Optical sheet

Abstract

To provide an optical sheet that offers good abrasion resistance and optical properties. [Solution] The optical sheet 100 comprises a base layer 11 made of a first resin material and an anti-reflective layer 12 made of a second resin material which is the outermost surface of at least one of the surfaces. The anti-reflective layer 12 has a plurality of pillars 20 that protrude outward, and a plurality of pillar bundles 21, which are bundles of multiple pillars 20, are scattered throughout one region of the anti-reflective layer 12.

Description

[Technical Field]

[0001] This invention relates to an optical sheet. [Background technology]

[0002] Conventionally, it is known that various properties can be imparted to optical sheets by applying fine surface processing. For example, Patent Document 1 (International Publication No. 2020 / 183914) discloses a sheet-like substrate having a surface microstructure in which, in order to obtain surface anti-reflective properties, a plurality of first protrusions separated from each other by first crevasses, and a plurality of second protrusions separated from each other by second crevasses that are shallower in depth than the first crevasses and have a shorter continuous length in the in-plane direction, the plurality of second protrusions are observed as finer granular in a plan view compared to the plurality of first protrusions. In detail, an optical substrate such as glass or sapphire glass is etched by reactive ion etching, reactive ion beam etching, etc., to form a fine uneven structure. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 183914 [Overview of the project] [Problems that the invention aims to solve]

[0004] The technology described in Patent Document 1 uses an inorganic material such as glass or sapphire glass as an optical sheet substrate. In response to this, the inventors of this invention focused on using organic materials as a base material. However, without any modifications, organic materials generally tend to have inferior abrasion resistance compared to inorganic materials. Therefore, the object of the present invention is to obtain an optical sheet having an anti-reflective function that can obtain good abrasion resistance even when using organic materials. [Means for solving the problem]

[0005] The inventors of the present invention conducted intensive research on surface microstructures that can provide anti-reflective properties and discovered that such surface microstructures consist of bundles of pillars, and that scattering these pillar bundles is effective in solving the problem, thus completing the present invention.

[0006] [1] A base layer made of a first resin material, It consists of a second resin material, and an anti-reflective layer which is the outermost surface of at least one of the surfaces, An optical sheet comprising a laminate including, The anti-reflective layer has a plurality of pillars that protrude outward, An optical sheet in which multiple pillar bundles, each consisting of multiple pillars arranged in a bundle, are scattered throughout one region of the anti-reflective layer. [2] In the optical sheet described in [1], An optical sheet in which, when the pillar area is determined according to the following procedure A, the ratio of the pillar area when the pillar height is 20 to the pillar area when the pillar height is 0 is 65% or more. (Procedure A) The image of the optical sheet as viewed from the pillar side is processed by image analysis software to calculate the brightness, with the maximum brightness value set to the maximum pillar height of 100 and the minimum brightness value set to the minimum pillar height of 0. A threshold is set for brightness corresponding to an arbitrary pillar height, and the area of ​​the region where the brightness is higher than that threshold is defined as the pillar area. [3] In the optical sheet described in [1] or [2], An optical sheet in which, when the pillar area is determined according to the following procedure A, the ratio of the pillar area when the pillar height is 40 to the pillar area when the pillar height is 0 is 40% or more. (Procedure A) The image of the optical sheet as viewed from the pillar side is processed by image analysis software to calculate the brightness, with the maximum brightness value set to the maximum pillar height of 100 and the minimum brightness value set to the minimum pillar height of 0. A threshold is set for brightness corresponding to an arbitrary pillar height, and the area of ​​the region where the brightness is higher than that threshold is defined as the pillar area. [4] In the optical sheet described in any one of [1] to [3], An optical sheet in which, in the pillar bundle, more than half of the pillars have their tops inclined toward the center of the pillar bundle. [5] In any one of the optical sheets described in [1] through [4], An optical sheet in which the average height of the aforementioned multiple pillars is between 150 nm and 400 nm. [6] In any one of the optical sheets described in [1] to [5], An optical sheet in which, when the anti-reflective layer of a plurality of pillars belonging to the same pillar bundle is observed in an SEM image viewed from directly above, the shortest distance between the vertices of the plurality of pillars is 15 nm or more and 120 nm or less. [7] In any one of the optical sheets described in [1] to [6], An optical sheet wherein the contact angle of pure water on the surface of the optical sheet facing the anti-reflective layer is 140° or more and less than 155°. [8] In any one of the optical sheets described in [1] through [7], The second resin material is an optical sheet comprising a polymerizable component, a polymerization initiator, and an ultraviolet absorber. In the optical sheet described in [9] [8], An optical sheet wherein the polymerization initiator has a maximum peak of light absorption in the wavelength range of over 350 nm and up to 400 nm, and the ultraviolet absorber has a maximum peak of light absorption in the wavelength range of 300 nm to 350 nm.

[10] [1] to [9] In any one of the optical sheets described above, The first resin material is an optical sheet having light transmittance.

[11] [1] to

[10] In any one of the optical sheets described above, The first resin material is an optical sheet containing a thermoplastic resin.

[12] In any one of the optical sheets described in [1] to

[11] , The optical sheet, wherein the first resin material contains polycarbonate. [Effects of the Invention]

[0007] According to the present invention, an optical sheet that can achieve favorable abrasion resistance and optical properties can be provided. [Brief Description of the Drawings]

[0008] [Figure 1] It is a cross-sectional view schematically showing a cross-section of the optical sheet of the present embodiment. [Figure 2] It is a schematic diagram for explaining a method for manufacturing the optical sheet of the present embodiment. [Figure 3] It is a schematic diagram for explaining a method for manufacturing the optical sheet of the present embodiment. [Figure 4] It is an SEM image of the optical sheet of an example when viewed obliquely. [Figure 5] It is an SEM image of the optical sheet of an example when viewed from the top surface. [Mode for Carrying Out the Invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. To avoid complexity, when there are a plurality of identical constituent elements in the same drawing, reference signs are only given to one of them, and may not be given to all of them. All drawings are provided for illustrative purposes only. The shapes, dimensional ratios and the like of each member in the drawings do not necessarily correspond to actual articles.

[0010] In the present specification, unless otherwise specified, the notation "a to b" in the description of numerical ranges means from a to b inclusive. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less". Further, the lower limit values and upper limit values of numerical ranges can be arbitrarily combined with the lower limit values and upper limit values of other numerical ranges, respectively.

[0011] Unless otherwise specified, each component and material exemplified herein may be used alone or in combination of two or more.

[0012] <Optical Sheet> Figure 1 is a schematic cross-sectional view showing a cross-section of the optical sheet of this embodiment.

[0013] As shown in Figure 1, the optical sheet 100 of this embodiment comprises a laminate including a base layer 11 made of a first resin material and an anti-reflective layer 12 made of a second resin material which is the outermost surface of at least one of the surfaces. The anti-reflective layer 12 has a plurality of pillars 20 that protrude outward, and a plurality of pillar bundles 21, in which the plurality of pillars 20 are bundled together, are scattered throughout one region of the anti-reflective layer 12.

[0014] This reduces wear on the optical sheet 100. Specifically, it reduces wear on the pillars 20 and pillar bundles 21 of the anti-reflective layer 12 that make up the outermost surface of the pillars 20. Although the details of this effect are not clear, it is presumed that the presence of multiple pillar bundles 21, which are bundles of multiple pillars 20, uniformly distributes stress caused by wear, thereby improving wear resistance.

[0015] (contact angle) The contact angle of pure water on the side of the optical sheet 100 facing the anti-reflective layer 12 is preferably 140° or more and less than 155°, and more preferably 145° or more and 155° or less. By setting the contact angle to be above the lower limit mentioned above, the water droplet's ability to slide off is improved. On the other hand, by keeping the contact angle below the above upper limit, the adhesion of the coating film can be ensured.

[0016] The contact angle can be determined using a contact angle meter (Azumi Giken Co., Ltd., B100W) by the θ / 2 method, by dropping 2 μL of pure water onto the surface to be measured and measuring the water contact angle after 1 second. Furthermore, the contact angle value can be controlled by adjusting the shape, number, etc., of the pillars 20.

[0017] (Thickness) The thickness of the optical sheet 100 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. By making the thickness of the optical sheet 100 equal to or greater than the above lower limit, the sheet itself can be given rigidity and excellent workability. The thickness of the optical sheet 100 is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less. By making the thickness of the optical sheet 100 below the above upper limit, it can be obtained as a roll, which is excellent for mass production.

[0018] (Light transmittance) The light transmittance of the optical sheet 100 at a wavelength of 550 nm is preferably 90-95%, more preferably 91-95%, and even more preferably 92-95%. The light transmittance is preferable as long as it is high, from the standpoint of achieving transparency.

[0019] The light transmittance of optical sheet 100 can be measured using a spectrophotometer (JASCO Corporation V-670).

[0020] The anti-reflective layer 12 and the substrate layer 11 that constitute the optical sheet 100 will be described below.

[0021] [Anti-reflection layer 12] The anti-reflective layer 12 is the outermost surface of at least one surface of the optical sheet 100. The anti-reflective layer 12 has multiple pillars 20 that protrude outward, and multiple pillar bundles 21, which are bundles of multiple pillars 20, are scattered throughout one region of the anti-reflective layer 12. The pillars 20 and pillar bundles 21 can provide a fine uneven surface to the outer surface of the optical sheet 100. As a result, the reflection of light incident on the anti-reflective layer 12 is suppressed, exhibiting an anti-reflective function, while also providing good wear resistance.

[0022] A pillar 20 is a fine protrusion that extends outward from the surface of the anti-reflective layer 12 facing the base layer 11. The shape of the pillar 20 is not particularly limited, but for example, it may be cylindrical, substantially conical, or needle-shaped. It may also have a taper towards the apex in part. Adjacent pillars 20 may be integrated and connected in the region excluding the apex (for example, the region from the base to the middle). In other words, adjacent pillars 20 may be connected in a webbed manner. Multiple pillars 20 come together to form a pillar bundle 21.

[0023] A pillar bundle 21 is a collection of multiple pillars 20 arranged in a bundle. The distance between pillars 20 within a single pillar bundle 21 is closer than the distance between multiple pillar bundles 21. The number of pillars 20 included in the pillar bundle 21 is not particularly limited, but for example, it can be 3 to 20.

[0024] In the anti-reflective layer 12, the pillar bundles 21 are scattered. That is, when the anti-reflective layer 12 is viewed from above, the pillar bundles 21 are scattered in an island-like pattern.

[0025] The pillars 20 and pillar bundles 21 can be confirmed by observing the surface of the optical sheet 100 on the side with the anti-reflective layer 12 using an SEM.

[0026] Furthermore, when the pillar area PS of the optical sheet 100 is determined according to the following procedure A, it is preferable that the ratio of the pillar area PS when the pillar height HS is 20 to the pillar area PS when the pillar height HS is 0 is 65% or more, and more preferably 67% or more. This improves the wear resistance of the pillar 20.

[0027] Furthermore, when the pillar area PS of the optical sheet 100 is determined according to the following procedure A, it is preferable that the ratio of the pillar area PS when the pillar height PH is 40 to the pillar area PS when the pillar height PH is 0 is 40% or more. This makes it possible to improve the anti-reflective function while maintaining good wear resistance.

[0028] (Procedure A) The brightness of the optical sheet 100 when viewed from the pillar 20 side is calculated by processing the image with image analysis software, the maximum value of the brightness is set to the maximum value of the pillar height HS, 100, and the minimum value of the brightness is set to the minimum value of the pillar height HS, 0. A threshold is set for brightness corresponding to an arbitrary pillar height HS, and the area of ​​the region where the brightness is higher than that threshold is defined as the pillar area.

[0029] In other words, a pillar height HS of 0, determined by procedure A, means that it is the base of pillar 20, and a pillar height HS of 100 means that it is the apex of pillar 20. Therefore, when the pillar height HS is 20, the pillar area PS represents the thickness of the pillar 20 relatively close to its base. Conversely, when the pillar height HS is 40, the pillar area PS represents the thickness of the pillar 20 in the middle section.

[0030] In addition, ImageJ can be used as the image analysis software in procedure A.

[0031] In the pillar bundle 21, it is preferable that more than half of the pillars 20 have their tops inclined toward the center of the pillar bundle 21. Furthermore, the tallest pillar 20 in a single pillar bundle 21 may be at the center of the pillar bundle 21, or it may be offset from the center.

[0032] The tilt of pillar 20 can be confirmed by the SEM image. The inclination of pillar 20 is intended to be obliquely conical relative to a roughly right circular cone.

[0033] The average height of the multiple pillars 20 is preferably 150 nm to 400 nm, more preferably 180 nm to 380 nm, and even more preferably 200 nm to 350 nm.

[0034] The height of the pillar 20 can be calculated by observing the cross-sectional shape of the anti-reflective layer 12 from a 45° angle using SEM, measuring the length from the base to the apex of the pillar 20, and then multiplying that length by √2.

[0035] The average spacing between the vertices of multiple pillars 20 belonging to the same pillar bundle 21 is preferably 15 nm to 120 nm, more preferably 20 nm to 80 nm, and even more preferably 30 nm to 60 nm.

[0036] The spacing between the vertices of the pillars 20 is calculated by measuring the shortest distance between the vertices of multiple pillars 20 observed in an SEM image of the anti-reflective layer 12 viewed from directly above.

[0037] Furthermore, although the anti-reflective layer 12 has pillars 20 and pillar bundles 21 as described above, it may also have smooth regions that do not have pillars 20 and pillar bundles 21. Also, the width of the smooth regions is wider than the spacing between pillar bundles 21.

[0038] (thickness) The average thickness of the anti-reflective layer 12 is preferably 3 μm to 30 μm, and more preferably set to 3 μm to 30 μm. By setting the average thickness of the anti-reflective layer 12 within this range, it is possible to thin the optical sheet 100 while effectively suppressing bending.

[0039] (Second resin material) The anti-reflective layer 12 is made of a second resin material. That is, the pillar 20 and the pillar bundle 21 are made of the second resin material. The second resin material preferably contains a polymerizable component, a polymerization initiator, and an ultraviolet absorber. Furthermore, the second resin material preferably contains a photocurable resin. The following describes the components contained in the second resin material.

[0040] (polymerizable components) Polymerizable components (monomers and oligomers) have polymerizable groups. A network (polymer chain) is formed by the reaction of these polymerizable groups, and the anti-reflective layer 12 can be obtained when the second resin material hardens. Examples of polymerizable groups include radical polymerizable groups and cationic polymerizable groups, but radical polymerizable groups are preferred.

[0041] Examples of radical polymerizable groups include (meth)acryloyl groups and vinyl groups, but (meth)acryloyl groups are preferred. (Meth)acryloyl groups are preferred as radical polymerizable groups because they exhibit excellent radical polymerizability and because compounds containing (meth)acryloyl groups as polymerizable groups are readily available. In other words, so-called acrylic monomers are preferred as monomer components.

[0042] Furthermore, the polymerizable component preferably has multiple (two or more) radical polymerizable groups, and more preferably contains both a component with two radical polymerizable groups and a component with three or more radical polymerizable groups. This allows for the formation of a stronger network in the cured product of the second resin material.

[0043] Furthermore, in polymerizable components, when the region incorporated into the network by linking radical polymerizable groups is considered the main chain of the polymerizable component, examples of this main chain include linear or branched chains having urethane bonds, linear or branched chains having ester bonds, linear or branched chains having epoxy bonds, linear or branched chains of glycols, and linear or branched chains having repeating siloxane bonds (-Si-O-Si-). Among these, those with relatively good flexibility, such as linear or branched chains having urethane bonds, linear or branched chains having ester bonds, linear or branched chains having epoxy bonds, and linear or branched chains of glycols, are preferably selected. This ensures that the cured product of the second resin material is reliably soft. Among these, linear or branched chains having urethane bonds are preferred, and linear chains having urethane bonds are more preferred. Specifically, for example, a linear chain having urethane bonds (-OCONH-) with (meth)acryloyl groups as side chains linked to it, i.e., urethane (meth)acrylate, is an example. This urethane acrylate may be either a monomer or an oligomer. This improves the conformability of the film made of the second resin material to the mold, and as a result, pillars 20 and pillar bundles 21 can be formed on the surface of the anti-reflective layer 12 with greater precision.

[0044] Furthermore, in polymerizable components, when regions that are not incorporated into the network due to linkage between radical polymerizable groups are considered as side chains of the polymerizable components, it is preferable that the polymerizable components, in addition to those described above, also contain fluorinated hydrocarbon groups as side chains. That is, it is preferable that the polymerizable components have radical polymerizable groups and fluorinated hydrocarbon groups within their skeleton. As a result, when the polymerizable components (monomers and oligomer components) polymerize and a cured product of the second resin material is formed, the second resin material hardens with a configuration in which fluorinated hydrocarbon groups are exposed on the surface of the cured product. Therefore, the surface of the cured product of the second resin material, i.e., the surface of the anti-reflective layer 12 on which the pillars 20 and pillar bundles 21 are formed, has a configuration in which these fluorinated hydrocarbon groups as side chains are exposed. Thus, excellent water repellency can be imparted to the surface of the anti-reflective layer 12. In addition, the exposure of fluorinated hydrocarbon groups in the anti-reflective layer 12 allows the anti-reflective layer 12 to exhibit excellent sliding properties.

[0045] Furthermore, the content of polymerizable components in the second resin material is not particularly limited, but is preferably 40.0 parts by weight or more and 95.0 parts by weight or less, and more preferably 70.0 parts by weight or more and 95.0 parts by weight or less, per 100.0 parts by weight of the second resin material. By setting the content of polymerizable components in the second resin material within the aforementioned range, the anti-reflective layer 12 can be provided such that pillars 20 and pillar bundles 21 are formed on its surface with excellent precision.

[0046] Furthermore, if the polymerizable component contains a polymerizable component having a fluorinated hydrocarbon group as a side chain, the content of the polymerizable component is preferably 0.1 parts by weight or more and 5.0 parts by weight or less, and more preferably 0.3 parts by weight or more and 2.5 parts by weight or less, per 100.0 parts by weight of the second resin material. This ensures that the effects obtained by the second resin material containing a polymerizable component having a fluorinated hydrocarbon group as a side chain are reliably exhibited.

[0047] (Polymerization initiator) Furthermore, the second resin material contains a polymerization initiator to initiate a polymerization reaction that forms a network of polymerization components. As mentioned above, when the polymerizable component has a radical polymerizable group as a polymerizable group, it is preferable to include a radical polymerization initiator (photoradical polymerization initiator) that generates radicals when irradiated with ultraviolet light as an energy ray, as the polymerization initiator.

[0048] This allows for the reliable generation of radicals from the photoradical polymerization initiator by irradiating the film made of the second resin material with ultraviolet light while pressing a mold against its surface. Consequently, these radicals can initiate a polymerization reaction by polymerizable components that have radical polymerizable groups as polymerizable groups. Therefore, an anti-reflective layer 12 with pillars 20 and pillar bundles 21 can be stably formed.

[0049] Furthermore, while there are no particular limitations on the photoradical polymerization initiator, examples include acetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, thioxanthone-based photoradical polymerization initiators, ketone-based photoradical polymerization initiators, imidazole-based photoradical polymerization initiators, carbazole-based photoradical polymerization initiators, oxime ester-based photoradical polymerization initiators, titanocene-based photoradical polymerization initiators, acylphosphine oxide-based photoradical polymerization initiators, trichloromethyltriazine-based photoradical polymerization initiators, and one or more of these can be used in combination.

[0050] Furthermore, it is preferable that this photoradical polymerization initiator has a photoabsorption peak in its photoabsorption spectrum that has a maximum absorption peak in the wavelength range of over 350 nm and up to 400 nm.

[0051] Here, the UV absorber described later is used with the aim of suppressing the alteration and deterioration of the optical sheet 100 due to exposure to sunlight. Generally, it has a light absorption peak in the light absorption spectrum that has a maximum absorption peak in the wavelength range of 300 nm to 350 nm. Therefore, even if UV light in the wavelength range of 300 nm to 350 nm is absorbed by the UV absorber during UV irradiation, the photoradical polymerization initiator has a maximum absorption peak in the wavelength range of over 350 nm and up to 400 nm. As a result, it can reliably generate radicals by absorbing UV light in this range.

[0052] The content of the photoradical polymerization initiator in the second resin material is not particularly limited, but is preferably 1.0 part by weight or more and 8.0 parts by weight or less, and more preferably 3.0 parts by weight or more and 6.5 parts by weight or less, per 100.0 parts by weight of the second resin material. By setting the content of the photoradical polymerization initiator within the above range, radicals can be reliably generated by the absorption of ultraviolet light by the photoradical polymerization initiator.

[0053] (UV absorber) The second resin material contains an ultraviolet absorber, which allows it to absorb ultraviolet light within the anti-reflective layer 12. Therefore, it is possible to suppress the alteration and deterioration of other constituent materials contained in the second resin material.

[0054] While not particularly limited, examples of UV absorbers include triazine-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based types, and one or two of these can be used in combination. Among these, benzotriazole-based UV absorbers are particularly preferred, and among benzotriazole-based UV absorbers, hydroxyphenylbenzotriazole-based UV absorbers are more preferred.

[0055] Furthermore, it is preferable that the ultraviolet absorber has a functional group that is reactive with the polymerization component. Specifically, if the polymerizable component is a monomer component having a radical polymerizable group, it is preferable that the ultraviolet absorber has a radical polymerizable group as a functional group. This allows the ultraviolet absorber to be incorporated into the network formed by the reaction of the polymerization component. Therefore, it is possible to effectively suppress the leakage, or bleed-out, of the ultraviolet absorber from the anti-reflective layer 12 composed of the cured product of the second resin material.

[0056] Furthermore, when the polymerizable group of the polymerization component is a (meth)acryloyl group, an ultraviolet absorber having a (meth)acryloyl group as a functional group that reacts with the polymerization component (radical polymerization component) is preferably used as an ultraviolet absorber having a functional group that reacts with the radical polymerization component because the (meth)acryloyl groups of both the polymerization component and the (meth)acryloyl groups can form a network through radical polymerization. In addition, an ultraviolet absorber having a (meth)acryloyl group as a functional group can be obtained, for example, as a reaction product of a hydroxyphenylbenzotriazole ultraviolet absorber having two or more hydroxyl groups and a (meth)acrylate monomer. In hydroxyphenylbenzotriazole ultraviolet absorbers, one hydroxyl group adjacent to the triazine skeleton is present in order to exhibit the function of an ultraviolet absorber. Therefore, in order to impart reactivity with the (meth)acrylate monomer to a hydroxyphenylbenzotriazole ultraviolet absorber, the hydroxyphenylbenzotriazole ultraviolet absorber (benzotriazole ultraviolet absorber) is required to have one or more hydroxyl groups different from this hydroxyl group.

[0057] Furthermore, the content of the ultraviolet absorber in the second resin material is not particularly limited, but it is preferably 2.0 parts by weight or more and 5.0 parts by weight or less, and more preferably 2.5 parts by weight or more and 4.5 parts by weight or less, per 100.0 parts by weight of the second resin material. If the content of the ultraviolet absorber in the second resin material is below the lower limit, depending on the type of ultraviolet absorber, the effect obtained by adding the ultraviolet absorber to the anti-reflective layer 12 may not be sufficiently obtained. Also, even if the content of the ultraviolet absorber in the second resin material exceeds the upper limit, no further improvement in ultraviolet irradiation resistance will be observed, and there is a risk of reducing the transparency of the anti-reflective layer 12 and the adhesion of the anti-reflective layer 12 to the base layer 11.

[0058] The second resin material may further contain other additives besides those mentioned above.

[0059] Other additives include, for example, light stabilizers, heat absorbers, plasticizers, colorants, sensitizers, surfactants, antioxidants, reduction inhibitors, antistatic agents, and surface modifiers (leveling agents).

[0060] The second resin material having such a configuration may further contain a solvent as another additive, but it is preferable that it is a solvent-free resin composition that substantially does not contain a solvent. This makes it possible to form an anti-reflective layer 12 by curing the second resin material by irradiating it with ultraviolet light through a transparent substrate layer 11 while pressing a mold against the surface of the film made of the second resin material, with better film formation accuracy.

[0061] Furthermore, when the second resin material is a solvent-free resin composition, monomers and oligomer components are preferably selected as polymerizable components, as described above. This allows the second resin material to be prepared with low viscosity, specifically, with a viscosity of preferably 30 cP to 200 cP, and more preferably 50 cP to 120 cP, even when the second resin material is a solvent-free resin composition.

[0062] [Base material layer 11] The base layer 11 is a sheet-like base portion of the optical sheet 100. The base layer 11 is made of a first resin material.

[0063] (First resin material) The first resin material is preferably light-transmitting in order to obtain good light transmittance of the optical sheet 100. The first resin material preferably contains a thermoplastic resin, and more preferably contains a polycarbonate-based resin as the main material.

[0064] Furthermore, "main material" refers to the constituent material that makes up 50% by weight or more of the constituent materials of the layer (base material) containing this material.

[0065] Polycarbonate resins are rich in transparency (light transmission) and mechanical strength such as rigidity, and also have high heat resistance. Therefore, by selecting a polycarbonate resin as the transparent resin, the transparency of the base layer 11, as well as the impact resistance and heat resistance of the base layer 11, can be improved.

[0066] Various types of polycarbonate resins can be used, but aromatic polycarbonate resins are preferred. Aromatic polycarbonate resins have aromatic rings in their main chain, which allows for the creation of a base layer 11 with superior strength.

[0067] Aromatic polycarbonate resins are synthesized, for example, by interfacial polycondensation reactions between bisphenol and phosgene, or by transesterification reactions between bisphenol and diphenyl carbonate.

[0068] Examples of bisphenols include bisphenol A and bisphenol (modified bisphenol) which is the origin of the repeating units of polycarbonate shown in formula (1A) below.

[0069] [ka] (In formula (1A), X is an alkyl group, aromatic group, or cyclic aliphatic group having 1 to 18 carbon atoms; Ra and Rb are each independently an alkyl group having 1 to 12 carbon atoms; m and n are each integers from 0 to 4; and p is the number of repeating units.)

[0070] Specifically, examples of bisphenols that originate from the repeating units of the polycarbonate shown in formula (1A) include 4,4'-(pentane-2,2-diyl)diphenol, 4,4'-(pentane-3,3-diyl)diphenol, 4,4'-(butane-2,2-diyl)diphenol, 1,1'-(cyclohexanediyl)diphenol, 2-cyclohexyl-1,4-bis(4-hydroxyphenyl)benzene, 2,3-biscyclohexyl-1,4-bis(4-hydroxyphenyl)benzene, 1,1'-bis(4-hydroxy-3-methylphenyl)cyclohexane, 2,2'-bis(4-hydroxy-3-methylphenyl)propane, and one or more of these can be used in combination.

[0071] In particular, it is preferable that the polycarbonate resin mainly consists of a bisphenol-type polycarbonate resin having a bisphenol-derived skeleton. By using such a bisphenol-type polycarbonate resin, the base layer 11 exhibits even greater strength.

[0072] Furthermore, the glass transition temperature (Tg) of the polycarbonate resin contained as the main material in the base layer 11 is preferably 100°C to 190°C, and more preferably 105°C to 155°C. This makes it relatively easy to bend the optical sheet 100 into a curved shape. It also improves the durability and reliability of the optical sheet 100.

[0073] Furthermore, the base layer 11 may be colorless, red, blue, yellow, or any other color, as long as it is light-transmitting.

[0074] Furthermore, it is preferable that the base layer 11 also contains an ultraviolet absorber. This improves the weather resistance of the optical sheet 100.

[0075] As the ultraviolet absorber, the same type as the ultraviolet absorber described above for the anti-reflective layer 12 can be used, and one or more of these can be used in combination.

[0076] Furthermore, the first resin material may, if necessary, contain various additives such as antioxidants, fillers, plasticizers, light stabilizers, heat absorbers, and flame retardants, in addition to the polycarbonate resin, ultraviolet absorber, and dye or pigment mentioned above.

[0077] In this case, the content of polycarbonate resin in the first resin material is not particularly limited, but is preferably 75% by weight or more, and more preferably 85% by weight or more. By setting the content of polycarbonate resin within the above range, the optical sheet 100 can be made to exhibit excellent strength.

[0078] (Refractive index) Furthermore, the refractive index of the substrate layer 11 at a wavelength of 589 nm is preferably between 1.3 and 1.8, and more preferably between 1.4 and 1.65. By setting the refractive index of the substrate layer 11 within the above numerical range, good optical properties can be obtained.

[0079] (thickness) The average thickness of the base layer 11 is preferably set to 0.1 mm or more and 1.5 mm or less, more preferably to 0.2 mm or more and 0.8 mm or less. By setting the average thickness of the base layer 11 within this range, it is possible to thin the optical sheet 100 while effectively suppressing bending.

[0080] <Manufacturing method> Next, an example of a manufacturing method for the optical sheet 100 will be explained using Figures 2 and 3. The method for manufacturing the optical sheet 100 comprises the following steps. (Step 1) A step of preparing a first mold 40 having a fine uneven structure, (Step 2) A step of forming an anti-reflective layer 12 on the base layer 11 by pressing the first mold 40 onto the coating film 12p obtained by coating the base layer 11, and curing the second resin material while transferring the shape of the first mold 40, Includes. The following provides a detailed explanation of each step.

[0081] (Process 1) First, prepare the first type 40 (Figure 3(a)). The first mold 40 has a fine uneven structure on at least one of its outer surfaces. By transferring this fine uneven structure to a coating film of the second resin material, an anti-reflective layer 12 having pillars 20 and pillar bundles 21 is obtained.

[0082] As shown in Figure 3(a), the first mold 40 preferably comprises a base layer 41 and a resin layer 42 having a fine uneven structure on the base layer 41. As the base layer 41, a known base material can be used, but for example, the first resin material that constitutes the base layer 11 of the optical sheet 100 may be used. The resin layer 42 can be formed using a known resin material, but for example, the second resin material that constitutes the anti-reflective layer 12 of the optical sheet 100 may be used.

[0083] Furthermore, it is preferable that the resin layer 42 having a fine uneven structure of the first mold 40 is obtained using the second mold 50. An example of a method for manufacturing the first mold 40 will be described below with reference to Figure 2.

[0084] (Process 1-1) First, glassy carbon is laminated onto the base material layer 51 by sputtering or the like to form a glassy carbon layer 52. When performing a glassy carbon layer deposition process using a sputtering method with a DC power supply, a glassy carbon layer with small grain boundaries and high film density can be deposited by setting appropriate conditions for sputtering power, deposition pressure, etc. Specifically, the sputtering power should be 0.5 kW or more and 5 kW or less, preferably 1.0 kW or more and 3.0 kW or less, more preferably 1.0 kW or more and 2.0 kW or less, and the deposition pressure should be 1.0 Pa or less, preferably 8 × 10⁻⁶. -1 Pa or less, more comfortable 5 x 10 -1 It's best to use Pa.

[0085] Glassy carbon, also known as glassy carbon or amorphous carbon, has a homogeneous and dense structure (Figure 2(a)). Glassy carbon possesses the same properties as other carbon materials, such as conductivity, chemical stability, heat resistance, and high purity, but also has the superior characteristic of not having its surface powdered and detached. Furthermore, a general characteristic of glassy carbon is its density of 1.45-1.60 g / cm³. 3 It is lightweight, has high bending strength of 50-200 MPa, and is highly corrosion-resistant to acids such as sulfuric acid and hydrochloric acid. Its electrical conductivity is slightly higher than graphite, with a specific electrical resistance of 4 mΩcm to 20 mΩcm, but its gas permeability is 10 -9 cm 2 / s or more 10 -12 cm 2 It is less than or equal to / s.

[0086] The base layer 51 may, for example, comprise a transferable base material and a transferable underlayer formed on the transferable base material (not shown), and a glassy carbon layer 52 is formed on the transferable underlayer.

[0087] Examples of constituent materials for the above-mentioned transfer-type substrate include resins, rubbers, glass, metals, alloys, ceramics (metal oxides, metal nitrides, metal oxynitrides), silicon wafers (Si wafers), compound semiconductors used in compound semiconductor substrates, silicon carbide (SiC) used in power device substrates, and solar cell materials such as silicon. One or more of these materials can be used in combination.

[0088] Examples of the above-mentioned transfer-type underlayers include metals, alloys, ceramics (metal oxides, metal nitrides, metal oxynitrides), silicon (Si), etc., and one or more of these can be used in combination.

[0089] The transfer-type underlayer preferably has an average thickness of 10 nm to 500 nm, and more preferably 50 nm to 250 nm.

[0090] (Step 1-2) Next, the glassy carbon layer 52 on the substrate 51 is etched with an oxygen ion beam or oxygen plasma. A reaction gas may be used during this process. As the reaction gas, an oxygen-containing gas may be used; oxygen alone may be used, or a gas mixed with oxygen and a CF-based gas such as CF4 may be used. In addition, a noble gas such as argon may be mixed in to change the ion current density and plasma density. Etching creates fine recesses on the surface of the glassy carbon layer 52 (Figure 2(b)). At this time, the shape (size, width, angle, etc.) and pitch of the fine recesses can be controlled by controlling the acceleration voltage, gas flow rate, and processing time. This yields the second type 50.

[0091] The glassy carbon layer 52 is a layer made of glassy carbon and forms the outermost surface of the second mold 50. The glassy carbon layer 52 preferably has an average thickness of 300 nm to 5 μm, and more preferably 500 nm to 3 μm.

[0092] (Step 1-3) Next, as shown in Figure 2(c), the first mold 40 is created using the shape of the second mold 50. That is, the shape of the second mold 50 is transferred to the first mold 40. The transcription method is not particularly limited and any known method can be used. As an example, a resin material is coated onto the base layer 41 constituting the first mold 40, and the surface of the second mold 50 on the glassy carbon layer 52 side is pressed against the coating film 42p made of the resin material to transfer the surface shape of the second mold 50 (Figure 2(c)). At this time, it is preferable to cure the resin material by irradiating it with ultraviolet light while transferring the shape. By doing so, a first mold 40 having a resin layer 42 on the base layer 41 can be obtained (Figure 3(a)).

[0093] (Process 2) Next, the shape of the first mold 40 is transferred to obtain an anti-reflective layer 12 having pillars 20 and pillar bundles 21 on its surface. Specifically, the second resin material is applied to one side of the base layer 11 to obtain a coated film 12p, and the first mold 40 is pressed onto the coated film 12p made of the second resin material to transfer the surface shape of the first mold 40 (Figure 3(b)). Alternatively, the coated film 12p may be obtained by reducing the fluidity of the second resin material by heating it appropriately after application to form a film. Furthermore, it is preferable to cure the second resin material by irradiating it with ultraviolet light while transferring it. This results in an optical sheet 100 in which an anti-reflective layer 12 having pillars 20 and pillar bundles 21 on its surface is laminated on the base layer 11 (Figure 3(c)).

[0094] The coating film made of the second resin material may be cured, for example, by irradiating the coating film with ultraviolet light from the substrate layer 11 side. In this case, it is preferable that the substrate layer 11 is light-transmitting.

[0095] As shown in Figure 3(b), the resin layer 42 of the first mold 40 is pressed against the second resin material. However, even when the second resin material is used as the resin layer 42 of the first mold 40, the surface free energy of the second resin material is low, so no particular problems occur, such as the interface becoming excessively tight and difficult to peel off.

[0096] The optical sheet 100 can be obtained by following the procedure described above. The optical sheet 100 may be further processed depending on the purpose and application.

[0097] [Application] The optical sheet 100 of this embodiment is suitably used as a transparent sheet (transparent substrate) that covers the surface (front side) of a functional optical sheet (functional substrate). Specifically, it can be used to cover the front side of a functional optical sheet (functional substrate) that is provided to cover the lens of eyewear, the window portion of a housing for a head-up display, or a windshield of a vehicle.

[0098] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted. [Examples]

[0099] Next, the present invention will be described in detail with reference to examples, but the content of the present invention is not limited to these examples.

[0100] (1) Preparation of the base layer Using the following raw material 1, a first resin material consisting of 98.0 parts by weight of polycarbonate resin 1 and 2.0 parts by weight of ultraviolet absorber 1 was kneaded, and the resulting mixture was extruded to produce a substrate layer (transparent substrate) with a thickness of 0.0.4 mm. (raw material 1) • Polycarbonate resin 1: Bisphenol A type polycarbonate (manufactured by Mitsubishi Engineering Plastics Co., Ltd., "E2000FN") • UV absorber 1: Hydroxyphenyltriazine-based UV absorber (BASF Japan, "Tinuvin 1577 ED")

[0101] (2) Preparation of the second resin material Using the following raw material 2, the raw materials shown in Table 1 were kneaded to prepare each second resin material. (raw material 2) • Acrylic monomer 1: A glycerin triacrylic monomer (manufactured by Toagosei Co., Ltd., "Aronics M-930") that has a branched glycol chain (aliphatic chain with 3 carbon atoms) as its main chain and three acryloyl groups as polymerizable groups. • Acrylic monomer 2: A difunctional acrylic monomer (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., "A-BPE-4") comprising a straight chain with an ester bond as the main chain and two acryloyl groups as polymerizable groups. • Acrylic monomer 3: A difunctional acrylic monomer (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., "A-HD-N") that has a straight glycol chain (aliphatic chain with 6 carbon atoms) as its main chain and two acryloyl groups as polymerizable groups. • Acrylic monomer 4: A polyfunctional acrylic monomer (manufactured by Shin-Etsu Chemical Co., Ltd., "KY-1211") comprising a branched chain having a repeating siloxane bond (-Si-O-Si-) as the main chain, a fluorinated hydrocarbon group as a side chain, and two or more acryloyl groups as polymerizable groups. • Acrylic oligomer 5:2 functional urethane acrylate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "GX-8644D")

[0102] • Polymerization initiator 1: A photoradical polymerization initiator ("Omnirad 819" manufactured by IGMresins B.V.) that has a maximum absorption peak around 370 nm in its light absorption spectrum.

[0103] • UV absorber 2: Hydroxyphenylbenzotriazole-based UV absorber (manufactured by Otsuka Chemical Co., Ltd., "RUVA-93", containing a (meth)acryloyl group as a radical polymerizable group. Maximum absorption peak: wavelength 330nm)

[0104] [Table 1]

[0105] (3) Production of optical sheet <Example 1> An optical sheet was produced as follows. Furthermore, both the first mold and the optical sheet used the base material layer produced in (1) above, and a coating film was formed on the base material layer using the second resin material produced in (2) above. The second resin material used was as shown in Table 2.

[0106] • Preparation of second mold A second mold having a glassy carbon layer on a base layer made of Cr formed on a glass substrate was prepared. The glassy carbon layer was subjected to oxygen plasma etching and had fine recesses on the surface.

[0107] • Preparation of first mold The first mold was produced by the following procedure using the second mold. The second resin material was coated on the base material layer using a die coater to form a coating film, and the surface of the second mold on the glassy carbon layer side was pressed against the coating film to transfer the surface shape of the second mold. Further, while transferring, ultraviolet light of 405 nm was applied at 1500 mJ / cm 2 under the above conditions to cure the resin material, thereby producing the first mold.

[0108] • Production of optical sheet The second resin material was coated on the base material layer using a die coater, and the surface of the first mold on the resin layer side was pressed against the coating film made of the (unheated) second resin material under non-heating conditions at a pressure of 0.010 MPa to transfer the surface shape of the first mold. Further, while transferring, ultraviolet light of 405 nm was applied at 1500 mJ / cm 2 under the above conditions to cure the second resin material, thereby forming an antireflection layer made of the second resin material, and thus an optical sheet in which the base material layer and the antireflection layer are laminated was produced.

[0109] <Example 2> An optical sheet was prepared in the same manner as in Example 1, except that the second resin material was changed to one shown in Table 2.

[0110] <Example 3> An optical sheet was prepared in the same manner as in Example 1, except that instead of being pressed at a pressure of 0.010 MPa without heating, it was pressed at a pressure of 0.008 MPa without heating.

[0111] <Example 4> An optical sheet was prepared in the same manner as in Example 2, except that instead of being pressed at a pressure of 0.010 MPa without heating, it was pressed at a pressure of 0.008 MPa without heating.

[0112] <Comparative Example 1> The optical sheet was fabricated as follows. • Preparation of the second type A second mold was prepared, comprising a glassy carbon layer on a Cr-based underlayer formed on a glass substrate. The glassy carbon layer had fine depressions on its surface.

[0113] • Fabrication of optical sheets A second resin material was applied to the substrate layer, and the resin layer side of the second mold was pressed against the coating film made of the second resin material to transfer the surface shape of the second mold. While transferring the shape, the second resin material was cured by ultraviolet irradiation to form an anti-reflective layer made of the second resin material, thereby creating an optical sheet in which the substrate layer and the anti-reflective layer were laminated.

[0114] <Comparative Example 2> An optical sheet was prepared in the same manner as in Comparative Example 1, except that the second resin material was changed to one shown in Table 2.

[0115] (3) Measurement and evaluation The obtained optical sheets were subjected to the following measurements and evaluations. Figure 4 shows an example of an SEM image of the optical sheet of the example viewed from an oblique angle, and Figure 5 shows an example of an SEM image of the optical sheet of the example viewed from above.

[0116] (Procedure A) The image of the anti-reflective layer side of each optical sheet was smoothed using image analysis software (ImageJ) and converted to 16 bits to calculate the brightness. The maximum brightness was set to the maximum value of pillar height PH, which is 100, and the minimum brightness was set to the minimum value of pillar height PS, which is 0. A threshold was set for luminance corresponding to an arbitrary pillar height PH, and the area of ​​the region where the luminance is higher than the threshold was defined as the pillar area. Specifically, a luminance threshold was set for pillar heights PH20 and PH40, and the area of ​​the region where the luminance is higher than the threshold was calculated and defined as the pillar area PS.

[0117] (Measurement of average pillar height) The cross-sectional shape of the anti-reflective layer was observed using SEM from a 45° angle, and the length from the base to the apex of multiple pillars (20 arbitrary pillars in the 25,000x magnification region) was measured. The average height of the pillars (nm) was then calculated by multiplying this length by √2. The measurement was performed multiple times, and the range of the average pillar heights (nm) calculated for each measurement is shown in Table 2.

[0118] (Measurement of the distance between the vertices of pillars in the same pillar bundle) For pillar bundles and pillars observed in SEM images of the anti-reflective layer viewed from directly above, the shortest distance (nm) between the vertices of multiple pillars belonging to the same pillar bundle was measured. Multiple measurements were performed, and the range of the shortest distance (nm) calculated for each measurement is shown in Table 2. However, pillar bundles were not observed in the anti-reflective layers of Comparative Examples 1 and 2.

[0119] (contact angle) The water contact angle was determined using a contact angle meter (Azumi Giken Co., Ltd., B100W) by applying 2 μL of pure water to the surface of the object to be measured (the side of the optical sheet with the anti-reflective layer) and measuring the water contact angle after 1 second using the θ / 2 method.

[0120] (Light transmittance) The light transmittance of the optical sheet at a wavelength of 550 nm was measured using a spectrophotometer (JASCO Corporation V-670).

[0121] (Abrasion resistance) A sliding test was conducted on the anti-reflective layer side of the optical sheet (load 1 kg, area 572 mm²). 2 A 1500-cycle test was conducted using a No. 3 abrasion filter, and the reduction rate of the contact angle of pure water after the sliding test compared to the contact angle of pure water before the sliding test was determined to evaluate the abrasion resistance. A lower rate of decrease in the contact angle indicates better wear resistance.

[0122] [Table 2] [Explanation of symbols]

[0123] 11 Base material layer 12 Anti-reflection layer 12p coating film 20 Pillars 21 Pillar bundle 41 Base material layer 42 resin layer 42p Coating film 51 Base material layer 52 Glassy carbon layer 100 optical sheets

Claims

1. A base layer made of a first resin material, It consists of a second resin material, and an anti-reflective layer which is the outermost surface of at least one of the surfaces, An optical sheet comprising a laminate including, The anti-reflective layer has a plurality of pillars that protrude outward, An optical sheet in which multiple pillar bundles, each consisting of multiple pillars arranged in a bundle, are scattered throughout one region of the anti-reflective layer.

2. In the optical sheet according to claim 1, An optical sheet in which, when the pillar area is calculated according to the following procedure A, the ratio of the pillar area when the pillar height is 20 to the pillar area when the pillar height is 0 is 65% or more. (Procedure A) The image of the optical sheet as viewed from the pillar side is processed by image analysis software to calculate the brightness, the maximum value of the brightness is set to the maximum value of the pillar height of 100, and the minimum value of the brightness is set to the minimum value of the pillar height of 0. A threshold is set for brightness corresponding to an arbitrary pillar height, and the area of ​​the region where the brightness is higher than that threshold is defined as the pillar area.

3. In the optical sheet according to claim 1, An optical sheet in which, when the pillar area is calculated according to the following procedure A, the ratio of the pillar area when the pillar height is 40 to the pillar area when the pillar height is 0 is 40% or more. (Procedure A) The image of the optical sheet as viewed from the pillar side is processed by image analysis software to calculate the brightness, the maximum value of the brightness is set to the maximum value of the pillar height of 100, and the minimum value of the brightness is set to the minimum value of the pillar height of 0. A threshold is set for brightness corresponding to an arbitrary pillar height, and the area of ​​the region where the brightness is higher than that threshold is defined as the pillar area.

4. In the optical sheet according to claim 1, An optical sheet in which, in the pillar bundle, more than half of the pillars have their tops inclined toward the center of the pillar bundle.

5. In the optical sheet according to claim 1, An optical sheet in which the average height of the aforementioned multiple pillars is between 150 nm and 400 nm.

6. In the optical sheet according to claim 1, An optical sheet in which, when the anti-reflective layer of a plurality of pillars belonging to the same pillar bundle is observed in an SEM image viewed from directly above, the shortest distance between the vertices of the plurality of pillars is 15 nm or more and 120 nm or less.

7. In the optical sheet according to claim 1, An optical sheet wherein the contact angle of pure water on the surface of the optical sheet facing the anti-reflective layer is 140° or more and less than 155°.

8. In the optical sheet according to any one of claims 1 to 7, The second resin material is an optical sheet comprising a polymerizable component, a polymerization initiator, and an ultraviolet absorber.

9. In the optical sheet according to claim 8, An optical sheet wherein the polymerization initiator has a maximum peak of light absorption in the wavelength range of over 350 nm and up to 400 nm, and the ultraviolet absorber has a maximum peak of light absorption in the wavelength range of 300 nm to 350 nm.

10. In the optical sheet according to any one of claims 1 to 7, The first resin material is an optical sheet having light-transmitting properties.

11. In the optical sheet according to claim 10, The first resin material is an optical sheet containing a thermoplastic resin.

12. In the optical sheet according to claim 10, The first resin material is an optical sheet containing polycarbonate.

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