Light transmission direction control sheet and method for manufacturing same

Abstract

The invention provides a light transmission direction control sheet and a manufacturing method thereof, wherein the light transmission direction control sheet can realize improved transmittance and thinness. The shutter comprises a first shutter layer 2, a second shutter layer 2A, an interlayer bonding layer 5 used for the first shutter layer 2 and the second shutter layer 2A, a surface film layer 6 used for the first shutter layer 2, a surface side bonding layer 7 used for the first shutter layer 2 and the surface film layer 6, a back film layer 8 used for the second shutter layer 2A, and a back side bonding layer 9 used for the second shutter layer 2A and the back film layer 8. In the first and second shutter layers 2, 2A, light-transmissive tapes 3 and light-shielding tapes 4 are alternately arranged, the light-transmissive tapes 3 are formed from light-transmissive silicone rubber, the light-shielding tapes 4 are formed from colored silicone rubber, the hardness of the silicone rubber is 73-83, the interlayer adhesive layer 5, the surface-side adhesive layer 7 and the back-side adhesive layer 9 are formed from adhesive silicone rubber, the hardness of the adhesive silicone rubber is 10-60, and the light-shielding tapes 4 are formed from colored silicone rubber. The thickness of the interlayer adhesive layer 5 is 10 [mu] m or more and 30 [mu] m or more.

Description

Technical Field

[0001] The present invention relates to a light transmission direction control sheet used in various detection devices or image display devices of automobiles to control light paths or viewing angles, and a method for manufacturing the sheet. Background Art

[0002] like Figure 9 and Figure 10 As shown, the conventional light transmission direction control sheet 30 has a first and a second louver layer group 31, 31A opposite to each other in the up and down directions. These first and second louver layer groups 31, 31A are thickness control sheets formed by orthogonally stacking and bonding via an adhesive layer 33, and are used in sensors or fingerprint authentication devices, etc. (refer to patent documents 1, 2, 3, 4).

[0003] The first louver layer group 31 is stacked to include: a first louver layer 32 with excellent rigidity, an adhesive layer 33 respectively bonded to the front and back surfaces of the first louver layer 32, a light-transmitting surface film layer 34 bonded to the surface of the first louver layer 32 via the adhesive layer 33, and a first internal film layer 35 bonded to the back surface of the first louver layer 32 via the adhesive layer 33.

[0004] The first louver layer 32 is formed by alternating light-transmitting portions made of, for example, acrylic resin or polycarbonate resin, and microscopic louver-like elements that block light. Furthermore, the first inner film layer 35 is made of, for example, a strong, transparent polyethylene terephthalate resin film approximately 0.2 mm thick. This layer corrects the warping of the first louver layer 32, which is susceptible to significant warping.

[0005] In contrast, the second louver layer group 31A is stacked to include: a second louver layer 32A with excellent rigidity, an adhesive layer 33 respectively bonded to the front and back surfaces of the second louver layer 32A, a second internal film layer 35A bonded to the surface of the second louver layer 32A via the adhesive layer 33, and a light-transmitting back film layer 36 bonded to the back surface of the second louver layer 32A via the adhesive layer 33. The second internal film layer 35A is bonded to the first internal film layer 35 of the first louver layer group 31 via the adhesive layer 33.

[0006] The second louver layer 32A is also formed by alternating light-transmitting portions made of acrylic resin or polycarbonate resin and microscopic louver-like elements that block light. Furthermore, the inner film layer 35A is made of a transparent polyethylene terephthalate resin film, approximately 0.2 mm thick and possessing excellent strength. This layer corrects the warping of the second louver layer 32A, which is subject to significant warping.

[0007] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2004-109615 Patent Document 2: Japanese Patent Application Laid-Open No. 2016-224259 Patent Document 3: Japanese Patent Application Laid-Open No. 2007-212507 Patent Document 4: Japanese Patent Application Laid-Open No. 2021-99437 Summary of the Invention

[0008] Problems to be solved by the invention Conventional light transmission direction control sheets 30 have a multi-layer structure as described above. Due to the proneness to warping of the first and second louver layers 32 and 32A, the number of components and interfaces is high, potentially leading to reduced transmittance due to interfacial reflections. Furthermore, since the first and second louver layer groups 31 and 31A require internal film layers 35 and 35A, respectively, while warping of the first and second louver layers 32 and 32A can be corrected, this does not allow for thinning, potentially causing problems during assembly into equipment.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light transmission direction control sheet and a method for producing the sheet, which can achieve improved transmittance and reduced thickness.

[0010] Solutions to Problems In order to solve the above-mentioned problems, the present invention comprises: first and second louver layers facing each other, an interlayer adhesive layer bonding the first and second louver layers together, a light-transmitting surface film layer facing the surface of the first louver layer, a surface-side adhesive layer bonding the first louver layer and the surface film layer together, a light-transmitting back film layer facing the back of the second louver layer, and a back-side adhesive layer bonding the second louver layer and the back film layer together, wherein the first and second louver layers are cross-stacked, and is characterized in that: The first and second louver layers are formed by alternating a plurality of light-transmitting bands and light-blocking bands, each of which is formed of light-transmitting silicone rubber, and each of which is formed of colored silicone rubber, wherein the Shore A hardness of these silicone rubbers is not less than 73 and not more than 83 when measured using a Type A durometer in accordance with JIS K6253. The interlayer adhesive layer, the front side adhesive layer, and the back side adhesive layer are each formed of an adhesive silicone rubber, and have a Shore A hardness of 10 to 60 when measured using a type A durometer in accordance with JIS K 6253. At least the thickness of the interlayer adhesive layer is 10 to 30 μm.

[0011] Furthermore, the device can be mounted on a light source of a detection device that irradiates light onto an object to control the optical path of the light. Furthermore, the device can be integrated with an image display device in an automobile to control the optical path of the light.

[0012] Furthermore, when measured with a refractometer in accordance with JIS K 7142, it is preferable that the difference in refractive index between the first and second louver layers and the interlayer adhesive layer is 0.02 or less. In addition, it is preferred that the silicone rubber of the first and second louver layers has a tensile strength of not less than 7.5 MPa and not more than 13.5 MPa when measured in accordance with JIS K 6251, an elongation at break when measured in accordance with JIS K 6251 of not less than 270% and not more than 490%, and a tear strength when measured in accordance with JIS K 6252 of not less than 8 kN / m and not more than 28 kN / m.

[0013] In addition, in the present invention, in order to solve the above-mentioned problems, a method for manufacturing a light transmission direction control sheet is a method for manufacturing a light transmission direction control sheet according to technical solutions 1, 2 or 3, characterized in that a plurality of silicone rubber sheets for light transmission belts and silicone rubber sheets for light-shielding belts are alternately stacked to form a stacked body, the stacked body is pressurized and then cut to form the first and second louver layers, adhesive silicone rubber is respectively applied to the opposing surfaces of the first and second louver layers, the exposed surface of the first louver layer, and the exposed back surface of the second louver layer, so that the first and second louver layers are crossed and stacked and bonded, and an adhesive surface film layer is stacked on the surface of the first louver layer, and an adhesive back film layer is stacked on the back of the second louver layer.

[0014] Here, the physical property values ​​of the silicone rubber of the first and second louver layers in the claims include approximate values ​​if there is no difference in the effects. In addition, the irradiated body includes at least transparent, opaque, and translucent solids, liquids, and droplets. Examples of the irradiated body include various mechanical parts, electrical / electronic parts, transparent bottles or containers, liquid medicines or their droplets, etc. The detection device includes at least a device for detecting the presence, position, size, shape, number, flow rate, speed, etc. of the irradiated body. Furthermore, the light transmission direction control sheet of the present invention can be used for at least detection devices, image display devices, medical devices such as drip devices, liquid crystal displays, CIDs, water meters, etc.

[0015] According to the present invention, since the first and second louver layers are formed of highly flexible, non-warping silicone rubber, the number of internal film layers or adhesive layers with different refractive indices can be reduced. Furthermore, the number of components can be reduced, enabling the overall thinning of the light transmission direction control sheet.

[0016] Effects of the Invention According to the present invention, the light-transmitting strips of the first and second louver layers are formed from light-transmitting silicone rubber, while the light-blocking strips are formed from colored silicone rubber. This improves transmittance and enables a thinner design. Furthermore, since the silicone rubber has a Shore A hardness of 73 to 83, as measured using a Type A durometer in accordance with JIS K 6253, warping or deformation of the first and second louver layers can be prevented.

[0017] According to the invention described in claim 2, since the light transmission direction control sheet of the present invention is attached to the light source of the detection device, even when the illuminated object is opaque, the ends of the illuminated object can be clearly identified, and the shape, size, etc. of the illuminated object can be detected. Furthermore, even when the illuminated object is transparent or translucent, the ends of the illuminated object can be clearly visually recognized, and the presence or position of the illuminated object can be detected.

[0018] According to the invention described in Technical Solution 3, since the light transmission direction control sheet of the present invention is embedded in the image display device of a motor vehicle, the emission of light from the image display device can be controlled, eliminating the possibility that the image of the image display device is reflected on the windshield or door glass of the motor vehicle and causes obstacles to the driving of the motor vehicle.

[0019] According to the invention described in claim 4, the difference in refractive index between the first and second louver layers and the interlayer adhesive layer is 0.02 or less when measured with a refractometer according to JIS K 7142, thereby contributing to preventing interface reflection of the light transmission direction control sheet.

[0020] According to the invention described in claim 5 , by limiting the numerical values ​​of the tensile strength, elongation at break, and tear strength of the silicone rubber of the first and second louver layers, it is expected that the light transmission direction controlling sheet can be prevented from warping or deformation.

[0021] According to the invention described in Technical Solution 6, since a plurality of silicone rubber sheets for light-transmitting bands and silicone rubber sheets for light-shielding bands are alternately stacked to form a stacked body, and the stacked body is pressurized and then cut to form the first and second venetian blind layers, the first and second venetian blind layers having a plurality of light-transmitting bands and light-shielding bands arranged alternately can be quickly and easily manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a front explanatory view schematically showing an embodiment of the light transmission direction control sheet of the present invention. Figure 2 This is a side explanatory view schematically showing an embodiment of the light transmission direction control sheet of the present invention. Figure 3 It is an exploded explanatory diagram schematically showing an embodiment of the light transmission direction controlling sheet of the present invention. Figure 4 This is a plan view schematically showing a state in which a light transmission direction control sheet according to a second embodiment of the light transmission direction control sheet of the present invention is attached to a detection device. Figure 5 This is a plan view schematically illustrating problems in the second embodiment of the light transmission direction control sheet of the present invention. Figure 6 This is a plan view schematically showing a state where a light transmission direction control sheet according to a third embodiment of the light transmission direction control sheet of the present invention is attached to a detection device. Figure 7 It is a plan view schematically illustrating problems in the third embodiment of the light transmission direction control sheet of the present invention. Figure 8 This is a front explanatory view schematically showing a fourth embodiment of the light transmission direction control sheet of the present invention. Figure 9 This is an explanatory front view showing a conventional light transmission direction control sheet. Figure 10 This is a front explanatory view showing the first and second louver layer groups before bonding of a conventional light transmission direction control sheet. DETAILED DESCRIPTION

[0023] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figures 1 to 3 As shown, the light transmission direction control sheet 1 in this embodiment is a control sheet with a viewing angle of 90°, which comprises: a first and a second louver layer 2, 2A opposite to each other, an interlayer adhesive layer 5 bonding these first and second louver layers 2, 2A, a light-transmitting surface film layer 6 opposite to the surface of the first louver layer 2, a surface-side adhesive layer 7 bonding the first louver layer 2 and the surface film layer 6, a light-transmitting back film layer 8 opposite to the surface of the second louver layer 2, and a back-side adhesive layer 9 bonding the second louver layer 2A and the back film layer 8, contributing to the achievement of Goal 9 of SDGs (International Goals for Sustainable Development of the United Nations, Sustainable Development Goals consisting of 17 global goals and 169 goals (achievement benchmarks)) adopted at the United Nations Summit.

[0024] like Figures 1 to 3As shown, the light transmission direction control sheet 1 is formed into a rectangular shape, such as a rectangular or square shape. However, at least a portion of the peripheral edge may be notched, at least a portion of the peripheral edge may be curved, or at least one of the four corners may be chamfered. The overall light transmittance (total light transmittance) of the light transmission direction control sheet 1 is 46% or higher, preferably 46% or higher and 100% or lower, more preferably 47% or higher and 90% or lower, and even more preferably 48% or higher and 80% or lower. This is because if the overall light transmittance is less than 46%, visual recognition is deteriorated.

[0025] The light transmittance referred to herein is the value calculated as follows: Light transmittance = (B / A) × 100 (unit: %): In an apparatus using D65 light source specified in JIS Z 8720 and measuring the intensity of inspection light emitted from the light source by a light-receiving sensor, the output value of the light-receiving sensor when no object to be measured is in the optical path of the inspection light is set to A; and the output value of the light-receiving sensor when the object to be measured is placed in the optical path of the inspection light and the transmitted light that has passed through the object to be measured is received by the light-receiving sensor is set to B.

[0026] The first and second louver layers 2 and 2A are formed by alternately arranging a plurality of light-transmitting strips 3 and light-shielding strips 4 in a horizontal row, forming planar rectangular shapes of equal size, and are stacked in a crosswise manner in the vertical direction (Z direction). From the perspective of adjusting the directivity of light passing through the light-transmitting direction control sheet 1 in any direction or facilitating manufacturing, the thickness of the first and second louver layers 2 and 2A is 100 μm to 5000 μm, preferably 500 μm to 3500 μm, more preferably 600 μm to 2000 μm, and even more preferably approximately 1200 μm. In addition, the up-down, front-back, left-right directions of the light transmission direction control sheet 1 are directions based on the drawings and can be appropriately changed as needed.

[0027] The thickness of the first and second louver layers 2, 2A is fixed. This fixedness in this context includes a thickness within a range of ±5% of the designed value. The thickness of the first and second louver layers 2, 2A can be determined by measuring a cross-sectional photograph of each of the first and second louver layers 2, 2A. The average value of the values ​​measured at ten or more locations is preferably used.

[0028] Considering the improvement of light transmittance and tolerance, the first and second louver layers 2 and 2A preferably intersect at an angle that is substantially perpendicular to each other. Specifically, the angle is preferably 85° to 95°, preferably 88° to 92°, and more preferably 90°.

[0029] From the perspective of reducing the number of components, each light-transmitting strip 3 of the first and second louver layers 2 and 2A is formed into a strip by light-transmitting silicone rubber having excellent heat resistance, cold resistance, moisture resistance, environmental resistance, softness, colorability, transparency, etc. above 90°C, which helps to prevent warping or deformation. Each shading strip 4 is formed into a strip by silicone rubber with light-shielding coloring applied to transparent silicone rubber. By forming these light-transmitting strips 3 and shading strips 4 to the same height, the front and back are symmetrical.

[0030] Examples of silicone rubber include silicone rubber compositions generally referred to as mirabu rubber, which are composed of a diorganopolysiloxane having its molecular chain ends blocked with hydroxysilyl or vinylsilyl groups and an organic peroxide; and so-called addition-reaction-type silicone rubber compositions, which are formed by blending a diorganopolysiloxane having at least two vinyl groups bonded to silicon atoms with an organohydrogenpolysiloxane having at least three hydrogen atoms bonded to silicon atoms (i.e., SiH bonds) and a platinum catalyst. Specific examples of silicone rubber include KE-153U (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0031] The density of silicone rubber measured at 23°C according to JIS K 6268 is 1.21 g / cm 3 Above 1.25g / cm 3 Below, preferably 1.24g / cm 3 From the perspective of preventing warping or deformation of the first and second louver layers 2 and 2A, the Shore A hardness, as measured using a rubber / plastic durometer (Type A durometer) in accordance with JIS K 6253, is preferably 73 to 83, preferably 78 to 79. From the perspective of preventing warping or deformation, the tensile strength, as measured in accordance with JIS K 6251, is preferably 7.5 MPa to 13.5 MPa, preferably approximately 10.5 MPa.

[0032] The silicone rubber preferably has an elongation at break of 270% to 490%, preferably 310% to 380%, when measured according to JIS K 6251. Furthermore, to prevent warping and deformation, the tear strength (Crescent type) measured according to JIS K 6252 is preferably 8 kN / m to 28 kN / m, preferably 13 kN / m to 18 kN / m. These measurements can be made using measuring equipment or testing machines from, for example, M&K Co., Ltd. or ITS Japan Co., Ltd.

[0033] The setting angles of the light-transmitting bands 3 and the light-shielding bands 4 are adjusted to be greater than 0° and less than 1°, respectively. Each light-transmitting band 3 is formed of transparent silicone rubber into a longitudinally long rectangular cross-section and serves to transmit light. From the perspective of controlling the directivity of light in an arbitrary direction and seeking ease of manufacturing, the average width of the light-transmitting bands 3 is greater than 50 μm and less than 200 μm, preferably greater than 80 μm and less than 170 μm, and more preferably greater than 100 μm and less than 150 μm, taking into account tolerances. In addition, from the perspective of obtaining excellent transparency, the light transmittance when only light is incident on the light-transmitting bands 3 is greater than 75%, preferably greater than 75% and less than 100%, and more preferably greater than 85% and less than 100%.

[0034] Each light-shielding strip 4 is formed from silicone rubber with a light-shielding coloring, and has a longitudinally elongated rectangular cross-section that is thinner and narrower than the light-transmitting strips 3, thereby shielding light. The light-shielding coloring is imparted to the silicone rubber by adding a colorant such as a pigment or dye to the type of light-transmitting strip having the aforementioned physical properties. Specific examples of colorants include common organic and inorganic pigments such as carbon black, iron oxide, titanium oxide, yellow iron oxide, disazo yellow, and phthalocyanine blue. Black carbon black, due to its excellent shielding properties, is most preferred.

[0035] In the case where a black pigment is not used as a colorant, it is preferred to use a white pigment in combination to ensure light-shielding properties. A single colorant may be used alone, or two or more may be used in combination. In addition, from the perspective of controlling the directivity of light to an arbitrary direction or facilitating manufacturing, the average width of each light-shielding band 4 is preferably 1 μm to 50 μm, preferably 5 μm to 30 μm, more preferably 8 μm to 20 μm, and even more preferably about 10 μm, taking into account tolerances.

[0036] The interlayer adhesive layer 5 is formed from transparent silicone rubber, which has adhesive properties due to its compatibility with silicone rubber. It bonds the opposing surfaces of the first and second louver layers 2 and 2A together, allowing light to pass through. Transparent silicone rubber is equivalent to a silicone adhesive or adhesive silicone rubber sheet, which exhibits excellent heat resistance, cold resistance, moisture resistance, environmental resistance, flexibility, and transparency above 90°C, and helps prevent warping and deformation. Specific examples of silicone adhesives include thermosetting adhesives such as KE-1825 (manufactured by Shin-Etsu Chemical Co., Ltd.) and KE-1056 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0037] To achieve a thinner light transmission direction control sheet 1, the thickness of the interlayer adhesive layer 5 is 10 μm to 32 μm, preferably 15 μm to 25 μm, and more preferably approximately 20 μm. Furthermore, the Shore A hardness of the interlayer adhesive layer 5, as measured using a Type A durometer in accordance with JIS K 6253, is 10 to 60, preferably 10 to 30 or 30 to 60, and more preferably 10 to 30 or 50 to 60.

[0038] This is because if the hardness of the interlayer adhesive layer 5 is between 10 and 60, warping and deformation of the first and second louver layers 2 and 2A can be prevented. From the perspective of achieving excellent transparency, the light transmittance when light is incident only on the interlayer adhesive layer 5 is preferably 65% ​​or more, preferably 65% ​​or more and 100% or less, and more preferably 80% or more and 100% or less.

[0039] The surface film layer 6 is made of polycarbonate resin films such as those excellent in heat resistance, weather resistance, impact resistance, dimensional accuracy, transparency, difficulty in warping, difficulty in deformation, and transmits light. From the viewpoint of suppressing installation space or ensuring that rigidity prevents warping, the thickness of this transparent surface film layer 6 is set at 0.1mm or more and 0.3mm or less, preferably 0.189mm or more and 0.2mm or less, more preferably 0.195mm or more and 0.2mm or less, further preferably 0.2mm or so.

[0040] From the viewpoint that obtains excellent transparency, the light transmittance when only making light incident on the surface film layer 6 is more than 75%, preferably more than 75% below 100%, more preferably more than 85% below 100% is preferred.In addition, the flexural elastic modulus when the polycarbonate resin film that uses in the surface film layer 6 is measured according to the determination test method of ISO 178 is preferably more than 91MPa below 2300MPa.

[0041] The surface-side adhesive layer 7, like the interlayer adhesive layer 5, is formed of adhesive transparent silicone rubber due to its compatibility with silicone rubber. It bonds the surface of the first louver layer 2 to the surface film layer 6 to allow light to pass through. Transparent silicone rubber is equivalent to a silicone adhesive or adhesive silicone rubber sheet that has excellent heat resistance, cold resistance, moisture resistance, environmental resistance, flexibility, transparency, etc. at temperatures above 90°C, and helps prevent warping and deformation. Specific examples of silicone adhesives include KE-1825 (manufactured by Shin-Etsu Chemical Co., Ltd.) and KE-1056 (manufactured by Shin-Etsu Chemical Co., Ltd.), which are thermosetting adhesives.

[0042] To achieve a thinner light transmission direction control sheet 1, the thickness of the front-side adhesive layer 7 is preferably 10 μm to 32 μm, preferably 15 μm to 25 μm, and more preferably approximately 20 μm. Furthermore, the Shore A hardness of the front-side adhesive layer 7, as measured using a Type A durometer in accordance with JIS K 6253, is preferably 10 to 60, preferably 10 to 30 or 50 to 60. This is because a hardness of 10 to 60 for the front-side adhesive layer 7 prevents warping and deformation of the light transmission direction control sheet 1. To achieve excellent transparency, the light transmittance when light is incident only on the front-side adhesive layer 7 is 65% or higher, preferably 65% ​​to 100%, and more preferably 80% to 100%.

[0043] Back film layer 8 is composed of a polycarbonate resin film, for example, that has excellent heat resistance, weather resistance, impact resistance, dimensional accuracy, transparency, and resistance to warping and deformation, for example, at temperatures above 90°C. It functions to transmit light. To minimize installation space and ensure rigidity to prevent warping, the thickness of transparent back film layer 8 is set to be between 0.1 mm and 0.3 mm, preferably between 0.189 mm and 0.2 mm, more preferably between 0.195 mm and 0.2 mm, and even more preferably approximately 0.2 mm.

[0044] In order to obtain excellent transparency, the light transmittance when only light is incident on the back film layer 8 is preferably 75% or more, preferably 75% or more and 100% or less, and more preferably 85% or more and 100% or less. In addition, the polycarbonate resin film used in the back film layer 8 preferably has a flexural modulus of 91 MPa or more and 2300 MPa or less when measured according to the measurement test method of ISO 178.

[0045] The back-side adhesive layer 9, like the interlayer adhesive layer 5, is formed from transparent silicone rubber with adhesive properties due to its compatibility with silicone rubber. It serves to bond the back surface of the second louver layer 2A to the back film layer 8, allowing light to pass through. Transparent silicone rubber is equivalent to a silicone adhesive or adhesive silicone rubber sheet that has excellent heat resistance, cold resistance, moisture resistance, environmental resistance, flexibility, and transparency above 90°C, and helps prevent warping and deformation. Specific examples of silicone adhesives include KE-1825 (manufactured by Shin-Etsu Chemical Co., Ltd.) and KE-1056 (manufactured by Shin-Etsu Chemical Co., Ltd.), which are thermosetting adhesives.

[0046] To achieve a thinner light transmission direction control sheet 1, the thickness of the back-side adhesive layer 9 is preferably 10 μm to 32 μm, preferably 15 μm to 25 μm, and more preferably approximately 20 μm. Furthermore, the Shore A hardness of the back-side adhesive layer 9, as measured using a Type A durometer in accordance with JIS K 6253, is preferably 10 to 60, preferably 10 to 30 or 50 to 60. This is because a hardness of 10 to 60 for the back-side adhesive layer 9 prevents warping and deformation of the light transmission direction control sheet 1. To ensure excellent transparency, the light transmittance when light is incident only on the back-side adhesive layer 9 is 65% or more, preferably 75% to 100%, and more preferably 80% to 100%.

[0047] In the above structure, when manufacturing the light transmission direction control sheet 1, first, a plurality of transparent silicone rubber sheets for light transmission belts and a plurality of black-colored silicone rubber sheets for light shielding belts are prepared, and these plurality of silicone rubber sheets for light transmission belts and silicone rubber sheets for light shielding belts are alternately stacked to form a laminate. The silicone rubber sheets for light transmission belts and the silicone rubber sheets for light shielding belts can be manufactured by extrusion molding, calendaring molding, or stamping molding. In addition, the silicone rubber sheets for light transmission belts and the silicone rubber sheets for light shielding belts can be hot-pressed, but it is best to alternately stack and bond them using a transparent silicone adhesive that can be expected to be reliably bonded.

[0048] Next, the laminate is heated, vulcanized, and pressurized to form a block. This block is then cut to form the first and second louver layers 2 and 2A in sheet form. Transparent adhesive silicone rubber is applied to the opposing surfaces of these first and second louver layers 2 and 2A, forming the interlayer adhesive layer 5. Furthermore, transparent adhesive silicone rubber is applied to the exposed surface of the first louver layer 2, forming the front-side adhesive layer 7, and transparent adhesive silicone rubber is applied to the exposed back surface of the second louver layer 2A, forming the back-side adhesive layer 9. Because the first and second louver layers 2 and 2A are made of silicone rubber, which exhibits minimal warping, they can be directly bonded together, achieving a thinner profile. Furthermore, the use of silicone rubber can be expected to further reduce the thickness of the interlayer adhesive layer 5.

[0049] Next, the opposing surfaces of the first and second Venetian blind layers 2 and 2A are pressure-bonded and bonded together. At this time, the layers are laminated and bonded so that the arrangement directions of the light-shielding strips 4 of the first and second Venetian blind layers 2 and 2A intersect at a 90° angle. Furthermore, before and after the bonding of the opposing surfaces, a surface film layer 6 and a back film layer 8 are laminated and bonded onto the adhesive silicone rubber, which will serve as the front-side adhesive layer 7 and the back-side adhesive layer 9, respectively. After the lamination and bonding operations are completed, the uncured adhesive silicone rubber is thermally cured, and unnecessary portions of the surface film layer 6 and back film layer 8 are removed, thereby producing the light transmission direction control sheet 1.

[0050] In the manufactured light transmission direction control sheet 1, the difference in refractive index between the first and second louver layers 2 and 2A and the interlayer adhesive layer 5 is 0.02 or less, preferably 0 or more and 0.02 or less, more preferably 0.001 or more and 0.02 or less, and even more preferably 0.01 or more and 0.02 or less. This is because a refractive index difference of 0.02 or less can be expected to prevent interfacial reflection. These refractive index differences can be measured using a refractometer according to JIS K 7142 after manufacturing a test piece.

[0051] In addition, to prevent interface reflection, the refractive index of the light-transmitting bands 3 of the first and second louver layers 2 and 2A in the manufactured light transmission direction control sheet 1 is 1.41 to 1.43, preferably about 1.42. Furthermore, to prevent interface reflection, the refractive index of the interlayer adhesive layer 5, the front-side adhesive layer 7, and the back-side adhesive layer 9 is 1.40 to 1.42, preferably about 1.41. When the front film layer 6 or the back film layer 8 is a polycarbonate resin film, the refractive index is 1.57 to 1.59, for example, about 1.58. These refractive indices, as described above, can be measured using a refractometer in accordance with JIS K 7142.

[0052] According to the above structure, since the first and second louver layers 2 and 2A are formed of a non-warping silicone rubber with excellent flexibility, the number of a pair of internal film layers 35 and 35A or adhesive layers 33 with different refractive indices can be reduced. Therefore, since the number of interfaces can be reduced, the possibility of reduced transmittance due to interface reflection can be effectively eliminated. In addition, by reducing the number of components, the light transmission direction control sheet 1 can be thinned by at least 0.2 mm, which can effectively eliminate the possibility of obstruction when assembled into the equipment. Moreover, when the average value of the width of the light transmission belt 3 is greater than 100 μm and less than 150 μm, the stacking operation or cutting operation can be facilitated.

[0053] then, Figure 4 A second embodiment of the present invention is shown. In this case, the manufactured light transmission direction control sheet 1 is attached to a detection device 11 that irradiates light onto an opaque workpiece 10 as an irradiated object, thereby controlling the optical path of the light.

[0054] The workpiece 10 is composed of, for example, a mechanical component conveyed by a conveyor in the manufacturing industry, and is formed into a circular, elliptical, or spherical shape. Furthermore, the detection device 11 includes, for example, a light source 12 for irradiating light onto the workpiece 10, and a detection sensor 13, such as a visual sensor (camera), for capturing the workpiece 10 illuminated by the light source 12 and detecting its shape and size. These light sources 12 and detection sensors 13 are arranged horizontally opposite each other around the conveyor. The light source 12 is, for example, a backlight for irradiating diffuse light, and a light transmission direction control sheet 1 is attached to the irradiation surface. The remaining components are the same as those in the above-described embodiment, and therefore their description is omitted.

[0055] In this embodiment, the same effects as those in the above embodiment can be expected. In addition, the peripheral portion of the workpiece 10 can be clearly detected, and the shape and size of the workpiece 10 can be detected with high precision. Figure 5 As shown, due to light diffraction and other factors, the shadow of the peripheral portion of the workpiece 10 becomes unclear, resulting in the possibility of not being able to detect the shape or size of the workpiece 10. In view of this, attaching a light transmission direction control sheet 1 to the light source 12 controls the optical path of the light and irradiates it horizontally, thereby clarifying the shadow of the peripheral portion of the workpiece 10. Therefore, it is expected that the peripheral portion of the workpiece 10 will be clarified, preventing misidentification of the workpiece 10 and enabling high-precision detection of the shape and size of the workpiece 10.

[0056] then, Figure 6 A third embodiment of the present invention is shown. In this case, the manufactured light transmission direction control sheet 1 is attached to a detection device 11 that irradiates light onto a light-transmitting bottle or liquid 14 as an irradiated object to control the optical path of the light.

[0057] Liquid 14, for example, made of various transparent drinking water, is filled from above to the upper portion of the opening of a light-transmitting bottle. Furthermore, a detection device 11 includes, for example, a light source 12 for illuminating the filled liquid 14 with light, and a detection sensor 13, such as a visual sensor (camera), for capturing the liquid 14 illuminated by the light source 12 and detecting the presence of the liquid. These light source 12 and detection sensor 13 are positioned around a conveyor that transports the bottles in a horizontally opposed manner. Light source 12 is, for example, a backlight that radiates diffuse light, and a light transmission direction control sheet 1 is attached to the irradiation surface. The remaining components are identical to those of the above-described embodiment, and therefore their description is omitted.

[0058] In this embodiment, the same effects as those in the above embodiment can be expected. In addition, the side end of the liquid 14 can be clearly visually recognized, and the presence of the liquid 14 can be detected with high precision. Figure 7 As shown, light is transmitted through the entire portion of liquid 14, making it impossible to detect the presence of liquid 14. In view of this, if a light transmission direction control sheet 1 is attached to light source 12, the optical path of the light can be controlled to irradiate the light horizontally, causing the light to enter or reflect the liquid 14 at an angle of approximately 90° (89° or 90°). As a result, the light is not transmitted through the side edges of liquid 14, which are detected as black. This prevents misidentification of liquid 14 and allows for highly accurate detection of the presence of liquid 14.

[0059] then, Figure 8 A fourth embodiment of the present invention is shown. In this embodiment, a light transmission direction control sheet 1 is embedded in an image display device 21 below an instrument panel 20 of an automobile to control the optical path of light. Other parts are the same as those in the above embodiment, so their description is omitted.

[0060] In this embodiment, the same effects as those in the above embodiment can be expected, and the possibility of causing obstacles to the driving of the motor vehicle can be eliminated. This effect is described in detail: When the image display device 21 is installed below the instrument panel 20 of the motor vehicle, the image of the image display device 21 may be reflected on the windshield 22 or door glass of the motor vehicle, causing obstacles to the driving of the motor vehicle (see Figure 8 In view of this, if the light transmission direction control sheet 1 of this embodiment is embedded in a light source such as a backlight of an image display device 21, it is possible to control the emission of light in the vertical, horizontal, and vertical directions, thereby eliminating the possibility of an image being reflected on the windshield 22 or door glass of a motor vehicle and causing an obstruction to the driving of the motor vehicle.

[0061] In addition, at least one of the surface film layer 6 and the back film layer 8 in the above embodiment may be subjected to an anti-glare (AG) coating treatment to prevent light from being reflected and becoming dazzling and difficult to see, or a hard coating treatment, etc. In addition, an acrylic plate for protection may be laminated on at least one of the surface film layer 6 and the back film layer 8. In addition, at least one of the surface film layer 6 and the back film layer 8 may be made of a polyethylene terephthalate resin film, etc.

[0062] In addition, the manufacturing order of the light transmission direction control sheet 1 can also be changed. After the first and second louver layers 2 and 2A are formed, adhesive silicone rubber serving as the interlayer adhesive layer 5 is applied to the opposing surfaces of the first and second louver layers 2 and 2A, respectively. The opposing surfaces of the first and second louver layers 2 and 2A are bonded to each other and heat-cured. An adhesive silicone rubber serving as the surface side adhesive layer 7 is applied to the exposed surface of the first louver layer 2, and an adhesive silicone rubber serving as the back side adhesive layer 9 is applied to the exposed back surface of the second louver layer 2A. An adhesive surface film layer 6 and a back film layer 8 are stacked on each adhesive silicone rubber and heat-cured, and then unnecessary portions of the surface film layer 6 and the back film layer 8 are removed.

[0063] Example Hereinafter, examples of the light transmission direction controlling sheet and the method for producing the same according to the present invention will be described together with comparative examples. [Example] To manufacture Figures 1 to 3 The light transmission direction control sheet shown, with a viewing angle of 90°, is made by first preparing a plurality of transparent silicone rubber sheets for light-transmitting belts and a black-colored silicone rubber sheet for light-shielding belts. These plurality of silicone rubber sheets for light-transmitting belts and light-shielding belts are alternately stacked and heat-pressed to form a laminate. Each silicone rubber sheet for light-transmitting belts uses KE1571U (Shin-Etsu Chemical Co., Ltd.) with a thickness of 125 μm. In contrast, the silicone rubber sheet for light-shielding belts uses KE153U (Shin-Etsu Chemical Co., Ltd.), which is 10 μm thick and is made by blending 15 parts by mass of carbon black with 100 parts by mass of silicone rubber.

[0064] When forming a laminate, the Shore A hardness, tensile strength, elongation at break, and tear strength (Crescent type) of the silicone rubber sheet used for the light-transmitting tape in the laminate were measured. The measurement results showed that the Shore A hardness of the silicone rubber sheet test piece measured according to JIS K 6253-3 was 78, the tensile strength of the silicone rubber sheet measured according to JIS K 6251 was 10.5 MPa, the elongation at break of the silicone rubber sheet measured according to JIS K 6251 was 380%, and the tear strength of the silicone rubber sheet measured according to JIS K 6252 was 18 kN / m. The Shore A hardness of the test piece was measured using an Asker Durometer Type A [manufactured by Polymer Instruments Co., Ltd.: product name].

[0065] Next, the laminate is heated, vulcanized, and pressurized to form a block, and the block is cut to form the first and second louver layers with a thickness of 1.2 mm into a sheet. When cutting the block, the cutting is performed along a cutting surface perpendicular to the surface of the sheet. After the first and second louver layers are formed in this way, an uncured thermosetting adhesive is applied to the opposing surfaces of the first and second louver layers to form an interlayer adhesive layer, an uncured thermosetting adhesive is applied to the exposed surface of the first louver layer to form a surface-side adhesive layer, and an uncured thermosetting adhesive is applied to the back of the second louver layer to form a back-side adhesive layer. KE1825 [manufactured by Shin-Etsu Chemical Co., Ltd.: product name] is used for each thermosetting adhesive.

[0066] Next, the opposing surfaces of the first and second venetian blind layers are bonded to each other, and the surface film layer and the back film layer are laminated on the thermosetting adhesive that becomes the surface side adhesive layer or the back side adhesive layer, and all the thermosetting adhesives are thermally cured to form an interlayer adhesive layer, a surface side adhesive layer, and a back side adhesive layer with a thickness of 0.02 mm, respectively. At this time, the first and second venetian blind layers are laminated and bonded in a manner that the length direction of the shading tape is orthogonal at an angle of 90°. The surface film layer and the back film layer are respectively commercially available polycarbonate resin films with a thickness of 0.2 mm. In addition, the Shore A hardness of the interlayer adhesive layer, the surface side adhesive layer, and the back side adhesive layer formed was measured using a type A micrometer using a test piece in accordance with JIS K 6253-3, and the result was 30. As a specific measuring device, an Asker rubber hardness meter type A [manufactured by Polymer Instruments Co., Ltd.: product name] was used.

[0067] After thermal curing, unnecessary portions of the front and back film layers were removed to produce a thin light transmission direction control sheet with a viewing angle of 90°. The overall light transmittance of the produced light transmission direction control sheet was measured to be 48%, a satisfactory result. In an apparatus using a D65 light source as specified in JIS Z 8720, where a light sensor measures the intensity of inspection light emitted from the light source, the light transmittance is calculated using the formula: Light transmittance = (B / A) × 100 (unit: %). The output value of the light sensor when the light transmission direction control sheet is not in the inspection light path is defined as A, and the output value when the light transmission direction control sheet is placed in the inspection light path and the light transmitted by the light transmission direction control sheet is received by the light sensor is defined as B.

[0068] The refractive indices of the light-transmitting bands of the first and second louver layers in the manufactured light transmission direction control sheet were measured and found to be 1.42, respectively. Furthermore, the refractive indices of the interlayer adhesive layer, the front-side adhesive layer, and the back-side adhesive layer were 1.41, respectively, and the refractive indices of the front film layer and the back film layer were 1.58, respectively. These refractive indices were measured using a refractometer in accordance with JIS K 7142. A multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) with a measurement wavelength of 589 nm was used as the refractometer.

[0069] (Comparative Example) To manufacture Figure 9 、 Figure 10 The light transmission direction control sheet shown is first prepared by first preparing the first louver layer of the first louver layer group. The first louver layer is the same as the first louver layer of the embodiment. After the first louver layer is prepared, a thermosetting adhesive having a thickness of 0.02 mm is applied to both the front and back surfaces of the first louver layer to form an adhesive layer, and a surface film layer and a first internal film layer are laminated on these thermosetting adhesives and thermally cured to prepare the first louver layer group. The thermosetting adhesive used is KE1825 [product name manufactured by Shin-Etsu Chemical Co., Ltd.]. In addition, the surface film layer and the first internal film layer are respectively commercially available polycarbonate resin films with a thickness of 0.2 mm.

[0070] Next, the second louver layer group was manufactured in the same manner as the first louver layer group. A thermosetting adhesive having a thickness of 0.02 mm was applied to the surface of the second inner film layer of the second louver layer group to serve as an adhesive layer. The first inner film layer of the first louver layer group was laminated and bonded perpendicularly to the second inner film layer, and the adhesive layer was thermally cured to manufacture the second louver layer group. Figure 9 or Figure 10 The light transmission direction control sheet having the thickness shown was measured. The light transmittance of the entire light transmission direction control sheet was measured by the same method as in the examples. The result showed that the light transmittance of the entire sheet was only 42%, and improvement was required.

[0071] Industrial applicability The light transmission direction control sheet and the manufacturing method thereof of the present invention are used in the manufacturing fields of detection devices, image display devices, medical equipment such as drip devices, liquid crystal displays, CIDs, water meters, etc.

[0072] Explanation of symbols 1Light transmission direction control sheet 2. First blinds layer 2A Second Louver Floor 3 light transmission bands 4 shading tape 5 interlayer bonding layer 6 Surface film layer 7 Surface side adhesive layer 8 back film layer 9 Back side adhesive layer 10 Workpiece (irradiated object) 11 Detection device 12 light sources 13 detection sensors 14Liquid (irradiated object) 20 Dashboard 21 Image display device 30 Light transmission direction control sheet 31 First Louver Layer Group 31A second louver layer group 33 adhesive layer.

Claims

1. A light transmission direction control sheet comprising: first and second opposing louver layers, an interlayer adhesive layer bonding the first and second louver layers, a light-transmitting surface film layer facing the surface of the first louver layer, a front-side adhesive layer bonding the first louver layer and the surface film layer, a light-transmitting back film layer facing the back of the second louver layer, and a back-side adhesive layer bonding the second louver layer and the back film layer, wherein the first and second louver layers are cross-laminated, and characterized in that: The first and second louver layers are formed by alternating a plurality of light-transmitting bands and light-blocking bands, each of which is formed of light-transmitting silicone rubber, and each of which is formed of colored silicone rubber, wherein the Shore A hardness of these silicone rubbers is not less than 73 and not more than 83 when measured using a Type A durometer in accordance with JIS K6253. The interlayer adhesive layer, the front side adhesive layer, and the back side adhesive layer are each formed of an adhesive silicone rubber, and have a Shore A hardness of 10 to 60 when measured using a type A durometer in accordance with JIS K 6253. At least the thickness of the interlayer adhesive layer is 10 to 30 μm.

2. The light transmission direction control sheet according to claim 1, wherein It is installed on the light source of the detection device that irradiates light to the irradiated object and controls the optical path of the light.

3. The light transmission direction control sheet according to claim 1, wherein: It is integrated with the image display device of the vehicle to control the optical path of the light.

4. The light transmission direction control sheet according to claim 1, 2 or 3, wherein: When measured with a refractometer in accordance with JIS K 7142, the difference in refractive index between the first and second louver layers and the interlayer adhesive layer is 0.02 or less.

5. The light transmission direction control sheet according to claim 1, 2 or 3, wherein: The silicone rubber of the first and second louver layers has a tensile strength of 7.5 MPa to 13.5 MPa when measured in accordance with JIS K 6251, an elongation at break when measured in accordance with JIS K 6251 of 270% to 490%, and a tear strength of 8 kN / m to 28 kN / m when measured in accordance with JIS K 6252.

6. A method for manufacturing a light transmission direction control sheet, the method for manufacturing a light transmission direction control sheet according to claim 1, 2 or 3, characterized in that: A plurality of silicone rubber sheets for light-transmitting bands and silicone rubber sheets for light-shielding bands are alternately stacked to form a stacked body, which is pressurized and then cut to form the first and second louver layers. Adhesive silicone rubber is applied to the opposing surfaces of the first and second louver layers, the exposed surface of the first louver layer, and the exposed back surface of the second louver layer, respectively, so that the first and second louver layers are cross-stacked and bonded, and an adhesive surface film layer is stacked on the surface of the first louver layer, and an adhesive back film layer is stacked on the back surface of the second louver layer.

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