JP2007227286A - Lighting device and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a downright type lighting device made thinner, with less unevenness in the luminance. <P>SOLUTION: A downright type backlight module 101 is provided with a light guide plate 7, with through-holes 8 opened at a given position surrounded by light-incident faces 5 crossing a horizontal face, light sources 1 arranged on a substrate 2 so as to be positioned inside each through-hole 8, and reflecting members 6 arranged so as to face each light source 1 for reflecting the light emitted from it. The light is reflected at the reflecting members, travels laterally through the incident faces 5 and is irradiated from the light guide plate 7 toward an LCD 102 as a planar light flux, with high uniformity. The planar light, with little luminance unevenness thus obtained, enables formation of the downright-type backlight module 101. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface-emitting illumination device used for a non-self-luminous display device or the like, and more particularly to a direct illumination device capable of handling a wide light-emitting area, and more specifically, forming the illumination device thinner. And relates to a technique for making light emission more uniform.

  A backlight module that supplies light to a liquid crystal display panel (hereinafter referred to as “LCD”), which is a non-self-luminous display element, is arranged directly below the sidelight type display element and the display element that are arranged next to the light guide plate. It can be roughly divided into direct type. The direct type backlight module is mainly used for supplying light to an LCD having a relatively wide screen (for example, one used for a television device, a display of a personal computer, or the like) (for example, a patent document). 1).

  FIG. 14 shows the structure of a conventional direct type backlight module. As illustrated, a plurality of light sources 1 (light emitting diodes that emit white light) are mounted on a substrate 2 in a predetermined arrangement. Then, the substrate 2 is disposed on the bottom of the mortar-shaped casing 3, and the upper opening of the casing 3 is sealed with the diffusion plate 4. Here, the inner surface of the housing 3 is all a mirror surface. When the light source 1 emits light, light is irradiated in all directions as indicated by arrows in FIG. And reaches the diffusion plate 4. The diffuser plate 4 diffuses light in various directions, and the light is supplied to the LCD positioned above FIG. 14 (see, for example, Patent Document 2).

  However, according to such a configuration, most of the light emitted from the light source 1 is directly irradiated onto the diffusion plate 4. Therefore, as shown in FIG. 15A, when only a single light source 1 is present, only the portion directly above the light source 1 is remarkably bright and the surroundings gradually become dark, resulting in luminance unevenness. As shown in FIG. 15B, if a plurality of light sources 1 are provided, the luminance unevenness between the light sources 1 can be slightly corrected, but the luminance unevenness cannot be improved outside the light source 1.

  In addition, the luminance of light emitted from a light emitting diode typically used as the light source 1 has a sharp directivity and the highest luminance is obtained on the central axis. The brightness decreases. For example, if it is shifted by 60 degrees from the central axis, the luminance falls below 40% of the luminance on the central axis (see, for example, Patent Document 3).

According to the prior art, in order to eliminate luminance unevenness, the depth of the housing 3 must be secured to some extent (usually about 5 cm) or more. Therefore, there is a problem that it is difficult to apply to a thin television device or a display of a personal computer. In addition, there is a problem that the area that can be illuminated by one light source is small and the number of light sources tends to increase. In addition, as shown in FIG. 15 (c), the light emitted from the light source 1 to the diffusion plate 4 (see the arrow) is refracted twice from its original direction indicated by the dashed-dotted arrow (the two refraction points are Both are on the surface of the diffusing plate 4), and are emitted from the inner side of the original irradiation line to the LCD side. Originally, in order for the diffusing plate 4 to diffuse light, the light reaching the diffusing plate 4 must be emitted from the outside of the direction. However, according to the prior art, the opposite is true, and there is a problem that the light diffusion effect by the diffusion plate 4 is low.
Japanese Patent Laying-Open No. 2005-284283 (FIGS. 2 and 3) JP 2003-272406 A Japanese Patent Laying-Open No. 2005-18997 (FIG. 8)

  Therefore, an object of the present invention is to provide a direct type backlight module that can be formed thinner and has less luminance unevenness.

  A direct type backlight module according to the present invention includes a light guide plate in which a storage space surrounded by a light incident surface intersecting a horizontal plane is opened at a predetermined position, a light source disposed so as to be positioned in the storage space, A reflective member that is disposed so as to face the light source and reflects at least part of the light emitted from the light source.

  According to the direct type backlight module of the present invention, the light emitted from the light source is reflected by the reflecting member, proceeds laterally through the light incident surface, and is guided into the light guide plate. Further, this light is refracted at various angles in the light guide plate, and eventually, it is emitted from the light guide plate into a planar and highly uniform light bundle toward the LCD. Here, since this phenomenon is not significantly affected by the thickness of the light guide plate, the direct-type backlight module can be made thin, and even if this is done, luminance unevenness hardly occurs. In the prior art, the thickness has to be about 5 cm, but according to the present invention, it can be made thinner (for example, about 1 cm).

  A direct illumination device of the present invention includes a light guide plate in which a storage space surrounded by a light incident surface intersecting a horizontal plane is opened at a predetermined position, a light source disposed so as to be positioned in the storage space, and a light source And a reflecting member that reflects at least part of the light emitted from the light source. In addition, a substrate carrying a light source was provided. In this way, not only can the light source be reliably supported, but the substrate can be used as a reflecting surface and the light emitted from the light source can be efficiently directed to the LCD. The storage space is configured to penetrate the light guide plate in the thickness direction. In this way, the light guide plate can be easily processed, and the thickness of the light guide plate can be effectively utilized to increase the light incident surface. Furthermore, the light incident surface of the storage space was made parallel to the thickness direction of the light guide plate. In this way, the storage space can be easily formed.

  Furthermore, the light incident surface of the storage space was inclined with respect to the thickness direction of the light guide plate so as to spread as it moved away from the light source. In this way, light can be guided more laterally into the light guide plate, and a planar light bundle can be easily formed. Further, the reflecting member is formed so that the center side of the light source is thick and becomes thinner as the distance from the center of the light source is increased. If it carries out like this, the light reflected by the reflection member will become easy to inject into a light-guide plate, and attenuation of the light by the repetition of reflection can be suppressed. Further, a diffusion plate for diffusing light emitted from the upper surface of the light guide plate is further provided. By so doing, the light emitted from the direct type backlight module can be made more uniform by the diffusion plate.

  Furthermore, a side-surface reflecting member that reflects light emitted from the side surface of the light guide plate and returns the light into the light guide plate is provided. If it carries out like this, the light which is going to radiate | emits further from the side of a light-guide plate can be utilized without wasting. Furthermore, the process which diffuses light is given to the at least one part surface of a light-guide plate. If it carries out like this, the light radiate | emitted from a light-guide plate can be controlled by processing. Furthermore, at least a part of the surface of the light guide plate is processed so as to emit more light as the distance from the light source increases. In this way, it is possible to reinforce the emission of light at a location far from the light source and where light tends to be insufficient, and improve the uniformity of luminance. Preferably, the reflecting member transmits a part of the light emitted from the light source. The portion directly above the reflecting member tends to be locally dark, but this can be mitigated.

  In addition, the non-self-luminous display element is illuminated using the illumination device having any one of the above-described configurations. As a result, a bright display device with little uneven illuminance can be realized.

  FIG. 1 is a cross-sectional view of the direct type backlight module of the present embodiment. As shown in the figure, the direct type backlight module 101 is arranged directly below the LCD 102, and changes the light emitted from the light source 1 into a planar light with a configuration described later, and irradiates the LCD 102 with the planar light. That is, the display screen constituted by the pixels of the LCD 102 is brightly illuminated by the planar light of the direct type backlight module 101 and displayed to the user with high visibility.

  Now, the inner surface of the housing 3 constituting the backlight module 101 is a mirror surface, and the following elements are disposed inside the housing 3. That is, the surface of the substrate 2 is a reflective surface. The light source 1 (light emitting diode) is mounted and supported at a predetermined position on the substrate 2 and emits white light. The light guide plate 7 is provided with a through hole 8 surrounded by a light incident surface 5 intersecting a horizontal plane at a predetermined position. Each of the plurality of light sources 1 is disposed on the substrate 2 so as to be located in the through hole 8. The reflection member 6 is disposed so as to face the light source 1 and reflects light emitted from the light source 1. Further, the upper opening of the housing 3 is sealed by the diffusion plate 4. Reference numeral 10 denotes a diffusion unit that diffuses light passing through the light guide plate 7 to the outside.

  Various configurations that the light guide plate 7 can take will be described with reference to FIGS. FIG. 2 is an explanatory view for explaining a direct type backlight module, and FIG. 3 is a sectional view showing a light guide plate. The light guide plate 7 is preferably made of a transparent material having a high light transmittance. The light guide plate 7 preferably has a refractive index of about “1.5” when the refractive index of air is “1”. For example, acrylic, polycarbonate, ARTON (trademark), ZEONOR (trademark) and the like are suitable. The through hole 8 is an example of an enclosed space that surrounds the light source 1 by the light incident surface 5. As shown in FIG. 3A, the light incident surface 5 may have a cylindrical shape, or may have a rectangular column shape or other polygonal column shape. The cross section can be an ellipse or the like, but considering the directivity of the light source 1, it is desirable that the cross section be a point-symmetric cross section.

  Moreover, as shown in FIG.3 (b), you may form the light-incidence surface 5 in the taper shape which the upper side (side away from the light source 1) opens. This is preferable because the light from the light source 1 is directed in the lateral direction due to the incident angle. As shown in FIGS. 3C and 3D, the surrounding space does not necessarily have to penetrate the light guide plate 7. As shown in FIG. 3C, the reflecting member 6 may be placed in a recess provided in the upper part of the enclosed space of the light guide plate 7, or as shown in FIG. A well-known printing material (for example, a material containing silver) may be appropriately printed on the upper surface. The printing method may be a well-known printing method, and when the number of light sources is large, printing is convenient because it can reduce labor. 3D is more advantageous than FIG. 3C because the height of the light incident surface 5 can be increased when the light guide plate 7 having the same thickness is used. The lower end of the enclosed space may be configured to have a slightly larger diameter than the light source 1.

  Next, the reflecting member 6 will be described with reference to FIGS. 4 is a cross-sectional view showing the reflecting member, and FIG. 5 is a plan view showing the reflecting member. As shown in FIG. 5 (a), the entire surface of the reflecting member 6 may be a reflecting surface, or as shown in FIG. It may be transparent. The material of the reflecting member 6 may be a metal such as silver or aluminum, or another material that is white and has a high reflectance can be used. As shown in FIG. 5B, even if the through hole 6a is not opened, it is possible to control to partially transmit light by appropriately reducing the thickness of the reflecting member 6. When the reflection member 6 transmits a part of light, the tendency for the upper part of the reflection member 6 to become dark can be relieved. In that case, the reflectance is preferably about 60 to 70%.

  As described in the background art, the light from the light source 1 has a sharp directional characteristic having a peak at the central axis of the light source 1. Therefore, the portion of the reflecting member 6 that faces the light source 1 may be flat as shown in FIG. 4A, but for example, it may be conical as shown in FIG. As shown in c), it may be either a convex curved surface shape, but it is desirable to form it so as to be convex toward the central axis of the light source 1. In this way, most of the light emitted from the light source 1 travels almost directly upward due to the directivity characteristics, but this is immediately reflected toward the light incident surface 5 (attenuating attenuation due to repeated reflection). This is because the possibility of being guided into the light guide plate 7 through the light incident surface 5 is increased. Moreover, as shown in FIG.4 (d), when the reflective member 6 is printed and formed in the diffusion plate 4 on a process sequence, subsequent assembly becomes easy and it is still more suitable. The enclosed space can be filled with a translucent material having a refractive index between the refractive index of the light guide plate 7 and the refractive index of air.

  Next, processing on the side surface of the light guide plate 7 will be described with reference to FIG. 6 which is a perspective view showing an outline of the light guide plate of the present invention. FIG. 6 is a perspective view showing an outline of the light guide plate of the present invention. As shown in the drawing, here, all four side surfaces of the light guide plate 7 are coated with the reflection sheet 9. The reflection sheet 9 corresponds to a side reflection member. Thereby, the light which is going to be emitted laterally from the side surface of the light guide plate 7 can be returned into the light guide plate 7. The reflective sheet 9 can be made of the same material as the reflective member 6.

  FIG. 7 shows a cross section of the light guide plate of the present invention. As shown in the figure, the diffusion unit 10 (at least one of the upper surface and the bottom surface of the light guide plate 7) is subjected to processing for diffusing light. In FIG. 7A, a plurality of V-shaped grooves are formed on the upper surface of the light guide plate 7 and in the lower surface of the light guide plate 7 in FIG. In the vicinity of the V-shaped groove, light is emitted only from an inclined surface inclined in a V-shape, and the light is reflected from a horizontal portion and returns into the light guide plate 7. Whether or not the light is emitted is determined by the magnitude relationship of the incident angles. Of course, various modifications such as making the groove U-shaped are possible.

  Alternatively, as shown in FIG. 7C, when the light source 1 is on the left side (when the light travels generally to the right as indicated by an arrow), a shallow groove is formed at a location close to the light source 1 to move away from the light source 1. You may form the groove | channel which becomes deeper gradually as it goes. In this way, even if the distance from the light source is different, it is easy to make the emitted luminance uniform, which is preferable. Alternatively, as shown in FIG. 7D, grooves having the same shape are formed, but the pitch between the grooves may be reduced as the distance from the light source 1 increases. Even in this case, similarly to the above, even if the distance from the light source is different, it is preferable that the emitted luminance is easily uniformized. Furthermore, it goes without saying that the methods of FIGS. 7C and 7D may be combined. Alternatively, as shown in FIG. 7E, the grooves 10 may not be formed, and the diffusing portion 10 (at least one of the upper surface and the bottom surface) of the light guide plate 7 may be a rough surface. For rough surface processing, for example, sandblasting can be used. The rough surface pattern may be arbitrary.

  Now, when configured as described above, as shown in FIG. 2C, most of the light emitted from the light source 1 is reflected by the reflecting member 6 due to its directivity and passes through the light incident surface 5. Guided into the light guide plate 7. The light that reaches the light guide plate 7 is finally reflected upward from the diffusion portion 10 on the upper surface of the light guide plate 7 while being appropriately reflected in the light guide plate 7. As a result, as shown in FIG. 8A, the light from the light source 1 that is a point light source is changed into a planar light, and after being diffused by the diffusion plate 4, the LCD 102 is illuminated with high uniformity. Therefore, luminance unevenness of the display screen of the LCD 102 is reduced, and the thickness of the backlight module 101 can be made smaller than that of the prior art, and a direct type suitable for applications such as a thin television device or a display of a personal computer. A backlight module is obtained.

  Further, as apparent from comparing FIG. 8B with FIG. 15C, when the gap between the light guide plate 7 and the substrate 2 is absent or very small, the light guide plate 7 enters the light source 1 from the light source 1. The light reaching the light surface 5 is reflected from the light guide plate 7 and is emitted from a position farther from the light source 1 than the initial direction indicated by the one-dot chain line arrow. In other words, the degree of diffusion increases. Further, as shown in FIG. 8C, even when there is a gap between the light guide plate 7 and the substrate 2, an optical path reflected by the substrate 2 is added, but as a whole, as described above. In addition, the degree of diffusion increases. That is, also in this sense, the light travels more randomly and the luminance uniformity is improved.

  The case where the light source 1 emits white light has been described above. FIG. 9 schematically shows a cross-sectional view of the light source used in the present invention. As shown in FIG. 9A, the light source 1 has a blue light emitting element housed in a package and is surrounded by a silicon resin mixed with a yellow phosphor (YAG). As shown in FIG. 9B, a green phosphor and a red phosphor may be mixed in the silicon resin. Further, as the light source 1, a light emitting diode that emits blue light as shown in FIG. 9C can be used. In this case, a colored layer that changes blue light to white light may be provided in the middle of the optical path of blue light. The form of this colored layer will be described with reference to FIG. Specifically, when the light source 1 emits white light (FIG. 10A), a first phosphor layer 12 (yellow) is added to the light incident surface 5 as shown in FIG. 10B. Alternatively, as shown in FIG. 10C, a second phosphor layer 13 (green) and a third phosphor layer 14 (red) may be added to the light incident surface 5. Of course, the second phosphor layer 13 (green) and the third phosphor layer 14 (red) do not need to be separate layers as shown in the figure, and may be mixed together to form one layer.

  In these layers, the material systems described in the columns of “yellow phosphor”, “red phosphor”, and “green phosphor” in the following table can be used.

  Further, the positions of the layers 12 to 14 are appropriately changed. For example, the layers 12 to 14 may be provided on the upper surface of the light guide plate 7 as shown in FIG. ) As shown on the lower surface of the diffusion plate 4. Moreover, as shown to Fig.12 (a), you may provide in the lower surface of the reflection member 6, and you may provide in the upper surface of the diffusion plate 4 with the lower surface of the reflection member 6. FIG. Alternatively, it may be provided only on the upper surface of the diffusion plate 4. When the enclosed space is filled with a translucent material having a refractive index between the refractive index of the light guide plate 7 and the refractive index of air, the material portion may be colored.

  Further, as shown in FIG. 13, the prism sheet 103 may be arranged between the LCD 102 and the backlight module 101 to improve the luminance, or a diffusion sheet may be arranged in place of the prism sheet 103 to obtain uneven luminance. May not be conspicuous.

It is sectional drawing of the direct type | mold backlight module of this invention. 1A is a plan view of a direct type backlight module of the present invention, FIG. 2B is a cross-sectional view taken along line A-A ′, and FIG. It is sectional drawing of the light-guide plate of this invention. It is sectional drawing of the reflection member of this invention. It is a top view of the reflective member of this invention. It is a perspective view of the light-guide plate of this invention. It is sectional drawing of the light-guide plate of this invention. It is explanatory drawing explaining an optical path. It is sectional drawing of a light source. It is sectional drawing of the colored layer of this invention. It is sectional drawing of the colored layer of this invention. It is sectional drawing of the colored layer of this invention. It is sectional drawing of a prism sheet. It is sectional drawing of the conventional direct type | mold backlight module. It is explanatory drawing explaining the conventional direct type | mold backlight module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Board | substrate 3 Housing | casing 4 Diffusion plate 5 Light-incidence surface 6 Reflective member 7 Light guide plate 8 Through-hole 9 Reflective sheet 10 Diffusion part 12 1st fluorescent substance layer 13 2nd fluorescent substance layer 14 3rd fluorescent substance layer 101 Backlight Module 102 LCD

Claims (12)

A light guide plate in which a storage space surrounded by a light incident surface intersecting a horizontal plane is opened at a predetermined position;
A light source disposed so as to be located in the storage space;
A direct-type illumination device including a reflecting member that is disposed so as to face the light source and reflects at least part of light emitted from the light source.   The illumination device according to claim 1, further comprising a substrate that carries the light source.   The lighting device according to claim 1, wherein the storage space penetrates the light guide plate in a thickness direction.   The lighting device according to claim 3, wherein a light incident surface of the storage space is parallel to a thickness direction of the light guide plate.   The illumination device according to claim 3, wherein a light incident surface of the storage space is inclined with respect to a thickness direction of the light guide plate so as to spread as the distance from the light source increases.   The lighting device according to any one of claims 1 to 5, wherein the reflecting member is formed such that a center side of the light source is thick and becomes thinner as the distance from the center of the light source increases.   The lighting device according to claim 1, further comprising a side surface reflection member that reflects light emitted from a side surface of the light guide plate and returns the light into the light guide plate.   The illumination device according to claim 1, wherein at least a part of the surface of the light guide plate is processed to diffuse light.   The lighting device according to claim 8, wherein at least a part of the surface of the light guide plate is processed so as to emit more light as the distance from the light source increases.   The lighting device according to any one of claims 1 to 9, wherein the reflecting member has a characteristic of transmitting a part of light emitted from the light source.   The said light source emits the light of the specific color which is not white light, The colored layer which changes the said specific color light into white light in the middle of the optical path of the said specific color light is provided in any one of Claims 1-10. The lighting device according to claim 1.   A display device comprising: the illumination device having the configuration according to claim 1; and a non-self-luminous display element illuminated by the illumination device.

Images