JP4807609B2 - Direct type backlight module and liquid crystal display - Google Patents

Description

  The present invention relates to a backlight module using a point light source. In particular, the present invention relates to a direct type backlight module that can be used in a liquid crystal display device.

  FIG. 1 shows the structure of a conventional liquid crystal display device. This liquid crystal display device includes a liquid crystal panel 10 filled with a liquid crystal material between a pair of substrates, a backlight module 20 disposed on the back side of the liquid crystal panel 10, and cases 11, 12 and the like. Yes. The backlight module 20 is required to emit light uniformly over the entire surface of the liquid crystal panel 10. There are a plurality of types of the backlight module 20, and examples thereof include a direct type backlight module and an edge light type backlight module.

FIG. 2 shows a cross-sectional structure when the direct type backlight module 21 is cut at the position of line 2-2 shown in FIG. As shown in FIG. 2, the direct type backlight module 21 includes a housing 70, a reflection sheet 60 disposed on the bottom surface of the housing 70, and a light source 50 using a fluorescent tube or the like disposed below the housing 70. The diffusion layer 40 disposed on the upper surface of the housing 70 and the prism sheet 30 disposed on the diffusion layer 40 are provided.
FIG. 3 shows a cross-sectional structure when the edge light type backlight module 22 is cut at the position of line 2-2 shown in FIG. As shown in FIG. 3, the edge light type backlight module 22 includes a light guide plate 80, a light source 50 disposed on at least one side surface of the light guide plate 80, and a U-shaped reflector surrounding the light source 50. 61 is provided. The U-shaped opening of the reflector 61 is located on the side surface side of the light guide plate 80. The reflection sheet 60 is disposed below the light guide plate 80. The diffusion layer 40 is disposed above the light guide plate 60. The prism sheet 30 is disposed on the diffusion layer 40. Since the light source 50 is disposed on the side surface side of the light guide plate 80, the thickness of the liquid crystal display device can be made relatively thin.

In the direct type backlight module, light emitted from the light source is directly incident on the display range of the display panel. On the other hand, in the edge light type backlight module, the light emitted from the light source is attenuated when propagating through the light guide plate. Therefore, it can be said that the direct-type backlight module has a structure that can easily achieve higher luminance. In addition, since the direct type backlight module does not require a light guide plate, it can be said that the manufacturing cost can be easily reduced. However, the conventional direct type backlight module using a cold cathode fluorescent tube (CCFL) has the following disadvantages.
(1) Poor color saturation: Since the emission spectrum of the cold cathode fluorescent tube covers a wide range, the current color filter cannot extract pure colored light. FIG. 4 shows a spectral distribution BLU when the light of the cold cathode fluorescent tube is extracted by a color filter. FIG. 4 shows the wavelength band RCF that the red filter transmits, the wavelength band GCF that the green filter transmits, and the wavelength band BCF that the blue filter transmits. As shown in FIG. 4, even if a color filter is used, an unnecessary portion is included in the spectrum distribution BLU. The saturation is only about 72% of the color gamma defined by the NTSC (National Television Standards Committee) standard.
(2) Low responsiveness: The response time depends on the light emission principle of the light source, and the response time of the cold cathode fluorescent tube (CCFL) is at a level exceeding several milliseconds.
(3) It is susceptible to environmental temperature. The luminous efficiency of the cold cathode fluorescent tube is strongly influenced by the environmental temperature, and high luminous efficiency can be exhibited only under specific temperature conditions.
(4) Drive voltage is high: The drive voltage of the cold cathode fluorescent tube is 1000 volts or more.
(5) There is a problem from the viewpoint of environmental protection: cold cathode fluorescent tubes contain mercury.

In order to solve the above-described problem, a direct backlight module using a light emitting diode has been developed. Compared with a direct type backlight module using a cold cathode fluorescent tube, a direct type backlight module using a light emitting diode has the advantages listed below.
(1) Excellent color saturation: As shown in FIG. 5, the emission spectrum of the light emitting diode (LED in the figure) is concentrated in the red band (approximately 645 nm), the green band (approximately 525 nm), and the blue band (approximately 455 nm). Therefore, a pure color can be easily extracted with the current color filter (BLU in FIG. 5). Its saturation achieves approximately 100 percent of the color gamma as defined by the NTSC standard.
(2) Fast response: Response time is on the order of a few nanoseconds.
(3) Less susceptible to environmental temperature:
(4) The drive voltage is low. For example, the driving voltage of a red light emitting diode is about 2 to 3 volts. The driving voltage of the blue light emitting diode and the green light emitting diode is about 3 to 5 volts.
(5) Excellent from the viewpoint of environmental protection: The light-emitting diode does not contain mercury.
From the above, in the field of liquid crystal display devices, direct type backlight modules using light emitting diodes are becoming mainstream.

Since the cold cathode fluorescent tube is a line light source, in order to use a point light source such as a light emitting diode instead of the cold cathode fluorescent tube, it is necessary to develop a structure of a direct type backlight module suitable for the point light source. .
An object of the present invention is to provide a structure of a direct type backlight module suitable for a point light source.

The present invention is embodied in a direct type backlight module using a point light source. The direct type backlight module includes a plurality of point light sources, a diffusion layer that receives light from the plurality of point light sources, a reflector that re-reflects light from the point light source reflected by the diffusion layer toward the diffusion layer, and It has. The reflector is disposed between the plurality of point light sources and the diffusion layer, and has a plurality of openings corresponding to the positions of the plurality of point light sources. On the surface of the diffusion layer, a plurality of micro-reflecting parts are formed of a material that reflects light, and the area occupancy of the micro-reflecting part groups decreases from the central part close to the point light source in the radial direction. It is characterized by being.

The light emitted from the point light source passes through the opening of the reflector and reaches the diffusion layer. A part of the light that reaches the diffusion layer propagates through the diffusion layer and is irradiated to the outside, and a part of the light is reflected by the minute reflection portion of the diffusion layer. The light reflected by the minute reflection part of the diffusion layer goes to the reflector, is reflected by the reflector, and reaches the diffusion layer again. The light emitted from the point light source is diffused by repeating the reflection by the minute reflecting portion and the reflector.
In the diffusion layer, the area occupancy ratio of the micro-reflecting portion is large at a position close to the point light source and small at a position far from the point light source. That is, the ratio of reflected light is high at a position where the point light source is strongly irradiated, and the ratio of light irradiated to the outside is high at a position where the point light source is weakly irradiated. Thereby, uniform light can be irradiated from the diffusion layer, and a display area such as a liquid crystal panel can be illuminated uniformly.

As the point light source, a light emitting diode, a mercury lamp, a halogen lamp, or the like can be used.
In the diffusing layer, it is preferable that the distance between the minute reflecting portion groups is increased from the central portion close to the point light source in the radial direction. Or it is preferable that each minute reflection part is small toward the radial direction from the center part close | similar to a point light source.
At least a part of the diffusion layer may form a minute reflection portion group in which a plurality of minute reflection portions exist in a square range of 0.1 to 1.2 mm square. The micro-reflecting part group is preferably composed of a main micro-reflecting part and a plurality of sub-micro reflecting parts arranged around the main micro-reflecting part.
The minute reflecting portion may be formed on the surface of the diffusion layer on the point light source side or on the surface opposite to the point light source. Alternatively, a part of the minute reflection portion group may be formed on the surface of the point light source and the remaining portion may be formed on the surface of the anti-point light source.
The minute reflection portion may be provided so as to protrude from the surface of the diffusion layer, or may be embedded in the surface or inside of the diffusion layer. Alternatively, a part of the minute reflecting portion group may be protruded and the remaining portion may be embedded in the surface or inside of the diffusion layer.
Diffusion layer is preferably formed of glass or acrylic resin or polymethyl methacrylate or polycarbonate and Arton (registered trademark) resin or polyethylene terephthalate.
The minute reflecting portion is preferably formed of a titanium compound, a silicon compound, barium sulfate, or the like.

  By disposing the above backlight module on the back surface of the liquid crystal display panel, a liquid crystal display device in which the brightness of the display area is uniform can be realized.

The present invention is also embodied in a method for manufacturing a direct type backlight module using a point light source. In this method, a step of forming a plurality of point light sources, a step of forming a diffusion layer that receives light from the plurality of point light sources, and re-reflecting the light of the point light source reflected by the diffusion layer toward the diffusion layer Forming a reflector. In the reflector forming step, the reflector is formed between the plurality of point light sources and the diffusion layer, and a plurality of openings are formed in the reflector corresponding to the positions of the plurality of point light sources. In the step of forming the diffusion layer, the surface of the diffusion layer is interspersed with a plurality of minute reflection portions, and the area occupancy of the minute reflection portion group is decreased from the central portion close to the point light source in the radial direction. Features.
According to this manufacturing method, a backlight module that can uniformly illuminate a display area such as a liquid crystal panel can be realized.

  In the step of forming the diffusion layer, it is preferable to form the micro-reflection portion by screen printing a material that reflects light on the diffusion layer. Alternatively, it is preferable to form the micro-reflecting portion by engraving the arrangement pattern of the micro-reflecting portion on the surface of the diffusion layer and then applying a material that reflects light to the surface of the diffusion layer.

  In order to make the objectives, features, advantages, and the like of the present invention clearer and easier to understand, embodiments of the present invention will be described below in detail and will be described in detail with reference to the accompanying drawings.

(Example 1)
FIG. 6 is a schematic diagram illustrating a main configuration of the liquid crystal display device 100 including the backlight module according to the first embodiment. The liquid crystal display device 100 includes a liquid crystal panel 110 and a backlight module 120. The liquid crystal panel 110 includes a pair of substrates 112 and 114 and a liquid crystal material 116 filled between the pair of substrates 112 and 114.
The backlight module 120 is a direct type backlight module using a point light source. The backlight module 120 illuminates the display area of the liquid crystal panel 110 and is required to illuminate the display area of the liquid crystal panel 110 uniformly. The backlight module 120 includes a plurality of point light sources 150, a reflector 160, a diffusion layer 180, and a plurality of prism sheets.

A plurality of openings 162 are formed in the reflector 160. Each opening 162 is formed corresponding to the position of each point light source 150. Thereby, much of the light emitted from each point light source 150 can pass through each opening 162 of the reflector 160 and reach the diffusion layer 180. Depending on the form of the point light source 150, the position where the reflector 160 is arranged is set below the point light source 150, set above the point light source 150, or at the same height as the point light source 150. Can be set. Thereby, regardless of the form of the point light source 150, much of the light emitted from the point light source 150 can pass through the opening 162 of the reflector 160 and reach the diffusion layer 180. Note that one opening 162 may be formed for each of the plurality of point light sources 150.
A plurality of minute reflecting portions 182 are scattered on the surface of the diffusion layer 180. The minute reflecting portion 182 is formed of a reflective material that reflects light. When the light from the point light source 150 group reaches the diffusion layer 180, a part of the light is reflected by the minute reflecting portion 182 and a part of the light propagates through the diffusion layer 180. The light reflected by the minute reflector 182 travels toward the reflector 160, is reflected by the reflector 160, and reaches the diffusion layer 180 again. The light emitted from the group of point light sources 150 is diffused by repeating the above reflection, and then propagates into the diffusion layer 180. The backlight module 120 can uniformly illuminate the display area of the liquid crystal panel 110 by irradiating light uniformly from the diffusion layer 180 in the plane direction.

(Example 2)
FIG. 7 is a schematic diagram illustrating a configuration of the backlight module 220 according to the second embodiment. The backlight module 220 according to the second embodiment includes a plurality of point light sources 250, a reflector 260, and a diffusion layer 280. A plurality of openings 262 are formed in the reflector 260. A plurality of minute reflecting portions 282 are scattered on the surface of the diffusion layer 280. In the diffusing layer 280, the area occupancy of the group of minute reflecting portions 282 (area / area of the minute reflecting portions 282 group) from a position close to the point light source 250 (hereinafter sometimes referred to as a central portion) 290 in the radial direction. The area of the diffusion layer) is reduced. Specifically, the interval between the small reflecting portions 282 is increased from the position of the center portion 290 in the radial direction. In addition, each minute reflection portion 282 becomes smaller from the position of the center portion 290 toward the radial direction. That is, on the surface of the diffusion layer 280, more incident light is reflected at positions closer to each point light source 250, and more incident light propagates into the diffusion layer at positions farther from each point light source 250.

The intensity of light that the point light source 250 irradiates the diffusion layer 280 becomes stronger in the vicinity of the central part 290 that is closer to the point light source 250 and becomes weaker in the radial direction from the central part 290. The intensity of light that the point light source 250 group irradiates the diffusion layer 280 does not become uniform over the surface of the diffusion layer 280. At this time, in the diffusion layer 280 of the present embodiment, more incident light is reflected in the vicinity of the center portion 290, and more incident light is propagated in the diffusion layer 280 as the distance from the center portion 290 is increased. Thereby, the amount of light propagating in the diffusion layer 280 is uniform over the surface of the diffusion layer 280. That is, the intensity of light emitted from the diffusion layer 280 to the outside is uniform over the surface direction of the diffusion layer 280, and a display area such as a liquid crystal panel can be illuminated uniformly.
The distribution of light reflectance on the surface of the diffusion layer 280 can be adjusted by adjusting the arrangement pattern of the micro-reflecting portions 282 and the size of each micro-reflecting portion 282.
In the backlight module 220 described above, one point light source 250 is arranged with respect to one central portion 290. On the other hand, as shown in FIG. 8, it is good also as a structure which arrange | positions the several point light source 250 with respect to one center part 290. FIG.

In the backlight module 220, a light emitting diode, a mercury lamp, a halogen lamp, or the like can be used for the plurality of point light sources 250.
The minute reflecting portion 282 may be formed on the point light source side surface of the diffusion layer 280 or may be formed on the opposite point light source side surface. A part of the group of minute reflecting portions 282 may be formed on the light source side surface, and the remaining portion may be formed on the anti-point light source side surface.
The minute reflection portion 282 may protrude from the surface of the diffusion layer 280 or may be embedded. A part of the group of minute reflecting portions 282 may be protruded and the remaining portion may be embedded. Further, it can be formed inside the diffusion layer 280.
The diffusion layer 280 can be formed of a transparent or translucent material such as glass, acrylic resin, polymethyl methacrylate (PMMA), polycarbonate (PC), Arton (registered trademark) resin, or polyethylene terephthalate (PET).
The micro-reflecting portion 282 can be formed using a reflective material such as a titanium (Ti) compound, a silicon (Si) compound, or BaSO 4.

  FIG. 9A to FIG. 9F show examples of forming the minute reflection portion 282. As shown in FIG. 9A, only one minute reflection portion 282 may be formed in a predetermined unit area (for example, 0.1 to 1.2 mm square) 292. Further, as shown in FIGS. 9B and 9F, two minute reflecting portions 282 may be formed in the unit area 292. When configuring a micro-reflecting part group in which a plurality of micro-reflecting parts 282 are formed in the unit area 292, the two micro-reflecting parts 282 may be formed in contact with each other as shown in FIG. 9B. However, as shown in FIG. 9F, the two minute reflecting portions 282 may be formed apart from each other. Alternatively, as shown in FIGS. 9C, 9 </ b> D, and 9 </ b> E, a main micro-reflecting portion 282 a and a plurality of sub-micro-reflecting portions 282 arranged around the main micro-reflecting portion 282 may be formed in the unit area 292. .

FIG. 10A and FIG. 10B exemplify arrangement patterns of the minute reflecting portions 182 and 282. In the arrangement pattern illustrated in FIG. 10A, the distance between the small reflective portions 182 increases from the central portion 190 in the radial direction, and the small reflective portions 182 become smaller. Each minute reflection portion 182 is independent, and one minute reflection portion 182 is formed in the unit area 192.
In the example of FIG. 10b, a plurality of minute reflecting portions 282 are formed in the unit area 292, and a plurality of minute reflecting portion groups are formed. In this case, from the center part 290 toward the outside, the interval between the minute reflection part group groups is widened, and the largest minute reflection part (main minute reflection part) of each minute reflection part group is smaller.

  In order to form the minute reflection portion 282 in the diffusion layer 280, for example, a material that reflects light can be formed on the surface of the diffusion layer 280 by screen printing. Alternatively, it can be formed by engraving (by etching or the like) an arrangement pattern of the minute reflecting portions 282 on the surface of the diffusion layer 280 and then applying a material that reflects light to the surface of the diffusion layer 280.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The figure which shows the structure of the conventional liquid crystal display device. It is sectional drawing of the conventional direct type | mold backlight module. It is sectional drawing of the conventional edge light type backlight module. The graph which shows the emission spectrum of a direct type backlight module using a cold cathode fluorescent tube. The graph which shows the emission spectrum of the direct type backlight module using a light emitting diode. The figure which shows the structure of the liquid crystal display device of an Example. 1 is a diagram illustrating a configuration of a backlight module according to Embodiment 1. FIG. FIG. 6 is a diagram illustrating a configuration of a backlight module according to a second embodiment. The figure which illustrates a microreflection part. The figure which shows the radial arrangement | positioning pattern from which each minute reflection part is independent. The figure which shows the radial arrangement | positioning pattern in which each microreflection part comprises the group.

Explanation of symbols

10. Liquid crystal panel 11. Case 12. Case 20. Backlight module 21. Direct type backlight module 22. Edge light type backlight module 30. Prism sheet 40. Scattering layer 50. Lamp 60, 61 .. Reflector 70. Housing 80. Light guide plate 100. Liquid crystal display device 110. Liquid crystal display panel 112, 114. Substrate 116. Liquid crystal material 120, 220. Backlight modules 150, 250. ..Point light sources 160, 260..Reflectors 162, 262..Apertures 180, 280..Diffusion layers 182, 282, 282a..Slight reflection portions 190, 290..Center portions 192, 292..Unit area

Claims (21)

Multiple point sources,
A diffusion layer for receiving light from the plurality of point light sources;
A reflector that re-reflects the light of the point light source reflected by the diffusion layer toward the diffusion layer;
On the surface of the diffusion layer, a plurality of micro-reflecting parts are scattered, and the area occupancy of the micro-reflecting part group is reduced from the central part close to the point light source in the radial direction,
The reflector is disposed between the plurality of point light sources and the diffusion layer, and a plurality of openings are formed corresponding to positions of the plurality of point light sources. Type backlight module.   The direct type backlight module according to claim 1, wherein the point light source is any one of a light emitting diode, a mercury lamp, and a halogen lamp.   3. The direct type backlight module according to claim 1, wherein in the diffusion layer, the interval between the micro-reflection portions is widened from the central portion in the radial direction.   4. The direct-type backlight module according to claim 1, wherein in the diffusion layer, each minute reflection portion becomes smaller in the radial direction from the center portion. 5.   5. The micro-reflecting part group in which a plurality of micro-reflecting parts exist in a square range of 0.1 to 1.2 mm square is formed in at least a part of the diffusion layer. The direct type backlight module according to claim 1.   6. The direct type back according to claim 5, wherein the micro-reflecting part group includes a main micro-reflecting part and a plurality of sub-micro reflecting parts arranged around the main micro-reflecting part. Light module.   7. The direct type backlight module according to claim 1, wherein the minute reflecting portion is formed on a point light source side surface and / or an anti-point light source side surface of a diffusion layer. 8.   The direct type backlight module according to any one of claims 1 to 7, wherein the minute reflecting portion protrudes and / or is embedded in the surface of the diffusion layer.   The diffusion layer is formed of any one of glass, acrylic resin, polymethyl methacrylate, polycarbonate, Arton (registered trademark) resin, and polyethylene terephthalate. The direct type backlight module described.   10. The direct type backlight module according to claim 1, wherein the minute reflecting portion is formed of any one of a titanium compound, a silicon compound, and barium sulfate. A method of manufacturing a direct type backlight module using a point light source,
Forming a plurality of point light sources;
Forming a diffusion layer that receives light from the plurality of point light sources;
Forming a reflector that re-reflects the light of the point light source reflected by the diffusion layer toward the diffusion layer, and
In the step of forming the diffusion layer, the surface of the diffusion layer is interspersed with a plurality of micro-reflecting parts, and the area occupancy of the micro-reflecting part group is decreased from the central part close to the point light source in the radial direction,
In the step of forming the reflector, the reflector is formed between the plurality of point light sources and the diffusion layer, and a plurality of openings are formed in the reflector corresponding to the positions of the plurality of point light sources. A manufacturing method of a direct type backlight module characterized by the above. The method of manufacturing a direct type backlight module according to claim 11 , wherein any one of a light emitting diode, a mercury lamp, and a halogen lamp is used as the point light source. The method for manufacturing a direct type backlight module according to claim 11 or 12 , wherein, in the step of forming the diffusion layer, the interval between the minute reflecting portions is increased from the central portion in the radial direction. The direct-type backlight module according to any one of claims 11 to 13 , wherein in the step of forming the diffusion layer, the diameter of each minute reflection portion is reduced from the center portion toward the radial direction. Manufacturing method. The step of forming the diffusion layer is characterized in that at least a part of the diffusion layer is formed with a minute reflection portion group in which a plurality of minute reflection portions exist in a square range of 0.1 to 1.2 mm square. method for manufacturing a direct-type backlight module according to any one 11 to 14. The direct-type backlight according to claim 15 , wherein the micro-reflecting part group includes a main micro-reflecting part and a plurality of sub-micro reflective parts arranged around the main micro-reflecting part. Module manufacturing method. The method of manufacturing a direct type backlight module according to any one of claims 11 to 16 , wherein the minute reflecting portion is formed on a point light source side surface and / or an anti-point light source side surface of a diffusion layer. . The diffusion layer, as claimed in any one of claims 11 to 17, characterized in that formed in one of glass and acrylic resin and polymethyl methacrylate and polycarbonate and ARTON (registered trademark) resin and a polyethylene terephthalate Manufacturing method of direct type backlight module. The method for manufacturing a direct type backlight module according to any one of claims 11 to 18 , wherein the minute reflective portion is formed of any one of a titanium alloy, a silicon composite, and barium sulfate. The step of forming the diffusion layer, by screen printing a material that reflects light on the diffusion layer, direct type according to any one of claims 11 to 19, and forming a micro reflecting portion A method for manufacturing a backlight module. In the diffusion layer forming step, the micro-reflecting portion is formed by performing a step of engraving the arrangement pattern of the micro-reflecting portion on the surface of the diffusion layer and a step of applying a material that reflects light on the surface of the diffusion layer. The method for manufacturing a direct type backlight module according to any one of claims 11 to 19 , wherein:

Images