Tabletop lighting device

Abstract

Provided is a tabletop lighting device in which a sense of oppressiveness and flickering of light are reduced. A tabletop lighting device having a light source and a light guide unit that includes a light guide plate, the light guide unit guiding light that has been emitted from the light source, wherein: the light guide plate has a light incidence surface on which light from the light source is incident, a first main surface from which light that was incident on the light incidence surface is emitted, and a second main surface opposite from the first main surface; the first main surface is positioned so as to be roughly perpendicular to an installation surface of the tabletop lighting device; and the angle at which maximum intensity is achieved in a light distribution of the light emitted from the first main surface is equal to or greater than −90° and less than 0°, where an axis that passes through the center of the first main surface and that is perpendicular to the installation surface is a perpendicular axis, and where, in a plane that includes the perpendicular axis and that is perpendicular to the installation surface, a direction parallel to the installation surface is perpendicular 0°, an angle having a higher orientation than the parallel direction is a positive angle, and an angle having a lower orientation than the parallel direction is a negative angle.

Description

[Technical field]

[0001] The present invention relates to a desk lighting device. [Background technology]

[0002] Lighting devices using light-emitting diodes (LEDs) are becoming more and more common. 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, which causes flickering.

[0003] Directional lighting devices that convert light from an LED into directional planar or linear emission have been proposed (see, for example, Patent Document 1). In these lighting devices, an LED light source is arranged with one side or two opposing sides of a light guide made of a transparent material as the incident side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-110783 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the desk light disclosed in Patent Document 1, the lighting unit is located above the desk, and the light emission surface faces downward. The presence of the lighting device may cause the user to feel oppressed. In addition, since the illumination light is directly visible, the user may feel flickering, which may reduce concentration.

[0006] An object of the present invention is to provide a desk lighting device that reduces the feeling of oppression and light flickering. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a tabletop lighting device having a light source and a light guide portion including a light guide plate for guiding light emitted from the light source, the light guide plate has a light incident surface through which light from the light source is incident, a first main surface through which the light incident from the light incident surface is emitted, and a second main surface opposite to the first main surface; The first main surface is disposed substantially perpendicular to a surface on which the desk lighting device is installed, When an axis passing through the center of the first main surface and perpendicular to the installation surface is defined as a vertical axis, and a direction parallel to the installation surface within a plane including the vertical axis and perpendicular to the installation surface is defined as vertical 0°, an angle upward from the parallel direction is defined as a positive angle, and an angle downward from the parallel direction is defined as a negative angle, an angle at which the intensity is maximum in the light distribution of the light emitted from the first main surface is equal to or greater than -90° and less than 0°. the law of nature, The light guiding portion is transparent to visible light, The back of the light guide is visible . Effect of the Invention

[0008] The above configuration realizes lighting that does not cause the user to feel oppressive or experience flickering light. [Brief description of the drawings]

[0009] [Figure 1] 1 is an external view of a tabletop lighting device according to an embodiment. [Diagram 2] FIG. 2 is a diagram defining an angle in the vertical direction with respect to the installation surface. [Diagram 3] FIG. 1 is a diagram showing light distribution characteristics in the YZ plane. [Figure 4] FIG. 2 is a diagram defining an angle in the horizontal direction with respect to the installation surface. [Diagram 5] FIG. 1 is a diagram showing light distribution characteristics in the XY plane. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a light source unit. [Figure 7A] 1A and 1B are diagrams illustrating an example of the configuration of a light guide plate. [Figure 7B] 13A and 13B are diagrams illustrating another configuration example of the light guide plate. [Figure 7C] 13A and 13B are diagrams illustrating another configuration example of the light guide plate. [Figure 8] FIG. 2 is a diagram illustrating the significance of providing a low refractive index layer. [Figure 9] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 10] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 11] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 12] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 13] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 14] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 15] FIG. 13 is a diagram showing yet another configuration example of the light guide plate. [Figure 16] FIG. 2 is a diagram showing an installation state of the desk lighting device. [Figure 17] FIG. 2 is a diagram showing an installation state of the desk lighting device. [Figure 18] 1A and 1B are schematic diagrams illustrating the effects of a desk lighting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the embodiment, in order to realize table lighting that does not cause the user to feel a sense of oppression or flickering of light, a light guide section that includes a light guide plate and is transparent to visible light is used. The first main surface of the light guide plate, which is the light exit surface, is arranged perpendicular to the installation surface of the table lighting device. When using the table lighting device, the user can see through to the back of the light guide section, reducing the sense of claustrophobia and oppression. By providing a predetermined orientation to the distribution of light exiting from the light exit surface, the irradiated light is prevented from being directly viewed by the user, reducing flickering.

[0011] FIG. 1 is an external view of a table lighting device 10 according to an embodiment. The table lighting device 10 is placed on a desk, a table, etc. (hereinafter collectively referred to as "desk 2"). The surface on which the table lighting device 10 is placed is referred to as the "installation surface 2p." A surface parallel to the installation surface 2p is referred to as the XY plane, and a direction perpendicular to the XY plane is referred to as the Z direction. The height direction of the table lighting device 1 is referred to as the Z direction, and the width direction is referred to as the X direction. The light emission direction is referred to as the Y direction.

[0012] The desk lighting device 10 includes a light guide plate 11 and a light guide section 300 that guides light from a light source. Although the light source is omitted in Fig. 1, the light source may be accommodated inside a groove or slot formed in the installation surface 2p, or may be located on the installation surface 2p together with the light guide plate 11. An example of the configuration of the light source will be described later.

[0013] The light guide plate 11 is a solid transparent to visible light, and is made of glass, plastic, or the like. Examples of glass materials that can be used include quartz glass, alkali-free glass, and borosilicate glass. Examples of plastic materials that can be used include acrylic resins (e.g., polymethyl methacrylate (PMMA)), polycarbonate (PC) resins, and cycloolefin (COP) resins. The visible light transmittance of 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 using a spectrophotometer at a measurement wavelength of 380 nm or more and 780 nm or less.

[0014] The light guide plate 11 has a first main surface 111 from which light is emitted. The first main surface 111 is approximately perpendicular to the installation surface 2p. The term "approximately perpendicular" means that it may include an error of about ±5° from the perpendicular. The light emitted from the first main surface 111 has a light distribution that is biased downward from a direction horizontal to the installation surface 2p. As long as this light distribution is satisfied, the first main surface 111 may include an error of about ±5° from the perpendicular.

[0015] In first main surface 111, an axis that passes through center C of first main surface 111 and is perpendicular to installation surface 2p is defined as the vertical axis, or V axis. A direction that includes the V axis and is parallel to installation surface 2p within the YZ plane perpendicular to installation surface 2p is defined as vertical 0°. An angle upward from vertical 0° 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 of the emitted light from the center C on the XZ plane orthogonal to the installation surface 2p, light can generally be emitted in the range of -90° to +90°. In contrast, in the table lighting device 10, the angle at which the intensity is maximum in the light distribution of the emitted light from the center of the first main surface 111 is set in the 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] In first main surface 111, an axis that passes through center C and is horizontal to installation surface 2p is defined as the horizontal axis, or H axis. The angle from 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 installation surface (or from above the installation 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, the horizontal distribution of the light emitted from 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°. The table lighting device 10 may have a substantially uniform light distribution in the horizontal direction.

[0018] Fig. 2 defines the vertical angle of the table lighting device 10, and Fig. 3 shows the light distribution characteristics in the YZ plane. The coordinate system in Fig. 2 and Fig. 3 is the same as Fig. 1. In Fig. 2, on the YZ plane perpendicular to the installation surface 2p, the angle that can generally be taken in the vertical direction is from -90° to +90°. As shown in Fig. 3, the first main surface 111 of the table lighting device 10 of the embodiment is configured so that the angle at which the intensity becomes maximum in the light distribution of the emitted light 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 emission surface is at maximum (i.e., the angle formed by the arrow in Fig. 3) to a range of -90° or more and less than 0°, the work area of ​​the installation surface 2p is illuminated with sufficient illuminance while preventing the emitted light from directly entering the user's eyes. This prevents the user from feeling flickering and suppresses a decrease in work efficiency.

[0020] Fig. 4 defines the horizontal angle of the table lighting device 10, and Fig. 5 shows the light distribution characteristics in the XY plane. The coordinate system in Fig. 4 and Fig. 5 is the same as Fig. 1. In Fig. 4, within the XY plane horizontal to the installation surface 2p, the angle range that can be taken in the horizontal direction is from -90° to +90°. As shown in Fig. 5, the light distribution of the emitted light from the first main surface 111 of the table lighting device 10 is within the range of -90° to +90° in the horizontal direction.

[0021] By setting the horizontal light distribution in the range of -90° to +90°, the work area of ​​the installation surface 2p can be illuminated almost uniformly, thereby improving the user's work efficiency.

[0022] 6 is a diagram showing a configuration example of the light source unit 30 of the table lighting device 10. Before describing the configuration of the light source unit 30, the overall configuration of the table lighting device 10 will be briefly described. The table lighting device 10 has a light source unit 30 and a light guide unit 300 including a light guide plate 11 that guides the light emitted from the light source unit 30. The light guide plate 11 has a light incident surface 113 that receives the light from the light source unit 30, a first main surface 111 that emits the light incident from the light incident surface 113 to the outside, and a second main surface 112 opposite to the first main surface 111.

[0023] As described above, the first main surface 111 is configured to emit light in the range of -90° or more and less than 0° in the vertical direction. It is more preferable that the first main surface 111 is configured to emit light in the range of -90° to +90° in the horizontal direction.

[0024] 6, the light incident surface 113 is located at the lower end of the light guide plate 11 in the Z direction, and the light source unit 30 is disposed below the light guide plate 11. As will be described later, the arrangement of the light source unit 30 is not limited to this example, and the light source unit 30 may be provided at a side end of the light guide plate 11.

[0025] The light source unit 30 has, for example, a light emitting element 31 housed in a housing 35 as a light source. The light emitting element 31 may be mounted on a substrate 32 and fixed to a heat dissipation unit 33 with thermally conductive double-sided tape 34. Instead of the light emitting element, an organic electroluminescence (EL) emitter or an inorganic EL emitter capable of surface emission, or a linear light source such as a fluorescent lamp or a cold cathode tube may be used.

[0026] The light guide plate 11 is held in the housing 35 by a holding member 36 so that the first main surface 111 is approximately perpendicular to the installation surface of the desk lighting device 10. The light source unit 30 together with the housing 35 may be accommodated inside a groove or slot formed in the desk 2, or the light source unit 30 together with the housing 35 may be placed on the surface of the desk 2.

[0027] <Example of light guide section configuration> Next, a configuration example of the light guide section 300 will be described. In FIG. 7A to FIG. 7C, 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. The low refractive index layer is a layer having a lower refractive index than the refractive index 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 a void disclosed in International Publication No. WO 2019 / 146628 can be used. The contents of this specification are incorporated by reference.

[0028] The visible light transmittance of the light guide plate 11 and the light guide section 300 having 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 using a spectrophotometer at a measurement wavelength of 380 nm or more and 780 nm or less.

[0029] 7A, the table lighting device 10A has a light source unit 30 and a light guide unit 300 including a light guide plate 11A. The light source unit 30 has a light emitting element 31 that emits light to the light guide plate 11A. Other configurations of the light source unit 30 are arbitrary, and for example, the configuration of FIG. 6 can be adopted.

[0030] The light guide plate 11A has a light incident surface 113 facing the light emitting element 31, a first main surface 111, and a second main surface 112, and a low refractive index layer 26 is provided on the first main surface 111. The low refractive index layer 26 may be covered with a cover layer 28a.

[0031] Light incident on light guide plate 11A from light incident surface 113 propagates in the Z direction through light guide plate 11A 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 so that the angle at which the maximum intensity is obtained in the light distribution distribution of the emitted light from the center of first main surface 111 is in the range of -90° or more and less than 0° in the YZ plane. In the horizontal direction (XY plane), the light distribution distribution of the emitted light may have a distribution in the range of -90° to +90°.

[0032] 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.

[0033] In Fig. 7B, the table lighting device 10B has a light source unit 30 and a light guide unit 300 including a light guide plate 11B. The light source unit 30 has a light emitting element 31 that emits light to the light guide plate 11B. Other configurations of the light source unit 30 are arbitrary, and for example, the configuration of Fig. 6 can be adopted.

[0034] The light guide plate 11B has a light incident surface 113 facing the light emitting element 31, a first main surface 111, and a second main surface 112, and a low refractive index layer 27 is provided on the second main surface 112. The low refractive index layer 26 may be covered with a cover layer 28b.

[0035] Light incident on light guide plate 11B from light incident surface 113 propagates through light guide plate 11B in the Z direction while being totally reflected between the interface 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 intensity becomes maximum in the light distribution distribution of the emitted light from the center of first main surface 111 is in the range of -90° or more and less than 0° in the YZ plane. In the horizontal direction (XY plane), the light distribution distribution of the emitted light may have a distribution in the range of -90° to +90°.

[0036] 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.

[0037] In Fig. 7C, the table lighting device 10C has a light source unit 30 and a light guide unit 300 including a light guide plate 11C. The light source unit 30 has a light emitting element 31 that outputs light incident on the light guide plate 11C. Other configurations of the light source unit 30 are arbitrary, and for example, the same configuration as that in Fig. 6 can be adopted.

[0038] The light guide plate 11C has a light incident surface 113 facing the light emitting element 31, a first main surface 111, and a second main surface 112. A low refractive index layer 26 is provided on the first main surface 111, and a low refractive index layer 27 is provided on the second main surface 112. The low refractive index layers 26 and 27 may be covered with cover layers 28a and 28b, respectively.

[0039] Light incident on light guide plate 11C from light incident surface 113 propagates in the Z direction through light guide plate 11C while being totally reflected between first main surface 111 on which low refractive index layer 26 is provided and second main surface 112 on which low refractive index layer 27 is provided. 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 so that the angle at which the maximum intensity is obtained in the light distribution distribution of the emitted light from the center of first main surface 111 is in the range of -90° or more and less than 0° in the YZ plane. In the horizontal direction (XY plane), the light distribution distribution of the emitted light may have a distribution in the range of -90° to +90°.

[0040] By providing low refractive index layers 26 and 27 on first main surface 111 and second main surface 112, respectively, it is possible to suppress light loss caused by stains or scratches on the main surfaces of light guide plate 11C.

[0041] 8 is a diagram for explaining the significance of providing low refractive index layers 26, 27. Consider a case where dirt C1, C2 such as sebum, sweat, etc. is attached to first main surface 111 or second main surface 112. Of the light propagating in the Z direction while being totally reflected between first main surface 111 and second main surface 112, the light incident on the position where dirt C1 or C2 is attached is scattered by dirt C1 or C2, and optical loss occurs before the light is emitted from first main surface 111.

[0042] By providing the 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 the light propagating inside the light guide plate 11 from being lost due to scattering, etc. As a result, it is possible to maintain high emission efficiency from the first main surface 111.

[0043] <Example of light exit surface configuration> Next, a configuration example of the light exit surface of the light guide plate 11 is shown. Fig. 9 is a schematic diagram of a table lighting device 10D. The table lighting device 10D has a light source unit 30 and a light guide unit 300 including a light guide plate 11D. The light source unit 30 has the configuration described with reference to Fig. 6, for example.

[0044] The light guide plate 11D has one or more optical cavities 151 therein, and the light extraction portion 15 is formed on the first main surface 111. The optical cavity 151 is a gap filled with a material having a lower refractive index than the light guide plate 11. When the gap is filled with air, it becomes an air cavity. In addition to air, the cavity may be filled with a gas, liquid, or solid material having a lower refractive index than the light guide plate 11. The optical cavity 151 is designed so that the light incident on the interface of the optical cavity 151 from the light guide plate 11D 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 visible light transmittance of light guide plate 11D and light guide unit 300 having light extraction unit 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.

[0046] The light guide plate 11D 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.

[0047] The light guide plate 11D containing the optical cavity 151 therein is 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 interfacial reflection, it is desirable that the refractive indexes of the light guide layers to be bonded together are 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.

[0048] 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.

[0049] Light guide plate 11D allows light incident on light incident surface 113 to be emitted from first main surface 111 with the above-mentioned light distribution while propagating in the Z direction by total reflection.

[0050] 10 is a schematic diagram of a table lamp 10E. The table lamp 10E has a light source unit 30 and a light guide unit 300 including a light guide plate 11E. The light guide plate 11E has a light extraction layer 16 functioning as a light extraction unit on a first main surface 111. The light extraction layer 16 has one or more optical cavities 161 formed therein.

[0051] 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 11D in Fig. 9. Alternatively, the light guide layer having the cavity pattern formed thereon may be directly bonded to the first main surface 111.

[0052] 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 11E 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.

[0053] Light incident on the light extraction layer 16 from the light guide plate 11E 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 11E is totally reflected in the direction of the outermost surface 162 of the light extraction layer 16, 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 emitted within an angle range of -90° or more and less than 0° in the YZ plane.

[0054] The light guide plate 11E allows the light incident from the light incident surface 113 to be emitted from the light extraction layer 16 with the above-mentioned light distribution while propagating in the Z direction by total reflection.

[0055] 11 is a schematic diagram of a table lamp 10F. The table lamp 10F has a light source unit 30 and a light guide unit 300 including a light guide plate 11F. The light guide plate 11F is provided with a light extraction layer 17 functioning as a light extraction unit on the second main surface 112. The light extraction layer 17 has one or more optical cavities 171 formed therein.

[0056] 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 11D in Fig. 9 and the light extraction layer 16 in Fig. 10. Alternatively, the light guide layer having the cavity pattern formed thereon may be directly bonded to the second main surface 112.

[0057] 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 11F. For example, when the light guide plate 11F 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.

[0058] The light incident on the light extraction layer 17 from the light guide plate 11F is totally reflected at the interface of the optical cavity 171, and is guided in the direction of the first main surface 111. As described above, in the first main surface 111, 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.

[0059] The light guide plate 11F can guide the light incident from the light incident surface 113 in the direction of the light extraction layer 17 toward the first main surface 111 while propagating the light in the Z direction by total reflection, and can emit the light from the first main surface 111 with the specified light distribution described above.

[0060] With any of the configurations in Figs. 9 to 11, the work area can be illuminated with sufficient illuminance, while the emitted light can be prevented from directly entering the user's eyes, and flickering can be suppressed.

[0061] 12 is a schematic diagram of a table lamp 10G. The table lamp 10G has a light guide section 300 including a light guide plate 11G. The light guide plate 11G has a prism section 251 as a light extraction section on a first main surface 111. As the prism section 251, for example, a prism sheet may be attached to the first main surface 111. In this case, it is desirable that the refractive index of the prism sheet and that of the light guide plate 11G are the same or close to each other.

[0062] 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 11G is refracted by prism portion 251 and emitted from light guide plate 11G. 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.

[0063] 13 is a schematic diagram of a table lamp 10H. The table lamp 10H has a light guide section 300 including a light guide plate 11H. The light guide plate 11H has 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 attached to the second main surface 112. In this case, it is desirable that the refractive index of the prism sheet and that of the light guide plate 11H are the same or close to each other.

[0064] 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 11H 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.

[0065] The configuration of FIG. 12 or FIG. 13 can also illuminate the work area with sufficient illuminance, prevent emitted light from directly striking the user's eyes, and suppress flickering.

[0066] FIG. 14 is a schematic diagram of a table lamp 10I. The table lamp 10I has a light guide section 300 including a light guide plate 11I. The light guide plate 11I 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.

[0067] FIG. 15 is a schematic diagram of a tabletop lighting device 10J. The tabletop lighting device 10J has a light guide section 300 including a light guide plate 11J. The light guide plate 11J 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 11J 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 not less than −90° 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.

[0068] The configuration of FIG. 14 or FIG. 15 can also illuminate the work area with sufficient illuminance, prevent emitted light from directly striking the user's eyes, and suppress flickering.

[0069] <How to use the tabletop lighting device> 16 and 17 are diagrams showing how the table lighting device 10 is used. In Fig. 16, the light incident surface 113 of the light guide plate 11 is arranged parallel to the installation surface 2p of the table lighting device 10, and the light source unit 30 is arranged to face the light incident surface 113. In the light source unit 30, a plurality of light emitting elements 31 are arranged in the X direction. The light output from each light emitting element 31 is incident on the light incident surface 113 at the lower end of the light guide plate 11, and while propagating through the light guide plate 11 in the Z direction, is output from the first main surface 111 with the light distribution shown in Fig. 3.

[0070] 17, the light incident surface 113 of the light guide plate 11 is disposed perpendicular to the installation surface 2p of the table lighting device 10, and the light source unit 30 extends in the Z direction from the installation surface 2p along the light incident surface 113 of the light guide plate 11. In the light source unit 30, a plurality of light emitting elements 31 are arranged in the Z direction. The side end surface of the light guide plate 11 facing the light emitting elements 31 of the light source unit 30 becomes the light incident surface 113.

[0071] The light output from each light-emitting element 31 enters the light incident surface 113 at the side end of the light guide plate 11, propagates through the light guide plate 11 in the X direction, and is output from the first main surface 111 with the light distribution shown in FIG. 3.

[0072] Since the light guide plate 11 is transparent to visible light, the user can see behind the light guide plate 11 whether in the usage mode of FIG. 16 or in the usage mode of FIG. 17, and an open illuminated space is provided.

[0073] 18 is a schematic diagram illustrating the effect of the table lighting device 10. In the table lighting device 10, illumination light is emitted in the range of -90° or more and less than 0° in the vertical direction. The emitted light illuminates the user's work surface and hands with uniform brightness. The user can view the work surface and also see behind the table lighting device 10 through the table lighting device 10.

[0074] On the other hand, as indicated by the cross marks, the light emitted from the desk lamp 10 is hardly visible directly, thus reducing the flickering sensation and maintaining work efficiency.

[0075] Although the present invention has been described above based on specific configuration examples, the present invention is not limited to the above configuration examples. The configurations of Figs. 7A to 7C in which a low refractive index layer is provided and the light extraction configurations of Figs. 9 to 15 may be arbitrarily combined. The arrangement direction of the light emitting elements 31 of the light source unit 30 may be either horizontal or vertical. In either case, an open lighting space with reduced oppressive feeling and light flicker is realized by emitting light from a transparent light guide plate in a direction that is difficult for the user to directly view.

[0076] This application claims priority based on Japanese Patent Application No. 2020-127348 filed on July 28, 2020, and includes the entire contents of this Japanese patent application. [Explanation of symbols]

[0077] 2p installation surface 10, 10A~10J Tabletop lighting device 11, 11A~11J Light guide plate 111 First main surface 112 Second main surface 113 Light incidence surface 15 Light extraction section 151 Optical Cavity 16, 17 Light extraction layer 161, 171 Optical cavity (air gap) 162 Outermost surface 26, 27 Low refractive index layer 28a, 28b Cover layer 30 Light source section 31 Light emitting element 251, 252 Prism part 253, 254 Uneven part 300 Light guide section

Claims

1. A desk lighting device having a light source and a light guide portion including a light guide plate for guiding light emitted from the light source, the light guide plate has a light incident surface through which light from the light source is incident, a first main surface through which the light incident from the light incident surface is emitted, and a second main surface opposite to the first main surface; The first main surface is disposed substantially perpendicular to a surface on which the desk lighting device is installed, an axis passing through the center of the first main surface and perpendicular to the installation surface is defined as a vertical axis, and within a plane including the vertical axis and perpendicular to the installation surface, a direction parallel to the installation surface is defined as vertical 0°, an angle upward from the parallel direction is defined as a positive angle, and an angle downward from the parallel direction is defined as a negative angle, in a light distribution distribution of light emitted from the first main surface, an angle at which the intensity is maximum is equal to or greater than −90° and less than 0°, The light guiding portion is transparent to visible light, The back of the light guiding section is visible through the light. Tabletop lighting device.

2. The light guide plate has an upper end surface, a lower end surface, and a pair of opposing side surfaces extending vertically between the lower end surface and the upper end surface; The desk lighting device according to claim 1 , wherein the light incident surface is one of the pair of opposing side surfaces of the light guide plate or the lower end surface of the light guide plate.

3. The light guiding section has a low refractive index layer having a refractive index lower than that of the light guiding plate on at least one of the first principal surface and the second principal surface, the light guide portion has a light extraction portion that outputs the light propagating through the light guide plate from the first main surface with the light distribution, 3. The table lighting device according to claim 1, wherein the light extraction portion is one or more gaps provided inside the light guide plate, and the gaps totally reflect the light propagating through the light guide plate and emit the light with the light distribution from the first main surface.

4. The light guiding section has a low refractive index layer having a refractive index lower than that of the light guiding plate on at least one of the first principal surface and the second principal surface, the light guide portion has a light extraction portion that outputs the light propagating through the light guide plate from the first main surface with the light distribution, the light extraction portion is a light extraction layer disposed on the first main surface, 3. The desk lighting device according to claim 1, wherein the light extraction layer has one or more voids that totally reflect light incident on the light extraction layer from the light guide plate and emit the light from an outermost surface of the light extraction layer.

5. 5. The table lighting device according to claim 1, wherein, in the first principal surface, an axis that passes through a center of the first principal surface and is horizontal to the installation surface is defined as a horizontal axis, 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 installation surface and is perpendicular to the light exit surface is defined as horizontal 0°, and when the parallel plane is viewed from the opposite side to the installation surface, a clockwise direction from the 0° direction is defined as a positive angle and a counterclockwise direction is defined as a negative angle, such that a horizontal light distribution of light exiting from the center of the first principal surface is within a range of -90° to +90°.

6. The desk lighting 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.

7. The desk lighting device according to claim 6 , wherein the light guiding portion has the low refractive index layer on both the first main surface and the second main surface.

8. The desk lighting device according to claim 6 , wherein the light guide portion includes a light extraction portion that emits the light propagating through the light guide plate from the first main surface with the light distribution.

9. 9. The table lighting device of claim 8, wherein the light extraction portion is a light extraction layer disposed on the second main surface, and the light extraction layer has one or more gaps that totally reflect light incident on the light extraction layer from the light guide plate and emit the light in the direction of the first main surface.

10. The desk lighting device according to claim 8 , 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.

11. The table lighting device according to any one of claims 1 to 10, wherein the light incident surface of the light guide plate is arranged parallel to the installation surface.

12. The table lighting device according to any one of claims 1 to 10, wherein the light incident surface of the light guide plate is arranged perpendicular to the installation surface.

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