Lighting sheet

Abstract

To provide a daylighting sheet capable of achieving both daylighting properties and heat shielding properties.SOLUTION: A daylighting sheet 10 includes a light control layer 1 having an incident surface S1 and an emission surface S2 facing the incident surface, in which the light control layer includes a light transmissive portion 3 having a plurality of groove portions 2 on the emission surface, an infrared absorbing portion 4 disposed in the groove portion, and a reflective film 5 disposed on one side surface of two facing side surfaces of the groove portion, the reflective film intersects the incident surface and the emission surface and is disposed to be inclined with respect to a normal direction of the incident surface, and the plurality of groove portions are disposed to be separated from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a daylighting sheet. [Background technology]

[0002] In recent years, as environmental problems such as global warming have become more serious, there has been progress in the development and use of daylighting sheets that adjust the absorption, deflection, reflection, transmission, etc. of external light and control the amount of incident light, with the aim of saving energy and reducing CO2 emissions.

[0003] For example, Patent Document 1 discloses a daylighting sheet that is composed of light-transmitting sections that transmit light and a plurality of light-deflecting sections that are arranged in one direction within the sheet and are disposed between the light-transmitting sections and filled with a material that has a lower refractive index than the light-transmitting sections. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-126713 Summary of the Invention [Problem to be solved by the invention]

[0005] Daylighting sheets are used by being placed on windows in buildings, automobiles, etc. However, because windows have poor insulation performance and a lot of heat enters and leaves through the windows, heat loss is a problem.

[0006] The present invention has been made in view of the above circumstances, and has as its main object to provide a daylighting sheet that can achieve both daylighting and heat insulation properties. [Means for solving the problem]

[0007] One embodiment of the present disclosure provides a daylighting sheet having a light control layer with an incident surface and an exit surface opposite the incident surface, wherein the light control layer has a light-transmitting section with a plurality of grooves on the exit surface, an infrared absorbing section arranged within the grooves, and a reflective film arranged on one of two opposing side surfaces of the grooves, the reflective film intersecting the incident surface and the exit surface and arranged at an angle with respect to the normal direction of the incident surface, and the plurality of grooves are arranged at a distance from each other. [Effects of the Invention]

[0008] The present invention has the effect of achieving both light transmission and heat insulation properties. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 3] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 5] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 7] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. [Figure 8] 1A to 1C are process diagrams illustrating a method for forming a light control layer of a daylighting sheet according to the present disclosure. [Figure 9] 1A to 1C are process diagrams illustrating a method for forming a light control layer of a daylighting sheet according to the present disclosure. [Figure 10] 1 is a schematic cross-sectional view illustrating a daylighting sheet according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0011] In this specification, when describing a mode in which another component is placed on a certain component, the term "above" or "below" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the term "on the surface side" or "on the surface" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween.

[0012] In this specification, the term "sheet" also includes members called "film" and "plate."

[0013] The daylighting sheet of the present disclosure will be described in detail below.

[0014] The daylighting sheet of the present disclosure is a daylighting sheet having a light control layer with an incident surface and an exit surface opposite the incident surface, wherein the light control layer has a light-transmitting section with a plurality of grooves on the exit surface, an infrared absorbing section arranged within the grooves, and a reflective film arranged on one of the two opposing side surfaces of the grooves, the reflective film intersecting the incident surface and the exit surface and arranged at an angle with respect to the normal direction of the incident surface, and the plurality of grooves are arranged at a distance from each other.

[0015] Fig. 1 is a schematic cross-sectional view showing an example of a daylighting sheet according to the present disclosure. As shown in Fig. 1, daylighting sheet 10 has a light control layer 1 having an incident surface S1 on which light enters and an exit surface S2 opposite to the incident surface S1 and from which light exits. Light control layer 1 has a light-transmitting section 3 having multiple grooves 2 on the exit surface S2, an infrared absorbing section 4 disposed within the grooves 2, and a reflective film 5 disposed on one of the two opposing side surfaces S11, S12 of grooves 2, namely, side surface S11. Reflective film 5 intersects with incident surface S1 and exit surface S2 and is disposed at an angle with respect to the normal direction D of incident surface S1. The multiple grooves 2 are disposed spaced apart from one another.

[0016] The altitude of the sun at noon varies depending on the location, i.e., latitude. The altitude is highest at the summer solstice and lowest at the winter solstice. The altitude of the sun at noon is calculated using the following formula: The altitude at noon at the summer solstice θ1 = 90 - latitude + 23.4 The meridian altitude at the time of the vernal and autumnal equinoxes is θ2 = 90 - latitude The noon altitude at the winter solstice is θ3 = 90 - latitude - 23.4

[0017] FIG. 2 is a schematic diagram illustrating the path of sunlight at the summer solstice. The meridian altitude θ1 is highest at the summer solstice. When the daylighting sheet 10 is positioned so that the normal direction D of the light control layer 1 is horizontal, the incident angle θ11 of sunlight L1, L2, and L3 with respect to the incident surface S1 of the light control layer 1 is equal to the meridian altitude θ1 at the summer solstice. When sunlight L1, L2, and L3 enters the incident surface S1 of the light control layer 1, the high incident angle θ11 allows almost all sunlight L1, L2, and L3 to reach the infrared absorbing section 4, and the infrared rays in the sunlight L1, L2, and L3 are absorbed. This reduces the amount of infrared rays that reach the exit surface S2 of the light control layer 1. This improves heat insulation. This suppresses indoor temperature increases and improves cooling efficiency.

[0018] On the other hand, with respect to sunlight L1, L2, and L3 that reaches the infrared absorbing portion 4, the infrared rays in the sunlight L1, L2, and L3 are absorbed, but the light rays other than the infrared rays in part of the sunlight L3, i.e., visible light, are reflected by the reflective film 5 and reach the exit surface S2 of the light control layer 1. As a result, a sufficient amount of light can be obtained. As a result, daytime lighting efficiency can be improved. In this way, in the summer, heat blocking properties can be improved without impairing light-transmitting properties.

[0019] FIG. 3 is a schematic diagram illustrating the path of sunlight at the winter solstice. The meridian altitude θ3 is lowest at the winter solstice. When the daylighting sheet 10 is positioned so that the normal direction D of the light control layer 1 is horizontal, the incident angle θ13 of sunlight L1, L2, and L3 with respect to the incident surface S1 of the light control layer 1 is equal to the meridian altitude θ3 at the winter solstice. When sunlight L1, L2, and L3 enters the incident surface S1 of the light control layer 1, the low incident angle θ13 causes some sunlight L1 and L2 to pass through the infrared absorbing sections 4 and reach the exit surface 2 of the light control layer 1. This increases the amount of infrared light reaching the exit surface S2 of the light control layer 1. This reduces the heat-shielding effect and actively utilizes the heat generated by sunlight. This increases the indoor temperature and improves heating efficiency.

[0020] On the other hand, some of the sunlight L3 reaches the infrared absorbing sections 4, but light rays other than infrared rays in the sunlight L3, i.e., visible light rays, reach the exit surface S2 of the light control layer 1. As described above, some of the sunlight L1 and L2 passes through the infrared absorbing sections 4 and reaches the exit surface 2 of the light control layer 1. This increases the amount of light that is taken in. This in turn improves daytime lighting efficiency. In this way, in winter, the light taking effect is high and the heat blocking effect is low.

[0021] FIG. 4 is a schematic diagram illustrating the path of sunlight at the vernal and autumnal equinoxes. The noon altitude θ2 at the vernal and autumnal equinoxes is midway between the noon altitude θ1 at the summer solstice and the noon altitude θ3 at the winter solstice. When the daylighting sheet 10 is positioned so that the normal direction D of the light control layer 1 is horizontal, the incident angle θ12 of sunlight L1, L2, and L3 with respect to the incident surface S1 of the light control layer 1 is equal to the noon altitude θ2 at the vernal and autumnal equinoxes. When sunlight L1, L2, and L3 enters the incident surface S1 of the light control layer 1, the incident angle θ12 is lower than the incident angle θ11 in FIG. 2 but higher than the incident angle θ13 in FIG. 3. Therefore, some sunlight L3 reaches the infrared absorbing section 4, and the infrared rays in sunlight L3 are absorbed. This reduces the amount of infrared rays reaching the exit surface S2 of the light control layer 1. This provides heat-shielding properties.

[0022] On the other hand, with respect to the sunlight L3 that reaches the infrared absorbing sections 4, the infrared rays in the sunlight L3 are absorbed, but the light rays other than the infrared rays in the sunlight L3, i.e., visible light, are reflected by the reflective film 5 and reach the exit surface S2 of the light control layer 1. Furthermore, some of the sunlight L1 and L2 passes through between the infrared absorbing sections 4 and reaches the exit surface 2 of the light control layer 1. As a result, a sufficient amount of light can be obtained. As a result, the daytime lighting efficiency can be improved.

[0023] Thus, in the present disclosure, the light control layer has an infrared absorbing portion, which allows the heat-blocking effect to be adjusted by taking advantage of the seasonal differences in metropolitan altitude. Furthermore, in the present disclosure, the light control layer has multiple grooves spaced apart from one another, i.e., multiple infrared absorbing portions spaced apart from one another, which allows some sunlight to pass through when the angle of incidence is low, thereby enhancing the daylighting effect. Furthermore, in the present disclosure, the light control layer has a reflective film, which intersects the incident surface and the exit surface and is arranged at an angle with respect to the normal direction of the incident surface. Therefore, when the angle of incidence is high, some visible light in the sunlight can be reflected by the reflective film, thereby enhancing the daylighting effect. Therefore, it is possible to achieve both a heat-blocking effect and a daylighting effect.

[0024] 2 to 4 have been explained using examples of the noon altitude for each season, but the altitude of the sun also varies depending on the time of day. The altitude of the sun is highest around noon. Therefore, for example, in spring or autumn, the altitude of the sun is high around noon, so heat-blocking and light-transmitting properties can be obtained. On the other hand, the altitude of the sun is low in the morning and evening, so the heat-blocking effect can be reduced while the light-transmitting property can be increased. Therefore, the heat-blocking effect can be adjusted by taking advantage of the fact that the altitude of the sun varies depending on the time of day.

[0025] Furthermore, although the explanation has been given in connection with FIGS. 2 to 4 using sunlight as an example, the heat-shielding effect can also be adjusted in the same manner as described above in the case of heat ray wavelength ranges including infrared rays.

[0026] Furthermore, in the present disclosure, the light control layer has a reflective film that intersects the incident surface and the exit surface and is disposed at an angle relative to the normal direction of the incident surface, thereby blocking the view from the diagonally downward direction d1, as shown in Figures 2 to 4. This makes it difficult for the state of the room to be seen from outside, and also ensures privacy.

[0027] Each component of the daylighting sheet according to the present disclosure will be described below.

[0028] A. Light control layer The light control layer according to the present disclosure has an incident surface and an exit surface, a light transmitting section having a plurality of grooves on the exit surface, an infrared absorbing section disposed within the grooves, and a reflective film disposed on one of two opposing side surfaces of the grooves.

[0029] 1.Light transmission part (1) Characteristics of the light-transmitting part The light-transmitting portion has light transmittance. Specifically, the total light transmittance of the light-transmitting portion is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The total light transmittance of the light-transmitting portion is measured in accordance with JIS K7361-1:1997.

[0030] The refractive index of the light-transmitting portion is not particularly limited, and may be approximately 1.5, which is a general refractive index for resin. The refractive index of the light-transmitting portion is, for example, 1.3 or more and 1.7 or less. The refractive index of the light-transmitting portion is measured in accordance with Method A of JIS K7142:2014 using an Abbe refractometer at a temperature of 23°C and a sodium light source with a measurement wavelength of 589 nm. The same method is used to measure the refractive index of other components.

[0031] (2) Material of the light-transmitting part The resin constituting the light-transmitting portion is not particularly limited as long as it satisfies the above total light transmittance, and resins generally used in the field of transparent sheets can be used. Examples of resins used in the light-transmitting portion include curable resins and thermoplastic resins. Examples of curable resins include thermosetting resins and ionizing radiation curable resins. Examples of ionizing radiation curable resins include ultraviolet curable resins, electron beam curable resins, visible light curable resins, and near-infrared curable resins. Examples include acrylic resins and polycarbonates.

[0032] The light-transmitting portion may contain additives as needed, such as ultraviolet absorbers, light stabilizers, antioxidants, polymerization initiators, crosslinking agents, curing agents, hard coating agents, fillers, polymerization inhibitors, antistatic agents, leveling agents, thixotropy-imparting agents, coupling agents, plasticizers, antifoaming agents, and fillers.

[0033] (3) Groove The light transmitting portion has a plurality of grooves on the exit surface, the grooves being arranged on the exit surface of the light transmitting portion so as to extend in a direction intersecting the entrance surface and the exit surface.

[0034] The cross-sectional shape of the groove may be any shape as long as the side constituting one of the two opposing side surfaces of the groove intersects with the incident surface and the exit surface and is inclined with respect to the normal direction of the incident surface. The cross-sectional shape of the groove is the same as the cross-sectional shape of the infrared absorbing portion described below.

[0035] The shape of the grooves in plan view is not particularly limited and may be the same as the shape of the infrared absorbing portion in plan view, which will be described later.

[0036] The depth of the grooves is the same as the thickness of the infrared absorbing portions described below. The width of the grooves on the light emitting surface side is the same as the width of the infrared absorbing portions described below. The arrangement of the grooves is the same as the arrangement of the infrared absorbing portions described below.

[0037] 2. Infrared absorbing part The infrared absorbing portion is disposed in the groove of the light transmitting portion.

[0038] (1) Characteristics of the infrared absorbing part The infrared absorbing portion has infrared absorbing properties. In particular, the infrared absorbing portion preferably absorbs near-infrared rays, more preferably in the wavelength range of 1000 nm to 3000 nm. Specifically, the average transmittance of the infrared absorbing portion in the wavelength range of 1000 nm to 2000 nm is preferably 30% or less, more preferably 15% or less, and even more preferably 10% or less. If the average transmittance is within the above range, a high heat-shielding effect can be obtained.

[0039] Furthermore, the infrared absorbing portion usually has visible light transmittance. Specifically, the visible light transmittance of the infrared absorbing portion is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. If the visible light transmittance is within the above range, high light-collecting properties can be obtained. The visible light transmittance is the average value of the transmittance in the wavelength range of 380 nm or more and 780 nm or less.

[0040] The method for measuring the transmittance of the infrared absorbing portion is as follows. First, a measurement infrared absorbing portion is formed on a glass substrate. The thickness of the measurement infrared absorbing portion is set to be the same as the thickness T1 of the infrared absorbing portion in the daylighting sheet. Next, the transmittance of the measurement infrared absorbing portion is measured using a spectrophotometer.

[0041] The refractive index of the infrared absorbing portion is preferably small in difference from the refractive index of the light transmitting portion, and more preferably approximately the same as the refractive index of the light transmitting portion. This can suppress reflection of sunlight at the interface between the light transmitting portion and the infrared absorbing portion. Therefore, the heat-shielding effect of the infrared absorbing portion can be enhanced. The refractive index of the infrared absorbing portion is the same as the refractive index of the light transmitting portion.

[0042] (2) Infrared absorbing material The material of the infrared absorbing portion is not particularly limited as long as it has the above-mentioned infrared absorbing properties and visible light transmittance. The infrared absorbing portion preferably contains a resin and an infrared absorbing agent.

[0043] The infrared absorbing agent is not particularly limited as long as it has the above-mentioned infrared absorbing properties, and may be an inorganic material or an organic material. Among these, inorganic materials are preferred from the viewpoint of durability.

[0044] Examples of inorganic materials include tungsten oxides such as cesium-doped tungsten oxide (CWO), indium oxide, tin-doped indium oxide (ITO), tin oxide, antimony-doped tin oxide (ATO), titanium oxide, zinc oxide, zirconium oxide, tantalum oxide, niobium oxide, ruthenium oxide, cesium oxide, zinc sulfide, and metal borides such as lanthanum hexaboride (LaB6). Furthermore, inorganic pigments are preferred as inorganic materials. Of these, cesium-doped tungsten oxide (CWO) is preferred.

[0045] The content of the infrared absorber in the infrared absorbing section is appropriately determined taking into consideration the balance between the desired visible light transmittance and the amount of infrared attenuation. Light in the near-infrared region is attenuated as it passes through the infrared absorbing section in the thickness direction of the infrared absorbing section. When the infrared absorber is CWO, for example, if the above-mentioned visible light transmittance is 70%, the transmittance in the near-infrared region can be kept to 20% or less. When the infrared absorber is CWO, the content of the infrared absorber in the infrared absorbing section is preferably 2% by mass or more and 25% by mass or less, taking into consideration the compatibility between the inorganic pigment and the resin or additives so as to prevent aggregation of the inorganic pigment.

[0046] The resin constituting the infrared absorbing portion is not particularly limited as long as it is a resin that transmits visible light, and resins generally used in the field of transparent sheets can be used. Examples of resins used in the infrared absorbing portion include curable resins. Examples of curable resins include thermosetting resins and ionizing radiation curable resins. Examples of ionizing radiation curable resins include ultraviolet curable resins, electron beam curable resins, visible light curable resins, and near-infrared curable resins. Examples include acrylic resins and polycarbonates.

[0047] Furthermore, it is preferable that the type of resin contained in the infrared absorbing portion is the same as the type of resin contained in the light transmitting portion. This makes it possible to reduce the difference in refractive index between the infrared absorbing portion and the light transmitting portion. The same type of resin means that the main chemical structure is the same. For example, when the light transmitting portion contains an acrylic resin, it is preferable that the infrared absorbing portion also contains an acrylic resin. Furthermore, when the light transmitting portion contains polycarbonate, it is preferable that the infrared absorbing portion also contains polycarbonate.

[0048] The infrared absorbing portion may contain additives, such as a polymerization initiator, a crosslinking agent, and a curing agent, if necessary.

[0049] (3) Shape of infrared absorbing part The cross-sectional shape of the infrared absorbing portion is the same as the cross-sectional shape of the groove portion. The cross-sectional shape of the infrared absorbing portion may be any shape as long as the side constituting one of the two opposing side surfaces of the infrared absorbing portion intersects with the incident surface and the exit surface and is inclined with respect to the normal direction of the incident surface. Examples of the cross-sectional shape of the infrared absorbing portion include a triangle and a trapezoid. In FIG. 1, the cross-sectional shape of the infrared absorbing portion 4 is a triangle. In FIG. 5(a), the cross-sectional shape of the infrared absorbing portion 4 is a trapezoid. Furthermore, as shown in FIGS. 5(b) and 5(c), the cross-sectional shape of the infrared absorbing portion 4 may be a tapered shape in which the oblique side constituting one of the two opposing side surfaces S21 and S22 of the infrared absorbing portion 4 is composed of two or more straight or curved lines.

[0050] In the cross section of the infrared absorbing section, one of the two opposing side surfaces of the infrared absorbing section intersects with the incident surface and the exit surface and is inclined with respect to the normal to the incident surface. Hereinafter, this side surface may be referred to as the inclined side surface. The angle of the inclined side surface of the infrared absorbing section with respect to the normal to the incident surface is the same as the angle with respect to the normal to the incident surface of the reflective film described below. The angle of the inclined side surface of the infrared absorbing section with respect to the normal to the incident surface is not particularly limited as long as it can achieve both heat-blocking and daylighting functions, and is adjusted appropriately depending on the noon altitude θ3 at the winter solstice in the location where the daylighting sheet is used and the refractive index of the light-transmitting section. The angle of the incident surface of the reflective film with respect to the normal will be described later.

[0051] 2 and 3, the angle of the inclined side surface S21 of the infrared absorbing portion 4 with respect to the normal direction D of the incident surface S1 is indicated by θa. Also, in FIG. 2 and 3, the angle of the incident surface S1 of the reflective film 5 with respect to the normal direction D is indicated by θb.

[0052] Furthermore, in the cross section of the infrared absorbing portion, the other of the two opposing side surfaces of the infrared absorbing portion, which is not the inclined surface, intersects with the incident surface and the exit surface. Hereinafter, this side surface may be referred to as the "opposing side surface." The opposing side surface of the infrared absorbing portion may be parallel to the normal direction of the incident surface or may be inclined with respect to the normal direction of the incident surface. It is preferable that the opposing side surface of the infrared absorbing portion be parallel to the normal direction of the incident surface. Furthermore, when the opposing side surface of the infrared absorbing portion is inclined with respect to the normal direction of the incident surface, as shown in FIG. 5(d), it is preferable that the opposing side surface S22 of the infrared absorbing portion 4 be inclined on the same side as the inclined side surface S21 of the infrared absorbing portion 4 with respect to the normal direction D of the incident surface S1. Since the infrared absorbing portion contains an infrared absorbent, the infrared absorbing portion may have a color due to the infrared absorbent. In this case, when observing the incident surface side from the exit surface side, the color of the scenery may change, such as appearing bluish. As shown in FIG. 6(c), when the facing side surface S22 of the infrared absorbing unit 4 is inclined with respect to the normal direction D of the incident surface S1 and is inclined on the opposite side to the inclined side surface S21 of the infrared absorbing unit 4 with respect to the normal direction D of the incident surface S1, when the incident surface S1 side is observed from the exit surface S2 side, the portion seen through the infrared absorbing unit 4 is colored. In this case, since the portion seen through the infrared absorbing unit 4 increases, the color of the scenery is likely to change. On the other hand, as shown in FIG. 6(a), when the facing side surface S22 of the infrared absorbing unit 4 is parallel to the normal direction D1 of the incident surface S1, when the incident surface S1 side is observed from the exit surface S2 side, the portion seen through the infrared absorbing unit 4 decreases, so the change in the color of the scenery can be suppressed. 6(b), in the case where the opposing side surface S22 of the infrared absorbing part 4 is inclined with respect to the normal direction D of the incident surface S1 and the opposing side surface S22 of the infrared absorbing part 4 is inclined on the same side as the inclined side surface S21 of the infrared absorbing part 4 with respect to the normal direction D of the incident surface S1, when the incident surface S1 side is observed from the exit surface S2 side, the portion that can be seen through the infrared absorbing part 4 becomes smaller, thereby suppressing changes in the color of the scenery. This makes it possible to suppress the viewer from feeling uncomfortable.

[0053] In particular, it is preferable that the opposing side surfaces of the infrared absorbing portion are parallel to the normal direction of the incident surface, because this makes it easier to form a reflective film when forming a light control layer by the manufacturing method for a light control layer described later.

[0054] The angle formed between the opposing side surfaces of the infrared absorbing portion and the normal direction to the incident surface is preferably 0±5°, and more preferably 0°.

[0055] The shape of the infrared absorbing portion in plan view is not particularly limited, and may be, for example, a straight line or a curved line.

[0056] The thickness T1 of the infrared absorbing portion is the same as the depth of the grooves. The thickness T1 of the infrared absorbing portion is not particularly limited as long as it can achieve both heat-shielding and daylighting functions, and is adjusted appropriately depending on the noon altitude θ1 at the summer solstice where the daylighting sheet is used, the angle θa of the inclined side of the infrared absorbing portion relative to the normal to the incident surface, and the refractive index of the light-transmitting portion. For example, in Figure 2, when the refractive index of air is n1, the refractive index of the light-transmitting portion 3 is n2, and the incident angle is θ11, the refraction angle θ21 can be calculated using the following formula: n2 / n1=sinθ11 / sinθ21 The thickness T1 of the infrared absorbing portion 4 is preferably set so that sunlight L1 with an incident angle θ11 reaches the infrared absorbing portion 4 after being refracted at a refraction angle θ22. Specifically, when a right-angled triangle is drawn with the line segment P1P2 as the hypotenuse and the angle of the hypotenuse as the refraction angle θ21, the thickness T1 of the infrared absorbing portion 4 is preferably the length A1±(A1 / 20) μm of the adjacent side of the right-angled triangle, and more preferably the length A1 of the adjacent side of the right-angled triangle. In this case, almost all sunlight L1, L2, and L3 can reach the infrared absorbing portion 4. This reduces the amount of sunlight that passes through the infrared absorbing portion 4 and reaches the exit surface S2. This improves the heat-shielding effect. A high heat-shielding effect is desirable in summer, so this design is preferable.

[0057] For example, assuming that the refractive index n1 of air is 1 and the refractive index n2 of the light-transmitting portion 3 is 1.5, the thickness T1 of the infrared absorbing portion relative to the width W1 of the light-emitting surface side of the infrared absorbing portion is preferably within the range shown below. The latitude of the Tokyo area is 35°, the meridian altitude at the summer solstice is 78.4°, and the meridian altitude at the winter solstice is 31.6°. In this case, the thickness T1 of the infrared absorbing portion is preferably, for example, W1×3 or more and W1×3.3 or less, and more preferably approximately W1×3. The latitude of the Sapporo area is 43°, the meridian altitude at the summer solstice is 70.4°, and the meridian altitude at the winter solstice is 23.6°. In this case, the thickness T1 of the infrared absorbing portion is preferably, for example, W1×3.7 or more and W1×4 or less, and more preferably approximately W1×3.7. The latitude of the Naha area is 26°, the meridian altitude at the summer solstice is 87.4°, and the meridian altitude at the winter solstice is 40.6°. In this case, the thickness T1 of the infrared absorbing part is, for example, preferably W1 × 2.2 or more and W1 × 2.5 or less, and more preferably about W1 × 2.2. If the thickness of the infrared absorbing part is within the above range, it is possible to achieve a good balance between the heat-shielding function and the lighting function.

[0058] Furthermore, the thickness T1 of the infrared absorbing portion is preferably thinner than the thickness of the light control layer. Specifically, the thickness of the infrared absorbing portion may be 50% to 98% or 70% to 98% of the thickness of the light control layer (100%).

[0059] The thickness of the infrared absorbing portion is the length from the exit surface of the light control layer to the tip of the infrared absorbing portion on the incident surface side. The thickness of the infrared absorbing portion is indicated by T1 in Fig. 2, for example. The width of the infrared absorbing portion on the exit surface side is indicated by W1 in Fig. 7, for example.

[0060] The width W1 of the infrared absorbing section on the exit surface side is the width of the groove on the exit surface side. The width W1 of the infrared absorbing section on the exit surface side is not particularly limited as long as it can achieve both heat-shielding and daylighting functions, and is adjusted appropriately depending on the summer solstice noon altitude θ1 and winter solstice noon altitude θ3 of the location where the daylighting sheet will be used, as well as the refractive index of the light-transmitting section. For example, in Figure 3, when the refractive index of air is n1, the refractive index of the light-transmitting section 3 is n2, and the angle of incidence is θ13, the refraction angle θ23 can be calculated using the following formula: n2 / n1=sinθ13 / sinθ23

[0061] For example, the latitude near Tokyo is 35°, the meridian altitude at the summer solstice is 78.4°, and the meridian altitude at the winter solstice is 31.6°. For example, if the refractive index n1 of air is 1 and the refractive index n2 of the light-transmitting portion 3 is 1.5, the refraction angle θ23 at the winter solstice is 20.01°. When the angle θa of the inclined side surface of the infrared absorbing portion relative to the normal to the incident surface is equal to the refraction angle θ23, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the infrared absorbing portion on the exit surface side is 2.727. Therefore, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the infrared absorbing portion on the exit surface side is preferably 2.32 to 3.14, more preferably 2.45 to 3.0, and even more preferably 2.59 to 2.86.

[0062] The latitude near Sapporo is 43°, the meridian altitude at the summer solstice is 70.4°, and the meridian altitude at the winter solstice is 23.6°. For example, if the refractive index n1 of air is 1 and the refractive index n2 of the light-transmitting portion 3 is 1.5, the refraction angle θ23 at the winter solstice is 15.29°. When the angle θa of the inclined side surface of the infrared absorbing portion relative to the normal to the incident surface is equal to the refraction angle θ23, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the infrared absorbing portion on the exit surface side is 3.659. Therefore, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the infrared absorbing portion on the exit surface side is preferably, for example, 3.11 or more and 4.21 or less, more preferably 3.29 or more and 4.03 or less, and even more preferably 3.48 or more and 3.84 or less.

[0063] The latitude near Naha is 26°, the meridian altitude at the summer solstice is 87.4°, and the meridian altitude at the winter solstice is 40.6°. For example, if the refractive index n1 of air is 1 and the refractive index n2 of the light-transmitting portion 3 is 1.5, the refraction angle θ23 at the winter solstice is 24.86°. When the angle θa of the inclined side surface of the infrared absorbing portion relative to the normal to the incident surface is equal to the refraction angle θ23, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the exit surface side of the infrared absorbing portion is 2.158. Therefore, the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the exit surface side of the infrared absorbing portion is preferably, for example, 1.83 to 2.48, more preferably 1.94 to 2.37, and even more preferably 2.05 to 2.27.

[0064] If the ratio of the thickness T1 of the infrared absorbing portion to the width W1 of the infrared absorbing portion on the emission surface side is within the above range, the heat shielding function and the lighting function can be achieved in a balanced manner.

[0065] The infrared absorbing portions are spaced apart from one another. The infrared absorbing portions may be arranged at equal intervals or at intervals that vary in part. The intervals between the infrared absorbing portions are the same as the intervals between the grooves.

[0066] The spacing between the infrared absorbing sections is not particularly limited as long as it can achieve both heat-shielding and daylighting functions. It is adjusted appropriately depending on the summer solstice noon altitude θ1 and winter solstice noon altitude θ3 in the location where the daylighting sheet is used. The wider the spacing W2 between the infrared absorbing sections is compared to the width W1 of the infrared absorbing sections on the light-receiving surface side, the more sunlight that passes through the infrared absorbing sections and reaches the light-receiving surface without reaching the infrared absorbing sections, thereby increasing the amount of light and reducing the amount of infrared absorption. For example, in areas with a high noon altitude, less sunlight passes through the infrared absorbing sections, reducing the impact of the spacing W2 between the infrared absorbing sections. On the other hand, in areas with a low noon altitude, more sunlight passes through the infrared absorbing sections, reducing the impact of the spacing W2 between the infrared absorbing sections. However, in areas with a low noon altitude, where the heat radiation from summer sunlight is not particularly high, the spacing W2 between the infrared absorbing sections may be widened to allow for the capture of winter sunlight's heat radiation. Thus, the spacing W2 between the infrared absorbing sections is preferably designed to suit the region.

[0067] The ratio of the spacing W2 of the infrared absorbing sections to the width W1 of the infrared absorbing sections on the exit surface side may be, for example, 0.25 to 2, 0.5 to 1.5, or 0.75 to 1. The spacing W2 of the infrared absorbing sections may be, for example, 25 μm to 2000 μm, 50 μm to 1500 μm, or 75 μm to 1000 μm. If the spacing of the infrared absorbing sections is greater than a predetermined value, sunlight can be secured to pass through the infrared absorbing sections and reach the exit surface when the solar noon altitude is low. Furthermore, if the spacing of the infrared absorbing sections is less than a predetermined value, sunlight can be secured to reach the infrared absorbing sections. Therefore, a good balance can be achieved between the heat-shielding function and the light-collecting function. Furthermore, as described above, the infrared absorbing section contains an infrared absorbent, and the infrared absorbing section may have a color due to the infrared absorbent. In this case, when observing the incident surface side from the light-receiving surface side of the daylighting sheet, the scenery may appear to have a bluish tinge, or the color of the scenery may change. If the spacing between the infrared absorbing sections is equal to or less than a predetermined value, even if the infrared absorbing sections have a color, the change in the color of the scenery when observing the incident surface side from the light-receiving surface side can be suppressed. This prevents the viewer from feeling uncomfortable.

[0068] The spacing between the infrared absorbing portions is the distance between the ends of adjacent infrared absorbing portions, and is indicated by W2 in FIG.

[0069] The arrangement of the multiple infrared absorbing sections is not particularly limited. The multiple infrared absorbing sections may be arranged so that they do not intersect with each other, or so that they intersect with each other. In particular, considering the view when observing the incident surface side from the exit surface side of the daylighting sheet, it is preferable that the multiple infrared absorbing sections are arranged so that they do not intersect with each other, and it is more preferable that they are arranged in parallel. Furthermore, the multiple infrared absorbing sections may be arranged regularly or irregularly. In particular, it is preferable that the planar shape of the infrared absorbing section is linear, and that the multiple infrared absorbing sections are arranged regularly in parallel.

[0070] 3.Reflective film The reflective film is disposed on one of two opposing side surfaces of the groove.

[0071] (1) Characteristics of the reflective film The reflective film reflects visible light. The visible light reflectance of the reflective film is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. The method for measuring the visible light reflectance of the reflective film is as follows. First, a reflective film to be measured is formed on a glass substrate. Next, the visible light reflectance of the reflective film to be measured is measured using a spectrophotometer according to the SCI method. As the spectrophotometer, for example, the CM-2500 spectrophotometer manufactured by Konica Minolta can be used. The measurement wavelength range of this spectrophotometer is 360 nm to 740 nm, and the measurement wavelength interval is 10 nm. The measurement conditions are a 2° field of view and a D65 light source.

[0072] The OD (Optical Density) value of the reflective film is preferably 1 or more, and more preferably 2 or more. The OD value indicates the so-called optical density. The OD value of the reflective film is measured as follows. First, a reflective film for measurement is formed on a glass substrate. Next, the OD value of the reflective film for measurement is measured using an optical densitometer.

[0073] (2) Reflective film material The reflective film is not particularly limited as long as it can reflect visible light, and examples thereof include a metal layer and a white layer. Of these, a metal layer is preferred. The specular reflection of the metal layer can improve the light transmission.

[0074] Examples of materials for the metal layer include metals such as aluminum and silver, and alloys thereof. Methods for forming the metal layer include, for example, vapor deposition, sputtering, plating, spray coating, die coating, screen printing, wiping, inkjet printing, and foil transfer. The thickness of the metal layer is not particularly limited and may be appropriately selected depending on the material and forming method, but is, for example, 10 nm or more and 2000 nm or less.

[0075] The white layer contains, for example, a resin and a whitening agent. Examples of the whitening agent include white pigments such as titanium oxide. Examples of the resin include curable resins. Examples of a method for forming the white layer include a method of applying a resin composition containing the resin and the whitening agent and curing it.

[0076] (3) Shape of the reflective film The reflective film is disposed on one of the two opposing side surfaces of the groove. The reflective film intersects with the incident surface and the exit surface and is disposed at an angle with respect to the normal direction of the incident surface. The reflective film reflects light incident from the incident surface toward the exit surface.

[0077] The reflective surface preferably has smoothness in order to reflect a large amount of light. Specifically, the arithmetic mean roughness Ra of the reflective surface is preferably 300 nm or less, more preferably 150 nm or less, and even more preferably 50 nm or less. The smaller the Ra of the reflective surface, the more preferable it is, and the lower limit of Ra is not particularly limited, but from the viewpoint of forming the above-mentioned reflective film, it is, for example, 1 nm or more. By keeping the Ra of the reflective surface within the above range, scattering of light on the reflective surface can be suppressed, and desired light-collecting properties can be obtained.

[0078] The arithmetic mean roughness Ra of the reflecting surface is measured using a non-contact white light interferometer in accordance with JIS B0601: 2013. For example, a Zygo NewView 6200 manufactured by Canon Corporation is used as the non-contact white light interferometer.

[0079] The angle of the reflective film relative to the normal to the incident surface is the same as the angle of the inclined side of the infrared absorbing section relative to the normal to the incident surface. The angle of the reflective film relative to the normal to the incident surface is not particularly limited as long as it can achieve both heat-blocking and daylighting functions, and is adjusted appropriately depending on the noon altitude θ3 at the winter solstice in the location where the daylighting sheet is used and the refractive index of the light-transmitting section. For example, in Figure 3, when the refractive index of air is n1, the refractive index of the light-transmitting section 3 is n2, and the incident angle is θ13, the refraction angle θ23 can be calculated using the following formula: n2 / n1=sinθ13 / sinθ23 The angle θb of the reflective film 5 relative to the normal direction D of the incident surface S1 is preferably set so that sunlight L1 with an incident angle θ13 is not reflected by the reflective film 5 when refracted at a refraction angle θ23. Specifically, the angle θb of the reflective film 5 relative to the normal direction D of the incident surface S1 is preferably the refraction angle θ23±2°, and is preferably equal to the refraction angle θ23. If the angle θb of the reflective film 5 relative to the normal direction D of the incident surface S1 is smaller than the refraction angle θ23 or larger than the refraction angle θ23, sunlight L1 with an incident angle θ13 may be reflected by the reflective film 5 and reach the infrared absorbing section 5, resulting in the infrared ray in the sunlight L1 being absorbed. In this case, the heat-shielding effect is increased. On the other hand, if the angle θb of the reflective film 5 with respect to the normal direction D of the incident surface S1 is equal to the refraction angle θ23, when sunlight L1 at an incident angle θ13 is refracted at the refraction angle θ23, the sunlight L1 can pass through the infrared absorbing parts 4 without being reflected by the reflective film 5 or absorbed by the infrared absorbing parts 4. This increases the amount of infrared light that reaches the exit surface S2. This reduces the heat-shielding effect. This type of design is preferable in winter, when it is desirable to reduce the heat-shielding effect and actively utilize the heat from sunlight.

[0080] For example, assuming that the refractive index n1 of air is 1 and the refractive index n2 of the light-transmitting portion 3 is 1.5, the angle of the reflective film relative to the normal to the incident surface is preferably within the range shown below. The latitude of the Tokyo area is 35°, the meridian altitude at the summer solstice is 78.4°, and the meridian altitude at the winter solstice is 31.6°. In this case, the angle of the reflective film relative to the normal to the incident surface is preferably 20.01±2°, and more preferably 20.01°. The latitude of the Sapporo area is 43°, the meridian altitude at the summer solstice is 70.4°, and the meridian altitude at the winter solstice is 23.6°. In this case, the angle of the reflective film relative to the normal to the incident surface is preferably 15.29±1.5°, and more preferably 15.29°. The latitude of the Naha area is 26°, the meridian altitude at the summer solstice is 87.4°, and the meridian altitude at the winter solstice is 40.6°. In this case, the angle of the reflective film relative to the normal to the incident surface is preferably 24.86±2.5°, and more preferably 24.86°. If the angle of the reflective film relative to the normal to the incident surface is within the above range, a good balance between the heat-shielding function and the lighting function can be achieved.

[0081] For example, in FIGS. 2 and 3, the angle of the incident surface S1 of the reflective film 5 with respect to the normal direction D is indicated as θb.

[0082] 5(b), the cross-sectional shape of the infrared absorbing part 4 may be a tapered shape in which the oblique side constituting one of the two opposing side surfaces S21, S22 of the infrared absorbing part 4 is formed by two or more straight lines. In this case, the reflective film 5 has a plurality of portions each having a different angle with respect to the normal direction D of the incident surface S1. The angle of each portion constituting the reflective film 5 with respect to the normal direction D of the incident surface S1 is preferably smaller the closer to the exit surface. In this case, the angle of each portion constituting the reflective film 5 with respect to the normal direction D of the incident surface S1 is preferably within the above range.

[0083] 5(c), the cross-sectional shape of the infrared absorbing part 4 may be a tapered shape in which the oblique side constituting one side S21 of the two opposing side surfaces S21, S22 of the infrared absorbing part 4 is curved. In this case, the cross-sectional shape of the reflective film 5 is curved. In such a case, it is preferable that the curve be approximated to a straight line, and the angle of this straight line with respect to the normal direction to the incident surface be within the above range.

[0084] 4. Incident and exit surfaces The incident surface is the surface of the light control layer of the daylighting sheet on which light enters, and the exit surface is the surface of the light control layer of the daylighting sheet on which light exits, and is the surface opposite the incident surface.

[0085] 5.Thickness of the light control layer The thickness of the light control layer is not particularly limited as long as it is greater than the depth of the grooves, i.e., the thickness of the infrared absorbing portions. The thickness of the light control layer also varies depending on whether or not a substrate layer, which will be described later, is present. When a substrate layer is disposed on the incident surface of the light control layer, the thickness of the light control layer may be relatively thin as long as it is greater than the depth of the grooves, i.e., the thickness of the infrared absorbing portions. The thickness of the light control layer is, for example, 20 μm or more and 500 μm or less.

[0086] 6. Method for forming light control layer The method for forming the light control layer is not particularly limited. FIGS. 8(a) to 8(f) and 9(a) to 9(b) show an example of a method for forming the light control layer. First, as shown in FIG. 8(a), a light-transmitting section 3 having a plurality of grooves 2 is formed. Next, as shown in FIG. 8(b), a reflective film 5 is formed on the surface of the light-transmitting section 3 facing the grooves 2. Next, as shown in FIG. 8(c), a resist layer 31 is formed in the grooves 2 of the light-transmitting section 3. Next, as shown in FIG. 8(d), the resist layer 31 is exposed to UV parallel light from the surface of the light-transmitting section 3 opposite the grooves 2. Next, as shown in FIG. 8(e), the resist layer 31 is developed. Next, as shown in FIG. 8(f), the reflective film 5 is etched using the resist layer 31 as a mask, and the resist layer 31 is removed as shown in FIG. 9(a). This forms a reflective film 5 on one side of the grooves 2. Next, as shown in FIG. 9(b), a resin composition containing a resin and an infrared absorbing agent is filled into the grooves 2 of the light transmitting portion 3 and cured to form the infrared absorbing portion 4.

[0087] B. Base material layer As shown in Figure 10(a), the daylighting sheet of the present disclosure may have a base layer 6 on the incident surface S1 of the light control layer 1. The base layer supports the light control layer, improving the mechanical strength of the daylighting sheet.

[0088] The refractive index of the base material layer is preferably small in difference from the refractive index of the light-transmitting portion, and more preferably approximately the same as the refractive index of the light-transmitting portion. This makes it possible to suppress reflection of sunlight at the interface between the base material layer and the light-transmitting portion. Therefore, it is possible to improve lighting performance. The refractive index of the base material layer is the same as the refractive index of the light-transmitting portion.

[0089] The substrate layer transmits visible light and infrared rays. The total light transmittance of the substrate layer is the same as that of the light-transmitting portion. The substrate layer is not particularly limited as long as it transmits visible light and infrared rays, and a resin substrate can be used. The type of resin contained in the resin substrate may be the same as the type of resin contained in the light-transmitting portion. The difference between the refractive index of the substrate layer and that of the light-transmitting portion can be reduced. The thickness of the substrate layer is not particularly limited.

[0090] C. Adhesive layer The daylighting sheet of the present disclosure may have an adhesive layer on the incident surface or the exit surface of the light control layer. As shown in FIG. 10(b), when the adhesive layer 7 is disposed on the incident surface S1 of the light control layer 1, and the daylighting sheet 10 is attached to, for example, a window, the daylighting sheet 10 is attached to the indoor side of the window. In this case, heat generated by infrared rays absorbed by the infrared absorbing sections 5 is released into the room. This can further warm the room in winter. On the other hand, as shown in FIG. 10(c), when the adhesive layer 7 is disposed on the exit surface S2 of the light control layer 1, and the daylighting sheet 10 is attached to, for example, a window, the daylighting sheet 10 is attached to the outdoor side of the window. In this case, heat generated by infrared rays absorbed by the infrared absorbing sections 5 is released to the outside. This can further prevent the room from getting too hot in summer.

[0091] The refractive index of the adhesive layer is preferably small in difference from the refractive index of the light-transmitting portion, and more preferably approximately the same as the refractive index of the light-transmitting portion. This can suppress reflection of sunlight at the interface between the adhesive layer and the light-transmitting portion, thereby improving daylighting. The refractive index of the adhesive layer is the same as the refractive index of the light-transmitting portion.

[0092] The adhesive layer transmits visible light and infrared rays. The total light transmittance of the adhesive layer is the same as that of the light-transmitting portion. The adhesive layer is not particularly limited as long as it transmits visible light and infrared rays, and various adhesives can be used. The adhesive may be a pressure-sensitive adhesive. The type of resin contained in the adhesive layer may be the same as the type of resin contained in the light-transmitting portion. The difference between the refractive index of the adhesive layer and the refractive index of the light-transmitting portion can be reduced. The thickness of the adhesive layer is not particularly limited.

[0093] D. Protective layer The daylighting sheet of the present disclosure may have a protective layer on the light-incident or light-exiting surface of the light control layer. This can protect the light control layer. In particular, when the daylighting sheet is attached to the exterior side of a window, for example, the protective layer on the light-incident surface of the light control layer can prevent deterioration of the light control layer.

[0094] The refractive index of the protective layer is preferably small in difference from the refractive index of the light-transmitting portion, and more preferably approximately the same as the refractive index of the light-transmitting portion. This can suppress reflection of sunlight at the interface between the protective layer and the light-transmitting portion, thereby improving light transmission. The refractive index of the protective layer is the same as the refractive index of the light-transmitting portion.

[0095] The protective layer transmits visible light and infrared rays. The total light transmittance of the protective layer is the same as that of the light-transmitting portion. The protective layer is not particularly limited as long as it transmits visible light and infrared rays. The protective layer preferably contains a weathering agent such as an ultraviolet absorber or a light stabilizer to the extent that it does not impair the light-transmitting function. Furthermore, the type of resin contained in the protective layer may be the same as the type of resin contained in the light-transmitting portion. This makes it possible to reduce the difference in refractive index between the protective layer and the light-transmitting portion. The thickness of the protective layer is not particularly limited.

[0096] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention.

[0097] The present disclosure provides the following inventions. [1] A daylighting sheet having a light control layer having an incident surface and an exit surface facing the incident surface, the light control layer has a light transmission section having a plurality of grooves on the light exit surface, an infrared absorption section disposed in the grooves, and a reflective film disposed on one of two opposing side surfaces of the grooves, the reflective film is disposed so as to intersect the incident surface and the exit surface and to be inclined with respect to a normal direction of the incident surface, The daylighting sheet, wherein the plurality of grooves are arranged at a distance from one another. [2] The daylighting sheet according to [1], wherein the infrared absorbing portion contains a resin and an infrared absorbing agent. [3] The daylighting sheet according to [1] or [2], wherein the reflective film is a metal layer. [4] The daylighting sheet according to any one of [1] to [3], wherein the light control layer has an adhesive layer on the incident surface or the exit surface. [Explanation of symbols]

[0098] 1... Light control layer 2 ... Groove 3 … Light transmitting part 4...Infrared absorbing part 5 … Reflective film 10...Lighting sheet S1…Incidence surface S2… Output surface

Claims

1. A daylighting sheet having a light control layer having an incident surface and an exit surface facing the incident surface, the light control layer has a light transmission section having a plurality of grooves on the light exit surface, an infrared absorption section disposed in the grooves, and a reflective film disposed on one of two opposing side surfaces of the grooves, the reflective film intersects the incident surface and the exit surface and is disposed at an angle with respect to a normal direction of the incident surface, The daylighting sheet, wherein the plurality of grooves are arranged at a distance from one another.

2. The daylighting sheet according to claim 1 , wherein the infrared absorbing portion contains a resin and an infrared absorbing agent.

3. The daylighting sheet according to claim 1 or 2, wherein the reflective film is a metal layer.

4. The daylighting sheet according to claim 1 or 2, further comprising an adhesive layer on the incident surface or the exit surface of the light control layer.

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