JP2018180112A - Optical retardation member, and method of manufacturing optical retardation member - Google Patents

Abstract

An optical phase difference member having high transmittance, capable of producing a desired phase difference, and having high mechanical strength and moisture resistance is provided. An optical phase difference member (10A) according to the present invention is formed on a substrate (40) having a first surface (41) and a second surface (42) located on the opposite side of the first surface (41), and formed on the first surface (41). A first uneven structure 50 made of a first inorganic material, and a second uneven structure 52 formed on the second surface 42 and made of a second inorganic material. The uneven structure 50 includes a plurality of protrusions 60 extending in a first direction parallel to the first surface 41 and having a width decreasing in a direction away from the first surface 41 of the base material 40. The second uneven structure 52 includes a plurality of protrusions 62 extending in the first direction and having a width decreasing in a direction away from the second surface 42 of the base material 40. [Selection diagram] FIG. 1A

Description

  The present invention relates to an optical retardation member and a method of manufacturing the same.

  The optical retardation plate has a very large number of uses, and various uses such as a projector (projection type display), a reflection type liquid crystal display, a semi-transmission type liquid crystal display, a pickup for an optical disc, a PS conversion element, etc. Is used for

  The optical retardation plate should have a periodic structure shorter than the working wavelength artificially formed of a birefringent crystal existing in the natural world such as calcite, mica or quartz, or formed of a birefringent polymer And those using an oblique columnar structure film.

  As an optical retardation plate artificially provided with a periodic structure, there is one provided with a concavo-convex structure on a transparent substrate. The concavo-convex structure used for the optical retardation plate has a period shorter than the used wavelength, and has, for example, a stripe pattern as shown in FIG. Such a concavo-convex structure has refractive index anisotropy, and when light L is incident perpendicularly to the substrate 420 of the optical retardation plate 400 of FIG. 3, in the concavo-convex structure, it is parallel to the periodic direction of the concavo-convex structure. Since the polarization component and the polarization component perpendicular to the periodic direction of the uneven structure propagate at different speeds, a phase difference occurs between the two polarization components. This phase difference can be controlled by adjusting the height (depth) of the concavo-convex structure, the refractive index difference of the material forming the convex portion and the material (air) between the convex portion, and the like. The optical retardation plate used for the above-mentioned device such as a projector needs to generate a phase difference of λ / 4 or λ / 2 with respect to the used wavelength λ, but such a sufficient phase difference can be generated. In order to form an optical retardation plate, the difference between the refractive index of the material constituting the convex portion and the refractive index of the material (air) between the convex portions and the height (depth) of the concavo-convex structure are made sufficiently large. There is a need. As such an optical phase difference plate, in patent document 1, what coat | covered the surface of uneven structure with high refractive index material is proposed.

As an optical retardation plate using an oblique columnar structure film, Patent Document 2 discloses a lithium niobate Ta ₂ O ₃ film having an oblique columnar structure with a low film density formed by evaporation or sputtering from an oblique direction. The one provided on both sides of the substrate is described. In Patent Document 2, providing the oblique columnar structure film on both sides of the substrate makes it possible to reduce the thickness of the oblique columnar structure film as compared to the case where it is provided only on one side. It is described that peeling can be prevented, and that the optical retardation plate provided with oblique columnar structure films on both sides of the substrate has higher transmittance than the optical retardation plate provided with oblique columnar structure films only on one side. ing.

Japanese Examined Patent Publication 7-99402 JP-A-8-122523

  As described above, in order for the optical retardation member to have a sufficient phase difference, it is necessary to make the height of the concavo-convex structure sufficiently large, but such a concavo-convex structure tends to be difficult to form and the mechanical strength is low. is there. When the optical retardation member is used for a projector or the like, it is desirable that the optical retardation member has high transmittance in a wide wavelength range, but the high refractive index of the retardation plate disclosed in Patent Document 1 is high. Since the layer is in contact with air, most of the light incident on the retardation plate is reflected at the interface between the high refractive index layer and air, so the transmittance of the retardation plate is low. In addition, a part of the light is also reflected on the surface on the opposite side of the surface on which the concavo-convex structure of the transparent substrate is formed, so the transmittance is further reduced.

  Since the oblique columnar structure film of the optical retardation plate described in Patent Document 2 is a sparse film having a low film density, it is said that the mechanical strength is low and it easily deteriorates in a high humidity environment.

  An object of the present invention is to provide an optical retardation member which has high transmittance, can produce a desired phase difference, and has high mechanical strength and moisture resistance, and a method of manufacturing the same.

According to a first aspect of the invention,
A substrate having a first surface and a second surface located opposite the first surface;
A first uneven structure formed on the first surface and made of a first inorganic material;
And a second uneven structure formed on the second surface and made of a second inorganic material,
The first concavo-convex structure includes a plurality of projections which extend in a first direction parallel to the first surface and whose width decreases in a direction away from the first surface of the base material.
There is provided an optical retardation member including a plurality of convex portions in which the second concavo-convex structure extends in the first direction and the width decreases in a direction away from the second surface of the base. Ru.

According to a second aspect of the present invention, there is provided a method of producing an optical retardation member according to the first aspect, the method comprising:
Forming a first uneven structure composed of a first inorganic material on the first surface of the substrate;
There is provided a method of manufacturing an optical retardation member, comprising forming a second uneven structure composed of a second inorganic material on a second surface opposite to the first surface of the substrate. Ru.

  The optical retardation member of the present invention can have high transmittance and can produce a desired retardation by forming the concavo-convex structure on both surfaces of the base material. In addition, the concavo-convex structure has high mechanical strength and moisture resistance. Therefore, the optical retardation member of the present invention is suitable for various uses such as a projector.

FIG. 1A is a view conceptually showing the cross-sectional structure of the optical retardation member of the first embodiment. FIG. 1B is a view conceptually showing the cross-sectional structure of the optical retardation member of the second embodiment. FIG. 1C is a diagram conceptually showing the cross-sectional structure of the optical retardation member of the third embodiment. FIG. 2 is a flowchart showing a method of manufacturing the optical retardation member. FIG. 3: is a figure which shows notionally an example of the optical phase difference member of a prior art.

  Hereinafter, an optical retardation member and a method of manufacturing the same will be described with reference to the drawings.

[Optical retardation member]
(1) Optical Retardation Member 10A (First Embodiment)
The optical retardation member 10A shown in FIG. 1A is formed on a first surface 41 and a plate-like base material 40 having a first surface 41 and a second surface 42 opposite to the first surface 41. A first uneven structure body 50 and a second uneven structure body 52 formed on the second surface 42 are provided. The surfaces of the first uneven structure body 50 and the second uneven structure body 52 are both exposed. That is, no other layer is formed on any of the first uneven structure body 50 and the second uneven structure body 52, and the first uneven structure body 50 and the second uneven structure body 52 are the outermost layer.

<Base material>
The substrate 40 is not particularly limited, and a known plate-like plate (a flat plate that transmits visible light) having a refractive index at a wavelength of 550 nm (hereinafter referred to as “refractive index” as appropriate) is in the range of 1.4 to 1.8. Shape) can be suitably used. For example, a base material made of a transparent inorganic material such as quartz or glass; a base material made of any transparent resin material, or the like can be used. When the optical retardation member 10A is used in a projector, the optical retardation member 10A is required to have high light resistance and high heat resistance, so the substrate 40 is desirably a substrate having high light resistance and high heat resistance. . In this respect, a substrate made of an inorganic material is preferred. The thickness of the substrate 40 is preferably in the range of 1 μm to 20 mm.

<First uneven structure body>
The first concavo-convex structure 50 has a plurality of convex portions 60 and concave portions 70 between the adjacent convex portions, whereby the concavo-convex pattern 80 is defined on the surface of the first concavo-convex structure 50.

The first uneven structure body 50 may be made of a material having a refractive index in the range of 1.6 to 1.9. Further, assuming that the refractive index of the first concavo-convex structure 50 is n ₁ and the refractive index of the base 40 is n ₀ , the value of n ₁ −n ₀ may be in the range of −0.4 to 0.4. . When the value of n ₁ −n ₀ is in the range of −0.4 to 0.4, the difference in refractive index between the concavo-convex structure 50 and the base material 40 is sufficiently small, so the interface between the concavo-convex structure 50 and the base material 40 The reflectance of the optical retardation member 10A is further reduced. Also, the value of n ₁ -n ₀ may be in the range of -0.1 to 0.4, and may be in the range of 0.1 to 0.4. When the value of n ₁ −n ₀ is −0.1 or more, particularly 0.1 or more, the difference between the refractive index of the convex portion 60 and the air layer 90 to be described later is sufficiently large. It becomes easy to generate a phase difference. Examples of the material constituting the first uneven structure body 50 include Si-based materials such as silica, SiN and SiON, Ti-based materials such as TiO ₂ , ITO (indium-tin-oxide) -based materials, ZnO, Inorganic materials such as ZnS, ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Cu ₂ O, MgS, AgBr, CuBr, BaO, Nb ₂ O ₅ , and SrTiO ₂ can be used. These inorganic materials may be xerogels obtained by curing the precursors (sols) of these inorganic materials by a sol-gel method. The xerogel has a three-dimensional network composed of strong covalent bonds such as Si-O bonds and has sufficient mechanical strength. Moreover, you may use the material which composited the thermoplastic resin which is described in WO2016 / 056277, an ultraviolet curable resin, etc. to the said inorganic material. Known fine particles and fillers may be contained in the above-mentioned inorganic material in order to adjust the refractive index, to increase the hardness, and the like. Furthermore, the above-mentioned material may contain an ultraviolet absorbing material. The ultraviolet light absorbing material has the function of suppressing deterioration of the first uneven structure body 50 by absorbing ultraviolet light and converting light energy into a harmless form such as heat. As an ultraviolet absorber, arbitrary things, such as an ultraviolet absorber illustrated by WO2016 / 056277, can be used. When the optical retardation member 10A is used in a projector, it is desirable that the first concavo-convex structure 50 have high light resistance and heat resistance. In this respect, since the first uneven structure body 50 is made of an inorganic material, it is excellent in light resistance and heat resistance.

  Each convex portion 60 and each concave portion 70 of the first concavo-convex structure 50 extend in the Y direction (depth direction) of FIG. 1A parallel to the first surface 41, and the plurality of convex portions 60 and concave portions 70 They are arranged at a cycle shorter than the design wavelength (the wavelength of light causing a phase difference by the optical retardation member 10A).

  Each convex portion 60 has a width (length in the X direction in FIG. 1A) decreasing upward from the first surface 41 of the base 40 (in a direction away from the first surface 41, ie, in the Z direction of FIG. 1A). Has a tapered shape. That is, the cross section in the ZX plane orthogonal to the extending direction of each convex portion 60 may be substantially trapezoidal. In the present application, “substantially trapezoidal” has a pair of opposite sides substantially parallel to the first surface 41 of the base material 40, and among the opposite sides, the side (lower base) closer to the first surface 41 of the base material 40 It means a substantially square shape longer than the other side (upper base), and the angle between the lower base and the two oblique sides is an acute angle. Each side of the substantially rectangular shape may be curved, and each vertex may be rounded. The convex portion 60 having such a tapered shape causes the average refractive index to be continuously lowered in the direction away from the first surface 41. Therefore, since reflection of light at the interface between the air and the first uneven structure body 50 is suppressed, the transmittance of the optical retardation member 10A is improved. Also, the length of the upper base may be zero. That is, in the present application, “substantially trapezoidal” is a concept including “substantially triangular”. The length of the upper base is preferably greater than 0. A convex portion having a substantially trapezoidal cross section whose upper base is greater than 0 has the following advantages over a convex portion having a substantially triangular cross section. That is, it is easy to form a template used to form the convex portion by the imprint method, and to have high mechanical strength such as surface pressing resistance of the convex portion.

  It is desirable that the height (concave / convex height) of the convex portion 60 be in the range of 100 to 2000 nm. When the height of the convex portion 60 is less than 100 nm, it tends to be difficult to generate a desired phase difference when visible light is incident on the optical retardation member 10A. When the height of the convex portion 60 exceeds 2000 nm, since the aspect ratio of the convex portion 60 is large, the formation of the concavo-convex pattern 80 tends to be difficult. The aspect ratio of the convex portion 60 may be in the range of 1 to 5. When the aspect ratio of the convex portion 60 is 1 or more, a sufficient phase difference can be generated by the optical retardation member. While the convex part 60 can have sufficient mechanical strength because the aspect ratio of the convex part 60 is five or less, formation of the uneven structure body 50 becomes easy. In the present application, “aspect ratio of convex portion” means the ratio of convex portion height Ha to convex portion width W, and “convex portion height Ha” is the distance from the bottom surface to the upper surface of convex portion 60 The term “convex part width W” means the thickness of the convex part 60 at a height of Ha / 2 from the bottom of the convex part 60 (see FIG. 1A). The width of the upper surface 60t of the convex portion 60 (the length of the upper base of the substantially trapezoidal cross section in the plane orthogonal to the extending direction of the convex portion 60) is preferably 50 nm or less. When the width of the upper surface 60t of the convex portion 60 is 50 nm or less, the transmittance of the optical retardation member 10A can be easily increased. Moreover, it is preferable that the uneven | corrugated pitch of the uneven | corrugated pattern 80 exists in the range of 50-1000 nm. An uneven pattern having a pitch of less than 50 nm tends to be difficult to form by the nanoimprinting method. When the pitch exceeds 1000 nm, it tends to be difficult to secure sufficient colorless transparency as an optical retardation member.

  An air layer 90 exists in the space (gap) between the opposing side surfaces 60s of the adjacent convex portions 60. The periodic arrangement of the air layer 90 and the projections 60 causes birefringence, which can cause a phase difference. The width Wa of the air layer 90 is preferably in the range of 20 to 200 nm. Note that “the width Wa of the air layer 90” means the thickness of the air layer 90 at a height of Ha / 2 from the bottom surface of the protrusion 60 (the distance between the facing side surfaces 60s of the adjacent protrusions 60). means.

<2nd uneven structure body>
The second uneven structure body 52 may be made of the above-described material that can be used as a material of the first uneven structure body 50. Further, the second concavo-convex structural body 52 has a plurality of convex portions 62 and concave portions 72 between the adjacent convex portions in the same manner as the first concavo-convex structural body 50, whereby the surface of the second concavo-convex structural body 52 A pattern 82 is defined. The shape and size of each convex portion 62 of the second concavo-convex structure 52 and the concavo-convex pitch etc. of the concavo-convex pattern 82 are the shape and size of each convex part 60 described above for the first concavo-convex structure 50 It may be similar to etc. The uneven pattern 82 of the second uneven structure 52 may be the same pattern as the uneven pattern 80 of the first uneven structure 50. In that case, since the first uneven structure body 50 and the second uneven structure body 52 can be manufactured from a common base mold, there is no need to prepare a base mold for each of the first uneven structure body 50 and the second uneven structure body 52. The manufacturing cost of the optical retardation member can be suppressed.

  An air layer 92 exists in the space (gap) between the facing side surfaces 62s of the adjacent convex portions 62. The periodic arrangement of the air layer 92 and the convex portions 62 causes birefringence, which can cause a phase difference. The width Ws of the air layer 92 is preferably in the range of 20 to 200 nm. The “width Ws of the air layer 92” means the thickness of the air layer 92 at a height Hs / 2 from the bottom surface of the protrusion 62, where Hs is the height from the bottom surface to the top surface of the protrusion 62 It means the distance between the facing side surfaces 62s of the adjacent convex portions 62).

  The size of the phase difference generated by the optical retardation member 10A is the sum of the phase difference generated by the first concavo-convex structure 50 and the phase difference generated by the second concavo-convex structure 52. Therefore, the optical retardation member 10A can generate a large phase difference. The phase difference generated by the optical retardation member 10A may be any magnitude, but is preferably λ / 4 or λ / 2 (λ indicates the wavelength of incident light). For example, when the first uneven structure body 50 and the second uneven structure body 52 respectively cause a phase difference of λ / 4, the optical retardation member 10A can generate a phase difference of λ / 2.

  Usually, in order to generate a large phase difference such as λ / 2 using structural birefringence due to asperities, it is necessary to sufficiently increase the asperity height (depth). Large irregularities are difficult to form due to low releasability and mechanical strength. However, since the optical retardation member 10 </ b> A produces a phase difference that is the sum of the phase difference generated by the first uneven structure body 50 and the phase difference generated by the second uneven structure body 52, the first uneven structure body 50 is And the uneven | corrugated height of the 2nd uneven | corrugated structure 52 can be made low (for example, to the half uneven | corrugated height in the case where an optical retardation member has only one uneven | corrugated structure). Therefore, the optical retardation member 10A of the present embodiment can generate a large retardation while being easy to manufacture.

(2) Optical Retardation Member 10B (Second Embodiment)
An optical retardation member 10B shown in FIG. 1B includes a plate-like base 40 similar to the optical retardation member 10A shown in FIG. 1A, a first uneven structure body 50, and a second uneven structure body 52, and further The high refractive index layer 30 formed on the upper surface 60t and the side surface 60s of the convex portion 60 of the first concavo-convex structure 50, and the middle refractive index layer formed on the high refractive index layer 30 on the upper surface 60t of the convex portion 60 And 20. The base 40, the first concavo-convex structure 50, and the second concavo-convex structure 52 are the same as the above-described optical retardation member 10A (first embodiment), and thus the description thereof is omitted. The refractive index of the first uneven structure body 50 and the second uneven structure body 52 of the optical retardation member 10B may be in the range of 1.2 to 1.9.

<High refractive index layer>
The high refractive index layer 30 is a layer having a refractive index higher than that of the first uneven structure body 50. The high refractive index layer 30 is preferably made of a material having a refractive index of 2.3 or more. Examples of the material constituting the high refractive index layer 30 include metals such as Ti, In, Zr, Ta, Nb, and Zn, and oxides such as oxides, nitrides, sulfides, oxynitrides, and halides of such metals. Materials can be used.

The high refractive index layer 30 covers the convex portion 60. That is, the high refractive index layer 30 covers the upper surface 60 t and the side surface 60 s of the convex portion 60. By covering the convex portion 60 with the high refractive index layer 30, the birefringence caused by the periodic arrangement of the convex portion 60 and the air layer 90b described later becomes large. Therefore, since the height of the convex portion 60 can be reduced, that is, the aspect ratio of the convex portion 60 can be reduced, the formation of the first concavo-convex structure 50 is facilitated. It is preferable that thickness T _ht of the high refractive index layer 30 formed on the upper surface 60t of the convex part 60 exists in the range of 50-250 nm.

When the optical retardation member 10B is used for the purpose of giving a phase difference to light of a specific wavelength λ, the thickness T _hs of the high refractive index layer 30 formed on the side surface 60s of the convex portion 60 is 0.03 λ to It is preferable that it is 0.11 λ. When the thickness T _hs of the high refractive index layer 30 is in the above range, it becomes easy to further increase the transmittance of the optical retardation member 10B. The “thickness T _hs of the high refractive index layer 30 on the side surface 60s of the convex portion 60” in the optical retardation member 10B is the height from the bottom of the convex portion 60 to the top of the middle refractive index layer 20 as Hb. In this case, the thickness of the high refractive index layer 30 at the position of Hb / 2 from the bottom of the convex portion 60 is meant.

  The middle refractive index layer 20 is a layer having a lower refractive index than the high refractive index layer 30. The middle refractive index layer 20 is preferably made of a material having a refractive index in the range of 1.5 to 1.7. The refractive index of the material constituting the middle refractive index layer 20 is more preferably 1.6. Examples of the material constituting the middle refractive index layer 20 include aluminum oxide, zinc oxide, magnesium oxide, silicon oxynitride, lanthanum fluoride, silicon oxide, germanium oxide and the like.

The middle refractive index layer 20 is formed on the high refractive index layer 30 on the upper surface 60 t of the convex portion 60. Since the reflection of light is thereby suppressed, the optical retardation member 10B can have high transmittance. When the optical retardation member 10A is used for the purpose of giving a phase difference to light of a specific wavelength λ, the thickness T _mt of the middle refractive index layer 20 formed on the high refractive index layer 30 on the upper surface 60t of the convex portion 60 Is preferably in the range of 0.9 λ / 4 n to 1.3 λ / 4 n (n represents the refractive index of the middle refractive index layer 20). When the thickness T _mt of the middle refractive index layer 20 is in the above range, it is easy to further increase the transmittance of the optical retardation member 10B.

  The middle refractive index layer 20 may be formed also on the high refractive index layer 30 on the side surface 60 s of the convex portion 60. The thickness of the middle refractive index layer 20 formed on the high refractive index layer 30 on the side surface 60s of the convex portion 60 (the thickness of the middle refractive index layer 20 on the side surface 60s of the convex portion 60) specifies the optical retardation member 10A. When using for the purpose of giving a phase difference to the light of wavelength (lambda), it is preferable that it is 0.03 (lambda) or less. When the thickness of the middle refractive index layer 20 on the side surface 60s of the convex portion 60 exceeds 0.03 λ, the retardation caused by the optical retardation member 10B tends to be small. Note that “the thickness of the middle refractive index layer 20 on the side surface 60s of the convex portion 60” in the optical retardation member 10B is a half of the height from the bottom surface of the convex portion 60 to the top of the middle refractive index layer 20. The thickness of the middle refractive index layer 20 at the height position is meant.

  An air layer 90 b exists in a space (gap) between the high refractive index layers 30 formed on the opposing side surfaces 60 s of the adjacent convex portions 60. The periodic arrangement of the high refractive index layer 30 covering the air layer 90 b and the convex portion 60 causes birefringence, which can cause a phase difference. The width Wb of the air layer 90b is preferably in the range of 0.08 to 0.18 times the wavelength of the incident light. When the width Wb of the air layer 90b is in the above range, it is easy to further increase the transmittance of the optical retardation member 10B, and it is possible to generate a sufficiently large phase difference. . The “width Wb of the air layer 90b” in the optical retardation member 10B is Hb / b from the bottom of the convex 60, assuming that the height from the bottom of the convex 60 to the top of the middle refractive index layer 20 is Hb. This means the thickness of the air layer 90b at a height of 2 (the distance between the surfaces of the high refractive index layer 30 formed on the opposing side surfaces 60s of the adjacent convex portions 60).

(3) Optical Retardation Member 10C (Third Embodiment)
An optical retardation member 10C shown in FIG. 1C includes a plate-like base 40 similar to the optical retardation member 10A shown in FIG. 1A, a first uneven structure body 50, and a second uneven structure body 52, and further The high refractive index layer 30 formed on the upper surface 60t and the side surface 60s of the convex portion 60 of the first uneven structure body 50, and the laminate 25 formed on the high refractive index layer 30 on the upper surface 60t of the convex portion 60 Equipped with The base 40, the first uneven structure body 50, and the second uneven structure body 52 are the same as the optical retardation member 10A (first embodiment) described above, and the high refractive index layer 30 is the optical retardation member 10B described above Since the second embodiment is the same as the second embodiment), the description is omitted. The refractive index of the first uneven structure body 50 and the second uneven structure body 52 of the optical retardation member 10C may be in the range of 1.2 to 1.9.

<Laminate>
The stacked body 25 is formed on the high refractive index layer 30 on the upper surface 60 t of the convex portion 60. The stack 25 may be composed of 2n + 1 (n is a positive integer) layers, that is, an odd number of layers of 3 or more. In FIG. 1C, the laminate 25 is composed of three layers: a first layer 22, a second layer 24, and a third layer 26. The first layer 22 is formed directly on the high refractive index layer 30, the second layer 24 is formed directly on the first layer 22, and the third layer 26 is formed directly on the second layer 24.

  The refractive index of the first layer 22 is lower than that of the high refractive index layer 30, and the refractive index of the third layer 26 is lower than the refractive index of the second layer 24. Thereby, the optical retardation member 10C can have high transmittance in a wide wavelength range.

  The refractive index of the second layer 24 may be higher than the refractive index of the first layer 22, or the refractive index of the second layer 24 may be lower than the refractive index of the first layer 22.

  In the case where the refractive index of the second layer 24 is higher than the refractive index of the first layer 22, the laminate 25 is formed by alternately laminating layers having a relatively high refractive index and layers having a relatively low refractive index. It has a structure. In this case, the refractive index of the first layer 22 and the third layer 26 may be in the range of 1.3 to 1.55. When the refractive index of the first layer 22 or the third layer 26 exceeds 1.55, the average transmittance of the optical retardation member 10C (average of transmittance of light at a wavelength of 430 nm to 680 nm) tends to be low. Materials with refractive index less than 1.3 tend to be less stable. The refractive index of the second layer 24 may be 2.1 or more, preferably in the range of 2.1 to 2.6. When the refractive index of the second layer 24 is less than 2.1, the average transmittance of the optical retardation member 100 tends to be low. Materials with refractive index greater than 2.6 tend to have low transparency in the visible light region of the material itself. Also, the first layer 22 and the third layer 26 may be formed of the same material, and the second layer 24 may be formed of the same material as the high refractive index layer 30. Thereby, since the optical retardation member 10C can be manufactured with a small number of types of materials, the manufacturing cost can be reduced.

  When the refractive index of the second layer 24 is lower than the refractive index of the first layer 22, in the stacked body 25, the layer farther from the high refractive index layer 30 has a lower refractive index. In this case, the refractive index of the third layer 26 which is the outermost layer (uppermost layer) of the laminate 25 may be in the range of 1.3 to 1.4.

Examples of the material constituting the first layer 22 and the third layer 26 include oxides of SiO ₂ and MgF ₂ such as Si, Al, Li, Mg, Ca and K, and fluorides. Examples of the material constituting the second layer 74 include metals such as Ti, In, Zr, Ta, Nb and Zn, and inorganic materials such as oxides, nitrides, sulfides, oxynitrides, and halides of the metals. It can be mentioned.

The thickness T _st1 of the first layer 22 formed on the high refractive index layer 30 on the upper surface 60 t of the convex portion 60 may be in the range of 20 to 40 nm, and the thickness T _st2 of the second layer 24 thereon. May be in the range of 35 to 55 nm, and the thickness T _st3 of the third layer 26 _thereon may be in the range of ₁₀₀ to 140 nm, and the first layer 22, the second layer 24, the third layer 26. The thickness T _st of the laminate 25 which is the sum of the thicknesses of H and W may be in the range of 155 to 210 nm. In this case, the average transmittance of the optical retardation member 10C tends to be high. Also, the thickness T _st1 of the first layer 22 may be in the range of 25 to 35 nm, the thickness T _st2 of the second layer 24 may be in the range of 35 to 45 nm, and the thickness T _{st3 of} the third layer 26 May be in the range of 115 to 125 nm, and the thickness T _st of the laminate 25 may be in the range of 185 to 195 nm. In this case, the average transmittance of the optical retardation member 10C tends to be higher.

The laminate 25 may be formed also on the high refractive index layer 30 on the side surface 60 s of the protrusion 60. The thickness of the laminate 25 formed on the high refractive index layer 30 on the side surface 60s of the protrusion 60 (the thickness of the laminate 25 on the side surface 60s of the protrusion 60) T _ss is in the range of 5 to 40 nm Is preferred. When the thickness T _ss of the laminate 25 is in the above range, the transmittance of the optical retardation member 10C can be increased while suppressing the reduction of the retardation due to the film deposition of the laminate 25 on the side surface 60s. In addition, when the refractive index of the second layer 24 is increased, a phase difference due to structural birefringence is also generated by the second layer 24 formed on the side surface, so that the phase difference is reduced due to the laminated body 25 being formed on the side surface. It can be suppressed. The “thickness T _ss of the laminated body 25 at the side surface 60s of the convex portion 60” in the optical retardation member 10C is the convex portion assuming that the height from the bottom of the convex portion 60 to the uppermost portion of the laminated body 25 is Hc. It means the thickness of the laminate 25 at a position of Hc / 2 height from the bottom surface of 60.

  When the laminate is composed of an odd number of layers of 5 or more, that is, when the number of layers of the laminate is 2n + 1 (n is an integer of 2 or more), the laminate is directly formed on the high refractive index layer A first layer, a second k layer directly formed on the second k-1 layers (k is an integer of 1 to n), and a second k + 1 layer directly formed on the second k layer; The surface layer is the 2n + 1 layer. The refractive index of the first layer is lower than that of the high refractive index layer, and the refractive index of the 2k + 1 layer is lower than the refractive index of the 2k layer. Thereby, the optical retardation member 10C can have high transmittance in a wide wavelength range. The refractive index of the 2k layer may be higher than the refractive index of the 2k-1 layer, or the refractive index of the 2k layer may be lower than the refractive index of the 2k-1 layer. When the refractive index of the 2k-th layer is higher than the refractive index of the 2k-1th layer, the laminate has a lower refractive index than a layer having a relatively high refractive index with respect to the layer in contact with the layer. It has a structure in which layers and layers are alternately stacked. In this case, the 2k-1 layer and the 2k + 1 layer may be formed of the same material, and the 2k layer may be formed of the same material as the high refractive index layer. Thereby, since the optical retardation member 10C can be manufactured with a small number of types of materials, the manufacturing cost can be reduced.

  An air layer 90c exists in the space (gap) between the high refractive index layers 30 formed on the opposing side surfaces 60s of the adjacent convex portions 60. The periodic arrangement of the high refractive index layer 30 covering the air layer 90c and the convex portion 60 causes birefringence, thereby causing a phase difference. The width Wc of the air layer 90c is preferably in the range of 35 to 100 nm. When the width Wc of the air layer 90c is in the above range, a large phase difference can be secured even at a low asperity height. The “width Wc of the air layer 90c” in the optical retardation member 10C is Hc from the bottom surface of the protrusion 60, where Hc is the height from the bottom surface of the protrusion 60 to the top of the stack 25. This means the thickness of the air layer 90c at the height position (the distance between the surfaces of the high refractive index layer 30 formed on the opposing side surfaces 60s of the adjacent convex portions 60).

  In FIGS. 1A to 1C, the adjacent convex portions 60 of the first uneven structure body 50 are in contact with each other at the bottom surface of the convex portion 60 (or the bottom of the convex portion 60). Alternatively, the skirts of adjacent protrusions 60 may be separated by a predetermined distance. In this case, part of light is reflected at the interface between the recess 70 and the air layer 90 or at the interface between the recess 70 and the high refractive index layer 30 formed thereon, so that the transmittance tends to be low. Therefore, from the viewpoint of making the optical retardation member have high transmittance, the distance between the bottom surfaces of the adjacent convex portions 60 of the first concavo-convex structure 50 (that is, the width of the concave portions 70) It is preferable to be in the range of -0.2 times. In other words, the width of the bottom of the convex portion 60 is preferably in the range of 0.8 to 1 times the pitch of the concavo-convex pattern 80. The ratio of the width of the concave portion 70 to the pitch of the concavo-convex pattern 80 is 0.2 or less, that is, the ratio of the width of the bottom of the convex portion 60 to the pitch of the concavo-convex pattern 80 is 0.8 or more. It becomes easy to make the transmittance of 10 C higher. Similarly, in FIGS. 1A to 1C, adjacent convex portions 62 of the second uneven structure body 52 are in contact with each other at the bottom surface of the convex portion 62 (or the bottom of the convex portion 62). Alternatively, the skirts of adjacent protrusions 62 may be separated by a predetermined distance. From the viewpoint of making the optical retardation members 10A to 10C have high transmittance, the distance between the bottom surfaces of the adjacent convex portions 62 of the second concavo-convex structure 52 (that is, the width of the concave portions 72) It is preferable to be in the range of 0 to 0.2 times.

  In FIGS. 1A to 1C, although the recesses 70 and 72 are formed on the surfaces of the first uneven structure 50 and the second uneven structure 52, respectively, the surface of the base material 40 is exposed in the recesses 70 and 72. May be That is, each of the first concavo-convex structural body 50 and the second concavo-convex structural body 52 may be one continuous layer as shown in FIGS. 1A to 1C, or alternatively, a plurality of independent convex portions may be used. It may be an aggregate.

[Method of Manufacturing Optical Retardation Member]
A method of manufacturing the optical retardation member will be described. The method for manufacturing an optical retardation member mainly comprises, as shown in FIG. 2, a step S1 of forming a first concavo-convex structure on a first surface of a plate-like substrate, and an opposite of the first surface of the substrate It has process S2 which forms a 2nd concavo-convex structure on the 2nd field located in the side, process S3 which forms a high refractive index layer, and process S4 which forms a middle refractive index layer or a layered product. S3 and S4 are optional steps. Each step will be described below.

(1) Formation of first uneven structure S1
The step S1 of forming the first uneven structure body is a solution preparation step of preparing a precursor solution of an inorganic material, applying the prepared precursor solution to a substrate or a mold on which a transfer pattern is formed to form a coating film. A coating step to be formed, a pressing step to press the coating film between the substrate and the transfer pattern, a pre-sintering step to temporarily bake the coating film, a peeling step to peel the mold from the coating film, and curing to cure the coating film It has a process. The pressing step, the pre-baking step, and the peeling step are collectively referred to as a transfer step.

i) Solution Preparation Step First, a solution of a precursor of an inorganic material is prepared. When forming the 1st uneven structure body which consists of inorganic materials using a sol gel method, you may use alkoxide (metallic alkoxide), such as Si, Ti, Sn, Al, Zn, Zr, In, as a precursor of an inorganic material. For example, precursors of inorganic materials described in WO 2016/056277 can be used. As a solvent of a precursor solution, the solvent described in WO2016 / 056277 can be used. To the precursor solution may be added the additives described in WO 2016/056277. In addition, polysilazane described in WO 2016/056277 may be used as a precursor of the inorganic material.

ii) Application Step The precursor solution of the inorganic material prepared as described above is applied on the first surface of the plate-like substrate or on the uneven surface of the mold for transferring the uneven pattern to form a coating film. A surface treatment or an easily adhesive layer may be provided on the substrate to improve adhesion. As a method of applying the precursor solution, any application method such as bar coating method, spin coating method, spray coating method, dip coating method, die coating method, ink jet method can be used, but a substrate with a relatively large area Alternatively, the bar coating method, the die coating method and the spin coating method are preferable in view of the fact that the precursor solution can be uniformly applied to the mold and the application can be completed quickly before the precursor solution is cured.

  The mold for transferring the concavo-convex pattern can be manufactured, for example, by the method described in WO 2016/056277. The mold may have a roll shape (cylindrical shape, cylindrical shape) having a concavo-convex pattern on the outer peripheral surface, or may be a flat shape (sheet shape).

  When the precursor solution is applied on a substrate, the substrate may be kept in the air or under reduced pressure to evaporate the solvent in the coating (drying step). From the viewpoint of stability of pattern formation, it is desirable that the drying time range in which pattern transfer can be made good is wide enough, and this is a mixture of drying temperature (holding temperature), drying pressure, precursor material type, precursor material type It can be adjusted by the ratio, the amount of solvent (precursor concentration) used in preparation of the precursor solution, and the like. In addition, since the solvent in a coating film evaporates only by holding a base material as it is, it is not necessary to necessarily perform positive drying operations, such as heating and ventilation, and the base material which formed the coating film is left as it is only for a predetermined time. Alternatively, it may simply be transported for a predetermined time to perform the subsequent steps.

iii) Pressing Step Subsequently, the coated film is sandwiched between the substrate and the mold for transferring the concavo-convex pattern, and the mold is pressed against the coated film. The coating may be heated while being pressed.

iv) Pre-baking step After pressing the mold against the coating, the coating may be pre-baked. The pre-baking hardens the coating film and makes it difficult to break off at the time of peeling. When performing temporary baking, it is preferable to heat at the temperature of room temperature-300 degreeC in air | atmosphere. Pre-baking is not necessarily required. When a precursor solution is added with a material that generates acid or alkali by irradiating light such as ultraviolet light, the coating film may be cured by irradiating energy beam instead of pre-baking. .

v) Peeling step After the pressing step or the pre-sintering step, the mold is peeled from the coating. Thereby, the first concavo-convex structure on which the surface shape (concave and convex pattern) of the mold is transferred is obtained. A known peeling method can be adopted as a method for peeling the mold. The protrusions and the recesses of the uneven pattern of the mold are arranged extending in a uniform direction, so that the releasability is good. The mold peeling direction may be parallel to the extending direction of the projections and the recesses. Thereby, mold releasability can be further improved. The mold may be peeled while heating the coating film, whereby the gas generated from the coating film can be released and the generation of air bubbles in the coating film can be prevented.

vi) Curing Step After the mold is peeled off from the coating to obtain the first uneven structure, the first uneven structure may be fully cured. The first concavo-convex structure can be fully cured by the main firing. The curing step is not necessarily required. In addition, when the precursor solution is added with a material that generates acid or alkali by irradiating light such as ultraviolet light, the first concavo-convex structure is main-cured by irradiation with energy rays instead of firing. Can.

(2) Formation of second uneven structure S2
Then, a second uneven structure is formed on the second surface (the back surface of the first surface) of the base material. The second concavo-convex structure can be formed in the same manner as the first concavo-convex structure. The formation of the second uneven structure may be performed before the formation of the first uneven structure or simultaneously with the formation of the first uneven structure.

(3) Formation of High Refractive Index Layer Next, a high refractive index layer may be formed on the first uneven structure body. In order to form the high refractive index layer having the film thickness as described above on the upper surface and the side surface of the convex portion of the first concavo-convex structure, the high refractive index layer is formed by a film forming method with high coverage (coverage). It is preferable to form, for example, it can be formed by plating method, atomic layer deposition method, chemical vapor deposition method, sputtering method, vapor deposition method and the like.

(4) Formation of Middle Refractive Layer or Laminate Further, a middle refractive index layer may be formed on the high refractive index layer. The middle refractive index layer is preferably formed by a film forming method with low spitness, such as sputtering or vapor deposition. Thereby, while the middle refractive index layer is not formed on the high refractive index layer on the side surface of the convex portion, or the thickness of the middle refractive index layer formed on the high refractive index layer on the side surface of the convex portion A middle refractive index layer can be formed on the high refractive index layer on the upper surface of the convex portion while controlling within such a range.

  Alternatively, 2n + 1 (n is a positive integer) layers constituting the laminate may be formed in order on the high refractive index layer. Each layer is preferably formed by a film formation method with a low throwing power, for example, a sputtering method, a vapor deposition method, or the like. Thereby, while preventing the material constituting the laminate from being deposited on the high refractive index layer on the side surface of the convex portion, or the film thickness of the laminate formed on the high refractive index layer on the side surface of the convex portion A laminate can be formed on the high refractive index layer on the upper surface of the convex portion while controlling within such a range.

  Although the present invention has been described above by the embodiment, the optical retardation member and the method of manufacturing the same according to the present invention are not limited to the above embodiment, and may be appropriately modified within the scope of the technical idea described in the claims. be able to.

  EXAMPLES Hereinafter, the optical retardation member of the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

Example 1
An uneven structure having a refractive index of 1.43 is formed on each of the front surface (first surface) and the back surface (second surface) of the glass substrate having a refractive index of 1.5. A high refractive index layer is formed by depositing a material having a refractive index of 2.42 with a thickness of 110 nm on the first concavo-convex structure), and the first layer, the second layer, and the third layer are sequentially formed thereon The structure of the optical retardation member in the case of deposition with a thickness of 32 nm, 23 nm, and 109 nm, respectively, was determined by simulation. The material of the first layer and the third layer was a material having a refractive index of 1.46, and the material of the second layer was a material having a refractive index of 2.42. Each concavo-convex structure has a plurality of convex parts and concave parts extending in one direction, the width of the upper surface of each convex part is 15 nm, the width of the lower surface is 160 nm, the height is 308 nm, and the concavo-convex pitch is 180 nm. The transmittance and the phase difference at a wavelength of 450 nm were determined by simulation for this optical retardation member. The transmittance of the optical retardation member at a wavelength of 450 nm was 98.5%, and the retardation was 114 nm.

Example 2
A concavo-convex structure (first concavo-convex structure) having a refractive index of 1.43 is formed on the surface (first surface) of a glass substrate having a refractive index of 1.5, and a refractive index of 1 on the back surface (second surface) Forming a high refractive index layer by depositing a material having a refractive index of 2.42 with a thickness of 55 nm on the first uneven structure body; The structure of the optical retardation member in the case where the first layer, the second layer, and the third layer were sequentially deposited with thicknesses of 32 nm, 27 nm, and 118 nm, respectively, was determined by simulation. The material of the first layer and the third layer was a material having a refractive index of 1.46, and the material of the second layer was a material having a refractive index of 2.42. The concavo-convex pattern (concave-convex structure) of the first and second concavo-convex structures was the same as in Example 1. The transmittance and the phase difference at a wavelength of 450 nm were determined by simulation for this optical retardation member. The transmittance was 98.9%, and the phase difference was 119 nm.

Comparative Example 1
The same concavo-convex structure as in Example 1 is formed only on the first surface of the glass substrate except that the height of the protrusions is 385 nm, and the same refractive index as in Example 1 on the concavo-convex structure on the first surface. Of the first layer, the second layer, and the third layer of the refractive index of Example 1 are sequentially deposited to a thickness of 32 nm, 40 nm, and 100 nm, respectively. An antireflection layer is formed by sequentially laminating films each having a refractive index of 2.33, 1.46, 2.33, 1.46 and a thickness of 13 nm, 34 nm, 115 nm, 88 nm on the second surface of the substrate. The transmittance and the phase difference at a wavelength of 450 nm were determined by simulation for the optical retardation member having the above. The transmittance was 98.3%, and the phase difference was 114 nm.

  From the above simulation results, it was found that the optical retardation members of Examples 1 and 2 have the same transmittance and retardation characteristics as the optical retardation member of Comparative Example 1. This indicates the following. First, by forming the concavo-convex structure on both sides of the glass substrate as in Examples 1 and 2, a convex portion lower than the case where the concavo-convex structure is formed only on one side of the glass substrate as in Comparative Example 1 Comparable retardation characteristics can be achieved at height. Second, by forming the concavo-convex structure on both surfaces of the glass substrate as in Examples 1 and 2, it is possible to achieve the same high transmittance as in the case of forming the antireflective layer as in Comparative Example 1.

Example 3
A glass substrate having a refractive index of 1.5 (OA-10G manufactured by Nippon Electric Glass Co., Ltd.) was prepared. The precursor solution of silica was apply | coated to the surface (1st surface) of this glass substrate, and the coating film was formed. Next, the coating was cured while pressing the mold for imprinting onto the coating, and then the mold was peeled off. Thereby, a first uneven structure body made of silica was formed on the first surface of the glass substrate. Similarly, a second uneven structure was formed on the back surface (second surface) of the glass substrate. The refractive index of silica formed from a precursor solution of silica was 1.43. In addition, the first uneven structure body and the second uneven structure body have a plurality of projections and depressions extending in one direction, the upper surface of each convex portion is 15 nm, the lower surface is 160 nm, and the height is 380 nm The unevenness pitch was 180 nm.

  On the first uneven structure body, a titanium oxide film was formed by sputtering as a high refractive index layer. Sputtering was performed until the thickness of the high refractive index layer formed on the upper surface of the convex portion of the first concavo-convex structure was 145 nm. Here, the thickness of the high refractive index layer formed on the upper surface of the convex portion is determined by placing a flat substrate in the vicinity of the sample, performing sputtering film formation, and determining the thickness of the film formed on the flat substrate. The The refractive index of the formed high refractive index layer was 2.42.

  Next, a silicon dioxide layer (first layer), a titanium oxide layer (second layer) and a silicon dioxide layer (third layer) were sequentially formed by sputtering to form a laminate on the high refractive index layer. The thicknesses of the first layer, the second layer, and the third layer formed on the high refractive index layer on the upper surface of the convex portion were 20 nm, 36 nm, and 85 nm, respectively. Here, the thickness of each layer was determined by placing a flat substrate in the vicinity of a sample, performing sputtering film formation, and determining the thickness of a film formed on the flat substrate. The refractive indexes of the first layer, the second layer, and the third layer were 1.46, 2.42, and 1.46, respectively.

  For the refractive index of each layer of silica, high refractive index layer and laminate, a flat film of each material is formed on a crystalline silicon substrate, and each film of each film is formed using spectral ellipsometry (AutoSE manufactured by Horiba-Scientific). It was determined by measuring the refractive index.

  The optical retardation member thus obtained is placed in a high temperature, high humidity environment at a temperature of 60 ° C. and a humidity of 90%, and the transmittance and phase difference at wavelengths of 400 nm to 800 nm after 0 hour, 24 hours, 120 hours and 240 hours are polarimeters. It measured using (Axometrix Axoscan). In the whole wavelength range measured, the rate of change of the transmittance and the phase difference was less than ± 2.5% and hardly deteriorated. This indicates that the optical retardation member of Example 3 has high moisture resistance.

10, 10A, 10B, 10C: optical retardation member, 20: middle refractive index layer 22: first layer, 24: second layer, 25: laminate, 26: third layer 30: high refractive index layer, 40: 40 Base material, 50: first uneven structure body,
52: second uneven structure, 60, 62: convex portion, 70, 72: concave portion 90: air layer, 80, 82: uneven pattern

Claims (13)

A substrate having a first surface and a second surface located opposite the first surface;
A first uneven structure formed on the first surface and made of a first inorganic material;
And a second uneven structure formed on the second surface and made of a second inorganic material,
The first concavo-convex structure includes a plurality of protrusions extending in a first direction parallel to the first surface and having a width decreasing in a direction away from the first surface of the base.
An optical retardation member comprising a plurality of convex portions, wherein the second concavo-convex structure extends in the first direction and the width decreases in a direction away from the second surface of the base.   The optical retardation member according to claim 1, wherein the aspect ratio of each convex portion of the first concavo-convex structure body and the second concavo-convex structure body is in a range of 1 to 5.   The optical retardation member according to claim 1, wherein the first inorganic material and the second inorganic material are a cured product of a sol-gel material. Assuming that the refractive index of the substrate is n ₀ , the refractive index of the material forming the first concavo-convex structure is n ₁ , and the refractive index of the material forming the second concavo-convex structure is n ₂ , n ₁ -n value and the value of _n 2 -n ₀ of _0, the optical phase difference members according to any one of claims 1 to 3 in the range of -0.4～0.4. A high refractive index layer formed on upper surfaces and side surfaces of the convex portions of the first concavo-convex structure body and having a refractive index higher than that of the convex portions of the first concavo-convex structure body;
A middle refractive index layer formed on the high refractive index layer on the upper surface of the convex portion of the first concavo-convex structure, and configured of a layer having a refractive index lower than that of the high refractive index layer;
The optical retardation according to any one of claims 1 to 4, wherein an air layer is present between the high refractive index layers formed on the opposite side surfaces of adjacent convex portions of the first uneven structure body. Element.   The optical retardation member according to claim 5, wherein the medium refractive index layer is formed on the high refractive index layer on the upper surface and the side surface of the convex portion of the first concavo-convex structure. A high refractive index layer formed on upper surfaces and side surfaces of the convex portions of the first concavo-convex structure body and having a refractive index higher than that of the convex portions of the first concavo-convex structure body;
A laminate formed of a laminate of 2n + 1 (n is a positive integer) layers formed on the high refractive index layer on the upper surface of the convex portion of the first concavo-convex structure body,
An air layer is present between the high refractive index layers formed on the opposite side surfaces of the adjacent convex portions of the first uneven structure body,
The laminate includes a first layer formed on the high refractive index layer, a second k layer formed on a second k-1 layer (k is an integer of 1 to n), and the second k layer. With the 2k + 1 layer formed,
The refractive index of the first layer is lower than the refractive index of the high refractive index layer,
The optical retardation member according to any one of claims 1 to 4, wherein the refractive index of the 2k + 1 layer is lower than the refractive index of the 2k layer.   The optical retardation member according to claim 7, wherein a refractive index of the 2k-1 layer (k is an integer of 1 to n) is lower than a refractive index of the 2k layer.   The optical retardation member according to claim 7, wherein the laminated body is formed on the high refractive index layer on the upper surface and the side surface of the convex portion of the first uneven structure body.   The optical retardation member according to any one of claims 1 to 4, wherein the surfaces of the first concavo-convex structure and the second concavo-convex structure are all exposed.   The projector provided with the optical phase difference member as described in any one of Claims 1-10. The method of manufacturing an optical retardation member according to any one of claims 1 to 10, wherein
Forming a first uneven structure composed of a first inorganic material on the first surface of the substrate;
A method of manufacturing an optical retardation member, comprising: forming a second uneven structure composed of a second inorganic material on a second surface opposite to the first surface of the base.   The method for manufacturing an optical retardation member according to claim 12, wherein the first uneven structure body and the second uneven structure body are formed using a sol-gel method.

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