JPWO2009047891A1 - Surface light source element array and image display device - Google Patents

Abstract

Provided is a surface light source element array capable of emitting light of uniform brightness in a plane without producing a lamp image even when the thickness between a target surface and a light emitting element arrangement surface is thin. In the surface light source element array, a plurality of surface light source elements 5 are arranged, and the surface light source element includes a light guide 1, at least one light emitting element 2 disposed inside the light guide, 50% of the light emitted from the light emitting element 2, including a light control member 4 disposed on the bottom surface of the light guide 1 and a reflection member 3 disposed on the side surface of the light guide. The above is incident at an angle of total reflection inside the light guide 1, the reflection member 3 is set so as to return light to the inside of the light guide 1 by reflection, and the light control member 4 It is set so that the traveling direction is changed and emitted to the outside of the light guide.

Description

Related applications

  This application claims the priority of Japanese Patent Application No. 2007-265397 filed on Oct. 11, 2007 in Japan, the entirety of which is cited as a part of this application by reference.

  The present invention relates to a surface light source and a surface light source element array, and more particularly to a thin and uniform surface light source using light from a point light source. The present invention further relates to a liquid crystal display device using the surface light source element array.

  In recent years, liquid crystal televisions have become widespread as flat-screen televisions. Since a liquid crystal television is not a self-luminous type, it is necessary to irradiate light from the back surface, and a backlight (surface light source device) is necessary. A backlight of a liquid crystal television is required to have a light emitting surface with a large area and to have uniform luminance over the front surface.

The backlight for the image display device guides the light of the light source arranged on the side surface of the light guide plate in the front direction with the light guide plate, and makes the light source uniform on the diffusion sheet and the light source on the back side of the illumination surface, There is a direct method in which light is made uniform with a diffusion sheet.
The direct type has a tendency to increase in thickness because it has a light source on the back of the device. For this reason, in fields where thinness is required such as mobile phones, mobile PCs, car navigation systems, etc. The edge light method that can be realized is the mainstream.

  On the other hand, in recent years, there has been an increasing demand for larger displays and higher brightness mainly in televisions and personal computer monitors. In particular, with the increase in the size of the display, in the edge light system, the ratio of the length of the peripheral portion where the light source can be arranged to the display area decreases, and the amount of light is insufficient, so that sufficient luminance cannot be obtained. Further, the edge light system has a problem that the weight of the light guide plate increases as the display becomes larger. As described above, in the edge light system, it has become difficult to meet market demands such as an increase in display size and brightness in recent years.

  Therefore, in large display applications, a direct system using a plurality of light sources is adopted. In this method, the ratio of the luminous flux emitted from the light source is high, and the number of light sources can be increased freely. That is, since the amount of light can be increased freely, the required high brightness can be easily obtained.

  However, the direct method needs to solve unique problems such as elimination of lamp image, thinning, and energy saving. In particular, the lamp image appears as brightness unevenness much more remarkable than the edge light system. For this reason, it is difficult to eliminate the lamp image by means conventionally used in the edge light system, that is, means such as a diffusion film in which a diffusion material is applied to the film surface.

  Therefore, a diffusion sheet containing a diffusion material is widely used. In this method, in order to obtain good diffusibility and light utilization efficiency, inorganic particles and crosslinked organic fine particles are added to the base resin such as methacrylic resin, polycarbonate resin, styrene resin, vinyl chloride resin, etc. And a method of preparing a light diffusion sheet.

  Until now, backlights using cold cathode tubes, which have high light utilization efficiency as a light source and are low cost, have been the mainstream. The lamp image of the cold cathode tube can be diffused by a diffusion sheet to form a uniform surface light source. In order to make a conventional illuminating device a uniform surface light source, it has been possible to realize a surface light source by providing an interval of about 30 mm between the light source and the diffusion sheet.

  On the other hand, in recent years, it has been necessary to further reduce power consumption and improve color reproducibility of displays, so that backlight light sources using red, green, and blue LEDs instead of cold cathode tubes have been developed. Yes.

  However, in this backlight, in order to mix three colors of light and to make the light intensity and color mixture uniform, a space between the LED arrangement surface and the prism sheet is required to be more than a certain level. There was a drawback that the thickness of the backlight was increased.

  If the target surface is brought close to the LEDs and the light intensity on the target surface is made uniform, it is necessary to increase the number of LEDs to increase the arrangement density. Therefore, in this case, there are problems that a large number of LEDs are required and power consumption is increased.

  In Patent Document 1, a plurality of light emitting diodes disposed on a substrate, a light guide plate provided on the light emitting side of the light emitting diode, and each light emitting diode are opposed to each other between the light emitting diode and the light guide plate. And an optical element provided therewith. In this backlight device, the light emitted from the LED chips of the respective colors of the light emitting diodes is diffused according to the alignment pattern of the light beam by the optical element, and the light emitted from the optical element is spread over the entire light guide plate.

  However, in this backlight device, each light emitting element and the optical element are arranged in a pair, and each pair of optical elements diffuses the light from the light emitting element. It is impossible to uniformly mix the light of each color before entering the optical element. For this reason, it is necessary to mix light of each color uniformly in the space between the optical element and the light guide plate, and for that purpose, it is necessary to take a sufficient optical path length in the space for uniformization. As a result, the thickness of the space between the optical element and the light guide plate becomes considerably large, so that the thickness cannot be reduced and the weight of the light guide plate increases.

  As described above, conventional backlights using red, green, and blue LEDs are superior in terms of color reproducibility, but backlights using three colors of LEDs are uniform. Therefore, it is necessary to sacrifice one of the thickness, uniformity, and power consumption, the thickness is thin, the light intensity distribution and the color mixture are uniform, and the low power consumption back. The light could not be made.

  In order to solve this problem, in Patent Document 2, a reflective member is provided on the back surface of the transparent mold portion, and light emitting elements of red, green, and blue emission colors are sealed at the center of the mold portion, In the vicinity of the center of the reflecting member, there is formed a reflective region that is inclined obliquely toward the back as it goes to the outer periphery, and a light emitting light source that is provided with an inclined inclined total reflection region on the light exit surface of the mold part Is disclosed. The light emitted from the light emitting elements of the red, green, and blue emission colors is totally reflected in the inclined total reflection region, further totally reflected in the direct emission region, and guided to the outer peripheral end portion of the reflection member. The light is emitted forward by reflection at the outer peripheral edge. In Patent Document 2, it is described that a light-emitting light source using a light-emitting element with uniform light intensity and color on the irradiated surface, thin thickness, and low power consumption can be obtained. However, in this light emitting light source, the light emitting elements of all colors are solidified at the center, so that it is difficult not only to obtain uniform brightness in the plane, but also from the light emitting elements provided in the center. In order to sufficiently diffuse light, the mold part must be thickened. Therefore, even if it is said to be thin, there is a drawback that it is equivalent to or thicker than the current mainstream cold cathode tube type.

Japanese Patent No. 2003-297127 JP 2006-148036 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a surface light source element array capable of emitting light of uniform brightness in a plane without producing a lamp image even when the thickness between the target surface and the light emitting element arrangement surface is thin. There is to do.

  Another object of the present invention is to provide a surface light source element array that does not require sacrifice of thickness, uniformity, or power consumption, has a uniform light intensity distribution and color mixture, and has low power consumption. Is to provide.

  Still another object of the present invention is to provide a surface light source element array capable of controlling not only the surface emitting area but also the surface light source elements independently to control brightness and color for each area. It is to provide.

  Another object of the present invention is to provide an illumination device that uniformly emits light and a high-quality image display device.

In order to solve the above problems, the present inventors have found the following points and completed the present invention.
First, in the surface light source element array, in each surface light source element constituting the array, the light emitting element that emits light toward the inside of the light guide is arranged not on the side surface of the light guide but on the inside. A large part of the light emitted from the element can be incident at an angle that totally reflects the inside of the light guide, and a light guide is provided by disposing a reflecting member on at least one of the side surface or the bottom surface of the light guide. Light can be confined inside the body. And the light confined inside the light guide in this way is uniformly mixed inside the light guide, while the light control member existing on the lower side or the upper side of the light guide or both, The traveling direction is changed, and the light is emitted as uniform light from the upper surface of the light guide. As a result, it has been found that uniform light is emitted from each of the surface light source elements, which are each constituent unit of the surface light source element array, and that extremely uniform light can be emitted from the entire surface of the surface light source element array.

  Second, in the above surface light source element, the light emitting element is not necessarily arranged at the center of the light guide. For example, a plurality of light emitting elements are arranged by arranging a plurality of light emitting elements at appropriate positions. However, it has been found that uniform light emission is performed for each light emitting element. Further, when red, green, and blue light emitting elements are used, it is possible to uniformly mix the respective colors inside the surface light source element, and if red, green, and blue light emitting elements are used, a surface having high definition. I also found it to be a light source.

  The present invention based on the above examination results is a surface light source element array in which a plurality of surface light source elements are arranged, and the surface light source elements are disposed inside the light guide and the light guide. And at least one light emitting element, a light control member disposed on at least one of an upper surface or a bottom surface of the light guide, and a reflecting member disposed on at least one of the side surface or the bottom surface of the light guide. And 70% or more of the light emitted from the light emitting element is incident at an angle at which the light is totally reflected inside the light guide, and the reflecting member is set to return the light to the inside of the light guide by reflection, and The light control member is set to change the traveling direction of the reflected light and to emit the reflected light to the outside of the light guide.

  In the surface light source element, when a diffusing member having a diffusing performance with a haze value of 90% is installed 5 mm above the main surface of the surface light source element, and one of the light emitting elements inside the surface light source element is turned on. Of the luminance of the surface light source element, the area where the decrease in luminance is within 10% compared to the brightest luminance may be 60% or more of the main surface of the surface light source element.

  The surface light source element may include a plurality of point light sources having different colored light as light emitting elements, and may include light emitting diodes of three colors of red, blue, and green as light emitting elements. The distance between the light emitting elements in the surface light source element may be about 2 to 5 times the diameter of the light emitting element.

  The present invention includes an image display device in which a transmissive display element is provided on the light emitting side of the surface light source element array. In the image display device, at least one optical member may be provided between the surface light source element array and the transmissive display element.

  In the present invention, the light emitting element is present inside the light guide, and the light guide is surrounded by the reflecting member, so that not only the light use efficiency is improved, but also the light is reflected inside the light guide to be uniform. Can disperse the light, and a uniform surface light source can be obtained. Furthermore, since reflection inside the light guide can be used as an optical path length for mixing light, it is possible to realize a thin surface light source element that has been difficult in the past.

  Furthermore, by changing the shape of the light guide part, it is possible not only to obtain a surface light source light emitting element having an arbitrary shape, but also by combining the surface light source elements, a surface light source element array that performs uniform surface light emission has an arbitrary size. It can be obtained in a sheath shape.

  Since the surface light source element performs uniform surface light emission independently, in the surface light source element array in which a plurality of such surface light source elements are arranged, it is possible to enlarge the area for surface light emission and each surface light source element. It is possible to control brightness and color for each area by independently controlling.

  When the light-emitting element described above is a point light source with different colored light, it is possible to emit not only a single color or white color but also any color by combining the light sources. This makes it possible to improve the color purity important for a display or the like and develop a specific color.

  Furthermore, by providing a transmissive display element in the surface light source element array of the present invention, not only can a large screen and a thin film be achieved, but also an image display device with high definition, high contrast and low power consumption can be obtained.

  Further, by providing an optical member between the surface light source element and the transmissive display element, it is possible to further improve the light utilization efficiency, adjust the viewing angle characteristics, and adjust the in-plane luminance distribution.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the examples and figures are for illustration and description only and should not be used to define the scope of the invention. The scope of the invention is defined by the appended claims. The drawings are not necessarily drawn to scale, but are exaggerated in illustrating the principles of the invention. In the accompanying drawings, the same part number in the plurality of drawings indicates the same part.
It is the conceptual diagram which expanded a part of surface light source element array of the 1st Embodiment of this invention. It is a conceptual diagram which shows the surface light source element used in the 1st Embodiment of this invention. It is a conceptual diagram which shows the cross-sectional structure of the surface light source element used by the 1st Embodiment of this invention. It is a conceptual diagram which shows the cross-sectional structure of the surface light source element used by the 2nd Embodiment of this invention. (A) is a top view of the surface light source element used in Example 1 of this invention, (b) is the sectional drawing. It is a top view of the light control member used in Example 1 of the present invention. (A) is a top view of the surface light source element used in Example 2 of this invention, (b) is the sectional drawing. (A) is a top view of the surface light source element used in Example 3 of this invention, (b) is the sectional drawing.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is a view for explaining an embodiment of the surface light source element array of the present invention, showing a top view of the surface light source element array, and FIG. 2 showing a top view of the surface light source element. FIG. 3 is a cross-sectional view orthogonal to the main surface of one surface light source element along the line III-III in FIG. As shown in FIG. 1, the surface light source element array is formed by two-dimensionally arranging a plurality of surface light source elements 5, and the square surface light source elements 5 are arranged in contact with each other. In addition, since the surface light source element 5 has the light emitting element 2 disposed inside the transparent light guide 1, the light emitting element 2 can be visually recognized through the light guide 1, and specifically, as shown in FIG. The light emitting element 2 includes a red light emitting element 2a, a blue light emitting element 2b, and two green light emitting elements 2c.

  Further, as shown in FIG. 3, each surface light source element 5 includes the light guide 1, the reflecting member 3 disposed on the entire circumference and the bottom surface of the light guide 1, and the bottom surface of the light guide 1. And a light emitting element 2 disposed in a cavity with a part cut away. Further, a liquid crystal panel 6 (not shown) is supported by a casing above the surface light source element in FIG. 3, that is, on the light emitting surface side, thereby forming an image display device. The light emission angle characteristic of each LED is between −30 ° and 45 ° when the direction in which the reflecting member is formed is − when the direction parallel to the main surface of the light guide 1 is 0 degree and the direction where the reflecting member is not formed is +. Light goes on. As shown in FIG. 3, the light emitted from the light emitting element 2 travels while being totally reflected in the light guide 1, and when the light enters the minute protrusions of the light control member 4, the light deviates from the condition of total reflection. Is generated, and light is emitted from the upper surface of the light guide 1.

(Light guide)
The light guide 1 is preferably transparent to the wavelength of visible light. If so-called transparent, the material is an organic material (for example, a thermoplastic resin, a thermosetting resin, a photocurable resin, etc.), an inorganic material. Any of (for example, glass etc.) may be sufficient. Examples of organic materials include (meth) acrylic resins, (meth) acrylic-styrene copolymer resins, styrene resins, aromatic vinyl resins, olefin resins, ethylene-vinyl acetate copolymer resins, vinyl chloride. Resin, vinyl ester resin, polycarbonate resin, fluororesin, urethane resin, silicone resin, amide resin, imide resin, polyester resin, epoxy resin, phenol resin, urea resin, melamine resin and the like. Of these, (meth) acrylic resin, polycarbonate resin, glass and the like are preferable.

  From the viewpoint of reducing loss when light having a visible light wavelength propagates, the refractive index of such a light guide is preferably, for example, about 1.48 to 1.62, and more preferably 1.50 to 1.2. About 60.

  In order to arrange two-dimensionally as a surface light source element array, it is preferable that the light guide has a form that can be combined in a tile shape. For example, forms that can be combined in a tile shape include polygonal shapes such as a triangle, a quadrilateral, a pentagon, and a hexagon. Although different shapes can be used in combination, a light guide having the same shape is often used from the viewpoint of manufacturing.

  Moreover, in order to enclose a light emitting element in the inside of a light guide, a part of bottom face is notched and a hollow part is formed. Such a hollow portion may be directly molded using a known or conventional method such as injection molding, compression molding or transfer molding, or a molded body having a predetermined shape is cut using a lathe or the like. Also good.

(Reflective member)
The reflective member 3 is disposed on at least one of the side surface side or the bottom surface side with respect to the main surface of the light guide 1. The reflecting member 3 allows light to be emitted in a certain direction only from the upper surface with respect to the main surface of the light guide, that is, only in a certain section. The reflecting member 3 may be formed of the same material on the side surface side and the bottom surface side, or may be formed of different materials.

  For example, the reflective member 3a on the side surface side is preferably made of a material that regularly reflects so that light is not emitted from a portion where the light guide 1 and the reflective member 3 approach each other. For example, as such a material, a metal sheet may be simply used, or a resin molded product formed from an olefin resin or the like may be used by coating or vapor-depositing a metal or the like. When a reflecting member that reflects on both sides is used on the side surface side, the arrangement of the reflecting member may be omitted on the side surface side of the surface light source element that faces the reflecting member.

  On the other hand, the reflecting member 3b on the bottom surface side of the light guide 1 may be made of a material having either regular reflection or diffuse reflection. As the material for regular reflection, the same member as the reflection member 3a on the side surface side is raised, and as the material for diffuse reflection, a white resin molded product with high diffusibility may be used as the reflection member.

  Such a reflection member 3 may be appropriately disposed with respect to the light guide 1 according to the material. For example, the reflection member 3 may be attached to the light guide 1 by using an adhesive, or guided by vapor deposition. It may be formed directly on the body 1. Moreover, you may arrange | position through an air layer.

(Light emitting element)
The light emitting element 2 is not particularly limited as long as 70% or more of the light emitted from the light emitting element is incident at an angle at which the light is totally reflected inside the light guide. For example, as the light emitting element having such a light emitting property, A side emission type light emitting diode (LED) is exemplified.
Even if the light emitting diode is not a side emission type light emitting diode, a light reflecting member, a diffusing member, an absorbing member, etc. are formed on the top of the light emitting element, so that 70% or more of the light emitted from the light emitting element is entirely within the light guide. It can be set as the structure which reflects.

  From the viewpoint of obtaining uniform surface light emission, the light emitting element 2 is preferably a light source that does not emit light in a direction perpendicular to the main surface of the light guide 1. Of the light emitted from the light emitting element, the light guide It is necessary that the light incident at an angle of total reflection inside the light source is 70% or more, preferably 7.5% or more, and more preferably 80% or more.

  Only one light emitting element may be provided for one light guide, or a plurality of (for example, 2 to 4, preferably 3 to 4) light emitting elements may be provided. From the viewpoint of enhancing color reproducibility, the surface light source element preferably has a plurality of point light sources having different colored light as light emitting elements. Further, from the viewpoint of low power consumption, it is preferable to use an LED as a light emitting element, and it is preferable to provide at least one LED of three colors of red, blue, and green in one light guide.

  The position of the light emitting element 2 in the light guide 1 is preferably not too close to the end of the light guide from the viewpoint of obtaining uniform light emission within the surface. For example, the light emitting element is preferably separated from the side surface of the closest light guide by 1/4 or more of the diameter of the light emitting element, more preferably 1/3 or more of the diameter, and further preferably 1/2 or more of the diameter. Particularly preferably, the distance may be about 1/1 to 3/2 of the diameter.

  On the other hand, when a plurality of light emitting elements are provided inside the light guide, it is preferable that the arrangement positions of the light emitting elements are not too close from the viewpoint of uniformly mixing the light emitted from the light emitting elements by reflection. For example, the distance between the light emitting elements (the distance connecting the center points of the light emitting elements) is preferably about 2 to 5 times the diameter of the light emitting elements, more preferably about 2.5 to 4.5 times, and even more preferably. About 3 to 4 times.

(Light control member)
The light control member provided in the upper part, the lower part, or both of the light guide 1 changes the traveling direction of light that has been repeatedly totally reflected inside the light guide 1. Then, light having an angle at which the inside of the light guide 1 cannot be totally reflected is generated, and the light is emitted from the upper surface of the light guide 1.

  The light control member is not particularly limited as long as it has a property of changing the traveling direction of light totally reflected in the light guide and emitting light from the light guide, and a known or public light control member can be used. . For example, the light control member may be a microprojection member disposed on the bottom surface of the light guide, and the plurality of convex portions have their tops on the light exit surface (ie, top surface) side of the light guide. The connecting convex member arranged in a row may be used. Moreover, the scattering reflection member etc. which were formed by printing a scattering reflective ink on the bottom face of a light guide may be sufficient. These light control members can be used alone or in combination.

  For example, when a microprojection member is used as the light control member, as shown in FIG. 3, as the light control member 4, a plurality of microprojections that project at regular intervals are disposed on the bottom surface of the light guide 1. Yes. The shape, size, density, and the like of the protrusions are not particularly limited as long as the traveling direction of the total reflected light can be changed from the reflection angle. For example, the protrusions may have a spherical shape or an elliptical spherical shape. And shapes such as a polygonal pyramid shape (for example, a triangular pyramid shape, a quadrangular pyramid shape, etc.) and an indefinite shape. Moreover, as a magnitude | size of the base part of a projection part, about 50-3000 micrometers is preferable and about 100-2000 micrometers is more preferable. Further, the height of the protrusion with respect to the width of the base is preferably about protrusion / base = 1/20 to 1/1, and more preferably about 1/15 to 2/3.

  The fine protrusions described above are arranged on the upper surface and / or the lower surface with respect to the main surface of the light guide portion, change the traveling direction of light traveling through the light guide portion, and break the total reflection condition. It works to extract light from the upper surface of the light guide part. By controlling the location, number, size, and shape of the protrusions, it is possible to obtain a surface light source without unevenness by making the brightness of the light emitted from each part in the surface uniform. It becomes possible to control the spread.

The density of the projections, for example, to the major surface 10 mm ² of the light control member, the total area of the base of the protrusions is preferably in the range of about ² 0.5 to 5 mm, 1 to 4 mm ² approximately It is more preferable that If the density of the microprojections is too high, the periphery of the light emitting element tends to be bright, and if it is too low, the in-plane brightness tends to be uneven.

    In addition, when a connected convex member is used as the light control member, as shown in FIG. 4, the connected convex member that uniformly has a plurality of convex portions having curved surfaces at least partially as the light control member 4 guides the convex portion. It is disposed in close contact with the upper surface of the light body 1. The shape, size, density, and the like of the convex portions are not particularly limited as long as the traveling direction of the total reflected light can be changed from the reflection angle. For example, the shape of the convex portions is a one-dimensionally arranged lenticular lens. Alternatively, it may be a two-dimensionally arranged lens array type or a microlens array.

  The connecting convex portion described above is usually disposed on the upper surface with respect to the main surface of the light guide, and changes the traveling direction of the light traveling through the light guide portion, thereby breaking the total reflection condition and guiding the light guide. It works to extract light from the top surface of the part.

  As a method for producing the microprojection member or the connecting convex member, a known method can be used. For example, it may be formed by injection molding integrally with the light guide using a mold, or may be photocurable. After the uneven shape is transferred to the resin to form a sheet-like projection surface, it may be bonded to the light guide 1 via an appropriate adhesive layer.

  As shown in FIG. 3, when the light control member 4 is disposed on the bottom surface of the light guide 1, the reflecting member 3 on the bottom surface side of the light guide 1 is not in contact with the light guide 1 and is normally guided. It is formed below the light body 1. On the other hand, as shown in FIG. 4, when the light control member 4 is disposed on the upper surface of the light guide 1, the reflection member 3 on the bottom surface side of the light guide 1 is formed in contact with the light guide 1. There are many.

(Surface light source element and surface light source element array)
The size of the surface light source device is not particularly limited as much as possible the surface-emitting, for example, is preferably an area of the main surface is ^{1 cm} 2 100 cm ² or ^so, and more preferably 5cm ² ~80cm 2 about.

  The surface light source element is provided with a diffusing member having a diffusing performance with a haze value of 90% at 5 mm above the main surface of the surface light source element, and one of the light emitting elements inside the surface light source element is turned on. In this case, it is preferable that the area where the decrease in brightness is within 10% of the brightness of the surface light source element is 60% or more of the main surface of the surface light source element, more preferably. It is 6.5% or more, more preferably 70% or more.

  If necessary, the surface light source element array may be composed of only surface light source elements that exhibit the same light emission characteristics, or may be used in combination with surface light source elements that exhibit different light emission characteristics. When configured with surface light source elements exhibiting the same light emission specification, it is possible to obtain a surface light source element array that emits light uniformly within the surface even when the size is increased. Further, when surface light source elements exhibiting different light emission characteristics are combined, brightness and color can be controlled for each area of the surface light source element array by independently controlling each surface light source element.

  In the surface light source element used in the present invention, the light emitted from the light emitting element is finely dispersed inside the single surface light source element and emitted from the emission surface of the surface light source element. In the light source element array, even if the light emitting area is increased, light that is finely and uniformly dispersed inside the surface light source element can be emitted from the entire surface light source element array. As a result, even if it is thin, the light intensity distribution A uniform surface light source element array can be formed.

  The surface light source element array thus obtained can be thinned even in the direct type, for example, the distance from the bottom of the light emitting element to the light emitting side of the target surface (that is, the transmissive display element). Is preferably about 5 to 15 mm, more preferably 13 mm or less, and still more preferably 10 mm or less.

(Image display device)
The image display device of the present invention can be obtained by providing a transmissive display element on the light emitting side of the surface light source array. For example, a transmissive display element 5 such as a liquid crystal panel is placed above the light guide 1 in FIG. The image display device (especially a liquid crystal display device) of the present invention can have uniform brightness and high contrast even if it is thin. In particular, when red, blue, and green LEDs are used as the light emitting elements, it is possible to provide a high-quality image display device with excellent color reproducibility even with low power consumption.

  Further, if necessary, an optical member may be disposed between the surface light source element or the surface light source element array and the transmissive display element, thereby further improving the brightness of the surface light source element and the in-plane luminance uniformity. You may adjust. As a typical optical member, a known or public optical sheet can be used, and examples thereof include a prism sheet that collects light, a diffusion sheet that spreads light, and a polarization separation sheet that controls polarization.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.

(In-plane luminance distribution of the surface light source element)
A diffusion sheet having a diffusion performance with a haze value of 90% was disposed 5 mm above the light guide. The luminance distribution of the amount of light reaching the diffusing member when the light emitting elements were individually turned on was imaged as luminance data of 256 gradations, and the image was visually evaluated. There is almost no difference in brightness between the edge part and the center part of the light guide, and the case where it shows uniform surface light is considered good, and there is a difference in brightness between the edge part and the center part of the light guide The case where it occurred and did not show uniform surface emission was defined as defective.

<Example 1>
As shown in FIG. 5, a light guide body 1 having a size of 40 mm square and a thickness of 5 mm and having three holes with a diameter of 6 mm was prepared from a polymethacrylate resin. The upper surface of the light guide 1 is flat, and the light control member 4 having 361 hemispherical shapes having a diameter of 1 mm is disposed at the position shown in FIG. A regular reflection member 3 is disposed on the side surface side and the bottom surface side of the light guide 1. Next, inside the light guide, as a light emitting element 2, one side-emitting type red LED, two green LEDs and one blue LED of Lumileds are used, and two green LEDs are square light guides as shown in FIG. The red LED and the blue LED were respectively arranged on the diagonal line of the square light guide. When the LEDs, which are light emitting elements, were individually turned on for red, green, and blue, the luminance distribution in the surface of the surface light source element was good. Therefore, the surface light source element array using such a surface light source element can perform uniform in-plane light emission.

<Example 2>
As shown in FIG. 7, a light guide body 1 having a size of 40 mm square and a thickness of 5 mm and having three holes with a diameter of 6 mm was prepared from polymethacrylate resin. An optical sheet provided with 20,000 minute irregularities having a diameter of 200 μm and a depth of 20 μm was attached to the bottom surface of the light guide via an adhesive. A film that specularly reflects on the side surface of the light guide 1 was laminated with an adhesive, and a similar specular reflection film was disposed on the lower surface with an air layer interposed therebetween. As the light emitting element, one side-emitting type red, green, and blue LED of Lumileds was arranged in a hole formed in the light guide. In order to eliminate light having an angle outside the total reflection condition, a diffusive reflecting member was placed on the LED.

When a diffusion sheet having a diffusion performance with a haze value of 90% is installed 5 mm above the main surface of the surface light source element and one green LED is turned on, the brightness of the brightest part is 2250 cd / m ² In addition, 70% or more of the area of the light guide showed a luminance higher than 2000 cd / m ² and uniformly emitted light.
When the LEDs, which are light emitting elements, were individually turned on for red, green, and blue, the luminance distribution in the surface of the surface light source element was good. Therefore, since the brightness of the end portion and the central portion of the surface light source element is the same, the surface light source element array using such a surface light source element can perform uniform in-plane light emission.
Moreover, it became white by lighting 3 color LED simultaneously. That is, almost the same luminance distribution was shown as a whole, a bright spot or the like was not observed due to a gentle luminance change, and the ratio of the minimum luminance to the maximum luminance in the plane was 0.66. Further, the chromaticity coordinates on the diffusion plate are white as a whole and hardly vary, and the difference between the maximum value and the minimum value (ΔX, ΔY) = (0.0179) in the chromaticity coordinates (X, Y). , 0.0220).

<Example 3>
As shown in FIG. 8, a light guide body 1 having a diameter of 40 mm square and a thickness of 5 mm and having three holes with a diameter of 6 mm formed with a polymethacrylate resin is provided as a light emitting element. The white LEDs were simultaneously turned on at three locations in the same manner as in Example 2 except that one side-emitting type white LED of Lumileds was placed in each hole formed in the light guide. In the diffusion sheet provided 5 mm above the main surface of the surface light source element, the luminance distribution in the surface of the surface light source element was good. Therefore, since the brightness of the end portion and the central portion of the surface light source element is the same, the surface light source element array using such a surface light source element can perform uniform in-plane light emission.

  In addition, instead of the white LED, when three red, green, and blue LEDs are arranged in three holes and these LEDs are turned on at the same time, the luminance distribution in the central part is higher than the peripheral part, and the in-plane The ratio of the minimum brightness to the maximum brightness was 0.59. Further, the chromaticity coordinate on the diffusion plate has a large color change in the vicinity of the LED, and the difference between the maximum value and the minimum value (ΔX, ΔY) = ( 0.0262, 0.0364).

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and these are also included in the present invention. It is included in the range.

Claims (7)

A surface light source element array in which a plurality of surface light source elements are arranged,
The surface light source element includes a light guide, at least one light emitting element disposed inside the light guide, a light control member disposed on at least one of an upper surface or a bottom surface of the light guide, A reflective member disposed on at least one of a side surface or a bottom surface of the light guide, and
More than 70% of the light emitted from the light emitting element is incident at an angle that totally reflects inside the light guide, and the reflection member is set to return the light to the inside of the light guide by reflection, and the light control member Is a surface light source element array set so as to change the traveling direction of the reflected light and to emit it to the outside of the light guide.   2. The surface light source element according to claim 1, wherein a diffusion sheet having a diffusion performance with a haze value of 90% is installed 5 mm above the main surface of the surface light source element, and one of the light emitting elements inside the surface light source element is provided. The surface light source element array in which the area where the decrease in brightness is within 10% of the brightness of the brightest of the surface light source elements when turned on is 60% or more of the main surface of the surface light source elements .   3. The surface light source element array according to claim 1, wherein the surface light source element includes a plurality of point light sources having different colored light as light emitting elements.   4. The surface light source element array according to claim 1, wherein the surface light source element includes light emitting diodes of three colors of red, blue, and green as light emitting elements.   5. The surface light source element array according to claim 1, wherein a distance between each light emitting element in the surface light source element is 2 to 5 times a diameter of the light emitting element.   The image display apparatus which provided the transmission type display element in the light-projection side of the surface light source element array as described in any one of Claims 1-5.   7. The image display device according to claim 6, wherein at least one optical member is provided between the surface light source element array and the transmissive display element.

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