Desk lighting device

Abstract

A desk illuminating device with reduced sense of oppression and light flicker is provided. The desk illuminating device has a light source and a light guide portion including a light guide plate and guiding light emitted from the light source, wherein the light guide plate has a light incident surface for light from the light source to be incident, a first main surface that emits light incident from the light incident surface, and a second main surface opposite the first main surface, the first main surface is arranged substantially perpendicular to a setting surface of the desk illuminating device, when an axis that passes through the center of the first main surface and is perpendicular to the setting surface is set as a vertical axis, a direction parallel to the setting surface is set as 0° vertical in a surface that contains the vertical axis and is perpendicular to the setting surface, an angle upward compared to the parallel direction is set as a positive angle, and an angle downward compared to the parallel direction is set as a negative angle, an angle that becomes the maximum intensity in the light distribution of light emitted from the first main surface is 90° or more and less than 0°.

Description

TECHNICAL FIELD

[0001] The present application relates to a table illuminating device. BACKGROUND

[0002] Lighting devices using light emitting diodes (LEDs) are becoming widespread. In the case of LED lighting, since the light beam obtained from one LED is small, a plurality of LEDs are generally used in concentration. In such LED lighting, the phenomenon of "multiple shadows" in which the number of light sources is shadowed, which is a cause of flicker, occurs.

[0003] A directivity lighting device which changes light from an LED into planar or linear light emission having directivity has been proposed (for example, refer to Patent Literature 1). In this lighting device, one side or opposite sides of a light guide body composed of a transparent member are disposed as incident sides of an LED light source.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2009-110783 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the desk lamp disclosed in Patent Literature 1, the illuminating portion is located above the desk, and the light emission surface faces downward. Since the illuminating appliance exists, the user sometimes feels oppressed. In addition, since the illuminating light can be directly seen, there is a risk of a decrease in concentration due to flicker.

[0009] An object of the present application is to provide a table illuminating device which reduces the feeling of oppression and flicker of light.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] In one aspect of the present application, a table illuminating device has a light source and a light guide portion including a light guide plate and guiding light emitted from the light source, wherein

[0012] the light guide plate has a light incident surface for light from the light source to be incident, a first main surface which emits the light incident from the light incident surface, and a second main surface which opposes the first main surface,

[0013] the first main surface is disposed substantially perpendicularly to a placement surface of the table illuminating device,

[0014] When an axis passing through the center of the first main surface and perpendicular to the placement surface is set as a vertical axis, an angle of a direction parallel to the placement surface is set as a vertical 0° in a plane containing the vertical axis and perpendicular to the placement surface, an angle upward compared to the parallel direction is set as a positive angle, and an angle downward compared to the parallel direction is set as a negative angle, an angle of maximum intensity in a light distribution of light emitted from the first main surface is -90° or more and less than 0°.

[0015] Effects of Invention

[0016] With the above structure, a user does not feel oppressed, and flickering of light is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is an appearance view of a table top lighting device of an embodiment.

[0018] Figure 2 is a view defining an angle of a vertical direction with respect to a placement surface.

[0019] Figure 3 is a view showing a light distribution characteristic in a Y-Z plane.

[0020] Figure 4 is a view defining an angle of a horizontal direction with respect to a placement surface.

[0021] Figure 5 is a view showing a light distribution characteristic in an X-Y plane.

[0022] Figure 6 is a view showing a structure example of a light source section.

[0023] Figure 7A is a view showing a structure example of a light guide plate.

[0024] Figure 7B is a view showing another structure example of a light guide plate.

[0025] Figure 7C is a view showing another structure example of a light guide plate.

[0026] Figure 8 is a view explaining the significance of providing a low refractive index layer.

[0027] Figure 9 is a view showing still another structure example of a light guide plate.

[0028] Figure 10 is a view showing still another structure example of a light guide plate.

[0029] Figure 11 is a view showing still another structure example of a light guide plate.

[0030] Figure 12 is a view showing another example of the light guide plate.

[0031] Figure 13 is a view showing another example of the light guide plate.

[0032] Figure 14 is a view showing another example of the light guide plate.

[0033] Figure 15 is a view showing another example of the light guide plate.

[0034] Figure 16 is a view showing a setting mode of the table illuminating device.

[0035] Figure 17 is a view showing a setting mode of the table illuminating device.

[0036] Figure 18 is a view showing an effect of the table illuminating device. DETAILED DESCRIPTION

[0037] In the embodiment, in order to realize the table illumination in which the user does not feel oppressive and flickering of light, a light guide portion including a light guide plate and having transmittance for visible light is used. The first main surface of the light guide plate, which becomes a light exit surface, is arranged perpendicularly to a setting surface of the table illuminating device. When the table illuminating device is used, the user can see through the back of the light guide portion, and the sense of obstruction and the sense of oppression are reduced. By making the distribution of light emitted from the light exit surface have a prescribed orientation, the irradiated light is prevented from being directly seen by the user, and flickering is reduced.

[0038] Figure 1 is an appearance view of the table illuminating device 10 of the embodiment. The table illuminating device 10 is placed on an office table, a dining table, or the like (hereinafter, collectively referred to as "table 2"). A surface on which the table illuminating device 10 is placed is set as a "setting surface 2p". A surface parallel to the setting surface 2p is set as an X-Y surface, and a direction orthogonal to the X-Y surface is set as a Z direction. The height direction of the table illuminating device 1 is the Z direction, and the width direction is the X direction. The light exit direction is set as the Y direction.

[0039] The table illuminating device 10 has a light guide portion 300 including a light guide plate 11 and guiding light from a light source. In Figure 1 the light source is omitted, and the light source can be housed inside a groove or a slit formed in the setting surface 2p or can be located on the setting surface 2p together with the light guide plate 11. The structure example of the light source will be described later.

[0040] The light guide plate 11 is a solid that is transparent to visible light and is formed of glass, plastic, or the like. As a glass material, quartz glass, alkali-free glass, borosilicate glass, or the like can be used. As a plastic material, an acrylic resin (for example, polymethyl methacrylate (PMMA)), a polycarbonate (PC) resin, a cyclic olefin (COP) resin, or the like can be used. 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 determined as an average 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.

[0041] The light guide plate 11 has a first main surface 111 from which light is emitted. The first main surface 111 is substantially perpendicular to the placement surface 2p. When referring to "substantially perpendicular", an error of about ±5° can be included with respect to perpendicular. Light emitted from the first main surface 111 has a light distribution that is deflected downward compared to a direction parallel to the placement surface 2p. As long as this light distribution is satisfied, the first main surface 111 can also include an error of about ±5° with respect to perpendicular.

[0042] In the first main surface 111, an axis that passes through the center C of the first main surface 111 and is perpendicular to the placement surface 2p is set as a vertical axis or V-axis. In a Y-Z plane that includes the V-axis and is perpendicular to the placement surface 2p, a direction parallel to the placement surface 2p is set as 0° vertically. An angle that is upward in the Y-Z plane compared to 0° vertically is set as a positive angle, and an angle that is downward is set as a negative angle.

[0043] If the light distribution of the emitted light from the center C on the X-Z plane orthogonal to the placement surface 2p is considered, light can generally be emitted in a range from -90° to +90°. In contrast, in the desk lighting device 10, an angle that becomes the maximum intensity in the light distribution of the emitted light from the center of the first main surface 111 is set in a range of -90° or more (for example, more than -90°) and less than 0°. For example, the upper limit thereof is -0.1°, -1°, -5°, -10°, -10°, -20°, -30°, -40°, -50°, -60°, -70°, -80°, -85°, -88°, -89°, and the lower limit thereof is -90°, -89°, -88°, -85°, -80°, -70°, -60°, -50°, -40°, -30°, -20°, -10°, -5°, -1°, and the value of the lower limit does not exceed the value of the upper limit. Furthermore, the light distribution of the emitted light can be measured using a field angle measuring device (for example, a luminance field angle measuring device EZContrast XL88 manufactured by ELDIM).

[0044] In the first main surface 111, an axis passing through the center C and horizontal to the placement surface 2p is set as a horizontal axis or H-axis. An angle from the center C of the first main surface 111 toward the Y direction is set as horizontal 0°. In addition, in a case where the X-Y plane passing through the center C is observed from the side opposite to the placement surface (or above the placement surface), an angle clockwise from the horizontal 0° is set as a positive angle, and an angle counterclockwise is set as a negative angle. In the X-Y plane, a horizontal direction distribution of light emitted from the first main surface 111 is in a range from -90° to +90°, for example, in a range exceeding -90° and less than +90°, for example, a lower limit thereof is -90°, -89°, -88°, -85°, -80°, -70°, -60°, -50°, -40°, -30°, -20°, -10°, and an upper limit thereof is +90°, +89°, +88°, +85°, +80°, +70°, +60°, +50°, +40°, +30°, +20°, +10°. The desk lighting device 10 can also be a substantially uniform light distribution in the horizontal direction.

[0045] Figure 2 is a graph defining an angle in the vertical direction of the desk lighting device 10, Figure 3 is a graph showing a light distribution characteristic in the Y-Z plane. Figure 2 and Figure 3 The coordinate system of Figure 1 is the same as Figure 2 In Figure 3 , in the Y-Z plane perpendicular to the placement surface 2p, a generally acceptable angle range in the vertical direction is -90° to +90°. As indicated, the first main surface 111 of the desk lighting device 10 of the embodiment is configured so that an angle at which the light distribution of the emitted light becomes the maximum intensity is in a range of -90° or more and less than 0°.

[0046] By setting the angle at which the light distribution of the emitted light from the center of the emission surface becomes the maximum intensity (i.e., the angle formed by the arrow of Figure 3 ) in a range of -90° or more and less than 0°, the work area of the placement surface 2p is irradiated with sufficient illuminance, and direct incidence of the emitted light into the user's eyes is prevented. Thereby, the user is prevented from feeling flicker, and reduction in work efficiency is suppressed.

[0047] Figure 4 is a graph defining an angle in the horizontal direction of the desk lighting device 10, Figure 5 is a graph showing a light distribution characteristic in the X-Y plane. Figure 4 and Figure 5 The coordinate system of Figure 1 is the same as Figure 4In the X-Y plane that is horizontal to the placement surface 2p, the range of the angle that is preferable in the horizontal direction is -90° to +90°. As for the first main surface 111 of the desk lighting device 10, as shown in Figure 5 the light distribution of the emitted light is in the range of -90° to +90° in the horizontal direction.

[0048] By setting the light distribution in the horizontal direction in the range of -90° to +90°, the work area of the placement surface 2p can be roughly uniformly illuminated, and the work efficiency of the user can be improved.

[0049] Figure 6 is a view that shows a structure example of the light source section 30 of the desk lighting device 10. Before explaining the structure of the light source section 30, the overall structure of the desk lighting device 10 will be explained. The desk lighting device 10 has the light source section 30 and a light guide section 300 that contains the light guide plate 11 and guides the light emitted from the light source section 30. The light guide plate 11 has a light incident surface 113 that is incident with the light from the light source section 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 that opposes the first main surface 111.

[0050] 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 if the first main surface 111 is configured to emit light in the range of -90° to +90° in the horizontal direction.

[0051] In the example of Figure 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 section 30 is disposed below the light guide plate 11. As will be described later, the disposition of the light source section 30 is not limited to this example, and it can be disposed at the side end portion of the light guide plate 11.

[0052] The light source section 30 has, for example, a light emitting element 31 housed in a housing 35 as a light source. The light emitting element 31 can also be mounted on a substrate 32 and fixed to a heat dissipation section 33 by a thermally conductive double-sided tape 34. Instead of the light emitting element, an organic electroluminescence (EL) light emitter, an inorganic EL light emitter, or a linear light source such as a fluorescent lamp, a cold cathode tube, or the like that can perform surface emission can be used.

[0053] The light guide plate 11 is held to the housing 35 by a holding member 36 in such a manner that the first main surface 111 is substantially perpendicular to the placement surface of the desk lighting device 10. The light source section 30 can house the entire housing 35 inside a groove or a slit formed in the desk 2, or the entire housing 35 can be placed on the surface of the desk 2.

[0054] Structure Example of Light Guide Section

[0055] Next, a structure example of the light guide section 300 will be explained. In the example ofFigure 7A-7C In the light guide portion 300, at least one of the first main surface 111 and the second main surface 112 of the light guide plate 11 has a low refractive index layer with a lower refractive index than the light guide plate 11. The low refractive index layer is a layer with a lower refractive index relative to the refractive index of the light guide plate 11. When the light guide plate 11 is configured to mainly contain PMMA, the refractive index n1 of the light guide plate 11 is around 1.49. In contrast, the refractive index n2 of the low refractive index layer is preferably 1.30 or less, more preferably 1.20 or less. There are no particular limitations on the low refractive index layer; for example, a low refractive index layer with gaps disclosed in International Publication No. 2019 / 146628 can be used. This content is incorporated herein by reference.

[0056] The visible light transmittance of the light guide portion 300, which has a light guide plate 11 and a 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. Visible light transmittance is defined as the average transmittance at various wavelengths measured using a spectrophotometer at a measurement wavelength of 380 nm or more and 780 nm or less.

[0057] exist Figure 7A In this tabletop lighting device 10A, there is a light source section 30 and a light guide section 300 including a light guide plate 11A. The light source section 30 has a light-emitting element 31 that emits light through the light guide plate 11A. Other structures of the light source section 30 are arbitrary; for example, it can employ... Figure 6 The structure.

[0058] The light guide plate 11A has a light incident surface 113 opposite to 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 also be covered by a cover layer 28a.

[0059] Light incident from the light incident surface 113 onto the light guide plate 11A undergoes total internal reflection between the first principal surface 111 and the second principal surface 112, where the low-refractive-index layer 26 is provided, and propagates along the Z-direction in the light guide plate 11A. Light incident at the interface between the first principal surface 111 and the low-refractive-index layer 26 that does not satisfy the total internal reflection condition is emitted from the first principal surface 111 at an angle greater than -90° and less than 0° in the YZ plane, where the light distribution from the center of the first principal surface 111 has the angle of maximum intensity. In the horizontal direction (XY plane), the light distribution of the emitted light can also have a range from -90° to +90°.

[0060] By providing a low refractive index layer 26 on the first main surface 111, light loss caused by dirt or scratches on the light-emitting surface can be suppressed.

[0061] exist Figure 7BIn this tabletop lighting device 10B, there is a light source section 30 and a light guide section 300 including a light guide plate 11B. The light source section 30 has a light-emitting element 31 that emits light through the light guide plate 11B. Other structures of the light source section 30 are arbitrary; for example, it can employ... Figure 6 The structure.

[0062] The light guide plate 11B has a light incident surface 113 opposite to 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 also be covered by a cover layer 28b.

[0063] Light incident on the light guide plate 11B from the light incident surface 113 undergoes total internal reflection at the interface between the first principal surface 111 and the second principal surface 112, which has a low refractive index layer 27, and propagates along the Z-direction in the light guide plate 11B. Light incident on the first principal surface 111 that does not satisfy the total internal reflection condition exits from the first principal surface 111 at an angle greater than -90° and less than 0° in the YZ plane, where the light distribution from the center of the first principal surface 111 results in the angle of maximum intensity. In the horizontal direction (XY plane), the light distribution of the exited light can also have a range from -90° to +90°.

[0064] By providing a low-refractive-index layer 27 on the second main surface 112, light loss caused by dirt or scratches on the second main surface 112 can be suppressed, and light can be efficiently directed toward the first main surface 111.

[0065] exist Figure 7C In this tabletop lighting device 10C, there is a light source section 30 and a light guide section 300 including a light guide plate 11C. The light source section 30 has a light-emitting element 31 that outputs light incident on the light guide plate 11C. Other structures of the light source section 30 are arbitrary; for example, it can adopt a configuration similar to... Figure 6 Same structure.

[0066] The light guide plate 11C has a light incident surface 113 opposite to 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 also be covered by cover layers 28a and 28b, respectively.

[0067] The light incident to the light guide plate 11C from the light incident surface 113 is totally reflected between the first main surface 111 provided with the low refractive index layer 26 and the second main surface 112 provided with the low refractive index layer 27, and propagates in the Z direction in the light guide plate 11C. The light of the light incident to the boundary surface of the first main surface 111 and the low refractive index layer 26, which does not satisfy the total reflection condition, is emitted in a range of -90° or more and less than 0° in the Y-Z plane in a manner that the angle becomes the maximum intensity in the distribution of the emitted light from the center of the first main surface 111. In the horizontal direction (X-Y plane), the distribution of the emitted light can also have a distribution in a range of -90° to +90°.

[0068] By providing the low refractive index layers 26 and 27 to the first main surface 111 and the second main surface 112, respectively, it is possible to suppress the light loss caused by dirt or scratches on the main surfaces of the light guide plate 11C.

[0069] Figure 8 is a diagram for explaining the meaning of providing the low refractive index layers 26 and 27. Consider a case where dirt C1, C2 such as sebum or sweat adheres to the first main surface 111 or the second main surface 112. Of the light propagating in the Z direction while being totally reflected between the first main surface 111 and the second main surface 112, the light incident to the position where the dirt C1 or C2 adheres is scattered due to the dirt C1 or C2, and light loss occurs before being emitted from the first main surface 111.

[0070] By providing the low refractive index layer 26 or 27 to 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 or the like. As a result, it is possible to maintain the emission efficiency from the first main surface 111 at a high level.

[0071] <Structure Example of Light Emitting Surface>

[0072] Next, a structure example of the light emitting surface of the light guide plate 11 is shown. Figure 9 is a schematic view of the desk illuminating device 10D. The desk illuminating device 10D has a light source section 30 and a light guide section 300 including a light guide plate 11D. The light source section 30 has, for example, the structure described with reference to Figure 6

[0073] ​The light guide plate 11D has one or more optical resonators 151 inside, and a light extraction portion 15 is formed on the first main surface 111. The optical resonator 151 is a void filled with a material having a lower refractive index than the light guide plate 11. In the case where the void is filled with air, it is an air resonator. Instead of air, a gas, a liquid, or a solid material having a lower refractive index than the light guide plate 11 can be filled. The optical resonator 151 is designed so that light incident on the interface of the optical resonator 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 of the light distribution of the light emitted from the center of the first main surface 111 becomes maximum is in the range of -90° or more and less than 0° in the Y-Z plane.

[0074] The visible light transmittance of the light guide portion 300 having the light guide plate 11D and the light extraction portion 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 determined as the average 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.

[0075] In the light guide plate 11D, a plurality of optical resonators 151 are regularly or randomly provided along the plane of the first main surface 111. The size of the optical resonator 151 can be appropriately selected within a range that can be provided inside the light guide plate 11E. The light guide plate having the optical resonator inside is not particularly limited, and 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 thereof are incorporated into the present application by reference.

[0076] The light guide plate 11D having the optical resonator 151 inside can be manufactured, for example, by laminating a light guide layer having a desired cavity pattern formed on the surface and a flat light guide layer having no cavity pattern, and then adhering them together. The light guide layers are adhered to each other by lamination such as a non-adhesive microwave surface treatment, or by pressure bonding with an adhesive (including a pressure-sensitive adhesive). In order to suppress interface reflection, it is desirable that the refractive indices of the light guide layers to be adhered are substantially equal. In the case of using an adhesive, an adhesive having a refractive index substantially equal to that of the light guide layers is preferably used.

[0077] The formation of the cavity pattern light guide layer is performed by laser patterning, direct laser imaging, laser drilling, laser irradiation with or without a mask, electron beam irradiation, or the like. As other methods, a separate property (change in refractive index value or the like) can also be imparted to a portion that becomes the optical resonator 151 by printing, inkjet printing, screen printing, or the like. Micron / nanometer dispensing, dosing, direct writing, discrete laser sintering, micro-EDM (Electro-Discharge Machining), micro-machining, micro-forming, embossing, embossing processing, and methods similar thereto can also be used.

[0078] With the light guide plate 11D, light incident from the light incident surface 113 can be made to propagate in the Z direction by total reflection while being emitted from the first major surface 111 with the above-described light distribution.

[0079] Figure 10 is a schematic view of a desk lamp 10E. The desk lamp 10E has a light source section 30 and a light guide section 300 including a light guide plate 11E. The light guide plate 11E is provided with a light extraction layer 16 that functions as a light extraction section on the first major surface 111. One or more optical resonators 161 are formed in the light extraction layer 16.

[0080] As with the light guide plate 11D of Figure 9 The light extraction layer 16 having the optical resonator 161 can be formed by pasting together a flat light guide layer having no cavity pattern and a light guide layer having a cavity pattern formed on the surface, or the light guide layer having the cavity pattern can be directly attached to the first major surface 111.

[0081] From the viewpoint of suppressing unwanted refraction and reflection, the refractive index of the light extraction layer 16 and the refractive index of the light guide plate 11E are desirably the same or close. For example, when the light guide plate 11E is formed of PMMA, the light extraction layer 16 is formed of a material having the same or close refractive index as PMMA.

[0082] Light incident from the light guide plate 11E to the light extraction layer 16 is totally reflected at the interface of the optical resonator 161 and emitted from the outermost surface 162 of the light extraction layer 16. The interface of the optical resonator 161 is designed so that light incident from the light guide plate 11E is totally reflected toward the outermost surface 162 of the light extraction layer 16, and the angle of the light distribution of the emitted light from the center of the first major surface 111 that becomes the maximum intensity is in the range of angles of -90° or more and less than 0° in the Y-Z plane.

[0083] With the light guide plate 11E, light incident from the light incident surface 113 can be made to propagate in the Z direction by total reflection while being emitted from the light extraction layer 16 with the above-described light distribution.

[0084] With the light guide plate 11E, light incident from the light incident surface 113 can be made to propagate in the Z direction by total reflection while being emitted from the light extraction layer 16 with the above-described light distribution.Figure 11 is a schematic view of a desk illuminating device 10F. The desk illuminating device 10F has a light source section 30 and a light guiding section 300 including a light guide plate 11F. The light guide plate 11F is provided with a light extraction layer 17 as a light extraction section on a second main surface 112. One or more light resonance cavities 171 are formed in the light extraction layer 17.

[0085] The light extraction layer 17 having the light resonance cavities 171 can be formed by sticking together a flat light guiding layer having no cavity pattern and a light guiding layer having a cavity pattern formed on a surface, as with the light extraction layer 16 of the desk illuminating device 10D and the light guide plate 11D of the desk illuminating device 10E. Figure 9 The light extraction layer 17 having the light resonance cavities 171 can be formed by sticking together a flat light guiding layer having no cavity pattern and a light guiding layer having a cavity pattern formed on a surface, as with the light extraction layer 16 of the desk illuminating device 10D and the light guide plate 11D of the desk illuminating device 10E. Figure 10 The light extraction layer 17 having the light resonance cavities 171 can be formed by sticking together a flat light guiding layer having no cavity pattern and a light guiding layer having a cavity pattern formed on a surface, as with the light extraction layer 16 of the desk illuminating device 10D and the light guide plate 11D of the desk illuminating device 10E.

[0086] From the viewpoint of suppressing undesirable refraction and reflection, the refractive index of the light extraction layer 17 and the refractive index of the light guide plate 11F are desirably the same or close to each other. For example, when the light guide plate 11F is formed of polymethyl methacrylate (PMMA), the light extraction layer 17 is formed of a material having the same or close to the refractive index as PMMA.

[0087] Light incident from the light guide plate 11F to the light extraction layer 17 is totally reflected at the interface of the light resonance cavities 171 and guided toward the first main surface 111. In the first main surface 111, as described above, the angle that becomes the maximum intensity in the distribution of the emitted light from the center of the first main surface 111 is -90° or more and less than 0° in the Y-Z plane.

[0088] With the light guide plate 11F, it is possible to propagate light incident from the light incident surface 113 in the Z direction by total reflection while guiding the light toward the first main surface 111 from the light extraction layer 17, and emit the light from the first main surface 111 with the above-described prescribed distribution of light.

[0089] With any of the structures of the desk illuminating devices 10D, 10E, and 10F, it is possible to irradiate the work area with sufficient illuminance and prevent direct incidence of the emitted light to the user's eyes, suppressing flicker. Figure 9-11

[0090] Figure 12 is a schematic view of a desk illuminating device 10G. The desk illuminating device 10G has a light guiding section 300 including a light guide plate 11G. The light guide plate 11G is provided with a prismatic section 251 as a light extraction section on the first main surface 111. As the prismatic section 251, for example, a prismatic sheet can be stuck to the first main surface 111. In this case, the refractive index of the prismatic sheet and the light guide plate 11G desirably are the same or close to each other.

[0091] ​The size, number of inclined surfaces, and the like of the prism portion 251 can be appropriately selected within a range in which the prism portion 251 can be disposed on the first main surface 111. Light incident on the prism portion 251 from the light guide plate 11G is refracted by the prism portion 251 and emitted from the light guide plate 11G. The angle and pitch of the inclined surfaces of the prism portion 251 are designed as described above so that 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 -90° or more and less than 0° in the Y-Z plane.

[0092] Figure 13 FIG. 17 is a schematic view of a desk lighting device 10H. The desk lighting device 10H has a light guide portion 300 including a light guide plate 11H. The light guide plate 11H has a prism portion 252 as a light extraction portion on the second main surface 112. As the prism portion 252, for example, a prism sheet can be attached to the second main surface 112. In this case, the refractive index of the prism sheet is desirably the same as or close to that of the light guide plate 11H.

[0093] The size, number of inclined surfaces, and the like of the prism portion 252 can be appropriately selected within a range in which the prism portion 252 can be disposed on the second main surface 112. Light incident on the prism portion 252 from the light guide plate 11H is refracted by the prism portion 252 toward the first main surface 111 and emitted from the first main surface 111. The angle and pitch of the inclined surfaces of the prism portion 252 are designed as described above so that 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 -90° or more and less than 0° in the Y-Z plane.

[0094] With the structure of Figure 12 or Figure 13 , it is possible to irradiate the work area with sufficient illuminance and prevent the emitted light from directly entering the user's eyes, thereby suppressing flicker.

[0095] Figure 14 FIG. 18 is a schematic view of a desk lighting device 101. The desk lighting device 101 has a light guide portion 300 including a light guide plate 11I. The light guide plate 11I has a concave-convex portion 253 as a light extraction portion on the first main surface 111. The concave-convex portion 253 has a plurality of convex portions or concave portions each having a width (or diameter) and a height of about 1 to 5 μm. The concave-convex portion 253 is designed so that 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 -90° or more and less than 0° in the Y-Z plane. As the concave-convex portion 253, an optical film in which concave portions and convex portions satisfying the above conditions are formed can be used.

[0096] Figure 15is a schematic view of a desk lighting device 10J. The desk lighting device 10J has a light guide portion 300 including a light guide plate 11J. The light guide plate 11J is provided with a concave-convex portion 254 as a light extraction portion on a second main surface 112. The concave-convex portion 254 has a plurality of convex portions or concave portions with a width (or diameter) and a height of about 1 to 5 μm. The concave-convex portion 254 causes light incident on the concave-convex portion 254 from the light guide plate 11J to be deflected toward the direction of the first main surface 111 and emitted from the first main surface 111. The concave-convex portion 254 is designed so that the angle at which the intensity of emitted light from the center of the first main surface 111 becomes maximum in the light distribution is -90° or more and less than 0° in the Y-Z plane. As the concave-convex portion 254, an optical film in which concave portions and convex portions satisfying the above condition are formed can also be used.

[0097] By the structure of Figure 14 or Figure 15 , it is also possible to irradiate the work area with sufficient illuminance and prevent direct incidence of emitted light rays on the user's eyes, suppressing flicker.

[0098] <Usage Modes of Desk Lighting Device>

[0099] Figure 16 and Figure 17 are views showing usage modes of a desk lighting device 10. In Figure 16 , a light incident surface 113 of a light guide plate 11 is arranged in parallel with a setting surface 2p of the desk lighting device 10, and a light source portion 30 is arranged in opposition to the light incident surface 113. In the light source portion 30, a plurality of light emitting elements 31 are arranged in the X direction. Light output from each light emitting element 31 is incident on the light incident surface 113 of the lower end of the light guide plate 11, propagates in the light guide plate 11 in the Z direction while being diffused, and is output from the first main surface 111 in the light distribution shown in Figure 3 .

[0100] In Figure 17 , the light incident surface 113 of the light guide plate 11 is arranged perpendicularly to the setting surface 2p of the desk lighting device 10, and the light source portion 30 is arranged so as to extend in the Z direction from the setting surface 2p along the light incident surface 113 of the light guide plate 11. In the light source portion 30, a plurality of light emitting elements 31 are arranged in the Z direction. The side end surface of the light guide plate 11 opposite to the light emitting elements 31 of the light source portion 30 is the light incident surface 113.

[0101] Light output from each light emitting element 31 is incident on the light incident surface 113 of the side end portion of the light guide plate 11, propagates in the light guide plate 11 in the X direction while being diffused, and is output from the first main surface 111 in the light distribution shown in Figure 3 .

[0102] Since the light guide plate 11 is transparent to visible light, it is possible to use the desk lighting device 10 in either of the usage modes, the Figure 16 , or the Figure 17The user can see the back of the light guide plate 11, providing an open lighting space.

[0103] Figure 18 is a schematic view illustrating the effect of the table illuminating device 10. In the table illuminating device 10, the illuminating light is emitted in the vertical direction to a range of -90° or more and less than 0°. The emitted light illuminates the user's work surface and handsides with uniform brightness. The user can see the work surface, and can also see the back of the table illuminating device 10 through the table illuminating device 10.

[0104] On the other hand, as indicated by the cross mark, the light emitted from the table illuminating device 10 is hardly directly seen. Thus, the sense of flicker can be reduced, maintaining the work efficiency.

[0105] The above, based on a specific configuration example, the present application is described, but the present application is not limited to the above-described configuration example. Also can be set to Figure 7A-7C the structure of the low refractive layer with Figure 9-15 the light extraction structure of the table illuminating device 10. The arrangement direction of the light emitting element 31 of the light source portion 30 can be horizontal direction, can also be vertical direction. In either case, by emitting light from the transparent light guide plate to the direction that the user is difficult to directly see, an open lighting space with reduced sense of oppression, flicker of light can be achieved.

[0106] This application is based on Japanese Patent Application No. 2020-127348 filed on July 28, 2020, which is hereby incorporated by reference in its entirety.

[0107] Explanation of Reference Signs

[0108] 2p Setting surface

[0109] 10, 10A to 10J Table illuminating device

[0110] 11, 11A to 11J Light guide plate

[0111] 111 First main surface

[0112] 112 Second main surface

[0113] 113 Light incident surface

[0114] 15 Light extraction portion

[0115] 151 Light resonator (void)

[0116] 16, 17 Light extraction layer

[0117] 161, 171 Light resonator (void)

[0118] 162 Outermost surface

[0119] 26, 27 low refractive index layer

[0120] 28a, 28b cover layer

[0121] 30 light source portion

[0122] 31 light emitting element

[0123] 251, 252 prism portion

[0124] 253, 254 concave-convex portion

[0125] 300 light guide portion

Claims

1. A desktop lighting device comprising a light source and a light guide portion including a light guide plate for guiding light emitted from the light source, wherein, The light guide plate has a light incident surface for light from the light source to be incident on, a first main surface for light incident from the light incident surface to be emitted out, and a second main surface opposite to the first main surface. The first main surface is configured approximately perpendicular to the surface on which the desktop lighting device is mounted. When an axis passing through the center of the first main surface and perpendicular to the setting surface is defined as the vertical axis, and a direction parallel to the setting surface within a plane containing the vertical axis and perpendicular to the setting surface is defined as 0°, an upward angle relative to the parallel direction is defined as a positive angle, and a downward angle relative to the parallel direction is defined as a negative angle, the angle at which the light distribution emitted from the first main surface reaches maximum intensity is greater than -90° and less than 0°. The light guide portion is transmissive to visible light. It allows for a through-view observation of the back of the light guide section.

2. The desktop lighting device as claimed in claim 1, wherein, If an axis passing through the center of the first main surface and horizontal to the setting surface is defined as a horizontal axis in the first main surface, then when the direction from the center of the light emitting surface toward the light emitting side and orthogonal to the light emitting surface in a surface containing the horizontal axis and parallel to the setting surface is defined as horizontal 0°, and when the parallel surface is viewed from the side opposite to the setting surface, the direction clockwise from the 0° direction is defined as a positive angle, and the direction counterclockwise is defined as a negative angle, the horizontal light distribution of the emitted light from the center of the first main surface is in the range of -90° to +90°.

3. The desktop lighting device as described in claim 1 or 2, wherein, The light guide portion has a low refractive index layer with a lower refractive index than the light guide plate on at least one of the first main surface and the second main surface.

4. The desktop lighting device as described in claim 3, wherein, The light guide portion has the low refractive index layer on both the first main surface and the second main surface.

5. The desktop lighting device as described in claim 1 or 2, wherein, The light guide portion has a light extraction portion that emits light propagating in the light guide plate from the first main surface in the light distribution.

6. The desktop lighting device as claimed in claim 5, wherein, The light extraction section is one or more gaps located inside the light guide plate. The gaps will totally reflect the light propagating in the light guide plate and emit it from the first main surface with the light distribution.

7. The desktop lighting device as claimed in claim 5, wherein, The light extraction section is a light extraction layer disposed on the first main surface. The light extraction layer has one or more gaps that allow total internal reflection of light incident from the light guide plate onto the light extraction layer and exit from the outermost surface of the light extraction layer.

8. The desktop lighting device as claimed in claim 5, wherein, The light extraction section is a light extraction layer disposed on the second main surface. The light extraction layer has one or more gaps that allow total internal reflection of light incident from the light guide plate into the light extraction layer and outward toward the first main surface.

9. The desktop lighting device as claimed in claim 5, wherein, The light extraction part is a prism part or a concave-convex part disposed on the second main surface and directs the light propagating in the light guide plate toward the first main surface.

10. The desktop lighting device as claimed in claim 1 or 2, wherein, The light incident surface of the light guide plate is arranged parallel to the setting surface.

11. The desktop lighting device as claimed in claim 1 or 2, wherein, The light incident surface of the light guide plate is configured perpendicular to the setting surface.

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