Foamed resin molded body, translucent signboard, and switch button

Abstract

To provide a foamed resin molded body, a translucent signboard and a switch button capable of obtaining excellent visibility while achieving weight reduction.SOLUTION: The foamed resin molded article 1 includes a molded article body 2 and a thin portion 3 formed in a part of the molded article body and having a thickness smaller than that of the molded article body 2. The thin portion has a relatively small amount of air bubbles or no air bubbles, and thus has a total light transmittance B of 30% or more. Since the molded article body 2 contains a large number of air bubbles 21, the molded article body 2 has a smaller total light transmittance A than the thin portion 3. The difference (B-A) between the total light transmittance B of the thin portion 3 and the total light transmittance A of the molded article body 2 is 5% or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a foamed resin molded body made of a thermoplastic resin, and a light-transmitting signboard and a switch button that use the foamed resin molded body. [Background technology]

[0002] Conventionally, convenience stores, fast food restaurants, pharmacies, general stores, and other businesses often install storefront signs in locations that are easily visible from the road, etc. Generally, storefront signs are made of milky white resin (e.g., acrylic resin) plates. Identification signs, such as the store name, consisting of letters or figures, are printed on raised portions of the milky white plate, and are easily visible even at night by shining light from behind the plate.

[0003] However, identification signs displayed on storefront signboards are usually made easily visible by contrasting their color or shape with the background, which creates the problem of them becoming difficult to see when the distance between the viewer and the storefront signboard increases.

[0004] Furthermore, the resin boards used for storefront signs are relatively heavy, especially for large storefront signs, and this increases the burden on the support parts when they are installed at high places, which has been an issue.

[0005] Japanese Patent Laid-Open Publication No. 8-106254 (Patent Document 1) discloses a laminate for use in three-dimensional signboard letters, etc. The laminate for use in three-dimensional signboard letters, etc., includes a plate-shaped substrate and a synthetic resin mirror provided with the mirror surface in contact with one surface of the plate-shaped substrate. The plate-shaped substrate is made of a light-transmitting synthetic resin foam with a cell size of 0.5 mm to 5.0 mm. As a result, Patent Document 1 provides a laminate for use in three-dimensional signboard letters, etc., that can achieve a more effective three-dimensional effect. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-106254 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present disclosure is to provide a foamed resin molded article that can provide excellent visibility while being lightweight. [Means for solving the problem]

[0008] In order to solve the above problems, the present disclosure provides the following solution. That is, the foamed resin molded body according to the present disclosure comprises a molded body main body and a thin-walled portion formed in at least a part of the molded body main body and having a smaller thickness than the molded body main body. The thin-walled portion has a total luminous transmittance of 30% or more. The molded body main body has a total luminous transmittance that is smaller than that of the thin-walled portion. The difference between the total luminous transmittance of the thin-walled portion and that of the molded body main body is 5% or more.

[0009] The light-transmitting signboard according to the present disclosure is made of the foamed resin molded article described above.

[0010] The switch button according to the present disclosure is made of the foamed resin molded article described above. [Effects of the Invention]

[0011] The foamed resin molded body, light-transmitting signboard, and switch button according to the present disclosure can achieve excellent visibility while being lightweight. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a foamed resin molded article according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the foamed resin molded article shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing a foamed resin molded article according to a modified example. [Figure 4]FIG. 4 is a schematic diagram showing a method for producing the foamed resin molded article shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the state of the thin-walled portion. [Figure 6] FIG. 6 is a cross-sectional view showing a foamed resin molded article according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The inventors of the present invention considered that the visibility of an identification sign portion could be improved by increasing the total light transmittance of the identification sign portion of the in-store sign relative to the total light transmittance of the background portion, rather than by increasing the contrast between the color or shape printed on the in-store sign and the background. In other words, by creating a contrast in total light transmittance between the identification sign portion and the background portion. The inventors first considered using a foamed resin molded body as the material for the in-store sign, from the perspective of reducing the weight of the in-store sign. A foamed resin molded body can be made lighter due to the large number of bubbles that are produced by foam molding, and can also ensure a predetermined strength due to its increased thickness.

[0014] However, foamed resin molded bodies contain many bubbles. When light is irradiated onto the bubbles, diffuse reflection occurs, causing the foamed resin molded body to become cloudy. As a result, the total light transmittance of foamed resin molded bodies is low, and they are generally not suitable for use as storefront signs. The present inventors have considered compressing the thickness of a portion of the foamed resin molded body by press processing in order to use such foamed resin molded bodies as storefront signs. When the thickness of the foamed resin molded body is compressed, the many bubbles are crushed and disappear. Therefore, the total light transmittance can be increased in the compressed portion of the foamed resin molded body, i.e., the thin-walled portion. The present disclosure was completed based on this finding as a result of extensive research by the present inventors. However, Patent Document 1 does not disclose this finding.

[0015] (Configuration 1) A foamed resin molded body according to an embodiment of the present disclosure comprises a molded body main body and a thin-walled portion formed on at least a portion of the molded body main body and having a smaller thickness than the molded body main body. The thin-walled portion has a total luminous transmittance of 30% or more. The molded body main body has a total luminous transmittance that is smaller than that of the thin-walled portion. The difference between the total luminous transmittance of the thin-walled portion and that of the molded body main body is 5% or more.

[0016] This allows for sufficient contrast in total light transmittance between the molded body and the thin-walled portion, thereby providing excellent visibility. Furthermore, since the foamed resin molded body is foam-molded, it can be made lighter.

[0017] (Configuration 2) In the foamed resin molded product of Configuration 1, the density of the thin-walled portion may be greater than the density of the molded body. The molded body has a relatively low density due to foam molding. This allows for a sufficient contrast in total light transmittance between the molded body and the thin-walled portion.

[0018] (Configuration 3) In the foamed resin molded article of Configuration 1 or 2, the thin-walled portion may be formed by providing a recess on one main surface of the molded article body, thereby making it possible to easily manufacture the foamed resin molded article 1.

[0019] (Configuration 4) In the foamed resin molded body of Configuration 3, the thin-walled portion may be formed by further providing a recess on the other main surface of the molded body, thereby making it possible to easily manufacture the foamed resin molded body 1.

[0020] (Configuration 5) The light-transmitting signboard according to the present disclosure is made of a foamed resin molded article according to any one of configurations 1 to 4. This allows for a reduction in weight while still providing excellent visibility.

[0021] (Configuration 6) In the light-transmitting sign of Configuration 5, the molded body may be the sign background. The identification mark of the light-transmitting sign may be displayed on the thin-walled portion. This makes the identification mark easier to identify.

[0022] (Configuration 7) The switch button according to the present disclosure is made of a foamed resin molded article according to any one of configurations 1 to 4. This allows the switch button to be lightweight while also providing excellent visibility.

[0023] The switch button is, for example, an operation button for an air conditioner or audio system in an automobile interior. Such an operation button has an icon displayed on its surface to identify the operation. The switch button of the present disclosure can improve visibility by contrasting the thin-walled portion with the molded body while achieving weight reduction. The icon may be displayed on either the thin-walled portion or the molded body, and the background may be the other of the thin-walled portion or the molded body. However, it may be difficult for a driver to see the operation button in an automobile interior while driving. The switch button has a step between the molded body and the thin-walled portion due to the provision of the thin-walled portion. Therefore, the driver can identify the icon displayed on the switch button and operate the switch button by touching the step with a fingertip or the like without visually recognizing the icon.

[0024] Hereinafter, an embodiment of a foamed resin molded product 1 according to the present disclosure will be specifically described with reference to Figures 1 to 6. Note that the same or corresponding components in the figures are denoted by the same reference numerals, and the same description will not be repeated. Note that, to make the description easier to understand, the drawings referred to below show simplified or schematic configurations, and some components are omitted.

[0025] The foamed resin molded article 1 according to this embodiment has a sheet or plate shape, as shown in Fig. 1. Here, the foamed resin molded article 1 will be described as a storefront signboard.

[0026] The foamed resin molded body 1 is made of a thermoplastic resin. A thermoplastic resin is a resin that softens at its glass transition point and solidifies below its glass transition point. The resin material of the foamed resin molded body 1 is not particularly limited as long as it is a thermoplastic resin, and examples that can be used include polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP). However, it is preferable to use PMMA or PC, which have a high total light transmittance, and it is even more preferable to use PC, which can withstand the heat emitted from an LED light source.

[0027] The resin material may also contain various types of additives to the extent that they do not significantly affect the effects of the present disclosure. The types of additives are not particularly limited, but include, for example, bubble nucleating agents, crystal nucleating agents, lubricants, surfactants, tension modifiers, shrinkage inhibitors, flow modifiers, impact modifiers, fillers, reinforcing agents, antioxidants, heat stabilizers, light stabilizers, UV absorbers, plasticizers, lubricants, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), surface effect additives, infrared absorbers, radiation stabilizers, drip-proofing agents, and antioxidants. The amount of additive added can be selected appropriately as long as it does not impair bubble formation, and the amount used in molding conventional thermoplastic resins can be used. Reinforcing fillers such as glass fiber, carbon fiber, or organic fiber, or inorganic fillers such as talc or calcium carbonate, can also be mixed.

[0028] 1 and 2, the foamed resin molded body 1 has a molded body main body 2 and a thin-walled portion 3 formed in at least a part of the molded body main body 2. In Fig. 2, the dashed dotted line indicates the boundary between the molded body main body 2 and the thin-walled portion 3 (the same applies to Figs. 3 and 5 below).

[0029] The molded body 2 is made of a foamed resin and has a large number of bubbles 21. The molded body 2 has a relatively small total light transmittance due to the large number of bubbles 21. In the present disclosure, the total light transmittance can be measured in accordance with "JIS K 7361-1." Note that, to easily measure the total light transmittance, a portion of the molded body 2 or a thin-walled portion 3 described below may be optionally machined.

[0030] The thin-walled portion 3 is made of a non-foamed resin or a foamed resin. However, even if the thin-walled portion 3 is made of a foamed resin, the thin-walled portion 3 has a density ρB greater than the density ρA of the molded body 2. In other words, the amount of bubbles (average porosity) in the thin-walled portion 3 is less than the amount of bubbles (average porosity) in the molded body 2. As a result, the thin-walled portion 3 has no bubbles or only a small amount of bubbles, resulting in a relatively high total light transmittance. In the present disclosure, "density" can be measured by an underwater displacement method using an automatic hydrometer ("DSG-1" manufactured by Toyo Seiki Co., Ltd.). For example, the molded body 2 and the thin-walled portion 3 are cut into pieces measuring 2 cm long x 2 cm wide and measured at least three times, i.e., three pieces are cut out and measured, and the average values ​​of the three levels can be used as the density ρA of the molded body 2 and the density ρB of the thin-walled portion 3.

[0031] The foamed resin molded body 1 (storefront signboard) can have the molded body main body 2 as the signboard background and an identification sign displayed on the thin-walled portion 3. However, the thin-walled portion 3 may also be used as the signboard background and an identification sign displayed on the molded body main body 2.

[0032] In this way, the foamed resin molded body 1 can be made lighter by constructing the molded body main body 2 from foamed resin. Furthermore, by providing a difference in total light transmittance between the molded body main body 2 (signboard background) and the thin-walled portion 3 (identification sign), the contrast between the molded body main body 2 and the thin-walled portion 3 can be made clearer, improving visibility. Note that in typical storefront signs, the area occupied by the identification sign relative to the entire sign may be smaller than the area of ​​the background. Also, in some cases, the identification sign is more easily visible if it is illuminated. Therefore, to make the identification sign more visible, it is preferable to display the identification sign on the thin-walled portion 3. On the other hand, if the identification sign has a simple structure, the molded body main body 2 can be the identification sign and the thin-walled portion 3 can be the signboard background.

[0033] From the viewpoint of obtaining excellent visibility in the foamed resin molded body 1, the total light transmittance of the thin-walled portion 3 is set to 30% or more, preferably 40% or more, and more preferably greater than 40%. However, if the total light transmittance of the thin-walled portion 3 is too high, it will be dazzling. Therefore, the total light transmittance of the thin-walled portion 3 should be less than 100%, preferably 60% or less, and more preferably less than 50%. In other words, the total light transmittance of the thin-walled portion 3 should be 30% or more and less than 100%, preferably 40% or more and 60% or less, and more preferably greater than 40% and less than 50%.

[0034] Furthermore, the total light transmittance of the molded body 2 is smaller than that of the thin-walled portion 3. From the viewpoint of obtaining excellent visibility, the difference (BA) between the total light transmittance A of the molded body 2 and the total light transmittance B of the thin-walled portion 3 is preferably 5% or more. The difference (BA) is preferably 10% or more, more preferably greater than 30%, and less than 70%, preferably less than 40%. In other words, the difference (BA) is preferably 5% or more, preferably 5% or more but less than 70%, more preferably 10% or more but less than 70%, and even more preferably greater than 30% but less than 40%. Note that in the present disclosure, the difference (%) in total light transmittance does not indicate the percentage of total light transmittance, but simply indicates a numerical difference. For example, if the total light transmittance A is 20% and the total light transmittance B is 45%, the difference (BA) in total light transmittance is 25%, which is calculated by subtracting 20 from 45.

[0035] Furthermore, from the viewpoint of obtaining excellent visibility, the ratio (ρA / ρB) of the density ρA of the molded body 2 to the density ρB of the thin-walled portion 3 is 0.3 or more, preferably 0.6 or more, more preferably 0.74 or more, and 0.9 or less, preferably 0.77 or less. In other words, the ratio (ρA / ρB) is 0.3 to 0.9, preferably 0.6 to 0.9, more preferably 0.74 to 0.77.

[0036] The thin-walled portion 3 has a thickness smaller than that of the molded body main body 2. As shown in FIG. 2, the thin-walled portion 3 is formed by providing a recess 4 on one main surface of the molded body main body 2. As shown in FIGS. 1 and 2, the side surface of the recess 4 may be a vertical surface extending perpendicular to one main surface of the molded body main body 2 or the bottom surface of the recess 4, an inclined surface extending in an inclined direction, or a convex curved surface convex toward the inside of the recess 4. In other words, the shape of the recess 4 is not particularly limited as long as it can form the thin-walled portion 3. The thicknesses of the molded body main body 2 and the thin-walled portion 3 can be measured using a vernier caliper, a micrometer, or the like. However, the method for measuring the thicknesses of the molded body main body 2 and the thin-walled portion 3 is not limited thereto.

[0037] Furthermore, when the light source is located on the other main surface opposite to the recess 4, if the recess 4 has an inclined or convex curved surface such that the width between both side surfaces widens from the bottom surface of the recess 4 toward the opening (see the recess 4 in the center and the recess 4 on the right side in FIG. 2), the light that has passed through the thin-walled portion 3 can be made to spread in the traveling direction. On the other hand, by making the side surfaces of the recess 4 vertical or close to vertical, the light that has passed through the thin-walled portion 3 can be made to travel straight without spreading in the traveling direction, making it easier to see from a distance.

[0038] Furthermore, the shape of the bottom surface of the recess 4 can be formed as a convex curved surface that is convex toward the opening of the recess 4 or a concave curved surface that is concave toward the other main surface of the molded body 2. This allows the light that has passed through the thin-walled portion 3 to travel in a diverging or narrowing direction depending on the purpose of the signboard.

[0039] As shown in FIG. 3 , the thin-walled portion 3 may be formed by providing a recess 4 on the other main surface of the molded body body 2. In this case, the thin-walled portion 3 formed by providing a recess 4 on the other main surface of the molded body body 2 may not overlap with the thin-walled portion 3 formed by providing a recess 4 on one main surface of the molded body body 2 in a plan view, i.e., when viewed from the direction of one main surface of the molded body body 2; that is, they may be separated by a predetermined distance. However, the thin-walled portion 3 formed by providing a recess 4 on one main surface of the molded body body 2 and the thin-walled portion 3 formed by providing a recess 4 on the other main surface of the molded body body 2 may overlap in a plan view. In other words, the thin-walled portion 3 may be formed between the recess 4 provided on one main surface of the molded body body 2 and the recess 4 provided on the other main surface of the molded body body.

[0040] The difference in thickness between the molded body 2 and the thin-walled portion 3 and the difference in total light transmittance described above can be attributed to the method for manufacturing the foamed resin molded body 1. Hereinafter, the method for manufacturing the foamed resin molded body 1 will be described with reference to FIG.

[0041] First, a molded body 2 (with the thin-walled portion 3 unformed) made of a foamed resin is prepared. The molded body 2 can be foam-molded by injection molding, extrusion molding, or the like. The foaming agent used in foam molding may be either a chemical foaming agent or a physical foaming agent. However, chemical foaming agents may reduce the total light transmittance of the thin-walled portion 3 due to bubbles or decomposition products that are generated when the agent is decomposed during hot pressing, as described below. Therefore, it is preferable that the foaming agent be a physical foaming agent, which has little effect on the total light transmittance of the thin-walled portion 3.

[0042] Next, the molded body 2 is placed on the lower mold 51 .

[0043] Finally, the upper die 52, on which protrusions corresponding to the recesses 4 are formed, is lowered toward the compact body 2, and the protrusions pressurize a portion of the main surface of the compact body 2 by hot pressing or the like. This forms the recesses 4 on a portion of the main surface of the compact body 2, and also forms the thin-walled portion 3 (see FIG. 2).

[0044] At this time, a portion of the molded body 2 is compressed by the upper mold 52. As a result, the thickness of the thin-walled portion 3 becomes smaller than the thickness of the molded body 2. Furthermore, during compression, air bubbles contained in the portion of the molded body 2 are crushed and eliminated, or the amount of air bubbles decreases. As a result, the density of the thin-walled portion 3 becomes larger than the density of the molded body 2, and the total light transmittance B of the thin-walled portion 3 can be made larger than the total light transmittance A of the molded body 2.

[0045] According to this method for producing a foamed resin molded body 1, it is possible to easily produce a foamed resin molded body 1 having a molded body 2 and a thin-walled portion 3 with different total light transmittances by compressing a portion of the molded body 2. Note that, in order to facilitate removal of the upper mold 52 from the molded body 2 after pressure is applied by the upper mold 52, it is preferable that the width of the opening of the recess 4 is greater than the width of the bottom surface of the recess 4, and that the widths of both side surfaces of the recess 4 gradually increase from the bottom surface toward the opening (see the recess 4 on the right side and the recess 4 in the center of FIG. 2).

[0046] The density and total light transmittance of the thin-walled portion 3 can be varied by changing the amount of compression of the molded body 2. As shown in FIG. 5, the depth of the recess 4, i.e., the amount of compression of the molded body 2, is greater in the thin-walled portion 3 on the right side of the figure than in the thin-walled portion 3 on the left side of the figure. In this case, more air bubbles are likely to be crushed and eliminated in the thin-walled portion 3 on the right side of the figure than in the thin-walled portion 3 on the left side of the figure. In this way, by increasing the amount of compression in the thin-walled portion 3, the total light transmittance of the thin-walled portion 3 can be increased, and by decreasing the amount of compression in the thin-walled portion 3, the total light transmittance of the thin-walled portion 3 can be decreased. In other words, the total light transmittance of the thin-walled portion 3 can be adjusted by changing the amount of compression in the thin-walled portion 3.

[0047] In this case, a plurality of thin-walled portions 3 each having a different total light transmittance can be formed in the foamed resin molded body 1. Alternatively, by adjusting the amount of compression in part of one thin-walled portion 3, i.e., by providing a step on the bottom surface of the recess 4, it is possible to form portions with different total light transmittance. Also, by sloping the lower surface of the convex portion of the upper mold 52 in Figure 4, it is possible to make the bottom surface of the recess 4 in one thin-walled portion 3 an inclined surface, thereby imparting a gradation in the total light transmittance in the thin-walled portion 3. This makes it possible to adjust the visibility of the sign and design a sign that better emphasizes the information to be conveyed.

[0048] As shown in Fig. 6, the foamed resin molded article 1 may have a corrugated shape. The foamed resin molded article 1 may be curved, processed into a corrugated shape, or formed into various shapes depending on the application, such as a storefront sign or a switch button. The foamed resin molded article 1 can be used not only as a storefront sign, but also as a switch button (an operation button for an air conditioner or audio in an automobile interior), an overhead console, a railway interior material, etc.

[0049] As described above, there is a difference in thickness between the molded body main body 2 and the thin-walled portion 3. In some cases, the identification mark displayed on the foamed resin molded body 1 can be identified by touching it with a fingertip or the like. For example, this is a switch button for operating an air conditioner or audio system in the interior of an automobile. A step is formed due to the difference in thickness between the molded body main body 2 and the thin-walled portion 3. The operator of the switch button can not only identify the identification mark (an icon in the case of a switch button in the interior of an automobile) by the difference in total light transmittance described above, but can also identify the step between the molded body main body 2 and the thin-walled portion 3 by touching it with a fingertip or the like.

[0050] The foamed resin molded body 1 can reduce the amount of resin used by foam molding. As a result, the foamed resin molded body 1 according to this embodiment can contribute to improving resource utilization efficiency, easing transportation burdens, reducing energy consumption, and reducing CO2 emissions. By providing the foamed resin molded body 1 to society, it is possible to contribute to achieving Goal 7 (Affordable and Clean Energy), Goal 9 (Industry, Innovation and Infrastructure), and Goal 11 (Sustainable Cities and Communities) of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0051] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Example]

[0052] As shown in Table 1 below, test pieces (foamed resin molded bodies) of Examples 1 to 5 and Comparative Examples 1 to 3 were prepared, and the visibility of the recess forming the thin-walled portion and the sign visibility (visibility based on the contrast of total light transmittance) of each test piece were evaluated.

[0053] [Table 1]

[0054] Each test piece was formed into a rectangle with a length of 300 mm in the hand direction and 500 mm in the longitudinal direction in plan view, and a thin-walled portion with a circular shape in plan view was formed at the diagonal center of the rectangle so that the centers of the thin-walled portions overlapped. For each test piece, the thicknesses t1 and t2 of the test piece (main body of the molded body) and the thin-walled portions, the total light transmittances A and B, and the densities ρA and ρB are as shown in Table 1.

[0055] Each test piece was prepared as follows. First, a molded body (thin-walled portion unformed) was prepared by extrusion foam molding using colorless polycarbonate ("L1225-L" manufactured by Teijin Limited) as the resin material. More specifically, the resin material was fed into the extruder at a screw rotation speed of 50 rpm and melt-kneaded. A foaming agent (nitrogen) was then injected through a vent hole at an arbitrary gas pressure to achieve a density ρA (total light transmittance A) as shown in Table 1, and the resin material and nitrogen were melt-kneaded. The molten resin was then extruded into a coat hanger die while gradually cooling, and a sheet-like molded body was taken up by a cooling roll so that the thickness of the molded body was 5 mm.

[0056] Next, the compact body was placed on a lower die set at 180°C, and an upper die with a circular protrusion was lowered from above and pressed for 90 seconds to form a thin-walled portion. Spacers (iron blocks) were placed around the compact body to adjust the thickness of the thin-walled portion of each test piece so that the thickness of the thin-walled portion would meet the conditions in Table 1.

[0057] In the present examples, the evaluation methods for each test piece are as follows.

[0058] (Signboard visibility) A light source was installed on the recessed side that formed the thin-walled portion of each test piece, and light was shone toward the thin-walled portion. An LED bulb (Panasonic Corporation's "Paluk LDA7DDGSZ6F") was used as the light source, and the LED bulb was installed so that the top of the LED bulb was facing the thin-walled portion and the distance between the LED bulb and the thin-walled portion was 5 cm. The sign visibility was confirmed visually from a distance of 10 m on the opposite side of each test piece from the side where the light source was installed. An "A" was assigned if the circular shape of the thin-walled portion was clearly visible, a "B" was assigned if the outline of the circular shape of the thin-walled portion was slightly blurred but still visible, a "C" was assigned if the circular shape of the thin-walled portion was clearly visible but was dazzling, and a "D" was assigned if the circular shape of the thin-walled portion was not visible.

[0059] (recess visibility) Furthermore, when the recesses forming the thin-walled portion were visually observed from a distance of 10 m from each test piece, they were rated as "A," and when they were not, they were rated as "D." If the recesses are visible, it is considered that the step between the molded body and the thin-walled portion can be sufficiently identified when touched with a fingertip or the like.

[0060] In Example 1, the difference between the thicknesses t1 and t2 was large, and the recesses were clearly visible. However, the total light transmittance B of the thin-walled portion was relatively high at 80%, and the difference between the total light transmittance A of the molded body and the total light transmittance B of the thin-walled portion was relatively high at 70%, which made the signboard visibility too bright, resulting in a rating of "C."

[0061] In Examples 2 to 5, the total light transmittance B of the thin-walled portion was 30% to 50%, and the difference between the total light transmittance A of the molded body and the total light transmittance B of the thin-walled portion was 20% to 40%. In Examples 2 to 5, the total light transmittance A of the molded body and the total light transmittance B of the thin-walled portion could be set in a well-balanced manner, so the recesses were sufficiently visible and the sign visibility was rated "B".

[0062] In Comparative Example 1, there was no difference between the thicknesses t1 and t2 and the total light transmittances A and B, and the recess visibility and signboard visibility were both rated "D."

[0063] In Comparative Example 2, the difference between thicknesses t1 and t2 was small, and the total light transmittance B of the thin-walled portion was relatively large at 34%, but the difference between the total light transmittance A of the molded body and the total light transmittance B of the thin-walled portion was relatively small at 4%. Therefore, the recess visibility and sign visibility were both rated "D".

[0064] In Comparative Example 3, the difference between the thicknesses t1 and t2 was small, the total light transmittance B of the thin-walled portion was relatively small at 29%, and the difference between the total light transmittance A of the molded body and the total light transmittance B of the thin-walled portion was also relatively small at 4%. Therefore, the recess visibility and sign visibility were both rated "D".

[0065] In addition, in Comparative Example 3, even when the total light transmittance A of the molded body body was set to 20% and the difference between the total light transmittance A of the molded body body and the total light transmittance B of the thin-walled portion was set to 9%, which is 5% or more, the visibility of the recessed portion was slightly improved compared to Comparative Example 2, but the total light transmittance B of the thin-walled portion was relatively small at 29%, so it is presumed that the sign visibility was rated "D".

[0066] From the above, it was confirmed that in order to obtain excellent visibility in a foamed resin molded body, it is necessary to make the total light transmittance B of at least the thin-walled portion 30% or more, and to make the difference (BA) between the total light transmittance A of the molded body itself and the total light transmittance B of the thin-walled portion 5% or more.

[0067] Furthermore, by comparing Examples 1 to 5, it was confirmed that in order to obtain better visibility in the foamed resin molded product, the total light transmittance B of the thin-walled portion should be 40% or more and 60% or less, and more preferably more than 40% and less than 50%. It was also confirmed that the difference (BA) between the total light transmittance A of the molded product body and the total light transmittance B of the thin-walled portion should be 10% or more and less than 70%, and more preferably more than 30% and less than 40%. [Explanation of symbols]

[0068] 1 foamed resin molded body, 2 molded body main body, 21 air bubbles, 3 thin-walled portion, 4 recess, 51 lower mold, 52 upper mold

Claims

1. A foamed resin molded body made of a thermoplastic resin, a molded body; a thin-walled portion formed in at least a part of the molded body body and having a thickness smaller than that of the molded body body; the thin-walled portion has a total light transmittance of 30% or more, the molded body has a total light transmittance that is smaller than the total light transmittance of the thin-walled portion, A foamed resin molded body, wherein the difference between the total light transmittance of the thin-walled portion and the total light transmittance of the molded body is 5% or more.

2. The foamed resin molded article according to claim 1, A foamed resin molded body, wherein the density of the thin-walled portion is greater than the density of the molded body main body.

3. The foamed resin molded article according to claim 1, The foamed resin molded body, wherein the thin-walled portion is formed by providing a recess on one main surface of the molded body.

4. The foamed resin molded article according to claim 3, The foam resin molded body, wherein the thin-walled portion is further formed by providing a recess on the other main surface of the molded body.

5. A light-transmitting signboard comprising the foamed resin molded article according to any one of claims 1 to 4.

6. The light-transmitting signboard according to claim 5, The molded body is a signboard background, The identification mark of the light-transmitting signboard is displayed on the thin portion.

7. A switch button comprising the foamed resin molded article according to any one of claims 1 to 4.

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