JP2009117195A - Planar light source and directional illumination device, directivity variable illumination device, and quasi-indirect illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planer light source that has less light loss and can give a directivity to a target angle and/or direction, and furthermore to provide a planar light source in which the directivity is variable in angle and/or direction. <P>SOLUTION: The planar light source is constructed to include: an electrode; a sheet-formed electroluminescent element having a light-emission material layer; and a directional functional film, on a substrate. The planar light source is characterized in that it emits output light having a directional angle of ≥5° with respect to a normal thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a planar light source that emits directional emitted light and an illumination device using the same.

  Conventionally, an illuminating device in which emitted light has directivity is used to illuminate a specific place. For example, there are lighting devices such as a light that illuminates only the vicinity of a book for reading, an interior lamp that illuminates only a certain part of each seat of an airplane, and an interior light that illuminates only a certain part of a vehicle.

  For these local illuminations, a light bulb illumination device combining a light source of a light bulb or a fluorescent lamp and a concave mirror has been used. However, due to its shape and size, the bulb light source has to be installed by hollowing out the wall or ceiling to be installed or protruding from the wall or ceiling. For this reason, the design and the design were limited.

  On the other hand, planar light sources that have become generally known in recent years are expected to be used for illumination because of their shape and size, such as being thinner than the bulb light source. However, in a planar light source represented by electroluminescence (electroluminescence device), the emitted light is diffused light and emitted light mainly in a direction perpendicular to the surface due to its light emission principle. Therefore, there has been a demand for an illuminating device having emitted light having a directivity angle of 5 ° or more with respect to the normal line of the planar light source. Furthermore, an illuminating device whose angle and direction are variable has been desired.

Regarding the directivity of the emitted light, a light beam introduced into the light guide plate from a linear light source arranged on the side surface of the transparent light guide plate, one surface is a microlens surface, and the other surface is minute There has been disclosed a planar light source that uses a light beam directing sheet having an array of protrusions to make directivity only in the normal direction of the planar light source (see, for example, Patent Document 1).
JP-A-10-39118

  Patent Document 1 uses a light beam directing sheet to direct outgoing light, but has a directivity mainly in a direction perpendicular to the surface. It is difficult to give an angle to the directivity, change the direction of the directivity, and change the directivity in a plurality of directions within the same light source.

  However, when a planar light source is used for local illumination, the directivity direction may be variable so that the illumination position can be freely changed by providing a directivity angle other than the direction perpendicular to the surface. Desired. Moreover, when using as illumination which also serves as decoration, it is preferable that directivity can be changed in a plurality of directions within the same light source.

  Researchers have made research on directivity other than the direction perpendicular to the surface of the planar light source, and tried with a transparent plastic light refracting plate (such as a car tail lamp cover). However, it was concluded that the light loss is large and it is not practical just by overlapping the photorefractive plates of several mm.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a planar light source that has small optical loss and can have directivity in a desired angle or direction. Furthermore, it is an object of the present invention to provide a planar light source whose angle and direction are variable.

The above object is achieved by the following configuration.
1. In a planar light source including an electroluminescent element having an electrode and a luminescent material layer on a substrate, the planar light source emits outgoing light having a directivity angle of 5 ° or more with respect to the normal line. A planar light source characterized by
2. 2. The planar light source according to 1, wherein the electroluminescent element has a sheet shape and includes a directional functional film.
3. The planar light source according to 2, wherein the directional functional film is a bottom-type prism sheet.
4). 4. The planar light source according to 3, wherein the prism of the bottom prism sheet is a truncated pyramid or a truncated cone.
5). The planar light source according to 3 or 4, wherein the prism portion of the bottom-type prism sheet is made of a flexible material, and the directivity angle can be varied by deforming the prism portion.
6). The planar light source according to any one of 2 to 5, wherein the directional functional film is a combination of two or more prism sheets.
7). Any one of 2 to 6, wherein the direction of directivity can be varied by rotating the sheet-like electroluminescent element in a plane direction in a state where the directional functional film is overlapped. The surface light source described in 1.
8). The planar light source according to any one of 1 to 7, wherein the electroluminescent element is an organic electroluminescence element.
9. 9. The planar light source according to 8, wherein the organic electroluminescence element is a phosphorescent light emitting type.
10. The planar light source according to 8 or 9, wherein the organic electroluminescence element is white light-emitting.
11. A directional illumination device using the planar light source according to any one of 11.1 to 10.
12. A directivity variable illumination device using the planar light source according to any one of 12.1 to 10.
13. A pseudo indirect illumination device using the planar light source according to any one of 13.1 to 10.

  By the above, since the directivity can be given to the emitted light of the planar light source, the emitted light can be irradiated at a target angle and direction. In addition, since the angle and direction of the directivity of the emitted light can be made variable, the degree of freedom of the installation location is increased and it can be used for a wide range of applications.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The planar light source of the present invention comprises a sheet-like electroluminescent element and a directional functional film that is a film sheet having a directional function. As a sheet-like light emitting element, light from a light source such as a cold cathode tube or a light emitting diode is incident from an end surface of a light guide plate or a diffusion plate using a transparent resin, and light is emitted from the surface of the light guide plate or the diffusion plate. There are a method, a method of emitting light from electroluminescence (EL) which is an electroluminescent element, and the like. The present invention uses the electroluminescent element as a sheet-like light emitting element.

  Electroluminescence is preferable from the viewpoint of thinness of the light emitting element and power saving, and among them, an organic EL element whose substrate is made of a flexible plastic film is most preferable.

  FIG. 1 is a configuration diagram of a planar light source according to the present invention. The planar light source 1 includes an electroluminescent element (hereinafter also abbreviated as a light emitting element) 10 and a directional functional film 20. In the present embodiment, an organic EL element is used as the light emitting element 10.

  In the present invention, the directivity is defined as the directivity angle by measuring the luminance from 0 ° to ± 60 ° in increments of 5 ° with respect to the normal of the planar light source, and the angle of the maximum luminance. For the measurement of luminance, a spectral radiance meter (for example, CS-1000 (manufactured by Konica Minolta Sensing)) or the like can be used.

  The planar light source of the present invention emits outgoing light having a directivity of 5 ° or more with respect to the normal line, and the angle is preferably 10 ° or more, particularly preferably 20 ° or more and 45 °. It is as follows. Further, the luminance distribution is preferably asymmetrical in the plane including the normal line.

  As the directional functional film 20, a transparent prism sheet having a fine concavo-convex structure on the surface as shown in JP-A No. 2004-127746 and JP-A No. 2005-55481 is formed at 5 ° with respect to the normal line. Although it is preferable to process the emitted light having the above directivity angle, it is preferable to use a liquid crystal film sheet, a transparent film sheet in which fine light-reflecting substances are arranged in a certain direction, and a micro that can be driven individually. An element in which mirrors are arranged can also be used.

  Particularly, in the present invention, the most effective means for achieving such a directivity angle is a prism sheet (in the present invention, as shown in FIGS. 1 to 9 of JP-A-2007-180001). , Which is composed of a bottom-type prism sheet) in which the center of the convex portion is inclined with respect to the normal so as to emit outgoing light having a directivity angle of 5 ° or more with respect to the normal It is.

  The bottom-type prism sheet is characterized in that convex portions formed on the surface of the base material are arranged on the light emission surface side of the light emitting element. The pitch of the convex portions is 10 to 500 μm, preferably 20 to 200 μm, and the height of the convex portions is 3 to 500 μm, preferably 10 to 200 μm.

  2 and 6 are views showing examples of the bottom type prism sheet. 2A and 6 are views seen from the side, and FIG. 2B is a view of the bottom-type prism sheet 21 shown in FIG. The convex portions 211 and 511 of the bottom-type prism sheets 21 and 51 are arranged on the light emitting surface side of the light emitting element 10, and the side portions 212, 213, 512, and 513 of the convex portions 211 and 511 have different combinations. The light directing angle can be adjusted by tilting the In the present embodiment, the convex portions 211 and 511 have an oblique truncated cone shape, but the present invention is not limited to this, and an oblique truncated cone shape may be used. In the present invention, the convex portion is most preferably an oblique truncated cone shape.

  As another effective example for achieving the directivity of the present invention, a configuration composed of a combination of a light emitting element and two or more prism sheets can be mentioned. When using the structure which consists of this combination of prism sheets, it is preferable that the prism sheet installed in the outermost part has an asymmetric structure in which the convex direction is angled with respect to the normal line.

  3 and 4 show examples in which prism sheets 31 and 41 having a fine uneven structure on the surface and another type of prism sheets 32 and 42 are combined. The directivity of the planar light source 1 is not limited to directivity in one direction, and may have directivity in two or more directions depending on the purpose and application of use. For example, FIG. 3 is an example having directivity in one direction, and FIG. 4 is an example having directivity in two directions. FIG. 5A shows the light distribution characteristic distribution of FIG. 3 and FIG. 5B shows the light distribution characteristic distribution of the example of FIG.

  In addition, the directivity can be made to function like a spotlight by collecting emitted light. FIG. 6 shows an example of condensing outgoing light. In this case, it is achieved by making the inclination of the side surface portion 512 of the convex portion 511 of the prism sheet 51 different depending on the position, exhibiting a function like a Fresnel lens, and designing at an arbitrary directivity angle.

  The planar light source 1 may be used in a state in which the directivity angle and direction are fixed, but it is also a preferable form that the directivity angle and direction of the installed planar light source 1 are variable by the user. The variable directivity can be achieved by movably installing the entire planar light source 1 having directivity so that the directivity can be varied. Further, it can also be achieved by configuring the bottom-type prism sheets 21 and 51 to be variable with respect to the light emitting element 10 or configuring the prism sheets 31 and 41 to be variable. (Hereinafter, the bottom-type prism sheets 21 and 51 and the prism sheets 31 and 41 are collectively referred to as a prism sheet). Such change of each prism sheet is possible by rotating each prism sheet with respect to the light emitting element 10 on the same plane. It is also possible to form at least the convex part of each prism sheet with a flexible material and to incline and deform it by physical force or electrical action.

  The prism sheet as described above can be made variable by arranging the liquid crystal film sheet, a transparent film sheet in which fine light-reflective substances are arranged in a certain direction, and micro-mirrors that can be individually driven. The present invention can also be applied to other elements.

In the present invention, the electroluminescent element is preferably an organic EL element.
An organic EL element has a structure in which a light emitting layer containing a light emitting compound (light emitting material) is sandwiched between a cathode and an anode, and excitons are formed by injecting electrons and holes into the light emitting layer and recombining them. It is an element that emits light by utilizing light emission (fluorescence / phosphorescence) when the excitons are deactivated. Although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / light emitting layer / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) Anode / anode buffer layer / hole transport layer / light emitting layer / hole Blocking layer / electron transport layer / cathode buffer layer / cathode Here, the concept of a hole injection layer and an electron blocking layer is also included in the hole transport layer.

  The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.

  In the present invention, the organic EL element is preferably white luminescent. In the present invention, white means that the chromaticity of the CIE 1931 color system is in the region of x = 0.33 ± 0.07 and y = 0.33 ± 0.07.

  The light emitting layer preferably contains at least two kinds of light emitting materials having different emission colors. It is preferable that the maximum light emission peak wavelength of the light emitting material contained in the light emitting layer is at least two selected from four categories of 430 to 480 nm, 500 to 540 nm, 520 to 560 nm, and 580 to 640 nm. The light emitting layer may be a single layer or may form a light emitting layer unit composed of a plurality of light emitting layers. When there are a plurality of light emitting layers, it is preferable to have a non-light emitting intermediate layer between each light emitting layer. A mode in which the light-emitting layer is a single layer and contains a plurality of, preferably three or more types of light-emitting materials is particularly preferable because it can reproduce a preferable white color and has high white color stability over time.

  The total thickness of the light emitting layers in the present invention is preferably in the range of 1 to 100 nm, and more preferably 10 to 50 nm because a lower driving voltage can be obtained. In addition, the sum total of the film thickness of the light emitting layer said by this invention is a film thickness also including this intermediate | middle layer, when a nonluminous intermediate | middle layer exists between light emitting layers.

  The thickness of each light emitting layer is preferably adjusted to a range of 1 to 50 nm, more preferably adjusted to a range of 1 to 20 nm. There is no particular limitation on the relationship between the film thicknesses of the blue, green and red light emitting layers.

  The present invention can also be applied to a device in which a light emitting element can adjust its emission color as disclosed in US Pat. Nos. 6,661,029, 6841949, 6312836, 6287712, 6210814, and 5773130.

  For the production of the light emitting layer, a light emitting material or a host compound, which will be described later, is formed by forming a film by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, or the like. it can.

  In the present invention, a plurality of light emitting materials may be mixed in each light emitting layer, and a phosphorescent light emitting material and a fluorescent light emitting material may be mixed and used in the same light emitting layer. In the present invention, the structure of the light-emitting layer preferably contains a host compound and a light-emitting material (also referred to as a light-emitting dopant compound) and emits light from the light-emitting material.

  As a host compound contained in the light emitting layer of the organic EL device of the present invention, a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) of less than 0.1 is preferable. More preferably, the phosphorescence quantum yield is less than 0.01. Moreover, it is preferable that the volume ratio in the layer is 50% or more among the compounds contained in a light emitting layer. As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of luminescent material mentioned later, and can thereby obtain arbitrary luminescent colors.

  The host compound used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (evaporation polymerizable light emitting host). )But it is good.

  As the known host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable. Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

  As the light-emitting material according to the present invention, a phosphorescent light-emitting material (also referred to as a phosphorescent compound or a phosphorescent compound) is preferably used.

  The phosphorescent material according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.). Although defined as being a compound of 01 or more, the preferred phosphorescence quantum yield is 0.1 or more.

  The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence emitting material according to the present invention can achieve the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

  The phosphorescent light emitting material can be appropriately selected from known materials used for the light emitting layer of the organic EL element. The phosphorescent material according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex compound). Rare earth complexes, most preferably iridium compounds.

  The compound used as the phosphorescent material is, for example, Inorg. Chem. 40, 1704-1711, and the like.

The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be. An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).
The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

  The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.

  The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

  The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.

  On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The film thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

  The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers. The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Particularly preferred as a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) according to the organic EL element of the present invention is a transparent and flexible resin film.

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability measured by a method in accordance with JIS K 7129-1992 (40 ° C., 90% RH) Is preferably a barrier film of 0.01 g / m ² · day · atm or less, and further has an oxygen permeability (20 ° C., 100% RH) of 10 measured by a method according to JIS K 7126-1992. ⁻³ g / m ² / day or less and a water vapor transmission rate of 10 ⁻³ g / m ² / day or less are preferable, and both the water vapor transmission rate and the oxygen transmission rate are 10 ^−5. More preferably, it is below g / m < ² > / day.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

By applying a white light emitting organic EL element containing a phosphorescent light emitting material to the present invention, a planar light source having a low driving voltage current, high luminous efficiency, excellent spectral emission characteristics, and a long lifetime can be provided. . Further, when combined with a directional functional film, the spectral light emission characteristics are excellent, and therefore an excellent planar light source with little change in white color tone can be provided even if the directivity is angled.
<Example>
1) For automotive interior lighting FIGS. 7 and 8 are examples in which the planar light source 1 is used for automotive interior lighting. FIG. 7 shows an example in which the planar light source 1 is attached to the inner side of the center pillar, which is a support column located substantially at the center of the side of the automobile. FIG. 8 is an example in which the planar light source 1 is attached inside the door. The planar light source 1 that emits directional emission light according to the present invention can be applied to an automobile interior illumination lamp by utilizing its thinness. Since almost no space for installing a light source is required, it can be installed by installing it in any place in the room. Moreover, it can be installed over a wide area in an arbitrary shape where lighting is required. Due to the directivity, the rear seat can be effectively illuminated at night with minimal impact on the driver.
2) For Local Illumination FIGS. 9 and 10 are examples in which the planar light source 1 is used for local illumination using directivity. FIG. 9 shows an example in which the planar light source 1 is attached to a desk, ceiling or the like as lighting for reading or work, for example. FIGS. 10A and 10B are examples used as lighting for personal reading of vehicles, aircraft, ships, etc., FIG. 10A shows a rectangular planar light source 1, and FIG. 10B shows a circular planar light source. 1 is an example using. By changing the direction of directivity, the usability is greatly improved. The illumination position can be changed by moving the aforementioned prism sheet. The directivity of the prism sheet may be manually changed. For example, in the case of FIG. 10A, the cursor lever type shown in FIG. 10C or the touch panel type shown in FIG. It can also be automatically variable in the directions of arrows X and Y. In the case of FIG. 10B, the prism sheet may be automatically rotated using a cursor lever method or the like as shown in FIG.
3) Decorative Wall Surface As shown in FIG. 11, the planar light source 1 can be applied to a decorative wall surface using its thinness and directivity. Since the direction of light can be designed by arbitrarily designing the pattern of the directional functional film, it is possible to form an interesting decorative wall surface in which the pattern changes depending on the position of the observer. By changing only the directional functional films (20a, 20b), it can be easily changed to a decorative wall surface with a different pattern, and is optimal for changing the design of a store or the like.
4) Pseudo indirect illumination FIG. 12 is a conceptual diagram of indirect illumination. Indirect illumination is to irradiate an object with light from a light source and use the reflected light. Conventionally, as shown in FIG. 12B, it is necessary to hide the light source itself. , Will require a lot of installation space.

  However, as shown in FIG. 12A, the planar light source 1 can be used as pseudo-indirect illumination without using a large installation space by utilizing its thinness and directivity. By designing the pattern of the directional functional film so that the directivity of the planar light source 1 that emits directional emitted light continuously changes, even if the light emitting element emits light uniformly, it depends on the position of the observer. Since it looks like a gradation is formed, you can feel as if it were a wall illuminated by indirect lighting.

It is a block diagram of the planar light source which concerns on this invention. It is a figure which shows the example of a bottom type prism sheet. It is a figure which shows the example which combined the prism sheet and the condensing sheet. It is a figure which shows the example which combined the prism sheet and the condensing sheet. It is a figure which shows the light distribution characteristic distribution of the example of FIG.3 and FIG.4. It is a figure which shows the example of a bottom type prism sheet. It is a figure which shows the example which used the planar light source for the indoor illumination of a motor vehicle. It is a figure which shows the example which used the planar light source for the indoor illumination of a motor vehicle. It is a figure which shows the example which used the planar light source for local illumination. It is a figure which shows the example which used the planar light source for local illumination. It is a figure which shows the example which used the planar light source for the decoration wall surface. It is a figure which shows the example which used the planar light source for pseudo-indirect illumination.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planar light source 10 Light emitting element 20 Directional function film 21, 51 Bottom type prism sheet 31, 41 Prism sheet 32, 42 Light collecting sheet

Claims (13)

In a planar light source including an electroluminescent element having an electrode and a luminescent material layer on a substrate, the planar light source emits outgoing light having a directivity angle of 5 ° or more with respect to the normal line. A planar light source characterized by The planar light source according to claim 1, wherein the electroluminescent element has a sheet shape and includes a directional functional film. The planar light source according to claim 2, wherein the directional functional film is a bottom-type prism sheet. 4. The planar light source according to claim 3, wherein the prism of the bottom prism sheet is a truncated pyramid or a truncated cone. 5. The planar light source according to claim 3, wherein the prism portion of the bottom-type prism sheet is made of a flexible material, and the directivity angle can be varied by deforming the prism portion. The planar light source according to any one of claims 2 to 5, wherein the directional functional film is a combination of two or more prism sheets. 7. The directivity direction can be varied by rotating the sheet-like electroluminescent element in a plane direction with the directional functional film being superposed. 2. A planar light source according to item 1. The planar light source according to any one of claims 1 to 7, wherein the electroluminescent element is an organic electroluminescence element. The planar light source according to claim 8, wherein the organic electroluminescence element is a phosphorescent light emitting type. The planar light source according to claim 8, wherein the organic electroluminescence element is white luminescent. A directional illumination device using the planar light source according to any one of claims 1 to 10. A directional variable illumination device using the planar light source according to any one of claims 1 to 10. A pseudo-indirect illumination device using the planar light source according to any one of claims 1 to 10.

Images