Surface lighting device, space including surface lighting device, and lighting method

Abstract

Provided are a surface illuminating device with which light flicker is suppressed, a space including said surface illuminating device, and an illumination method. In this surface illuminating device, including a light source and a transparent light-guiding plate for guiding light emitted from the light source, if an axis which passes through the center of a light-emitting surface of the surface illuminating device and which is perpendicular to a floor surface is defined as a perpendicular axis, a direction from the center of the light-emitting surface toward the floor surface, on the perpendicular axis, in a plane including the perpendicular axis and perpendicular to the light-emitting surface is defined as -90°, a direction from the center of the light-emitting surface toward the side opposite to the floor surface is defined as +90°, and a direction from the center of the light-emitting surface toward a light emission side, orthogonal to the light-emitting surface, is defined as a perpendicular 0°, then the angle of maximum intensity in the light distribution of emitted light from the center of the light-emitting surface is at least equal to -90° and less than 0°.

Description

[Technical field]

[0001] The present invention relates to a surface lighting device, a space including a surface lighting device, and a lighting method. [Background technology]

[0002] As teleworking progresses, the lighting environment is becoming more important not only in offices but also at home. Light-emitting diodes (LEDs), which consume little power and have a long lifespan, are widely used as light sources for lighting equipment. In the case of LED lighting, the luminous flux obtained from a single LED is small, so it is common to use multiple LEDs together. With this type of LED lighting, a phenomenon known as "multiple shadows" occurs, where shadows are generated for each light source, causing flickering.

[0003] A one-sided lighting window that serves both as a window and as a light source has been proposed (see, for example, Patent Document 1). When lighting is provided, such as at night, light emitted from a light source is incident on an end of a plate-shaped transparent substrate, and the illumination light guided through the transparent substrate is emitted from only one side. When lighting is not provided, such as during the day, the transparent substrate functions as a transparent window. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 102959 Summary of the Invention [Problem to be solved by the invention]

[0005] In the single-sided lighting disclosed in Patent Document 1, a reflective recess is provided on the surface opposite to the light exit surface to scatter the light. Since the illumination light emitted from the single-sided lighting is viewed directly, the user may feel the flickering of the light, which may cause eye strain or stress.

[0006] An object of the present invention is to provide a surface lighting device in which light flicker is suppressed, and a space and a lighting method using the same. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a surface lighting device that is installed on a side wall of a space having a floor and a side wall perpendicular to the floor, comprising: When the axis passing through the center of the light exit surface of the surface lighting device and perpendicular to the floor surface is defined as the vertical axis, and within a plane that includes the vertical axis and is perpendicular to the light exit surface, the direction on the vertical axis from the center of the light exit surface toward the floor surface is defined as -90°, the direction from the center of the light exit surface toward the opposite side of the floor surface is defined as +90°, and the direction from the center of the light exit surface toward the light exit side and perpendicular to the light exit surface is defined as 0° perpendicular, the angle at which the light distribution of the exiting light from the center of the light exit surface has maximum intensity within the perpendicular plane is greater than or equal to -90° and less than 0°. Effect of the Invention

[0008] The above configuration realizes a surface illumination device in which flickering of light is suppressed. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a space including a surface lighting device according to an embodiment. [Diagram 2] 1 is a diagram illustrating the spatial coordinates of a surface illumination device. [Figure 3A] FIG. 1 is a diagram defining an angle in a vertical direction with respect to a floor surface. [Figure 3B] FIG. 1 is a diagram showing light distribution characteristics in the YZ plane. [Figure 4A] FIG. 1 is a diagram defining an angle in the horizontal direction with respect to a floor surface. [Figure 4B] FIG. 1 is a diagram showing light distribution characteristics in the XY plane. [Diagram 5] FIG. 1 is a diagram illustrating an example of the configuration of a surface illumination device. [Figure 6A] FIG. 13 is a diagram showing another example of the configuration of the surface illumination device. [Figure 6B] FIG. 13 is a diagram showing another example of the configuration of the surface illumination device. [Figure 6C] FIG. 13 is a diagram showing another example of the configuration of the surface display device. [Figure 7] FIG. 2 is a diagram illustrating the significance of providing a low refractive index layer. [Figure 8] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 9] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 10] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 11] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 12] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 13] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 14] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 15] FIG. 13 is a diagram showing yet another example of the configuration of the surface illumination device. [Figure 16] 1A and 1B are diagrams showing a usage mode of a surface illumination device. [Figure 17] 1A and 1B are diagrams showing a usage mode of a surface illumination device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the embodiment, a surface lighting device is provided that does not cause a user to feel light flicker, fatigue, stress, etc. This surface lighting device emits light with directionality in a direction that is difficult for the user to directly view. In a good configuration example, light loss is minimized and light emission efficiency is increased. A specific configuration will be described below with reference to the drawings.

[0011] 1 is a schematic diagram of a space 20 including a surface lighting device 10 of an embodiment. The space 20 includes a floor surface 2, a side wall 3 perpendicular to the floor surface 2, and the surface lighting device 10 installed on the side wall 3. As a coordinate system, a plane parallel to the floor surface 2 is defined as the XY plane, and a height direction perpendicular to the XY plane is defined as the Z direction. The surface lighting device 1 is disposed within the XZ plane, and the light emission direction is defined as the Y direction.

[0012] The surface lighting device 10 includes a light guide plate 11 and has a light guide section 300 that guides light and emits light with a predetermined light distribution. When the surface lighting device 10 is used as window lighting, a transparent light guide plate 11 may be used. For example, the visible light transmittance of the light guide section 300 including the light guide plate 11 is 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more. The visible light transmittance is specified as the average value of the transmittance at each wavelength when measured at a measurement wavelength of 380 nm or more and 780 nm or less using a spectrophotometer. When the surface lighting device 10 is used as wall lighting, the light guide plate 11 does not necessarily have to be transparent as long as it has a light guide function and a light emission function, and a translucent light guide plate may be used.

[0013] The light guide plate 11 is made of glass, plastic, or the like. As the glass material, quartz glass, alkali-free glass, borosilicate glass, or the like can be used. As the plastic material, acrylic resin (e.g., polymethyl methacrylate (PMMA)), polycarbonate (PC) resin, cycloolefin (COP) resin, or the like can be used. As will be described later, the light guide plate 11 is configured to emit light having directionality in a predetermined direction.

[0014] FIG. 2 is a diagram for explaining the spatial coordinates of the surface lighting device 10. The light guide plate 11 has a first main surface 111 from which light is emitted. The first main surface 111 is nearly perpendicular to the floor surface 2. The term "nearly perpendicular" means that an error of about ±5° from the perpendicular may be included. The light emitted from the first main surface 111 has a light distribution that is biased downward from a direction horizontal to the floor surface 2. As long as this light distribution is satisfied, the first main surface 111 may have an error of about ±5° from the perpendicular direction to the floor surface 2.

[0015] In first main surface 111, an axis that passes through center C of first main surface 111 and is perpendicular to floor surface 2 is defined as the vertical axis, or V axis. A direction that includes the V axis and is parallel to floor surface 2 within the YZ plane that is perpendicular to floor surface 2 is defined as 0° vertical. An angle upward from 0° vertical within the YZ plane is defined as a positive angle, and a downward angle is defined as a negative angle.

[0016] Considering the light distribution distribution of the emitted light from the center C on the XZ plane perpendicular to the floor surface 2, light can generally be emitted in the range of -90° to +90°. In the above-mentioned Patent Document 1, the light is also scattered to emit light in a wide angle range. In contrast, in the surface lighting device 10, the angle at which the intensity is maximum in the light distribution distribution of the emitted light from the center of the light emission surface is set to a range of -90° or more (e.g., more than -90°) and less than 0°. For example, the upper limit is -0.1°, -1°, -5°, -10°, -10°, -20°, -30°, -40°, -50°, -60°, -70°, -80°, -85°, -88°, -89°, and the lower limit is -90°, -89°, -88°, -85°, -80°, -70°, -60°, -50°, -40°, -30°, -20°, -10°, -5°, -1°, and the lower limit value does not exceed the upper limit value. The light distribution of the emitted light can be measured using a viewing angle measuring instrument (for example, a luminance viewing angle measuring instrument EZContrast XL88 manufactured by ELDIM).

[0017] Regarding the horizontal direction, the axis that passes through center C on first main surface 111 and is horizontal to floor surface 2 is defined as the horizontal axis, or H axis. Within the XY plane that includes the H axis and is horizontal to floor surface 2, the angle that passes through center C of first main surface 111 toward the Y direction is defined as horizontal 0°. Furthermore, when the XY plane that passes through center C is viewed from the opposite side to the floor surface (or from above the floor surface), a clockwise angle from horizontal 0° is defined as a positive angle, and a counterclockwise angle is defined as a negative angle. In the XY plane passing through the center C, the light distribution of the light emitted from the center C of the first main surface 111 is within the range of -90° to +90°, for example, within the range of more than -90° and less than +90°, for example, the lower limit is -90°, -89°, -88°, -85°, -80°, -70°, -60°, -50°, -40°, -30°, -20°, -10°, and the upper limit is +90°, +89°, +88°, +85°, +80°, +70°, +60°, +50°, +40°, +30°, +20°, +10°. Preferably, the surface lighting device 10 has a uniform light distribution in the horizontal direction.

[0018] Fig. 3A is a diagram defining the vertical angle of the surface lighting device 10, and Fig. 3B is an image diagram of the light distribution in the YZ plane. The coordinate system of Fig. 3A and Fig. 3B is the same as Fig. 1 and Fig. 2. In Fig. 3A, on the YZ plane perpendicular to the floor surface 2, the angle range that can be taken in the vertical direction is from -90° to +90°. As shown in Fig. 3B, the first main surface 111, which is the light exit surface of the surface lighting device 10, is configured so that the angle at which the intensity of the emitted light is maximum is in the range of -90° or more and less than 0°.

[0019] By setting the angle at which the intensity of the light emitted from the center of the light emission surface is at maximum (i.e., the angle formed by the arrow in FIG. 3B) in the range of -90° or more and less than 0°, a given space including the floor surface 2 is illuminated with sufficient illuminance while preventing the emitted light from directly entering the user's eyes. This prevents the user from feeling flicker or fatigue and creates a comfortable lighting space.

[0020] Fig. 4A is a diagram defining the horizontal angle of the surface lighting device 10, and Fig. 4B is an image diagram of light distribution in the XY plane. The coordinate system of Fig. 4A and Fig. 4B is the same as Fig. 1 and Fig. 2. In Fig. 4A, in the XY plane horizontal to the floor surface 2, the light distribution of the emitted light is in the range of -90° to +90°. The first main surface 111, which is the light emission surface of the surface lighting device 10, is configured so that the emitted light is distributed in the range of -90° to +90°, as shown in Fig. 4B.

[0021] By setting the horizontal light distribution in the range of -90° to +90°, the space including the floor surface 2 can be illuminated almost uniformly.

[0022] <Example of surface lighting device configuration> The following describes a specific configuration example of the surface lighting device 10. In the surface lighting device 10, light is emitted with a specific light distribution from the first main surface 111. The light guide plate 11 is configured to achieve directional light emission.

[0023] 5 shows a surface illumination device 10A as a first configuration example. The surface illumination device 10A has a light source 31 and a light guide section 300 including a light guide plate 11A. The light guide plate 11A has a light incident surface 113 facing the light source 31 and receiving light from the light source, a first main surface 111 from which the light incident on the light guide plate 11A exits, and a second main surface 112 opposite to the first main surface.

[0024] In the first configuration example, the light source 31 receives light from the light incident surface 113 of the light guide plate 11A. The light incident surface 113 is an end surface facing the light source 31. The "end surface" is a surface in the thickness direction of the light guide plate 11A that is perpendicular to the first main surface 111 or the second main surface 112. As long as light can be received from the light incident surface 113 of the light guide plate 11A, there is no limitation on the configuration or type of the light source 31. As an example, one or more LEDs are used as the light source 31. An LED array in which multiple LEDs are arranged in a row may be used as a linear light source. Instead of an LED, an organic electroluminescence (EL) emitter or inorganic EL emitter capable of surface emission, or a linear light source such as a fluorescent lamp or a cold cathode fluorescent tube may be used.

[0025] One or more light sources 31 may be mounted on a substrate and connected to a heat sink with a thermally conductive adhesive. In the example of Fig. 5, the light source 31 is disposed on the lower end side (-Z side) of the light guide plate 11A, but it may also be disposed on the upper end side (+Z side) or to the side.

[0026] When the surface lighting device 10A is used as a window light, the light guide plate 11A is made of a material transparent to visible light. The light incident on the light guide plate 11A from the light incident surface 113 is guided inside the light guide plate 11A while being totally reflected by the first main surface 111 and the second main surface 112, and the light that does not satisfy the total reflection condition among the light incident on the first main surface 111 is emitted from the first main surface 111 with the above-mentioned light distribution. A specific configuration for emitting the light with the light distribution of FIG. 3B from the first main surface will be described later.

[0027] <Example of light guide section configuration> 6A to 6C show a configuration example of the light guide section 300 used in the surface illumination device 10. In the configuration example of FIG. 6A to FIG. 6C, the light guide section 300 has a low refractive index layer having a lower refractive index than the light guide plate 11 on at least one of the first main surface 111 and the second main surface 112 of the light guide plate 11. For example, the visible light transmittance of the light guide plate 11 and the light guide section 300 including the low refractive index layer is 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more. The visible light transmittance is specified as the average value of the transmittance at each wavelength when measured at a measurement wavelength of 380 nm or more and 780 nm or less using a spectrophotometer.

[0028] The low refractive index layer is a layer having a refractive index lower than that of the light guide plate 11. When the light guide plate 11 is mainly composed of PMMA, the refractive index n1 of the light guide plate 11 is about 1.49. In comparison, the refractive index n2 of the low refractive index layer is preferably 1.30 or less, more preferably 1.20 or less. The low refractive index layer is not particularly limited, but for example, a low refractive index layer having voids disclosed in International Publication No. 2019 / 146628 can be used. The contents of this document are incorporated by reference.

[0029] 6A has a light source 31 and a light guide section 300 including a light guide plate 11B. The light guide plate 11B has a light incident surface 113 facing the light source 31, a first main surface 111, and a second main surface 112. The light guide plate 11B also has a low refractive index layer 26 provided on the first main surface 111. The low refractive index layer 26 may be covered with a cover layer 28a.

[0030] Light incident on light guide plate 11B from light incident surface 113 propagates inside light guide plate 11B while being totally reflected between first main surface 111, on which low refractive index layer 26 is provided, and second main surface 112. Of the light incident on the interface between first main surface 111 and low refractive index layer 26, light that does not satisfy the total reflection condition is emitted from first main surface 111 with a predetermined light distribution, that is, such that the angle at which the light emitted from the center of first main surface 111 has maximum intensity in the light distribution distribution in the YZ plane is in the range of -90° or more and less than 0°. In the horizontal direction (in the XY plane), the emitted light may have a distribution in the range of -90° to +90°.

[0031] By providing the low refractive index layer 26 on the first main surface 111, it is possible to suppress light loss caused by dirt or scratches on the light exit surface.

[0032] 6B includes a light source 31 and a light guide section 300 including a light guide plate 11C. The light guide plate 11C includes a light incident surface 113 facing the light source 31, a first main surface 111, and a second main surface 112. The light guide plate 11C further includes a low refractive index layer 27 on the second main surface 112. The low refractive index layer 27 may be covered with a cover layer 28b.

[0033] Light incident on light guide plate 11C from light incident surface 113 propagates inside light guide plate 11C while being totally reflected between first main surface 111 and second main surface 112 on which low refractive index layer 27 is provided. Of the light incident on first main surface 111, light that does not satisfy the total reflection condition is emitted from first main surface 111 so that the angle at which the light emitted from the center of first main surface 111 has maximum intensity in the light distribution in the YZ plane is in the range of -90° or more and less than 0°. In the horizontal direction (XY plane), the emitted light may have a distribution in the range of -90° to +90°.

[0034] By providing the low refractive index layer 27 on the second major surface 112, it is possible to suppress light loss caused by stains or scratches on the second major surface 112, and to efficiently direct light in the direction of the first major surface 111.

[0035] 6C includes a light source 31 and a light guide section 300 including a light guide plate 11D. The light guide plate 11D includes a light incident surface 113 facing the light source, a first main surface 111, and a second main surface 112. The light guide plate 11D also includes a low refractive index layer 26 on the first main surface 111, and a low refractive index layer 27 on the second main surface 112. The low refractive index layers 26 and 27 may be covered with cover layers 28a and 28b, respectively.

[0036] Light incident on light guide plate 11D from light incident surface 113 propagates inside light guide plate 11D while being totally reflected between first main surface 111 and second main surface 112. Of the light incident on the interface between first main surface 111 and low refractive index layer 26, light that does not satisfy the total reflection condition is emitted at an angle ranging from -90° to less than 0° where the light intensity becomes maximum in the light distribution distribution in the YZ plane of the light emitted from the center of first main surface 111. In the horizontal direction (in the XY plane), the emitted light may have a distribution ranging from -90° to +90°.

[0037] By providing the low refractive index layers 26 and 27 on the first main surface 111 and the second main surface 112, respectively, it is possible to suppress light loss caused by stains or scratches on the main surfaces of the light guide plate 11D.

[0038] 7 is a diagram for explaining the significance of providing the low refractive index layer 26 or 27. Consider a case where dirt C1, C2 such as sebum or sweat is attached to the first main surface 111 or the second main surface 112. Of the light propagating inside the light guide plate 11 while being totally reflected between the first main surface 111 and the second main surface 112, the light that is incident on the position where the dirt C1 or C2 is attached is scattered by the dirt C1 or C2, and optical loss occurs before the light is emitted from the first main surface 111.

[0039] By providing a low refractive index layer 26 or 27 on at least one of the first main surface 111 and the second main surface 112, it is possible to prevent light propagating inside the light guide plate 11 from being lost due to scattering, etc., and to maintain high emission efficiency from the first main surface 111.

[0040] Figures 8 to 10 show other configuration examples of the light guide plate. In the configuration examples of Figures 8 to 10, light is output from first main surface 111 of light guide plate 11 with the above-mentioned light distribution by utilizing an optical cavity.

[0041] 8 is a schematic diagram of a surface illumination device 10E. The surface illumination device 10E has a light source 31 and a light guide section 300 including a light guide plate 11E. The light guide plate 11E has one or more optical cavities 151 therein, and a light extraction section 15 is provided on a first main surface 111.

[0042] For example, the visible light transmittance of light guide plate 11E and light guide section 300 including light extraction section 15 is 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more. The visible light transmittance is specified as the average value of the transmittance at each wavelength when measured using a spectrophotometer at a measurement wavelength of 380 nm or more and 780 nm or less.

[0043] The optical cavity 151 is a gap filled with a material having a lower refractive index than the light guide plate 11E. If the gap is filled with air, it becomes an air cavity. In addition to air, the optical cavity 151 may be filled with a gas, liquid, or solid material having a lower refractive index than the light guide plate 11E.

[0044] The optical cavity 151 is designed so that light incident on the interface of the optical cavity 151 from the light guide plate 11E is totally reflected in the direction of the first main surface 111, and the angle at which the intensity becomes maximum in the light distribution of the light emitted from the center of the first main surface 111 is in the range of -90° or more and less than 0° in the YZ plane.

[0045] The light guide plate 11E has a plurality of optical cavities 151 arranged regularly or randomly along the plane of the first main surface 111. The size of the optical cavities 151 can be appropriately selected within a range that allows installation inside the light guide plate 11E. The light guide plate including the optical cavities therein is not particularly limited, but for example, the light guide plates disclosed in International Publication No. 2011 / 124765, International Publication No. 2011 / 127187, International Publication No. 2019 / 087118, and International Publication No. 2019 / 182091 can be used. The contents of these documents are incorporated herein by reference.

[0046] The light guide plate 11E containing the optical cavity 151 therein can be produced, for example, by bonding a light guide layer having a desired cavity pattern formed on its surface with a flat light guide layer without a cavity pattern. The light guide layers are bonded together by lamination such as adhesive-free microwave surface treatment, or by pressing with an adhesive (including a pressure-sensitive adhesive). In order to suppress interface reflection, it is desirable for the refractive indexes of the light guide layers to be bonded together to be approximately equal. When an adhesive is used, it is preferable to use an adhesive with a refractive index approximately equal to that of the light guide layer.

[0047] The cavity pattern is formed in the light guide layer by laser patterning, direct laser imaging, laser drilling, laser irradiation through a mask or without a mask, electron beam irradiation, etc. Alternatively, individual properties (such as changes in refractive index value) may be imparted to the portion that will become the optical cavity 151 by printing, inkjet printing, screen printing, etc. Micro / nano dispensing, dosing, direct writing, discrete laser sintering, micro-electric discharge machining (EDM), micro-machining, micro-molding, imprinting, embossing, and the like may also be used.

[0048] Light guide plate 11E allows light incident on light incident surface 113 to propagate through the inside of light guide plate 11E by total reflection and to be emitted from first main surface 111 with the above-mentioned light distribution.

[0049] 9 is a schematic diagram of a surface lighting device 10F. The surface lighting device 10F has a light source 31 and a light guide section 300 including a light guide plate 11F. The light guide plate 11F has a light extraction layer 16 functioning as a light extraction section on a first main surface 111. The light extraction layer 16 has one or more optical cavities 161 formed therein.

[0050] The light extraction layer 16 having the optical cavities 161 can be formed by bonding a flat light guide layer without a cavity pattern to a light guide layer having a cavity pattern formed on its surface, similar to the light guide plate 11E in Fig. 8. Alternatively, the light guide layer having the cavity pattern formed thereon may be directly bonded to the first main surface 111.

[0051] From the viewpoint of suppressing undesirable refraction and reflection, it is desirable that the refractive index of the light extraction layer 16 is the same as or close to that of the light guide plate 11E. For example, when the light guide plate 11F is made of polymethyl methacrylate (PMMA), the light extraction layer 16 is made of a material having the same or a close refractive index as PMMA.

[0052] Light incident on the light extraction layer 16 from the light guide plate 11F is totally reflected at the interface of the light cavity 161, and is emitted from the outermost surface 162 of the light extraction layer 16. The interface of the light cavity 161 is designed so that the light incident from the light guide plate 11F is totally reflected in the direction of the outermost surface 162 of the light extraction layer 16, and the angle at which the light intensity becomes maximum in the light distribution of the emitted light from the center of the first main surface 111 is in the range of -90° or more and less than 0° in the YZ plane.

[0053] Light incident on the light guide plate 11F through the light incident surface 113 can be propagated inside the light guide plate 11F by total reflection and emitted from the light extraction layer 16 with the above-mentioned light distribution.

[0054] 10 is a schematic diagram of a surface lighting device 10G. The surface lighting device 10G has a light source 31 and a light guide section 300 including a light guide plate 11G. The light guide plate 11G has a light extraction layer 17 functioning as a light extraction section on the second main surface 112. The light extraction layer 17 has one or more optical cavities 171 formed therein.

[0055] The light extraction layer 17 having the optical cavities 171 can be formed by bonding a flat light guide layer without a cavity pattern to a light guide layer having a cavity pattern formed on its surface, similar to the light guide plate 11E in Fig. 8 and the light extraction layer 16 in Fig. 9. Alternatively, the light guide layer having the cavity pattern formed thereon may be directly bonded to the second main surface 112.

[0056] From the viewpoint of suppressing undesirable refraction and reflection, it is desirable that the refractive index of the light extraction layer 17 is the same as or close to that of the light guide plate 11G. For example, when the light guide plate 11G is made of polymethyl methacrylate (PMMA), the light extraction layer 17 is made of a material having the same or a close refractive index as PMMA.

[0057] The light incident on the light extraction layer 17 from the light guide plate 11G is totally reflected at the interface of the optical cavity 171 and guided in the direction of the first main surface 111. As described above, the angle at which the intensity becomes maximum in the light distribution of the light emitted from the center of the first main surface 111 is equal to or greater than -90° and less than 0° in the YZ plane.

[0058] The light guide plate 11G allows the light incident from the light incident surface 113 to propagate inside the light guide plate 11G by total reflection, while guiding the light from the light extraction layer 17 in the direction of the first main surface 111, and then emits the light from the first main surface 111 with the predetermined light distribution described above.

[0059] With any of the configurations in Figs. 8 to 10, it is possible to illuminate the space with sufficient illuminance, prevent emitted light rays from directly entering the user's eyes, and suppress flickering.

[0060] 11 is a schematic diagram of a surface illumination device 10H. The surface illumination device 10H has a light guide section 300 including a light guide plate 11H. The light guide plate 11H has a prism section 251 as a light extraction section provided on a first main surface 111. As the prism section 251, for example, a prism sheet may be bonded to the first main surface 111. In this case, it is desirable that the refractive indexes of the prism sheet and the light guide plate 11H are the same or close to each other.

[0061] The size of prism portion 251, the number of inclined surfaces, etc. are appropriately selected within a range in which prism portion 251 can be arranged on first main surface 111. Light incident on prism portion 251 from light guide plate 11H is refracted by prism portion 251 and emitted from light guide plate 11H. As described above, the angle and pitch of the inclined surfaces of prism portion 251 are designed so that the angle at which the intensity becomes maximum in the light distribution of light emitted from the center of first main surface 111 is greater than or equal to -90° and less than 0° in the YZ plane.

[0062] 12 is a schematic diagram of a surface illumination device 10I. The surface illumination device 10I has a light guide section 300 including a light guide plate 11I. The light guide plate 11I is provided with a prism section 252 as a light extraction section on the second main surface 112. As the prism section 252, for example, a prism sheet may be bonded to the second main surface 112. In this case, it is desirable that the refractive indexes of the prism sheet and the light guide plate 11I are the same or close to each other.

[0063] The size of prism portion 252, the number of inclined surfaces, etc. are appropriately selected within a range in which prism portion 252 can be arranged on second main surface 112. Light incident on prism portion 252 from light guide plate 11I is refracted by prism portion 252 in the direction of first main surface 111, and is emitted from first main surface 111. As described above, the angle and pitch of the inclined surfaces of prism portion 252 are designed so that the angle at which the intensity becomes maximum in the light distribution of light emitted from the center of first main surface 111 is greater than or equal to -90° and less than 0° in the YZ plane.

[0064] The configuration of FIG. 11 or FIG. 12 also makes it possible to prevent emitted light from directly entering the user's eyes, creating a lighting environment with less flicker and less oppressive feeling.

[0065] 13 is a schematic diagram of a surface lighting device 10J. The surface lighting device 10J has a light guide section 300 including a light guide plate 11J. The light guide plate 11J has an uneven portion 253 as a light extraction section on the first main surface 111. The uneven portion 253 has a plurality of convex portions or concave portions with a width (or diameter) and height of about 1 to 5 μm. The uneven portion 253 is designed so that the angle at which the intensity becomes maximum in the light distribution of the light emitted from the center of the first main surface 111 is not less than −90° and less than 0° in the YZ plane. As the uneven portion 253, an optical film in which concave portions and convex portions that satisfy the above conditions are formed may be used.

[0066] FIG. 14 is a schematic diagram of a surface lighting device 10K. The surface lighting device 10K has a light guide section 300 including a light guide plate 11K. The light guide plate 11K has an uneven portion 254 as a light extraction section on the second main surface 112. The uneven portion 254 has a plurality of convex portions or concave portions with a width (or diameter) and height of about 1 to 5 μm. The uneven portion 254 deflects the light incident on the uneven portion 254 from the light guide plate 11K toward the first main surface 111, and emits the light from the first main surface 111. The uneven portion 254 is designed so that the angle at which the intensity becomes maximum in the light distribution of the emitted light from the center of the first main surface 111 is -90° or more and less than 0° in the YZ plane. As the uneven portion 254, an optical film in which concave portions and convex portions that satisfy the above conditions are formed may be used.

[0067] The configuration of FIG. 13 or FIG. 14 also makes it possible to prevent emitted light from directly entering the user's eyes, creating a lighting environment with less flicker and less oppressive feeling.

[0068] 15 shows a surface lighting device 10L as a second configuration example of the surface lighting device 10. In the second configuration example, a surface light source 30 is used. The surface lighting device 10L includes a surface light source 30 and a viewing angle adjusting film 22. The surface light source 30 is disposed perpendicular to the floor surface 2 in the XZ plane, and emits light from the entire Z plane. An EL lamp or a backlight for liquid crystal display may be used as the surface light source 30.

[0069] The surface illumination device 10L may be used as a part of the side wall 3, or may be disposed on the surface of the side wall 3 or in the vicinity thereof.

[0070] The viewing angle adjusting film 22 has a light exit surface 221 on the main surface opposite to the surface light source 30. The viewing angle adjusting film 22 has a function of adjusting the angle at which the intensity of the light emitted from the center of the surface light source 30 is maximum in the light distribution within a range of -90° or more and less than 0° in the YZ plane. The viewing angle adjusting film 22 transmits only light incident from a specific direction or at an incident angle within a specific range of light incident from the surface light source 30, and does not transmit other light.

[0071] A louver film in which transparent resin with high light transmittance and resin with high reflectance are alternately arranged in the Z direction, or a liquid crystal film can be used as the viewing angle adjustment film 22. In the case of a liquid crystal film, a voltage needs to be applied to control the orientation direction of the liquid crystal, so a louver film is preferable from the viewpoint of energy saving.

[0072] The view angle adjusting film 22 may be configured not to limit the view angle in the horizontal direction, but to emit light at angles between −90° and +90°. <How the surface lighting device is used> 16 and 17 are diagrams showing a usage mode of the surface lighting device 10. Here, a configuration example without using a surface light source 30 is shown. In FIG. 16, the light incident surface 113 of the light guide plate 11 is arranged parallel to the floor surface (XY plane), and the light source 31 is arranged to face the light incident surface 113 of the light guide plate 11. As an example, a plurality of LEDs are arranged in the X direction. The light output from the light source 31 enters the light incident surface 113 at the lower end of the light guide plate 11, propagates through the light guide plate in the Z direction, and is output from the first main surface 111 with the light distribution shown in FIG. 3B.

[0073] 17, the light incident surface of the light guide plate 11 is disposed perpendicular to the floor surface (XY plane), and the light source 31 is disposed along the light incident surface 113. As an example, a plurality of LEDs are arranged in the Z direction. The side end surface of the light guide plate 11 facing the light source 31 becomes the light incident surface 113.

[0074] Light output from light source 31 enters light incident surface 113 at the side end of light guide plate 11, propagates through light guide plate 11 in the X direction, and is output from first main surface 111 with the light distribution shown in FIG. 3B.

[0075] When the light guide plate 11 is made of a material transparent to visible light, the surface lighting device 10 may be fitted into a window frame and used as a window during the day. When it gets dark, such as at night, the surface lighting device 10 is lit by turning on the light source 31. Note that a light source switch and wiring are omitted.

[0076] The surface lighting device 10 may be used as a wall light in homes, office buildings, schools, art museums, etc. In this case, the light guide plate 11 may be transparent or semi-transparent to visible light. If the light guide plate 11 is transparent, it may be used as interior decoration during the day by placing a poster or a picture between the wall surface and the light guide plate 11. Also, the surface lighting device 10L in FIG. 15 may be used as a wall light.

[0077] In either usage mode, the illumination light is prevented from entering the user's eyes directly, creating an illuminated space with less flicker and a feeling of oppression.

[0078] The illumination method using the surface illumination device is as follows: A surface lighting device is installed on the side wall perpendicular to the floor surface. When the axis passing through the center of the light exit surface of the surface lighting device and perpendicular to the floor surface is defined as the vertical axis, and within a plane including the vertical axis and perpendicular to the light exit surface, the direction on the vertical axis from the center of the light exit surface toward the floor surface is defined as -90°, the direction from the center of the light exit surface toward the opposite side of the floor surface is defined as +90°, and the direction from the center of the light exit surface toward the light exit side and perpendicular to the light exit surface is defined as 0° vertical, light is irradiated so that the angle at which the light distribution of the exiting light from the center of the light exit surface has maximum intensity within the perpendicular plane is greater than or equal to -90° and less than 0°.

[0079] This lighting method can be implemented by any of the surface lighting devices shown in Figures 5 to 17. This lighting method creates an illuminated space with less flicker and less oppressive feeling.

[0080] Although the present invention has been described above based on specific configuration examples, the present invention is not limited to the above configuration examples. Two or more of the configurations of the light guide plate described with reference to Figures 5 to 14 may be combined. For example, the low refractive index layer 26 or 27 may be combined with the viewing angle adjusting film 22 of Figure 15, or the low refractive index layer 26 or 27 may be combined with the configuration of the optical cavity.

[0081] The shape of the light guide plate 11 may be any planar shape that can be used in a surface lighting device. For example, it may be a triangle, a rhombus, a circle, an ellipse, or the like. In the case of a triangle, the emission direction of a plurality of light sources arranged on one side may be alternately arranged toward the directions of the other two sides. In the case of a rhombus, the light sources may be arranged so as to face one side or two adjacent sides. Also, in the case where the surface light source 30 is used, the planar shape of the surface lighting device 10L is not limited to a rectangle.

[0082] In either case, by emitting light with a predetermined light distribution from the light exit surface, a comfortable illuminated space with reduced oppressive sensations and light flickering is realized.

[0083] This application claims priority based on Japanese Patent Application No. 2020-127349, filed on July 28, 2020, and includes the entire contents of this Japanese patent application. [Explanation of symbols]

[0084] 2. Floor surface 3 side wall 10, 10A~10L surface lighting device 11, 11A~11L light guide plate 111 First main surface 112 Second main surface 113 Light entrance surface 15 Light extraction section 151 Optical Cavity 16, 17 Light extraction layer 161, 171 Optical cavity (air gap) 162 Outermost surface 22 Viewing angle adjustment film 221 Light exit surface 26, 27 Low refractive index layer 28a, 28b Cover layer 30 area light source 31 Light source 251, 252 Prism part 253, 254 Uneven part 300 Light guide section

Claims

1. A surface lighting device installed on a side wall in a space having a floor surface and a side wall perpendicular to the floor surface, comprising: A light source; a light guide portion including a light guide plate and configured to guide light from the light source; Equipped with when an axis passing through the center of the light exit surface of the surface lighting device and perpendicular to the floor surface is defined as a vertical axis, and within a plane including the vertical axis and perpendicular to the light exit surface, a direction on the vertical axis from the center of the light exit surface toward the floor surface is defined as -90°, a direction from the center of the light exit surface toward the opposite side from the floor surface is defined as +90°, and a direction from the center of the light exit surface toward the light exit side and perpendicular to the light exit surface is defined as 0° perpendicular, an angle at which the intensity is maximum in the light distribution of the exiting light from the center of the light exit surface within the perpendicular plane is equal to or greater than -90° and less than 0°, the light guide plate has a light incident surface on which light from the light source is incident, a first main surface serving as the light exit surface, and a second main surface facing the first main surface; The light guiding portion is transparent to visible light, the back of the surface lighting device on the second principal surface side can be seen through the space on the first principal surface side; Surface lighting device.

2. 2. The surface lighting device of claim 1, wherein an axis passing through the center of the light exit surface and parallel to the floor surface is defined as a horizontal axis, and a direction from the center of the light exit surface toward the light exit side within a plane that includes the horizontal axis and is parallel to the floor surface and is perpendicular to the light exit surface is defined as 0° horizontal, and when the parallel surface is viewed from the opposite side to the floor surface, a clockwise angle from the 0° direction is defined as a positive angle and a counterclockwise angle is defined as a negative angle, so that within the parallel surface, the light distribution of the light exiting from the center is within the range of -90° to +90°.

3. A surface lighting device as described in claim 1 or 2, wherein the surface lighting device is used as a window, or the light exit surface is used as a wall surface.

4. The surface illumination device according to claim 1 , wherein the light guide portion has a low refractive index layer, the low refractive index layer having a refractive index lower than that of the light guide plate, on at least one of the first main surface and the second main surface.

5. The surface illumination device according to claim 4 , wherein the light guide portion has the low refractive index layer on both the first main surface and the second main surface.

6. 6. The surface illumination device according to claim 1, wherein the light guide portion has a light extraction portion that emits the light propagating through the light guide plate from the first main surface with the light distribution.

7. 7. The surface illumination device of claim 6, wherein the light extraction portion is a gap provided inside the light guide plate, on the first main surface, or on the second main surface, and the gap totally reflects the light propagating through the light guide plate and emits the light with the light distribution from the first main surface.

8. The surface illumination device according to claim 6 , wherein the light extraction portion is a prism portion or an uneven portion that is disposed on the first main surface and causes the light propagating through the light guide plate to exit with the light distribution.

9. The surface illumination device according to claim 6 , wherein the light extraction portion is a prism portion or an uneven portion that is disposed on the second main surface and directs the light propagating through the light guide plate toward the first main surface.

10. 10. The surface illumination device according to claim 1, wherein the light guide plate has a light entrance surface that is parallel to the floor surface.

11. A surface lighting device as described in Claim 10, wherein the light incident surface is provided on the floor surface side of the light guide plate.

12. 10. The surface illumination device according to claim 1, wherein the light guide plate has a light entrance surface that is perpendicular to the floor surface.

13. The floor surface and A side wall installed perpendicular to the floor surface; The surface lighting device according to any one of claims 1 to 12, which is installed on the side wall; A space equipped with:

14. The floor surface and A side wall installed perpendicular to the floor surface; A method for illuminating a space including the surface illumination device according to any one of claims 1 to 12, the surface illumination device being installed on the side wall, the method comprising: light is illuminated such that, when an axis passing through the center of the light exit surface of the surface lighting device and perpendicular to the floor surface is defined as a vertical axis, and a direction on the vertical axis from the center of the light exit surface toward the floor surface within a plane including the vertical axis and perpendicular to the light exit surface is defined as -90°, a direction from the center of the light exit surface toward the opposite side to the floor surface is defined as +90°, and a direction from the center of the light exit surface toward the light exit side and perpendicular to the light exit surface is defined as 0° perpendicular, within the perpendicular plane, an angle at which the light intensity becomes maximum in the light distribution distribution of the exiting light from the center of the light exit surface is equal to or greater than -90° and less than 0°; lighting method.

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