JP4693691B2 - Light emitting device and liquid crystal display device - Google Patents

Description

  The present invention relates to a light emitting device and a liquid crystal display device including the light emitting device.

  In recent years, thin and light liquid crystal display devices have become widespread as display devices for television receivers and display devices for personal computers. The liquid crystal display device includes a liquid crystal display panel for displaying an image and the like, and a light emitting device for irradiating the liquid crystal display panel from the back side. When the light emitting device emits light, an image or the like formed by the liquid crystal display panel can be displayed. Among light emitting devices, devices using a plurality of LEDs (light emitting diodes) as light sources have been proposed.

  Japanese Patent Laid-Open No. 2005-115372 discloses a backlight including a housing having an open top surface, a light emitting diode supported on the reflective bottom surface of the housing, and a diffuser disposed above the light emitting diode. . Also, the housing has a height, and the ratio of the height to the pitch of the LED is between about 0.3 and 1.2 (for example, when the distance between the diffusion plate and the LED is 20 mm, A backlight is disclosed in which the distance between the LEDs is 6 mm or more and 24 mm or less. This backlight is disclosed as having high efficiency, good color uniformity, and a spatially and temporally adjustable luminance distribution.

  In Japanese Patent Application Laid-Open No. 2003-297127, a light emitting diode and an optical element are provided, and the optical element emits light by changing the refraction characteristics of light from the light emitting diode according to the intensity of light from the light emitting diode. A backlight device is disclosed that is configured so that the density of irradiated light is uniform. It is disclosed that a light emitting element having a function of spreading the light emitted from the light emitting diode near the center and condensing the light near the center is disclosed. According to this backlight device, it is disclosed that uniform light can be supplied to almost the entire area of the display panel while reducing the size.

  Japanese Laid-Open Patent Publication No. 2006-19141 discloses a backlight including a light guide plate having a recess and a plurality of side-emitting light emitting elements arranged in the recess. The side-emitting light emitting element includes a side-emitting red LED, a side-emitting green LED, and a side-emitting blue LED. The light emitted in the side surface direction is introduced into the light guide plate from the side surface of the recess, and propagates through the light guide plate to cause mixing of three colors. The light is emitted to the outside as backlight light through the diffusion sheet disposed on the upper surface. According to this backlight, it is disclosed that light from each light emitting element of different light emission color light sources can be mixed efficiently.

Japanese Patent Application Laid-Open No. 2005-340750 discloses an LED package including red, green, and blue LEDs arranged on a substrate, and a mold portion having a cylindrical side surface shape by sealing these LEDs. Further, it is disclosed that a material that does not absorb light is applied to the surface of the substrate, and protruding light scattering means is formed in a dot shape on the upper surface. According to this LED package, it is disclosed that a sufficient light traveling path can be secured and white light having a uniform hue and intensity can be emitted.
JP 2005-115372 A JP 2003-297127 A JP 2006-19141 A JP 2005-340750 A

  In general, the light emission characteristics of an LED are such that the light intensity at the central portion is the strongest, so that the area where the LED is disposed becomes bright, but the surrounding area becomes dark. For example, in a direct type backlight device in which a plurality of LEDs are arranged directly under a liquid crystal display panel, a portion where the LEDs are arranged is bright and a portion around the portion where the LEDs are arranged is dark. As described above, the light emitting device including the light source having the angle dependency on the light emission intensity has a problem that the luminance becomes non-uniform.

  The backlight disclosed in Japanese Patent Application Laid-Open No. 2005-115372 has a problem that the number of LEDs increases. For example, when the distance between the LED and the diffusion plate is about 20 mm, that is, when the thickness of the backlight is about 20 mm, the distance between the LEDs needs to be 6 mm or more and 24 mm or less. When the interval between the LEDs is increased beyond this interval, there is a problem that uniform brightness cannot be realized on the surface of the backlight. For example, when a backlight device to be attached to a 45-inch size liquid crystal display device is manufactured, 1300 or more LEDs are required. Thus, when the space | interval of LED is narrowed, there exists a problem that many LEDs will be needed.

  Here, in FIG. 20, on the premise of using high-efficiency LEDs, in a 45-inch size liquid crystal display device, 900 LEDs are reduced, and the backlight device is manufactured using 400 LEDs. The luminance distribution is shown. The horizontal axis is the position on the emission surface of the backlight device, and the vertical axis is the luminance of light at each position. The alternate long and short dash line represents the luminance of the light from each LED, and the solid line represents the sum of the light from each LED.

  When the definition of the luminance unevenness on the surface of the backlight device is [(maximum luminance−minimum luminance) / (maximum luminance)], a large luminance unevenness of about 23% appears. Thus, when the number of LEDs is reduced, there is a problem that it is difficult to manufacture a light emitting device with uniform light intensity on the emission surface.

  Further, in the backlight device disclosed in Japanese Patent Application Laid-Open No. 2003-297127, it is considered that light having a uniform luminance distribution can be emitted when the distance between the LEDs is small to some extent. In order to reduce the number of LEDs, there is a problem that it is difficult to make the luminance uniform when the interval between the LEDs is widened.

  In the above Japanese Patent Laid-Open No. 2006-19141, a side-emitting LED having a special lens mounted on the upper part of the light source is necessary, and there is a problem that the device is expensive.

  An object of this invention is to provide the light-emitting device which light-emits with uniform brightness | luminance, and a liquid crystal display device provided with the same.

The light emitting device according to the present invention includes a light guide plate including an incident surface and an output surface that are formed to be substantially parallel to each other. The light guide plate includes a plurality of light sources for supplying light. The optical path changing means for changing the traveling direction of the light is provided. A light emitting means formed to emit the light traveling through the light guide plate; The light guide plate is formed in a plate shape. The optical path changing means is configured so that a part of the light supplied to the inside of the light guide plate travels inside the light guide plate while being reflected by at least one of the incident surface and the exit surface. It is formed so as to change the traveling direction of light. The light emitting means is formed to emit at least part of the light traveling inside the light guide plate from the emission surface.

In the above invention, preferably, the optical path changing means is arranged on the incident surface.
Preferably, in the above invention, the optical path changing means includes a diffraction grating.

  In the above invention, preferably, the diffraction grating includes a diffraction surface for diffracting the light. The diffractive surface has an uneven cross-sectional shape.

  In the present invention, preferably, the light guide plate is formed such that the incident surface and the light exit surface are substantially parallel to each other. The diffraction grating includes a diffraction surface for diffracting the light. The diffractive surface has an uneven cross-sectional shape. The irregularities are formed such that the pitch at the center is narrower than the pitch at the periphery. The unevenness is formed such that the light diffracted at the central portion and the light diffracted at the peripheral portion are directed in substantially the same direction. The unevenness is formed so that the diffracted light is totally reflected on the exit surface and the entrance surface.

In the above invention, preferably, the light emitting means includes a reflector disposed on the incident surface. The reflector is formed in a cone shape. When the incident light with respect to the normal of the exit surface or the normal of the entrance surface is α ° when the light traveling through the light guide plate is incident on the exit surface and the entrance surface, The apex angle is formed to be approximately (180−α) °.

  In the above invention, preferably, the light emitting means includes a reflector disposed on the incident surface. The reflector is formed in a band shape when viewed in plan. The reflector is formed concentrically around the light source when viewed in plan. The reflector is formed so as to be inclined with respect to the incident surface, and has a reflecting surface that reflects the light traveling inside the light guide plate. When the incident light with respect to the normal of the exit surface or the normal of the entrance surface when the light traveling through the light guide plate is incident on the exit surface or the entrance surface is α °, The angle formed by the incident surface and the reflecting surface is approximately (α / 2) °.

  In the above invention, preferably, the light emitting means includes a reflector disposed on the incident surface. The reflector is formed to have a scattering effect.

  In the above invention, preferably, the plurality of light emitting means are arranged between the plurality of light sources. The light emitting means is arranged so that the number density gradually decreases from a substantially middle point of a line segment connecting the light sources to the light source.

  The liquid crystal display device based on this invention is equipped with the above-mentioned light-emitting device and the liquid crystal display panel arrange | positioned so that the light which the said light-emitting device emits may inject.

  ADVANTAGE OF THE INVENTION According to this invention, the light-emitting device which light-emits with uniform brightness | luminance, and a liquid crystal display device provided with this can be provided.

(Embodiment 1)
With reference to FIGS. 1-4, the light-emitting device in Embodiment 1 based on this invention and a liquid crystal display device provided with the same are demonstrated.

  FIG. 1 is a schematic cross-sectional view of the liquid crystal display device according to the present embodiment. The liquid crystal display device in the present embodiment includes a liquid crystal display panel 1. The liquid crystal display panel 1 is formed in a plate shape. The liquid crystal display panel 1 includes a substrate 3a as a first substrate having a pixel electrode formed on the surface so as to correspond to each pixel, and a substrate 3b as a second substrate.

  The substrates 3a and 3b in the present embodiment are formed of glass plates. A liquid crystal layer 2 is formed between the substrate 3a and the substrate 3b. The liquid crystal layer 2 is sealed in a space between the substrate 3a and the substrate 3b. A polarizing plate 4a as a first polarizing plate is disposed on the outer surface of the substrate 3a. The polarizing plate 4a is disposed so as to cover the main surface of the substrate 3a. A polarizing plate 4b as a second polarizing plate is disposed on the outer surface of the substrate 3b. The polarizing plate 4b is disposed so as to cover the main surface of the substrate 3b.

  The liquid crystal display device in the present embodiment includes an optical sheet 5. The optical sheet 5 is disposed on the substrate 3 a side of the surface of the liquid crystal display panel 1. The optical sheet 5 is disposed between the liquid crystal display panel 1 and the backlight device 41. Optical sheet 5 in the present embodiment includes brightness enhancement films 6 and 7. The brightness enhancement film 6 is DBEF (Dual Brightness Enhancement Film). The brightness enhancement film 7 is a BEF (Brightness Enhancement Film). The optical sheet 5 includes a diffusion plate 8.

  The liquid crystal display device in this embodiment includes a backlight device 41 as a light emitting device. The backlight device 41 in the present embodiment is a light emitting device directly under the back surface in which a plurality of light sources are arranged on the back surface of the liquid crystal display panel 1. The backlight device 41 is a surface light emitting device formed in a planar shape. The backlight device 41 and the liquid crystal display panel 1 are disposed so as to face each other. The backlight device 41 is formed so as to emit light toward the entire main surface of the liquid crystal display panel 1.

  The backlight device 41 in the present embodiment includes a reflecting plate 13. The backlight device 41 includes a plurality of LEDs 10 as light sources. LED 10 in the present embodiment is formed to emit white light. The LEDs 10 are arranged away from each other. The LED 10 is disposed on the surface of the reflection plate 13. The reflection plate 13 is formed so as to reflect the light of the LED 10.

  The backlight device 41 in the present embodiment includes a light guide plate 11. The light guide plate 11 is formed in a plate shape. The light guide plate 11 has front and back main surfaces. The light guide plate 11 has an incident surface 11a on which the light of the LED 10 is mainly incident and an output surface 11b on which the light of the LED 10 is mainly emitted. The entrance surface 11a and the exit surface 11b are formed in a planar shape. The entrance surface 11a and the exit surface 11b are formed so as to be substantially parallel to each other.

  The light guide plate 11 in the present embodiment is arranged away from the LED 10. The LED 10 is disposed so as to face the incident surface 11 a of the light guide plate 11. The main body of the light guide plate 11 is formed of a material having a low light absorption rate of the LED 10. The main body of the light guide plate 11 is made of, for example, a synthetic resin.

  The light guide plate 11 in the present embodiment includes a scatterer 31 as an optical path changing unit. The scatterer 31 changes the traveling direction of at least part of the light so that at least part of the light supplied to the light guide plate 11 travels inside the light guide plate while being reflected by the incident surface 11a or the exit surface 11b. It is formed to change. The scatterer 31 is formed such that a part of incident light passes through the scatterer 31 and the other part is reflected by the surface of the scatterer 31.

  The scatterer 31 can be formed, for example, by applying white ink to the surface of the main body of the light guide plate 11. Alternatively, the scatterer 31 is formed by forming a part of the surface of the main body of the light guide plate 11 into a so-called textured surface for scattering light.

  The scatterer 31 in the present embodiment is disposed on the emission surface 11 b of the light guide plate 11. The scatterers 31 are arranged away from each other. The scatterer 31 is disposed directly above the LED 10. The scatterer 31 is disposed so as to correspond to the position of the LED 10.

The light guide plate 11 in the present embodiment includes a reflector 21 as light emitting means. The reflector 21 in the present embodiment is formed in a conical shape. The reflector 21 in the present embodiment has a conical portion formed when the main body of the light guide plate 11 is molded, and a reflective film having a high reflectivity is formed on the surface of the conical portion. The reflective film in the present embodiment is formed by silver vapor deposition.

  The reflector 21 is disposed on the incident surface 11 a of the light guide plate 11. The reflectors 21 are arranged away from each other. The reflector 21 is disposed between the positions where the scatterers 31 are disposed. The reflector 21 is disposed at a substantially central portion between the positions where the scatterers 31 are disposed.

  FIG. 2 is a schematic plan view of the backlight device according to this embodiment. 1 is a cross-sectional view taken along the line II in FIG. The plurality of LEDs 10 in the present embodiment are arranged in a grid pattern. LED10 in this Embodiment is arrange | positioned by what is called square arrangement. The scatterer 31 is formed to have a circular planar shape. The scatterer 31 is arranged so that the LED 10 is located at the center of a circle when seen through in plan view. One scatterer 31 is formed for each LED 10. The reflectors 21 in the present embodiment are arranged in a square arrangement.

  Referring to FIG. 1, in backlight device 41 in the present embodiment, light is emitted from LED 10 as indicated by arrow 61. Light emitted from the LED 10 passes through the inside of the main body of the light guide plate 11 and enters the scatterer 31. A part of the light incident on the scatterer 31 passes through the scatterer 31 as indicated by an arrow 63. When passing through the scatterer 31, some light is scattered.

  A part of the light incident on the scatterer 31 is reflected. A part of the light reflected by the scatterer 31 travels inside the light guide plate 11 while repeating total reflection on the incident surface 11a and the exit surface 11b as indicated by an arrow 62. On the incident surface 11a, a part of the light reflected by the scatterer 31 passes through the incident surface 11a without satisfying the incident angle of total reflection. This light is reflected by the surface of the reflection plate 13 and enters the light guide plate 11 again. Light that does not satisfy the incident angle of total reflection on the emission surface 11 b is emitted toward the liquid crystal display panel 1.

  A part of the light reflected by the scatterer 31 enters the reflector 21. This light is reflected by the surface of the reflector 21 and is emitted toward the liquid crystal display panel 1 as indicated by an arrow 64. The emitted light indicated by the arrow 64 is emitted toward the liquid crystal display panel 1 from a position different from the position where the LED 10 is disposed. In the present embodiment, light is emitted around the position of the substantially middle point between the LEDs 10.

  The light emitted from the backlight device 41 enters the liquid crystal display panel 1 through the optical sheet 5. In the liquid crystal display panel 1, for example, light is transmitted or shielded in each pixel, and an image, a video, or the like can be displayed.

  FIG. 3 is a graph illustrating the luminance of light of the backlight device in this embodiment. The horizontal axis is the position on the exit surface of the light guide plate of the backlight device, and the vertical axis is the luminance of light. A broken line shows the light radiate | emitted by reflecting on the surface of a reflector. The alternate long and short dash line indicates the light emitted through the scatterer. The solid line indicates the sum of light emitted from the backlight device.

  The backlight device according to the present embodiment is formed so that the light quantity ratio between the light passing through the scatterer 31 and the light reflected and emitted from the surface of the reflector 21 is approximately 1: 1. As shown by the graph of the sum of the emitted light indicated by the solid line, it can be seen that there is almost no luminance distribution, and the luminance of the light is substantially uniform across the emission surface of the backlight device.

  That is, when the definition of the luminance unevenness on the surface of the backlight device is [(maximum luminance−minimum luminance) / (maximum luminance)], the luminance unevenness is almost 0%. Thus, in the backlight device according to the present embodiment, light can be emitted almost uniformly. Furthermore, even when the interval between the light sources is widened, a light emitting device with uniform luminance can be provided. Alternatively, the number of light sources can be reduced.

  In the liquid crystal display device, a device having uniform luminance over the entire display surface can be provided.

The reflector as the light emitting means in the present embodiment is formed in a cone . For cones whose surface is inclined, the light incident in response to the incident angle is reflected toward the various directions. That is, it has a scattering effect that the light flux spreads. For this reason, the brightness | luminance of the light in the surface of a backlight apparatus can be made more uniform.

  In the present embodiment, the LEDs as the light sources are arranged in a square arrangement, but the arrangement is not limited to this form, and any arrangement method can be adopted.

  FIG. 4 shows a schematic plan view of another LED arrangement method in the present embodiment. In the light emitting device in FIG. 4, the LEDs 10 are arranged at the corners of regular hexagons. That is, the LEDs 10 in FIG. 4 are arranged in a hexagonal arrangement. In addition, the LED as the light source can be disposed at an arbitrary position.

  The scatterer in the present embodiment is coated with white ink on the surface of the light guide plate. However, the scatterer is not limited to this form, and the optical path changing means is formed so that at least part of the traveling direction of light can be changed. It doesn't matter if it is.

  The light emitting means in the present embodiment includes a conical reflector, but is not limited to this form, and any shape can be adopted. The light emitting means may be formed so that at least a part of the light traveling inside the light guide plate is emitted from the emission surface. Further, the cone is not limited to a cone, and may be formed in a quadrangular pyramid shape, for example. In the present embodiment, one light emitting unit is disposed between the light sources, but the present invention is not limited to this mode, and a plurality of light emitting units may be disposed between the light sources. Absent.

  The light source in the present embodiment has been described by taking an example of an LED that emits white light. However, the present invention is not limited to this mode. For example, a plurality of types of LEDs that emit red, green, and blue colors are equally provided. You may arrange in. Alternatively, the present invention can be applied to a device that emits arbitrary light as a light source. In particular, by applying the present invention to a light-emitting device provided with a light source having an angle dependency on the light emission intensity, the effect of uniforming the brightness becomes remarkable.

(Embodiment 2)
With reference to FIG. 5, the light-emitting device and the liquid crystal display device in Embodiment 2 based on this invention are demonstrated. The liquid crystal display device in this embodiment is different from that in Embodiment 1 in the arrangement of scatterers.

  The liquid crystal display device in the present embodiment includes a backlight device 42 as a light emitting device. The backlight device 42 includes the light guide plate 11 and the reflection plate 13 on which the LEDs 10 are arranged. The light guide plate 11 has a scatterer 32 as optical path changing means. The scatterer 32 is disposed on the incident surface 11 a of the light guide plate 11. The scatterer 32 is disposed directly above the LED 10.

  The light guide plate 11 includes a reflector 22 as light emitting means. The reflector 22 is formed in a conical shape. The reflector 22 is disposed on the incident surface 11 a of the light guide plate 11. The reflector 22 is disposed between the scatterers 32. The reflector 22 is disposed at a substantially central portion between the scatterers 32.

  In the backlight device according to the present embodiment, the light from the LED 10 enters the scatterer 32 as indicated by an arrow 61. At this time, the light emitted from the LED 10 directly enters the scatterer 32 without passing through the inside of the main body of the light guide plate 11. The light incident on the scatterer 32 is scattered or reflected.

  A part of the light incident on the scatterer 32 passes through the emission surface 11 b of the light guide plate 11 and is emitted toward the liquid crystal display panel as indicated by an arrow 63. A part of the light incident on the scatterer 32 is totally reflected by the emission surface 11 b as shown by an arrow 62 and travels inside the light guide plate 11. A part of the light traveling inside the light guide plate 11 enters the reflector 22. As indicated by an arrow 64, this light is reflected by the surface of the reflector 22 and is emitted from the light guide plate 11 toward the liquid crystal display panel 1.

  The light reflected by the surface of the reflector 22 is emitted from a position different from the position where the LED 61 is disposed. Light that does not satisfy the incident angle of total reflection on the emission surface 11 b is emitted from the emission surface 11 b toward the liquid crystal display panel 1. Light that does not satisfy the incident angle of total reflection on the incident surface 11a is incident on the reflecting plate 13 from the incident surface 11a, is reflected on the surface of the reflecting plate 13, and then enters the light guide plate 11 again.

  As described above, in the light emitting device in the present embodiment, the scatterer 32 as the optical path changing unit is arranged on the incident surface 11 a of the light guide plate 11. That is, a part of the scatterer 32 is disposed so as to contact the incident surface 11a. With this configuration, the light emitted from the LED 10 is reflected by the incident surface 11a of the light guide plate 11, and the light that enters the light guide plate 11 is emitted from the incident surface 11a toward the reflective plate 13 is reduced. The amount of light traveling inside the light guide plate 11 can be increased. More light can be emitted from a position different from the position where the LED is arranged, and the luminance can be made uniform more easily.

  Moreover, in this Embodiment, the scatterer and the reflector are arrange | positioned at one main surface of the light-guide plate. That is, the scatterer and the reflector are formed on the same surface of the light guide plate. With this configuration, the light guide plate can be easily manufactured and productivity can be improved.

  Other configurations, operations, and effects are the same as those in the first embodiment, and thus description thereof will not be repeated here.

(Embodiment 3)
With reference to FIG. 6, the light-emitting device and the liquid crystal display device in Embodiment 3 based on this invention are demonstrated. In the present embodiment, the configuration of the optical path changing means of the light guide plate is different from that of the first embodiment.

  The liquid crystal display device in the present embodiment includes a backlight device 43. The backlight device 43 includes the light guide plate 14. The light guide plate 14 is formed in a plate shape. The light guide plate 14 has an entrance surface 14a and an exit surface 14b. The entrance surface 14a and the exit surface 14b are formed in a planar shape and are substantially parallel to each other.

  The light guide plate 14 in the present embodiment has a concave lens portion 14c as an optical path changing means. The concave lens portion 14c is formed on the incident surface 14a. The concave lens portion 14c is formed so as to be recessed from the surface of the incident surface 14a. The concave lens portion 14c has a function of a concave lens and is formed to scatter incident light. A reflector 21 is disposed between the concave lens portions 14c.

  In the present embodiment, the light emitted from the LED 10 enters the concave lens portion 14 c as indicated by an arrow 61. A part of the light incident on the concave lens portion 14 c goes to the liquid crystal display panel as indicated by an arrow 66. As shown by an arrow 65, a part of the light incident on the concave lens portion 14c travels inside the light guide plate 14 while satisfying the condition of the incident angle of total reflection and totally reflecting on the output surface 14b or the incident surface 14a. . A part of the light traveling inside the light guide plate 14 enters the reflector 21.

  A part of the light incident on the reflector 21 is emitted from the light guide plate 14 toward the liquid crystal display panel 1 as indicated by an arrow 67. Alternatively, the light that does not satisfy the condition of total reflection on the emission surface 14 b is emitted from the light guide plate 14 toward the liquid crystal display panel 1. Light is reflected from the surface of the reflector 21 and travels toward the liquid crystal display panel 1, whereby light is emitted from a position different from the position where the LED 10 is disposed.

  The optical path changing means in the present embodiment includes a concave lens portion 14c. With this configuration, it is possible to reduce the light reflected from the incident surface 14 a of the light guide plate 14 among the light emitted from the LEDs 10, and to introduce more light into the light guide plate 14.

  Since other configurations, operations, and effects are the same as those in the first or second embodiment, description thereof will not be repeated here.

(Embodiment 4)
With reference to FIGS. 7 to 12, a light-emitting device and a liquid crystal display device according to Embodiment 4 of the present invention will be described. In the present embodiment, the configuration of the optical path changing means is different from that of the second embodiment.

  FIG. 7 is a schematic cross-sectional view of the liquid crystal display device in the present embodiment. The liquid crystal display device in the present embodiment includes a backlight device 44. The backlight device 44 includes the light guide plate 11.

  The light guide plate 11 in the present embodiment includes a diffraction grating 33 as optical path changing means. The diffraction grating 33 is disposed on the incident surface 11 a of the light guide plate 11. The diffraction grating 33 is disposed directly above the LED 10. The reflector 22 is disposed between the diffraction gratings 33.

  The reflector 22 in the present embodiment is formed in a conical shape. The circular diameter of the bottom surface of the reflector 22 is formed to be 0.5 mm. The reflector 22 is formed so that the apex angle is 120 °.

  FIG. 8 shows a schematic plan view of the diffraction grating portion of the backlight device in the present embodiment. FIG. 9 is a schematic cross-sectional view of the diffraction grating portion of the backlight device according to this embodiment. 9 is a cross-sectional view taken along the line IX-IX in FIG.

  The diffraction grating 33 in the present embodiment has an uneven surface 33a. The uneven surface 33a becomes a light diffraction surface. The uneven surface 33a includes concentric unevenness. The cross-sectional shape of the unevenness is formed to be rectangular. The diffraction grating 33 is formed so that the uneven pitch of the surface is 1 μm. LED10 is arrange | positioned in the approximate center part of the unevenness | corrugation of the uneven surface 33a. That is, the LED 10 is arranged at the center of a concentric circle when the diffraction grating 33 is seen through in a plane.

  When the acrylic resin is used as the main body of the light guide plate 11, the diffraction grating can be formed by, for example, a lithography method. Or it can form by apply | coating a shaping | molding base material on the surface of the light-guide plate 11, and pressing after heating the metal mold | die of a diffraction grating. The diffraction grating can be formed more easily than a lens or the like. Moreover, the diffraction grating can be manufactured at low cost.

  As the diffraction grating, for example, the refractive index of the light guide plate can be 1.5, the wavelength of the light emitted from the LED can be 500 nm, the depth of the diffraction grating can be 0.5 μm, and the uneven shape can be rectangular. Almost 100% of the light emitted from the LED is diffracted by this diffraction grating. The light diffracted by the diffraction grating is either totally reflected at the exit surface of the light guide plate or passes through the exit surface toward the liquid crystal display panel.

  Referring to FIG. 7, in the present embodiment, light emitted from LED 10 enters diffraction grating 33 as indicated by arrow 61. A part of the light incident on the diffraction grating 33 goes to the liquid crystal display panel 1 as indicated by an arrow 69 without satisfying the condition of total reflection at the emission surface 11b. A part of the light incident on the diffraction grating 33 travels through the light guide plate 11 while being repeatedly diffracted after being diffracted as indicated by an arrow 68.

  A part of the light traveling inside the light guide plate 11 is reflected by the surface of the reflector 22 and travels toward the liquid crystal display panel 1 as indicated by an arrow 70. Of the light traveling inside the light guide plate 11, the light that does not satisfy the condition of total reflection on the emission surface 11 b is directed to the liquid crystal display panel 1.

  In the backlight device according to the present embodiment, when the light amount ratio between the light traveling through the diffraction grating toward the liquid crystal display panel and the light reflected from the surface of the reflector toward the liquid crystal display panel is 1: 1, The luminance on the surface of the backlight device is the same as in the case of FIG. 4 in the first embodiment. Also in this embodiment, the luminance can be made uniform over the entire emission surface of the backlight device.

  The optical path changing means in the present embodiment includes a diffraction grating. With this configuration, the optical path changing means can be easily formed. Alternatively, the optical path changing means can be manufactured at low cost. Further, the diffraction efficiency and the diffraction angle can be changed by changing the grating pitch of the diffraction grating and the depth of the unevenness of the diffraction surface. For example, it is possible to easily optimize the ratio of the light exiting the diffraction grating to be totally reflected by the exit surface of the light guide plate and the light directed to the liquid crystal display panel without being totally reflected by the exit surface. As a result, a desired luminance distribution can be obtained on the surface of the light emitting device.

  FIG. 10 shows a graph of light luminance when the diffraction efficiency deviates from the design value due to a manufacturing failure of the diffraction grating. In the graph shown in FIG. 10, the ratio of the amount of light directly going to the liquid crystal display panel through the diffraction grating and the light reflected by the surface of the reflector and going to the liquid crystal display panel is 5: 3. ing. The luminance of the light that goes directly to the liquid crystal display panel through the diffraction grating is larger than the luminance of the light reflected by the reflector.

  As shown in FIG. 10, although the uniformity of the sum of the light emitted from the light guide plate is reduced, the luminance uniformity is greatly improved compared to the example in the prior art shown in FIG. I understand. In the example shown in FIG. 10, the luminance unevenness is about 10%. Such non-uniformity can be used practically without any problem.

  As described above, the backlight device in this embodiment can sufficiently improve the luminance uniformity even if a manufacturing error or the like occurs in the diffraction grating. For this reason, the defective rate of a product can be remarkably reduced.

  Depending on the characteristics of the light source and the characteristics of the light guide plate, the structure of the diffractive surface, such as the pitch and depth of the unevenness of the diffraction grating, or the shape and size of the reflector, etc., has a uniform brightness on the surface of the light emitting device. It is preferable to be formed so as to be obtained.

  FIG. 11 is a schematic plan view of another diffraction grating portion of the backlight device according to the present embodiment. FIG. 12 is a schematic cross-sectional view of another diffraction grating portion of the backlight device according to this embodiment. 12 is a cross-sectional view taken along line XII-XII in FIG.

  The other diffraction grating 34 in the present embodiment has an uneven surface 34a as a diffraction surface. The uneven surface 34a is formed concentrically when viewed in plan. The uneven surface 34a has a plurality of triangular protrusions in the cross-sectional shape. The convex part of the concavo-convex surface 34a is formed so that the tip is sharp. Concavities and convexities are formed by having a shape in which triangular convex portions are continuously connected. The uneven surface 34a is formed in a sawtooth shape. The diffraction grating 34 is disposed so that the uneven surface 34 a faces the LED 10.

  In the other diffraction grating 34, the light emitted from the LED 10 can be diffracted in a desired direction. For example, among the light diffracted by the diffraction grating, the amount of light totally reflected on the surface of the light guide plate can be increased. The amount of light traveling inside the light guide plate can be increased, and the amount of light emitted from a position different from the position where the LEDs are arranged can be increased. As a result, it is possible to easily make the luminance uniform.

  Other configurations, operations, and effects are the same as those in the first to third embodiments, and thus description thereof will not be repeated here.

(Embodiment 5)
A light emitting device and a liquid crystal display device according to a fifth embodiment of the present invention will be described with reference to FIGS. The light emitting device and the liquid crystal display device in this embodiment are different from those in Embodiment 4 in the configuration of the diffraction grating.

  FIG. 13 shows a first schematic cross-sectional view of a backlight device as a light emitting device in the present embodiment. The backlight device 45 includes a light guide plate 11. The light guide plate 11 in the present embodiment includes a diffraction grating 35 disposed on the incident surface 11a.

  The diffraction grating 35 includes an uneven surface 35a having a sawtooth cross-sectional shape. The unevenness of the uneven surface 35a in the present embodiment is formed concentrically when viewed in plan. The unevenness in the present embodiment is formed so that the pitch of the central part is smaller than the pitch of the peripheral part. The unevenness in the present embodiment is formed so that the pitch gradually increases from the central portion toward the outer peripheral portion.

  The uneven surface 35a in the present embodiment is formed so that the light diffracted at the central portion of the diffraction grating 35 and the light diffracted at the peripheral portion are directed in substantially the same direction. That is, the light diffracted at the central portion of the diffraction grating and the light diffracted at the peripheral portion are formed so as to be incident on the emission surface 11b at substantially the same incident angle.

  As indicated by the arrow 61, the light emitted from the LED 10 is emitted with a certain extent. Most of the light diffracted by the uneven surface 35 a is diffracted so as to be directed in substantially the same direction as indicated by an arrow 71. As indicated by arrows 72 and 73, light that does not satisfy the condition of total reflection at the exit surface 11b out of the light diffracted by the uneven surface 35a is emitted from the exit surface 11b toward the liquid crystal display panel. As indicated by an arrow 75, among the light diffracted by the concavo-convex surface 35 a, light that satisfies the condition of total reflection at the exit surface 11 b travels while repeating total reflection inside the light guide plate 11.

  In FIG. 14, the 2nd schematic sectional drawing of the backlight apparatus in this Embodiment is shown. The light guide plate 11 in the present embodiment has a conical reflector 23. The reflector 23 is disposed away from the diffraction grating 35. The reflector 23 is disposed between the diffraction gratings 35. The diffraction grating 35 is formed so as to diffract light at the incident surface 11a or the exit surface 11b at an angle that satisfies the condition of total reflection and in substantially the same direction. Can increase the light to be.

  As indicated by arrows 71 and 75, part of the light traveling inside the light guide plate 11 is reflected by the surface of the reflector 23. By reflecting on the surface of the reflector 23, the light is emitted from the backlight device 45 as indicated by an arrow 74.

  FIG. 15 shows an enlarged schematic cross-sectional view of a reflector portion in the present embodiment. FIG. 15 is a cross-sectional view taken along the direction from the diffraction grating 35 toward the reflector 23. The reflector 23 has an apex angle θ1. The reflector 23 has a reflection surface 23 a for reflecting light traveling inside the light guide plate 11. The reflecting surface 23 a is formed to be inclined with respect to the incident surface 11 a of the light guide plate 11.

  In the present embodiment, when the light traveling through the light guide plate 11 enters the exit surface 11b or the entrance surface 11a, it enters at substantially the same angle. The light traveling through the light guide plate 11 is incident at an angle α with respect to the normal line 81 of the emission surface 11b or the normal line of the incident surface 11a.

  The reflector 23 in the present embodiment is formed so that the apex angle θ1 is approximately (180−α) °. With this configuration, as indicated by an arrow 74, the intensity of light emitted in a direction substantially perpendicular to the emission surface 11b can be increased. As a result, for example, the brightness of the front surface of the backlight device can be increased. Alternatively, it is possible to eliminate a brightness enhancement film such as BEF having a function of emitting spread light in the front direction.

  For example, when the diffraction grating 35 is designed so that the incident angle α of light on the exit surface 11b and the incident surface 11a is approximately 45 °, the apex angle θ1 of the reflector 23 is (180−45) °, that is, By setting the angle to 135 °, the luminance at the front can be increased.

  Since other configurations, operations, and effects are the same as those in the first to fourth embodiments, description thereof will not be repeated here.

(Embodiment 6)
A light-emitting device and a liquid crystal display device according to Embodiment 6 according to the present invention will be described with reference to FIGS.

  FIG. 16 is a schematic cross-sectional view of the backlight device in this embodiment. The backlight device 46 in the present embodiment includes a light guide plate 11, and the light guide plate 11 includes a diffraction grating 35. The diffraction grating 35 in the present embodiment is formed so as to be able to diffract light in one direction. The light guide plate 11 in the present embodiment includes a reflector 25 as light emitting means. The reflector 25 is disposed on the incident surface 11 a of the light guide plate 11.

  The reflector 25 is formed so that the cross-sectional shape is a triangle. The reflector 25 has a reflecting surface 25a. The reflection surface 25 a is formed so as to be inclined with respect to the incident surface 11 a of the light guide plate 11. The reflection surface 25 a is formed so as to face the diffraction grating 35. The reflection surface 25 a is formed so as to be able to reflect light traveling inside the light guide plate 11.

  FIG. 17 shows a schematic plan view of the backlight device in the present embodiment. The reflector 25 in the present embodiment is formed in a band shape when viewed in plan. The reflectors 25 are formed at intervals. The reflector 25 is formed concentrically when viewed from above. The reflector 25 is formed such that the LED 10 is disposed at the center when viewed in plan.

  FIG. 18 shows an enlarged schematic cross-sectional view of the reflector portion of the light guide plate in the present embodiment. The light diffracted by the diffraction grating 35 travels while repeating total reflection at the entrance surface 11a or the exit surface 11b as indicated by an arrow 75. The light traveling inside the light guide plate 11 is incident on the normal line of the incident surface 11a or the normal line 81 of the output surface 11b at an angle α. That is, the light advances so that the incident angle of the light with respect to the incident surface 11a or the emitting surface 11b is α °.

  In the present embodiment, the reflection surface 25a is formed such that the inclination angle θ2 is (90−α) °. For this reason, the light reflected by the reflecting surface 25 a can be directed in a direction substantially perpendicular to the emitting surface 11 b as indicated by an arrow 74. Also in the light-emitting device in this embodiment, the front luminance can be improved. Alternatively, it is possible to eliminate a brightness enhancement film such as BEF having a function of emitting spread light in the front direction.

  Further, since the reflectors are formed concentrically when viewed in plan, the luminance on the surface of the light emitting device can be made more uniform.

  Since other configurations, operations, and effects are the same as those in the first to fifth embodiments, description thereof will not be repeated here.

(Embodiment 7)
Referring to FIG. 19, a light emitting device and a liquid crystal display device according to Embodiment 7 based on the present invention will be described. In the present embodiment, the configuration of the reflector as the light emitting means is different from that of the first embodiment.

  FIG. 19 is a schematic plan view of the backlight device according to the present embodiment. In the backlight device according to the present embodiment, a plurality of reflectors 24 as light emitting means are arranged. The reflector 24 is disposed so as to surround the LED 10 when seen through in plan. The reflector 24 is formed so that the number density gradually increases as the distance from the LED 10 increases. That is, the reflectors 24 are arranged so that the number density is the highest at the midpoint of the line segment connecting the LEDs 10, and the density is gradually reduced toward the LEDs 10.

  In the present embodiment, when the portion where the LED 10 is arranged is brightest due to the characteristics of the LED 10 to be used and the characteristics of the scatterer 31 and the luminance decreases as the distance from the LED 10 decreases, the light at the portion away from the LED 10 The brightness can be increased. The brightness can be made more uniform on the surface of the backlight device.

  As described above, when a plurality of light emitting means are arranged, the luminance on the surface of the backlight device can be made more uniform by arranging many light emitting means in the portion where the luminance of light is weak.

  Since other configurations, operations, and effects are the same as those in the first to sixth embodiments, description thereof will not be repeated here.

  In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In the above description, descriptions such as “up” and “down” do not indicate absolute vertical directions in the vertical direction, but indicate relative positions.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 1. FIG. 1 is a schematic plan view of a backlight device according to Embodiment 1. FIG. 4 is a graph of luminance on the surface of the backlight device in the first embodiment. FIG. 5 is a schematic plan view illustrating the arrangement of other LEDs in the first embodiment. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device in a second embodiment. 6 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 3. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 4. FIG. 6 is a schematic plan view of a diffraction grating in Embodiment 4. FIG. 6 is a schematic cross-sectional view of a diffraction grating in Embodiment 4. FIG. 14 is a graph illustrating the luminance of a backlight when an error occurs in the diffraction grating in the fourth embodiment. 10 is a schematic plan view of another diffraction grating according to Embodiment 4. FIG. 10 is a schematic cross-sectional view of another diffraction grating in Embodiment 4. FIG. FIG. 10 is a schematic cross-sectional view of a backlight device in a fifth embodiment. FIG. 10 is another schematic cross-sectional view of the backlight device in the fifth embodiment. FIG. 10 is an enlarged schematic cross-sectional view of a reflector portion in a fifth embodiment. FIG. 10 is a schematic cross-sectional view of a backlight device in a sixth embodiment. FIG. 10 is a schematic plan view of a backlight device in a sixth embodiment. FIG. 10 is an enlarged schematic cross-sectional view of a reflector part in a sixth embodiment. FIG. 10 is a schematic plan view of a backlight device in a seventh embodiment. It is a graph explaining the brightness | luminance distribution of the surface of the backlight apparatus based on a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel, 2 Liquid crystal layer, 3a, 3b board | substrate, 4a, 4b Polarizing plate, 5 Optical sheet, 6, 7 Brightness increase film, 8 Diffuser plate, 10 LED, 11, 14 Light guide plate, 11a, 14a Incident surface, 11b, 14b Outgoing surface, 14c Concave lens part, 13 Reflecting plate, 21-25 Reflector, 23a, 25a Reflecting surface, 31, 32 Scattering body, 33-35 Diffraction grating, 33a, 34a, 35a Uneven surface, 41-46 Back Light device, 61-75 arrow, 81 normal.

Claims (10)

A light guide plate including an entrance surface and an exit surface formed so as to be substantially parallel to each other;
A plurality of light sources for supplying light into the light guide plate;
An optical path changing means for changing the traveling direction of the light;
Light emitting means formed so as to emit the light traveling inside the light guide plate,
The light guide plate is formed in a plate shape,
The optical path changing means is configured so that a part of the light supplied to the inside of the light guide plate travels inside the light guide plate while being reflected by at least one of the incident surface and the exit surface. Formed to change the direction of light travel,
The light emitting means is formed to emit at least part of the light traveling inside the light guide plate from the emission surface ,
The optical path changing means includes a diffraction grating,
The light guide plate is formed such that the entrance surface and the exit surface are substantially parallel to each other,
The diffraction grating includes a diffraction surface for diffracting the light,
The diffractive surface is formed with an uneven cross-sectional shape,
The unevenness is formed such that the pitch of the central part is narrower than the pitch of the peripheral part,
The unevenness is formed such that the light diffracted at the central portion and the light diffracted at the peripheral portion are directed in substantially the same direction,
The unevenness is a light emitting device formed so that the diffracted light is totally reflected on the exit surface and the entrance surface .   The light emitting device according to claim 1, wherein the optical path changing unit is disposed on the incident surface.   The light-emitting device according to claim 1, wherein the optical path changing unit is disposed on the emission surface. The diffraction grating includes a diffraction surface for diffracting the light,
The light-emitting device according to claim 1 , wherein the diffractive surface has an uneven cross-sectional shape. Said light emitting means, the is formed on the light path changing means and the coplanar light emitting apparatus according to any one of claims 1 to 4. The light emitting means includes a reflector disposed on the incident surface,
The reflector is formed in a cone shape,
When the incident angle with respect to the normal of the exit surface or the normal of the entrance surface when the light traveling through the light guide plate is incident on the exit surface and the entrance surface is α °, The light emitting device according to claim 1 , wherein the light emitting device is formed so that an apex angle is approximately (180−α) °. The light emitting means includes a reflector disposed on the incident surface,
The reflector is formed in a band shape when viewed in plan,
The reflector is formed concentrically around the light source when viewed in plan,
The reflector has a reflecting surface that is formed to be inclined with respect to the incident surface and reflects the light traveling inside the light guide plate;
The reflector, when the light traveling through the light guide plate is incident on the exit surface or the entrance surface, the normal of the exit surface or the incident angle with respect to the normal of the entrance surface is α °, The light-emitting device according to claim 1 , wherein an angle formed by the incident surface and the reflecting surface is substantially (α / 2) °. The light emitting means includes a reflector disposed on the incident surface,
The light emitting device according to claim 1, wherein the reflector is formed to have a scattering effect. A plurality of the light emitting means are arranged between the plurality of light sources,
2. The light emitting device according to claim 1, wherein the light emitting means is arranged so that the number density gradually decreases from a substantially middle point of a line segment connecting the light sources toward the light source. A light emitting device according to any one of claims 1 to 9 ,
A liquid crystal display device comprising: a liquid crystal display panel arranged so that light emitted from the light emitting device is incident thereon.

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