JP2005100837A - Surface light source device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device in which light source colors are effectively mixed and brightness distribution on a light-emitting face can be homogenized. <P>SOLUTION: In the surface-formed light source device 101 provided with a plurality of point state light sources 108 installed on a reflecting face 104 and a diffusing plate 103 installed on the opposite side of the reflecting face 104, a reflecting face 105 to reflect light emitted from the point state light source 108 to the reflecting face side is installed between the diffusing plate 103 and the point state light source 108. By having this constitution, the lightsource colors repeat diffusing reflections in the space between the reflecting plate 105 and the reflecting face 104, the colors are effectively mixed, and the brightness distribution on the light-emitting face can be homogenized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a planar light source device and a display device, and more particularly, to a planar light source device and a display device capable of effectively controlling light source color mixing and luminance uniformity.

  As an image display device for personal computers and other various monitors, a liquid crystal display device is widely used. The liquid crystal display device typically includes a liquid crystal display panel and a backlight unit disposed on the back surface thereof. The liquid crystal display panel displays an image by controlling the transmitted light. One of several types of liquid crystal display devices has a direct type backlight unit. In this case, in order to improve the luminance of the liquid crystal display device, a light source is arranged directly below the display surface. As a light source of the direct type backlight unit, a cold cathode tube and a light emitting diode (LED) are known.

  Light emitting diodes are excellent in color characteristics as compared to cold cathode fluorescent lamps, and have favorable characteristics as light sources, and thus are increasingly used as light sources for backlight units. When a light emitting diode is used as a light source, a plurality of LED chips that emit different colors may be used. Typically, LED chips that emit light of three colors of red (R), green (G), and blue (B) are prepared, and the desired emission color is adjusted by adjusting the emission intensity of each color. A light source device having the same can be obtained. When used as a backlight unit of a liquid crystal display device, the light emission intensity of these LED chips is controlled so that white light is obtained. When using light emitting diodes that emit light of different colors, it is necessary to mix the light from each light emitting diode in order to obtain light of a desired color.

  The LED chip functions as a point light source and is a highly directional light source. Therefore, it is difficult to mix the light from the light emitting diodes, and several means are known as the means. As one typical method, a light source device in which a plurality of point light sources such as red, green, and blue light emitting diodes are mounted on a substrate or the like is disposed immediately below a diffusion plate for diffusing light, and its surroundings. Is configured to cover with a reflector. Here, the direct light from the light source device and the reflected light from the reflector are diffused by the diffusion plate, thereby mixing the light into white light and emitting the planar emission light from the emission surface.

  However, when emitting mixed-color outgoing light, a plurality of lights emitted from a plurality of point light sources corresponding to each color are emitted from the emission surface before color mixing, so it is difficult to mix colors and color unevenness occurs. Arise. Further, when the light guide plate is not used in the direct type backlight unit, as described above, the light from the light emitting diode is directly emitted from the light source or once reflected by the reflection plate and then enters the diffusion plate. At this time, only the vicinity of the light source shines due to the directivity of the light emitting diode, resulting in luminance unevenness called a hot spot. In order to eliminate unevenness in luminance, means for uniformly emitting light from the light emitting diodes to the liquid crystal panel includes (1) a method of diffusing the light from the light source by thickening the diffusion plate, and (2) ND (Neutral Density). A method of absorbing light in the vicinity of the light source with a filter or the like; (3) a method of controlling light output from the light source by changing the reflectance / transmittance of the half mirror (Patent Document 1); and (4) a light source of a diffusion plate. There is known a method of applying or printing a reflection diffusing material on a portion of the side surface that is strongly irradiated with light from a light source. However, if the diffuser plate is thickened to eliminate uneven brightness, light absorption at the diffuser plate increases and the luminance decreases. Further, when an ND filter, a half mirror, or a reflection diffusing material is used, the luminance is sacrificed.

By the way, conventionally, in the backlight unit, a support pin for preventing the diffusion plate from being bent may be provided on the frame. Such deflection of the diffusion plate occurs when an impact is applied to the liquid crystal display device, and the diffusion plate may break. Further, the deflection is likely to occur as the diffuser plate becomes larger, which causes uneven brightness. In order to correct such deflection, the support pin is provided with a diffusion plate on the frame, and makes the diffusion plate flat.
Japanese Patent Application Laid-Open No. 6-265885

  The present invention has been made in view of the above-described prior art, and one object of the present invention is a planar light source device that can effectively mix light source colors and uniformize the luminance distribution on the light exit surface. And providing a display device.

  A first planar light source device according to the present invention includes a plurality of point light sources provided on a reflection surface, and a diffusion plate provided on a side facing the reflection surface with the point light source interposed therebetween. A reflection plate that reflects light emitted from the point light source toward the reflection surface is provided between the diffusion plate and the point light source. With this configuration, the light source color is diffusely reflected and repeatedly mixed in a space (hereinafter referred to as “reflecting plate region”) where light from the light source is reflected between the reflecting plate and the reflecting surface. Further, it is possible to correct the deflection of the diffuser at the upper part of the reflector, and to make the luminance distribution on the light exit surface uniform.

In the first planar light source device, the reflector diffuses and reflects the light emitted from the point light source toward the reflector. With this structure, the light source colors can be effectively mixed in the reflector region.
The said 1st planar light source device WHEREIN: The said reflecting plate is spaced apart from the said reflecting surface, and is provided with the clearance gap part for projecting light to the exterior of a reflecting plate in the side part. By having this structure, diffused reflection is repeated in the reflector region, and the mixed white light is emitted outside the reflector region, and the luminance distribution outside the reflector region can be made uniform.
In the first planar light source device, the reflecting plate reflects light on the surface facing the diffusion plate. With this structure, the white light emitted from the reflection plate region can be regularly reflected by the reflection layer and directed toward the diffusion plate. Thereby, it is possible to prevent the luminance from being lowered due to the shadow of the reflecting plate portion, and to uniform the luminance distribution on the light exit surface.
In the first planar light source device, the reflection plate includes a diffusion plate support portion on a surface facing the diffusion plate side. With this structure, it is possible to correct the deflection of the diffusing plate at the diffusing plate supporting portion and make the luminance distribution on the light exit surface uniform.

In the first planar light source device, the reflecting plate has a support, and the support is fitted in a hole provided in the reflection surface and a frame provided under the reflection surface. With this configuration, the reflecting surface and the frame can be fixed.
In the first planar light source device, the point light source is a light emitting diode. The light emitting diode has an advantage that the color reproduction range is wide and the color can be adjusted as compared with the cold cathode tube.
Furthermore, a first display device according to the present invention is provided on the light emitting surface side of the planar light source device and the planar light source device, and controls transmission of light from the planar light source device. A display panel for performing display. By having this configuration, the light source colors can be mixed effectively, the luminance distribution on the light exit surface can be made uniform, and the visibility of the display information can be improved.

  The present invention can provide a planar light source device and a display device that can effectively mix light source colors and make the luminance distribution on the light exit surface uniform.

  Embodiments to which the present invention can be applied will be described below. The following description is to describe the embodiment of the present invention, and the scope of the present invention is not limited to the following form. A person skilled in the art can make necessary or possible changes, conversions, additions or omissions to the following embodiments within the scope of the present invention. In addition, the following description is simplified or modified as appropriate from the actual configuration and dimensions in order to clarify the explanation.

Embodiment 1 of the Invention
A planar light source device and a liquid crystal display device according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view for explaining the entire configuration of a liquid crystal module according to an embodiment of the present invention. FIG. 1 shows an outline of a liquid crystal module 100 having a direct type backlight unit. In FIG. 1, 101 is a direct type backlight unit, and 102 is a liquid crystal display panel to which a drive circuit (not shown) is attached. Reference numeral 103 denotes a diffusion plate that makes the luminance of the display surface uniform by diffusing transmitted light. The diffusion plate 103 is made of milky white resin, and has a thickness of about 2 mm, for example. Reference numeral 104 denotes a reflecting surface that reflects incident light. Reference numeral 105 denotes a reflection plate that repeatedly diffuses and reflects the light source color between the reflection plate and the reflection surface to effectively mix colors. 106 is a diffusion plate support for correcting the deflection of the diffusion plate. Reference numeral 107 denotes a support for giving a gap to the reflecting plate.

Reference numeral 108 denotes a light source. As the light source, a point light source is usually used, and a light emitting diode is typically used. The light source 108 is not limited to a light emitting diode, and various light sources that emit light of different wavelengths can be used. For example, organic EL (Electro Luminescence), inorganic EL, etc. can be utilized. The liquid crystal display panel 102, the reflection plate 105, and other optical members are housed in a frame 109, and are held and protected from the outside by a bezel disposed on the upper surface of the display panel.
The direct type backlight unit 101 includes a diffusion plate 103, a reflection surface 104, a reflection plate 105, a light source 106, and a frame 109.
The reflective surface 104 can be configured by foaming a resin base material or by forming a metal reflective layer such as silver (Ag) or aluminum (Al) on a resin base material sheet. In addition to the metal reflection layer formed of Ag, Al, or the like, a multilayer film using a polyester resin or a reflection layer using a liquid crystal material can be used. In addition to these, it is also possible to use a white reflecting surface. The frame 109 is made of metal or resin, and can be formed integrally with the reflecting surface 104.

  The liquid crystal display panel 102 has a display area composed of a plurality of pixels arranged in a matrix and a frame area that is an outer peripheral area thereof. The liquid crystal display panel 102 has an array substrate on which an array circuit is formed and a counter substrate, and liquid crystal is sealed between the two substrates. The color liquid crystal display device has an RGB color filter layer on a counter substrate. Each pixel in the display area of the liquid crystal display panel 102 performs RGB color display. Of course, a black and white display displays either white or black. In the display area on the array substrate, a plurality of signal lines and gate lines are arranged in a matrix. The signal line and the gate line are arranged so as to overlap each other at a substantially right angle.

Each pixel selected by a gate voltage input from a gate driver IC (not shown) applies an electric field to the liquid crystal based on a display signal voltage input from the source driver IC. A voltage input from the source driver IC is sent to the pixel electrode via the source / drain of the TFT, and the pixel electrode and the common electrode apply an electric field to the liquid crystal. By changing this voltage, the voltage applied to the liquid crystal can be changed, and the light transmittance of the liquid crystal is controlled. A circuit for applying a common potential to the common electrode is configured on a control circuit board (not shown). As the liquid crystal display panel, in addition to the above active matrix type, a simple matrix type having no switching element is known. The present invention can be applied to various types of liquid crystal display panels. Alternatively, the light from the planar light source device can be applied to various display devices that are controlled by the display panel.
The optical operation of the direct type backlight unit 101 will be described. The light of the three colors R, G, and B emitted from the light source 108 is diffused and reflected on the reflecting surface side surface of the reflecting plate 105. Further, the diffused and reflected light is reflected from the reflecting surface 104, and a part of the light passes between the adjacent reflecting plates 105 and enters the diffusing plate 103. Another part is diffused and reflected again on the surface of the reflecting plate 105 on the reflecting surface side. In this way, the light repeatedly diffused and reflected between the reflecting surface side surface of the reflecting plate 105 and the reflecting surface 104 is mixed and becomes white light. Such white light also enters the diffusion plate 103. The light that has entered the diffusion plate 103 is further diffused so that the luminance of the display surface becomes uniform, is emitted from the light emission surface of the diffusion plate 103, and enters the liquid crystal display panel 102.

FIG. 2 is a plan view, a cross-sectional view taken along line AA, and a cross-sectional view taken along line BB, illustrating a schematic configuration of the light source device according to the present embodiment. In FIG. 2, the same reference numerals as those used in FIG. 1 denote the same elements, and descriptions thereof are omitted.
In the embodiment of the present invention, an example in which a light emitting diode is used as a light source will be described. The direct type backlight unit 101 includes a plurality of LED chips that emit light of different wavelengths as the light source 108. Typically, three types of LED chips of red (R), green (G), and blue (B) are mounted. For the LED chips of each color, an appropriate number and arrangement are selected so that light having the required chromaticity and luminance is emitted from the light source device. The types of light-emitting diodes to be mounted are not limited to the three colors RGB, and multiple types of LED chips of other colors can be used.

  In addition to LED chips that emit light of three different wavelengths, LED chips that emit light of two or more types of different wavelengths can be used. Since light having many chromaticities can be emitted, the light source device preferably has light sources of three or more colors. Moreover, it is preferable to have a light source of three colors from the viewpoint of controllability and the number of parts. The light source device of the display device preferably includes a three-color light source capable of forming white light or a three-color integrated white light source.

In the embodiment of the present invention, three color LED chips of red (R), green (G), and blue (B) are used. As shown in FIG. The two reflectors 105 are disposed below. This is because the three color LED chips are arranged close to each other to effectively mix the light source colors. Further, the three color LED chips are arranged in a state of being covered by one reflector 105. This is because when the LED chip is out of the reflector region, light directly enters the diffuser plate 103 from the portion of the LED chip that exits from the reflector region, causing uneven color. Further, the three-color LED chips are arranged at an angle of 120 degrees evenly in the circumferential direction under one reflector 105. This is for effectively mixing the light source colors to prevent color unevenness and making the luminance distribution on the light exit surface uniform. The diameter of the LED chip is usually 1 to 10 mm. When a white light emitting diode is used as the LED chip, one or more may be installed under one reflector 105.
In the embodiment of the present invention, for example, assuming that the size of the liquid crystal display panel 102 is 15 inches, a total of 20 reflecting plates 105 are arranged on the reflecting surface 104 in five rows and four rows. ing. The individual reflectors 105 in each row may be linear as shown in FIG. 2 or may be arranged in a zigzag manner.

A light source device according to an embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a perspective view, a top view, and a cross-sectional view of a reflection plate provided with a diffusion plate support portion and a support column. In FIG. 3, the same reference numerals as those used in FIG. 1 denote the same elements, and the description thereof is omitted. Reference numeral 301 denotes a reflector region, and 302 denotes a gap. A reflecting plate region 301 indicated by a hatched portion in FIG. 3 indicates a space between the reflecting plate and the reflecting surface. A light source 108 is disposed in the reflector region. Here, the light source color in the reflector region is repeatedly diffusely reflected and can be mixed effectively.

In the embodiment of the present invention, the reflector 105 is a hemisphere, and the diameter thereof is, for example, about 20 mm to 30 mm. The shape of the reflection plate 105 may not be a hemisphere, but may be, for example, a hemisphere, a rectangular parallelepiped, a cube, a triangular pyramid, a quadrangular pyramid, a cylinder, a cone, or the like, and the surface facing the diffusion plate 103 is flat. A rounded one is better. The size of the reflecting plate 105 is not particularly limited as long as the light source can be covered.
The gap 302 is provided in order to emit mixed color light outside the reflector region. In this embodiment, the gap 302 is provided by supporting the reflecting plate 105 with the support column 107. The outer periphery of the reflecting plate 105 at this time may be positioned, for example, about 3 mm to 5 mm higher than the light emitting diode apex.

A seal made of aluminum or the like is attached to the entire surface of the reflection plate 105 on the surface of the reflection plate 105 facing the diffusion plate 103 side. With this seal, the light that has entered the upper part of the reflecting plate 105 is regularly reflected by the diffusing plate 103, so that a decrease in luminance due to the shadow of the reflecting plate 105 formed on the upper part of the reflecting plate 105 can be prevented. The seal may be attached to a part of the surface of the reflection plate 105 facing the diffusion plate 103. In addition to reflecting the light incident on the surface of the reflector 105 to the diffuser 103, a pattern shape is directly set on the mold facing the diffuser 103 of the reflector 105 when the reflector is molded. Alternatively, there is a processing method such as post-processing such as blast processing.
The surface facing the reflection surface 104 side of the reflection plate 105 is subjected to a treatment for diffusion / reflection. By this diffuse reflection process, the light source color can be effectively diffused and mixed. As a method of the diffuse reflection treatment, a method of attaching a diffuse reflection material to the surface of the reflection plate 105 facing the reflection surface 104 side is preferable. Or at the time of shaping | molding a reflecting plate, a pattern shape can be directly set to the metal mold | die facing the reflective surface 104 side of the reflecting plate 105, or it can process by post-processing, such as a blast process.

  A conical diffuser support 106 is installed on the upper part of the reflector 105. The diffusion plate support 106 can correct the deflection of the diffusion plate 103 and make the luminance distribution on the light exit surface uniform. Further, damage to the diffusion plate 103 can be prevented. When the diffusing plate 103 is kept flat, the diffusing plate 103 and the tip of the diffusing plate support 106 are not in contact with each other and a gap is opened. When the diffusing plate 103 is bent, the diffusing plate support 106 comes into contact with and supports the diffusing plate 103. The shape of the diffusing plate support 106 is not limited to a conical shape, and may be a conical shape, a circular column shape, a triangular pyramid shape, a quadrangular pyramid shape, a quadrangular prism shape, or the like. A narrower tip such as a cone is preferable because light that travels to the diffusion plate 103 easily enters. The tip of the diffusion plate support 106 may be sharp, rounded, or missing.

In the embodiment of the present invention, the total height including the reflector 105, the diffuser support 106 and the support column 107 is, for example, about 20 mm to 50 mm. In the case of a direct type backlight using a cold cathode tube as a light source, the distance between the lamp and the frame is about 15 mm, and the distance between the reflecting surface and the diffusion plate is about 40 mm to 50 mm. If the distance between the reflecting surface and the diffusing plate becomes narrow, there will be inconveniences such as the lamp not turning on. On the other hand, when a light emitting diode is used as the light source, the amount of leakage is small, and the distance between the reflecting surface 104 and the diffusion plate 103 can be narrowed to make the direct type backlight unit 101 thinner.
In the embodiment of the present invention, the support column 107 is fitted into a hole provided in the reflection surface 104 and the frame 109, and serves as fixing of the reflection surface 104 and the frame 109. The fixed portion may be welded to the support column 107 on the inner surface side of the hole of the frame 109 or may be bonded with an adhesive. In addition, the reflecting plate 105 is fixed by being attached to the reflecting surface 104.

In the embodiment of the present invention, the material of the reflector 105 is white polycarbonate. Examples of other materials include acrylic resin and polyethylene terephthalate.
Although the manufacturing method of a reflecting plate is not specifically limited, When the reflecting plate 105 has the diffusion plate support part 106 and the support | pillar 107, the whole is manufactured by integral injection molding. Thereby, the number of parts can be reduced.
The light source uses a light emitting diode 108 of three colors of R, G, and B. The light emitting diodes of the respective colors are arranged at 120 ° intervals evenly in the circumferential direction within the reflector region of one reflector 105. The size of one LED chip is, for example, 1 mm to 10 mm.

Embodiment 2 of the Invention
A planar light source device according to an embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a perspective view, a top view, and a cross-sectional view of a reflection plate having the function of the diffusion plate support portion. The planar light source device of FIG. 4 differs from the planar light source device of FIG. 3 in the shape of the reflector and the light source used. In FIG. 4, the same reference numerals as those used in FIG. 1 denote the same elements, and a description thereof is omitted.
The reflecting plate 105 according to the present embodiment has an alphabet “r” in the shape of its cross section, and the portion protruding laterally acts as the reflecting plate 105. In addition, the laterally projecting portion functions as the diffusion plate support portion 106. That is, it is possible to support the diffusing plate 103 that is bent by a surface that faces the side of the diffusing plate 103 that protrudes sideways.
The light emitting diode 108 used in the present embodiment is a white light emitting diode. When white diodes are used in this way, one or more may be installed under one reflector. The white light emitting diodes do not need to be mixed in color, but in order to eliminate uneven brightness due to strong directivity, light is diffusely reflected by the reflector 105 and the brightness distribution on the light exit surface is made uniform.

Embodiment 3 of the Invention
A planar light source device according to an embodiment of the present invention will be described with reference to FIGS. The planar light source device described in FIGS. 5 and 6 is different from the planar light source device of FIG. 3 in the gap portion of the reflector and the diffusion plate support.
FIG. 5 is a perspective view of the reflector 105 provided with a hole as the gap 501. In FIG. 5, the same reference numerals as those used in FIG. 1 denote the same elements, and the description thereof is omitted. By the gap portion 501 provided by making a hole in the side surface of the reflecting plate 105, light mixed in the reflecting plate region can come out of the reflecting plate region. At this time, the shape, number, etc. of the gap portion 501 are not particularly limited. In the embodiment of the present invention, the diffusion plate support 106 is not provided. Instead, by using a hemisphere as the structure of the reflector 105, the vertex of the hemisphere can serve as the diffuser support 106. That is, when a deflection occurs in the diffusion plate 103, the deflection can be supported by the apex of the hemisphere.

  FIG. 6 is a perspective view of a reflection plate in which a reflection process is performed on the surface on the diffusion plate side. In FIG. 6, the same reference numerals as those used in FIG. 1 denote the same elements, and the description thereof is omitted. A hatched portion 601 is a portion subjected to a reflection treatment, and a circular aluminum seal or the like is attached as the reflection treatment. In addition, the dotted line part in drawing is the clearance gap 501 and means the case where the reflecting plate 105 has the clearance gap 501 further.

As described above, the embodiment of the present invention effectively mixes colors by repeatedly diffusing and reflecting the light source color between the reflecting plate and the reflecting surface, and emits white light from the reflecting plate region. Light can be reflected on the diffuser by reflection on the reflector, and the luminance distribution outside the reflector region can be made uniform.
The present invention is not limited to the embodiment described above, and can be applied to various light source devices. Moreover, it is not limited to the light source device of a display apparatus, It can apply to the light source device of various uses.
Note that the reflecting plate in the above example does not need to completely reflect the light from the light source, and may be configured to transmit and absorb part of the light.

It is sectional drawing which shows schematic structure of the liquid crystal display device which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the light source device which concerns on 1st Embodiment. It is the perspective view and sectional drawing of the reflecting plate which concern on 1st Embodiment. It is the perspective view and sectional drawing of the reflecting plate which concern on 2nd Embodiment. It is a perspective view of the reflecting plate which concerns on 3rd Embodiment. It is a perspective view of the reflecting plate which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Liquid crystal module 101 Direct type backlight unit 102 Liquid crystal display panel 103 Diffusing plate 104 Reflecting surface 105 Reflecting plate 106 Diffusing plate support part 107 Support | pillar 108 Point-shaped light source 109 Frame 301 Reflecting plate area 302 Gap part 501 Gap part 601 Reflection processing Part

Claims (8)

A planar light source device comprising a plurality of point light sources provided on a reflective surface, and a diffuser plate provided on a side facing the reflective surface across the point light source,
A planar light source device in which a reflection plate that reflects light emitted from the point light source toward the reflection surface is provided between the diffusion plate and the point light source.   The planar light source device according to claim 1, wherein the reflection plate diffusely reflects light emitted from the point light source toward the reflection surface.   The planar light source device according to claim 1, wherein the reflection plate is disposed apart from the reflection surface, and has a gap portion for projecting light to the outside of the reflection plate on a side portion thereof. The planar light source device according to claim 1, wherein the reflection plate reflects light on a surface facing the diffusion plate.   The planar light source device according to claim 1, wherein the reflection plate includes a diffusion plate support portion on a surface facing the diffusion plate side.   The said reflecting plate has a support | pillar, and this support | pillar is engage | inserted in the hole provided in the flame | frame provided in the said reflective surface and the said reflective surface. A surface light source device according to claim 1.   The planar light source device according to claim 1, wherein the point light source is a light emitting diode. A planar light source device according to any one of claims 1 to 7,
A display device, comprising: a display panel that is provided on a light emission surface side of the planar light source device and that performs display by controlling transmission of light from the planar light source device.

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