Anti-fog sheet structure and helmet

Abstract

To provide an antifogging sheet structure having excellent antifogging properties.SOLUTION: An antifogging sheet structural body 100 includes a substrate 22 formed of polycarbonate, a first synthetic polymer film 24 formed on the first main surface side of the substrate, and a second synthetic polymer film 26 formed on the second main surface side of the substrate, wherein the first synthetic polymer film has a plurality of first convex portions on its surface having an equivalent circle diameter Dp1 in the range of more than 50 nm and less than 500 nm, and the second synthetic polymer film has a plurality of second convex portions on its surface having an equivalent circle diameter Dp2 in the range of more than 20 nm and less than 500 nm, the first synthetic polymer film is formed from a cured product of a photocurable resin containing 30 mass% or more of ethoxylated pentaerythritol tetraacrylate, and when the surface of the first synthetic polymer film is contacted with saturated water vapor at 50°C, the time for the linear visible light transmittance of the first synthetic polymer film to decrease to 80% of the initial value is 90 seconds or more.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an anti-fogging sheet structure and a helmet. [Background technology]

[0002] For example, the face shield of a helmet must have high anti-fogging properties.

[0003] Patent Document 1 discloses an anti-fog film structure for use in helmets. The anti-fog film structure described in Patent Document 1 uses an anti-fog film whose surface is made more hydrophilic by saponifying a triacetate cellulose film.

[0004] Patent Document 2 discloses a resin composition for anti-fog coatings that uses a water-absorbing resin composition, and a plastic laminate that uses the same. The resin composition for anti-fog coatings contains a specific (meth)acrylamide copolymer in which a (meth)acrylamide monomer is copolymerized with other monomers, and at least one type of difunctional or higher (meth)acrylate compound. It describes that when the resin composition for anti-fog coatings is applied to a polycarbonate plate and cured by irradiating it with ultraviolet light, the coated surface has anti-fog properties.

[0005] Furthermore, Patent Document 3 discloses an anti-reflection plate having anti-glare properties, which is used for information display panels placed for advertising purposes in places visible to many people. The anti-reflection plate described in Patent Document 3 has anti-reflection films with a moth-eye structure on both sides of the surface. It is described that by forming the anti-reflection film from a hydrophilic resin, the surface with the moth-eye structure exhibits super-hydrophilicity, and the contact angle with water can be set to 20° or less. It is also described that even if water droplets adhere to the super-hydrophilic surface, they spread thinly and evaporate quickly, thereby exhibiting an anti-fogging effect. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Registered Utility Model Publication No. 3202173 [Patent Document 2] International Publication No. 2012 / 086552 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-109979 Summary of the Invention [Problem to be solved by the invention]

[0007] The anti-fogging properties required for helmet face shields are, for example, that the anti-fogging time (the time it takes for transmittance to fall to 80% of the initial value when exposed to saturated water vapor at 50°C) in an anti-fogging evaluation test in accordance with the ECE R22-5 standard is at least 20 seconds, and preferably 90 seconds or more.

[0008] However, the configurations described in Patent Documents 1 to 3 do not achieve the anti-fogging properties required for helmet face shields. For example, Patent Document 2 merely evaluates breath anti-fogging properties (whether or not fogging occurs when breath is blown onto the surface for 5 seconds) and hot water anti-fogging properties (whether or not fogging occurs 60 seconds after the surface is placed over a beaker containing 40°C hot water with the coated surface facing the hot water). Furthermore, simply using a hydrophilic surface, as in Patent Documents 1 and 3, has limitations on anti-fogging properties in conditions where evaporation is difficult.

[0009] Therefore, an object of the present invention is to provide an anti-fog sheet structure that can satisfy an anti-fog time of 90 seconds or more in an anti-fog evaluation test conforming to the ECE R22-5 standard, and a helmet equipped with such an anti-fog sheet structure. [Means for solving the problem]

[0010] According to an embodiment of the present invention, the following solutions are provided: [Item 1] a substrate formed of transparent plastic; a first synthetic polymer film formed on a first main surface side of the substrate; a second synthetic polymer film formed on a second main surface of the substrate opposite to the first main surface; and the first synthetic polymer film has, on its surface, a plurality of first protrusions each having an equivalent circle diameter Dp1 in the range of more than 50 nm and less than 500 nm when viewed in a normal direction of the first synthetic polymer film; the second synthetic polymer film has, on its surface, a plurality of second protrusions each having an equivalent circle diameter Dp2 in the range of more than 20 nm and less than 500 nm when viewed in a normal direction of the second synthetic polymer film; the first synthetic polymer film is formed from a cured product of a photocurable resin containing 30% by mass or more of ethoxylated pentaerythritol tetraacrylate; the second synthetic polymer film is formed from a cured product of a photocurable resin, An anti-fog sheet structure having anti-fog properties in which, when the surface of the first synthetic polymer film is brought into contact with saturated water vapor at 50°C, the time it takes for the linear transmittance of visible light of the first synthetic polymer film to decrease to 80% of its initial value is 90 seconds or longer. The transparent plastic forming the substrate is preferably polycarbonate. [Item 2] When the height of the plurality of first convex portions is Dh1, Dh1 is 50 nm or more, and an aspect ratio A1=Dh1 / Dp1 is less than 1.0, Item 1. The anti-fog sheet structure according to item 1, wherein when the height of the plurality of second protrusions is Dh2, the aspect ratio A2=Dh2 / Dp2 is 1.0 or more. [Item 3] Item 3. The anti-fog sheet structure according to item 2, wherein the height Dh1 of the plurality of first convex portions satisfies 150 nm≦Dh1≦300 nm. [Item 4] 4. The anti-fog sheet structure according to item 2 or 3, wherein the height Dh2 of the plurality of second convex portions satisfies 150 nm≦Dh2≦200 nm. [Item 5] 5. The anti-fog sheet structure according to any one of items 2 to 4, wherein the aspect ratio A2=Dh2 / Dp2 is 1.5 or less. [Item 6] 6. The anti-fog sheet structure according to any one of items 2 to 5, wherein the height Dh1 of the plurality of first convex portions is equal to or greater than the height Dh2 of the plurality of second convex portions. [Item 7] 7. The anti-fog sheet structure according to any one of items 1 to 6, wherein the surface of the first synthetic polymer film has a contact angle with water of 20° or more. [Item 8] 8. The anti-fog sheet structure according to any one of items 1 to 7, wherein the first synthetic polymer film is formed from a cured product of the photocurable resin that further contains urethane acrylate. [Item 9] Item 9. The anti-fog sheet structure according to Item 8, wherein the urethane acrylate comprises a urethane acrylate obtained by curing a mixture of 70% by mass of the urethane acrylate and 30% by mass of 2-(2-vinyloxyethoxy)ethyl acrylate monomer, the cured product having a water absorption rate of more than 2.0%. [Item 10] a third synthetic polymer film formed between the first main surface of the substrate and the first synthetic polymer film; 10. The anti-fog sheet structure according to any one of items 1 to 9, wherein the third synthetic polymer film has, on its surface, a plurality of third protrusions each having an equivalent circle diameter Dp3 in the range of more than 20 nm and less than 500 nm when viewed in the normal direction of the third synthetic polymer film. [Item 11] 11. The anti-fog sheet structure according to any one of items 1 to 10, wherein the haze value is 1.0 or less. [Item 12] Transmitted light L * a * b * a in color space * The absolute value of and b * 12. The anti-fog sheet structure according to any one of items 1 to 11, wherein the absolute values ​​of are each independently 1.0 or less. [Item 13] A helmet having a shield and a shell, The shield further includes an anti-fogging sheet structure disposed inside the shield via a gap, 13. A helmet, wherein the anti-fog sheet structure is the anti-fog sheet structure according to any one of items 1 to 12, and the first synthetic polymer film is configured to be disposed on the inside when the helmet is worn. [Effects of the Invention]

[0011] According to an embodiment of the present invention, there is provided an anti-fog sheet structure that can satisfy an anti-fog time of 90 seconds or more in an anti-fog evaluation test in accordance with the ECE R22-5 standard, and a helmet equipped with such an anti-fog sheet structure. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic side view of a full-face helmet 100 equipped with an anti-fog sheet structure according to an embodiment of the present invention. [Figure 2] 1 is a schematic perspective view of a shield 10 included in a full-face helmet 100. FIG. [Figure 3] 1 is a schematic perspective view of an antifogging sheet structure 20 attached to a shield 10. FIG. [Figure 4] FIG. 2 is a top view showing the state in which the antifogging sheet structure 20 is attached to the shield 10. [Figure 5] 1 is a schematic horizontal cross-sectional view of an antifogging sheet structure 20 attached to a shield 10. FIG. [Figure 6] FIG. 1 is a schematic cross-sectional view of an antifogging sheet structure 20A according to an embodiment of the present invention. [Figure 7] FIG. 2 is a schematic cross-sectional view of an antifogging sheet structure 20B according to an embodiment of the present invention. [Figure 8] FIG. 2 is a diagram showing an SEM image of the moth-eye structure of the first synthetic polymer film. [Figure 9] FIG. 10 is a diagram showing an SEM image of another moth-eye structure of the first synthetic polymer film. DETAILED DESCRIPTION OF THE INVENTION

[0013] An anti-fog sheet structure and a full-face helmet including the anti-fog sheet structure according to an embodiment of the present invention will be described below with reference to the drawings. Note that the anti-fog sheet structure and helmet according to the embodiment of the present invention are not limited to those exemplified below, and the anti-fog sheet structure according to the embodiment of the present invention can also be attached to helmets other than full-face helmets.

[0014] First, the structure of a full-face helmet 100 equipped with an anti-fog sheet structure 20 will be described with reference to Figures 1 to 5. Figure 1 is a schematic side view of a full-face helmet 100 equipped with an anti-fog sheet structure according to an embodiment of the present invention, and Figure 2 is a schematic perspective view of a shield 10 provided in the full-face helmet 100. Figure 3 is a schematic perspective view of the anti-fog sheet structure 20 attached to the shield 10. Figure 4 is a top view showing the state in which the anti-fog sheet structure 20 is attached to the shield 10, and Figure 5 is a schematic horizontal cross-sectional view of the state in which the anti-fog sheet structure 20 is attached to the shield 10.

[0015] As shown in FIG. 1, the helmet 100 has a shield 10 and a shell 40. The helmet 100 further has an anti-fog sheet structure 20 arranged inside the shield 10 with a gap 30a (see FIG. 5) interposed therebetween. As shown in FIGS. 1 and 2, the shield 10 is attached to the shell 40 by inserting pins provided on the shell 40 into holes 10a and 10b. The anti-fog sheet structure 20 is removably bonded to the inner surface of the shield 10 by fitting notches 22a and 22b onto pins 12a and 12b of the shield 10 (see FIGS. 3 and 4). The seal 30 is formed, for example, from a silicone-based sealant, and has a width of approximately 1 mm to approximately 5 mm and a height of approximately 1 mm to approximately 5 mm. The seal 30 forms a sealed gap (space) 30a between the inner surface of the shield 10 and the outer surface 20SO of the anti-fog sheet structure 20. The gap 30a has the effect of insulating the anti-fogging sheet structure 20 from the shield 10. That is, even if the shield 10 is exposed to cold outside air, a sudden drop in temperature of the anti-fogging sheet structure 20 is suppressed. The shield 10 is formed, for example, from polycarbonate or acrylic resin with a thickness of about 0.5 mm or more and about 10 mm or less.

[0016] The helmet 100 further includes an impact absorbing liner, an interior structure, a chin strap, etc. (not shown), but these are omitted here for simplicity. The configuration of the helmet 100 other than the anti-fog sheet structure 20 may be the same as that of a known full-face helmet.

[0017] Next, with reference to FIGS. 6 and 7, an example of an anti-fog sheet structure according to an embodiment of the present invention will be described.

[0018] FIG. 6 shows a schematic cross-sectional view of an anti-fog sheet structure 20A according to an embodiment of the present invention. The anti-fog sheet structure 20A includes a substrate 22A made of polycarbonate, a first synthetic polymer film 24A formed on a first main surface 22AS1 of the substrate 22A, and a second synthetic polymer film 26A formed on a second main surface 22AS2 of the substrate 22A opposite the first main surface 22AS1. The anti-fog sheet structure 20A is configured so that the first synthetic polymer film 24A is positioned on the inside when the helmet is worn. Specifically, a seal 30 is affixed to the second synthetic polymer film 26A formed on the opposite side of the substrate 22A from the first synthetic polymer film 24A. The anti-fog sheet structure 20A is removably adhered to the inner surface of the shield 10 by the seal 30 so that the second synthetic polymer film 26A faces the inner surface of the shield 10. The same applies to the anti-fog sheet structure 20B described below. The thickness of substrate 22A is, for example, about 0.3 mm or more and about 1.0 mm or less. The material of substrate 22A is preferably polycarbonate, as exemplified above, from the viewpoint of adhesion to first synthetic polymer film 24A and / or second synthetic polymer film 26A, but is not limited thereto. Transparent plastics (with a visible light transmittance of 90% or more), such as acrylic resin or PET, may also be used. If necessary, the surface of substrate 22A may be treated with a primer.

[0019] The first synthetic polymer film 24A has a plurality of first protrusions 24Ap on its surface, and the second synthetic polymer film 26A has a plurality of second protrusions 26Ap on its surface. The plurality of first protrusions 24Ap and the plurality of second protrusions 26Ap each form a moth-eye structure.

[0020] The moth-eye structure utilizes the principle of the moth eye, and has a fine uneven structure controlled to be equal to or smaller than the wavelength of visible light (λ = 380nm to 780nm), preventing reflection by continuously changing the refractive index of incident light from that of the incident medium to that of the substrate along the depth direction of the unevenness. The moth-eye structure is characterized by its ability to exert anti-reflection effects with little dependence on the angle of incidence over a wide wavelength range.

[0021] The present applicant has developed a method for producing an antireflective coating (antireflective surface) having a moth-eye structure using an anodized porous alumina layer. By using an anodized porous alumina layer, molds having an inverted moth-eye structure can be produced with high mass productivity (JP 2009-166502 A, WO 2011 / 125486 A, WO 2013 / 183576 A). The disclosures of JP 2009-166502 A, WO 2011 / 125486 A, and WO 2013 / 183576 A are incorporated herein by reference in their entirety.

[0022] In a state where a UV-curable resin is applied between a mold (moth-eye forming mold) having an inverted moth-eye structure formed by the above-mentioned anodized porous alumina layer and a substrate, the UV-curable resin is irradiated with ultraviolet light to harden the UV-curable resin, and the inverted moth-eye structure is transferred to the surface of the UV-cured resin, forming a moth-eye structure. In other words, a synthetic polymer film formed of a UV-curable resin having a moth-eye structure on its surface is obtained.

[0023] When viewed from the normal direction of the first synthetic polymer film 24A, the equivalent area circle diameter Dp1 of the multiple first protrusions 24Ap is in the range of more than 50 nm and less than 500 nm. For example, if the first protrusions 24Ap are conical, the equivalent area circle diameter Dp1 of the first protrusions 24Ap corresponds to the diameter of the base of the cone. Furthermore, the typical distance Dint1 between adjacent first protrusions 24Ap is more than 50 nm and not more than 1000 nm. As illustrated in FIG. 6, if the first protrusions 24Ap are densely arranged and there are no gaps between adjacent first protrusions 24Ap (for example, the bases of the cones partially overlap), the equivalent area circle diameter Dp1 of the protrusions 24Ap is equal to the distance D1int between adjacent first protrusions 24Ap. The typical height Dh1 of the first protrusions 24Ap is 50 nm or more and less than 500 nm. The thickness t of the first synthetic polymer film 24A S1 There is no particular limitation on the height Dh1 of the first protrusion 24Ap.

[0024] When viewed from the normal direction of the second synthetic polymer film 26A, the equivalent area circle diameter Dp2 of the multiple second protrusions 26Ap is in the range of more than 20 nm and less than 500 nm. For example, if the second protrusions 26Ap are conical, the equivalent area circle diameter Dp2 of the second protrusions 26Ap corresponds to the diameter of the base of the cone. Furthermore, the typical distance Dint2 between adjacent second protrusions 26Ap is more than 20 nm and not more than 1000 nm. As illustrated in FIG. 6, if the second protrusions 26Ap are densely arranged and there are no gaps between adjacent second protrusions 26Ap (for example, the bases of the cones partially overlap), the equivalent area circle diameter Dp2 of the protrusions 26Ap is equal to the distance D2int between adjacent second protrusions 26Ap. The typical height Dh2 of the second protrusions 26Ap is 50 nm or more and less than 500 nm. The thickness t of the second synthetic polymer film 26A S2 There is no particular limitation on the height Dh2 of the second protrusion 26Ap.

[0025] As shown in the figure, the first protrusions 24Ap and the second protrusions 26Ap are, for example, conical. The first protrusions 24Ap and the second protrusions 26Ap may be protrusions whose cross-sectional area (cross section parallel to the film surface) increases as they approach the substrate 22A, or may be protrusions whose cross-sectional area (cross section parallel to the film surface) is constant. The two-dimensional arrangement on the surface of the multiple first protrusions 24Ap or multiple second protrusions 26Ap that make up the moth-eye structure preferably has low regularity (periodicity) and is preferably random.

[0026] In the above-described method for manufacturing a moth-eye mold, by adjusting the etching time of the anodized porous alumina layer, it is also possible to manufacture a moth-eye mold for forming a synthetic polymer film having multiple protrusions that satisfy the relationship Dint > Dp. A moth-eye structure is formed in which multiple protrusions (Dp1) with conical tips are arranged at intervals of Dint (> Dp).

[0027] The anti-fogging sheet structure 20A includes a second synthetic polymer film 26A in addition to a first synthetic polymer film 24A, and has a moth-eye structure on both surfaces, which suppresses reflection on both surfaces of the anti-fogging sheet structure 20A and provides ultra-low reflection performance. The moth-eye structure has low incidence angle dependence, so it provides a high anti-reflection effect even when attached to the inner surface of the shield 10 to form a curved surface.

[0028] 7 is a schematic cross-sectional view of an anti-fog sheet structure 20B according to an embodiment of the present invention. The anti-fog sheet structure 20B further includes a substrate 22B made of polycarbonate, a first synthetic polymer film 24B formed on a first main surface 22BS1 side of the substrate 22B, a second synthetic polymer film 26B formed on a second main surface 22BS2 side of the substrate 22B opposite to the first main surface 22BS1, and a third synthetic polymer film 28B formed between the first main surface 22BS1 of the substrate 22B and the first synthetic polymer film 24B.

[0029] The first synthetic polymer film 24B has a plurality of first protrusions 24Bp on its surface, the second synthetic polymer film 26B has a plurality of second protrusions 26Bp on its surface, and the third synthetic polymer film 28B has a plurality of third protrusions 28Bp on its surface. The plurality of first protrusions 24Bp, the plurality of second protrusions 26Bp, and the plurality of third protrusions 28Bp each form a moth-eye structure. The anti-fogging sheet structure 20B differs from the anti-fogging sheet structure 20A shown in FIG. 6 in that it includes the third synthetic polymer film 28B, but may otherwise be configured the same as the anti-fogging sheet structure 20A. The equivalent area circle diameter Dp3 and height Dh3 of the plurality of third protrusions 28Bp of the third synthetic polymer film 28B may be the same as the equivalent area circle diameter Dp2 and height Dh2 of the plurality of second protrusions 26Bp of the second synthetic polymer film 26B. The third synthetic polymer film 28B acts to improve the adhesion between the first synthetic polymer film 24B and the substrate 22B. To improve the adhesion between the second synthetic polymer film 26B and the substrate 22B, a fourth synthetic polymer film may be provided between the second main surface 22BS2 of the substrate 22B and the second synthetic polymer film 26B. The fourth synthetic polymer film may be formed in the same manner as the third synthetic polymer film 28B.

[0030] When the height of the plurality of first convex portions 24Ap, 24Bp is Dh1, it is preferable that Dh1 is 50 nm or more and that the aspect ratio A1 = Dh1 / Dp1 is less than 1.0. When the height of the plurality of second convex portions 26Ap, 26Bp is Dh2, it is preferable that the aspect ratio A2 = Dh2 / Dp2 is 1.0 or more. It is preferable that the aspect ratio A2 = Dh2 / Dp2 is 1.5 or less. It is preferable that the height Dh1 of the plurality of first convex portions 24Ap, 24Bp satisfies 150 nm ≦ Dh1 ≦ 300 nm, and it is preferable that the height Dh2 of the plurality of second convex portions 26Ap, 26Bp satisfies 150 nm ≦ Dh2 ≦ 200 nm. It is preferable that the height Dh1 of the plurality of first protrusions 24Ap, 24Bp is equal to or greater than the height Dh2 of the plurality of second protrusions 26Ap, 26Bp.

[0031] Because the first synthetic polymer films 24A, 24B are water-absorbent and have relatively low mechanical strength, the aspect ratio A1 = Dh1 / Dp1 is preferably less than 1.0. Compared to a flat surface, the moth-eye structure has a higher haze value due to light scattering. This tendency is greater in the first convex portions 24Ap, 24Bp, so by reducing the height of the second convex portions 26Ap, 26Bp, the haze value of the entire anti-fog sheet structure can be reduced.

[0032] The first synthetic polymer films 24A and 24B are formed from a cured product of a photocurable resin containing 30% by mass or more of ethoxylated pentaerythritol tetraacrylate. The anti-fog sheet structures 20A and 20B have anti-fog properties such that, when the surfaces of the first synthetic polymer films 24A and 24B are exposed to saturated water vapor at 50°C, the time it takes for the linear visible light transmittance of the first synthetic polymer films 24A and 24B to decrease to 80% of its initial value is 90 seconds or longer. The second synthetic polymer films 26A and 26B may be formed from a hydrophilic cured product of a photocurable resin that does not contain ethoxylated pentaerythritol tetraacrylate. The surfaces of the second synthetic polymer films 26A and 26B have hydrophilic surfaces with a static contact angle with water of less than 90°, as shown in the experimental examples below. The contact angle can be measured by a conventional method using a contact angle meter.

[0033] As will be explained later with reference to experimental examples, first synthetic polymer films 24A and 24B are preferably formed using, for example, the following materials. The compositions of the materials used in the experimental examples (U-105 to U-119) are shown in Tables 1 and 2 below. Ethoxylated pentaerythritol tetraacrylate (product name: ATM-35E, manufactured by Shin-Nakamura Chemical Co., Ltd.) Hydrophilic urethane acrylate (product name: UA-7100, manufactured by Shin-Nakamura Chemical Co., Ltd.) Hydrophilic urethane acrylate (product name: UA-W2A, manufactured by Shin-Nakamura Chemical Co., Ltd.) 2-(vinyloxyethoxy)ethyl acrylate (product name: VEEA, manufactured by Nippon Shokubai Co., Ltd.) n-Vinyl-2-pyrrolidone (NVP, product name: manufactured by Nippon Shokubai Co., Ltd.) Dimethylacrylamide (product name: DMAA, manufactured by KJ Chemicals Co., Ltd.) Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (initiator product name: Omnirad-819, manufactured by IGM Resins BV) Hydrophobic silicone additive (product name: JAR-36, manufactured by Jujo Chemical Co., Ltd.)

[0034] Ethoxylated pentaerythritol tetraacrylate (ATM-35E) contains 35 ethylene oxide (EO) groups in its molecule and is highly hydrophilic. When incorporated into a photocurable resin composition (excluding initiators and additives) at a concentration of 30% by mass or more, it can impart water absorption to the cured photocurable resin. Not only does the photocurable resin have hydrophilic properties on its surface, but it also has hygroscopic properties in bulk, resulting in excellent anti-fogging properties.

[0035] The hydrophilic urethane acrylates (UA-7100 and UA-W2A) have the advantage of being highly water-resistant and viscous, making them easy to form thick films. UA-7100 is less hydrophilic than UA-W2A, and the water absorption of a cured product obtained by curing a mixture of 70% by mass of UA-7100 and 30% by mass of 2-(2-vinyloxyethoxy)ethyl acrylate monomer is 2.0% or less, whereas the water absorption of a cured product obtained by curing a mixture of 70% by mass of UA-W2A and 30% by mass of 2-(2-vinyloxyethoxy)ethyl acrylate monomer exceeds 2.0%.

[0036] 2-(vinyloxyethoxy)ethyl acrylate (VEEA) has a small molecular weight and has the effect of improving adhesion to polycarbonate substrates through its anchoring effect.

[0037] n-Vinyl-2-pyrrolidone (NVP) also has the effect of improving adhesion to polycarbonate substrates, and is more hydrophilic than 2-(vinyloxyethoxy)ethyl acrylate (VEEA).

[0038] Dimethylacrylamide (DMAA), like n-vinyl-2-pyrrolidone (NVP), has high hydrophilicity and is effective in improving adhesion to polycarbonate substrates.

[0039] Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Omnirad-819) is a versatile UV-sensitive initiator.

[0040] By adding a small amount of hydrophobic silicone additive (JAR-36), when water droplets adhere to the surface of the first synthetic polymer film 24A, the water does not spread but remains as droplets on the surface, thereby maintaining visibility. The contact angle of the surface of the first synthetic polymer film 24A with water is preferably 20° or more.

[0041] The second synthetic polymer films 26A, 26B are preferably formed using, for example, the following materials. The composition (G05) of the materials used in the experimental example is shown in Table 1 below. The second synthetic polymer films 26A, 26B are provided to further improve the anti-reflection performance of the anti-fog sheet structures 20A, 20B, and are formed using, for example, the photocurable resin disclosed in the above-mentioned JP 2009-166502 A, WO 2011 / 125486 A, and WO 2013 / 183576 A. The surfaces of the second synthetic polymer films 26A, 26B do not need to be water-absorbent and may be either hydrophilic or hydrophobic. Polyethylene glycol diacrylate (product name: Miramer M280, manufactured by Miwon Specialty Chemical Co., Ltd.) Trimethylolpropane triacrylate (product name: Miramer M300, manufactured by Miwon Specialty Chemical Co., Ltd.) 2-(vinyloxyethoxy)ethyl acrylate (product name: VEEA, manufactured by Nippon Shokubai Co., Ltd.) Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (initiator product name: Omnirad-819, manufactured by IGM Resins BV) Diglycerin monolaurate (hydrophilic antiviral agent, product name: Poem DL-100, manufactured by Riken Vitamin Co., Ltd.)

[0042] The diglycerin monolaurate may be omitted.

[0043] The third synthetic polymer film 28B is preferably formed using, for example, the following materials: The composition of the materials used in the experimental example (BT7100, BTW2A) is shown in Table 3 below. Hydrophilic urethane acrylate (product name: UA-7100, manufactured by Shin-Nakamura Chemical Co., Ltd.) Hydrophilic urethane acrylate (product name: UA-W2A, manufactured by Shin-Nakamura Chemical Co., Ltd.) 2-(vinyloxyethoxy)ethyl acrylate (product name: VEEA, manufactured by Nippon Shokubai Co., Ltd.) Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (initiator product name: Omnirad-819, manufactured by IGM Resins BV)

[0044] Third synthetic polymer film 28B contains 30% by mass of 2-(vinyloxyethoxy)ethyl acrylate (VEEA) in the photocurable resin composition (excluding the initiator), and therefore has high adhesion to polycarbonate substrate 22B. Furthermore, third synthetic polymer film 28B contains hydrophilic urethane acrylate (UA-7100, UA-W2A), and therefore has excellent adhesion to first synthetic polymer film 24B.

[0045] Next, experimental examples will be shown to demonstrate that the anti-fog sheet structure according to the embodiment of the present invention has excellent anti-fog properties. The formulations of the photocurable resin compositions used in the experiments are shown in Tables 1 to 3 below.

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] In the experimental example, a polycarbonate film (NF-2000 Clear, manufactured by Mitsubishi Gas Chemical Company, Inc.) having a thickness of 0.7 mm and measuring 7 cm x 7 cm was used as the substrate.

[0050] The first synthetic polymer film had a plurality of first protrusions with an equivalent circle area diameter Dp1 of 150 nm and a distance Dint1 between adjacent protrusions of 180 nm.

[0051] The second synthetic polymer film had a plurality of second protrusions with an equivalent circle diameter Dp2 of 150 nm and an adjacent distance Dint2 of 150 nm. The third synthetic polymer film had a plurality of third protrusions with an equivalent circle diameter Dp3 and an adjacent distance Dint3 that were the same as the second protrusions' equivalent circle diameter Dp2 and the adjacent distance Dint2, respectively. That is, the same moth-eye forming mold was used to form the second synthetic polymer film and the third synthetic polymer film.

[0052] Figures 8 and 9 show example SEM images of the moth-eye structure of the first synthetic polymer film. The moth-eye structure in Figure 8 had a Dp1 of 150 nm, a Dint1 of 150 nm, and a Dh1 of 130 nm. The moth-eye structure in Figure 9 had a Dp1 of 150 nm, a Dint1 of 180 nm, and a Dh1 of 120 nm. The SEM images were obtained using an S-4700 electron microscope manufactured by Hitachi High-Technologies Corporation. As can be seen from these images, the desired moth-eye structure was formed.

[0053] For sample A, which is an anti-fog sheet structure of U-108 (thickness: 130 μm) / PC substrate (thickness: 0.7 mm) / G05 (thickness: 15 μm), the haze value, total light transmittance, reflectance (Y value), and L of transmitted light were measured. * a * b * a in color space * and b * The contact angle with water was measured. The haze value and total light transmittance were measured using a turbidity meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. The reflectance and chromaticity (a * and b * ) was measured using a spectrophotometer V-560 manufactured by JASCO Corporation. The contact angle with water was measured using a portable contact angle meter V-560 manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 4 below.

[0054] [Table 4]

[0055] Thus, the anti-fog sheet structure sample A has a low haze value of 1.0% or less, a high total light transmittance of visible light of 90.0% or more, and a low reflectance of 1.0% or less. * a * b * a in color space * The absolute value of and b * The absolute values ​​of each were independently 1.0 or less, indicating that no coloring occurred. Furthermore, the contact angle of the first synthetic polymer film with water was 20° or more, and when a water droplet adhered to the surface of the first synthetic polymer film, the water did not wet and spread, but remained on the surface as a droplet.

[0056] 6 and 7, the anti-fog sheet structure according to an embodiment of the present invention has an asymmetric structure in the thickness direction, and therefore, when immersed in water, for example, it curls so that the first synthetic polymer film side is convex. For example, when the above-mentioned anti-fog sheet structure sample A was immersed in a stainless steel tray filled with tap water and left for 5 hours, it was removed from the tray and its appearance was observed. When this was observed, it curled to a height of about 5 cm so that the first synthetic polymer film side was convex.

[0057] An example of evaluating anti-fogging properties using Sample B will be described. A hot bath was filled with hot water at 50°C (±0.5°C), and Sample B was placed on top of it so that the first synthetic polymer film (water-absorbing layer) was in contact with saturated water vapor. The time until fogging was visible (anti-fogging time) was measured. Since the visible light transmittance at the time when fogging was visible was higher than 80%, this can be said to be slightly stricter than the anti-fogging property evaluation test conforming to the ECE R22-5 standard. In addition, the dependency of anti-fogging time on the thickness of the first synthetic polymer film (water-absorbing layer) was evaluated. The results are shown in Table 5 below.

[0058] [Table 5]

[0059] It can be seen that an anti-fogging time of 90 seconds or more can be obtained when the thickness of the first synthetic polymer film is about 20 μm. It can also be seen that the anti-fogging time increases in proportion to the thickness of the first synthetic polymer film. From the viewpoint of mass productivity, it is preferable that the thickness of the first synthetic polymer film does not exceed about 150 μm, and it is preferable that an anti-fogging time of 90 seconds or more can be obtained when the thickness is about 20 μm or more and about 100 μm or less.

[0060] The hydrophilicity and water absorbency of the first synthetic polymer film were evaluated using each of the resin compositions (U-105 to U-119) shown in Tables 1 and 2, and the results are shown in Tables 6 to 8 below. Hydrophilicity was evaluated by observing the behavior in breath and hot water anti-fogging (50°C water bath surface) evaluations, with ◎ indicating that the film did not fog with breath and maintained a water film state on the 50°C water bath surface, and ○ indicating that the film did not fog with breath and did not change or form a water film on the 50°C water bath surface for a certain period of time, but began to fog later. Water absorbency was evaluated by measuring hot water anti-fogging (50°C water bath surface) evaluations, with ○ indicating an anti-fogging time of 90 seconds or more, △ indicating an anti-fogging time of 20 seconds or more but less than 90 seconds, and × indicating an anti-fogging time of less than 20 seconds.

[0061] After hydrophilicity and water absorption tests, the film may peel off or deform due to swelling (water resistance). U-113, U-115, U-117, and U-118 have some issues with water resistance. Furthermore, if the resin is soft, adjacent convex portions of the moth-eye structure may adhere to each other, resulting in sticking. Although it depends on the height of the convex portions, U-111 was prone to sticking. In addition to hydrophilicity and water absorption, U-105 and U-119 were particularly excellent in terms of water resistance and sticking resistance. Adhesion to the substrate can be improved, if necessary, by providing an adhesive layer (third synthetic polymer film) and selecting the appropriate material for the adhesive layer.

[0062] Of the anti-fog sheet structure samples used for evaluation, U-105 had the structure of the anti-fog sheet structure 20B shown in Figure 7, and the others had the structure of the anti-fog sheet structure 20A shown in Figure 6. The third synthetic polymer film was BT7100 (thickness: 50 μm). The second synthetic polymer film was G05 (thickness: 10 μm), and the first synthetic polymer film 50 had a thickness of 70 μm.

[0063] [Table 6]

[0064] [Table 7]

[0065] [Table 8]

[0066] The water absorption rates of the first synthetic molecular films (U-105, U-108, U-110, U-112) and the third synthetic molecular films (BT7100, BTW2A) were determined as follows.

[0067] The first or third synthetic molecular film was formed on a polycarbonate film (0.7 mm thick, 7 cm x 7 cm, 4.246 g) as a substrate. The initial mass A of each sample was measured, and the mass B of each sample at the time of fogging in the anti-fogging test was measured. The mass of water absorbed by the first or third synthetic molecular film was calculated using BA. The ratio of the absorbed mass to the initial mass of the first or third synthetic molecular film was expressed as a percentage, which was taken as the water absorption rate. The results are shown in Table 9.

[0068] [Table 9]

[0069] It can be seen that all of the first synthetic molecular films have a high water absorption rate of over 10%. In contrast, the water absorption rate of the third synthetic molecular film is low, and the water absorption rate of BT7100 in particular was low at 2% or less.

[0070] The abrasion resistance of an anti-fog sheet laminate according to an embodiment of the present invention was evaluated. The samples used were the anti-fog sheet laminate shown in Figures 8 and 9 and a commercially available anti-fog sheet. The test was performed using steel wool (product name: #0000, manufactured by Bonstar Co., Ltd.) at a rubbing speed of 6000 mm / min, a rubbing distance of 10 mm, and 10 rubbings.

[0071] In the abrasion resistance test, the commercially available products showed severe scratches, whereas the anti-fog sheet laminates according to the embodiments of the present invention showed only weak scratches. From this, it can be said that the anti-fog sheet laminates according to the embodiments of the present invention have sufficient abrasion resistance. [Industrial Applicability]

[0072] The anti-fog sheet laminate according to the embodiment of the present invention has excellent anti-fog properties and is suitable for use in helmets and the like. [Explanation of symbols]

[0073] 10: Shield 10a, 10b: Hole 12a, 12b: pin 20, 20A, 20B: Anti-fogging sheet structure 20SO:Outer surface 22A, 22B: Base material 22AS1, 22BS1: 1st main surface 22AS2, 22BS2: 2nd main surface 24A, 24B: First synthetic polymer membrane 24Ap, 24Bp: First convex part 26A, 26B: Second synthetic polymer membrane 26Ap, 26Bp: Second convex part 28B: Third synthetic polymer membrane 28Bp: Third convex part 100: Full-face helmet

Claims

1. a substrate formed of transparent plastic; a first synthetic polymer film formed on a first main surface side of the substrate; a second synthetic polymer film formed on a second main surface of the substrate opposite to the first main surface; and the first synthetic polymer film has, on its surface, a plurality of first protrusions each having an equivalent circle diameter Dp1 in the range of more than 50 nm and less than 500 nm when viewed in a normal direction of the first synthetic polymer film; the second synthetic polymer film has, on its surface, a plurality of second protrusions each having an equivalent circle diameter Dp2 in the range of more than 20 nm and less than 500 nm when viewed in a normal direction of the second synthetic polymer film; the first synthetic polymer film is formed from a cured product of a photocurable resin containing 30% by mass or more of ethoxylated pentaerythritol tetraacrylate, and the surface of the first synthetic polymer film is hydrophilic; the second synthetic polymer film is formed from a cured product of a photocurable resin, An anti-fog sheet structure having anti-fog properties in which, when the surface of the first synthetic polymer film is brought into contact with saturated water vapor at 50°C, the time it takes for the linear transmittance of visible light of the first synthetic polymer film to decrease to 80% of its initial value is 90 seconds or more.

2. An anti-fogging sheet structure as described in claim 1, wherein the surface of the second synthetic polymer film is hydrophilic.

3. When the height of the plurality of first convex portions is Dh1, Dh1 is 50 nm or more, and an aspect ratio A1 = Dh1 / Dp1 is less than 1.0, 3. The anti-fogging sheet structure according to claim 1, wherein when the height of the plurality of second convex portions is Dh2, an aspect ratio A2 = Dh2 / Dp2 is 1.0 or more.

4. The anti-fogging sheet structure according to claim 3 , wherein the height Dh1 of the plurality of first convex portions satisfies 150 nm≦Dh1≦300 nm.

5. The anti-fogging sheet structure according to claim 3 , wherein a height Dh2 of the plurality of second convex portions satisfies 150 nm≦Dh2≦200 nm.

6. The anti-fog sheet structure according to claim 3 , wherein the aspect ratio A2=Dh2 / Dp2 is 1.5 or less.

7. The anti-fogging sheet structure according to claim 3 , wherein a height Dh1 of the plurality of first convex portions is equal to or greater than a height Dh2 of the plurality of second convex portions.

8. 3. The anti-fog sheet structure according to claim 1, wherein the surface of the first synthetic polymer film has a contact angle with water of 20° or more.

9. The anti-fog sheet structure according to claim 1 or 2, wherein the first synthetic polymer film is formed from a cured product of the photocurable resin further containing urethane acrylate.

10. The urethane acrylate is a cured product obtained by curing a mixture of 70% by mass of the urethane acrylate and 30% by mass of 2-(2-vinyloxyethoxy)ethyl acrylate monomer.

10. The anti-fog sheet structure of claim 9, comprising a urethane acrylate percentage greater than 2.0%.

11. a third synthetic polymer film formed between the first main surface of the substrate and the first synthetic polymer film; 3. The anti-fog sheet structure according to claim 1, wherein the third synthetic polymer film has, on its surface, a plurality of third convex portions each having an equivalent circle diameter Dp3 in the range of more than 20 nm and less than 500 nm when viewed from a normal direction of the third synthetic polymer film.

12. 3. The anti-fog sheet structure according to claim 1, wherein the haze value is 1.0 or less.

13. L of transmitted light ＊ a ＊ b ＊ a in color space ＊ The absolute value of and b ＊ The anti-fog sheet structure according to claim 1 or 2, wherein the absolute values ​​of are each independently 1.0 or less.

14. A helmet having a shield and a shell, The shield further includes an anti-fogging sheet structure disposed inside the shield via a gap, 3. A helmet, wherein the anti-fog sheet structure is the anti-fog sheet structure according to claim 1 or 2, and is configured so that the first synthetic polymer film is positioned on the inside when the helmet is worn.

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