Laminated film, method for producing laminated film, optical member, and method for producing optical member

Abstract

Provided is a laminated film with which it is possible to realize an optical member in which defects in pattern shape can be suppressed and improved productivity is possible. The laminated film according to an embodiment of the present invention comprises a base material having a first main surface and a second main surface on the reverse side from the first main surface, and an uneven layer disposed on the first main surface. The uneven layer has projecting parts composed of a surface protective film, and a recessed part composed of a low-refractive-index part arranged between the projecting parts. The low-refractive-index part has a porous structure. The ratio of the total area of the recessed parts to the total area of the uneven layer viewed from the thickness direction of the laminated film is 50% or less.

Description

Laminated film, laminated film manufacturing method, optical member, and optical member manufacturing method

[0001] The present invention relates to a laminated film, a method for manufacturing a laminated film, an optical member, and a method for manufacturing an optical member.

[0002] It is known that disposing a low-refractive index layer having a porous structure on a substrate improves the light reflection efficiency and improves and maintains the intensity of light emitted from optical components such as lighting devices equipped with a light source and a light guide layer. Optical components capable of distributing light by partially disposing a low-refractive index layer on a substrate to change the light extraction position have also been produced. Using such an optical component, an optical component can be realized that can efficiently distribute light irradiated onto the light guide layer and extract desired light. For example, to partially dispose a low-refractive index layer, a technique has been proposed in which a material having a porous structure is applied to the entire surface of the substrate, and then an ink (paint) containing a curable resin is selectively applied to form a patterned low-refractive index layer on the substrate (e.g., Patent Document 1).

[0003] International Publication No. 2019 / 182100

[0004] However, when producing a low refractive index layer having a pattern shape such as the above-mentioned optical component, productivity may decrease due to loss of material caused by filling with ink, etc. Furthermore, defects may occur in the pattern shape of the low refractive index layer. An object of the present invention is to provide a laminate film that can suppress defects in the pattern shape of the low refractive index portion and realize an optical component that can improve productivity.

[0005] [1] A laminate film according to an embodiment of the present invention includes a substrate having a first main surface and a second main surface opposite the first main surface; and a concave-convex layer disposed on the first main surface. The concave-convex layer has convex portions formed of a surface protective film and concave portions formed of low refractive index portions disposed between the convex portions. The low refractive index portions have a porous structure. The ratio of the total area of ​​the concave portions to the total area of ​​the concave-convex layer as viewed in the thickness direction of the laminate film is 50% or less. [2] In the laminate film described in [1] above, the low refractive index portions may be disposed on the first main surface of the substrate. [3] In the laminate film described in [1] or [2] above, the low refractive index portions may be formed in an island shape in a plan view as viewed in the thickness direction. [4] In the laminate film described in [3] above, the diameter of an equivalent diameter of an isocircular ellipse of the low refractive index portions in the plan view may be 1 μm or more and 500 μm or less. [5] In the laminate film described in any one of [1] to [4] above, the surface protective film may include a film layer and a pressure-sensitive adhesive layer disposed on the substrate side of the film layer. The thickness of the low refractive index portion may be smaller than the thickness of the film layer. [6] In the laminate film described in [5] above, the thickness of the low refractive index portion may be smaller than the thickness of the pressure-sensitive adhesive layer. [7] According to another aspect of the present invention, there is provided a method for producing a laminate film described in any one of [1] to [6] above. The method for producing a laminate film includes: a through-hole forming step of forming a through-hole in the surface protective film; a disposing step of disposing the surface protective film having the through-hole formed therein on the substrate; and a low-refractive index portion forming step of applying a low-refractive index portion forming material to the portion of the substrate exposed by the through-hole to form a low-refractive index portion. [8] In the laminate film manufacturing method described in [7] above, the low-refractive index portion forming step may include applying the low-refractive index portion forming material by spraying. [9] An optical element according to another aspect of the present invention includes a substrate and a plurality of low refractive index portions disposed on a main surface of the substrate. The low refractive index portions have a porous structure. A ratio of the area of ​​the low refractive index portions to the total area of ​​the main surface of the substrate and the low refractive index portions as viewed in a thickness direction of the optical element is 50% or less.

[10] In the optical member described in [9] above, the low refractive index portion may be formed in an island shape in plan view when viewed from the thickness direction.

[11] In the optical member described in

[10] above, the low refractive index portion may have an equivalent diameter of an isocircumferential ellipse in plan view of 1 μm or more and 500 μm or less.

[12] According to another aspect of the present invention, there is provided a method for manufacturing an optical member described in any one of [9] to

[11] above. The method for manufacturing the optical member includes: a through-hole forming step of forming a through-hole in a surface protective film that protects the substrate; an arrangement step of arranging the surface protective film having the through-hole formed therein on the substrate; a low refractive index portion forming step of applying a low refractive index portion forming material to the exposed portion of the substrate due to the through-hole to form a low refractive index portion; and a peeling step of peeling off the surface protective film after the low refractive index portion forming step.

[13] In the method for manufacturing an optical member described in

[12] above, the low refractive index portion forming step may include applying the low refractive index portion forming material by spraying.

[0006] According to the embodiments of the present invention, a laminated film capable of realizing an optical member capable of suppressing defects in pattern shape and enabling improvement in productivity, and an optical member in which defects in pattern shape are suppressed, can be obtained.

[0007] FIG. 1 is a schematic cross-sectional view of a laminate film according to one embodiment of the present invention; FIG. 2 is a schematic plan view of a laminate film according to the embodiment of the present invention, viewed from the thickness direction; FIG. 3 is a schematic cross-sectional view of an optical member according to one embodiment of the present invention; FIG. 4 is a schematic plan view of an optical member according to the embodiment of the present invention, viewed from the thickness direction; FIG. 5 is a schematic partial perspective view showing an example of a portion in one step (arrangement step) of a method for manufacturing a laminate film according to the embodiment of the present invention; FIG. 6 is a schematic partial cross-sectional view showing an example of a portion in one step (arrangement step) of a method for manufacturing a laminate film according to the embodiment of the present invention; FIG. 7 is a schematic partial cross-sectional view of a laminate film according to an example of the present invention, viewed from the thickness direction, and is an explanatory diagram illustrating the concepts of dot diameter and pitch in a laminate film; FIG. 8 is a diagram showing the surface state in plan view of a laminate film in Example 1, observed with a laser microscope and image-processed; FIG. 9 is a diagram showing the surface state in plan view of a laminate film in Example 2, observed with a laser microscope and image-processed; and FIG. 10 is a diagram showing the surface state in plan view of a laminate film in Example 3, observed with a laser microscope and image-processed. FIG. 10 is a diagram showing the surface state in a plan view of a laminated film in Example 4, which was observed with a laser microscope and image-processed.

[0008] Representative embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. For ease of viewing and understanding, the drawings are drawn schematically or conceptually, and the length, width, shape, size, ratio, direction, number, etc. may differ from the actual ones, and may not correspond to each other between the drawings. In this specification, "A and / or B" means either "A," "B," or "A and B."

[0009] A. Overall Configuration First, the overall configuration of the laminate film and the optical member will be described.

[0010] A-1. Overall Structure of the Laminated Film FIG. 1A is a schematic cross-sectional view of a laminated film according to one embodiment of the present invention. The illustrated laminated film 100 comprises a substrate 10 having a first major surface 10a and a second major surface 10b opposite the first major surface 10a; and an uneven layer 2 disposed on the first major surface 10a. The uneven layer 2 has convex portions 2a formed by a surface protective film 30 and concave portions 2b formed by low refractive index portions 20 disposed between the convex portions 2a. The low refractive index portions 20 have a porous structure. In an embodiment of the present invention, the ratio of the total area of ​​the concave portions 2b to the total area of ​​the uneven layer 2 as viewed from the thickness direction of the laminated film 100 (as viewed from above in the illustrated example) is 50% or less.

[0011] Conventionally, when fabricating an optical element having a patterned low-refractive index layer, it is necessary to first form a coating film having a porous structure and then penetrate ink into portions of the porous structure to form the desired pattern. The portions of the porous structure that are not permeated with ink become the low-refractive index layer (portion), while the portions that are permeated with ink are formed as portions that do not function as low-refractive index portions. Therefore, the material of the portions that are permeated with ink (portions that do not function as low-refractive index portions) may be essentially wasted as material for forming the low-refractive index portions. Furthermore, attempts to miniaturize the pattern shape of the low-refractive index portion (reducing the area of ​​the low-refractive index portion) increase the amount of ink used for permeation and also reduce the spacing between inks, which can lead to interference between adjacent patterns and result in defective pattern shapes.

[0012] In contrast, the surface protective film in the laminate film according to an embodiment of the present invention has through holes formed therein, which may correspond to recesses in the uneven layer. Furthermore, when the surface protective film is placed on the main surface of the substrate, exposed portions of the substrate are formed at positions corresponding to the through holes on the main surface of the substrate (hereinafter, sometimes referred to as "exposed portions"). During the manufacturing process of the laminate film, low refractive index portions are formed in the through holes (exposed portions). Since the low refractive index portions are typically significantly thinner than the surface protective film, the low refractive index portions constitute the recesses in the uneven layer. Thus, in the laminate film according to an embodiment of the present invention, the surface protective film functions as a mask for selectively forming low refractive index portions. In other words, to form patterned low refractive index portions, it is sufficient to form through holes in the surface protective film in a desired pattern and then coat the through holes with a material for forming the low refractive index portions. As a result, when the laminate film according to an embodiment of the present invention is used to manufacture optical components, not only is the need for ink to be permeated to selectively form low refractive index portions, as in the prior art, unnecessary, but the amount of material used to form the low refractive index portions can also be reduced. Furthermore, the convex portions can be made not to function as low-refractive-index portions, and there is no need to fill the surface protection film with ink or the like (to prevent them from functioning as low-refractive-index portions). Furthermore, in the laminate film according to the embodiment of the present invention, as described above, patterning of the low-refractive-index portions does not involve ink penetration and is not affected by ink interference, etc., so defects in the pattern shape of the low-refractive-index portions can be suppressed. Therefore, by using the laminate film according to the embodiment of the present invention, defects in the pattern shape of the low-refractive-index portions can be suppressed, and optical components can be realized at low cost and with improved productivity.

[0013] In this specification, the laminate film as viewed in the thickness direction of the laminate film is sometimes simply referred to as a "plan view," and a view of the plan view is sometimes referred to as a "plan view." For example, Figure 1B is a partial plan view of a laminate film 100 according to one embodiment of the present invention. In Figure 1B, the area of ​​the concave-convex layer 2 in the plan view is the entire area of ​​the laminate film 100.

[0014] In the illustrated example (e.g., Figure 1A), the uneven layer 2 is formed on one side (first main surface 10a) of the main surfaces of the substrate 10, but the uneven layer may also be formed on the second main surface 10b side, or the uneven layer may be formed on both the first main surface and the second main surface.

[0015] The ratio of the total area of ​​the recesses 2b to the total area of ​​the uneven layer 2 as viewed in the thickness direction of the laminated film 100 is preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less. The lower limit of the ratio of the total area of ​​the recesses 2b to the total area of ​​the uneven layer 2 is, for example, more than 0%, and is preferably 1% or more, more preferably 3% or more, and even more preferably 5% or more.

[0016] In the illustrated example, the low refractive index portions 20 are arranged between the convex portions 2a of the uneven layer 2, and form the concave portions 2b. The low refractive index portions 20 are preferably arranged on the first main surface 10a of the substrate 10. "Arranged on the first main surface of the substrate" means that the low refractive index portions 20 are arranged in contact with the first main surface of the substrate.

[0017] The low refractive index portions are preferably formed in an island shape in plan view when viewed from the thickness direction of the laminate film. Forming the low refractive index portions in an island shape can contribute to further improving the light extraction efficiency of an optical component that can be fabricated from a laminate film according to an embodiment of the present invention. "Island-shaped" means that, in plan view, multiple low refractive index portions are not continuous but are spaced apart. In a laminate film according to one embodiment of the present invention, multiple low refractive index portions are formed in an island shape by forming through holes patterned in an island shape in the surface protective film.

[0018] In one embodiment of the laminate film of the present invention, the equivalent diameter of an isocircumferential ellipse of the low refractive index portion in plan view is preferably 1 μm or more and 500 μm or less. Having the equivalent diameter of an isocircumferential ellipse of the low refractive index portion in plan view within the above range has the advantage of enabling the production of a laminate film capable of realizing an optical component having a more precise pattern shape. The "equivalent diameter of an isocircumferential ellipse of the low refractive index portion in plan view" refers to the diameter of a circle, assuming that the shape of the recess constituting the low refractive index portion on the surface (plane) in plan view is a circle. The equivalent diameter of an isocircumferential ellipse of the low refractive index portion in plan view is more preferably 2 μm or more, even more preferably 5 μm or more, and particularly preferably 10 μm or more. On the other hand, the equivalent diameter of an isocircumferential ellipse of the low refractive index portion in plan view is more preferably 300 μm or less, even more preferably 250 μm or less. The equivalent diameter of an isocircumferential ellipse refers to the major axis of the ellipse when the recess is elliptical in plan view, or refers to the diameter of the inscribed circle when the recess is polygonal.

[0019] A-2. Overall Configuration of Optical Element An optical element according to an embodiment of the present invention comprises a substrate and a plurality of low refractive index portions disposed on a major surface of the substrate. Optical element 101 shown in FIG. 2A comprises a substrate 10 and a plurality of low refractive index portions 20 disposed on a major surface (first major surface 10a in FIG. 2A) of the substrate 10. The low refractive index portions have a porous structure. The ratio of the area of ​​the low refractive index portions to the total area of ​​the major surface of the substrate and the low refractive index portions as viewed in the thickness direction of the optical element is 50% or less.

[0020] Optical elements according to embodiments of the present invention may typically have a light distribution function. The light distribution function refers to, for example, a function in which a laminate film is disposed on a light guide layer, and a portion of the light from the light source is totally reflected by a low refractive index portion, partially blocking the light from exiting one side of the light guide layer, thereby allowing a portion of the light to exit the light guide layer from a location where the low refractive index portion is not provided, thereby adjusting the light intensity and thereby varying the degree of light extraction depending on the position of the light guide layer from the light source. Achieving light distribution can contribute to uniforming the brightness of light emitted from the light guide layer. As described above, optical elements according to embodiments of the present invention facilitate patterning of the low refractive index portion in the laminate film, and can be effectively miniaturized. Therefore, optical elements according to embodiments of the present invention can suppress defects in the pattern shape. Furthermore, optical elements according to embodiments of the present invention can effectively miniaturize the low refractive index portion, thereby achieving highly efficient light distribution.

[0021] The optical member according to the embodiment of the present invention has a configuration in which the surface protective film is peeled off from the laminate film. That is, the optical member according to the embodiment of the present invention can be produced by peeling off the surface protective film, which serves as a mask for forming the low refractive index portion, from the laminate film. The substrate and the low refractive index portion in the optical member according to the embodiment of the present invention may correspond to the substrate and the low refractive index portion in the laminate film, respectively. In the optical member according to the embodiment of the present invention, the description of the laminate film described below will be used to cite the configuration common to the laminate film, and will be omitted as appropriate.

[0022] Next, the configuration that the laminate film or optical member according to the embodiment of the present invention may have will be specifically described.

[0023] B. Substrate The substrate (and consequently the laminate film and optical component) may have any suitable shape. The substrate may be, for example, long or sheet-like. In the illustrated example (e.g., FIG. 3A ), the substrate 10 is long and can be wound into a roll. In this specification, the term "long" refers to an elongated shape in which the length is sufficiently longer than the width, and includes, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, the width.

[0024] The substrate may be, for example, a resin film. Any appropriate resin material may be used as the material constituting the resin film. Specific examples of the resin material constituting the resin film, such as the main component, include transparent resins such as cycloolefin (COP)-based resins (e.g., polynorbornene-based), polyester-based resins (e.g., polyethylene terephthalate (PET)-based), polycarbonate (PC)-based resins, (meth)acrylic resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, polyolefin-based resins, and acetate-based resins. Examples of thermosetting resins or ultraviolet-curing resins include (meth)acrylic resins, urethane-based resins, (meth)acrylic urethane-based resins, epoxy-based resins, and silicone-based resins. The term "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins. Other examples include glassy polymers such as siloxane-based polymers. The resin film may be, for example, an extrusion molded product of the above-mentioned resin material or resin composition. The resin film materials may be used alone or in combination. The resin material constituting the resin film may further contain additives, such as antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, and antistatic agents.

[0025] The substrate may have any appropriate thickness. The thickness of the substrate is, for example, 6 μm or more and 1 mm or less. The thickness of the substrate is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The thickness of the substrate may typically be 100 μm or less.

[0026] C. Uneven Layer The uneven layer is disposed on the first main surface of the substrate. The uneven layer has convex portions and concave portions between the convex portions. The convex portions are formed by a surface protective film. The concave portions are formed by low refractive index portions disposed between the convex portions. That is, the thickness of the surface protective film is greater than the thickness of the low refractive index portions.

[0027] The pattern shape of the uneven layer (substantially, the low refractive index portion) can be any appropriate pattern depending on the purpose. The pattern shape of the uneven layer can be controlled, for example, based on the shape, number, and position of the through holes in the surface protection film that serves as a mask. Specific examples of the pattern shape of the uneven layer include circular, elliptical, rectangular, and polygonal shapes as the shape of the recesses (low refractive index portions) in a planar view. Specific examples of the pattern shape of the uneven layer include an arrangement in which the recesses in a planar view are spaced approximately equally apart in the length direction and width direction between adjacent recesses.

[0028] The longitudinal and widthwise spacings between adjacent recesses in the plane of the laminate film according to an embodiment of the present invention are preferably independently 2 μm or more and 5000 μm or less. When the longitudinal spacing and widthwise spacing are within the above ranges, the pattern shape of the low refractive index portion in the laminate film according to an embodiment of the present invention can be made finer. The longitudinal spacing and widthwise spacing refer to the distance between the centers (area centers of gravity) of adjacent recesses. In one embodiment of the laminate film 100, the pattern shape of the uneven layer 2 is such that, in a plan view, the recesses 2 b (low refractive index portions 20) have a circular shape, and the recesses 2 b (low refractive index portions 20) are arranged so that the longitudinal and widthwise spacings between adjacent recesses 2 b are equal.

[0029] In a laminated film according to one embodiment, the recesses (specifically, the low refractive index portions constituting the recesses) are more preferably arranged in a lattice pattern with approximately equal intervals in plan view. In other words, the low refractive index portions are arranged at approximately equal intervals in the length direction and width direction on the first main surface of the substrate. In this case, the respective lengthwise intervals and widthwise intervals are approximately equal to each other. "Approximately equal intervals" is not limited to strictly the same intervals, and an interval within a range of ±5 μm is acceptable as approximately equal intervals. The same applies to "approximately equal."

[0030] C-1. Surface Protection Film The surface protection film in the laminate film according to an embodiment of the present invention is temporarily and removably attached to the substrate. That is, as described above, the surface protection film functions as a mask for selectively forming a low refractive index portion and can protect the surface (main surface) of the substrate until the optical component is put into use. The surface protection film 30 in the illustrated example (e.g., FIG. 1A) includes a film layer 31 and a pressure-sensitive adhesive layer 32. The pressure-sensitive adhesive layer 32 can be disposed on the substrate 10 side of the film layer 31. The surface protection film 30 is temporarily and removably attached to the substrate 10 via the pressure-sensitive adhesive layer 32. In the laminate film according to an embodiment of the present invention, as described above, the surface protection film (substantially the film layer 31 and the pressure-sensitive adhesive layer 32) constitutes the convex portions 2a of the uneven layer 2. In the illustrated example, the longitudinal direction of the elongated surface protection film 30 and the longitudinal direction of the substrate 10 are substantially parallel. In one embodiment, the width dimension of the elongated surface protection film 30 can be designed to be substantially the same as or larger than the width dimension of the substrate 10. The surface protection film can be provided on one or both of the main surfaces (first main surface and second main surface) of the substrate.

[0031] The film layer of the surface protection film may be made of any suitable resin film. Examples of materials for forming the resin film include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Ester resins (particularly polyethylene terephthalate resins) are preferred.

[0032] The thickness of the film layer is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The upper limit of the thickness of the film layer may be, for example, 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less. Such a thickness has the advantage that deformation is unlikely to occur even when tension is applied during transportation and / or lamination.

[0033] The adhesive layer, as its name suggests, is composed of an adhesive. Examples of adhesives include adhesive compositions that use an acrylic resin, a styrene resin, a silicone resin, or the like as a base resin, and that are blended with a crosslinking agent selected from an isocyanate compound, an epoxy compound, an aziridine compound, or the like, and a silane coupling agent. Acrylic adhesives are preferably used from the standpoints of chemical resistance, adhesion (for example, to prevent penetration of a solution during immersion, as described below), and flexibility to adherends.

[0034] The thickness of the pressure-sensitive adhesive layer in the laminate film according to one embodiment of the present invention is smaller than the thickness of the film layer. The thickness of the pressure-sensitive adhesive layer is, for example, 1 μm or more and 60 μm or less. The thickness of the pressure-sensitive adhesive layer is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. On the other hand, the thickness of the pressure-sensitive adhesive layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. Within the above range, the adhesiveness of the pressure-sensitive adhesive layer can be maintained to a level that allows temporary adhesion, and the inclusion of air bubbles between the substrate and the film layer can be suppressed. Furthermore, within the above range, problems such as pressure-sensitive adhesive overflow can be suppressed.

[0035] C-2. Low refractive index portion As described above, the low refractive index portion is disposed between the convex portions of the concave-convex layer. In the laminate film and optical member according to the embodiment of the present invention, a plurality of low refractive index portions may be disposed.

[0036] The refractive index of the low refractive index portion is lower than that of the substrate, for example. The refractive index of the low refractive index portion is, for example, 1.30 or less, with the lower limit exceeding 1.00. The refractive index of the low refractive index portion is preferably 1.13 to 1.28, more preferably 1.14 to 1.27, even more preferably 1.15 to 1.26, and particularly preferably 1.16 to 1.25. If the refractive index of the low refractive index portion is within this range, the first main surface side of the substrate (more specifically, the exposed portion of the substrate through the through holes) can have a low refractive index portion having a pattern shape, and the light distribution function can be particularly well exhibited. Note that, unless otherwise specified, the refractive index refers to the refractive index measured at a wavelength of 550 nm. The refractive index is, for example, a value measured by the method described in the Examples below.

[0037] The total light transmittance of the low refractive index portion is preferably 85% to 99%, more preferably 87% to 98%, and even more preferably 89% to 97%. By providing such a low refractive index portion on the first main surface side of the substrate (more specifically, on the exposed portion of the substrate through the through holes), for example, excellent transparency can be achieved for the entire laminate film. As a result, for example, when the laminate film is applied to various products, visibility can be ensured. The total light transmittance can be measured, for example, using a haze meter (e.g., "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0038] The haze of the low refractive index portion is preferably less than 5%, more preferably less than 3%. On the other hand, the haze may be, for example, 0.1% or more, or 0.2% or more. By providing such a low refractive index portion on the first main surface side of the substrate (more specifically, the exposed portion of the substrate through the through holes), for example, excellent transparency can be achieved for the entire laminate film. The haze can be calculated, for example, using the value measured with the same haze meter as above, using the following formula: Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] × 100 (%)

[0039] The thickness of the low refractive index portion is, for example, 0.1 μm or more, preferably 0.3 μm or more, more preferably 1.0 μm or more, even more preferably 1.2 μm or more, particularly preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. The thickness of the low refractive index portion may be, for example, 2.2 μm or more, or, for example, 2.5 μm or more, or, for example, 2.8 μm or more. On the other hand, the thickness of the low refractive index portion may be, for example, 10 μm or less, or, for example, 8 μm or less, or, for example, 6 μm or less, or, for example, 4 μm or less. When the thickness of the low refractive index portion is within this range, the pattern shape of the low refractive index portion can be made more precise. Furthermore, when the thickness of the low refractive index portion is within this range, the productivity of producing an optical element from the laminate film according to an embodiment of the present invention can be further improved. Furthermore, when the thickness of the low refractive index portion is within this range, the optical element according to an embodiment of the present invention can particularly effectively exhibit light distribution and light intensity adjustment functions.

[0040] The thickness of the low refractive index portion of the laminate film according to an embodiment of the present invention is smaller than the thickness of the surface protective film. Furthermore, the thickness of the low refractive index portion is preferably smaller than the thickness of the film layer of the surface protective film. Furthermore, the thickness of the low refractive index portion is preferably smaller than the thickness of the pressure-sensitive adhesive layer of the surface protective film. When the thickness of the low refractive index portion satisfies the above, the pattern shape of the low refractive index portion can be made more precise, which can further improve the productivity when producing an optical element from the laminate film. Furthermore, when the thickness of the low refractive index portion is within this range, the optical element according to an embodiment of the present invention can particularly effectively exhibit the light distribution function and the light intensity adjustment function.

[0041] In the laminate film according to the embodiment of the present invention, the ratio of the thickness of the film layer to the thickness of the low refractive index layer is preferably within the range of 1:1 to 2000:1. Within this range, the effects of the laminate film and the optical component can be more significantly achieved even when the thickness of the low refractive index portion in the laminate film and the optical component is made sufficiently smaller than the thickness of the film layer. The ratio of the thickness of the film layer to the thickness of the low refractive index layer in the laminate film is more preferably within the range of 1:1 to 1000:1, even more preferably 1:1 to 500:1, even more preferably 1:1 to 100:1, and particularly preferably 1:1 to 30:1.

[0042] In the laminate film according to an embodiment of the present invention, the ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the low refractive index layer is preferably within the range of 0.1:1 to 600:1. Within this range, the effects of the laminate film and the optical component can be more significantly achieved even when the thickness of the low refractive index portion in the laminate film and the optical component is made sufficiently smaller than the thickness of the pressure-sensitive adhesive layer. The ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the low refractive index layer in the laminate film is more preferably within the range of 0.1:1 to 300:1, even more preferably 0.1:1 to 100:1, even more preferably 0.1:1 to 50:1, and particularly preferably 0.1:1 to 10:1.

[0043] The low refractive index portion has a porous structure. Any appropriate configuration can be adopted for the low refractive index portion as long as it can achieve the desired characteristics. As a material for forming the low refractive index portion (hereinafter, sometimes referred to as a "material for forming the low refractive index portion"), for example, materials described in International Publication No. 2004 / 113966, Japanese Patent Application Laid-Open No. 2013-254183, and Japanese Patent Application Laid-Open No. 2012-189802 can be adopted.

[0044] Representative examples of materials for forming low refractive index portions include silicon compounds. Examples of silicon compounds include silica-based compounds; hydrolyzable silanes and their partial hydrolysates and dehydration condensates; silicon compounds containing silanol groups; and activated silica obtained by contacting silicate with acid or ion exchange resin. Examples of materials for forming low refractive index portions include organic polymers; polymerizable monomers (e.g., (meth)acrylic monomers and styrene-based monomers); and curable resins (e.g., (meth)acrylic resins, fluorine-containing resins, and urethane resins). These materials may be used alone or in combination of two or more.

[0045] In one embodiment, the low refractive index portion may contain spaces such as pores and gaps therein. In this case, the porosity of the low refractive index portion is preferably 20 vol% to 60 vol%, more preferably 25 vol% to 55 vol%, even more preferably 30 vol% to 50 vol%, and particularly preferably 35 vol% to 45 vol%. Such a porosity allows the refractive index of the low refractive index portion to be within an appropriate range and ensures strength. Here, the porosity is a value calculated using the Lorentz-Lorenz formula from the refractive index value measured with an ellipsometer.

[0046] The size of the pores that can be contained in the low refractive index portion can be adjusted to a desired size depending on the purpose and application. The size of the pores that can be contained in the low refractive index portion is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, the size of the pores that can be contained in the low refractive index portion is, for example, 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. Note that the size of the pores refers to the diameter of the major axis of the pores, out of the diameter of the major axis and the diameter of the minor axis.

[0047] The pore size can be quantified by the BET test method. In one embodiment, 0.1 g of a measurement sample (e.g., a fabricated low refractive index portion) is placed in the capillary of a specific surface area measurement device (e.g., "ASAP2020" manufactured by Micromeritics), and then the sample is dried under reduced pressure at room temperature for 24 hours to remove gases contained in the measurement sample. Then, nitrogen gas is adsorbed onto the measurement sample, and an adsorption isotherm is drawn to determine the pore distribution. This allows the pore size to be evaluated.

[0048] Examples of the low refractive index portion having an internal space include a porous layer made of a porous body and / or a layer at least partially including an air layer. That is, the low refractive index portion having an internal space includes at least one of the porous layer and the air layer.

[0049] The low refractive index portion typically includes aerogel and / or particles (for example, hollow fine particles and / or porous particles). The low refractive index portion is preferably a nanoporous layer (specifically, 90% or more of the pores have a diameter of 1×10 －１ nm to 1×10 ３ The thickness may be in the range of 100 nm.

[0050] Any appropriate particles may be used as the particles. The particles are typically composed of a silica-based compound. Examples of particle shapes include spherical, plate-like, needle-like, string-like, and bunch-of-grapes shapes. Examples of string-like particles include particles in which a plurality of spherical, plate-like, or needle-like particles are strung together like beads, short fiber-like particles (e.g., short fiber-like particles described in JP 2001-188104 A), and combinations thereof. The string-like particles may be linear or branched. Examples of bunch-of-grapes-shaped particles include particles in which a plurality of spherical, plate-like, and needle-like particles are aggregated to form a bunch-of-grapes shape. The particle shape can be confirmed, for example, by observation with a transmission electron microscope.

[0051] An example of the low refractive index portion is a structure composed of one or more types of structural units that form a fine void structure, and these structural units are bonded to each other (for example, chemically bonded via catalytic action). Examples of the shape of the structural units include particulate, fibrous, rod-like, and flat-plate-like. The structural units may have only one shape, or may have a combination of two or more shapes.

[0052] A specific example of the low refractive index portion is a porous layer composed of a porous body in which particles having micropores (hereinafter referred to as micropore particles) are chemically bonded to each other. Such a porous layer can be obtained, for example, by chemically bonding the micropore particles to each other. The shape of the micropore particles is not particularly limited and may be, for example, spherical or other shapes. Furthermore, the micropore particles may be, for example, sol-gel beaded particles, nanoparticles (e.g., hollow nanosilica / nanoballoon particles), nanofibers, etc. Representative micropore particles include inorganic substances. Specific examples of inorganic substances include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used alone or in combination of two or more. In one embodiment, the micropore particles are, for example, micropore particles of a silicon compound, and the porous body is, for example, a silicone porous body. The micropore particles of the silicon compound include, for example, a pulverized gel silica compound.

[0053] Another example of the low refractive index portion is a layer containing a fibrous material such as nanofibers, in which spaces are formed by the entanglement of the fibrous material. Further examples of the low refractive index portion include a layer formed using hollow nanoparticles or nanoclay, and a layer formed using hollow nanoballoons or magnesium fluoride. The low refractive index portion may be composed of a single constituent material, or may be composed of multiple constituent materials. The low refractive index portion may be composed of a single form of the above examples, or may be composed of multiple forms of the above examples.

[0054] The porous layer may have, for example, an open-cell structure in which the pores are interconnected. An open-cell structure refers to a porous body (e.g., a silicone porous body) in which the pores are interconnected three-dimensionally, and can also be described as a state in which the spaces in the pore structure are interconnected. The open-cell structure of the porous layer can increase the porosity. It is difficult to form an open-cell structure using closed-cell particles with individual pore structures, such as hollow particles (e.g., hollow silica). However, when using silica sol particles (a pulverized product of a gel-like silicon compound that forms a sol), the silica sol particles can have a three-dimensional dendritic structure, and the dendritic particles can settle and deposit in a coating film (a coating film of a sol containing a pulverized product of a gel-like silicon compound) to easily form an open-cell structure. The porous layer preferably has a monolithic structure in which the open-cell structure includes a plurality of pore distributions. The monolithic structure refers to, for example, a hierarchical structure including a structure in which nano-sized fine pores exist and an open-cell structure in which nano-sized fine pores are aggregated. The monolithic structure, for example, can provide membrane strength through fine pores while providing high porosity through a coarse open-cell structure, thereby achieving both membrane strength and high porosity.

[0055] For example, the monolith structure can be formed by controlling the pore distribution of the void structure generated in the gel (gel silicon compound) before pulverizing into silica sol particles.Also, for example, when pulverizing the gel silicon compound, the monolith structure can be formed by controlling the particle size distribution of the pulverized silica sol particles to a predetermined size.In addition, the particle size distribution can be measured by, for example, a particle size distribution evaluation device such as dynamic light scattering method or laser diffraction method, and an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0056] As described above, the porous layer may contain pulverized gel compounds such as gel silicon compounds, and the pulverized particles are chemically bonded (chemically bonded) to one another. The chemical bond is not particularly limited, and examples thereof include cross-linking, covalent bonding, and hydrogen bonding. The volume average particle size of the pulverized particles in the porous layer is, for example, 0.10 μm or more, preferably 0.20 μm or more, and more preferably 0.40 μm or more. Meanwhile, the volume average particle size of the pulverized particles in the porous layer is, for example, 2.00 μm or less, preferably 1.50 μm or less, and more preferably 1.00 μm or less. The volume average particle size is an index of the particle size variation of the pulverized particles and is determined by particle size distribution measurement.

[0057] The low refractive index portion may contain silicon atoms. For example, the silicon atoms contained in the low refractive index portion are preferably siloxane-bonded. Of all silicon atoms contained in the low refractive index portion, the proportion of unbonded silicon atoms (specifically, residual silanols) is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0058] In one embodiment, the material for forming the low refractive index portion may be a coating liquid in which the above-mentioned material is dispersed in a dispersion medium. The dispersion medium can adjust the viscosity and other properties of the coating liquid to a suitable range. As a result, the coating properties when forming the low refractive index portion can be improved. The dispersion medium may be a single solvent or a mixed solvent containing multiple solvents.

[0059] Examples of dispersion media include alcohols such as ethanol, isopropyl alcohol, butanol, t-butanol, isobutyl alcohol, and 2-methoxyethanol (methyl cellosolve); esters such as ethyl acetate and butyl acetate; ethers such as diisopropyl ether and propylene glycol monomethyl ether; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and aromatic hydrocarbons such as toluene. These dispersion media can be used alone or in combination. Among these dispersion media, alcohols are more preferred, and isobutyl alcohol is even more preferred. The mass ratio of the dispersion medium to the total amount of the low refractive index portion forming material is, for example, 5% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more, and is, for example, 100% by mass or less, preferably 95% by mass or less, and more preferably 60% by mass or less. When the content of the dispersion medium is within the above range, the viscosity of the low refractive index portion forming material can be stably adjusted to a range suitable for spray coating.

[0060] In one embodiment, the coating film (a coating film of a sol containing a pulverized product of a gel-like silicon compound) can be formed using a coating liquid containing microporous particles, and the microporous particles can be chemically bonded to each other by heating (including drying) this coating liquid. The coating liquid containing microporous particles is, for example, a suspension. For example, a catalyst (crosslinking reaction accelerator) that promotes crosslinking between the microporous particles (for example, a dehydration condensation reaction of residual silanol groups that may be contained in the microporous particles) and / or a substance that generates a catalyst (crosslinking reaction accelerator) (catalyst generator) may be added to the coating liquid. Examples of catalysts include photoactive catalysts and thermally active catalysts. Examples of catalyst-generating substances (catalyst generators) include photocatalyst generators and thermal catalyst generators. Examples of photocatalyst generators include photobase generators (catalysts that generate a basic catalyst upon light irradiation) and photoacid generators (substances that generate an acidic catalyst upon light irradiation). For example, the microporous particles may be a pulverized product of a gel-like compound (preferably a gel-like silicon compound), and the low refractive index portion may have a porous structure composed of a porous body (preferably a silicone porous body) containing the pulverized product of the gel-like compound. Such microporous particles may have a state in which the three-dimensional structure of the gel-like compound before pulverization is dispersed in the three-dimensional basic structure, and by using such microporous particles, a structure based on the three-dimensional basic structure may be formed. Specifically, a new structure different from the three-dimensional structure of the gel-like compound may be formed. In this way, the finally obtained low refractive index portion (porous structure) may have a refractive index as low as, for example, an air layer. Furthermore, by chemically bonding the microporous particles to each other, the three-dimensional basic structure can be fixed, and sufficient strength can be ensured in the finally obtained low refractive index portion (porous structure). Details of the specific configuration and formation method of the low refractive index portion (porous structure) are described, for example, in International Publication No. 2019 / 151073. The description of this publication is incorporated herein by reference.

[0061] The coating thickness of the coating liquid can be set according to the thickness desired for the low refractive index portion. The heating temperature of the coating film (coating liquid) is, for example, 20°C or higher, preferably 50°C or higher. On the other hand, the heating temperature of the coating film (coating liquid) is, for example, 200°C or lower, preferably 150°C or lower. The heating time of the coating film (coating liquid) is, for example, 10 seconds or longer. On the other hand, the heating time of the coating film (coating liquid) is, for example, 24 hours or shorter, preferably 1 hour or shorter, more preferably 30 minutes or shorter, and even more preferably 10 minutes or shorter.

[0062] A coating film that forms a void structure, which is a precursor of a porous layer (void layer), is formed on a substrate. The following describes the case where the particles are pulverized gel compounds. However, a coating film can be formed in the same way when the particles are other than pulverized gel compounds. The reason why a void structure suitable for the coating film is formed when the particles are pulverized gel compounds is presumed to be, for example, as follows. However, this presumption does not limit the method for forming the low refractive index portion.

[0063] Since the above-mentioned particles (porous particles) are obtained by pulverizing gel silicon compound, the three-dimensional structure of the gel silicon compound before pulverization is dispersed in three-dimensional basic structure.For example, by spraying the crushed material of gel silicon compound onto a substrate, the precursor of porous structure based on three-dimensional basic structure is formed.In other words, according to the above-mentioned method, a new porous structure (three-dimensional basic structure) is formed by spraying the crushed material, which is different from the three-dimensional structure of gel silicon compound.Therefore, in the low refractive index part that is finally obtained, for example, it can realize a low refractive index that functions as the same as air layer.

[0064] D. Manufacturing Method of Laminated Film The laminated film according to an embodiment of the present invention can be produced, for example, by placing a surface protection film having through holes on the first main surface of the substrate and applying a low refractive index portion-forming material to the exposed portion of the substrate exposed by the through holes to form a low refractive index portion. More specifically, the laminated film according to an embodiment of the present invention can be produced, for example, as follows.

[0065] First, a surface protection film is prepared. In the laminate film manufacturing method according to an embodiment of the present invention, the surface protection film can be used as a mask for forming a pattern of low refractive index portions. Therefore, the surface protection film preferably has through holes formed in a desired pattern. Low refractive index portions can be formed in the exposed portions of the through holes. In the illustrated example (e.g., FIG. 3B ), the positions at which the through holes 33 are provided correspond to the positions at which the low refractive index portions are desired to be formed, and as a result, correspond to the positions of the recesses 2b in the uneven layer 2.

[0066] Next, the surface protection film 30 is disposed on the substrate 10 (for example, the first main surface 10a) (this step may be referred to as a disposing step). The surface protection film 30 is typically releasably attached to the substrate 10 via the pressure-sensitive adhesive layer 32, as described above.

[0067] In one embodiment, as shown in Fig. 3A, a surface protection film 30 having a plurality of long through holes 33 arranged in a predetermined pattern is laminated by roll-to-roll onto a long substrate 10. When the surface protection film having through holes is placed on the substrate, exposed portions 11 are formed as shown in Fig. 3B.

[0068] Next, a low refractive index portion is formed in the through hole (exposed surface) (sometimes referred to as a low refractive index portion forming step). In the low refractive index portion forming step, for example, a low refractive index portion forming material is applied to the exposed portion (see FIGS. 3B and 3C). Details of the low refractive index portion forming material are as described in Section C-2 above.

[0069] Specifically, the low refractive index portion can be formed, for example, by applying a liquid low refractive index portion-forming material (coating liquid) to the exposed portion of the substrate via a surface protection film having through holes disposed on the main surface of the substrate. More specifically, the low refractive index portion can be formed by heating the formed coating film. In other words, the low refractive index portion can be composed of a dried product, semi-cured product, or cured product of a coating film made from the low refractive index portion-forming material or coating liquid.

[0070] Any appropriate method may be employed for applying the low refractive index portion forming material. Specific examples of the application method include application methods such as spraying (spray coating), roll coating, and spin coating; and printing methods such as inkjet printing and screen printing. Any appropriate application device may be employed for application. Specific examples of the application device include a spray coater, a roll coater, a spin coater, a dispenser, an inkjet coater, and a screen printer.

[0071] In the low refractive index portion forming step, the low refractive index portion forming material (coating liquid) is preferably applied by spraying (also simply referred to as spraying). In the laminate film according to an embodiment of the present invention, a surface protection film having through holes that function as a mask is used, so spraying can further reduce the amount of low refractive index portion forming material used. Furthermore, the surface protection film does not need to be filled with paint such as ink. As a result, by using the laminate film according to an embodiment of the present invention, optical components can be produced at low cost and with high productivity.

[0072] A specific description will be given of the case where spraying is performed in the low refractive index portion forming step. The above-mentioned low refractive index portion forming material can be suitably employed for spraying. In spraying, the above-mentioned low refractive index portion forming material is sprayed onto a substrate on which a surface protective film is disposed as a mask, and a coating film is formed on exposed portions of the substrate. The coating film may be formed on exposed portions of the substrate by spraying, for example, while conveying the substrate on which the surface protective film is disposed with a roll.

[0073] In the case of spraying, the low refractive index portion forming material is preferably sprayed onto the substrate so that the rate of change in solid content concentration satisfies the following formula (1): 1.3≦rate of change in solid content concentration≦60 (1)

[0074] Preferably, the viscosity [mPa·s] of the coating film 10 seconds after spraying satisfies the following formula (2): １．２ｘ Viscosity of coating film 10 seconds after spraying ≦ 0.0549 e ３．３ｘ... (2) (In formula (2), e represents the Napier's number; x represents the solids concentration in the coating film 10 seconds after spraying.)

[0075] The viscosity of the coating film 10 seconds after spraying is specifically 3 mPa s or more, preferably 5 mPa s or more, more preferably 8 mPa s or more, even more preferably 10 mPa s or more, and particularly preferably 15 mPa s or more, and is, for example, 500 mPa s or less, preferably 300 mPa s or less, more preferably 200 mPa s or less, and particularly preferably 100 mPa s or less. If the viscosity of the coating film is within the above range, the transparency and thickness precision of the low refractive index portion can be further improved.

[0076] The viscosity of the low refractive index portion forming material before spraying is, for example, 0.5 mPa·s or more, preferably 1.0 mPa·s or more, and for example, 300 mPa·s or less, preferably 100 mPa·s or less. These viscosities can be calculated using a rheometer manufactured by Anton-Paar.

[0077] In the spraying, the distance (coating distance) between the spray head that sprays the low refractive index portion forming material and the substrate can be adjusted as appropriate. When the distance between the spray head and the substrate increases, the rate of change in the solid content concentration increases, and when the distance between the spray head and the substrate decreases, the rate of change in the solid content concentration decreases. The distance (coating distance) between the spray head and the substrate is, for example, 30 mm or more, preferably 50 mm or more, and, for example, 300 mm or less, preferably 200 mm or less.

[0078] In one embodiment, the spray head sprays the low refractive index portion forming material while moving in a plane direction including the exposed surface of the substrate. The atomization pressure of the spray is, for example, 100 kPa to 1000 kPa, the application rate of the spray is, for example, 0.1 mL / min to 20 mL / min, and the moving speed of the spray head during spraying is, for example, 10 mm / sec to 1000 mm / sec.

[0079] In this way, a laminated film having a concave-convex layer on a substrate can be produced. The method for producing a laminated film according to an embodiment of the present invention can include the step of forming the through holes (through hole forming step), the positioning step, and the low refractive index portion forming step. However, the method for producing a laminated film is not limited to the above-described method and the above-described order.

[0080] In one embodiment, forming the low refractive index portion further includes a step of heating and drying the coating film on the substrate. The heating temperature is, for example, 60°C or higher, preferably 70°C or higher, and more preferably 80°C or higher, and for example, 200°C or lower, preferably 120°C or lower, and more preferably 100°C or lower. The heating time is not particularly limited as long as the coating film can be sufficiently dried. In one embodiment, a crosslinking reaction occurs between multiple particles contained in the coating film in this step. As a result, the three-dimensional basic structure is fixed. As a result, the finally obtained low refractive index portion can maintain sufficient strength and flexibility despite having a void structure.

[0081] E. Optical Member and Method for Manufacturing Optical Member An optical member according to an embodiment of the present invention includes a substrate and a plurality of low refractive index portions disposed on a major surface of the substrate. The optical member 101 in the illustrated example (e.g., FIG. 2A ) includes a substrate 10 and a plurality of low refractive index portions 20 disposed on a first major surface 10a of the substrate 10. The low refractive index portions 20 have a porous structure. Furthermore, the ratio of the total area of ​​the low refractive index portions 20 to the total area of ​​the major surface of the substrate 10 and the low refractive index portions 20 as viewed in the thickness direction of the optical member 101 is 50% or less.

[0082] As described above, the optical member is a member in which the surface protection film is peeled off from the laminate film described above, and therefore may have a patterned low refractive index portion. The substrate and low refractive index portion in the optical member according to the embodiment of the present invention are the same as those described in Sections B and C-2 above.

[0083] The method for producing an optical element includes a step of peeling off the surface protective film (also referred to as a peeling step) after producing a laminate film in the same manner as the laminate film production method described in Section D above (see FIG. 4). That is, a method for producing an optical element according to one embodiment of the present invention may include the through-hole forming step, the arrangement step, the low refractive index portion forming step, and the peeling step. The long laminate (ultimately an optical element) obtained by the above production method may be cut to any appropriate size to form sheet-like optical elements of appropriate size.

[0084] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0085] (1) Refractive Index The low refractive index portion used in the Examples and Comparative Examples was formed on an acrylic film. The resulting laminate of the acrylic film and the low refractive index portion was cut to a size of 25 mm x 50 mm. The cut laminate was attached to the surface of a glass plate (thickness: 3 mm) via an adhesive. The center of the back surface of the glass plate (diameter: approximately 20 mm) was filled in with a black oil paint pen to create a sample that did not reflect light from the back surface of the glass plate. The sample was placed in an ellipsometer (VASE, manufactured by J.A. Woollam Japan), and the refractive index was measured at a wavelength of 550 nm and an incident angle of 50 to 80 degrees.

[0086] (2) Thickness: Measurement was performed using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000").

[0087] (3) Dot diameter, pitch, number of patterns, and area ratio of low refractive index portion The dot diameter and pitch of the low refractive index portion were confirmed by observing the shape of the recesses in the uneven layer of the laminated film in a planar view using a laser microscope (model number VK-X1000) manufactured by KEYENCE Corporation and processing the image. The dot diameter of the low refractive index portion is the diameter a of the circle (i.e., the diameter equivalent to an isocircular ellipse) when the shape of the recesses in a planar view is a circle, as shown in FIG. 5. The pitch refers to the center-to-center distance between adjacent recesses in the length direction (or width direction) in a planar view, as shown in FIG. 5. The center-to-center distance between adjacent recesses in the length direction is referred to as the length direction pitch px, and the center-to-center distance between adjacent recesses in the width direction is referred to as the width direction pitch py. Note that when the length direction pitch and the width direction pitch are equal, they are simply referred to as the pitch. The number of patterns in the low refractive index portion is 1 cm. ２ The area ratio of the low refractive index portion is calculated by observing the laminated film with a laser microscope, calculating the total area of ​​the concave-convex layer and the total area of ​​the concave portions in a plan view based on the image processed, and then calculating the ratio of the total area of ​​the concave-convex layer to the total area of ​​the concave-convex layer.

[0088] [Manufacturing Example 1] Preparation of low refractive index portion forming material (coating liquid) (1) Gelation of silicon compound Mixed solution A was prepared by dissolving 0.95 g of methyltrimethoxysilane (MTMS), a precursor of the silicon compound, in 2.2 g of dimethyl sulfoxide (DMSO). 0.5 g of 0.01 mol / L oxalic acid aqueous solution was added to this mixed solution A, and the mixture was stirred at room temperature for 30 minutes to hydrolyze the MTMS, producing a mixed solution B containing tris(hydroxy)methylsilane. 0.38 g of 28 wt% ammonia water and 0.2 g of pure water were added to 5.5 g of DMSO, and then the mixed solution B was further added and stirred at room temperature for 15 minutes to gel the tris(hydroxy)methylsilane, thereby obtaining a mixed solution C containing a gel-like silicon compound. (2) Aging Treatment The mixed solution C containing the gel-like silicon compound prepared as above was incubated at 40 ° C. for 20 hours to undergo an aging treatment. (3) Pulverization Next, the gel-like silicon compound aged as described above was crushed into granules of several mm to several cm in size using a spatula. Next, 40 g of isopropyl alcohol (IPA) was added to the mixed solution C, and after light stirring, the mixture was left to stand at room temperature for 6 hours, and the solvent and catalyst in the gel were decanted. The same decantation process was performed three times to replace the solvent, yielding mixed solution D. The gel-like silicon compound in mixed solution D was then crushed (high-pressure media-less crushing). The crushing process (high-pressure media-less crushing) was performed using a homogenizer (manufactured by SMT Corporation, trade name "UH-50"), by weighing 1.85 g of the gel-like compound in mixed solution D and 1.15 g of IPA into a 5 cc screw bottle, and then crushing for 2 minutes under conditions of 50 W and 20 kHz. This crushing process crushed the gel-like silicon compound in mixed solution D, and mixed solution D became a crushed sol solution E. The volume average particle size, which indicates the particle size variation of the pulverized material contained in Sol E, was confirmed to be 0.50 to 0.70 μm using a dynamic light scattering Nanotrac particle size analyzer (manufactured by Nikkiso Co., Ltd., Model UPA-EX150).Furthermore, 0.015 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd., product name: WPBG266) and 0.005 g of a 5 wt % MEK solution of a bis-crosslinking accelerator ((trimethoxysilyl)hexane) were added to 0.75 g of sol solution E to obtain low refractive index portion-forming coating solution 1. The refractive index of the low refractive index portion formed using this coating solution was 1.2.

[0089] Example 1 Base film 1 was prepared as the substrate, protective film 1 as the surface protective film, and the coating liquid of Production Example 1 above as the low refractive index portion-forming material. Through holes were formed in the surface protective film so as to form a predetermined pattern having the dot diameters shown in Table 1 and equal longitudinal and widthwise pitches. The surface protective film with the through holes formed therein was then bonded to the substrate via the adhesive layer of the surface protective film. The coating liquid of the low refractive index portion-forming material of Production Example 1 was then spray-coated into the through holes in the surface protective film to form a coating film of the low refractive index portion-forming material. Specifically, spray coating was performed as follows. The low refractive index portion-forming material and the substrate (hereinafter referred to as a laminate) to which the surface protective film having through holes was bonded were set in a spray coater (manufactured by Apeiros, product name API-240 series). The distance (coating distance) between the spray head (nozzle) and the substrate (exposed portion of the substrate) in the laminate was 125 mm. Next, the low refractive index portion-forming material was spray-coated onto the exposed portion of the substrate of the laminate under coating conditions of an atomization pressure of 100 kPa and a coating rate of 7 mL / min to form a coating film on the exposed portion of the substrate. The coating film on the exposed portion of the substrate in the laminate was then dried at 90°C for 10 minutes, and then dried at 70°C for 24 hours. This resulted in a laminate film having a concave-convex layer on the substrate, which had a surface protection film constituting the convex portions and a low refractive index portion constituting the concave portions. The thickness of the low refractive index portion was 2.0 μm. The resulting laminate film was subjected to the measurements and evaluations (1) to (3) above.

[0090] Examples 2 to 4 Laminated films were produced in the same manner as in Example 1, except that the dot diameter and pitch of the pattern shape of the through holes in the surface protective film were changed as shown in Table 1. The thickness of the low refractive index portion in each example is as shown in Table 1. The obtained laminated films were subjected to the same evaluations as in Example 1.

[0091] Comparative Example 1: Base film 1 was used as the substrate, and the coating liquid of Production Example 1 was used as the low-refractive-index portion-forming material. The low-refractive-index portion-forming material was applied to the entire first main surface of the substrate to form a coating film (layer) made of the low-refractive-index portion-forming material. Subsequently, a coating material (curable resin composition: urethane-based photocurable resin (Daicel Allnex Corporation product name KRM8904)) that penetrates the low-refractive-index portion-forming material was injected into the coating material inlet of an inkjet device, and the ink was ejected onto the coating film made of the low-refractive-index portion-forming material on the substrate using an inkjet method so that the ejected droplets had the dot diameter and pitch listed in Table 1. This formed a coating film made of the coating material with a predetermined spacing (pattern), producing a laminate. Subsequently, the laminate was heated at 100°C for 5 minutes to perform heat aging. This allowed the coating material to penetrate into the low-refractive-index layer (porous layer). The coating material was filled into a portion of the low-refractive-index layer (porous layer), yielding a laminate film with patterned low-refractive-index portions. It should be noted that no surface protective film was used in Comparative Example 1. The thickness of the low refractive index portion is as shown in Table 1. The obtained laminated film was subjected to the same evaluation as in Example 1.

[0092] The materials shown in Table 1 are as follows: (Substrate) Base film 1: Glass substrate (acrylic film (manufactured by Corning Incorporated, product name EAGLE XG. Material: alkali-free glass, thickness: 0.7 mm.) (Surface protection film) Protective film 1: Surface protection film (manufactured by Nitto Denko Corporation, product name E-MASK).

[0093]

[0094] As is clear from Table 1, according to the examples of the present invention, a laminated film can be obtained that can suppress defects in the pattern shape and realize optical members that can improve productivity.

[0095] The laminated film according to the embodiment of the present invention can be suitably used to produce an optical element, and the optical element according to the embodiment of the present invention can be suitably used as an optical element having a light distribution function.

[0096] REFERENCE SIGNS LIST 10 Substrate 11 Exposed portion 10a First main surface 10b Second main surface 2 Concave-convex layer 2a Convex portion 2b Concave portion 20 Low refractive index portion 30 Surface protective film 31 Film layer 32 Pressure-sensitive adhesive layer 33 Through-hole 100 Laminated film 101 Optical member

Claims

1. A laminated film comprising: a substrate having a first main surface and a second main surface opposite the first main surface; and an uneven layer disposed on the first main surface; wherein the uneven layer has convex portions formed by a surface protection film and concave portions formed by low refractive index portions disposed between the convex portions, the low refractive index portions have a porous structure, and the ratio of the total area of ​​the concave portions to the total area of ​​the uneven layer as viewed in the thickness direction of the laminated film is 50% or less.

2. The laminated film according to claim 1, wherein the low refractive index portion is disposed on the first main surface of the substrate.

3. The laminated film according to claim 2, wherein the low refractive index portions are formed in an island shape in a plan view when viewed from the thickness direction.

4. The laminated film according to claim 3, wherein the diameter of the equivalent of an equal-circumference ellipse of the low refractive index portion in a plan view is 1 μm or more and 500 μm or less.

5. The laminated film according to claim 1, wherein the surface protection film comprises a film layer and a pressure-sensitive adhesive layer disposed on the substrate side of the film layer, and the thickness of the low refractive index portion is smaller than the thickness of the film layer.

6. The laminated film according to claim 5, wherein the thickness of the low refractive index portion is smaller than the thickness of the pressure-sensitive adhesive layer.

7. A method for manufacturing a laminated film according to any one of claims 1 to 6, comprising: a through-hole forming step of forming a through-hole in the surface protective film; an arrangement step of arranging the surface protective film with the through-hole formed therein on the substrate; and a low-refractive-index portion forming step of forming a low-refractive-index portion by applying a material for forming a low-refractive-index portion to an exposed portion of the substrate due to the through-hole.

8. The method for producing a laminated film according to claim 7, wherein the low refractive index portion forming step includes applying the low refractive index portion forming material by spraying.

9. An optical element comprising a substrate and a plurality of low refractive index portions arranged on a main surface of the substrate, wherein the low refractive index portions have a porous structure, and the ratio of the area of ​​the low refractive index portions to the total area of ​​the main surface of the substrate and the low refractive index portions as viewed in the thickness direction of the optical element is 50% or less.

10. The optical element according to claim 9, wherein the low refractive index portions are formed in an island shape in a plan view when viewed in the thickness direction.

11. The optical element according to claim 10, wherein the diameter of an equivalent ellipse of an equal circumference of the low refractive index portion in a plan view is 1 μm or more and 500 μm or less.

12. A method for manufacturing an optical element according to any one of claims 9 to 11, comprising: a through-hole forming step of forming a through-hole in a surface protection film that protects the substrate; a disposing step of disposing the surface protection film, with the through-hole formed therein, on the substrate; a low-refractive-index portion forming step of forming a low-refractive-index portion by applying a material for forming a low-refractive-index portion to an exposed portion of the substrate due to the through-hole; and a peeling step of peeling off the surface protection film after the low-refractive-index portion forming step.

13. The method for manufacturing an optical element according to claim 12, wherein the low refractive index portion forming step includes applying the low refractive index portion forming material by spraying.

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