JP5535668B2 - Lighting device - Google Patents

Description

  The present invention relates to an illumination device using an organic EL element as a light source.

  An organic EL (Organic Electro-Luminescence) element (hereinafter referred to as “organic EL element”) has a characteristic that the time from voltage application to light emission is very short and excellent in responsiveness, and the responsiveness hardly changes with temperature. Further, the viewing angle is close to 180 degrees. Due to these features, in recent years, organic EL elements have attracted attention as backlight light sources and spatial illumination light sources for display devices.

  FIG. 8 schematically shows the structure of a general organic EL element. The illustrated organic EL element 1 includes a translucent substrate 2 and a light emitting unit 3 formed on one surface of the translucent substrate 2. The light emitting unit 3 includes a transparent electrode 4 formed on one surface of the translucent substrate 2, a light emitting layer 5 made of an organic compound laminated on the transparent electrode 4, and a counter electrode 6 formed on the light emitting layer. It consists of and. In other words, the light emitting layer 5 is sandwiched between the transparent electrode 4 and the counter electrode 6.

  In the organic EL element 1 having the above structure, light emission occurs inside the light emitting layer 5 when voltage is applied to the transparent electrode 4 and the counter electrode 6. Part of the generated light passes through the transparent electrode 4 and enters the translucent substrate 2, and is emitted from the surface of the substrate 2 into the atmosphere. Further, another part of the generated light is reflected by the counter electrode 6, then passes through the transparent electrode 4, enters the translucent substrate 2, and is emitted from the surface of the substrate 2 to the atmosphere. In any case, the light generated inside the light emitting layer 5 is emitted from the surface of the translucent substrate 2 into the atmosphere. In the following description, among the surfaces of the organic EL element, a surface from which light is emitted into the atmosphere is referred to as an “emission surface” and is distinguished from other surfaces. Therefore, in the organic EL element 1 shown in FIG. 8, the surface of the translucent substrate 2 opposite to the surface on which the light emitting portion 3 is formed is the emission surface. In addition, when the light emitting portion is configured by laminating the counter electrode, the light emitting layer, and the transparent electrode in this order on the surface of the translucent substrate, the surface of the transparent electrode becomes the emission surface.

  Here, since the refractive index difference between the emission surface of the organic EL element and the atmosphere is large, most of the light generated in the light emitting layer is totally reflected at the interface between the emission surface and the atmosphere and confined inside the organic EL element. . For example, in the organic EL element 1 shown in FIG. 8, most of the light generated in the light emitting layer 5 is totally reflected at the interface between the surface of the light-transmitting substrate 2 that is the emission surface and the atmosphere and confined inside the element. In a general organic EL element including the organic EL element shown in FIG. 8, the proportion of light emitted in the atmosphere (hereinafter referred to as “extraction efficiency”) out of the light generated in the light emitting layer is about 20% to 30%. It is said that there is.

  Therefore, various techniques intended to improve the extraction efficiency have been proposed. For example, Patent Document 1 describes that a brightness enhancement film is disposed on one surface of a glass substrate corresponding to the emission surface. Further, it is described that the incident surface of the brightness enhancement film facing the glass substrate is in close contact with the glass substrate, and a plurality of convex portions are provided on the surface opposite to the incident surface.

  Patent Document 2 describes that the shape of the protrusion provided on the brightness enhancement film is a truncated cone or a polygonal truncated cone.

  According to Patent Document 1 and Patent Document 2 described above, the light incident on the film in a direction substantially perpendicular to the incident surface of the brightness enhancement film is emitted without being refracted from the upper surface of the convex portion. The light incident on the film tilted with respect to the incident surface is refracted so as to approach the normal direction of the incident surface at the ridge surface of the convex portion, and thus the front luminance is improved and the adjacent convex portion Since light is scattered and reflected between the two, the light utilization efficiency (extraction efficiency) is improved.

JP 2004-184792 A JP 2004-233957 A

  As described above, when an organic EL element is used as a light source, attention has been focused on improving the light extraction efficiency from the emission surface. This is quite natural because the organic EL element is a so-called surface light emitting element. In addition, when the organic EL element is used as a light source for a backlight of a liquid crystal display device or the like, the organic EL element is disposed behind the liquid crystal panel so that light emitted from the emission surface enters the liquid crystal panel, and the emission surface Is generally arranged to face the light incident surface of the liquid crystal panel. In order to improve the luminance of the liquid crystal display device in such a layout, it is necessary and sufficient to improve the light extraction efficiency (utilization efficiency) from the emission surface.

  However, when the organic EL element is used as a light source for spatial illumination, it is not sufficient to improve the light extraction efficiency from the light exit surface of the element. For example, consider a case where an organic EL element is placed on the ceiling of a room. In this case, the organic EL element is attached to the ceiling surface such that the emission surface faces the floor surface. Then, light is emitted mainly from the emission surface of the organic EL element toward the floor surface. For this reason, the illumination of the ceiling surface and the wall surface becomes insufficient, in particular, the illumination of the upper part of the wall surface becomes insufficient, and the entire room is hardly illuminated uniformly.

  An object of the present invention is to illuminate light emitted from an emission surface of an organic EL element from at least two surfaces of a first surface opposite to the emission surface and a second surface different from the first surface. Is to provide a device.

An illuminating device of the present invention is an organic EL element, a plate-shaped light guide, provided on one plate surface of the light guide, and an incident surface on which light emitted from the organic EL element enters. has an exit surface which the light incident from the incident surface is emitted, said exit surface, the second emission surface intersecting the incident surface facing the first light exit surface and said first emission surface of including, and a light guide, both of the first exit surface and said second emission surface of the light guide is characterized in that it is a curved surface.

  According to the present invention, the illumination that causes the light emitted from the emission surface of the organic EL element to be emitted from at least two surfaces of the first surface facing the emission surface and the second surface different from the first surface. An apparatus can be realized.

It is a rear surface side perspective view which shows an example of embodiment of the illuminating device of this invention. It is a front side perspective view which shows an example of embodiment of the illuminating device of this invention. FIG. 3 is a plan view of the light guide shown in FIGS. 1 and 2. FIG. 3 is a plan view of the light guide shown in FIGS. 1 and 2. It is a top view which shows the example which connected multiple illuminating devices shown in FIG. 1, FIG. It is a perspective view which shows an example of a holding means and a connection means. It is a side view which shows the example which suspended the some illuminating device connected as shown in FIG. 5 on the ceiling. It is typical sectional drawing which shows the structure of a general organic EL element.

  Hereinafter, an example of embodiment of the illuminating device of this invention is demonstrated. 1 and 2 are perspective views showing the overall structure of the lighting device 10 according to the present embodiment. The lighting device 10 according to the present embodiment includes an organic EL element 1 as a light source and a light guide 20 that diffuses light emitted from the organic EL element 1. The light guide 20 is made of a translucent material (in this embodiment, a transparent acrylic resin).

  The organic EL element 1 which is a light source of the illumination device 10 according to the present embodiment has the same structure as the organic EL element 1 shown in FIG. Therefore, the same reference numerals as those used in FIG.

  FIG. 1 is a rear perspective view of the lighting device 10, and FIG. 2 is a front perspective view of the lighting device 10. 3 and 4 are plan views of each surface of the light guide 20. As shown in FIGS. 1 and 4, on the back surface of the light guide 20, two accommodating portions 21 that are adjacent to each other in the longitudinal direction and that can accommodate the organic EL element 1 are provided. Each accommodating portion 21 is a recess having a shape substantially similar to the light-transmitting substrate 2 of the organic EL element 1, and the organic EL element 1 is fitted inside each accommodating portion 21. That is, the light guide 20 has a role as a housing for housing the organic EL element 1 as well as a function of diffusing light emitted from the organic EL element 1.

  Each accommodating part 21 of the light guide 20 has a size in which each end surface of the light-transmitting substrate 2 of the organic EL element 1 accommodated in the accommodating part 21 and each inner side surface of the accommodating part 21 face each other with almost no gap. Have Further, the organic EL element 1 is accommodated in the accommodating portion 21 such that the emission surface thereof faces the bottom surface 21 a (FIG. 4) of the accommodating portion 21. The emission surface of the organic EL element 1 is as described above.

  Therefore, the light emitted from the emission surface of the organic EL element 1 enters the light guide 20 from the bottom surface 21 a of the housing portion 21. A part of the light incident on the inside of the light guide 20 is transmitted through the light guide 20 and emitted to the outside. More specifically, light that passes through the inside of the light guide 20 and enters the interface between the surface 20a of the light guide 20 and the atmosphere at an angle less than the critical angle is directly emitted into the atmosphere. On the other hand, light incident on the interface between the surface 20 a of the light guide 20 and the atmosphere at an angle greater than the critical angle is totally reflected at the interface and reenters the light guide 20. The light that re-enters the light guide 20 travels toward the side surface (end surface) 20b of the light guide 20 while repeating total reflection in the light guide 20, and is emitted from the side surface 20b to the atmosphere.

  However, part of the light re-entering the light guide 20 is emitted from the surface 20a of the light guide 20 into the atmosphere in the process of traveling toward the side surface 20b of the light guide 20. That is, as will be described later, since the surface 20a of the light guide 20 is a curved surface (in this embodiment, a free curved surface), the critical angle is not uniform over the entire surface of the light guide 20. Therefore, part of the light traveling toward the side surface 20b of the light guide 20 while repeating total reflection inside the light guide 20 may re-enter the interface at an angle less than the critical angle.

  In any case, the light emitted from the organic EL element 1 enters the atmosphere from the surface 20a (first emission surface) of the light guide 20 and the side surface (second emission surface) 20b intersecting the surface 20a. Emitted. The light guide has four side surfaces 20b, and light is emitted from each side surface 20b.

  Here, as the thickness of the light guide 20 is thinner, the number of total reflections that are repeated until the light re-entered the light guide 20 reaches the side surface 20b of the light guide 20 increases. To increase. Therefore, it is desirable from the viewpoint of improving the light utilization efficiency to make the light guide 20 as thick as possible and reduce the number of total reflections. On the other hand, when the thickness of the light guide 20 increases, the weight of the light guide 20 increases. Accordingly, the thickness of the light guide 20 needs to be determined in consideration of both the light attenuation and the weight of the light guide 20. In this case, if an attempt is made to secure a necessary thickness while keeping the thickness of the light guide 20 constant, the weight of the light guide 20 increases. On the other hand, if an attempt is made to reduce the weight (thinning) of the light guide 20 while keeping the thickness of the light guide 20 constant, the amount of light attenuation increases (a sufficient thickness cannot be ensured).

  Therefore, in the present invention, the surface 20a of the light guide 20 that is the first emission surface and the side surface 20b of the light guide 20 that is the second emission surface are configured by curved surfaces. That is, a part of the light guide 20 was shaved in order to reduce the weight of the light guide 20 as much as possible while ensuring the necessary thickness for the entire light guide.

  Here, since the surface 20a of the light guide 20 is a curved surface, the thickness of the light guide 20 is not uniform. Specifically, the light guide 20 has a thickest part having the maximum thickness and a thinnest part having the minimum thickness, and the smoothest curved surface is formed between the thickest part and the thinnest part. Tied. The thickest part is the distance along the normal direction of the bottom surface of the housing portion between the bottom surface 21a of the housing portion 21 that is the light incident surface and the surface 20a of the light guide 20 that is the first light exit surface. This is the part. The thinnest part is a part where the distance is minimum.

  As a result of various trials and errors based on the above viewpoint, the present inventor found that when the length of the long side of the light guide 20 is a (mm) and the thickness of the thickest part is b (mm), 0.5% The knowledge that it is desirable that the relationship of ≦ a / 4b ≦ 10 is satisfied was obtained.

  Therefore, prototype 1 of the lighting device according to the present invention in which the length of the long side of the light guide is 292 mm, the thickness of the thickest part is 25 mm, and the thickness of the thinnest part is 16 mm, and the long side of the light guide A comparative test was performed on the comparative product 1 having a length of 292 mm and a thickness of 25 mm (uniform). As a result, the test result that Prototype 1 has 1.75 times the light extraction efficiency compared with the comparative product was obtained.

  In addition, prototype 2 of the lighting device according to the present invention in which the length of the long side of the light guide is 292 mm, the thickness of the thickest part is 17 mm, and the thickness of the thinnest part is 8 mm, and the long side of the light guide A comparative test was performed on the comparative product 2 having a length of 292 mm and a thickness of 17 mm (uniform). As a result, the test result that the prototype 2 has a light extraction efficiency 1.65 times that of the comparative product 2 was obtained.

  Furthermore, as a result of various trials and errors including the above comparative tests and simulations, even if the thickness of the thickest part is the same, the thickness difference between the thickest part and the thinnest part is larger (the light guide surface It was also found that the light extraction efficiency is higher when the curvature is smaller.

  Refer to FIG. 1 again. A partition wall 22 is provided between two adjacent accommodating portions 21 of the light guide 20. Further, the central portion 23 of the partition wall 22 is raised higher than both ends thereof to constitute a fixed portion. Specifically, two holes 24 penetrating the partition wall 22 in the thickness direction are formed in the central portion 23 of the partition wall 22, and the holding means can be fixed using the holes 24. The holding means and its fixing method will be described in detail later.

  A plurality of lighting devices 10 according to the present embodiment may be used in a connected manner. 5 and 6 show an example in which nine lighting devices 10 are connected to each other. In the examples shown in these drawings, three lighting devices 10 are vertically arranged to form a first lighting device row 41, and two lighting devices 10 are vertically arranged on both sides of the first lighting device row 41. The second lighting device rows 42 are formed side by side. Further, one lighting device 10 is arranged outside each second lighting device row 42.

  Moreover, the attachment unit 50 as a holding means is being fixed to each fixing | fixed part 23 of the nine illuminating devices 10 arrange | positioned as shown in FIG. Further, the attachment units fixed to each lighting device 10 are connected to each other by a connecting means. In other words, the nine lighting devices 10 are connected and integrated with each other by the connecting means.

  As shown in FIG. 6, the attachment unit 50 is a cylindrical block. On the bottom surface of the mounting unit 50, a recess 51 for receiving the fixing portion 23 of the light guide 20 is formed. The attachment unit 51 is formed with a through hole 52 that penetrates the unit 50 in the radial direction across the recess 51. Further, a cross-shaped groove 53 is formed on the upper surface of the mounting unit 51.

  The mounting unit 50 having the above structure is fixed to the lighting device 10 as follows. That is, the fixing portion 23 of the light guide 20 is fitted into the recess 51 formed on the bottom surface of the mounting unit 50, and the through hole 52 of the mounting unit 50 and the hole 24 of the fixing portion 23 are aligned and communicated. Thereafter, a bolt (not shown) is inserted into the communicating through hole 52 and hole 24, and a nut (not shown) is fitted to the tip of the bolt that passes through the through hole 52 and hole 24.

  Next, the connecting means will be described. In the present embodiment, the steel pipe 60 is used as the connecting means. Specifically, the steel pipe 30 is hung between nine lighting devices 10 arranged as shown in FIG. 5, and the mounted steel pipe 60 is fixed to the predetermined lighting device 10. By fixing to 50, each illuminating device 10 is mutually connected. More specifically, after fitting the steel pipe 30 combined in a predetermined shape into a groove 53 formed on the upper surface of the mounting unit 50, the upper surface of the mounting unit 50 is covered with a lid 54, and the lid 54 is attached. It is fixed to the upper surface with screws. In other words, the steel pipe 30 is sandwiched between the upper surface of the mounting unit 50 and the lid 54.

  Here, as shown in FIG. 5, the attachment unit 50 includes a first attachment unit 50a having a relatively high height and a second attachment unit 50b having a relatively low height. By properly using the mounting units 50a and 50b having different heights, the height of adjacent lighting devices is slightly changed to enhance the design (FIG. 7).

  However, the connecting means is not limited to a steel pipe, and may be an aluminum pipe or other metal pipe, or a resin pipe. Furthermore, a rod made of metal or resin may be used. Further, it is obvious that each lighting device 10 can be detached individually in view of the above-described mounting structure. That is, when a failure occurs in any of the plurality of lighting devices 10 connected to each other, only the lighting device 10 can be replaced.

  Further, as shown in FIG. 7, the lighting device 10 is suspended from the ceiling by fixing the other end of the wire 62 whose one end is fixed to the ceiling 61 to the mounting unit 50 fixed to each lighting device 10. Can do. In this case, it is desirable that the hanging position of the lighting device 10 can be changed by adjusting the length of the wire 62. In addition, it is desirable that each operation such as lighting, extinguishing, and dimming of the lighting device 10 can be remotely operated by a remote controller. In this case, each of the plurality of lighting devices 10 can be remotely operated independently, or can be remotely operated collectively.

DESCRIPTION OF SYMBOLS 1 Organic EL element 10 Illuminating device 20 Light guide 20a Surface (1st output surface)
20b Side surface (second emission surface)
21 accommodating part 23 center part (fixed part)
50 Mounting unit 62 Wire

Claims (6)

An organic EL element;
A plate-like light guide, provided on one plate surface of the light guide body, and the incident surface of the light emitted from the organic EL element is incident, the light incident from the incident surface is emitted And a light guide including a first emission surface facing the incidence surface and a second emission surface intersecting the first emission surface.
Both of the said 1st output surface and the said 2nd output surface of the said light guide are curved surfaces, The illuminating device characterized by the above-mentioned. A housing portion for housing the organic EL element is formed on the one plate surface of the light guide, and a bottom surface of the housing portion facing the organic EL element housed in the housing portion is the incident surface. The lighting device according to claim 1. The lighting device according to claim 2, wherein a plurality of the accommodating portions are provided on the one plate surface of the light guide, and the organic EL element is accommodated in each of the accommodating portions.   The lighting device according to claim 3, wherein a fixing portion capable of fixing a holding unit that holds the lighting device is provided between the accommodating portions adjacent to each other.   When the length of the long side of the light guide is a [mm] and the maximum distance between the entrance surface and the first exit surface in the normal direction of the entrance surface is b [mm], 0.5 The lighting device according to claim 1, wherein a relationship of ≦ a / 4b ≦ 10 is satisfied.   6. A lighting device comprising a plurality of the lighting devices according to claim 1 connected together.

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