composite layer 20a. Therefore, it can be said that the antireflection structure 20 is composed of the composite layer 20a and the surface layer 20b.

[0013] When the resin substrate 1 according to the present invention has a portion that is recessed columnarly as shown in FIG. 3(a) as the concave portion 1b, the porous material is filled in the concave portion 1b to constitute the filled portion 2a. Further, the porous material is also disposed on the fine concavo-convex structure to constitute the surface layer 20b. That is, similar to FIG. 2, the porous layer 2 is composed of the surface layer 20b and the filled portion 2a. In the present invention, the region composed of the fine concavo-convex structure and the filled portion 2a, that is, the region composed of the resin substrate 1 between the concave portions 1b and the filled portion 2a of the porous layer 2 is, for convenience, referred to as the composite layer 20a. Therefore, it can be said that the antireflection structure 20 is composed of the composite layer 20a and the surface layer 20b.

[0014] The base material layer 10 illustrated in FIGS. 1(a) and (b) is the portion of the resin substrate 1 excluding the convex portion 1a when the resin substrate 1 has the columnar convex portion 1a as shown in FIG. 3(b), and the reference plane B corresponds to the surface of the base material layer 10. In this case, it can be said that the resin substrate 1 is composed of the base material layer 10 and the convex portion 1a. When the resin substrate 1 has the columnar concave portion 1b as shown in FIG. 3(a), it is the portion of the resin substrate 1 excluding the depth portion of the concave portion 1b from the reference plane B. In this case, it can be said that the resin substrate 1 is composed of the base material layer 10 and the portion between the concave portions 1b.

[0015] [Fine uneven structure] The refractive index of the composite layer 20a is determined by the volume ratio of the filler portion 2a in the composite layer 20a. That is, the refractive index can be adjusted by the fine uneven structure, and is appropriately adjusted to reduce the reflectivity depending on the refractive index of the resin substrate 1 and the refractive index of the porous material of the filler portion 2a. Preferably, the volume ratio of the filler portion 2a in the composite layer 20a is 30% to 50%.

[0016] As shown in the perspective views of Figures 3(a) and 3(b), the micro-textured structure according to the present invention has portions that are recessed or protruding in a columnar shape relative to the reference surface B of the resin substrate 1. Hereinafter, the protruding portions will be referred to as convex portions 1a, and the recessed portions as concave portions 1b. The columnar convex portions 1a or columnar concave portions 1b are arranged periodically in a two-dimensional manner. The cross-sectional shape of the convex portions 1a or concave portions 1b (the shape in the cross-section perpendicular to the central axis of the columnar shape) may be circular or polygonal, and convex portions 1a or concave portions 1b of different shapes may be mixed. For ease of manufacturing, it is preferable to have convex portions 1a or concave portions 1b of substantially the same shape.

[0017] Furthermore, the planar arrangement of the convex portions 1a or concave portions 1b can be either a grid pattern with multiple rows of convex portions 1a or concave portions 1b arranged in multiple columns, or a triangular lattice arrangement where the convex portions 1a or concave portions 1b are located at the vertices of equilateral triangles. In Figure 3(a), the columnar concave portions 1b are arranged in a triangular lattice, and in Figure 3(b), the columnar convex portions 1a are arranged in a triangular lattice. In the present invention, the convex portion 1a or concave portion 1b may be substantially columnar, and for manufacturing purposes, the side surface may be slightly inclined, and the angle (opening angle) of the side surface with respect to the central axis of the columnar shape may be 5° or less.

[0018] In this invention, the height of the protrusions 1a or the depth of the recesses 1b, i.e., the thickness Ds of the composite layer 20a, is 10 nm or more and 120 nm or less. Furthermore, the spacing (pitch) P between the protrusions 1a or recesses 1b is preferably 20 nm or more and less than or equal to half the wavelength of the target light, and therefore, for visible light, it is 20 nm or more and 300 nm or less. Within this range, a good anti-reflective effect can be obtained in visible light. It is desirable that the height of the protrusions 1a or the depth of the recesses 1b, and the spacing between the protrusions 1a or recesses 1b, be uniform, but they may vary within the above range.

[0019] [Porous layer] Figure 4 is a schematic cross-sectional view in the thickness direction showing the porous layer according to the present invention. The porous layer 2 is made of a porous material containing particles and has a two-layer structure consisting of a filling portion filled in the recesses 1b of the fine uneven structure and a surface layer 20b on the fine uneven structure. Although Figure 4 shows an example in which recesses 1b are provided as the fine uneven structure, the same applies when protrusions are provided.

[0020] In the porous layer 2, the particles 31 and 34 contained in the porous material are bound together by a binder 32, and voids 33 are formed between the particles to create a porous structure. Figure 4(a) shows a form in which the particles are chain-like particles 31, and Figure 4(b) shows a form in which both chain-like particles 31 and hollow particles 34 are used as particles.

[0021] The refractive index of the porous layer 2 is preferably 1.15 or more and 1.30 or less, and more preferably 1.18 or more and 1.26 or less. A refractive index of 1.15 or more ensures the mechanical strength of the porous layer 2, and a refractive index of 1.30 or less sufficiently reduces the refractive index difference between air and the resin substrate 1, thereby obtaining a sufficient anti-reflective effect.

[0022] The thickness Da of the surface layer 20b of the porous layer 2 is 80 nm to 150 nm, preferably 120 nm or less. Furthermore, the depth Ds of the recesses 1b of the fine uneven structure (= height of the protrusions = thickness of the composite layer 20a) is 10 nm to 120 nm, as described above.

[0023] The composite layer 20a is particularly effective in improving anti-reflective performance by interfering with the upper surface layer 20b, and also improves scratch resistance. When a porous layer 2 is provided on the surface of a smooth resin substrate 1 that does not have a fine uneven structure, peeling of the porous layer 2 is likely to occur at the interface between the porous layer 2 and the resin substrate 1. In the present invention, the porous material filled in the recesses of the fine uneven structure acts as an anchor, making it difficult for the porous layer 2 to peel off and resulting in high scratch resistance.

[0024] (particle) Inorganic particles are preferably used as the particles contained in the porous layer 2. Specifically, examples include silicon dioxide particles, magnesium fluoride particles, lithium fluoride particles, calcium fluoride particles, and barium fluoride particles, with silicon dioxide particles being preferred. Examples of particle shapes include chain-like, cocoon-like, spherical, disc-like, rod-like, needle-like, and angular. When lowering the refractive index of the porous layer 2, chain-like particles or hollow particles having pores surrounded by a shell are preferred.

[0025] The chain-like particles are obtained as silicon oxide particles and are secondary particles consisting of multiple spherical primary particles linked together in a straight or bent pattern. The primary particles constituting the chain-like particles may be in a state where the individual shapes are clearly observable, or in a state where their shapes are distorted due to fusion with each other, but it is preferable that the individual shapes are clearly observable. The primary particles constituting the chain-like particles may be perfectly spherical, cocoon-shaped, or barrel-shaped, but cocoon-shaped or barrel-shaped particles are particularly preferred, and particles with a short axis of 8 nm to 20 nm and a long axis of 1.5 to 3.0 times the short axis are particularly preferred.

[0026] The thickness of the chain-like particles corresponds to the average particle diameter of a single primary particle. The average particle diameter of the primary particles can be calculated from the specific surface area obtained by nitrogen adsorption for chain-like particles extracted from the coating solution. The average particle diameter of the primary particles constituting the chain-like silicon oxide particles is preferably between 8 nm and 20 nm. When the average particle diameter is 8 nm or more, the surface area of ​​the chain-like particles is appropriately suppressed, eliminating the risk of reduced film reliability due to the incorporation of moisture and chemical substances from the atmosphere. Furthermore, when the average particle diameter is 20 nm or less, dispersion in the solvent becomes stable, and good coating properties are obtained.

[0027] The average particle diameter of the chain-like particles corresponds to the Ferret diameter of the secondary particles, and can be determined by dynamic light scattering if the particles are in the coating solution. The average particle diameter of the chain-like particles is preferably 4 to 8 times the average particle diameter of the primary particles. If the average particle diameter of the chain-like particles is 4 times or more the average particle diameter of the primary particles, the film will not become too dense, and the refractive index can be sufficiently reduced. If it is 8 times or less, the viscosity of the coating solution will be within an appropriate range, resulting in good coating and leveling properties. Furthermore, the average particle diameter of the primary particles constituting the chain-like silicon dioxide particles contained in the porous layer 2 can be calculated from transmission electron microscope or scanning electron microscope images.

[0028] As a method for producing hollow particles, in the case of silicon dioxide particles, known methods described in Japanese Patent Publication No. 2001-233611 and Japanese Patent Publication No. 2008-139581 can be used. In the case of magnesium fluoride particles, known methods described in Japanese Patent Publication No. 2012-76967 and Japanese Patent Publication No. 2015-145325 can be used.

[0029] The average particle diameter of hollow particles is preferably between 15 nm and 300 nm, and more preferably between 30 nm and 80 nm. If the average particle diameter is 15 nm or more, the particles can be manufactured stably, and if the average particle diameter is 300 nm or less, the voids generated between the particles are not very large, and scattering by the particles is suppressed.

[0030] The average particle diameter of hollow particles is the average Ferret diameter. This average Ferret diameter can be measured by image processing of images obtained by observing particles contained in the coating solution or particles contained in the porous layer 2 using a transmission electron microscope. Commercially available image processing software such as image Pro PLUS (manufactured by Media Cybernetics, Inc.) can be used for image processing. In a predetermined image area, the contrast can be adjusted as needed, the Ferret diameter of each particle can be measured by particle measurement, and the average value of multiple particles can be calculated to obtain the average Ferret diameter.

[0031] The shell thickness of the hollow particles is 10% to 50% of the average particle diameter, preferably 20% to 35%. If the shell thickness is 10% or more, the strength of the particles themselves is sufficient, and if the shell thickness is 50% or less, the ratio of voids to the volume occupied by the particles is large, allowing for the formation of a porous layer 2 with a refractive index of 1.30 or less, which is the effect of using particles. The average particle diameter of particles other than chain-like particles and hollow particles can be determined by dynamic light scattering in the coating solution. In the porous layer 2, the Ferret diameter of multiple particles can be measured from transmission electron microscope or scanning electron microscope images, and the average value of these measurements can be used as the average Ferret diameter.

[0032] (binder) The binder 32 that binds particles 31 and 34 together is preferably made of the same inorganic material if particles 31 and 34 are inorganic particles. Using the same material increases the bonding strength between particles and makes it possible to create a porous layer that is less susceptible to deterioration depending on the environment in which it is used. For this reason, when silicon dioxide particles are used as particles, the binder is preferably a silicon dioxide compound. A preferred example of a silicon dioxide compound is a cured product of a silicon dioxide oligomer obtained by hydrolysis and condensation of a silicate ester.

[0033] The amount of binder in the porous layer 2 is preferably 0.2 parts by mass or more and 20 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 8 parts by mass or less, per 100 parts by mass of particles contained in the porous layer 2. If the amount of binder is 0.1 parts by mass or more, the bonding between particles is sufficient and the porous layer 2 can obtain sufficient strength. If it is 20 parts by mass or less, the binder does not disrupt the arrangement of the particles, and the porous layer 2 can achieve a low refractive index due to good scattering with respect to visible light.

[0034] The component of the present invention may optionally have a functional layer 3, such as an antifouling layer or a hydrophilic layer, on the porous layer 2, i.e., on the surface opposite to the resin substrate 1, as shown in Figure 5. Examples of antifouling layers include a layer containing a fluoropolymer, a fluorosilane monolayer, and a layer containing titanium dioxide particles. A hydrophilic polymer layer is preferred for the hydrophilic layer, and a layer containing a polymer having amphoteric hydrophilic groups such as sulfobetaine groups, carbobetine groups, and phosphoroline groups is particularly preferred.

[0035] The components of the present invention can be preferably used as optical elements such as lenses, mirrors, filters, and functional films. In particular, they can be used in display devices and imaging devices that require high durability and high-performance anti-reflective properties. Among these, lenses and filters for head-mounted displays (HMDs) that require weight reduction are especially suitable.

[0036] [Manufacturing method] The method for manufacturing the component of the present invention will be described below. (Resin base material) Resin substrates with a micro-textured surface can be manufactured by injection molding or imprinting using a mold with an inverted micro-textured surface. In the case of lenses, it is necessary to manufacture a mold with a micro-textured surface on a curved surface. The manufacturing process of a mold with an inverted micro-textured surface is shown in Figure 6. Figure 6 is a schematic cross-sectional view in the thickness direction. By this method, a micro-textured surface can be formed on the mirror-like surface of the mold, and the refractive index and thickness of the composite layer can be controlled.

[0037] As shown in Figure 6(a), the mold for forming the fine uneven structure involves growing a NiP plating film 42 on a substrate 41 made of Starbucks material, and then smoothing the surface. Next, after cleaning the surface of the plating film 42, a uniform SiO2 film 43 with a thickness of 100 nm to 300 nm is deposited on the surface by sputtering. In sputtering, a Si target is used and the ratio of Ar gas and O2 gas is finely adjusted to deposit the film. In order to control the etching depth of the SiO2 film 43 in the subsequent dry etching process by the etching selectivity ratio of the film composition, a Si-rich film is formed on the side of the SiO2 film 43 that is close to the plating film 42. On the side far from the plating film 42, an SiO2 film with a thickness equal to or greater than the height of the convex parts or the depth of the concave parts of the fine uneven structure is formed.

[0038] As shown in Figure 6(b), a photoresist 44 is applied to the SiO2 film 43 by spin coating to ensure uniform film thickness, and then a drying treatment such as pre-baking is performed.

[0039] On the photoresist 44, patterns corresponding to the convex or concave parts of the uneven structure are drawn using electron beam lithography so as to be normal to the mirror-like curved surface. Electron beam lithography allows adjustment of the cross-sectional shape, size, and spacing of the convex or concave parts of the fine uneven structure, i.e., the refractive index of the composite layer. The thickness of the photoresist 44 used in the drawing process is related to the fine uneven structure formed on the mirror-like surface; specifically, if the height is 80 nm, a thickness of 60 nm or more is required based on the selectivity ratio in dry etching. Furthermore, depending on the specifications of the drawing equipment, the interfacial reflection of the photoresist 44 is reduced as needed by bark or turk treatment.

[0040] After the mold is immersed in a developing solution to form the drawn pattern, a post-bake treatment is performed to create a pattern on the photoresist 44 on the SiO2 film 43 that is similar to the fine uneven structure formed by dry etching but reduced in height (Figure 6(c)).

[0041] As shown in Figure 6(d), the SiO2 film 43 is etched by dry etching using CHF3 gas with the photoresist 44 as a mask, to the height of the protrusions or the depth of the recesses, thereby forming a fine uneven structure that is inverted on the mirror-like surface. The height of the protrusions or the depth of the recesses can be controlled by the film thickness of the SiO2 film 43 and the dry etching time.

[0042] After dry etching, an ashing treatment with oxygen gas is performed to remove the residue of the photoresist 44, and a mirror-finish injection mold having an SiO2 film 43 with an inverted fine uneven structure is fabricated (Figure 6(e)).

[0043] Next, the manufacturing method of a resin substrate by injection molding using the mold produced in the process shown in Figure 6 will be explained with reference to Figure 7. Figure 7 is a schematic cross-sectional view in the thickness direction of the manufacturing process of the component shown in Figure 1(a).

[0044] When constructing a component having an anti-reflective structure 20 on both sides of a base layer 10, molds 61a and 61b are prepared, each having an inverted micro-textured structure on both sides, as shown in Figure 7(a), so that a micro-textured structure is formed on both sides. The molds 61a and 61b are incorporated into the fixed and movable molds 62a and 62b of the injection molding apparatus, respectively, but either can be used as the fixed side. If the surface of the resin base material 1 is curved, the convex or concave parts of the micro-textured structure are formed along the direction normal to the curved surface.

[0045] Next, as shown in Figure 7(b), uncured resin 63 is injected into the gap between molds 61a and 61b. Thermoplastic resins such as cycloolefin polymer resin, polycarbonate resin, and polymethacrylate acrylic resin, which have low water absorption, can be used as the resin for injection molding. Among these, it is preferable to use cycloolefin resin, which has low water absorption. When using cycloolefin resin, the molten resin temperature is preferably 250°C to 290°C, the mold temperature is preferably 125°C to 140°C, and the holding pressure is preferably 20 MPa to 90 MPa.

[0046] After the molded resin temperature has cooled to a temperature below the glass transition temperature, the molded product is demolded using an ejector pin to prevent tilting, as shown in Figure 7(c), and a resin substrate 1 having a fine uneven surface structure on both sides is obtained.

[0047] When injection molding a lens with a small opening angle (a lens that is nearly flat), for example, if the optical axis of the lens is the direction of demolding, the height of the protrusions or the depth of the recesses of the micro-textured structure can be formed without any problems. However, in the case of a lens with a large opening angle, if the central axis of the columnar protrusions or recesses of the micro-textured structure formed on the molds 61a and 61b is not parallel to the optical axis when demolding, the micro-textured structure may deform, resulting in a structural distribution that significantly changes the reflectivity. However, in the present invention, since the height of the protrusions or the depth of the recesses is 120 nm or less, the strain during demolding can be absorbed by the elastic deformation of the resin substrate 1, so there is no problem.

[0048] (Porous layer) Next, we will describe the coating liquid used in the manufacture of the porous layer, and then we will describe the method for manufacturing the anti-reflective structure.

[0049] <Coating liquid> The coating liquid for forming the porous layer 2 contains particles constituting the porous material, a binder component that binds the particles together, and an organic solvent. Uniform dispersion of the particles in the coating liquid and a slow drying rate of the solvent after application allow for uniform filling of the particles between the protrusions or depressions of the fine uneven structure. If the particles are aggregated due to the influence of the dispersion medium or binder component, they will have difficulty penetrating between the fine protrusions or depressions. Furthermore, if there is a significant difference in drying rate between the side with the fine uneven structure and the opposite side during the drying process after application of the coating liquid, the filling of particles between the protrusions or depressions of the fine uneven structure will be insufficient, and the voids within the filled areas will tend to become larger. Moreover, larger voids between the protrusions or depressions weaken the anchoring effect of the porous layer 2, resulting in reduced scratch resistance.

[0050] The binder is preferably made of the same material as the particles. Therefore, when silicon dioxide particles are used as the particles, the binder is preferably a silicon dioxide compound. Although silicon dioxide particles have silanol (Si-OH) groups on their surface, the number of silanol groups on the surface can be further increased by mixing them with silicon dioxide oligomers in the coating solution. As a result, it becomes possible to create a surface state in which the particles are more easily bonded together. When the coating solution is applied and dried, the silicon dioxide oligomers bond multiple particles together, thus realizing a highly scratch-resistant porous layer 2.

[0051] In the coating liquid according to the present invention, the content of the binder component is the same as that of the porous layer 2 described above.

[0052] Any organic solvent that can be used in the coating solution is acceptable as long as it does not cause particle precipitation or rapid thickening of the coating solution. Examples of solvents include: monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol, 1-heptanol, 2-heptanol, 1-octanol, and 2-octanol; and dihydric or higher alcohols such as ethylene glycol and triethylene glycol. Ether alcohols such as methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol, and 3-methoxy-1-butanol; ethers such as dimethoxyethane, diglyme (diethylene glycol dimethyl ether), tetrahydrofuran, dioxane, diisopropyl ether, dibutyl ether, and cyclopentyl methyl ether; esters such as ethyl formate, ethyl acetate, n-butyl acetate, methyl lactate, ethyl lactate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, and propylene glycol monomethyl ether acetate; various aliphatic or alicyclic hydrocarbons such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane; and various aromatic hydrocarbons such as toluene, xylene, and ethylbenzene. Various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone. Various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, and tetrachloroethane. Aprotic polar solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and ethylene carbonate.It is also possible to mix and use two or more of these solvents.

[0053] From the viewpoint of particle dispersibility and coating liquid applicability, it is preferable that 30% by mass or more of the solvent contained in the coating liquid is a water-soluble solvent having hydroxyl groups with 4 to 6 carbon atoms and a high boiling point. In particular, it is especially preferable that the coating liquid contains at least one solvent selected from ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ethyl lactate, and 3-methoxy-1-butanol.

[0054] <Preparation of porous layer> The production of the porous layer 2 consists of a step of applying a coating liquid to the resin substrate 1 and a step of drying and / or firing the coating liquid. Methods for applying the coating liquid to the resin substrate 1 include spin coating, blade coating, roll coating, slit coating, printing, gravure coating, and dip coating. When manufacturing components with three-dimensionally complex shapes such as concave surfaces, the spin coating method is preferred because it is easy to apply the coating to a uniform thickness. The drying and / or firing process of the coating solution is not particularly limited. [Examples]

[0055] A resin substrate with a micro-textured surface was fabricated by injection molding using a mold with an inverted micro-textured surface. The spacing P between the depressions was set to 250 nm. Cycloolefin resin was used as the resin material, and molding was performed at a molten resin temperature of 270°C, a mold temperature of 130°C, and a holding pressure of 50 MPa. After molten resin injection, the molded resin temperature was cooled to a temperature below the glass transition temperature, and then the molded product was released using an ejector pin to prevent tilting, thereby producing a resin substrate with a micro-textured surface. For each example of resin substrate, a coating solution was prepared and applied to form a porous layer. The evaluation method is described below.

[0056] <Evaluation of the size of micro-textures> Using a high-resolution SEM with FIB, we repeatedly performed FIB-based slicing and SEM-based observation, and then reconstructed the acquired images to evaluate the three-dimensional size of the micro-surface structure.

[0057] <Evaluation of the reflectivity of anti-reflective structures> The reflectance was measured using a reflectance meter (Olympus USPM-RUIII) at wavelengths from 380 nm to 780 nm.

[0058] <Evaluation of the refractive index of porous layers> The refractive index of the porous layer was determined from the analysis using the size and reflectance results of the micro-texture structure. The refractive index model of the anti-reflective structure used in the analysis is shown in Figure 8.

[0059] In Figure 8, the horizontal axis represents the layer thickness. Da is the thickness of the surface layer of the porous layer, and Ds is the thickness of the composite layer, using evaluation results from a high-resolution SEM with FIB. The vertical axis represents the refractive index. Nsr is the refractive index of the cycloolefin polymer (1.537). Na is the refractive index of the porous layer. Nsb is the composite refractive index at the bottom of the micro-textured structure (resin substrate side), and Nst is the composite refractive index on top of the micro-textured structure (surface side).

[0060] The composite refractive index was expressed using the Maxwell-Garnett equation, and the volume fraction of the solid in the equation was obtained from the evaluation results of a high-resolution SEM with FIB. Furthermore, the refractive index of the porous layer with a fine uneven structure, i.e., the filled portion, was assumed to be the same as the refractive index of the porous layer on the surface, and the refractive index of the porous layer was determined.

[0061] <Evaluation of scratch resistance> The scratch resistance of the anti-reflective structure was evaluated using the following method: A dry wiping test was performed 50 times back and forth using lens tissue, and peeling and scratches were visually checked. The load used during the test was 100g / cm². 2 From 100g / cm 2 The amount was gradually increased until peeling or damage to the film was observed. For example, 500 g / cm³ 2If film peeling or scratches are observed after 50 back-and-forth dry wiping tests under load, the scratch resistance evaluation result is 400g / cm². 2 I gave it an evaluation.

[0062] (Example 1) A resin substrate with a triangular lattice arrangement of cylindrical recesses as a fine uneven structure was prepared, and a coating liquid for forming a porous layer was prepared by the following method. A porous layer was then formed on the resin substrate to produce a component with an anti-reflective structure.

[0063] 400 g of an isopropyl alcohol dispersion of linear silicon dioxide particles (IPA-ST-UP, manufactured by Nissan Chemical Corporation, particle size 40 nm, solid content concentration 15% by mass) was heated and distilled while adding 1-propoxy-2-propanol. The isopropyl alcohol was distilled until the solid content concentration reached 30.0% by mass to prepare 200 g of a 1P2P solvent-substituted solution of linear silicon dioxide particles (hereinafter referred to as "solvent-substituted solution 1"). Dynamic light scattering measurements showed that the peak value of the particle size distribution of the linear silicon dioxide particles was 40 nm, the average particle size of the primary particles was 10 nm, and the major axis of the secondary particles was 40 nm to 100 nm.

[0064] In a separate container, 12.48 g of ethyl silicate was added to 13.82 g of ethanol and an aqueous nitric acid solution (3% concentration). The mixture was stirred at room temperature for 10 hours to prepare silica sol 1 (solid content concentration 11.5% by mass). Gas chromatography confirmed that the ethyl silicate starting material had reacted completely.

[0065] Solvent replacement solution 1 was diluted with ethyl lactate to a solid content concentration of 5.0% by mass, and then silica sol 1 was added so that the mass ratio of silicon dioxide particles to silica sol component was 100:5. Furthermore, the mixture was stirred at room temperature for 2 hours to obtain coating solution 1 containing chain-like silicon dioxide particles.

[0066] The obtained coating solution 1 was dropped onto a resin substrate, a film was formed using a spin coater, and then baked on a hot plate at 100°C for 5 minutes to produce a component with an anti-reflective structure.

[0067] Subsequently, a reflectance evaluation was conducted, and the average reflectance at wavelengths of 400 nm to 700 nm was found to be 0.12%. A scratch resistance evaluation was conducted, and the average reflectance was 400 g / cm³. 2 That was the case.

[0068] Subsequently, the size of the fine surface structure was evaluated using a high-resolution SEM with FIB. The thickness Da of the surface layer of the porous layer was 91 nm, and the depth Ds of the depressions was 60 nm. The cross-sectional shape including the central axis of the cylindrical depressions, as illustrated in Figure 4(a), had sides that widened slightly towards the top (opening), and the opening angle θs was a straight line tilted at 3°. The size of the depressions, with Ls being the diameter of the central part in the depth direction, was 151 nm. The refractive index of the porous layer, calculated from the refractive index model, was 1.20.

[0069] (Example 2) A resin substrate with a modified recess size was prepared, and a component having an anti-reflective structure was fabricated in the same manner as in Example 1, except that the mass ratio of silicon dioxide particles to silica sol component in coating solution 1 was set to 100:10.

[0070] When the obtained material was evaluated, the reflectance evaluation showed an average reflectance of 0.12% at wavelengths of 400 nm to 700 nm, and the scratch resistance evaluation showed 400 g / cm³. 2 That was the case.

[0071] Furthermore, using a high-resolution SEM with FIB, the size of the micro-rough structure was evaluated, and the surface thickness Da was found to be 90 nm, while the depth Ds of the depressions was 49 nm. The cross-sectional shape including the central axis of the cylindrical depressions was as shown in Figure 4(a), and the side surface was a straight line with an opening angle θs of 3°. The size of the depressions, when the diameter Ls is the central part in the depth direction, was 153 nm. The refractive index of the porous layer calculated from the refractive index model was 1.22.

[0072] (Example 3) A resin substrate with a modified recess size was prepared, and a component having an anti-reflective structure was fabricated in the same manner as in Example 1, except that the mass ratio of silicon dioxide particles to silica sol component in coating solution 1 was set to 100:15.

[0073] When the obtained material was evaluated, the reflectance evaluation showed an average reflectance of 0.18% at wavelengths of 400 nm to 700 nm, and the scratch resistance evaluation showed 400 g / cm³. 2 That was the case.

[0074] Furthermore, using a high-resolution SEM with FIB, the size of the micro-rough structure was evaluated, and the surface thickness Da was found to be 91 nm, while the depth Ds of the recesses was 26 nm. The cross-sectional shape including the central axis of the cylindrical recesses was as shown in Figure 4(a), and the sides were straight lines with an opening angle θs of 3°. The size of the recesses, when the diameter Ls is the central part in the depth direction, was 172 nm. The refractive index of the porous layer calculated from the refractive index model was 1.26.

[0075] (Example 4) A resin substrate was prepared under the same conditions as in Example 3, and a component having an anti-reflective structure was prepared in the same manner as in Example 1, except that the coating liquid 2 was prepared by the following method.

[0076] To solvent-exchanged solution 1, obtained in the same manner as in Example 1, an isopropyl alcohol dispersion of hollow silicon oxide particles was added so that the mass ratio of chain-like silicon oxide particles to hollow silicon oxide particles was 2:1 to obtain dispersion 2. As the isopropyl alcohol dispersion of hollow silicon oxide particles, JGC Catalysts & Chemicals Co., Ltd.'s Thru-Ria 4110 was used, with an average particle diameter (Ferret diameter) of approximately 60 nm, a shell thickness of approximately 10 nm, and a solid content concentration of 20.5% by mass. Silica sol 1 was also prepared in the same manner as in Example 1.

[0077] Dispersion 2 was diluted with ethyl lactate to a solid content concentration of 5.0% by mass, and then silica sol 1 was added so that the mass ratio of silicon dioxide particles to silica sol component was 100:10. Furthermore, by mixing and stirring at room temperature for 2 hours, coating solution 2 containing chain-like silicon dioxide particles and hollow silicon dioxide particles was obtained.

[0078] When the obtained member was evaluated, the reflectance evaluation showed that the average reflectance in the wavelength range of 400 nm to 700 nm was 0.15%, and the abrasion resistance evaluation was 500 g / cm 2 was obtained.

[0079] Also, using a high-resolution SEM device with FIB, when the size of the fine uneven structure was evaluated, the thickness Da of the surface layer was 105 nm, and the depth Ds of the concave portion was 26 nm. Also, the cross-sectional shape including the central axis of the columnar concave portion was in the form shown in Fig. 4(a), and the side surface was a straight line inclined at an opening angle θs of 3°. The size when the diameter at the center of the concave portion in the depth direction was Ls was 172 nm.

[0080] In this example, the ratio of the hollow particles present in the porous material was different between the filling portion and the surface layer in the concave portion. The hollow particles were preferentially arranged on the surface layer side, and the abrasion resistance was improved. It is considered that the arrangement of the hollow particles on the outermost surface improves the slipperiness, and the adhesion to the resin base material can be sufficiently ensured by mixing with the chain-like particles.

[0081] The evaluation for reference of the refractive index of the porous layer was performed by the following method. Coating liquid 2 was applied on a silicon wafer under the same conditions as those for forming on the resin base material in the example, and fired to form a porous layer. Using a spectroscopic ellipsometer (VASE, manufactured by J. A. Woolam Japan), light was made to enter the porous layer, and the reflected light was measured from a wavelength of 380 nm to 800 nm to calculate the refractive index, which was 1.21.

[0082] (Comparative Example 1) A member having an antireflection structure was produced in the same manner as in Example 2, except that a resin base material with a different size of the concave portion was produced.

[0083] When the obtained member was evaluated, the reflectance evaluation showed that the average reflectance in the wavelength range of 400 nm to 700 nm was 1.10%, and the abrasion resistance evaluation was 400 g / cm 2 was obtained.

[0084] Furthermore, using a high-resolution SEM with FIB, the size of the micro-rough structure was evaluated, and the surface thickness Da was found to be 90 nm, while the depth Ds of the recesses was 130 nm. The cross-sectional shape including the central axis of the cylindrical recesses was as shown in Figure 4(a), and the side surface was a straight line with an opening angle θs of 3°. The size of the recesses, when the diameter Ls is the central part in the depth direction, was 153 nm. The refractive index of the porous layer calculated from the refractive index model was 1.22.

[0085] The reason why the reflectivity of the component in this example is higher compared to Example 2 is thought to be because the depth of the recess was too deep, which reduced the reflection suppression effect due to interference.

[0086] (Comparative Example 2) A component having an anti-reflective structure was fabricated in the same manner as in Example 2, except that solvent replacement solution 1 was diluted with ethyl lactate so that the solid content concentration of the coating solution was 7.0% by mass.

[0087] When the obtained material was evaluated, the reflectance evaluation showed an average reflectance of 2.70% at wavelengths of 400nm to 700nm, and the scratch resistance evaluation showed 400g / cm³. 2 That was the case.

[0088] Furthermore, using a high-resolution SEM with FIB, the size of the micro-rough structure was evaluated, and the surface thickness Da was found to be 160 nm, while the depth Ds of the recesses was 49 nm. The cross-sectional shape including the central axis of the cylindrical recesses was as shown in Figure 4(a), and the sides were straight lines with an opening angle θs of 3°. The size of the recesses, when the diameter Ls is the central part in the depth direction, was 153 nm. The refractive index of the porous layer calculated from the refractive index model was 1.22.

[0089] The reason why the reflectivity of the component in this example is higher compared to Example 2 is thought to be because the thickness of the porous layer on the surface is too thick, which reduces the reflection suppression effect due to interference.

[0090] (Comparative Example 3) By changing the dry etching conditions when creating the micro-textured structure of the injection molding die, a micro-textured structure having conical protrusions was formed, and a resin substrate in which conical recesses were arranged in a triangular lattice was produced by injection molding using this mold. Except for using the resin substrate described above, a component having an anti-reflective structure was produced in the same manner as in Example 3.

[0091] When the obtained material was evaluated, the reflectance evaluation showed an average reflectance of 1.15% at wavelengths of 400nm to 700nm, and the scratch resistance evaluation showed 600g / cm³. 2 That was the case.

[0092] Furthermore, using a high-resolution SEM with FIB, the size of the micro-rough structure was evaluated, and it was found that the shape of the recesses was a frustoconical shape that widened towards the opening. The minimum diameter at the bottom of the recess (resin substrate side) was 5 nm, and the maximum diameter at the top of the recess (porous surface layer side) was 245 nm. The top of the recess and the surface of the filling area were almost identical, with no surface layer (Da=0), and the depth Ds of the recess was 350 nm. The refractive index of the porous layer calculated from the refractive index model of the depth was 1.26.

[0093] The anti-reflective structure in this example is a refractive index gradient structure. In such a structure, a moth-eye structure that does not fill the recesses is optimal. Filling the recesses with a porous material improves scratch resistance, but it results in a deterioration of anti-reflective performance.

[0094] (Comparative Example 4) A component having an anti-reflective structure was fabricated in the same manner as in Example 3, except that a mold without a fine uneven surface was used to create the resin substrate.

[0095] When the obtained material was evaluated, the reflectance evaluation showed an average reflectance of 0.50% at wavelengths of 400nm to 700nm, and the scratch resistance evaluation showed 100g / cm³. 2 That was the case.

[0096] The film thickness and refractive index of the porous layer were measured using a spectroscopic ellipsometer (VASE, manufactured by J.A. Woolam Japan) and calculated using a single-layer model. The film thickness was 90 nm and the refractive index was 1.26. The results for the examples and comparative examples are shown in Table 1.

[0097] [Table 1] [Explanation of symbols]

[0098] 1: Resin substrate, 1a: Convex portion, 1b: Recessed portion, 2: Porous layer, 20b: Surface layer, 30: Glass substrate, 31: Chain-like particles, 34: Hollow particles

Claims

1. A member comprising a resin substrate having a fine uneven surface structure, and a porous layer made of a porous material containing particles located on the resin substrate on the side with the fine uneven surface structure, The porous layer consists of a filling portion in which the porous material is filled into the voids of the fine uneven structure, and a surface layer on the fine uneven structure. The aforementioned fine uneven structure has columnar protrusions or columnar recesses arranged periodically in a two-dimensional manner. The thickness of the aforementioned surface layer is 80 nm or more and 150 nm or less. A member characterized in that the spacing between the protrusions or recesses is 20 nm or more and 300 nm or less, and the height of the protrusions or the depth of the recesses is 10 nm or more and 120 nm or less.

2. The member according to claim 1, characterized in that the refractive index of the porous layer is 1.15 or more and 1.30 or less.

3. The member according to claim 1 or 2, characterized in that the volume ratio of the filling portion in the fine uneven structure is 30% to 50%.

4. The member according to any one of claims 1 to 3, characterized in that the particles consist of silica.

5. The member according to claim 4, characterized in that the particles are chain-like particles.

6. The member according to claim 4, characterized in that the particles consist of chain-like particles and hollow particles.

7. The member according to any one of claims 1 to 6, further comprising a glass substrate, wherein the resin substrate is laminated on the glass substrate.

8. A display device characterized by comprising the member described in any one of Claims 1 to 7.

9. An imaging device characterized by comprising the member described in any one of Claims 1 to 7.

10. A head-mounted display characterized by comprising the member described in any one of Claims 1 to 7.

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