JP2010170898A - Edge light type partial drive backlight unit and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reflective efficiency by preventing crosstalk; and to lessen luminance deterioration caused by heat generation of a light source. <P>SOLUTION: Light emitted from a linear light source 11 of a first light guide plate 12 and light P<SB>a</SB>reflected by a lamp reflector 15 are emitted from a light reflecting surface 13 by being diffusely reflected with a reflective dot of an irregular reflecting surface 14, and the light P<SB>b</SB>emitted from a linear light source 21 of a second light guide plate 22 is totally reflected with a flat smooth surface of a total reflection range T<SB>b</SB>, and is emitted from a light emitting surface 23 by being diffusely reflected with a reflective dot of an irregular reflecting surface 24. The linear light sources 11, 21 of the first and second light guide plates 12, 22 prevent crosstalk by being arranged on both sides of an end 16<SB>t</SB>of a reflective sheet 16 wherein reflective treatment or shading treatment is applied to both surface sides, a base board B of the linear light sources 11, 21 is excellent on thermal diffusion since it comes in contact with the sectioned C-shaped lamp reflector 15 with good thermal conductivity, and luminance deterioration caused by heat generation of the light source is lessened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight used in a liquid crystal display device, and more particularly to an edge light type partial drive backlight unit suitable for area control and a liquid crystal display device using the same.

  In recent years, liquid crystal display devices such as a liquid crystal television and a liquid crystal display tend to be large and thin, and accordingly, thinning the backlight has become a major issue. In the case of a self-luminous display such as a PDP or an organic EL, a backlight is not necessary, but since a liquid crystal only has a filter function, a backlight is necessary for a liquid crystal display, which is one of the most important technologies. .

  In this case, the light source is placed directly on the back surface of the liquid crystal panel, and the light source is placed on the side of the liquid crystal panel, and light is spread over the entire surface of the liquid crystal panel using a light guide plate or reflector. The type is known, and there are many edge light types for small liquid crystal, notebook type and desktop personal computers and LCD monitors, and the direct type is mainly used for liquid crystal televisions.

  The direct type system described above is a system in which CCFLs (cold cathode fluorescent lamps) and LEDs are arranged below the liquid crystal, and light is sent to the liquid crystal from a surface light source on which a diffusion plate is arranged. It is easy to add and lightweight, and can implement partial drive methods such as local dimming, so it is widely used in LCD TVs, but it takes time to process the diffusion plate and improves uneven brightness. Therefore, since a certain distance is required between the light source and the diffusion plate and a predetermined thickness is required, there is a problem that it is difficult to reduce the thickness.

  On the other hand, the edge light type method is a method in which the linear light of CCFL or LED is converted into planar light using a light guide plate and sent to liquid crystal, and the light guided from the light source into the acrylic light guide plate is transmitted. Using total reflection, light is directed to the entire surface, and the light hitting the reflective dot changes its path, and the light with an angle smaller than the total reflection angle is emitted from the acrylic surface and is emitted from the entire surface of the light guide plate. This structure has the advantage of being advantageous for thinning because of its structure.

  In the above-mentioned edge light type backlight, the light incident from the acrylic end face of the light guide plate repeats total reflection on the smooth surface, but all the incident light except for the surface reflection becomes total reflection light. Since the light travels through the plate and reaches the opposite end face without being attenuated unless it hits the reflective dot, it has an advantage that the light use efficiency in the light guide plate is very high.

  However, the edge light type system uses a light guide plate as a surface light source, but there is a problem that the vicinity of the CCFL is bright, it becomes dark as it goes far from the CCFL, and it tends to cause uneven brightness. It has become.

  As a technique for solving such a problem of luminance unevenness, a flat rectangular shape having one surface as a light emitting surface, and two to four side surfaces as light incident surfaces, the thickness from all the light incident surfaces is increased. There is known a light guide plate that has a reflective surface composed of 1 to 4 inclined surfaces configured to be gradually thinner, and that can cope with non-lighting of a light emitter with high luminance (see, for example, Patent Document 1). .

  In addition, a plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, the front surface is a light emitting surface, and at least two of the four side surfaces are light incident surfaces, and the back surface is light. A light guide plate that has a light reflecting surface made of, for example, a curved surface that is formed so that the plate thickness decreases from the incident surface toward the center, is lightweight, has high luminance, and has excellent luminance uniformity with little luminance unevenness. (For example, refer to Patent Document 2).

  On the other hand, it is known that a backlight capable of partial drive display can realize high contrast and wide color reproducibility. As a backlight capable of such area control, each block is separated from each other. A plurality of light guide plates to be formed, and a plurality of LEDs arranged on the side portions of the light guide plates to allow light to enter the light guide plates of each block, and the LEDs that allow light to enter the light guide plates of each block are adjacent to each other. A backlight unit that is superposed on the light guide plate of the matching other block and is easy to achieve a partial drive method such as local dimming that is partially driven by each block and can realize clear image quality through a high contrast ratio is known. (For example, see Patent Document 3).

  In addition, two or more illumination units having a wedge shape whose thickness decreases as the distance from the end light incident surface decreases, with each illumination unit partially overlapping with the surface of one illumination unit facing the back of another illumination unit. The light source is arranged on the light incident surface of one or more illumination units, and the surface of each illumination unit forms a substantially series of opposed surfaces with respect to the light irradiation target. And the planar light source device which enabled the simplification of a structure is known (for example, refer patent document 4).

JP 2001-167622 A International Publication Number WO2004 / 081444 JP 2007-293339 A JP 2001-184929 A

  In the above-described light guide plates of Patent Documents 1 and 2, since the light guide plate is provided with two or more light incident surfaces, the incident surface enables higher luminance than the light guide plate having one surface. Even if the use for area control is considered, the number of one or both of the vertical and horizontal division planes is limited to 1 or 2, so it can be used for area control on a large screen. Not suitable.

  On the other hand, in the backlight unit of Patent Document 3 capable of area control, a partial drive system is possible using a light guide plate of the same shape, but the light guide plate of another block adjacent to the LED of the light guide plate of each block As a result of the superposition, a large number of LEDs are arranged directly under the light irradiation surface, and the thickness of the light guide plate changes abruptly in this superposition portion. There are difficulties in achieving this.

  Furthermore, the planar light source device of Patent Document 4 also enables a partial drive system using light guide plates having the same shape. However, on the back surface of each light guide plate, liquid crystal panels due to interference of light from adjacent light sources or the like are provided. In order to prevent uneven brightness, it is necessary to perform gradation processing and shading processing or light attenuation processing on a predetermined area, and a holding member is inserted into the space formed by the rear surface of each light guide plate and the rear chassis, Since it is necessary to form a rear chassis along the outline of each lighting unit, the structure is complicated, and a large number of LEDs are arranged directly under the light irradiation surface, and the entire light emission surface is covered. There are difficulties in achieving uniform brightness.

As means for solving the above problems, the present applicant, as shown in FIG. 5, uses light guide plates 42 and 52 having linear light sources 41 and 51 at the end portions as light emission surfaces of the respective light guide plates. 43, 53 is an edge light type backlight in which the linear light sources 41, 51 of the light guide plates 42, 52 are arranged in parallel so as to form substantially the same plane, and the light guide plates 42, 52 are arranged in parallel. becomes the a first light guide plate irregular reflection surface 44 on the opposing surface of the light emitting surface 43 is formed, from the first light guide plate 42 and the stacked laminate section the second light guide plate 52 having a L _a, second light guide plate 52 is composed of a laminated portion L total reflection region is formed in _a T _a and the light emitting surface 43 of the first light guide plate and diffuse reflection region D _a having a light emitting surface 53 adjacent, irregularly reflected edge forming the irregular reflection surface 54 on the opposing surface of the light emitting surface 53 of the area D _a The byte type partial driving the backlight unit 40, and filed previously (see Japanese Patent Application No. 2008-112748). In the figure, 45 and 55 are lamp reflectors, 46 and 56 are reflection sheets, and 47 and 57 are end face reflection sheets.

In this case, in the edge light type partial drive backlight unit described above, the light P ₁ emitted from the linear light source 41 of the _first light guide plate 42 enters the light guide plate from the end face of the light guide plate 42 and diffusely reflects. The light is irregularly reflected by the reflection dots on the surface 44 and is emitted from the light emitting surface 43. On the other hand, the light P ₂ emitted from the linear light source 51 of the second light guide plate 52, receiving light from the end face of the light guide plate 52 to the light guide plate in while repeating total reflection smooth surface of the total reflection region T _a, All the incident light except for the surface reflection is totally reflected light, travels in the light guide plate 52, is irregularly reflected by the reflection dots on the irregular reflection surface 54, and is emitted from the light emission surface 53.

Using the plurality of edge light type partial drive backlight units 40 described above, for example, the linear light sources of two units are arranged on both end sides, and the plurality of sets are arranged so that the light emission surfaces are on the same plane. By arranging in parallel, partial driving is possible without arranging a large number of LEDs under the liquid crystal display screen, but it has been found that there are the following problems.
That is, in the edge light type partial driving the backlight unit 40 shown in FIG. 5 above, the laminated portion L _a of the second light guide plate 52 is partially laminated with the first light guide plate 42, therefore, Since each of the linear light sources 41 and 51 is disposed at different positions in the plate direction parallel to the paper surface of FIG. 5 of the light guide plate, it has a structure that does not generate crosstalk between the two light guide plates. Since a lamp reflector made of steel is used, a highly reflective material containing silver or the like cannot be used.

In this structure, since a resin lamp reflector is used, for example, when LEXAN ^* BFL4000U Resin (trademark of SABIC Innovative Plastics) is used as a resin material, the reflectance is about 95%, so that the resin made in the LED installation area is used. When reflection is repeated three times on the lamp reflector, the reflected light decreases to about 86%. In this case, there is a method of attaching a silver reflection type reflector to the resin frame, but the number of parts and assembly man-hours increase, and one LED bar is required for each light guide plate, which also leads to an increase in the number of parts. Has the disadvantages.

  Furthermore, since the linear light sources 41 and 51 made of LEDs or the like are arranged apart from each other, there is a problem that a problem of luminance reduction due to heat generated by the linear light source also occurs.

  In the edge light type partial drive backlight unit 40 shown in FIG. 5 described above, a top view type LED is used as a linear light source, but there is a similar problem when a side view type LED is used.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly efficient edge light type partial drive backlight without increasing the number of parts.

  In addition, the present invention prevents crosstalk around the linear light source, improves the reflection efficiency of the light source, and further reduces the decrease in luminance due to heat generated by the light source. The object is to provide a light structure.

  Another object of the present invention is to arrange all the light sources at both ends of the backlight unit without arranging a large number of light sources (LEDs) immediately below the light irradiation surface, and to simplify the structure, and An object of the present invention is to provide a partial drive backlight unit that is not limited by the number of vertical and horizontal division planes for large screen area control.

  In order to achieve the above object, an edge light type partial drive backlight unit according to the present invention includes a plurality of light guide plates each having a linear light source at an end, and each light output surface of each light guide plate is substantially Are arranged adjacent to each other so as to form the same plane, and the linear light sources of the plurality of light guide plates are arranged in parallel, the backlight unit includes at least a part of the light emitting surface of the light guide plate. A first light guide plate having an irregular reflection surface formed on the opposing surface, and a second light guide plate having a laminated portion that is different from the first light guide plate and laminated with the first light guide plate via a reflection sheet. The second light guide plate includes a total reflection region formed in the laminated portion and a diffuse reflection region having a light output surface adjacent to the light output surface of the first light guide plate. At least some pairs of light exit surfaces A diffused light reflecting surface is formed on the surface, and the linear light sources of the first and second light guide plates are arranged on both sides of the end portion of the reflecting sheet, and the two linear light sources are formed with a U-shaped thermal conductivity and It is made to coat with a material having good reflectivity.

  In the edge light type partial drive backlight unit described above, the second light guide plate further includes an nth light guide plate (n ≧ 3) each having a stacked portion that is sequentially stacked via a reflective sheet. The n light guide plate is different in shape from the (n-1) light guide plate and has a total reflection area formed in a laminated portion of the (n-1) light guide plate and the (n-1) light guide plate. A diffused reflection region having a light output surface adjacent to the light output surface and forming substantially the same plane, and forming a diffused reflection surface on at least a part of the opposite surface of the light output surface of the irregular reflection region, and The linear light sources of the 1st to nth light guide plates are arranged on both sides of the end portions of the respective reflection sheets, and the n linear light sources are covered with a material having a U-shaped cross section and good thermal conductivity and reflectivity. It can also be formed.

  In addition, corresponding to a backlight unit composed of a plurality of light guide plates corresponding to a large screen, two of the above-mentioned edge light type partial drive backlight units are arranged so that the linear light sources of each light guide plate are on both ends. It is also possible to arrange the light emitting surfaces adjacent to each other so that the light emitting surfaces of the respective light guide plates form substantially the same plane. It is also possible to arrange the light emitting surfaces adjacent to each other so that the light emitting surfaces of the partial drive backlights form substantially the same plane.

  An edge light type partial drive backlight unit composed of a plurality of light guide plates corresponding to these large screens is suitable for a liquid crystal display device.

  According to the present invention, partial drive display can be easily realized by using a plurality of light guide plates having different shapes, and a highly efficient edge light type partial drive backlight can be realized without increasing the number of components. can do.

  Further, according to the present invention, it is possible to prevent the crosstalk around the linear light source, improve the reflection efficiency, and reduce the luminance decrease due to the heat generated by the light source.

  Furthermore, according to the present invention, since all the light sources are arranged on one side or both ends of the backlight unit without arranging a large number of light sources (LEDs) immediately below the light irradiation surface, the structure is simple, In addition, an edge light type partial drive backlight unit capable of two-dimensional partial drive suitable for area control of a large screen that is not limited by the number of vertical and horizontal divided surfaces can be easily realized.

FIG. 2 is a cross-sectional view (a) and a partially enlarged cross-sectional view (b) showing an embodiment of an edge light type partial drive backlight unit according to the present invention. It is a partially expanded sectional view which shows the other Example of the edge light type partial drive backlight unit by this invention. They are sectional drawing (a) which shows other Examples of the edge light type partial drive backlight unit by this invention, and sectional drawing (c) which shows one Example of a liquid crystal display device (b) using the same. 1 is a plan view of an edge light type partial drive backlight unit divided into a number of areas according to the present invention; FIG. It is sectional drawing which shows the edge light type partial drive backlight unit which concerns on the prior application of this invention.

  Hereinafter, an embodiment for carrying out the present invention will be described with reference to a plan view.

  FIG. 1A is a sectional view of an edge light type partial drive backlight unit 10 for explaining the basic principle of the present invention, and FIG. 1B is a partially enlarged sectional view thereof.

  In the same figure, 11 and 21 are linear light sources, 12 and 22 are light guide plates, 13 and 23 are light emitting surfaces, 14 and 24 are irregular reflection surfaces formed by reflective dots, 16 and 26 are reflection sheets, Reference numeral 27 denotes an end face reflection sheet.

The linear light sources 11 and 21 are arranged in parallel to the end portions of the light guide plates 12 and 22, respectively, and the light emitting surfaces 13 and 23 of the light guide plates 12 and 22 are arranged adjacent to each other so as to form substantially the same plane. Has been. An irregular reflection surface 14 is formed on at least a part, usually the entire surface, of the first light guide plate 12 facing the light exit surface 13. The second light guide plate 22 is connected to the first light guide plate 12. It is composed of a total reflection region T _b composed of the stacked laminated portions L _b and a diffuse reflection region D _b having a light output surface 23 adjacent to the light output surface 13 of the first light guide plate 12, and the light in the irregular reflection region D _b An irregular reflection surface 24 is formed on at least a part of the opposing surface of the emission surface 23, usually the entire surface.

  The linear light sources 11 and 21 of the first and second light guide plates are composed of, for example, a plurality of top view type LEDs arranged in a straight line, and these LEDs are arranged on a single substrate B. LED bar is formed.

  This LED bar is covered with a lamp reflector 15 having a U-shaped cross section, and the bottoms of the substrates B of the linear light sources 11 and 21 and the lamp reflector 15 are mounted in contact with each other. For the lamp reflector 15 having a U-shaped cross section, for example, a metal material having good thermal conductivity and reflectivity is used.

  The linear light sources 11 and 21 composed of the LEDs of the first and second light guide plates are arranged on separate substrates, and the bottoms of the substrates of the linear light sources 11 and 21 and the lamp reflector 15 are brought into contact with each other. It is also possible to do.

  For the light guide plates 12 and 22, a resin having excellent visible light permeability is employed, and PMMA (polymethyl methacrylate: broadly defined acrylic resin), PC (polycarbonate), or the like is employed. In addition to LEDs (light emitting diodes), CCFLs (cold cathode tubes) and HCFLs (hot cathode tubes) are used as the linear light sources 11 and 21 disposed on one end side of the light guide plates 12 and 22, but local dimming and impulsive are used. It is preferable to employ an LED in order to implement partial driving of the method.

Reflective sheets 16 and 26 are disposed on the opposing surfaces of the light emitting surfaces 13 and 23 of the light guide plates 12 and 22, respectively, and end surface reflective sheets 17 and 27 are disposed on the end surfaces of the respective light guide plates. and the end portion 16 _t of the linear light source side of the reflective sheet 16 between the second light guide plate 12 and 22 is extended between the respective linear light sources 11, 21 in order to prevent crosstalk. The reflection sheet 16 disposed between the linear light sources 11 and 21 is subjected to a reflection process or a light shielding process on both sides thereof at least at an end portion _16t located between the linear light sources.
The irregular reflection surfaces 14 and 24 formed on the light guide plates 12 and 22 can be formed by any one of a printing method, a molding method, an adhesive dot method, and a groove processing method. For example, when a printing method is used, The reflective dots are formed by applying the reflective ink to the back surface according to the gradation pattern. In the light guide plates 12 and 22, the area of the reflective dots in the vicinity of the linear light sources 11 and 21 is reduced and the area of the reflective dots is increased as the distance from the light source is increased in order to make the luminance of the entire light emitting surface uniform.

  The light emitted from the linear light sources 11 and 21 such as LEDs enters from the side surfaces of the light guide plates 12 and 22, but almost all light enters the light guide plate except for the light reflected on the surface at this time, and is totally reflected. In the region, the surface reflection is repeated, and light is scattered by the reflection dots formed on the irregular reflection surfaces 14 and 24 in the irregular reflection region, and the light exits from the light exit surfaces 13 and 23.

  In addition to the total reflection, the reflection sheets 16 and 26 reflect a component of the scattered light of the reflection dots toward the rear surface of the light guide plate and direct it toward the front surface of the light emission surface.

In the edge light type partial driving the backlight unit 10 described above, the light P _a which is reflected by the light and lamp reflector 15 exiting from the linear light source 11 of the first light guide plate 12 is incident end of the light guide plate 12 receiving light from the surface to the light guide plate within, is irregularly reflected by the reflection dots irregular reflection surface 14 and emitted from the light emitting surface 13, whereas, the light P _b emitted from the linear light source 21 of the second light guide plate 22, guide receiving light from the end face of the optical plate 22 to the light guide plate in while repeating total reflection smooth surface of the total reflection region T _b, all light entering the exception of surface reflection is total reflected light becomes light guide plate 22 In the same manner as in FIG. 5, the light is diffused by the reflecting dots of the irregular reflection surface 24 and emitted from the light exit surface 23, but in the edge light type partial drive backlight unit 10, the first and second light guides are used. Linear light source of optical plates 12 and 22 1,21 is, since the reflection process or shading on both sides are arranged on both sides of the end 16 _t of the reflection sheet 16 that has been subjected, on can prevent crosstalk, the two linear Since the substrate B of the light sources 11 and 21 is in contact with the lamp reflector 15 having a U-shaped cross section and good thermal conductivity, it is excellent in thermal diffusion, and a reduction in luminance due to heat generation of the light source can be reduced. That is, the heat generated by the LED or the like is transmitted to the substrate B made of metal or the like, and the substrate and the lamp reflector are in contact with each other. Therefore, the lamp reflector made of metal having good thermal conductivity serves as a heat sink, and the metal lamp reflector More heat is dissipated. In this case, it is possible to further improve the cooling effect by installing a heat conductive sheet between the substrate and the metal lamp reflector. In addition, the cooling effect can be adjusted by changing the area of the lamp reflector in contact with the lower portion of the reflection sheet 26.

  Furthermore, since the linear light sources 11 and 21 are covered with the lamp reflector, it is possible to prevent light leakage.

Moreover, since the lamp reflector 15 is made of a material having excellent reflectance, the reflection efficiency can be improved. As mentioned above, when using a resin lamp reflector,
When reflection is performed three times on the lamp reflector, the reflected light is reduced to about 86%. However, when a metal lamp reflector is used, the reduction of the reflected light can be remarkably reduced.

  For example, if DESR-M-SIR manufactured by 3M is used, the reflectivity is about 98%. Therefore, if reflection is performed three times on the metal lamp reflector in the LED installation area, the reflected light will be about 94%. The reflection loss can be greatly reduced as compared with the case of the resin lamp reflector.

  In the above description, the case where the linear light sources 11 and 21 are made of top view type LEDs is shown. As shown in FIG. 2, the linear light sources 11 and 21 emit side light from the side of the package. The LED can also be used.

In this case, the substrates B _a and B _b of the linear light sources 11 and 21 of the first and second light guide plates 12 and 22 are in contact with a material having a U-shaped cross section and good thermal conductivity and reflectance. Opposed.

  When the above-described top view type LED shown in FIG. 1 or side view type LED shown in FIG. 2 is mounted on a substrate, a plurality of LEDs on the substrate of each LED bar are respectively arranged in a plane perpendicular to the light guide plate. It is also possible to arrange the LEDs adjacent to each other or a plurality of LEDs on the substrates of the adjacent LED bars in a staggered manner in the direction of the LED bars in a plane perpendicular to the light guide plate. In particular, LEDs are arranged in a staggered manner in the direction of the substrate of the LED bar in a plane perpendicular to the light guide plate, and a larger number of LEDs are arranged with respect to the second light guide plate 22 than the first light guide plate 12. As a result, it is possible to diffuse the heat and to compensate for the reduction in efficiency of the light guide plate 22.

  The edge light type partial drive backlight unit 10 of FIG. 1 uses two light guide plates, but in the present invention, the edge light type partial drive backlight unit is configured by using a plurality of three or more light guide plates. can do.

That is, a third light guide plate laminated via a reflection sheet is disposed below the second light guide plate 22, and this third light guide plate is formed in a total reflection portion formed on the laminated portion with the second light guide plate. And a diffused reflection region having a light output surface adjacent to the light output surface of the second light guide plate and forming a substantially same plane, and forming a diffused reflection surface on the surface opposite to the light output surface of the irregular reflection region, The linear light sources of the first to third light guide plates are respectively arranged on both sides of the end portions of the respective reflection sheets, and the three linear light sources are made of a material having a U-shaped cross section and good thermal conductivity and reflectance. It can also be formed to cover. In this case, the length of the laminated portion of the second light guide plate 22 and the third light guide plate is longer than the length L _b of the laminated portion of the first light guide plate 12 and the second light guide plate 22. It corresponds to.

  In this configuration, the light emitting surfaces of the first to third light guide plates form substantially the same plane, and preferably the irregular reflection surfaces facing the light emitting surfaces of the irregular reflection regions of the second and third light guide plates. Is formed with reflective dots and the like on the entire surface. The above configuration can be similarly applied when there are four or more light guide plates.

  Also, two of the edge light type partial drive backlight units described above are adjacent to each other so that the linear light sources of the respective light guide plates are arranged on both ends, and the light output surfaces of the respective light guide plates are substantially Can be arranged so as to form the same plane.

  FIG. 3A shows the second light guide plate 22 of the edge light type partial drive backlight unit 10 of FIG. 1A and the second light guide plate of the edge light type partial drive backlight unit 10 ′ having the same structure. 22 ′ is a cross-sectional view of a configuration in which 22 ′ is arranged facing each other and the first and second light guide plates 12, 22, 12 ′, and 22 ′ of each unit 10, 10 ′ are arranged on the same plane. .

  In this case, the linear light sources 11, 21, 11 ′, and 21 ′ of the units 10 and 10 ′ are disposed on both ends of the units 10 and 10 ′, and are mounted on the substrates B and B ′, respectively. The substrate and the lamp reflector are arranged in contact with each other in the lamp reflectors 15 and 15 'having a U-shaped cross section.

  FIG. 3B shows a cross-sectional view of a liquid crystal display device using the edge light type partial drive backlight units 10 and 10 ′ shown in FIG. As described above, two light guide plates 12, 12 ′, 22, 22 ′ are arranged on the upper surface of the edge light type partial drive backlight units 10, 10 ′ arranged so as to face each other. The diffusion sheet DS is disposed with the prism sheet PS interposed therebetween, and the liquid crystal panel LC is disposed on the upper surface thereof. This diffusion sheet not only has the purpose of making the reflective dots inconspicuous, but also has an important function of increasing the front brightness by collecting light in the front. The prism sheet is a kind of lens sheet, and is installed on the upper surface of the light guide plate of the backlight in order to improve the luminance in the front direction.

  An edge light type partial drive backlight unit divided into a large number of areas corresponding to a large screen can be easily achieved by using a plurality of the edge light type backlight units described above.

  FIG. 4 is a plan view showing an example in which eight of the edge light type partial drive backlight units composed of the three light guide plates described above are used.

  In the figure, an edge light type partial drive backlight unit 20 ′ composed of first to third light guide plates 12, 22, 32 and an edge light composed of first to third light guide plates 12 ′, 22 ′, 32 ′. Each of the linear light sources (11, 11 ′, etc.) is arranged on both ends so that the light guide plates form the same plane in the mold partial drive backlight unit 30 ′, and these four sets are arranged in parallel. In this case, all the light guide plates form substantially the same plane. Also in this case, similarly to FIG. 3B, the diffusion sheet DS, the prism sheet PS, and the liquid crystal panel LC are disposed on the upper surface of the light guide plate.

  With the above configuration, the liquid crystal panel of the liquid crystal display device is divided into a plurality of regions, and the luminance value of the linear light source is made uniform for each divided region according to the gray level value of each divided region. Can do. Moreover, local dimming is also facilitated by controlling the linear light source corresponding to each area for each area.

  Although the present invention has been described with the specific embodiments shown in the drawings, the present invention is not limited to this, and any configuration known so far can be adopted as long as the effects of the present invention are exhibited. It goes without saying that it can be done.

  The edge light type partial drive backlight unit according to the present invention can be used for a liquid crystal display device having an area-controllable backlight.

10, 10 ', 20', 30 ', 40 Edge light type partial drive backlight unit 11, 21, 41, 51 Linear light source 12, 12', 42 First light guide plate 22, 22 ', 52 Second Light guide plate 32, 32 ′ Third light guide plate 13, 23, 43, 53 Light exit surface 14, 24, 44, 54 Diffuse reflection surface 16, 26, 46, 56 Reflective sheet 15, 15 ′, 45, 55 Lamp reflector 16 _t Reflective sheet ends 17, 27, 47, 57 End reflective sheets B, B ′, B _a , B _b Substrate LC Liquid crystal panel DS Diffusion sheet PS Prism sheet D _a , D _b Diffuse reflection area L _a , L _b Laminate T _a , T _b total reflection region P ₁ , P ₂ , P _a , P _b light

Claims (18)

  A plurality of light guide plates each having a linear light source at each end are arranged adjacent to each other so that each light exit surface of each light guide plate forms substantially the same plane, and each line of the plurality of light guide plates In the edge light type partial drive backlight unit in which the shape light sources are arranged in parallel, the edge light type partial drive backlight unit has a first surface in which an irregular reflection surface is formed on at least a part of the light emission surface of the light guide plate. And a second light guide plate having a laminated part that is laminated with the first light guide plate via a reflective sheet, and having the same structure as the first light guide plate. The light plate includes a total reflection region formed in the stacked portion and a diffuse reflection region having a light output surface adjacent to the light output surface of the first light guide plate, and at least a part of the light output surface of the diffuse reflection region. A diffuse reflection surface is formed on the opposite surface. In addition, the linear light sources of the first and second light guide plates are arranged on both sides of the end portion of the reflection sheet, and the two linear light sources have a U-shaped cross section and have good thermal conductivity and reflectivity. Edge light type partial drive backlight unit characterized by being coated with.   The second light guide plate further includes an nth light guide plate (n ≧ 3) each having a stacked portion that is sequentially stacked via a reflection sheet, and the nth light guide plate is the (n−1) th. ) And the shape of the light guide plate are different from each other, adjacent to the total reflection region formed in the laminated portion of the (n-1) light guide plate and the light exit surface of the (n-1) light guide plate, The first to nth light guide plates are formed of an irregular reflection region having a light emission surface that forms substantially the same plane, and forms an irregular reflection surface on at least a part of the light emission surface of the irregular reflection region. The linear light sources are arranged on both sides of the end of each of the reflection sheets, and the n linear light sources are covered with a material having a U-shaped cross section and good thermal conductivity and reflectance. The edge light type partial drive backlight unit according to claim 1.   3. The edge light type partial drive according to claim 1, wherein the reflection sheet disposed between the light guide plates is subjected to a reflection process or a light shielding process on both sides thereof at least between the linear light sources. Backlight unit.   The edge light type partial drive backlight unit according to any one of claims 1 to 3, wherein the linear light source of each light guide plate is formed by an LED bar in which a plurality of LEDs are arranged on a substrate. .   5. The edge light type partial drive backlight unit according to claim 4, wherein the plurality of LEDs on the LED bar substrate are of a top view type.   The edge light type partial drive backlight unit according to claim 4, wherein the plurality of LEDs on the LED bar substrate are of a side view type.   6. The edge light type partial drive backlight unit according to claim 5, wherein the plurality of LEDs are arranged on a single LED bar substrate.   8. The edge light type partial drive backlight unit according to claim 5, wherein the substrate of the LED bar is arranged in contact with a material having a U-shaped cross section and good thermal conductivity and reflectivity.   Each linear light source of the first light guide plate and the second light guide plate is formed by a side view type LED bar in which a plurality of LEDs are arranged on the substrate, and the LED bar substrate has a U-shaped thermal conductivity and reflection. 2. The edge light type partial drive backlight unit according to claim 1, wherein the edge light type partial drive backlight unit is disposed in contact with a material having a good rate.   The edge light type partial drive back according to any one of claims 4 to 9, wherein the plurality of LEDs on each LED bar substrate are arranged adjacent to each other in a plane perpendicular to the light guide plate. Light unit.   10. The plurality of LEDs on each adjacent LED bar substrate are arranged in a staggered manner in the direction of the LED bar substrate in a plane perpendicular to the light guide plate. The described edge light type partial drive backlight unit.   Each linear light source of the first light guide plate and the second light guide plate is formed by a top-view type or side-view type LED bar in which a plurality of LEDs are arranged on the substrate, and the LED bar substrate has a U-shaped cross-section of heat. A plurality of LEDs on the LED bar substrate are arranged in contact with a material having good conductivity and reflectivity, and are arranged in a staggered manner in the direction of the LED bar substrate in a plane perpendicular to the light guide plate. 2. The edge light type part according to claim 1, wherein the number of the plurality of LEDs on the LED bar substrate is larger than that of the first light guide plate with respect to the second light guide plate. Drive backlight unit.   The edge light type partial drive backlight unit according to any one of claims 1 to 12, wherein an irregular reflection surface is formed on an entire surface of the first light guide plate facing the light emitting surface.   The edge light type partial drive back according to any one of claims 1 to 13, wherein an irregular reflection surface is formed on an entire surface of the light reflection surface of the irregular reflection region of the second and nth light guide plates. Light unit.   The edge light type partial drive according to any one of claims 1 to 14, wherein the irregular reflection surface of each light guide plate is formed by any one of a printing method, a molding method, an adhesive dot method, and a groove processing method. Backlight unit.   The two partial drive backlight units according to any one of claims 1 to 15, wherein the light emitting surfaces are adjacent to each other so that the linear light sources of the backlight units are arranged at both ends, An edge light type partial drive backlight characterized in that the light emitting surfaces are arranged so as to form substantially the same plane.   A plurality of the partial drive backlights according to claim 16 are arranged adjacent to each other so that each linear light source is arranged at both ends, and the light emission surfaces of each partial drive backlight are substantially flush with each other. An edge light type partial drive backlight characterized by being arranged to form   18. A liquid crystal display device comprising the edge light type partial drive backlight according to claim 16.

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