Patent Application
20240045109
The present invention relates to an optical body, a master, and a method for manufacturing an optical body.
Typically, with display devices such as televisions, and optical elements such as camera lenses, in order to reduce surface reflections and increase transmitted light, a reflection-reducing treatment is performed on the light-incident face. For example, one proposal for such a reflection-reducing treatment is to form, on the light-incident face, an optical body in which a concave-convex structure is formed on the surface thereof. Herein, the concave-convex structure formed on the surface of the optical body is formed by multiple convexities and concavities, in which the array pitch between the convexities and the array pitch between the concavities are less than or equal to the visible light wavelengths.
On the surface of such an optical body, changes in the refractive index with respect to incident light become gradual, and thus sudden changes in the refractive index that cause reflections do not occur. Consequently, by forming such a concave-convex structure on the surface of the light-incident face, reflections of incident light can be restrained over a wide wavelength range.
Patent Literatures 1 to 3 disclose technology related to such an optical body. In the technology disclosed in Patent Literature 1, in order to prevent poor filling of transfer material into a mold, convexity losses of the transfer product due to separation resistance, and pattern collapse of the convexities in the transferred fine concave-convex structure, dense clusters of convexities are arranged randomly on the surface of the optical body.
In the technology disclosed in Patent Literature 2, in order to inhibit the occurrence of diffracted light, the array pattern of concavities and convexities is shifted from a regular polygonal array pattern. In the technology disclosed in Patent Literature 3, in order to control the array pitch of concavities and convexities and the like easily, the concavities and convexities are formed randomly by sputtering. In the technology disclosed in Patent Literature 4, concavities and convexities having a symmetric shape are arrayed in a certain array pattern.
However, with the technologies disclosed in Patent Literatures 1 to 4, the anti-reflection characteristics of the optical body remain inadequate. Note that as a method of raising the anti-reflection characteristics of the optical body, a method of overlapping convexities that form the concave-convex structure with each other is proposed, as disclosed in Patent Literature 4. According to this method, since the density of the concave-convex structure is improved, an improvement in the anti-reflection characteristics of the optical body is anticipated. However, in the case of applying this method to a concave-convex structure of the past, in order to realize the desired anti-reflection characteristics, it is necessary to greatly overlap the convexities. For this reason, there is another problem of degraded transferability of the concave-convex structure of the master.
In other words, the optical body is produced using a master as a transfer mold, in which the concave-convex structure is formed on the surface of the master. The concave-convex structure formed on the surface of the master has the inverse shape of the concave-convex structure formed on the surface of the optical body. With this method, an uncured resin layer is formed on a base material, and the concave-convex structure of the master is transferred to the uncured resin layer. After that, the uncured resin layer is cured. Subsequently, the master is separated from the uncured resin layer which has been cured, or in other words, the cured resin layer. The concave-convex structure of the master is thus transferred to the cured resin layer. By the above steps, the optical body is produced. Herein, in the case of greatly overlapping the convexities with each other, the concavities become extremely fine shapes. In other words, the floor area of the concavities becomes extremely small. Consequently, the convexities formed on the master become extremely fine shapes. For this reason, accurately transferring the concave-convex structure of the master to the uncured resin layer becomes extremely difficult. In other words, the transferability of the concave-convex structure of the master is degraded. Additionally, if the transferability is degraded, the concave-convex structure of the master is not reflected accurately in the optical body, and there is a possibility of degraded anti-reflection characteristics of the optical body.
Accordingly, the present invention has been devised in light of the above problems, and an objective of the present invention is to provide a novel and improved optical body, master, and method for manufacturing an optical body in which the anti-reflection characteristics are improved even further, and fabrication is facilitated.
According to an aspect of the present invention in order to achieve the above object, there is provided an optical body having a concave-convex structure in which structures having convex shapes or concave shapes are arrayed on an average cycle less than or equal to visible light wavelengths. The structures have an asymmetric shape with respect to any one plane direction perpendicular to a thickness direction of the optical body.
Herein, a plan-view shape of the structures may have an asymmetric shape with respect to the one plane direction.
Also, in a case of dividing the plan-view shape of the structure into two regions by a line that bisects a quadrilateral circumscribing the structure along an array direction of the structures, each of the two regions may have a different area.
Also, an area ratio obtained by dividing the area of the smaller of the two regions by the area of the larger region may be 0.97 or less.
Also, the area ratio may be 0.95 or less.
Also, the area ratio may be 0.95 or less, and 0.33 or greater.
Also, a perpendicular cross-sectional shape of the structures may have an asymmetric shape with respect to the one plane direction.
Also, a position of an apex of the perpendicular cross-sectional shape of the structures may be displaced in a track direction of the structures with respect to a center point of the track direction.
Also, a displacement ratio, which is obtained by dividing a displacement of the position of the apex by a dot pitch of the structures, may be 0.03 or greater.
Also, the displacement ratio may be 0.03 or greater, and 0.5 or less.
Also, an array pitch of the structures in the one plane direction may be different from an array pitch of the concave-convex structure in another plane direction.
Also, the structures may have convex shapes.
Also, the structures may have concave shapes.
Also, the structures may include a cured curing resin.
Also, adjacent structures may abut each other.
According to another aspect of the present invention, there is provided a master, on a surface of which is formed an inverse shape of the above concave-convex structure.
Herein, the master may be plate-like, hollow round cylindrical, or round columnar.
According to another aspect of the present invention, there is provided a method for manufacturing an optical body, including: forming the concave-convex structure on a base material by using the above master as a transfer mold.
According to the above aspects, the structures have an asymmetric shape with respect to any one plane direction perpendicular to the thickness direction of the optical body. Consequently, high anti-reflection characteristics are realized, without greatly overlapping the structures with each other. For this reason, the transferability of the concave-convex structure of the master is high, thereby also facilitating fabrication of the optical body.
According to the above aspects as described above, the anti-reflection characteristics are improved even further, and fabrication is facilitated.
Hereinafter, (a) preferred embodiment(s) of the present invention will be described in detail with reference to the appended drawings. In this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted.
Next, the configuration of an optical body 10 will be described on the basis of
The concave-convex structure 12 includes multiple convexities 13 (structures), which are convex in the film-thickness direction of the optical body 10, and multiple concavities 14 (structures), which are concave in the film-thickness direction of the optical body 10. The convexities 13 and the concavities 14 are arranged periodically on the optical body 10. For example, in the example of
In other words, the concave-convex structure 12 may be considered to be a parallel array of tracks (rows) that include multiple convexities 13 and concavities 14. Note that although there is no particular limit on which direction in which the convexities 13 and concavities 14 are lined up is to be defined as the tracks, for example, in the case in which the optical body 10 is an elongated optical body (or an optical body obtained by cutting an elongated optical body), the convexities 13 and concavities 14 lined up in the lengthwise direction of the elongated optical body may be defined as the tracks. In the example of
Obviously, the convexities 13 and the concavities 14 may also be arranged in a different array pattern. For example, the convexities 13 and the concavities 14 may also be arranged in a different regular polygonal lattice (for example, a rectangular lattice). Additionally, the convexities 13 and the concavities 14 may also be arranged in a distorted polygonal lattice. Additionally, the convexities 13 and the concavities 14 may also be arranged randomly.
Also, the convexities 13 have an asymmetric shape with respect to any one plane direction perpendicular to the thickness direction of the optical body 10. In the example of
In the present embodiment, as illustrated in
Additionally, draw a quadrilateral X circumscribing the plan-view shape of a convexity 13. Herein, the quadrilateral X means the smallest quadrilateral among quadrilaterals that enclose the plan-view shape of the convexity 13. Next, bisect the quadrilateral X by a line segment X1 perpendicular to the arrow B. Herein, the line segment X1 is the line segment that bisects the quadrilateral X along the array direction of the convexity 13. Next, define the midpoint A of the line segment X1 as the center point of the convexity 13 (that is, the center point of the convexity 13 in the track direction). The plan-view shape of the convexity 13 is divided by the line segment X1 into two regions X11 and X12. In addition, “the plan-view shape of the convexity 13 is asymmetric with respect to the direction of the arrow B” means that these regions X11 and X12 are asymmetric with respect to the line segment X1, or in other words, the areas of the regions X11 and X12 are different. Consequently, the plan-view shape of the convexity 13 is a shape obtained by distorting a shape that is symmetric with respect to the line segment X1 (for example, a perfect circle) in the direction of the arrow B. The area ratio of the region X11 and the region X12 is not particularly limited, but is preferably 0.97 or less, more preferably 0.95 or less, and more preferably 0.95 or less and 0.33 or greater. In the case in which the area ratio becomes 0.97 or less, the floor area described later can be increased. Also, in the case in which the plan-view shape of the convexity 13 takes a triangular shape (see
The plan-view shapes of the convexities 13 may be separated from each other, contacting each other (that is, adjacent convexities 13 may be abutting each other), or partially overlapping each other. In the example of
Furthermore, in the present embodiment, as illustrated in
Additionally, the apexes 13a of the convexities 13 are arranged on the CC cross-section. Additionally, the apexes 13a are arranged at positions that are shifted (displaced) from a line L1 that passes through the point A and is parallel to the thickness direction of the optical body 10. In other words, the positions of the apexes 13a of the perpendicular cross-sectional shapes of the convexities 13 are displaced in the track direction with respect to the center point A of the convexities 13 in the track direction. Specifically, a line L2 that passes through an apex 13a and is parallel to the thickness direction of the optical body 10 is distanced from the line L1 in the direction of the arrow B by a distance T1 (the displacement of the apex position). Consequently, “the perpendicular cross-sectional shapes of the convexities 13 are asymmetric with respect to the direction of the arrow B” means that the apexes 13a are arranged at positions shifted from the line L1 in the direction of the arrow B. Consequently, the perpendicular cross-sectional shapes of the convexities 13 are shapes obtained by distorting shapes that are symmetric with respect to the line L1 in the direction of the arrow B. Consequently, the convexities 13 may be considered to be inclined in the direction of the arrow B. The length of the distance T1 is not particularly limited, but is preferably equal to or greater than 2% of the radius r of a plan-view shape. Herein, the radius r of a plan-view shape means the distance from the point of intersection between the CC cross-section and the outer peripheral part of a convexity 13, to the center point. Also, the value obtained by dividing the distance L1 (nm) by the dot pitch (nm) of the structures, namely the displacement ratio (%), is preferably 0.03 or greater, more preferably 0.03 or greater and 0.5 or less, and more preferably 0.03 or greater and 0.1 or less. Note that in the case in which the convexities 13 and the concavities 14 are arranged randomly, the displacement ratio becomes the value obtained by dividing the distance L1 by the average cycle of the concave-convex structure 12. Also, in the case in which the distance L1 is different for every structure 12, it is sufficient to compute distances L1 for several structures 12, and take the arithmetic mean value of these as the distance L1.
Note that in the example illustrated in
On the other hand, the concavities 14 are arranged in between the convexities 13. In other words, the concavities 14 are formed by the outer peripheral surfaces of the convexities 13. Consequently, the shapes of the concavities 14 inevitably have features similar to the convexities 13. In other words, the plan-view shapes and the perpendicular cross-sectional shapes of the concavities 14 are asymmetric with respect to the direction of the arrow B. The plan-view shapes and the perpendicular cross-sectional shapes of the concavities 14 are defined similarly to the plan-view shapes and the perpendicular cross-sectional shapes of the convexities 13. Note that the plan-view shapes of the concavities 14 are the shapes of the open faces of the concavities 14, and the centers of gravity in the plan-view shapes of the concavities 14 correspond to the apexes 13a of the convexities 13.
In the present embodiment, since the convexities 13 and the concavities 14 have asymmetric shapes with respect to the direction of the arrow B, as disclosed in Examples described later, high anti-reflection characteristics can be realized without overlapping or greatly overlapping the convexities 13 with each other. For this reason, in the present embodiment, high anti-reflection characteristics can be realized without greatly overlapping the convexities 13 with each other. In other words, in the present embodiment, high anti-reflection characteristics can be obtained without greatly overlapping the convexities 13 with each other like in Patent Literature 4. Furthermore, in the present embodiment, the separability of the master 100 is improved. In other words, in the present embodiment, since the convexities 13 have asymmetric shapes with respect to the direction of the arrow B, by separating the master 100 away from the optical body 10 in the direction of the arrow B, the master 100 can be separated from the optical body 10 easily.
The shapes of the convexities 13 and the concavities 14 are not particularly limited insofar as the conditions described above are satisfied. The shapes of the convexities 13 and the concavities 14 may also be bullet-shaped, conical, columnar, or needle-shaped, for example.
Further, the average cycle (an average cycle of a structure) of the convexities 13 and the concavities 14 is less than or equal to the visible light wavelengths (for example, less than or equal to 830 nm), preferably more than or equal to 100 nm and less than or equal to 350 nm, more preferably more than or equal to 120 nm and less than or equal to 280 nm, and further more preferably more than or equal to 130 nm and less than or equal to 270 nm. Consequently, the concave-convex structure 12 has what is called a moth-eye structure. Herein, if the average cycle is less than 100 nm, there is a possibility that the formation of the concave-convex structure 12 may become difficult, which is not preferable. Also, if the average cycle exceeds 350 nm, there is a possibility that a diffraction phenomenon of visible light may occur, which is not preferable.
Herein, the average cycle of the convexities 13 and the concavities 14 is, for example, the arithmetic mean value of the distances between adjacent convexities 13 and concavities 14. Note that the concave-convex structure 12 is observable by scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (cross-sectional TEM), or the like, for example. The average cycle of the convexities 13 is measured by the following method, for example. Namely, several combinations of adjacent convexities 13 are sampled. Next, the distances between the apexes of the convexities 13 are measured. Next, the arithmetic mean value of the measured values may be taken as the average cycle of the convexities 13. In addition, the average cycle of the concavities 14 is measured by the following method, for example. Namely, several combinations of adjacent concavities 14 are sampled. Next, the distances between the centers of gravity of the concavities 14 are measured. Next, the average cycle of the concavities 14 may be computed by taking the arithmetic mean of the measured values.
Note that in the case in which the convexities 13 and the concavities 14 are arrayed periodically on the optical body 10, the average cycle of the convexities 13 and the concavities 14 (that is, the average pitch) is categorized into a dot pitch L12 and a track pitch L13, for example. The dot pitch L12 is the average cycle between the convexities 13 (or concavities 14) arrayed in the track length direction. The track pitch L13 is the average cycle between the convexities 13 (or the concavities 14) arrayed in the track array direction (the vertical direction in
Also, the height of the convexities 13 (in other words, the depth of the concavities 14) is not particularly limited, and is preferably between 100 nm and 300 nm inclusive, more preferably between 130 nm and 300 nm inclusive, and even more preferably between 150 nm and 230 nm inclusive.
By having the average cycle and the height of the concave-convex structure 12 take values in the above ranges, the anti-reflection characteristics of the optical body 10 can be improved further. Specifically, the lower limit of the spectral reflectance (spectral specular reflectance for wavelengths from 350 nm to 800 nm) of the concave-convex structure 12 may be set approximately from 0.01% to 0.1%. Also, the upper limit may be set to 0.5% or less, preferably 0.4% or less, more preferably 0.3% or less, and even more preferably 0.2% or less. Also, in the case of forming the concave-convex structure 12 by a transfer method as described later, the optical body 10 can be separated from the master 100 easily after the transfer. Note that the height of the convexities 13 may also be different for every convexity 13.
The concave-convex structure 12 is made up of a cured curing resin, for example. The cured curing resin is preferably transparent. The curing resin includes a polymerizable compound and a curing initiator. The polymerizable compound is a resin that is cured by the curing initiator. The polymerizable compound may be a compound such as a polymerizable epoxy compound or a polymerizable acrylic compound, for example. A polymerizable epoxy compound is a monomer, oligomer, or prepolymer having one or multiple epoxy groups in the molecule. Examples of polymerizable epoxy compounds include various bisphenol epoxy resins (such as bisphenol A and F), novolac epoxy resin, various modified epoxy resins such as rubber and urethane, naphthalene epoxy resin, biphenyl epoxy resin, phenol novolac epoxy resin, stilbene epoxy resin, triphenol methane epoxy resin, dicyclopentadiene epoxy resin, triphenyl methane epoxy resin, and prepolymers of the above.
A polymerizable acrylic compound is a monomer, oligomer, or prepolymer having one or multiple acrylic groups in the molecule. Herein, monomers are further classified into monofunctional monomers having one acrylic group in the molecule, bifunctional monomers having two acrylic groups in the molecule, and multifunctional monomers having three or more acrylic groups in the molecule.
Examples of “monofunctional monomers” include carboxylic acids (acrylic acids), hydroxy monomers (2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate), alkyl or alicyclic monomers (isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate), other functional monomers (2-methoxyethyl acrylate, methoxyethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, N,N-dimethylamino ethyl acrylate, N,N-dimethylamino propyl acrylamide, N,N-dimethyl acrylamide, acryloyl morpholine, N-isopropyl acrylamide, N,N-diethyl acrylamide, N-vinyl pyrrolidone, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl-acrylate, 2-(perfluorodecyl)ethyl-acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate), 2,4,6-tribromophenol acrylate, 2,4,6-tribromophenol methacrylate, 2-(2,4,6-tribromophenoxy)ethyl acrylate), and 2-ethylhexyl acrylate.
Examples of “bifunctional monomers” include tri(propylene glycol) di-acrylate, trimethylolpropane-diaryl ether, and urethane acrylate.
Examples of “multifunctional monomers” include trimethylolpropane tri-acrylate, dipentaerythritol penta- and hexa-acrylate, and ditrimethylolpropane tetra-acylate.
Examples other than the polymerizable acrylic compounds listed above include acrylmorpholine, glycerol acrylate, polyether acrylates, N-vinylformamide, N-vinylcaprolactone, ethoxy diethylene glycol acrylate, methoxy triethylene glycol acrylate, polyethylene glycol acrylate, ethoxylated trimethylolpropane tri-acrylate, ethoxylated bisphenol A di-acrylate, aliphatic urethane oligomers, and polyester oligomers. From the perspective of transparency of the optical body 10, the polymerizable compound preferably is a polymerizable acrylic compound.
The curing initiator is a material that cures the curing resin. Examples of the curing initiator include thermal curing initiators and light-curing initiators, for example. The curing initiator may also be one that cures by some kind of energy beam other than heat or light (for example, an electron beam) or the like. In the case in which the curing initiator is a thermal curing initiator, the curing resin is a thermosetting resin, whereas in the case in which the curing initiator is a light-curing initiator, the curing resin is a light-curing resin.
Herein, from the perspective of transparency of the optical body 10, the curing initiator preferably is an ultraviolet-curing initiator. Consequently, the curing resin preferably is an ultraviolet-curing acrylic resin. An ultraviolet-curing initiator is a type of light-curing initiator. Examples of ultraviolet-curing initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenyl propane-1-one.
In addition, the resin that forms the concave-convex structure 12 may be a resin imparted with functionality such as hydrophilicity, water repellency, anti-fogging, and the like.
Additionally, additives may also be added to the concave-convex structure 12 depending on the purpose of the optical body 10. Examples of additives include inorganic fillers, organic fillers, leveling agents, surface conditioners, and antifoaming agents. Note that examples of types of inorganic fillers include metallic oxide particles such as SiO2, TiO2, ZrO2, SnO2, and Al2O3.
The type of the base material 11 is not particularly limited, but in the case of using the optical body 10 as an anti-reflection film, a transparent and tear-resistant film is preferable. Examples of the base material 11 include polyethylene terephthalate (PET) film and triacetyl cellulose (TAC) film. In the case of using the optical body 10 as an anti-reflection film, the base material 11 is preferably made of a highly transparent material. Also, it is sufficient to adjust the thickness of the base material 11 as appropriate according to the usage of the optical body 10, or in other words the handling properties demanded of the optical body 10. The base material 11 may be made of a silicon-based material. Also, the shape of the base material 11 is not limited to a film shape, and base materials of any of various shapes, such as plate-like, curved, and lens-shaped, may also be used. Also, for the material of the base material 11, an inorganic material, such as a glass material or an Al2O3-based material, for example, may be used. The base material 11 and the concave-convex structure 12 may be made of different materials or the same material. In the case in which the base material 11 and the concave-convex structure 12 are made of different materials, an index-matching layer or the like for adjusting the refractive index between the materials may also be formed. The thickness of the base material 11 may be from 50 μm to 125 μm, for example. The base material 11 may be plate-like or have another shape (for example, concave or convex). Also, at least one of the base material 11 and the concave-convex structure 12 may also be colored.
Next, various modifications of the concave-convex structure will be described.
Note that to obtain a concave-convex structure 12 like that of the second modification, it is sufficient to modify the track pitch and the dot pitch appropriately. For example, the track pitch may be set from 100 nm to 180 nm, and the dot pitch may be set from 180 nm to 270 nm.
In the fourth modification, the concave-convex structure 12 has the inverse shape of the concave-convex structure 12 illustrated in
The concave-convex structure 12 is produced using the master 100 illustrated in
The master 100 is provided with a master base material 110, and the master concave-convex structure 120 formed on the circumferential surface of the master base material 110. The master base material 110 is a glass body, for example, and specifically is formed from quartz glass. However, the master base material 110 is not particularly limited insofar as the SiO2 purity is high, and may also be formed from a material such as fused quartz glass or synthetic quartz glass. The master base material 110 may also be a laminate of the above materials on a metal matrix, or a metal matrix. The shape of the master base material 110 is a hollow round cylindrical shape, but may also be a round columnar shape, or some other shape. However, as described above, the master base material 110 preferably has a hollow round cylindrical shape or a round columnar shape. The master concave-convex structure 120 has the inverse shape of the concave-convex structure 12.
Next, a method of manufacturing the master 100 will be described. First, a base material resist layer is formed (deposited) on the master base material 110. At this point, the resist constituting the base material resist layer is not particularly limited, and may be either an organic resist or an inorganic resist. Examples of organic resists include novolac-type resist and chemically-amplified resist. Also, examples of inorganic resists include metallic oxides including one or multiple types of transition metals such as tungsten (W) or molybdenum (Mo). However, in order to conduct thermal reaction lithography, the base material resist layer preferably is formed with a thermo-reactive resist including a metallic oxide.
In the case of using an organic resist, the base material resist layer may be formed on the master base material 110 by using a process such as spin coating, slit coating, dip coating, spray coating, or screen printing. Also, in the case of using an inorganic resist for the base material resist layer, the base material resist layer may be formed by sputtering.
Next, by exposing part of the base material resist layer with an exposure device 200 (see
Next, by dripping a developing solution onto the base material resist layer in which is formed the latent image, the base material resist layer is developed. As a result, a concave-convex structure is formed in the base material resist layer. Subsequently, by etching the master base material 110 and the base material resist layer using the base material resist layer as a mask, the master concave-convex structure 120 is formed on the master base material 110. Note that although the etching method is not particularly limited, dry etching that is vertically anisotropic is preferable. For example, reactive ion etching (RIE) is preferable. By the above steps, the master 100 is produced. Note that anodic porous alumina obtained by the anodic oxidation of aluminum may also be used as the master. Anodic porous alumina is disclosed in WO 2006/059686, for example. Additionally, the master 100 may also be produced by a stepper using a reticle mask with an asymmetric shape.
Herein, although details will be described later, in the present embodiment, the master concave-convex structure 120 is formed by adjusting the irradiation mode of the laser light 200A. With this arrangement, the shape of the master concave-convex structure 120 can be set to the inverse shape of the concave-convex structure 12. In other words, the shape of the master concave-convex structure 120 is an asymmetric shape with respect to any one plane direction of the master 100 (herein, the circumferential direction of the master 100).
Next, the configuration of the exposure device 200 will be described on the basis of
The laser light source 201 is a light source that emits laser light 200A, and is a device such as a solid-state laser or a semiconductor laser, for example. The wavelength of the laser light 200A emitted by the laser light source 201 is not particularly limited, but may be a wavelength in the blue light band from 400 nm to 500 nm, for example. Also, it is sufficient for the spot diameter of the laser light 200A (the diameter of the spot radiated onto the resist layer) to be smaller than the diameter of the open face of a concavity of the master concave-convex structure 120, such as approximately 200 nm, for example. The laser light 200A emitted from the laser light source 201 is controlled by the control mechanism 230.
The laser light 200A emitted from the laser light source 201 advances directly in a collimated beam, reflects off the first mirror 203, and is guided to the deflecting optical system.
The first mirror 203 is made up of a polarizing beam splitter, and has a function of reflecting one polarized component, and transmitting the other polarized component. The polarized component transmitted through the first mirror 203 is sensed by the photodiode 205 and photoelectrically converted. Also, the photodetection signal photoelectrically converted by the photodiode 205 is input into the laser light source 201, and the laser light source 201 conducts phase modulation of the laser light 200A on the basis of the input photodetection signal.
In addition, the deflecting optical system is provided with a condenser lens 207, an electro-optic deflector (EOD) 209, and a collimator lens 211.
In the deflecting optical system, the laser light 200A is condensed onto the electro-optic deflector 209 by the condenser lens 207. The electro-optic deflector 209 is an element capable of controlling the radiation position of the laser light 200A. With the electro-optic deflector 209, the exposure device 200 is also able to vary the radiation position of the laser light 200A guided onto the movable optical table 220 (what is called a Wobble mechanism). After the radiation position is adjusted by the electro-optic deflector 209, the laser light 200A is converted back into a collimated beam by the collimator lens 211. The laser light 200A exiting the deflecting optical system is reflected by the second mirror 213, and guided level with and parallel to the movable optical table 220.
The movable optical table 220 is provided with a beam expander (BEX) 221 and an objective lens 223. The laser light 200A guided to the movable optical table 220 is shaped into a desired beam shape by the beam expander 221, and then radiated via the objective lens 223 onto the base material resist layer formed on the master base material 110. In addition, the movable optical table 220 moves by one feed pitch (track pitch) in the direction of the arrow R (feed pitch direction) every time the master base material 110 undergoes one rotation. The master base material 110 is placed on the turntable 227. The spindle motor 225 causes the turntable 227 to rotate, thereby causing the master base material 110 to rotate. With this arrangement, the laser light 200A is made to scan over the base material resist layer. At this point, a latent image of the base material resist layer is formed along the scanning direction of the laser light 200A. Consequently, the track direction of the concave-convex structure 12 (that is, the direction of the arrow B) corresponds to the scanning direction of the laser light 200A.
In addition, the control mechanism 230 is provided with a formatter 231 and a driver 233, and controls the radiation of the laser light 200A. The formatter 231 generates a modulation signal that controls the radiation of the laser light 200A, and the driver 233 controls the laser light source 201 on the basis of the modulation signal generated by the formatter 231. As a result, the irradiation of the master base material 110 by the laser light 200A is controlled.
The formatter 231 generates a control signal for irradiating the base material resist layer with the laser light 200A, on the basis of an input image depicting an arbitrary pattern to draw on the base material resist layer. Specifically, first, the formatter 231 acquires an input image depicting an arbitrary pattern to draw on the base material resist layer. The input image is an image corresponding to a development of the outer circumferential surface of the base material resist layer, in which the outer circumferential surface of the base material resist layer is cut in the axial direction and expanded in a single plane. Next, the formatter 231 partitions the input image into sub-regions of a certain size (for example, partitions the input image into a lattice), and determines whether or not the draw pattern is included in each of the sub-regions. Subsequently, the formatter 231 generates a control signal to perform control to irradiate with the laser light 200A each sub-region determined to include the draw pattern. The control signal (that is, the exposure signal) preferably is synchronized with the rotation of the spindle motor 225, but does not have to be synchronized. In addition, the control signal and the rotation of the spindle motor 225 may also be resynchronized every time the master base material 110 performs one rotation. Furthermore, the driver 233 controls the output of the laser light source 201 on the basis of the control signal generated by the formatter 231. As a result, the irradiation of the base material resist layer by the laser light 200A is controlled. Note that the exposure device 200 may also perform a known exposure control process, such as focus servo and positional correction of the irradiation spot of the laser light 200A. The focus servo may use the wavelength of the laser light 200A, or use another wavelength for reference.
In addition, the laser light 200A radiated from the laser light source 201 may irradiate the base material resist layer after being split into multiple optical subsystems. In this case, multiple irradiation spots are formed on the base material resist layer. In this case, when the laser light 200A emitted from one optical system reaches the latent image formed by another optical system, exposure may be ended.
In the present embodiment, the master concave-convex structure 120 is formed on the master base material 110 by adjusting the irradiation mode of laser light. One example of the laser irradiation mode is a pulse waveform of laser light. Accordingly, pulse waveforms of laser light will be described.
Also, if the output difference between the output level Ib1 and the output level Ib is decreased, the area ratio between the region X11 and the region X12 becomes larger. Also, the distance T1 between the line L2 and the line L1 (that is, the distance in the direction of the arrow B from the apex 13a of a convexity 13 to the center point A of the convexity 13; see
Note that in the example of
Also, as the output time t2 of the high-output pulse P1 becomes longer, the area ratio between the region X11 and the region X12 becomes larger. Also, the distance T1 between the line L2 and the line L1 becomes larger. The relationship (t3/(t2+t3)) between the output time t2 and the output time t3 is preferably equal to or greater than 40%, and less than or equal to 90%. This is because, in this case, the concave-convex structure 12 can be set to an asymmetric shape with respect to the direction of the arrow B.
Also, as the slope of the output level of the high-output pulse P1 becomes smaller (that is, as the amount of decrease in the output level per unit time becomes larger), the area ratio between the region X11 and the region X12 becomes larger. Also, the distance T1 between the line L2 and the line L1 becomes larger. Note that the slope of the output level of the high-output pulse P1 is preferably less than or equal to 97% of Iw. This is because, in this case, the concave-convex structure 12 can be set to an asymmetric shape with respect to the direction of the arrow B. Also, the slope of the output level of the high-output pulse P1 furthermore is preferably equal to or greater than 50% of Iw. This is because, in this case, the area ratio between the region X11 and the region X12 can be set to a value inside the preferable range described above.
Also, as the difference between the maximum value and the minimum value of the high-output pulse P1 becomes larger, the area ratio between the region X11 and the region X12 becomes larger. Also, the distance T1 between the line L2 and the line L1 becomes larger. Note that the difference between the maximum value and the minimum value of the high-output pulse P1 is preferably less than or equal to 97% of Iw. This is because, in this case, the concave-convex structure 12 can be set to an asymmetric shape with respect to the direction of the arrow B. Also, the difference between the maximum value and the minimum value of the high-output pulse P1 furthermore is preferably equal to or greater than 50% of Iw. This is because, in this case, the area ratio between the region X11 and the region X12 can be set to a value inside the preferable range described above.
Also, the number of steps by which to lower the output level of the high-output pulse P1 is one step in the example of
Note that in the examples of
Note that another irradiation mode of the laser light 200A may be the shape of the laser spot that the laser light 200A forms on the base material resist layer. By setting the shape of the laser spot to an asymmetric shape with respect to a direction different from the scanning direction of the laser light 200A, the shape of the master concave-convex structure 120 can be set to an asymmetric shape with respect to a direction different from the scanning direction of the laser light 200A. In this case, it becomes possible to form the concave-convex structure 12 illustrated in
Also, it is sufficient to adjust the specific output levels of the high-output pulse P1 and the low-output pulse P2 appropriately according to the material of the base material resist layer, the wavelength of the laser light 200A, and the like. In other words, it is sufficient to adjust the output levels of the high-output pulse P1 and the low-output pulse P2 so that the master concave-convex structure 120 according to the present embodiment is formed on the master base material 110.
Also, when using a thermo-reactive resist as the base material resist layer, since the temperature distribution changes depending on power level of the irradiating pulse, asymmetric shapes can be produced. Also, when using a photo-reactive resist as the base material resist layer, since the reaction spot shape of the resist changes depending on the light intensity, asymmetric shapes can be produced.
Next, an example of a method of manufacturing the optical body 10 using the master 100 will be described with reference to
The transfer device 300 is provided with the master 100, a base material supply roll 301, a take-up roll 302, guide rolls 303 and 304, a nip roll 305, a separation roll 306, an applicator device 307, and a light source 309.
The base material supply roll 301 is a roll around which a long-length base material 11 is wound in a roll, while the take-up roll 302 is a roll that takes up the optical body 10. Also, the guide rolls 303 and 304 are rolls that transport the base material 11. The nip roll 305 is a roll that puts the base material 11 laminated with an uncured resin layer 310, or in other words a transfer film 3a, in close contact with the master 100. The separation roll 306 is a roll that separates the base material 11 formed with the concave-convex structure 12, or in other words the optical body 10, from the master 100.
The applicator device 307 is provided with an applicating means such as a coater, and applies an uncured light-curing resin composition to the base material 11, and forms the uncured resin layer 310. The applicator device 307 may be a device such as a gravure coater, a wire bar coater, or a die coater, for example. Also, the light source 309 is a light source that emits light of a wavelength able to cure the light-curing resin composition, and may be a device such as an ultraviolet lamp, for example.
In the transfer device 300, first, the base material 11 is sent continuously from the base material supply roll 301 via the guide roll 303. Note that partway through the delivery, the base material supply roll 301 may also be changed to a base material supply roll 301 of a separate lot. The uncured light-curing resin composition is applied by the applicator device 307 to the delivered base material 11, and the uncured resin layer 310 is laminated onto the base material 11. As a result, the transfer film 3a is prepared. The transfer film 3a is put into close contact with the master 100 by the nip roll 305. The light source 309 irradiates with light the uncured resin layer 310 put in close contact with the master 100, thereby curing the uncured resin layer 310. With this arrangement, the arrangement pattern of the master concave-convex structure 120 formed on the outer circumferential face of the master 100 is transferred to the uncured resin layer 310. In other words, the concave-convex structure 12 having the inverse shape of the master concave-convex structure 120 is formed on the base material 11. Next, the base material 11 in which the concave-convex structure 12 is formed, or in other words the optical body 10, is separated from the master 100 by the separation roll 306. Next, the optical body 10 is taken up by the take-up roll 302 via the guide roll 304. Note that the master 100 may be oriented vertically or oriented horizontally, and a mechanism that corrects the angle and eccentricity of the master 100 during rotation may also be provided separately. For example, an eccentric tilt mechanism may be provided in a chucking mechanism.
In this way, in the transfer device 300, the circumferential shape of the master 100 is transferred to the transfer film 3a while transporting the transfer film 3a roll-to-roll. With this arrangement, the optical body 10 is produced.
Note that in the case of producing the optical body 10 with a thermoplastic resin, the applicator device 307 and the light source 309 become unnecessary. Also, the base material 11 is taken to be a thermoplastic resin film, and a heater device is disposed farther upstream than the master 100. The base material 11 is heated and softened by the heater device, and after that, the base material 11 is pressed against the master 100. With this arrangement, the master concave-convex structure 120 formed on the circumferential surface of the master 100 is transferred to the base material 11. Note that the base material 11 may also be taken to be a film made up of a resin other than a thermoplastic resin, and the base material 11 and a thermoplastic resin film may be laminated. In this case, the laminated film is pressed against the master 100 after being heated by the heater device. Consequently, the transfer device 300 is able to continuously produce a transfer product to which the master concave-convex structure 120 formed on the master 100 has been transferred, or in other words, the optical body 10.
In addition, a transfer film to which the master concave-convex structure 120 of the master 100 has been transferred may be produced, and the transfer film may be used as a transfer mold to produce the optical body 10. Also, the master 100 may be duplicated by electroforming, thermal transfer, or the like, and the duplicate may be used as a transfer mold. Furthermore, the shape of the master 100 is not necessarily limited to a roll shape, and may also be a planar master. Besides a method of irradiating resist with the laser light 200A, various processing methods can be selected, such as semiconductor exposure using a mask, electron beam lithography, machining, or anodic oxidation.
In addition, when separating the optical body 10 from the master 100, separation in the direction of the asymmetry of the convexities 13 (in the example of
In Example 1, the master 100 was produced by the following steps. A plate-like master base material 110 made of thermally oxidized silicon was prepared. Next, by spin-coating a positive resist material on the master base material 110, the base material resist layer was formed on the master base material 110. Herein, a metallic oxide resist including tungsten (W) was used as the resist material.
Next, the exposure device 200 was used to form a latent image of a regular hexagonal lattice in the base material resist layer. Herein, the wavelength of the laser light 200A was 405 nm, and the NA of the objective lens 223 was 0.85. Also, the pulse waveform of the laser light 200A was the one illustrated in
Next, by dripping developer onto the base material resist layer, the latent image was removed. In other words, a development process was performed. Next, dry etching was performed using the base material resist layer as a mask. With this arrangement, the master concave-convex structure 120 was formed on the master base material 110. For the etching gas, CHF3 was used. Next, the master concave-convex structure 120 was coated with a fluorine-based release agent.
Next, the optical body 10 was produced using the master 100 as a transfer mold. Specifically, a polyethylene terephthalate film was prepared as the base material 11, and an uncured resin layer made of acrylic resin acrylate was formed on the base material 11. Next, the master concave-convex structure 120 of the master 100 was transferred to the uncured resin layer. Next, the uncured resin layer was cured by irradiating the uncured resin layer with ultraviolet rays at 1000 mJ/cm2. Next, the optical body 10 was separated from the master 100 in the direction of the arrow B (that is, the track direction). By the above steps, the optical body 10 was produced.
The surface structure of the optical body 10 was confirmed with SEM and TEM. A SEM photograph is illustrated in
Also, the convexities 13 had asymmetric shapes in the direction of the arrow B. Specifically, the area ratio between the region X11 and the region X12 was 0.95. Also, the height of the convexities 13 was 180 nm. Also, although the convexities 13 were adjacent to each other, there was little to no overlap.
Next, the spectral reflection spectrum of the optical body 10 was calculated by simulation. The RCWA method was used as the simulation technique. Also, the area ratio of the asymmetry was 0.95. Also, other parameters used in the simulation were as follows.
The results are illustrated in
Also, the floor ratio was measured using commercial data analysis software (Wolfram Mathematica; the same applies hereinafter). The floor ratio is the ratio of the floor area of all concavities 14 with respect to the total area of the surface of the base material 11 (that is, the surface on which the concave-convex structure 12 is formed). As a result, the floor ratio was the relatively large value of 8.0%.
In this way, in Example 1, high anti-reflection characteristics were obtained, even though the convexities 13 do not overlap each other (that is, the floor ratio is relatively large). The inventors think that such anti-reflection characteristics were obtained because the convexities 13 have asymmetric shapes with respect to the direction of the arrow B.
Other than changing the conditions when producing the optical body 10 as follows, the optical body 10 was produced by performing a process similar to Example 1. Specifically, the pulse waveform of the laser light 200A was the one illustrated in
The surface structure of the optical body 10 was confirmed with SEM and TEM. As a result, the formation of the concave-convex structure 12 on the surface of the optical body 10 was confirmed. Also, almost no gaps in the concave-convex structure 12 were confirmed. Consequently, the transferability of the master 100 was confirmed to be favorable. Also, the dot pitch was 250 nm, and the track pitch was 200 nm.
Also, the convexities 13 had asymmetric shapes in the direction of the arrow B. Specifically, the area ratio between the region X11 and the region X12 was 0.83, and the distance T1 was 20 nm. Also, the height of the convexities 13 was 180 nm. Also, although the convexities 13 were adjacent to each other, there was little to no overlap.
Next, by a method similar to Example 1, the spectral reflection spectrum of the optical body 10 was calculated. The results are illustrated in
Also, when the floor ratio was measured using the commercial data analysis software, the floor ratio was 9.7%, which is a larger value than Example 1.
Consequently, the optical body 10 was confirmed to have high anti-reflection characteristics with respect to a wide wavelength band. Also, high anti-reflection characteristics were obtained, even though the floor ratio was higher than Example 1. The reason for this is thought to be because the area ratio of Example 2 is a value inside the preferable range.
Other than changing the conditions when producing the optical body as follows, the optical body was produced by performing a process similar to Example 1. Specifically, the pulse waveform of the laser light 200A was the one illustrated in
The surface structure of the optical body was confirmed with SEM and TEM. A SEM photograph is illustrated in
Also, the convexities 500 were symmetric with respect to all plane directions. Specifically, the plan-view shapes of the convexities 500 were perfect circles (that is, the area ratio was nearly 1.0), and the distance T1 was nearly zero. Also, the height of the convexities was 180 nm. Also, although the convexities 500 were adjacent to each other, there was little to no overlap.
Next, by a method similar to Example 1, the spectral reflection spectrum of the optical body was calculated. The results are illustrated in
Also, when the floor ratio was measured using the commercial data analysis software, the floor ratio was 10%.
Consequently, the spectral reflectance of the optical body was higher overall than Example 1. Furthermore, the spectral reflectance was particularly high in the wavelength band from 450 nm to 550 nm. This is thought to be because, in Comparative Example 1, since the floor ratio is large, reflections of incident light occur on the floor of the concavities 14. Also, in the actual measurement, the spectral reflectance was higher than the values illustrated in
Other than setting the output level Iw of the high-output pulse P1 to 11.0 MW/cm2, the optical body was produced by performing a process similar to Comparative Example 1.
The surface structure of the optical body was confirmed with SEM and TEM. As a result, the formation of the concave-convex structure on the surface of the optical body was confirmed. However, the convexities greatly overlapped each other, and gaps in the concave-convex structure were observed sporadically. Also, the dot pitch was 250 nm.
Also, the convexities were symmetric with respect to all plane directions. Specifically, the plan-view shapes of the convexities were perfect circles (that is, the area ratio was nearly 1.0), and the distance T1 was nearly zero. Also, the height of the convexities was 180 nm. Next, by a method similar to Example 1, the spectral reflection spectrum of the optical body was calculated. The results are illustrated in
Also, when the floor ratio was measured using the commercial data analysis software, the floor ratio was 5.5%, which is an extremely small value. In Comparative Example 2, the floor ratio was small because the convexities greatly overlap each other. For this reason, in the simulation, the spectral reflectance exhibited favorable values. However, when the concave-convex structure was actually observed, gaps in the concave-convex structure were observed sporadically, and thus the actual spectral reflectance is anticipated to be higher than in
Other than performing the exposure while randomly changing the output time t2 of the high-output pulse P1 between 22 ns and 25 ns, the optical body 10 was produced by performing a process similar to Example 2.
The surface structure of the optical body 10 was confirmed with SEM and TEM. A SEM photograph is illustrated in
Also, the convexities 13 had asymmetric shapes in the direction of the arrow B (the vertical direction in
Next, the spectral reflection spectrum of the optical body 10 was measured. For the measurement, the JASCO V-550 was used. The results are illustrated in
Also, when the floor ratio was measured using the commercial data analysis software, the floor ratio was 10%.
A transfer film was produced, on which the master concave-convex structure 120 of the master 100 produced in Example 1 was transferred. Additionally, other than using the transfer film in place of the master 100, the optical body 10 was produced by performing a process similar to Example 1.
The surface structure of the optical body 10 was confirmed with SEM and TEM. As a result, the formation of the concave-convex structure 12 on the surface of the optical body 10 was confirmed. The CC cross-section of the concave-convex structure 12 had the shape illustrated in
Also, the concavities 14 had asymmetric shapes in the direction of the arrow B. Specifically, the area ratio between the region X11 and the region X12 was 0.9, and the distance T1 was 15 nm. Also, the depth of the concavities 14 was 180 nm. Also, there was little to no overlap between the concavities 14.
Next, by a method similar to Example 1, the spectral reflection spectrum of the optical body 10 was calculated. The results are illustrated in
Also, when the floor ratio in plan view was measured using the commercial data analysis software, the floor ratio was 9.8%. Note that the floor herein refers to the floor of the transfer film used in place of the master, which becomes the top (upper end) of the convexities 13 in the obtained optical body 10.
Other than changing the conditions when producing the optical body 10 as follows, the optical body 10 was produced by performing a process similar to Example 1. Specifically, the master concave-convex structure 120 was coated with an inorganic release agent.
The surface structure of the optical body 10 was confirmed with SEM and TEM. As a result, the formation of the concave-convex structure 12 on the surface of the optical body 10 was confirmed. Also, almost no gaps in the concave-convex structure 12 were confirmed. Consequently, the transferability of the master 100 was confirmed to be favorable. Also, the dot pitch was 250 nm, and the track pitch was 200 nm.
Also, the convexities 13 had asymmetric shapes in the direction of the arrow B. Specifically, the area ratio between the region X11 and the region X12 was 0.97. Also, the height of the convexities 13 was 180 nm, and the distance T1 was 8 nm. Also, although the convexities 13 were adjacent to each other, there was little to no overlap. The change in the area ratio from Example 1 is thought to be because the state of the coating of the release agent changed.
Next, by a method similar to Example 1, the spectral reflection spectrum of the optical body 10 was calculated. The results are illustrated in
Also, when the floor ratio was measured using the commercial data analysis software, the floor ratio was 8.0%, which is the same value in the error range as Example 1. The results are summarized in Table 1. Note that in Table 1, the values of the 550 nm reflectance for Examples 1, 2, 4, and 5 and Comparative Examples 1 and 2 are simulation values, whereas the value of the 550 nm reflectance for Example 3 is a measured value. In addition, Table 1 also illustrates the displacement ratio. Consequently, the optical bodies 10 according to Examples were confirmed to have high anti-reflection characteristics with respect to a wide wavelength band.
The preferred embodiment(s) of the present invention has/have been described above with reference to the accompanying drawings, whilst the present invention is not limited to the above examples. A person skilled in the art may find various alterations and modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-224316 | Nov 2015 | JP | national |
| 2016-211302 | Nov 2016 | JP | national |
This application is a continuation of U.S. patent application Ser. No. 15/769,411 (filed on Apr. 19, 2018), which is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2016/083775 (filed on Nov. 15, 2016) under 35 U.S.C. § 371, which claims priority to Japanese Patent Application Nos. 2015-224316 (filed on Nov. 16, 2015) and 2016-221302 (filed on Nov. 14, 2016), which are all hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15769411 | Apr 2018 | US |
| Child | 18375123 | US |
