Translucent resin material

Abstract

To provide a translucent resin member which can suppress such color appearance that a translucent resin member seems to be colored according to a viewpoint position.SOLUTION: There is provided a translucent resin member 10A in which a plurality of groove structures composed of a plurality of linear projections and a plurality of linear recesses are formed on at least a part of its surface, wherein the linear projections and the linear recesses extend in a direction parallel to each other, the grooves are formed at such a pitch that transmittance of visible light which is incident in a region where the grooves are formed on the surface, and is incident at a predetermined range of an incident angle to permeate the translucent resin member becomes substantially a constant.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a translucent resin member, and more particularly to a translucent resin member that can suppress color appearance, in which the translucent resin member appears to change color depending on the viewpoint. [Background technology]

[0002] Patent Document 1 describes a light-transmitting resin member having a plurality of groove structures formed on the surface at a uniform pitch, the groove structures being made up of a plurality of linear convex portions and a plurality of linear concave portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-189207 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inventors have found through their research that increasing the groove pitch of the grooves formed in a translucent resin member (e.g., an outer lens) changes the transmittance of visible light passing through the translucent resin member, resulting in a problem in that the translucent resin member appears to change color depending on the viewpoint.

[0005] The present invention has been made to solve such problems, and aims to provide a translucent resin member that can suppress the color appearance that occurs when the translucent resin member appears to change color depending on the viewpoint position. [Means for solving the problem]

[0006] The translucent resin member of the present invention is a translucent resin member having a plurality of groove structures formed on at least a part of its surface, each of which is composed of a plurality of linear convex portions and a plurality of linear concave portions, wherein the linear convex portions and the linear concave portions extend in directions parallel to each other, and the grooves are formed at a pitch such that the transmittance of visible light incident on the region of the surface where the grooves are formed and passing through the translucent resin member at an incident angle within a predetermined range is approximately constant.

[0007] With this configuration, it is possible to suppress color appearance, in which the translucent resin member appears to be colored depending on the viewpoint position.

[0008] This is because the grooves are formed at a pitch such that the transmittance of visible light within a specified angle range that enters the area of ​​the surface where the grooves are formed and passes through the translucent resin member is approximately constant.

[0009] In the above-described light-transmitting resin member, the grooves may be arranged at non-uniform pitches.

[0010] In the above-mentioned translucent resin member, when the maximum pitch of the grooves is b(max), the minimum pitch of the grooves is b(min), and the average pitch of the grooves is b(ave), {b(max)-b(min)} / b(ave)≧0.16 may be satisfied.

[0011] With this configuration, when the grooves are arranged at non-uniform pitches, it is possible to suppress color appearance in which the translucent resin member (second region) appears to be colored depending on the viewpoint position.

[0012] In the above-described light-transmitting resin member, the grooves may be arranged at uniform intervals.

[0013] In the above-mentioned light-transmitting resin member, when the uniform pitch is a, a≦200 nm may be satisfied.

[0014] With this configuration, when the grooves are arranged at a uniform pitch, it is possible to suppress color appearance in which the translucent resin member (first region) appears to be colored depending on the viewpoint position.

[0015] In the above-described translucent resin member, the linear convex portions and the linear concave portions extend in directions parallel to each other, and an average width W1 of the linear convex portions may be 75 nm≦W1≦200 nm, an average width W2 of the linear concave portions, which is the width of the groove, may be 75 nm≦W2≦450 nm, a pitch P between adjacent grooves may be 150 nm≦P≦600 nm, an aspect ratio D / W2 of the depth D of the groove to the width W2 of the groove may be 2.0≦D / W2, an angle θ1 of the sidewall of the groove with respect to a reference plane may be 60°≦θ1≦90°, and a contact angle θ2 of water with respect to the surface on which the grooves are not formed may be 60°≦θ2≦90°.

[0016] With this configuration, it is possible to suppress a decrease in light transmittance due to the groove structure, while achieving the desired anti-fogging effect.

[0017] In the above-mentioned light-transmitting resin member, the width W1 of the linear convex portion and the width W2 of the linear concave portion may be substantially the same.

[0018] In the above-described translucent resin member, the translucent resin member is a translucent resin member through which light irradiated from a light source of a vehicle lamp passes, and the linear convex portion and the linear concave portion may be formed on a back surface of the translucent resin member.

[0019] In the above-described light-transmitting resin member, the material of the light-transmitting resin member may be acrylic or polycarbonate. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a translucent resin member that can suppress color appearance, in which the translucent resin member appears to change color depending on the viewpoint position. [Brief explanation of the drawings]

[0021] [Figure 1]It is a partial perspective view (schematic view) of the translucent resin member 10. [Figure 2] It is a partial cross-sectional view (schematic view) of the translucent resin member 10. [Figure 3] It is an example of a groove (rectangular groove) when the groove angle θ1 is 90°. [Figure 4] It is a diagram for explaining the anti-fogging effect confirmation test (steam test). [Figure 5] It is a table summarizing the presence or absence of the anti-fogging effect and the like of samples S1 to S6 with different aspect ratios D / W2 and groove angles θ1. [[ID=I4]] [Figure 6] [[ID=I5]]It is a table summarizing the specifications and the like of samples S1 to S6. [Figure 7] It is a photograph of samples S1 to S6. [Figure 8] It is a table summarizing the presence or absence of the anti-fogging effect and the like of samples S1 to S6. [Figure 9] It is an example of a grid-like mass. [Figure 10] It is an example of the use of a grid-like mass. [Figure 11] (a) An example of a rectangular groove with a filling rate = groove width W / groove pitch D = 0.4 and a groove height H = 400 nm, (b) A graph representing the transmittance of light Ray (simulation result) when the groove pitch D shown in Fig. 11(a) is changed. [Figure 12] It is a graph representing the measured transmittance results. [Figure 13] It is a modified example of the cross-sectional shape of the tip of the linear convex portion 11. [Figure 14] [[ID=I39]](a) An example of an outer lens 10A, (b) An example of grooves formed in the outer lens 10A at an equal pitch a, (c) An example of grooves formed in the outer lens 10A at unequal pitches b1, b2 (b1 < b2). [Figure 15] (a) A diagram showing a state where after the resin (resin material such as acrylic or polycarbonate) poured into the molds 40A and 40B is cooled and solidified, the mold 40A is removed from the molded product (here, the outer lens 10A) in the direction of the arrow Ar1, (b) A graph representing the relationship between the surface roughness Ra of the mold and the脱模 resistance. [Figure 16]1 is a diagram showing a state in which light Ray (visible light) is incident on an outer lens 10A at an angle θ. [Figure 17] 10 is a graph showing the results of simulation 1. [Figure 18] 10 is a graph showing the results of simulation 2. [Figure 19] 19 is a table summarizing the groove pitches and average transmittances shown in FIG. 18. [Figure 20] 10 is a graph showing the results of Simulation 3. [Figure 21] 21 is a table summarizing the groove pitches and average transmittances shown in FIG. 20. [Figure 22] 14 is a table summarizing the relationship between the surface roughness Ra of the mold and the assumed demolding resistance ratio when grooves formed in the outer lens 10A have uneven pitches (see symbols b1 and b2 in FIG. 14(c)). [Figure 23] 10 is a table summarizing the results (anti-fogging properties) of an anti-fogging effect confirmation test conducted on samples S7 to S10 having different groove pitches. [Figure 24] (a) An example of grooves formed with uneven pitches (three or more types of groove pitch), (b) a graph summarizing the results of Simulation 4. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Embodiment 1> Hereinafter, as a first embodiment, a light-transmitting resin member 10 that can suppress a decrease in light transmittance due to a groove structure while exhibiting a desired anti-fogging effect will be described with reference to the accompanying drawings. Corresponding components in each drawing are given the same reference numerals, and redundant explanations will be omitted.

[0023] The light-transmitting resin member 10 of the first embodiment is used, for example, as an inner lens or an outer lens of a vehicle lamp (not shown). The vehicle lamp is, for example, a vehicle headlamp or a vehicle signal lamp (for example, a rear combination lamp).

[0024] Fig. 1 is a partial perspective view (schematic diagram) of a light-transmitting resin member 10. Fig. 2 is a partial cross-sectional view (schematic diagram) of the light-transmitting resin member 10.

[0025] 1 and 2, the shape of the light-transmitting resin member 10 is a flat plate. However, the shape of the light-transmitting resin member 10 is not limited to a flat plate shape, and it can have various shapes (for example, a curved shape) depending on the vehicle design, etc. The material of the light-transmitting resin member 10 is acrylic (PMMA) or polycarbonate.

[0026] A plurality of grooves (groove structures) are formed on the surface of the light-transmitting resin member 10. The surface of the light-transmitting resin member 10 is the surface (the surface facing the vehicle lamp (light source)) into which light emitted from a light source of the vehicle lamp (for example, a semiconductor light-emitting element such as an LED that constitutes the vehicle lamp) enters. Hereinafter, the surface of the light-transmitting resin member 10 will also be referred to as the back surface of the light-transmitting resin member 10. groove structure is composed of a plurality of linear protrusions 11 and a plurality of linear recesses 12. The linear recess 12 is a groove. The linear protrusions 11 and the linear recesses 12 extend linearly in directions parallel to each other. Note that the linear protrusions 11 and the linear recesses 12 may extend in curved lines in directions parallel to each other. Hereinafter, as shown in FIG. 1, the direction in which the linear protrusions 11 and the linear recesses 12 extend will be referred to as the groove direction. Furthermore, the direction intersecting (perpendicular to) the groove direction will be referred to as the groove intersecting direction.

[0027] The average width W1 of the linear convex portions 11 (hereinafter also referred to as convex portion width W1) is 75 nm≦W1≦200 nm (Equation 1). The average width W2 of the linear concave portions 12 (hereinafter also referred to as groove width W2) is 75 nm≦W2≦450 nm (Equation 2). The pitch P between adjacent grooves (hereinafter referred to as groove pitch P) is 150 nm≦P≦600 nm (Equation 3). The aspect ratio D / W2 of the groove depth D to the groove width W2 is 2.0≦D / W2 (Equation 4). Note that the width W1 of the linear convex portions and the width W2 of the linear concave portions may be substantially the same, i.e., W1≈W2. The angle θ1 of the sidewall of the groove with respect to the reference plane (hereinafter referred to as groove angle θ1) is 60°≦θ1≦90° (Equation 5). Figure 2 shows an example of a groove (triangular groove) with a groove angle θ1 of 78°, and Figure 3 shows an example of a groove (rectangular groove) with a groove angle θ1 of 90°.

[0028] The contact angle θ2 (not shown) of water with respect to the surface of the translucent resin member 10 (a flat surface on which no grooves are formed) is within a range outside the range in which high hydrophilicity is obtained (60° or less) and the range in which high water repellency is obtained (more than 90°), i.e., 60°≦θ2≦90° (Equation 6).

[0029] Even if the base resin of a resin material such as acrylic or polycarbonate is the same, it may be copolymerized with other resin materials or modified with additives or structures to improve various properties such as strength, heat resistance, translucency, and wettability. Therefore, there are many varieties of the same acrylic (or polycarbonate). These effects cause the surface energy of the same acrylic (or polycarbonate) to vary, resulting in various water contact angles with the surface. In contrast, strength, heat resistance, and light transmittance are important for vehicle lamps such as vehicle headlamps and vehicle signal lamps (e.g., rear combination lamps). Therefore, a translucent resin member 10 made of a resin material such as acrylic (or polycarbonate) that meets the strength, heat resistance, and light transmittance required for vehicle lamps is used. The water contact angle θ2 of the surface (flat surface without grooves) of the translucent resin member 10 made of a resin material such as acrylic (or polycarbonate) that meets the strength, heat resistance, and light transmittance required for vehicle lamps is 60°≦θ2≦90°.

[0030] The water contact angle θ2 can be measured, for example, by a contact angle meter (for example, a portable contact angle meter PCA-11 manufactured by Kyowa Interface Science Co., Ltd.). The fact that high hydrophilicity is obtained in a range of 60° or less and high water repellency is obtained in a range of more than 90° is described, for example, in Patent Document 1.

[0031] The groove (groove structure) having the above configuration can be formed, for example, by thermal imprinting on the light-transmitting resin substrate. Alternatively, the groove (groove structure) having the above configuration can be formed by molding (injection molding) the light-transmitting resin member 10 using a mold.

[0032] By using a translucent resin member 10 that satisfies the above formulas 1 to 6, it is possible to suppress a decrease in light transmittance (transmittance of light irradiated from a vehicle lamp) due to the groove structure, while achieving the desired anti-fogging effect (anti-fogging effect on the back surface of the translucent resin member 10). Furthermore, by using a translucent resin member 10 that satisfies the above formulas 1 to 6, droplets that adhere to the linear recesses 12 are less likely to flow, and the capillary force of the grooves (groove structure) stretches the water droplets in the groove direction, expanding the surface area of ​​the water droplets and promoting evaporation of the water droplets. This allows the water droplets to evaporate before they accumulate inside the vehicle lamp, thereby achieving an anti-fogging effect.

[0033] The above formulas 1, 2, and 4 to 6 are conditions for achieving the desired anti-fogging effect. Hereinafter, an anti-fogging effect confirmation test (steam test) conducted by the present inventors to derive some of the ranges of these conditions will be described. <Anti-fogging effect confirmation test (steam test)> FIG. 4 is a diagram for explaining the anti-fogging effect confirmation test (steam test).

[0034] As shown in Fig. 4, in the anti-fogging effect confirmation test (steam test), a stainless steel bottle 21 containing salt water 20 (NaCl) was heated with hot water 23 (40°C) in a hot water bath 22 to generate steam 24 (relative humidity 74%RH), and this steam 24 was applied to the underside of sample S, which is a light-transmitting resin member 10. Sample S is samples S1 to S6, which will be described below. The underside 25 of sample S includes a processed surface on which a groove structure is formed by thermal imprinting and a base surface (flat surface) on which no groove structure is formed.

[0035] Then, one minute after the steam generation, the degree of water droplets adhering to the lower surface 25 (the processed surface and the base surface) of the sample S was observed (photographed) using a microscope camera 26 with an objective lens.

[0036] Figure 5 is a table summarizing the presence or absence of anti-fogging effects for samples S1 to S6, which have different aspect ratios D / W2 and groove angles θ1. Figure 6 is a table summarizing the specifications of samples S1 to S6. Samples S1 to S6 are acrylic flat plates (60 mm square, 2 mm thick). The specifications of samples S1 to S6 are as follows (see Figures 5 and 6). <Sample S1> Sample S1 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=300 nm, groove depth D=150 nm, groove width W2=150 nm, aspect ratio D / W2=1.0, and groove angle θ1=90°. <Sample S2> Sample S2 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=300 nm, groove depth D=150 nm, groove width W2=150 nm, aspect ratio D / W2=1.0, and groove angle θ1=60°. <Sample S3> Sample S3 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=300 nm, groove depth D=200 nm, groove width W2=150 nm, aspect ratio D / W2=1.3, and groove angle θ1=90°. <Sample S4> Sample S4 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=300 nm, groove depth D=300 nm, groove width W2=150 nm, aspect ratio D / W2=2.0, and groove angle θ1=90°. <Sample S5> Sample S5 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=300 nm, groove depth D=300 nm, groove width W2=150 nm, aspect ratio D / W2=2.0, and groove angle θ1=78°. <Sample S6> Sample S6 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch P=150 nm, groove depth D=200 nm, groove width W2=75 nm, aspect ratio D / W2=2.7, and groove angle θ1=90°.

[0037] The above test results using samples S4 and S5 show that, when the aspect ratio is 2.0, the desired anti-fogging effect is achieved with both groove angles θ1 = 78° and θ1 = 90°. This is thought to be because the capillary force of the grooves (groove structure) stretches the water droplets in the groove direction and the groove intersection direction, expanding the surface area of ​​the water droplets and promoting their evaporation. Furthermore, the groove angle θ1 = 90° (rectangular groove) (sample 4) exhibits low and favorable water droplet density and water droplet area ratio, but the water droplet size increases to about 100 μm, making it easy to observe with the naked eye.

[0038] FIG. 7 is a photograph of samples S1 to S6. In FIG. 7, the area A1 above the line L represents the processed surface on which the groove structure is formed, and the area A2 below the line L represents the base surface (flat surface) on which the groove structure is not formed. In FIG. 7, the white circles or ellipses represent water droplets, and the direction in which the line L extends represents the direction in which the grooves extend. FIG. 8 is a table summarizing the presence or absence of the anti-fogging effect of samples S1 to S6. The presence or absence of the anti-fogging effect in FIG. 8 was evaluated using the evaluation method described below. <Method for evaluating the presence or absence of anti-fogging effect> First, the "droplet area (machined surface)" in Figure 8 is calculated. The "droplet area (machined surface)" represents the proportion of the area occupied by water droplets attached to the machined surface on which the groove structure is formed. The "droplet area (machined surface)" can be calculated, for example, using a grid-like grid (e.g., 20 x 20 grid) as shown in Figure 9. Figure 9 is an example of a grid-like grid. The grid-like grid is used by overlaying it on a photograph as shown in Figure 10. Figure 10 is an example of how to use a grid-like grid. Specifically, the area occupied by water droplets attached to the machined surface on which the groove structure is formed is measured in terms of the number of grids, and the proportion of this to the total area (e.g., 400 grids) is calculated (number of grids of water droplets (net number of grids) / 400). Note that the measurement area was selected visually based on the area with the most water droplets, not on an area with a low water droplet distribution. The measurement error was approximately 2 to 3%.

[0039] Next, calculate the "droplet area (base surface)" in Figure 8. The "droplet area (base surface)" represents the proportion of water droplets adhering to the base surface where no groove structure is formed. Like the "droplet area (machined surface)," the "droplet area (base surface)" can be calculated using a grid (e.g., 20 x 20 grid) shown in Figure 9.

[0040] Next, calculate the "droplet presence ratio" in Fig. 8. The "droplet presence ratio" can be calculated by ("droplet area (machined surface)" / "droplet area (base surface)") x 100.

[0041] For example, for sample 4, the percentage of reduced water droplet adhesion compared to the bare surface can be calculated as follows: water droplet presence ratio on the bare surface (100%) - "water droplet presence ratio" on the processed surface (16.8%) = 83.2%. Similar calculations can be made for the other samples 1 to 3, 5, and 6.

[0042] In the first embodiment, samples (here, Samples 4 to 6) where the ratio of the water droplet adhesion on the processed surface to the base surface (i.e., the water droplet presence ratio on the base surface (100%) minus the "droplet presence ratio" on the processed surface satisfied an evaluation criterion (e.g., 50% or more) were evaluated as having the desired "anti-fogging effect." The other samples (here, Samples 1 to 3) were evaluated as having the desired "anti-fogging effect." For example, in the case of Sample 4 in FIG. 8, the droplet area on the processed surface is 9.8% and the droplet area on the base surface is 58.5%, so the droplet presence ratio (processed surface ÷ base surface × 100) is 16.8%. In other words, it can be seen that the area of ​​droplets adhering to the processed surface is only 16.8% of the area of ​​droplets adhering to the base surface. Therefore, it can be seen that the amount of droplet adhesion was reduced by 83.2% (100% - 16.8% = 100%) compared to the base surface. Note that the evaluation criterion is not limited to 50% or more, and other numerical values ​​or more may be used.

[0043] The above formula 3 is a condition for suppressing a decrease in light transmittance (transmittance of light irradiated from a vehicle lamp) due to the groove structure. Below, we will explain the simulations that the inventors performed using predetermined software (Wave Optics Module, manufactured by COMSOL) to derive this condition. <Suppression of transmittance reduction (simulation)> Figure 11(a) shows an example of rectangular grooves with a filling factor of 0.4 (groove width W / groove pitch D) and a groove height of 400 nm. In Figure 11(a), multiple grooves (groove structures) are formed on the underside of a lens layer (similar in size to samples S1 to S6). The grooves (groove structures) are composed of multiple convex portions and multiple concave portions protruding from the underside of the lens layer.

[0044] FIG. 11(b) is a graph showing the transmittance (simulation results) of the light Ray (see FIG. 11(a)) when the groove pitch D shown in FIG. 11(a) is changed. In FIG. 11(b), the symbol WL 480 represents the transmittance of light with a wavelength of 480 nm (simulation result), and the symbol WL 580 indicates the transmittance of light with a wavelength of 580 nm (simulation results).

[0045] 11(b), it can be seen that for light with a wavelength of 480 nm, the transmittance is roughly constant up to a groove pitch D of 300 nm, but the transmittance decreases when the groove pitch D is 300 nm or more. Also, for light with a wavelength of 580 nm, the transmittance is roughly constant up to a groove pitch D of 360 nm, but the transmittance decreases when the groove pitch D is 360 nm or more.

[0046] From the above results, it can be seen that for visible light with a wavelength of 480 nm or more, a decrease in transmittance can be suppressed by setting the groove pitch D to 480 nm x 0.62 = 300 nm or less. It can also be seen that for visible light with a wavelength of 580 nm or more, a decrease in transmittance can be suppressed by setting the groove pitch D to 580 nm x 0.62 = 360 nm or less. Note that 0.62 is a coefficient calculated using 300 nm / 480 nm and 360 nm / 580 nm.

[0047] In light of the above, when it is desired to transmit visible light with a wavelength of 380 nm or more (for example, when the light-transmitting resin member 10 is used as an inner lens or outer lens of a vehicle headlamp), it is clear that a decrease in transmittance can be suppressed by setting the groove pitch D to 380 nm × 0.62 ≒ 235 nm or less. In this case, it is desirable that the lower limit be 150 nm or more so that part of ultraviolet light can be transmitted.

[0048] Furthermore, when it is desired to transmit visible light with wavelengths of 630 nm or more (red visible light) (for example, when the translucent resin member 10 is used as an inner lens or outer lens of a vehicle signal lamp), it is found that the decrease in transmittance can be suppressed by setting the groove pitch D to 630 nm × 0.62 ≒ 390 nm or less.

[0049] Furthermore, when it is desired to transmit visible light with a wavelength of 580 nm or more (amber visible light) (for example, when the light-transmitting resin member 10 is used as an inner lens or outer lens of a vehicle signal lamp), it is found that a decrease in transmittance can be suppressed by setting the groove pitch D to 580 nm × 0.62 ≒ 360 nm or less. Fig. 12 is a graph showing the results of actual transmittance measurements.

[0050] In FIG. 12, symbol WL1 represents the transmittance (simulation result) without a groove structure, symbol WL2 represents the transmittance (simulation result) with a groove structure (rectangular groove, groove depth 300 nm), and symbol WL3 represents the actual measurement result with a groove structure (aspect ratio = 2, groove width = 150 nm, groove depth = 300 nm, groove pitch = 300 nm, groove angle θ1 = 78°).

[0051] 12, it can be seen that the drop in transmittance (measured results) occurs around a wavelength of 480 nm, which is consistent with the simulation result (484 = 300 / 0.62). It can also be seen that approximately 85% of visible light with wavelengths of 480 nm or more (measured results) is transmitted, which indicates that the decrease in transmittance has been suppressed.

[0052] As described above, according to the first embodiment, it is possible to provide a light-transmitting resin member 10 that can exert a desired anti-fogging effect while suppressing a decrease in light transmittance due to the groove structure.

[0053] The use of the above formula 3 makes it possible to suppress the reduction in light transmittance due to the groove structure.

[0054] The desired anti-fogging effect can be achieved by employing the above formulas 1, 2, and 4 to 6.

[0055] Furthermore, according to the first embodiment, when the translucent resin member 10 is used as an inner lens or an outer lens of a vehicle headlamp, by setting the groove pitch D to 380 nm × 0.62 ≒ 235 nm or less, it is possible to suppress a decrease in light transmittance (transmittance of light (visible light of 380 nm or more) irradiated from the vehicle headlamp) while achieving the desired anti-fogging effect.

[0056] Furthermore, according to embodiment 1, when the translucent resin member 10 is used as an inner lens or an outer lens of a vehicle signal lamp, by setting the groove pitch D to 630 nm × 0.62 ≒ 390 nm or less, it is possible to suppress a decrease in light transmittance (transmittance of light irradiated from the vehicle signal lamp (red visible light of 630 nm or more)) while achieving the desired anti-fogging effect.

[0057] Furthermore, according to the first embodiment, when the translucent resin member 10 is used as an inner lens or an outer lens of a vehicle signal lamp, by setting the groove pitch D to 580 nm × 0.62 ≒ 360 nm or less, it is possible to suppress a decrease in light transmittance (transmittance of light (amber-based visible light of 580 nm or more) irradiated from the vehicle signal lamp) while achieving the desired anti-fogging effect.

[0058] Next, a modified example will be described.

[0059] In the first embodiment, the light-transmitting resin member 10 is used as an inner lens or an outer lens of a vehicle headlamp or a vehicle signal lamp, but the present invention is not limited to this.

[0060] For example, the light-transmitting resin member 10 may be used as a light-transmitting resin member that transmits light (wavelength: about 1-10 μm) emitted from a light source for radar (for example, an infrared LiDAR that is a distance measurement element). In this case, by setting the groove pitch D to 780 nm (the upper limit wavelength of visible light) × 0.62 ≒ 483 nm or less, it is possible to suppress a decrease in light transmittance (transmittance of light (light of 780 nm or more) irradiated from a light source for radar) and to achieve the desired anti-fogging effect.

[0061] Furthermore, in the above-described first embodiment, the cross-sectional shape of the tip of the linear protrusion 11 is a flat surface (see FIGS. 2 and 3), but the present invention is not limited to this.

[0062] FIG. 13 shows a modified example of the cross-sectional shape of the tip of the linear protrusion 11.

[0063] As shown in FIG. 13, the cross-sectional shape of the tip of the linear convex portion 11 may be an arc shape convex toward the outside.

[0064] By doing so, due to the convex arc shape of the tip of the linear convex portion 11, the contact angle with the water droplet becomes small and the surface area of the water droplet expands. As a result, the evaporation of the water droplet is promoted, so that the anti-fogging effect can be improved. <Embodiment 2> Next, the light-transmissive resin member of Embodiment 2 will be described. The light-transmissive resin member of Embodiment 2 is an example in which the light-transmissive resin member 10 of the above Embodiment 1 is applied to an outer lens. Hereinafter, it is referred to as an outer lens 10A.

[0065] FIG. 14(a) is an example of the outer lens 10A, FIG. 14(b) is an example of the grooves formed in the outer lens 10A at an equal pitch a, and FIG. 14(c) is an example of the grooves formed in the outer lens 10A at unequal pitches b1, b2 (b1 < b2).

[0066] The outer lens 10A is attached to a housing (not shown), and constitutes a lamp chamber S in which a lamp unit 30 is disposed between the outer lens 10A and the housing. The lamp unit 30 is, for example, a projector-type lamp unit. However, the lamp unit 30 is not limited thereto, and may be a reflector-type lamp unit, a direct projection type (so-called direct type) lamp unit, a lamp unit using a light guide (for example, a light guide rod, a light guide plate), or other lamp units. Further, the lamp unit 30 may be an optical unit for a headlamp, a lamp unit for a vehicle signal lamp, or other lamp units. The lamp unit 30 is an example of the vehicle lamp of the present invention.

[0067] The light-transmissive resin member (outer lens 10A) of Embodiment 2 is mainly different from the light-transmissive resin member 10 of the above Embodiment 1 in the following points.

[0068] That is, in the light-transmitting resin member 10 of the above-mentioned embodiment 1, the grooves (groove structure) were formed at equal pitches on the surface of the light-transmitting resin member 10, whereas in the light-transmitting resin member (outer lens 10A) of embodiment 2, the grooves (groove structure) are formed at equal pitches a (see FIG. 14(b)) in a first region B1 (see FIG. 14(a)) on the surface of the light-transmitting resin member (outer lens 10A), and are formed at unequal pitches b1, b2 (see FIG. 14(c)) in a second region B2 (see FIG. 14(a)) other than the first region B1 on the surface of the light-transmitting resin member (outer lens 10A).

[0069] The first region B1 is a region that contributes to the optical characteristics of the lamp unit 30. Specifically, the first region B1 is mainly a region on the surface of the outer lens 10A that affects the optical characteristics of the light that is incident on and transmitted by the lamp unit 30. On the other hand, the second region B2 is a region that does not contribute to the optical characteristics of the lamp unit 30. Specifically, the second region B2 is mainly a region on the surface of the outer lens 10A other than the first region B1.

[0070] The groove pitch of the grooves formed in the first region B1 is a uniform pitch a (see FIG. 14(b)). Hereinafter, this will also be referred to as the first pitch a. On the other hand, the groove pitch of the grooves formed in the second region B2 is an uneven pitch b1, b2 (see FIG. 14(c)). Hereinafter, this will also be referred to as the second pitch b1 and the third pitch b2.

[0071] The average pitch ((b1+b2) / 2) of the grooves formed in the second region B2 is greater than the first pitch a. That is, there is the relationship a<(b1+b2) / 2 (Equation 7). Equation 7 is a condition for reducing mold release resistance when the outer lens 10A is molded (injection molded) using a mold.

[0072] There is also the relationship a≦200 nm (Equation 8), which is a condition for suppressing color appearance in which the outer lens 10A (first region B1) appears colored depending on the viewpoint position E (see FIG. 16).

[0073] Furthermore, in addition to the condition of formula 7, if the maximum pitch of the grooves formed in the second region B2 is b(max), the minimum pitch of the grooves formed in the second region B2 is b(min), and the average pitch of the grooves formed in the second region B2 is b(ave), then there is the relationship {b(max)-b(min)} / b(ave)≧0.16 (formula 9). Formula 9 is a condition for suppressing color appearance, in which the outer lens 10A (second region B2) appears colored depending on the viewpoint position E (see FIG. 16).

[0074] As described above, in the second embodiment, the grooves are formed in the first region B1 at an equal pitch a (see FIG. 14(b)) that satisfies the above formula 8. On the other hand, the grooves are formed in the second region B2 at unequal pitches b1 and b2 (see FIG. 14(c)) that satisfy the above formulas 7 and 9.

[0075] By satisfying the above formula 7, it is possible to reduce mold release resistance when the outer lens 10A is molded (injection molded) using a mold. Furthermore, by satisfying the above formulas 8 and 9, it is possible to suppress color appearance in which the outer lens 10A (first region B1, second region B2) appears colored depending on the viewpoint position E (see FIG. 16). Furthermore, by satisfying formulas 1 to 6 described in the above embodiment 1, antifogging properties (desired antifogging effect) are achieved.

[0076] Simulations and the like carried out by the present inventors to derive the above formulas 7 to 9 will be described below.

[0077] Figure 15(a) shows the state in which the mold 40A is removed from the molded product (here, the outer lens 10A) in the direction of arrow Ar1 after the resin (a resin material such as acrylic or polycarbonate) poured into the molds 40A and 40B has cooled and solidified.

[0078] As shown in FIG. 15(a), when an outer lens 10A having a groove (see symbol G in FIG. 16) formed therein is molded (injection molded), mold release resistance increases when attempting to remove the mold 40A from the molded product. Mold release resistance refers to the force that causes the molded product to adhere to and remain in contact with the mold 40B. Therefore, when removing the mold 40A from the molded product, a force greater than the mold release resistance is applied to the molded product, which may result in deformation of the molded product. Furthermore, there may be cases where the mold 40A cannot be removed from the molded product at all. Therefore, a small mold release resistance is desirable.

[0079] Figure 15(b) is a graph showing the relationship between the mold surface roughness Ra and demolding resistance. This graph is taken from "Relationship between Core Surface Roughness and Demolding Resistance in Injection Molding" by Kobayashi Yoshikazu et al., Journal of the Japan Society for Precision Engineering, Vol. 67, No. 3, 2001. In Figure 15(b), the vertical axis represents demolding resistance, and the horizontal axis represents the mold surface roughness Ra.

[0080] Referring to Figure 15(b), it can be seen that as the surface roughness Ra of the mold increases, the mold release resistance increases (it becomes more difficult for the mold to be released from the molded product). Note that when the surface roughness Ra of the mold is close to 0, the mold release resistance increases. This is thought to be because when the surface roughness Ra of the mold is close to 0, the mold surface approaches a mirror finish, creating a vacuum between the mold surface and the molded product.

[0081] Here, increasing the groove pitch of the grooves formed in the outer lens 10A is equivalent to decreasing the surface roughness Ra of the mold. Therefore, by increasing the groove pitch of the grooves formed in the outer lens 10A, it is possible to reduce the mold release resistance when the mold 40A is removed from the molded product.

[0082] However, if the groove pitch of the grooves formed in the outer lens 10A is increased, the transmittance of visible light passing through the outer lens 10A changes, which causes a problem in that the outer lens 10A appears to be colored depending on the viewpoint position E (see Figure 16) relative to the outer lens 10A.

[0083] This point will be explained below with reference to the results of a simulation (hereinafter referred to as Simulation 1) conducted by the present inventors.

[0084] Fig. 16 is a diagram showing how light Ray (visible light) is incident on the outer lens 10A at an angle θ (incident angle). Fig. 17(a) is a graph showing the results of Simulation 1 when the angle θ is 10°. Fig. 17(b) is a graph showing the results of Simulation 1 when the angle θ is 20°. Fig. 17(c) is a graph showing the results of Simulation 1 when the angle θ is 30°.

[0085] In Simulation 1, the transmittance of a light ray (visible light) that is incident on the outer lens 10A at an angle θ and passes through the outer lens 10A was simulated, as shown in Fig. 16. All of Simulations 1 to 4 shown below were calculated using COMSOL Multiphysics by COMSOL.

[0086] Specifically, Simulation 1 was performed on three types of outer lenses 10A in which grooves were formed at equal pitches a (=200 nm, 250 nm, 350 nm) with angles θ of 10°, 20°, and 30°. The groove depth, groove width, aspect ratio, groove angle, and convex portion width were all consistent: groove depth D = 200 nm, groove width W2 = 100 nm, aspect ratio D / W2 = 2.0, groove angle θ1 = 90°, and convex portion width W1 = (a - W2) nm. Referring to Figures 17(a) and 17(b), it can be seen that when the first pitch a is 200 nm and the angle θ is 10°, 20°, and 30°, the transmittance of light Ray (overall visible light) is constant (almost constant).

[0087] The inventors produced a prototype outer lens in which grooves with a first pitch a of 200 nm were formed, and examined how actual colors appeared for each angle θ.

[0088] As a result, it was confirmed that when the first pitch a was 200 nm, even if the viewpoint position E (see FIG. 16) relative to the outer lens was changed, color appearance in which the outer lens appears colored did not occur (almost did not occur).

[0089] In contrast, referring to Figures 17(a) to 17(b), when the first pitch a is 250 nm, it can be seen that when the angle θ is 10°, 20°, or 30°, the transmittance of the short wavelength side of light Ray (visible light) relatively decreases.

[0090] The inventors produced a prototype outer lens in which grooves with a first pitch a of 250 nm were formed, and examined how actual colors appeared for each angle θ.

[0091] As a result, it was confirmed that when the first pitch a is 250 nm, changing the viewpoint position E (see FIG. 16) relative to the outer lens causes a color appearance in which the outer lens appears to be colored. It was also confirmed that this color appearance correlates with the transmittance of light Ray (see FIGS. 17(a) to 17(c)). For example, referring to FIG. 17(a), when the first pitch a is 250 nm and the angle θ is 10°, the transmittance of light Ray (visible light) on the short wavelength side decreases. In this case, it was confirmed that when the viewpoint position E (see FIG. 16) is placed in the direction of the angle θ = 10°, light of a wavelength (color) corresponding to the short wavelength side where the transmittance has decreased can be seen.

[0092] This is thought to be because, of the light Ray (visible light) incident on the outer lens 10A from a direction of angle θ, the light that does not pass through the outer lens 10A is reflected or diffracted, and the reflected or diffracted light interferes with each other, causing the outer lens 10A to appear colored. The above is thought to be similarly applicable when the angle θ is 20° or 30°.

[0093] 17(a) and 17(b), when the first pitch a is 350 nm, the transmittance of the short wavelength side of light Ray (visible light) relatively decreases when the angle θ is 10° or 20°. Also, when the first pitch a is 350 nm and the angle θ is 30°, the transmittance of the intermediate wavelength between the short wavelength side and the long wavelength side of light Ray (visible light) relatively decreases.

[0094] The inventors produced a prototype outer lens in which grooves with a first pitch a of 350 nm were formed, and examined how actual colors appeared for each angle θ.

[0095] As a result, when the first pitch a is 350 nm, it was confirmed that changing the viewpoint position E (see FIG. 16) relative to the outer lens causes a color appearance in which the outer lens appears to be colored. It was also confirmed that this color appearance (how the color of the outer lens appears) correlates with the transmittance of light Ray (see FIGS. 17(a) to 17(c)). For example, referring to FIG. 17(a), when the first pitch a is 350 nm and the angle θ is 10°, the transmittance of the short wavelength side of light Ray (visible light) decreases. In this case, it was confirmed that when the viewpoint position E (see FIG. 16) is placed in the direction of the angle θ = 10°, light of a wavelength (color) corresponding to the short wavelength side where the transmittance has decreased can be seen.

[0096] This is thought to be because, of the light Ray (visible light) incident on the outer lens 10A from a direction of angle θ, the light that does not pass through the outer lens 10A is reflected or diffracted, and the reflected or diffracted light interferes with each other, causing the outer lens 10A to appear colored. The above is thought to be similarly applicable when the angle θ is 20° or 30°.

[0097] From the above, the above formula 8, i.e., a≦200 nm, is derived as a condition for suppressing color appearance, in which the outer lens 10A appears to be colored depending on the viewpoint position E (see FIG. 16). Here, a is the pitch of the grooves formed in the first region B1 (see FIG. 14(b)). Taking this into consideration, in embodiment 2, grooves are formed in the first region B1 at a uniform pitch a (see FIG. 14(b)) that satisfies the above formula 8. This makes it possible to suppress color appearance, in which the outer lens 10A (first region B1) appears to be colored depending on the viewpoint position E (see FIG. 16).

[0098] Here, it is also possible to form grooves in the second region B2 at a uniform pitch a (see FIG. 14(b)) that satisfies the above formula 8.

[0099] However, this increases the mold release resistance, which can cause problems such as a force greater than the mold release resistance being applied to the molded product (outer lens 10A) when the mold 40A is removed from the molded product, resulting in deformation of the molded product. Another problem is that it may not be possible to remove the mold 40A from the molded product in the first place.

[0100] As a result of intensive research to solve this problem, the inventors discovered that by forming grooves in the second region B2 at uneven pitches b1, b2 (see Figure 14(c)) rather than at uniform pitches, it is possible to reduce the release resistance and suppress the color appearance in which the outer lens 10A (second region B2) appears colored depending on the viewing position E (see Figure 16).

[0101] This point will be explained below with reference to the results of a simulation conducted by the present inventors (hereinafter referred to as Simulation 2). FIG.

[0102] In simulation 2, as shown in FIG. 16, the transmittance of light Ray (visible light) that is incident on the outer lens 10A at an angle θ (=30°) and passes through the outer lens 10A is simulated.

[0103] Specifically, Simulation 2 was performed on six types of outer lenses 10A in which grooves were formed at non-uniform pitches b1 and b2 (=b1 / b2=240 / 260, b1 / b2=230 / 270, b1 / b2=220 / 280, b1 / b2=210 / 290, b1 / b2=200 / 300, b1 / b2=180 / 320) with an average pitch of 250 nm. For comparison, Simulation 2 was also performed on an outer lens 10A in which grooves were formed at a uniform pitch (b1 / b2=250 / 250). The groove depth, groove width, aspect ratio, groove angle, and convex width are common: groove depth D = 200 nm, groove width W2 = 100 nm, aspect ratio D / W2 = 2.0, groove angle θ1 = 90°, convex width W1a = (b1 - W2) nm, convex width W1b = (b2 - W2) nm, and convex width W1 = (W1a + W1b) / 2. In Figure 18, b1 / b2 = 240 / 260 represents b1 = 240 nm and b2 = 260 nm. The same applies to the others.

[0104] Referring to FIG. 18, it can be seen that as the difference between b1 and b2 increases, the drop in transmittance of light Ray (visible light) on the short wavelength side decreases (color appearance decreases).

[0105] FIG. 19 is a table summarizing the groove pitches and average transmittances shown in FIG.

[0106] In Figure 19, b(max) represents the maximum pitch, b(min) represents the minimum pitch, b(ave) represents the average pitch, (1) 380-480 nm represents the average transmittance in this wavelength range, (2) 500-780 nm represents the average transmittance in this wavelength range, and (1) / (2) represents the value obtained by dividing the average transmittance (380-480 nm) by the average transmittance (500-780 nm). The larger (1) / (2) is, the more effectively color appearance at short wavelengths is reduced.

[0107] Referring to FIG. 19, (1) / (2) of No. 1 is 77.2%, while (1) / (2) of No. 2 is 77.5%, and no significant difference in color appearance reduction is observed between No. 1 and No. 2.

[0108] In contrast, the (1) / (2) ratio for each of Nos. 3 to 7 is 79.1% or higher, showing a significant difference. In particular, for Nos. 6 and 7, the (1) / (2) ratio is 87% or higher, demonstrating a clear improvement in color appearance at short wavelengths.

[0109] From the above, the above formula 9, i.e., {b(max)}-b(min) / b(ave)≧0.16, is derived as a condition for suppressing color appearance in which the outer lens 10A (second region B2) appears tinted depending on the viewpoint position E (see FIG. 16). The 0.16 in this formula 9 is obtained by adopting the value 0.16 of b(max)-b(min) / b(ave) of No. 3 in FIG. 19. In consideration of this, in the second embodiment, grooves are formed in the second region B2 at unequal pitches b1, b2 (see FIG. 14(c)) that satisfy the above formula 9. This makes it possible to suppress color appearance in which the outer lens 10A (second region B2) appears tinted depending on the viewpoint position E (see FIG. 16).

[0110] Next, the results of a simulation (hereinafter referred to as Simulation 3) conducted by the present inventors to verify the above-mentioned Formula 9 will be described with reference to Fig. 20. The results of Simulation 3 are shown in Fig. 20.

[0111] In Simulation 3, as shown in FIG. 16, the transmittance of light Ray (visible light) that is incident on the outer lens 10A at an angle θ (=10°) and passes through the outer lens 10A is simulated.

[0112] Specifically, Simulation 3 was performed on two types of outer lenses 10A in which grooves were formed at uneven pitches b1 and b2 (= b1 / b2 = 300 / 400, b1 / b2 = 200 / 500) with an average pitch of 350 nm. For comparison, Simulation 3 was also performed on an outer lens 10A in which grooves were formed at an even pitch (b1 / b2 = 350 / 350). The groove depth, groove width, aspect ratio, groove angle, and convex portion width were all common: groove depth D = 200 nm, groove width W2 = 100 nm, aspect ratio D / W2 = 2.0, groove angle θ1 = 90°, convex portion width W1a = (b1 - W2) nm, convex portion width W1b = (b2 - W2) nm, and convex portion width W1 = (W1a + W1b) / 2. In addition, in Fig. 20, b1 / b2=300 / 400 indicates that b1=300 nm and b2=400 nm.

[0113] Referring to FIG. 20, it can be seen that as the difference between b1 and b2 increases, the drop in transmittance of light Ray (visible light) on the short wavelength side decreases (color appearance decreases).

[0114] FIG. 21 is a table summarizing the groove pitches and average transmittances shown in FIG.

[0115] In Figure 21, b(max) represents the maximum pitch, b(min) represents the minimum pitch, b(ave) represents the average pitch, (1) 380-540 nm represents the average transmittance in this wavelength range, (2) 560-780 nm represents the average transmittance in this wavelength range, and (1) / (2) represents the value obtained by dividing the average transmittance (380-540 nm) by the average transmittance (560-780 nm). The larger (1) / (2) is, the more effectively color appearance at short wavelengths is reduced.

[0116] Referring to FIG. 21, (1) / (2) for No. 2 is 86.0%, and (1) / (2) for No. 3 is 104.0%, which shows that color appearance at short wavelengths is clearly improved.

[0117] From the above, it can be seen that even when the average pitch is 350 nm, the above formula 9, i.e., {b(max)-b(min)} / b(ave)≧0.16, is an effective condition for suppressing the color appearance in which the outer lens 10A (second region B2) appears colored depending on the viewpoint position E (see Figure 16).

[0118] As described above, when grooves are formed in the first region B1 at an even pitch a (see FIG. 14(b)) that satisfies the above formula 8, and grooves are formed in the second region B2 at unequal pitches b1, b2 (see FIG. 14(c)) that satisfy the above formula 9, by satisfying the above formula 7, i.e., a<(b1+b2) / 2, the mold release resistance can be reduced compared to when a=(b1+b2) / 2. Note that, as shown in FIG. 22, it has been found that the mold release resistance decreases in inverse proportion to the average pitch ((b1+b2) / 2). 22 is a table summarizing the relationship between the mold surface roughness Ra and the assumed demolding resistance ratio when the grooves formed in the outer lens 10A have uneven pitches b1 (=100 nm) and b2 (=100 nm, 150 nm, 200 nm, 250 nm), groove depth D = 200 nm, groove width W2 = 100 nm, aspect ratio D / W2 = 2.0, and groove angle θ1 = 90°. Note that here, b1 is, for example, 100 nm, and b2 is, for example, 100 nm, 150 nm, 200 nm, or 250 nm, but is not limited to these. In other words, b1 and b2 may be any values ​​such that (b1 + b2) / 2 satisfies the values ​​shown in FIG. 22.

[0119] In Figure 22, the assumed demolding resistance ratio is the value obtained by calculating the demolding resistance for each average pitch ((b1 + b2) / 2) and dividing each demolding resistance by the demolding resistance for an average pitch ((b1 + b2) / 2) of 200 nm. The smaller the assumed demolding resistance ratio, the smaller the demolding resistance (the easier it is for the mold to be released from the molded product).

[0120] Next, the results of an anti-fogging effect confirmation test conducted by the present inventors to confirm the anti-fogging properties will be described.

[0121] 23 is a table summarizing the results (anti-fogging properties) of an anti-fogging effect confirmation test conducted on samples S7 to S10 with different groove pitches. The anti-fogging effect confirmation test was the same as the anti-fogging effect confirmation test (steam test) described in the first embodiment above. The specifications of samples S7 to S10 are as follows. Here, the groove pitch a of samples S7 to S10 corresponds to the groove pitch P of samples S1 to S6. <Sample S7> Sample S7 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch (uniform pitch) a = 225 nm, groove depth D = 300 nm, groove width L (W2) = 150 nm, linear convex portion width S (W1) = 75 nm, aspect ratio D / L (W2) = 2, and groove angle θ1 = 90°. <Sample S8> Sample S8 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch (uniform pitch) a = 300 nm, groove depth D = 300 nm, groove width L (W2) = 150 nm, linear convex portion width S (W1) = 150 nm, aspect ratio D / L (W2) = 2, and groove angle θ1 = 90°. <Sample S9> Sample S9 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch (uniform pitch) a = 450 nm, groove depth D = 300 nm, groove width L (W2) = 150 nm, linear convex portion width S (W1) = 300 nm, aspect ratio D / L (W2) = 2, and groove angle θ1 = 90°. <Sample S10> Sample S10 is an acrylic flat plate (60 mm square, 2 mm thick), with a groove pitch (uniform pitch) a = 600 nm, groove depth D = 300 nm, groove width L (W2) = 150 nm, linear convex portion width S (W1) = 450 nm, aspect ratio D / L (W2) = 2, and groove angle θ1 = 90°.

[0122] As a result of the tests using the above samples S7 to S10, it was confirmed that anti-fogging properties (desired anti-fogging effects) were exhibited even when the groove pitch was widened. The "Anti-fogging property ◯" in Figure 23 indicates that anti-fogging properties (desired anti-fogging effects) were exhibited. This is thought to be because the capillary force of the grooves (groove structure) stretches the water droplets in the groove direction and the groove intersection direction, expanding the surface area of ​​the water droplets and promoting evaporation of the water droplets. Furthermore, the desired anti-fogging effects were also obtained by adopting the above formula 2 and formulas 4 to 6.

[0123] Whether or not capillary force is exerted depends on the individual groove shape. Therefore, as long as the groove shape is such that capillary force is exerted (see the above-mentioned embodiment 1), anti-fogging properties are exerted even if the groove pitch is changed on the order of several hundred nanometers.

[0124] The reason for this is thought to be that the size of a water droplet is on the order of several tens of micrometers, so even if the groove pitch is changed on the order of several hundred nanometers, several grooves exist under the water droplet, and capillary forces are exerted.

[0125] The narrower the groove pitch, the more grooves there are under the water droplet, and the greater the capillary force becomes in proportion to the number of grooves. As a result, the narrower the groove pitch, the longer the water droplet becomes. For example, as shown in Figure 23, the water droplet on sample S7 (photograph) is longer than the water droplet on sample S10 (photograph). The "Steam Test Results (Photo)" in Figure 23 is a photograph of samples S7 to S10. In Figure 23, the area above line L represents the processed surface on which the groove structure is formed, and the area below line L represents the base surface (flat surface) on which the groove structure is not formed. Also, in Figure 23, the white circles or ellipses represent water droplets, and the direction in which line L extends represents the direction in which the grooves extend.

[0126] On the other hand, the narrower the groove pitch, the more corners that serve as starting points for water droplet adhesion, and so the water droplet adhesion density tends to increase. For example, as shown in Figure 23, the water droplet adhesion density of sample S7 (photograph) is higher than that of sample S10 (photograph).

[0127] 23 shows an example of a uniform pitch, but whether or not anti-fogging properties are exhibited is considered to be determined by the number of grooves with a shape that allows capillary force to be exerted under water droplets (see embodiment 1 above), regardless of whether the pitch is uniform or uneven. Even in the case of an uneven pitch, it is considered that anti-fogging properties will be exhibited as long as there are grooves with a shape that allows capillary force to be exerted under water droplets (see embodiment 1 above).

[0128] Conversely, if the shape of the groove itself is changed (especially by lowering the aspect ratio) in order to reduce the mold release resistance, the anti-fogging properties are not exhibited. For example, as shown in Figure 5, when the aspect ratio is 1.0 or 1.3, the anti-fogging properties are not exhibited (no anti-fogging effect). In contrast, when the aspect ratio is 2.0, the anti-fogging properties are exhibited (anti-fogging effect).

[0129] As described above, according to the second embodiment, it is possible to suppress color appearance in which the outer lens 30 appears to be colored depending on the viewpoint position E (see FIG. 16).

[0130] This is because the grooves (groove structure) are formed at a pitch such that the transmittance of visible light that enters the area (first area B1, second area B2) on the surface of the outer lens 30 where the grooves are formed and passes through the outer lens 30 within a predetermined angle range (for example, angle θ = 10° to 30°; see Figure 16) is approximately constant (see Figures 17 to 19).

[0131] Furthermore, according to the second embodiment, it is possible to suppress color appearance in which the translucent resin member (first region B1) appears to be colored depending on the viewpoint position E (see FIG. 16). This is due to the use of formula 8.

[0132] Furthermore, according to the second embodiment, it is possible to suppress color appearance in which the translucent resin member (second region B2) appears to be colored depending on the viewpoint position E (see FIG. 16). This is due to the use of formula 9.

[0133] Furthermore, according to the second embodiment, it is possible to reduce the mold release resistance when attempting to remove (at the time of mold release) the molded product (the outer lens 10A that is a light-transmitting resin member).

[0134] This is due to the adoption of formula 7, that is, the average pitch of the grooves formed in the second region B2 being wider than the first pitch of the grooves formed in the first region B1.

[0135] Furthermore, the mold release resistance when the mold is removed from the molded product (translucent resin member) (during demolding) can be reduced, which reduces the probability that the molded product (translucent resin member) will be cracked or deformed during demolding, thereby improving the yield of molded products (translucent resin members).

[0136] Furthermore, according to the second embodiment, it is possible to suppress a decrease in light transmittance due to the groove structure, while achieving the desired anti-fogging effect.

[0137] The use of the above formula 3 makes it possible to suppress the reduction in light transmittance due to the groove structure.

[0138] The desired anti-fogging effect can be achieved by employing the above formulas 1, 2, and 4 to 6.

[0139] Next, a modified example will be described.

[0140] In the above-mentioned second embodiment, an example (see FIG. 14(c)) in which grooves are formed at an uneven pitch (two types of groove pitch) has been described, but this is not limiting. For example, as shown in FIG. 24(a), grooves may be formed at an uneven pitch (three or more types of groove pitch). FIG. 24(a) is an example in which grooves are formed at an uneven pitch (three or more types of groove pitch).

[0141] The following description will be made with reference to the results of a simulation (hereinafter referred to as Simulation 4) conducted by the present inventors to verify the non-uniform pitch (three or more types of groove pitch). Figure 24(b) is a graph summarizing the results of Simulation 4.

[0142] In Simulation 4, as shown in FIG. 16, the transmittance of light Ray (visible light) that is incident on the outer lens 10A at an angle θ (=30°) and passes through the outer lens 10A is simulated.

[0143] Specifically, Simulation 4 was performed on two types of outer lenses 10A in which grooves were formed at non-uniform pitches (b1 / b2 = 200 / 300, b1 / b2 / b3 = 200 / 250 / 300). For comparison, Simulation 4 was also performed on an outer lens 10A in which grooves were formed at a uniform pitch (b1 / b2 = 250 / 250). The groove depth, groove width, aspect ratio, groove angle, and convex portion width were all consistent: groove depth D = 200 nm, groove width W2 = 100 nm, aspect ratio D / W2 = 2.0, groove angle θ1 = 90°, convex portion width W1a = (b1 - W2) nm, convex portion width W1b = (b2 - W2), and convex portion width W2c = (b3 - W3) nm. When b1 / b2 = 200 / 300, the convex width W1 = (W1a + W1b) / 2. On the other hand, when b1 / b2 / b3 = 200 / 250 / 300, the convex width W1 = (W1a + W1b + W1c) / 3. In FIG. 24(b), b1 / b2 / b3 = 200 / 250 / 300 represents b1 = 200 nm, b2 = 250 nm, and b3 = 300. The same applies to the other cases. Referring to FIG. 24(b), it can be seen that when grooves are formed at uneven pitches (three groove pitches: b1 / b2 / b3 = 200 / 250 / 300), the drop in transmittance on the short wavelength side is smaller (color appearance is reduced) than when grooves are formed at uniform pitches (b1 / b2 = 250 / 250).

[0144] In the above-described Embodiment 2, an example in which a groove is formed in the first region B1 has been described, but the present invention is not limited to this. For example, part or all of the grooves in the first region B1 may be omitted. This is because the region (the first region B1) that contributes to the optical characteristics has a high temperature due to the heat from the lamp unit 30 (mainly the light source) and is less likely to become cloudy.

[0145] This also makes it possible to reduce the脱模 resistance when the mold is to be removed from the molded product (the outer lens 10A which is a translucent resin member) (when脱模).

[0146] In the above-described Embodiment 2, the groove pitch of the grooves formed in the first region B1 is the equal pitch a (see FIG. 14(b)), while the groove pitch of the grooves formed in the second region B2 is the unequal pitches b1 and b2 (see FIG. 14(c)). An example in which the formula 7, that is, a <(b1 + b2) / 2 is used as a condition for reducing the脱模 resistance has been described, but the present invention is not limited to this.

[0147] For example, the groove pitch of the grooves formed in the first region B1 is the equal pitch a (see FIG. 14(b)), while the groove pitch of the grooves formed in the second region B2 is also the equal pitch b (not shown). As a condition for reducing the脱模 resistance, instead of the formula 7, a <b may be used.

[0148] Even in this case, it is possible to reduce the脱模 resistance when the mold is to be removed from the molded product (the outer lens 10A which is a translucent resin member) (when脱模).

[0149] All the numerical values shown in the above-described embodiments are merely examples, and it is needless to say that appropriately different numerical values can be used.

[0150] The above-described embodiments are merely illustrative in every respect. The present invention is not to be construed in a limited sense by the description of the above-described embodiments. The present invention can be implemented in various other forms without departing from its spirit or main features.

Description of Reference Numerals

[0151] It should be noted that the term "脱模" is a more literal translation of the original Japanese term which is related to the process of removing a mold from a molded object. In a more common context, it might be better expressed as "demolding" or "ejecting the mold", but following the instruction to translate as-is, this is the rendered text. 10...Translucent resin member, S(S1 to S6)...Sample, 11...Linear convex portion, 12...Linear concave portion, 20...Saline solution, 21...Stainless steel bottle, 22...Hot water bath, 23...Hot water, 24...Steam, 25...Bottom surface, 26...Microscope camera with objective lens

Claims

1. A light-transmitting resin member having a plurality of groove structures formed on at least a part of its surface, the groove structures being composed of a plurality of linear convex portions and a plurality of linear concave portions, the linear protrusions and the linear recesses extend in directions parallel to each other, the grooves, which are the linear recesses, are formed at a pitch such that the transmittance of visible light incident at an incident angle within a predetermined range on the surface in which the grooves are formed and passing through the translucent resin member is approximately constant; The pitch of the light-transmitting resin member is an irregular pitch.

2. When the maximum pitch of the grooves is b (max), the minimum pitch of the grooves is b (min), and the average pitch of the grooves is b (ave), 2. The light-transmitting resin member according to claim 1, wherein {b(max)-b(min)} / b(ave)≧0.

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3. the linear protrusions and the linear recesses extend in directions parallel to each other, the average width W1 of the linear convex portions is 75 nm≦W1≦200 nm; the average width W2 of the linear recessed portion, which is the width of the groove, is 75 nm≦W2≦450 nm; The pitch P between the adjacent grooves is 150 nm≦P≦600 nm. The aspect ratio D / W2 of the depth D of the groove to the width W2 of the groove is 2.0≦D / W2, The angle θ1 of the side wall of the groove with respect to the reference plane is 60°≦θ1≦90°, 3. The light-transmitting resin member according to claim 1, wherein a contact angle θ2 of water with respect to the surface on which the grooves are not formed is 60°≦θ2≦90°.

4. 4. The light-transmitting resin member according to claim 3, wherein a width W1 of the linear convex portion and a width W2 of the linear concave portion are substantially the same.

5. the translucent resin member is a translucent resin member through which light emitted from a light source of a vehicle lamp passes, 5. The light-transmitting resin member according to claim 3, wherein the linear convex portions and the linear concave portions are formed on a rear surface of the light-transmitting resin member.

6. A translucent resin member provided in a lamp that emits light irradiated from a lamp unit, through which the light irradiated from the lamp unit enters and passes, a first region of the surface of the light-transmitting resin member that contributes to the optical characteristics of the lamp unit is formed with a plurality of first groove structures that are each formed with a plurality of linear convex portions and a plurality of linear concave portions extending in directions parallel to each other; a second region of the surface of the light-transmitting resin member that does not contribute to the optical characteristics of the lamp unit is formed with a plurality of second groove structures that are each formed with a plurality of linear convex portions and a plurality of linear concave portions extending in directions parallel to each other; a pitch of the grooves, which are linear recesses of the plurality of first groove structures in the first region, is a uniform pitch, and when the uniform pitch is defined as a, a≦200 nm; The pitch of the grooves, which are linear recesses of the plurality of second groove structures in the second region, is non-uniform.

7. The plurality of second groove structures in the second region are When the maximum pitch of the grooves is b (max), the minimum pitch of the grooves is b (min), and the average pitch of the grooves is b (ave), 7. The light-transmitting resin member for a lamp according to claim 6, wherein {b(max)-b(min)} / b(ave)≧0.

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8. 8. The light-transmitting resin member according to claim 1, wherein the material of the light-transmitting resin member is acrylic or polycarbonate.

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