Light transmission direction control sheet and method for manufacturing same

Abstract

Provided are a light transmission direction control sheet in which an air layer can be excluded without injecting an adhesive into a gap, and a method for manufacturing the same.　The light transmission direction control sheet 1 comprises first and second light transmissive resin films 2, 2A facing each other, and a pair of louver layers 3, 3A interposed between the first and second light transmissive resin films 2, 2A and bonded with an adhesive 6, the light transmission direction control sheet 1 being used in a module device 10 to control the optical path of a light beam, and the pair of louver layers 3, 3A being butted and closely contacted with each other without a gap. Since an air layer between the pair of louver layers 3, 3A is eliminated, irregular reflection of the light beam can be prevented. Therefore, an optical sensor 14 of the module device 10 does not malfunction or produce false detection. In addition, since it is not necessary to fill the air layer by injecting a filling adhesive into the gap, it is possible to eliminate the possibility of a part of the air layer remaining or the light transmission direction control sheet 1 being contaminated by the filling adhesive.

Description

Light transmission direction control sheet and manufacturing method thereof

[0001] The present invention relates to a light transmission direction control sheet used in various detection devices, image display devices for automobiles, etc. to control the light path and the visible angle, and to a method for manufacturing the same.

[0002] Conventionally, when light transmission direction control sheets 20 and 20A are used in a module device 10, as shown in Figures 8 and 9, the light transmission direction control sheets 20 and 20A are placed opposite the light source 13 for emitting light and the light sensor 14 for receiving light of the module device 10, respectively, and the optical path of the light beam is controlled by this pair of light transmission direction control sheets 20 and 20A (see Patent Document 1).

[0003] The module device 10 includes a flat rectangular housing 11, a pair of mounting holes 12 drilled at a distance in the longitudinal direction of the surface of the housing 11, and a light source 13 is fitted into one of the pair of mounting holes 12, and this light source 13 lights up and irradiates a light beam as shown by the arrow in Fig. 8. On the other hand, an optical sensor 14 is fitted into the other mounting hole 12, and this optical sensor 14 detects the light beam that has passed from the light source 13 and passed through the pair of light transmission direction control sheets 20, 20A.

[0004] The pair of light transmission direction control sheets 20, 20A includes a light transmission direction control sheet 20 installed on the surface of the housing 11 facing the light source 13, and a light transmission direction control sheet 20A installed on the surface of the housing 11 facing the light sensor 14, each formed as a planar rectangular sheet, and functions to transmit light rays emitted from the light source 13 to the light sensor 14. The pair of light transmission direction control sheets 20, 20A are arranged horizontally in a row and adjacent to each other, with the adjacent peripheral surfaces facing each other with a gap G between them. Of the pair of light transmission direction control sheets 20, 20A, the light transmission direction control sheet 20A facing the light sensor 14 is rotated 90° and oriented in a direction different from the orientation of the light transmission direction control sheet 20 facing the light source 13, from the standpoint of directivity, as shown in FIG.

[0005] JP 2017-146359 A

[0006] A pair of conventional light transmission direction control sheets 20, 20A are configured as described above, and the adjacent peripheral surfaces face each other with a gap G therebetween, which creates an air layer A that diffuses light rays, resulting in the problem of malfunction or false detection by the optical sensor 14. As a means for solving this problem, a method has been proposed in which a silicone-based or acrylic-based filling adhesive 21 is injected into the gap G between the peripheral surfaces of the pair of light transmission direction control sheets 20, 20A to fill the air layer A, as shown in Figure 10.

[0007] However, in practice, it is not easy to install a pair of light transmission direction control sheets 20 and 20A and then properly inject the filling adhesive 21 into the gap G to completely fill the air layer A. For example, if the amount of filling adhesive 21 injected is insufficient, part of the air layer A will remain, and if the amount of filling adhesive 21 injected is excessive, contamination may occur near the opposing peripheral surfaces of the light transmission direction control sheets 20 and 20A.

[0008] The present invention has been made in view of the above, and aims to provide a light transmission direction control sheet that can eliminate air layers without injecting adhesive into gaps, and a method for manufacturing the same.

[0009] In order to solve the above problems, the present invention is characterized by including opposing first and second light-transmitting resin films and a plurality of louver layers interposed between the first and second light-transmitting resin films and bonded with an adhesive, and the plurality of louver layers are butted together and in close contact.

[0010] Each louver layer is formed by alternating multiple light-transmitting bands and light-shielding bands, with each light-transmitting band being formed from light-transmitting silicone rubber and each light-shielding band being formed from colored silicone rubber, and it is preferable that the hardness of these silicone rubbers be 73 or more and 83 or less when measured with a Type A durometer in accordance with JIS K6253.

[0011] Furthermore, it is preferable that the silicone rubber of each louver layer has a tensile strength of 7.5 MPa or more and 13.5 MPa or less when measured in accordance with JIS K6251, an elongation at break of 270% or more and 490% or less when measured in accordance with JIS K6251, and a tear strength of 8 kN / m or more and 28 kN / m or less when measured in accordance with JIS K6252.

[0012] The adhesive is preferably an adhesive silicone rubber, and has a hardness after curing of 10 to 60 when measured with a Type A durometer in accordance with JIS K6253. The adhesive can be attached to a module device to cover the light source and light sensor of the module device. The arrangement direction of the light transmission bands and light blocking bands of the louver layer facing the light source can be approximately perpendicular to the arrangement direction of the multiple louver layers, and the arrangement direction of the light transmission bands and light blocking bands of the louver layer facing the light sensor can be approximately aligned with the arrangement direction of the multiple louver layers.

[0013] In order to solve the above problems, the present invention provides a method for manufacturing a light transmission direction control sheet as set forth in claim 1 or 2, characterized in that a plurality of elastic louver layers, each having light-transmitting zones and light-shielding zones arranged alternately, are adhered to a first light-transmitting resin film with an adhesive, and the plurality of louver layers are butted together and brought into close contact, a second light-transmitting resin film is adhered to the plurality of louver layers with an adhesive, and the adhesive is heated and cured.

[0014] In addition, among the multiple louver layers, recesses can be formed on the butting peripheral edges of some of the louver layers, and protrusions can be formed on the butting peripheral edges of the remaining louver layers, and the multiple louver layers can be butted together while these recesses and protrusions fit together.

[0015] Here, the multiple louver layers in the claims may be formed to the same size or different sizes using a specified resin or elastomer. The number of louver layers is not particularly limited and can be two, three, four, five, six, etc. Some of the multiple louver layers can be crossed with their orientations changed. The physical properties of the silicone rubber of the louver layers include approximate values ​​as long as there is no difference in the operational effect. Furthermore, the recesses and protrusions may each be singular, or multiple of each can be formed. Furthermore, the up / down, front / back, left / right directions of the light transmission direction control sheet according to the present invention are directions based on the drawings and can be appropriately changed as needed.

[0016] According to the present invention, the multiple louver layers are not arranged with gaps between them but are butted together closely, so that there are no gaps between the multiple louver layers and air layers between the multiple louver layers can be eliminated.

[0017] According to the present invention, since a plurality of louver layers are butted together and tightly attached without gaps, there is an effect that air gaps can be eliminated without filling the gaps with adhesive.

[0018] According to the invention of claim 2, the louver layer is formed from silicone rubber so that it can be elastically deformed, which not only improves adhesion but also improves the heat resistance, cold resistance, moisture resistance, environmental resistance, flexibility, colorability, transparency, etc. The silicone rubber forming the louver layer has a hardness of 73 or more and 83 or less when measured with a Type A durometer in accordance with JIS K6253, which prevents warping and deformation of the louver layer, and by preventing this warping and deformation, it is possible to prevent the formation of air gaps between multiple louver layers.

[0019] According to the invention of claim 3, by limiting the tensile strength, elongation at break, and tear strength of the silicone rubber of the louver layer, it is expected that warping and deformation of the light transmission direction control sheet can be prevented. Furthermore, by preventing warping and deformation, it is possible to prevent air layers from forming between the multiple louver layers.

[0020] According to the invention of claim 4, the adhesive is adhesive silicone rubber, which improves adhesion between the louver layer and the silicone rubber. Furthermore, the hardness of the adhesive after curing is 10 to 60 when measured with a Type A durometer in accordance with JIS K6253, which prevents warping and deformation of the louver layer and also prevents air gaps from forming between multiple louver layers.

[0021] According to the fifth aspect of the present invention, the use of the light transmission direction control sheet makes it possible to appropriately transmit the light beam emitted from the light source to the light sensor.

[0022] According to the invention described in claim 6, multiple louver layers can be adhered to the first light-transmitting resin film, and these multiple louver layers can be butted together while being manually adjusted over a long period of time, thereby reducing the occurrence of gaps between the multiple louver layers.

[0023] According to the invention described in claim 7, multiple louver layers are positioned by fitting the recesses and protrusions together, and misalignment of the louver layers is regulated, thereby making it possible to prevent the louver layers from misaligning and generating air bubbles due to differences in the thermal expansion coefficients of the first and second light-transmitting resin films and the louver layers.

[0024] 1 is an explanatory diagram schematically showing a state in which a light transmission direction control sheet is set in and used on a module device in an embodiment of the light transmission direction control sheet according to the present invention. FIG. 1 is an explanatory plan view schematically showing a state in which a light transmission direction control sheet is set in and used on a module device in an embodiment of the light transmission direction control sheet according to the present invention. FIG. 2 is an explanatory plan view schematically showing a state in which an adhesive silicone rubber is applied to a first light-transmitting resin film in an embodiment of the method for manufacturing a light transmission direction control sheet according to the present invention. FIG. 3 is an explanatory plan view schematically showing a state in which a pair of louver layers are laminated and bonded to the adhesive silicone rubber applied to the first light-transmitting resin film in an embodiment of the method for manufacturing a light transmission direction control sheet according to the present invention. FIG. 4 is an explanatory plan view schematically showing a state in which a second light-transmitting resin film is laminated and bonded to a pair of louver layers in an embodiment of the method for manufacturing a light transmission direction control sheet according to the present invention. FIG. 5 is an explanatory plan view schematically showing a state in which excess portions of the first and second light-transmitting resin films have been removed along the peripheral edges of the pair of louver layers in an embodiment of the method for manufacturing a light transmission direction control sheet according to the present invention. FIG. 6 is an explanatory plan view schematically showing a second embodiment of the method for manufacturing a light transmission direction control sheet according to the present invention. 1 is a plan view of a module device in which a pair of light transmission direction control sheets are installed and used; FIG. 2 is a plan view of a module device in which a pair of light transmission direction control sheets are installed and used; and FIG. 3 is a diagram illustrating a method of filling an air layer by injecting a filling adhesive into a gap between peripheral surfaces of a pair of light transmission direction control sheets.

[0025] A preferred embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 6 , the light transmission direction control sheet 1 in this embodiment has a multilayer structure including first and second light-transmitting resin films 2, 2A facing each other and a pair of louver layers 3, 3A interposed between the first and second light-transmitting resin films 2, 2A and bonded with an adhesive 6, and is a control sheet used in a module device 10 to control the optical path of light rays. By forming the pair of louver layers 3, 3A from a predetermined elastic elastomer and bringing them into close contact, this sheet contributes to the achievement of Goal 9 of the SDGs (the United Nations' international goals for sustainable development, consisting of 17 global goals and 169 targets (achievement criteria)) adopted at the United Nations Summit.

[0026] 1 and 2, the light transmission direction control sheet 1 is formed into a rectangular shape, such as a flat rectangle or a square, and is placed on the surface of the module device 10 to cover the light source 13 for emitting light and the light sensor 14 for receiving light of the module device 10. At least a portion of the periphery of this light transmission direction control sheet 1 may be curved, or at least one of the four corners may be chamfered.

[0027] 1 and 2, the module device 10 has a housing 11 that is rectangular in plan view, and a pair of mounting holes 12 are drilled in a horizontal row at intervals along the longitudinal direction of the surface of the housing 11. A light source 13 such as an LED is fitted into one of the pair of mounting holes 12, and this light source 13 lights up and irradiates a light beam. On the other hand, an optical sensor 14 is fitted into the other mounting hole 12, and this optical sensor 14 detects the light beam that has passed through the light transmission direction control sheet 1 from the light source 13.

[0028] 1 to 5, the first and second light-transmitting resin films 2 and 2A are made of, for example, a polycarbonate resin film or the like that has excellent heat resistance of 90°C or higher, weather resistance, impact resistance, dimensional accuracy, and transparency, and is resistant to warping and deformation, and are formed to a size larger than the pair of closely spaced louver layers 3 and 3A before manufacturing the light transmission direction control sheet 1, and function to sandwich the pair of louver layers 3 and 3A and prevent air from entering. The thickness of the first and second light-transmitting resin films 2 and 2A is set to 0.1 mm or more and 0.3 mm or less, preferably 0.189 mm or more and 0.2 mm or less, more preferably 0.195 mm or more and 0.2 mm or less, and even more preferably around 0.2 mm, from the viewpoints of reducing the installation space and ensuring rigidity to prevent warping.

[0029] In order to obtain excellent transparency, the light transmittance when light is incident only on the first and second light-transmitting resin films 2 and 2A is preferably 75% or more, preferably 75% to 100%, and more preferably 85% to 100%. Furthermore, the polycarbonate resin film used for the first and second light-transmitting resin films 2 and 2A preferably has a flexural modulus of 91 MPa to 2300 MPa when measured in accordance with the measurement test method of ISO 178.

[0030] 1 and 2, the pair of louver layers 3, 3A are provided with a louver layer 3 facing the light source 13 of the module device 10 from above and a louver layer 3A facing the light sensor 14 of the module device 10 from above, in a horizontal row, with the opposing surfaces butted together and in close contact with no gaps, transmitting the light beam emitted from the light source 13 to the light sensor 14 and functioning to eliminate the conventional air layer A. Of this pair of louver layers 3, 3A, the louver layer 3A facing the light sensor 14 is rotated 90 degrees and oriented in a direction perpendicular to the orientation of the louver layer 3 facing the light source 13, from the perspective of guiding the light beam to the light sensor 14.

[0031] Each louver layer 3 / 3A is formed into a rectangular shape, e.g., 15 inches, by alternately arranging a plurality of light-transmitting zones 4 and light-shielding zones 5 in a horizontal row. From the viewpoints of adjusting the directivity of light rays passing through the light transmission direction control sheet 1 in any direction and facilitating manufacturing, the thickness of each louver layer 3 / 3A is preferably 100 μm to 5000 μm, more preferably 500 μm to 3500 μm, more preferably 600 μm to 2000 μm, and even more preferably approximately 1200 μm. The thickness of the louver layer 3 / 3A is made constant, but this constantness includes a range of ±5% of the design value in the thickness direction. The thickness of this louver layer 3 / 3A can be determined by measuring a cross-sectional photograph of the louver layer 3 / 3A alone, and the average value of measurements taken at 10 or more locations is preferably used.

[0032] In order to improve adhesion, the louver layers 3 and 3A have each light-transmitting band 4 formed in a strip shape from light-transmitting silicone rubber that has excellent heat resistance of 90°C or more, cold resistance, moisture resistance, environmental resistance, flexibility, colorability, transparency, etc., and that helps prevent warping and deformation, and each shading band 5 formed in a strip shape from transparent silicone rubber that has been colored to block light, and these light-transmitting bands 4 and shading bands 5 are formed at the same height, making the front and back symmetrical.

[0033] As silicone rubber, for example, the silicone rubber composition generally called millable rubber, which is made up of diorganopolysiloxane whose molecular chain end is blocked with hydroxysilyl group or vinylsilyl group and organic peroxide; the so-called addition reaction type organosilicone rubber composition, which is made up of diorganopolysiloxane having at least two vinyl groups bonded to silicon atom in the molecule, organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atom (i.e., SiH bond) in the molecule and platinum catalyst.The specific example of silicone rubber is KE-153U (product name manufactured by Shin-Etsu Chemical Co., Ltd.) etc.

[0034] The silicone rubber has a density of 1.21 g / cm when measured at 23°C in accordance with JIS K6268. 3 1.25g / cm or more 3or less, preferably 1.24 g / cm 3 Furthermore, from the viewpoint of preventing warping and deformation of the louver layers 3 and 3A, the hardness measured with a rubber / plastic hardness tester (type A durometer) in accordance with JIS K6253 is optimally 73 to 83, preferably 78 to 79. Furthermore, from the viewpoint of preventing warping and deformation, the tensile strength measured in accordance with JIS K6251 is optimally 7.5 MPa to 13.5 MPa, preferably around 10.5 MPa.

[0035] The silicone rubber preferably has an elongation at break of 270% to 490%, preferably 310% to 380%, as measured in accordance with JIS K6251. To prevent warping and deformation, the tear strength (crescent type) is preferably 8 kN / m to 28 kN / m, preferably 13 kN / m to 18 kN / m, as measured in accordance with JIS K6252. These measurements can be performed using measuring instruments and testing machines from M&K Corporation, ITS Japan Co., Ltd., etc.

[0036] The installation angles of the light transmission band 4 and the light blocking band 5 are each adjusted to between 0° and 1°. Each light transmission band 4 is formed from transparent silicone rubber with a vertically long rectangular cross section and functions to transmit light. From the viewpoints of controlling the directivity of light rays in any direction and facilitating manufacturing, the average width of this light transmission band 4 is preferably between 50 μm and 200 μm, more preferably between 80 μm and 170 μm, and even more preferably between 100 μm and 150 μm, taking tolerances into account. Furthermore, from the viewpoint of obtaining excellent transparency, the light transmittance when light rays are incident only on the light transmission band 4 is preferably between 75% and 100%, and even more preferably between 75% and 100%.

[0037] Each light-shielding band 5 is made of silicone rubber that has been colored to block light, and is formed into a rectangular shape with a vertically elongated cross section that is thinner and narrower than the light-transmitting band 4, and functions to block light rays. The silicone rubber has the light-shielding color by adding a colorant such as a pigment or dye to the type of silicone rubber used for the light-transmitting band 4 that has the physical properties described above. Specific examples of colorants include common organic or inorganic pigments such as carbon black, iron oxide, titanium oxide, yellow iron oxide, disazo yellow, and phthalocyanine blue, but black carbon black, which has excellent blocking properties, is optimal.

[0038] When a black pigment is not used as the colorant, it is preferable to use a white pigment in combination to ensure light-blocking properties. One colorant may be used alone, or two or more may be used in combination. Furthermore, from the viewpoint of controlling the directivity of light rays in any direction and facilitating manufacturing, the average width of each light-blocking zone 5 should be 1 μm or more and 50 μm or less, preferably 5 μm or more and 30 μm or less, more preferably 8 μm or more and 20 μm or less, and even more preferably around 10 μm, taking tolerances into account.

[0039] The adhesive 6 is formed from a transparent silicone rubber having adhesive properties in consideration of its compatibility with silicone rubber, and bonds the opposing surfaces of the first and second light-transmitting resin films 2, 2A and the pair of louver layers 3, 3A to transmit light. The transparent silicone rubber may be a silicone-based adhesive or adhesive silicone rubber sheet that has excellent heat resistance (temperatures above 90°C), cold resistance, moisture resistance, environmental resistance, flexibility, transparency, etc., and helps prevent warping and deformation. Specific examples of silicone-based adhesives include thermosetting adhesives such as KE-1825 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.) and KE-1056 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0040] The adhesive 6 hardens to form an adhesive layer, and the thickness of this adhesive layer is optimally 10 μm or more and 32 μm or less, preferably 15 μm or more and 25 μm or less, and more preferably about 20 μm, from the viewpoint of thinning the light transmission direction control sheet 1. Furthermore, the hardness of the adhesive layer formed by hardening the adhesive 6, when measured with a type A durometer in accordance with JIS K6253, is optimally 10 or more and 60 or less, preferably 10 or more and 30 or less or 30 or more and 60 or less, and more preferably 10 or more and 30 or less or 50 or more and 60 or less. This is because if the hardness of the adhesive layer is 10 or more and 60 or less, warping and deformation of the pair of louver layers 3, 3A can be prevented.

[0041] In order to obtain excellent transparency, the light transmittance when light is incident only on the adhesive layer is preferably 65% ​​or more, preferably 65% ​​or more and 100% or less, and more preferably 80% or more and 100% or less.

[0042] In the above configuration, when manufacturing the light transmission direction control sheet 1, first, a pair of louver layers 3, 3A are manufactured. Specifically, a plurality of transparent silicone rubber sheets for the light transmission band and a plurality of black-colored silicone rubber sheets for the light-shading band are prepared, and these plurality of silicone rubber sheets for the light transmission band and silicone rubber sheets for the light-shading band are alternately stacked to form a laminate, and this laminate is heated, vulcanized, and pressurized to form a block body, and then the block body is cut, whereby a pair of elastic louver layers 3, 3A can be manufactured in sheet form.

[0043] The silicone rubber sheet for the light transmission band and the silicone rubber sheet for the light shading band can be manufactured by extrusion molding, calendar molding, or press molding. The silicone rubber sheet for the light transmission band and the silicone rubber sheet for the light shading band may be bonded by thermocompression, but it is best to alternately laminate and bond them with a transparent silicone adhesive, which is expected to provide reliable adhesion.

[0044] Next, a first light-transmitting resin film 2 is prepared, and a thin film of transparent adhesive silicone rubber, which will serve as the adhesive 6, is applied to most of the surface of this first light-transmitting resin film 2, excluding the peripheral edges (see FIG. 3). After the transparent adhesive silicone rubber has been applied in this manner, a pair of louver layers 3, 3A are butted together and brought into close contact with each other, facing in opposite directions, and the pair of louver layers 3, 3A are laminated and bonded to the surface of the first light-transmitting resin film 2 using the adhesive silicone rubber, and the pair of louver layers 3, 3A are then butted together again by hand while being adjusted so that there are no gaps and they are tightly attached (see FIG. 4).

[0045] During this lamination and bonding, the arrangement direction of the light transmission zones 4 and the light blocking zones 5 of the louver layer 3 facing the light source 13 is different from and perpendicular to the arrangement direction of the pair of louver layers 3, 3A (the left-right direction in FIG. 4 ). In contrast, the arrangement direction of the light transmission zones 4 and the light blocking zones 5 of the louver layer 3A facing the light sensor 14 matches the arrangement direction of the pair of louver layers 3, 3A. Furthermore, during lamination and bonding, if a rotatable hand roll is pressed against the pair of louver layers 3, 3A and the lamination and bonding is performed while rotating and shifting the hand roll, air can be discharged from between the first light-transmitting resin film 2 and the pair of louver layers 3, 3A to the outside, preventing diffuse reflection of light and reduced transparency due to remaining air.

[0046] Next, a second light-transmitting resin film 2A is prepared, and a thin film of transparent adhesive silicone rubber, which will serve as the adhesive 6, is applied to most of the surface of this second light-transmitting resin film 2A except for the peripheral edges, and this adhesive silicone rubber is then bonded to the surfaces of the pair of louver layers 3, 3A (see FIG. 5). In this case, a rotatable hand roll is pressed against the second light-transmitting resin film 2A, and the hand roll is rotated and shifted while bonding the film, thereby discharging air from between the pair of louver layers 3, 3A and the second light-transmitting resin film 2A to the outside, thereby preventing diffuse reflection of light rays and a decrease in transparency due to remaining air.

[0047] Once the pair of louver layers 3, 3A are sandwiched between the first and second light-transmitting resin films 2, 2A in this manner, they are heated and hardened to form the adhesive 6 into an adhesive layer, and then the excess portions of the first and second light-transmitting resin films 2, 2A are cut and removed along the peripheral edges of the pair of louver layers 3, 3A (see Figure 6), thereby producing the light transmission direction control sheet 1.

[0048] The refractive index of the first and second light-transmitting resin films 2 and 2A in the manufactured light transmission direction control sheet 1 is 1.57 or more and 1.59 or less, for example, around 1.58, when the first and second light-transmitting resin films 2 and 2A are polycarbonate resin films. These refractive indices can be measured with a refractometer in accordance with JIS K7142, as described above. Furthermore, the refractive index of the light-transmitting bands 4 of the louver layers 3 and 3A is preferably 1.41 or more and 1.43 or less, and preferably around 1.42, in order to prevent interfacial reflection. The refractive index of the adhesive layer in which the adhesive 6 is cured is preferably 1.40 or more and 1.42 or less, and preferably around 1.41, in order to prevent interfacial reflection.

[0049] According to the above configuration, the pair of louver layers 3, 3A are butted together in close contact, eliminating the air layer A between the pair of louver layers 3, 3A, thereby preventing diffuse reflection of light. In particular, since the louver layers 3, 3A are not butted together but rather are butted together with elastic louver layers 3, 3A made of silicone rubber, the butted surfaces of the louver layers 3, 3A elastically deform to reliably fill the gap G. Therefore, the optical sensor 14 does not malfunction or detect incorrectly.

[0050] Furthermore, since there is no need to inject a filling adhesive into the gap G to fill the air layer A, it is possible to eliminate the risk of part of the air layer A remaining or contamination near the opposing surfaces of the pair of louver layers 3, 3A. Furthermore, when the average width of the light transmission band 4 is 100 μm or more and 150 μm or less, stacking and cutting operations can be facilitated.

[0051] 7 shows a second embodiment of the present invention, in which a plurality of dovetail grooves 7 serving as recesses are cut out at predetermined intervals on the butting surface of one of the pair of louver layers 3, 3A, and a plurality of dovetail necks 8 serving as protrusions are formed at predetermined intervals on the butting surface of the other louver layer 3A, and the pair of louver layers 3, 3A are butted together while these dovetail grooves 7 and dovetail necks 8 are fitted together. The dovetail grooves 7 and dovetail necks 8 of the pair of louver layers 3, 3A are each formed in plurality by a punching blade, for example, when cutting the block body.

[0052] In the present embodiment, when manufacturing the light transmission direction control sheet 1, the process is the same up to the point where adhesive silicone rubber is applied to the surface of the first light-transmitting resin film 2, but the orientations of the pair of louver layers 3, 3A are changed, and the dovetail grooves 7 and dovetail necks 8 of the pair of louver layers 3, 3A are butted together while tightly fitting together, and the pair of louver layers 3, 3A are laminated and bonded to the surface of the first light-transmitting resin film 2 via the adhesive silicone rubber.

[0053] During this lamination and bonding, the arrangement direction of the light transmission zones 4 and the light blocking zones 5 of the louver layer 3 facing the light source 13 is perpendicular to the arrangement direction of the pair of louver layers 3, 3A. In contrast, the arrangement direction of the light transmission zones 4 and the light blocking zones 5 of the louver layer 3A facing the light sensor 14 coincides with the arrangement direction of the pair of louver layers 3, 3A (the left-right direction in FIG. 7 ). Furthermore, during lamination and bonding, if a rotatable hand roll is pressed against the pair of louver layers 3, 3A and the lamination and bonding is performed while rotating and shifting the hand roll, air can be discharged from between the first light-transmitting resin film 2 and the pair of louver layers 3, 3A to the outside, preventing diffuse reflection of light and reduced transparency due to remaining air.

[0054] Next, a second light-transmitting resin film 2A is prepared, and a thin film of transparent adhesive silicone rubber, which will serve as the adhesive 6, is applied to most of the surface of this second light-transmitting resin film 2A except for the peripheral edges, and this adhesive silicone rubber is then bonded to the surfaces of the pair of louver layers 3, 3A. In this case, a rotatable hand roll is pressed against the second light-transmitting resin film 2A, and the hand roll is rotated and shifted while bonding, thereby discharging air from between the pair of louver layers 3, 3A and the second light-transmitting resin film 2A to the outside, preventing diffuse reflection of light rays and reduced transparency due to remaining air.

[0055] After sandwiching the pair of louver layers 3, 3A between the first and second light-transmitting resin films 2, 2A in this manner, the adhesives 6 are heated and cured to form adhesive layers, product-forming lines 9 for cutting are drawn on the second light-transmitting resin film 2A, and then the first light-transmitting resin film 2, the pair of louver layers 3, 3A, and the second light-transmitting resin film 2A are cut and removed along the product-forming lines 9 on the second light-transmitting resin film 2A, thereby producing the light transmission direction control sheet 1. As shown in FIG. 7 , the product-forming lines 9 are drawn with the required number of dotted lines or the like in areas of the pair of louver layers 3, 3A that do not include the multiple dovetail grooves 7 and dovetail necks 8. The other parts are the same as those in the above embodiment, so a description thereof will be omitted.

[0056] In this embodiment, the same effects as those of the above embodiment can be expected, and moreover, the pair of louver layers 3, 3A are positioned while tightly fitting the multiple dovetail grooves 7 and dovetail necks 8, thereby preventing the generation of air bubbles B due to misalignment of the louver layers 3, 3A. To explain this effect in more detail, when the pair of louver layers 3, 3A are sandwiched between the first and second light-transmitting resin films 2, 2A and the adhesive 6 is heated, the difference in thermal expansion coefficients between the first and second light-transmitting resin films 2, 2A and the louver layers 3, 3A causes the louver layers 3, 3A to misalign, and as a result, air bubbles B often occur between the pair of louver layers 3, 3A (see FIG. 6 ).

[0057] In view of this, if the movement of the pair of louver layers 3, 3A is restricted by tightly fitting the multiple dovetail grooves 7 and dovetail necks 8, an adhesive force is generated when the adhesive 6 is heated, and air bubbles B are not generated between the pair of louver layers 3, 3A.

[0058] In the above embodiment, the first and second light-transmitting resin films 2 and 2A are polycarbonate resin films, but the present invention is not limited to this. For example, polybutylene terephthalate resin films or acrylic resin films may also be used. Furthermore, at least one of the first and second light-transmitting resin films 2 and 2A may be subjected to an anti-glare (AG) coating treatment or a hard coating treatment to prevent dazzling reflections of light.

[0059] A protective acrylic plate may be laminated to at least one of the first and second light-transmitting resin films 2, 2A. The arrangement direction of the light-transmitting bands 4 and the light-shielding bands 5 of the louver layer 3A facing the optical sensor 14 may be approximately perpendicular to the arrangement direction of the pair of louver layers 3, 3A. Furthermore, the dovetail groove 7 and the dovetail neck 8 may be modified to have similar shapes as necessary.

[0060] Examples of the light transmission direction control sheet and its manufacturing method according to the present invention will be described below. [Example 1] To manufacture the light transmission direction control sheet shown in Figures 1 and 2, multiple transparent silicone rubber sheets for the light transmission band and black silicone rubber sheets for the light shading band were prepared, and these multiple silicone rubber sheets for the light transmission band and the light shading band were alternately stacked and thermocompression bonded to form a laminate. Each silicone rubber sheet for the light transmission band was a 125 μm thick KE1571U (product name, manufactured by Shin-Etsu Chemical Co., Ltd.). In contrast, a 10 μm thick KE153U (product name, manufactured by Shin-Etsu Chemical Co., Ltd.) silicone rubber sheet, which was a blend of 100 parts by weight of silicone rubber and 15 parts by weight of carbon black, was used for the light shading band.

[0061] When constructing the laminate, the hardness, tensile strength, elongation at break, and tear strength (crescent type) of the Type A silicone rubber sheet for the light transmission band used in the laminate were measured using a durometer. As a result of the measurements, the hardness of the test piece of the silicone rubber sheet measured in accordance with JIS K6253-3 was 78, the tensile strength of the silicone rubber sheet measured in accordance with JIS K6251 was 10.5 MPa, the elongation at break of the silicone rubber sheet measured in accordance with JIS K6251 was 380%, and the tear strength of the silicone rubber sheet measured in accordance with JIS K6252 was 18 kN / m. The hardness of the test piece was measured using an Asker Rubber Hardness Tester Type A (product name, manufactured by Kobunshi Keiki Co., Ltd.).

[0062] After the laminate was formed, it was heated, vulcanized, and pressed to form a block, which was then cut into a pair of 1.2 mm thick louver layers in the form of sheets, along a cutting plane perpendicular to the surface of the sheet.

[0063] Next, a first light-transmitting resin film was prepared, and a thin layer of transparent adhesive silicone rubber was applied to most of the surface of the first light-transmitting resin film, excluding the peripheral edge. The first light-transmitting resin film was a commercially available polycarbonate resin film with a thickness of 0.2 mm. KE1825 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the transparent adhesive silicone rubber. After the transparent adhesive silicone rubber was applied, a pair of louver layers were butted together so that their orientations were 90° apart, and the pair of louver layers were laminated and bonded to the surface of the first light-transmitting resin film using the adhesive silicone rubber. The pair of louver layers were then butted together again by hand, adjusting the alignment to ensure no gaps were present.

[0064] During lamination and bonding, a hand roll was pressed against the pair of louver layers, and the lamination and bonding was performed while rotating and shifting the hand roll, thereby discharging air from between the first light-transmitting resin film and the pair of louver layers to the outside.

[0065] Next, a second light-transmitting resin film was prepared, and a thin film of transparent adhesive silicone rubber was applied to most of the surface of the second light-transmitting resin film, excluding the peripheral edges, and this adhesive silicone rubber was adhered to the surfaces of the pair of louver layers. The second light-transmitting resin film was a commercially available polycarbonate resin film with a thickness of 0.2 mm. The transparent adhesive silicone rubber was KE1825 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0066] In this case, too, a hand roll was pressed against the second light-transmitting resin film, and the hand roll was rotated and shifted while adhering, thereby discharging air to the outside from between the pair of louver layers and the second light-transmitting resin film.

[0067] After sandwiching the pair of louver layers between the first and second light-transmitting resin films in this way, they were heated and cured to form hardened adhesive layers for each adhesive, and then the excess portions of the first and second light-transmitting resin films were cut and removed along the peripheral edges of the pair of louver layers, thereby producing a light transmission direction control sheet.

[0068] The thickness of each adhesive layer of the manufactured light transmission direction control sheet was measured and found to be 20 μm. The hardness of this adhesive layer was measured using a test piece with a Type A durometer in accordance with JIS K 6253-3 and found to be 30. An Asker Rubber Hardness Tester Type A (manufactured by Kobunshi Keiki Co., Ltd.: product name) was used as the measuring instrument. The refractive index of each adhesive layer was measured and found to be 1.41, and the refractive index of the first and second light-transmitting resin films was measured and found to be 1.58, respectively. These refractive indices were measured with a refractometer in accordance with JIS K7142. The refractometer used was a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.: product name) with a measurement wavelength of 589 nm.

[0069] When the manufactured light transmission direction control sheet was visually observed, no gaps were found between the pair of louver layers. As a result, it is presumed that diffuse reflection of light rays can be prevented even when the light transmission direction control sheet is used in the module device shown in FIG.

[0070] Example 2 When the block body of Example 1 was cut to form a pair of louver layers each 1.2 mm thick into sheets, two dovetail grooves that would become recesses were cut out at a predetermined interval on the butting surface of one of the louver layers, and two dovetail necks that would become protrusions were punched out at a predetermined interval on the butting surface of the other louver layer. After the pair of louver layers was formed into sheets in this way, the orientations of the pair of louver layers were shifted by 90°, and the dovetail grooves and dovetail necks of the pair of louver layers were butted together while tightly fitting them together.

[0071] Next, a thin film of transparent adhesive silicone rubber was applied to most of the surface of the first light-transmitting resin film, and a pair of closely spaced louver layers was laminated and bonded to the surface of this first light-transmitting resin film via the adhesive silicone rubber. The first light-transmitting resin film and adhesive silicone rubber were the same as in Example 1. During the lamination and bonding, the hand roll of Example 1 was pressed against the pair of louver layers, and air was discharged from between the first light-transmitting resin film and the pair of louver layers to the outside.

[0072] Next, a second light-transmitting resin film was prepared, and a thin film of transparent adhesive silicone rubber was applied to most of the surface area of ​​this second light-transmitting resin film as an adhesive, and this adhesive silicone rubber was adhered to the surfaces of the pair of louver layers. The second light-transmitting resin film and adhesive silicone rubber were the same as in Example 1. At this time, the hand roll of Example 1 was also pressed against the second light-transmitting resin film, and air was discharged from between the pair of louver layers and the second light-transmitting resin film to the outside.

[0073] After sandwiching the pair of louver layers between the first and second light-transmitting resin films in this way, they were heated and cured to turn the adhesive into an adhesive layer, and after drawing a product-forming line for cutting as shown in Figure 7 on the surface of the second light-transmitting resin film, the first light-transmitting resin film, the pair of louver layers, and the second light-transmitting resin film were cut and removed along the product-forming line to produce a light transmission direction control sheet.

[0074] The thickness, hardness, and refractive index of each adhesive layer of the manufactured light transmission direction control sheet were measured, and the values ​​were the same as those in Example 1. The refractive indexes of the first and second light-transmitting resin films were also measured, and the values ​​were the same as those in Example 1. When the light transmission direction control sheet was visually observed, no gaps were found between the pair of louver layers. As a result, it is presumed that diffuse reflection of light rays can be prevented even when the light transmission direction control sheet is used in the module device shown in FIG.

[0075] The light transmission direction control sheet and its manufacturing method according to the present invention are used in the manufacturing fields of various detection devices, image display devices, medical devices such as infusion devices, liquid crystal displays, CIDs, and the like.

[0076] REFERENCE SIGNS LIST 1 Light transmission direction control sheet 2 First light-transmitting resin film 2A Second light-transmitting resin film 3 Louver layer 3A Louver layer 4 Light-transmitting band 5 Light-shielding band 6 Adhesive 7 Dovetail groove (recess) 8 Dovetail neck (protrusion) 9 Product forming line 10 Module device 11 Housing 13 Light source 14 Optical sensor A Air layer B Air bubble G Gap

Claims

1. A light transmission direction control sheet comprising opposing first and second light-transmitting resin films and a plurality of louver layers interposed between the first and second light-transmitting resin films and bonded with an adhesive, the plurality of louver layers being butted together and in close contact with each other.

2. A light transmission direction control sheet as described in claim 1, wherein each louver layer is formed by alternating a plurality of light transmission zones and light blocking zones, each light transmission zone being formed from light-transmitting silicone rubber and each light blocking zone being formed from colored silicone rubber, and the hardness of these silicone rubbers is 73 or more and 83 or less when measured with a type A durometer in accordance with JIS K6253.

3. The light transmission direction control sheet according to claim 2, wherein the silicone rubber of each louver layer has a tensile strength of 7.5 MPa or more and 13.5 MPa or less when measured in accordance with JIS K6251, an elongation at break of 270% or more and 490% or less when measured in accordance with JIS K6251, and a tear strength of 8 kN / m or more and 28 kN / m or less when measured in accordance with JIS K6252.

4. A light transmission direction control sheet according to claim 2 or 3, wherein the adhesive is adhesive silicone rubber and the hardness after curing is 10 or more and 60 or less when measured with a type A durometer in accordance with JIS K6253.

5. The light transmission direction control sheet according to claim 1 or 2, which is attached to a module device and covers a light source and a light sensor of the module device.

6. A method for producing a light transmission direction control sheet as described in claim 1 or 2, comprising the steps of: bonding a plurality of elastic louver layers, each having alternating light transmission zones and light blocking zones, to a first light transmission resin film with an adhesive; butting the plurality of louver layers together to bring them into close contact; bonding a second light transmission resin film to the plurality of louver layers with an adhesive; and heat-curing the adhesive.

7. A method for manufacturing a light transmission direction control sheet as described in claim 6, in which a recess is formed on the butt peripheral portion of some of the multiple louver layers, and a protrusion is formed on the butt peripheral portion of the remaining louver layers, and the multiple louver layers are butted together while fitting these recesses and protrusions together.

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