JP2011243563A - Backlight module and liquid crystal display equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight module and a liquid crystal display capable of controlling generation of dark spots in a corner portion where a lamp unit of a light guide panel is arranged, and also making an effective display area larger.SOLUTION: The backlight module Bm includes: the lamp unit 2 arranged along a light incident surface formed on a side face of the light guide plate 3; a light-diffusing member 5 to diffuse the light emitted from a light-emitting surface of the light guide plate 3; and protrusions 511, 521, 531 where the light-diffusing member 5 covers corner portions on a light incident surface side of the light-emitting surface.

Description

  The present invention relates to a backlight module with less luminance unevenness and a liquid crystal display device having the backlight module.

  In a liquid crystal display device used in a notebook computer or a thin television receiver, a transmissive liquid crystal module is generally employed. A backlight module is attached to the back of the transmissive liquid crystal module. The liquid crystal display device displays an image on the front surface of the liquid crystal module by transmitting or reflecting the light emitted from the backlight module by the liquid crystal module.

  The backlight module is roughly divided into a light guide plate method using a light guide plate and allowing light to enter from the side surface of the light guide plate (edge light method), and a direct type method in which light sources are arranged side by side on the back of the liquid crystal module. There are two methods. In the light guide plate method, light sources are arranged on the side surface of the light guide plate, so that the number of light sources can be reduced as compared with the direct type. In addition, by reducing the number of light sources, power consumption can be suppressed, and the liquid crystal display device body can be made thinner, and has recently been reviewed.

  A conventional light guide plate type backlight module will be described with reference to the drawings. FIG. 6 is a front view of a conventional backlight module. The backlight module includes a rectangular frame 91, a lamp unit 92 embedded inside the long side of the frame 91, a light guide plate 93 disposed inside the frame 91, and a light guide plate 93. And a light diffusing member 94 affixed to.

  The light diffusion member 94 includes a lens sheet, an upper diffusion sheet attached to the upper surface (surface on the liquid crystal module side) of the lens sheet, and a lower diffusion sheet attached to the lower surface (surface on the diffusion plate side) of the lens sheet. I have.

  As shown in FIG. 6, in the backlight module, the light diffusion member 94 is attached to the light guide plate 93 so as not to cover a portion in the vicinity of the lamp unit 92. By not covering the vicinity of the lamp unit 92 of the light guide plate 93 with the light diffusion member 94 in this way, the amount of light emitted from the backlight module becomes substantially uniform.

  In many light guide plate type backlight modules, a cold cathode fluorescent lamp (CCFL) is used as a light source of the lamp unit 92. The cold-cathode tube is provided with electrodes at both ends thereof, and the amount of light at the corner on the lamp unit 92 side of the backlight module decreases, that is, it becomes dark.

  In recent years, the number of light sources that use LEDs has increased. In the case of using an LED, an LED package in which a plurality of LEDs are packaged is arranged side by side along the frame 91. In this case as well, a connector is attached to one end, and the LED package Is designed not to be arranged at the end, so that the amount of light is reduced as in the case of using a cold cathode tube. In addition, the LED package is often not disposed at the other end, and the amount of light at the corner near the other end is reduced.

  If a dark part is formed at the corner, the dark part affects the effective display area of the liquid crystal module, which deteriorates the appearance display quality of the liquid crystal display device.

  Therefore, in order to eliminate dark portions (dark portions) at corners, when the light guide plate is a printed light guide plate, a method of adjusting the printing density and film thickness at the corners is employed. When the light guide plate is a molded light guide plate, a method of increasing the light quantity at the corners by adjusting the molding pattern of the light incident surface on which light is incident is used.

  Further, in the invention described in Japanese Patent No. 3809328, a light output control pattern having groove-shaped and uneven textures is formed in the vicinity of the corner of the light guide plate. Accordingly, light is easily emitted from the corner of the light guide plate, and unevenness is suppressed.

  Further, in Japanese Patent No. 4224354, a lamp holder that holds both ends of a lamp that is a linear light source is formed to be transparent or semi-transparent, and both end portions are arranged inside the side wall, whereby both end portions of the lamp are arranged. Is effectively irradiated to the light guide plate to suppress unevenness.

Japanese Patent No. 3809328 Japanese Patent No. 4224354

  However, it is difficult to obtain a sufficient amount of light by adjusting the printing density and film thickness, and adjusting the molding pattern on the light incident surface. In addition, as in the invention described in Japanese Patent No. 3809328, in the case of a method of increasing the amount of emitted light by making the surface uneven, it is difficult to form effective grooves and wrinkles, and the configuration of the lamp unit (the arrangement of the LED package) ) Changes, it is considered that the same effect cannot be exhibited.

  In the case of the invention described in Japanese Patent No. 4224354, when the lamp unit uses a linear light source such as a cold-cathode tube, it has the effect of eliminating the dark part generated at the corner, but the LED that is a point light source is It is difficult to adopt the same technology for a backlight module in which a plurality of collected LED packages are arranged at a predetermined interval.

  Accordingly, the present invention provides a backlight module of a light guide plate type, and a backlight module and a liquid crystal display device capable of suppressing the generation of dark portions at the corners where the lamp units of the light guide plate are arranged and increasing the effective display area. The purpose is to do.

  In order to achieve the above object, the present invention is arranged along a transparent rectangular plate-shaped light guide plate and a light incident surface formed on a side surface of the light guide plate, and emits light toward the light incident surface. A backlight module comprising: a lamp unit; and a light diffusing member that is attached to a light exit surface from which light from the light guide plate is emitted and diffuses light emitted from the light exit surface. A protrusion is provided to cover a corner of the light exit surface on the light incident surface side.

  According to this configuration, a portion where a dark portion has conventionally occurred can emit a sufficient amount of light, and the ability of the backlight can be enhanced. Moreover, the effective area can be expanded by suppressing the occurrence of dark areas, and the same effective area can be proved with a backlight smaller than that of the conventional one. Thereby, the output of a lamp unit can also be suppressed and it is possible to reduce energy consumption.

  The said structure WHEREIN: The said light-diffusion member is a laminated body which bonded the diffusion sheet and the lens sheet.

  In the above configuration, the light guide plate may include two or more light incident surfaces, and the lamp unit may be disposed on each of the light incident surfaces.

  In the above configuration, the lamp unit includes LEDs arranged in a straight line and includes a connector for supplying power to an end portion, and the protruding portion covers at least a portion of the light emitting surface overlapping the connector. What is formed like this can be mentioned.

  For example, in the case of a lamp unit formed so that the interval between adjacent LEDs increases from the center toward the end, a dark part tends to occur at the end. The number of LEDs can be reduced as compared with the case where they are arranged at equal intervals without narrowing the effective area.

  In the above configuration, the lamp unit includes an arc tube, and the protrusion is formed so as to cover at least a portion of the light exit surface that overlaps a lead wire provided at an end of the arc tube. There may be.

  A liquid crystal display device can be given as an example of equipment using the backlight module of the present invention.

  According to the present invention, there is provided a backlight module of a light guide plate type and a liquid crystal display device capable of suppressing generation of a dark portion at a corner portion where a lamp unit of the light guide plate is disposed and increasing an effective display area. can do.

It is a disassembled perspective view of the backlight module concerning this invention. It is a front view of the backlight module concerning this invention. FIG. 3 is an enlarged view of a corner portion of the backlight module shown in FIG. It is a graph which shows the measurement result of an Example. It is a disassembled perspective view of the liquid crystal television receiver using the liquid crystal display device concerning this invention. It is a front view of the conventional backlight module.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is an exploded perspective view of a backlight module according to the present invention, FIG. 2 is a front view of the backlight module shown in FIG. 1, and FIG. 3 is an enlarged view of a corner of the backlight module shown in FIG. It is. As shown in FIG. 1, the backlight module Bm includes a frame 1, a lamp unit 2, a light guide plate 3, a reflection plate 4, and a light diffusion member 5.

  The frame 1 is an integrally molded body of resin, and is formed in a rectangular frame shape by connecting four wall bodies. Each wall is formed with a shelf extending inward, and the lamp unit 2 is attached to one of the sides (the lower side in FIGS. 1 and 2). Each wall body of the frame 1 includes a shelf that protrudes toward the inside, and a reflection plate 4, a light guide plate 3, and a light diffusion member 5 are arranged in this order on the top of the shelf. The outer periphery of the light guide plate 3, the reflection plate 4, and the light diffusing member 5 is supported by the shelf.

  As shown in FIG. 1, the light guide plate 3 has a light incident surface 31 on which light emitted from the lamp unit 2 formed on the side is incident and a light output surface 32 formed on the upper portion. The light guide plate 3 is formed of a transparent acrylic plate, and reflection dots are formed on the surface opposite to the light output surface 32 when the light guide plate 3 is molded or by printing. Light incident from the light incident surface 31 is reflected by the reflective dots and emitted from the light output surface 32.

  The reflection plate 4 is a reflection member that is disposed on the lower surface of the light guide plate 3, reflects light emitted from the lower surface of the light guide plate 3, and reenters the light guide plate 3. The reflecting plate 4 has a white surface facing the light guide plate 3. By providing the reflecting plate 4, light leaking from the lower surface of the light guide plate 3 can be used again, and a reduction in the amount of light can be suppressed. Further, the reflection plate 4 also acts as a support member that supports the light guide plate 3 and the light diffusion member 5.

  The light diffusing member 5 is an optical member attached to the light exit surface of the light guide plate 3. As shown in FIG. 1, the light diffusion member 5 includes a lower diffusion sheet 51 disposed close to the light guide plate 3, an upper diffusion sheet 52 disposed away from the light guide plate 3, and a lower diffusion sheet 51. And a lens sheet 53 disposed between the upper diffusion sheet 52 and the upper diffusion sheet 52. The lower diffusion sheet 51 and the lens sheet 53 and the lens sheet 53 and the upper diffusion sheet 52 are attached and laminated. The lower diffusion sheet 51 is in contact with the light guide plate 3.

  The two diffusion sheets 51 and 52 and the lens sheet 53 diffuse light in different forms. The light emitted from the light exit surface of the light guide plate 3 is diffused when passing through the light diffusing member 5, the light quantity in the surface is aligned within a certain range, and the light is emitted as surface emitting illumination light.

  As shown in FIG. 1, the backlight module Bm includes a pressing member 6 that contacts the frame 1 and presses the light guide plate 3, the reflection plate 4, and the light diffusion member 5. The pressing member 6 does not block the light emitted from the light diffusing member 5, and presses the light diffusing member 5 to the frame 1 only around the periphery so that the light guide plate 3, the reflecting plate 4 and the light diffusing member 5 can be firmly held. It has a configuration with a surface.

  As shown in FIGS. 2 and 3, the lamp unit 2 includes an elongated base 21, an LED package 22 arranged side by side with the base 21, and a connector 23 attached to one end of the base 21. It has. The LED package 22 contains a plurality of LED elements. Although not shown, each LED package 22 is connected to a wiring from a connector 23, and power is supplied through the wiring. The lamp unit 2 is attached so that the LED package 22 emits light inside the frame 1.

  The principal part of the backlight module according to the present invention will be described with reference to the drawings. As shown in FIGS. 2, 3, etc., the backlight module Bm according to the present invention covers the light diffusing member 5 at both corners on the light incident surface side of the light guide plate 3, that is, the portion overlapping the end of the lamp unit 2. It is formed as follows. That is, the lower diffusion sheet 51 includes a protrusion 511 at the corner on the lamp unit 2 side. Similarly, the upper diffusion sheet 52 and the lens sheet 53 also include protrusions 521 and 531 at corners on the lamp unit 2 side.

  These protrusions 511, 521, and 531 are arranged so as to cover a dark part that has conventionally occurred at the corner of the lamp unit 2 of the backlight module Bm. In this way, by attaching the lower diffusion sheet 51, the upper diffusion sheet 52, and the lens sheet 53 on which the protruding portions 511, 521, and 531 are formed to the light guide plate 3, light is diffused even in a portion where a dark portion has conventionally occurred. It is possible to suppress the occurrence of dark parts. The protruding portions 511, 521, and 531 are formed so as to cover at least the light emitting surface 32 adjacent to the portion where the LED package 22 is not disposed and the portion where the connector 23 is formed.

  Next, the effect of the backlight module of the present invention will be described with reference to experimental results. As an example, a light emission test of the backlight module was performed under the following conditions, and the luminance was measured and compared in a place where a dark part had conventionally occurred.

The details of the backlight module used for comparison with the backlight module according to the present invention are as follows.
(Backlight module according to the present invention)
Backlight size: 21.6 type LED light source (light guide plate format)
LED arrangement: Arranged on the lower side Number of LED packages: 40 Other conditions are as follows. The configuration of the backlight is laminated in the order of a reflection sheet, a printed light guide plate, a lower diffusion sheet, a lens sheet, and an upper diffusion sheet, and is arranged in the frame. The lower diffusion sheet, the lens sheet, and the upper diffusion sheet are attached to the light guide plate so as to expose only the central part on one side of the lamp unit and cover the corners (see FIG. 2).

(Backlight module of comparative example)
Backlight size: 21.6 type LED light source (light guide plate format)
LED arrangement: Arranged on the lower side Number of LED packages: 40 Other conditions are as follows. The configuration of the backlight is laminated in the order of a reflection sheet, a printed light guide plate, a lower diffusion sheet, a lens sheet, and an upper diffusion sheet, and is arranged in the frame. The lower diffusion sheet, the lens sheet, and the upper diffusion sheet are attached to the light guide plate so that one side of the lamp unit is exposed (the shape shown in FIG. 6).

  The backlight module according to the present invention and the backlight module of the comparative example are all tested under the same conditions except that the shapes of the lower diffusion sheet, the lens sheet, and the upper diffusion sheet are different.

(Measurement)
In both the conventional backlight module and the backlight module according to the present invention, the luminance of the corner (the lower left corner in FIGS. 2 and 6) on the side opposite to the connector on the side where the lamp unit is disposed was measured. Specifically, the brightness at 5 mm (point A), 10 mm (point B), and 15 mm (point C) from the lateral end was measured at a portion where the height from the side on the lamp unit side of the backlight module was equal. .

また、図４にこの測定結果のグラフを示す。図４に示すグラフはＡＢＣ各点における比較例のバックライトモジュールで測定された輝度を１００（％）としたときの本発明の輝度変化率を示すグラフである。 (Measurement result)
The measurement results are as shown in Table 1.

FIG. 4 shows a graph of the measurement results. The graph shown in FIG. 4 is a graph showing the luminance change rate of the present invention when the luminance measured by the backlight module of the comparative example at each point of ABC is 100 (%).

  As shown in FIG. 4, the backlight module of the present invention has 109.6 (%) at point A, 108.7 (%) at point B, and 102.4 (%) at point C. It can be seen that the luminance is higher at any of the points, points B, and C than the backlight module of the comparative example. Then, it can be seen that the rate of change in luminance is greater on the side of point A than on point C, that is, the effect of suppressing the occurrence of dark portions is higher.

  From this result, it can be seen that in the backlight module Bm of the present invention, the dark portion is improved at the corner where the light from the lamp unit 2 is difficult to reach. For example, in the case of a lamp unit in which LED packages are arranged at unequal pitches, the arrangement pitch of the LED unit LED packages is often dense at the center and sparse at the ends, so that light reaches the corners of the backlight module. Often difficult. By adopting the configuration of the present invention in such a backlight module using a lamp unit in which LED packages are arranged at unequal pitches, it is possible to suppress the occurrence of dark portions.

  A liquid crystal display device using a backlight module according to the present invention will be described with reference to the drawings. FIG. 5 is an exploded perspective view of a liquid crystal television receiver using the liquid crystal display device according to the present invention. As shown in FIG. 5, the liquid crystal television receiver Lt includes a front panel Fp and a rear panel Rp, and a liquid crystal display device L is disposed in a space between the front panel Fp and the rear panel Rp.

  As shown in FIG. 5, the liquid crystal display device L includes a liquid crystal module Lm and a backlight module Bm attached to the back side of the liquid crystal module Lm. The liquid crystal module Lm forms an image by transmitting or blocking light from the backlight module Bm to the front side.

  An opening window Ow is formed in the front panel Fp of the liquid crystal television receiver Lt. The image display surface in front of the liquid crystal display device L has an effective display area Ea at the center. The liquid crystal television receiver Lt is formed so that the effective display area Ea can be viewed from the opening window Ow. That is, the size of the screen that can be viewed by the user of the liquid crystal television receiver Lt depends on the size of the opening window Ow, that is, the effective display area Ea.

  The effective display area Ea is an area where there is little difference in the amount of light in the plane and it is difficult for the image to be uneven. In the liquid crystal display device L of the present invention, it is possible to suppress the occurrence of dark portions at the corners near the lamp, so that even when a lamp unit and a light guide plate having the same size and shape are used, an effective display area is improved compared to the conventional one It is possible to increase Ea.

  Thereby, in the case of the liquid crystal television receiver having the same screen size, the liquid crystal display device L using the liquid crystal display device L according to the present invention can be downsized compared to the conventional one. . Therefore, the external dimensions of the liquid crystal television receiver can be reduced. In addition, since a small liquid crystal display device L can be used, the lamp unit can often be a small lamp unit, and power consumption can be reduced accordingly.

  In the above embodiment, a liquid crystal television receiver is cited as an example of a device provided with a liquid crystal display device, but the present invention is not limited thereto, and a flat screen such as a digital photo frame or a personal computer display is used. It can be widely used in equipment equipped.

  In the backlight module Bm described above, an example in which a plurality of LED packages are arranged side by side as a lamp unit has been described. However, the present invention is not limited to this. For example, when an arc tube such as a cold cathode tube is used, both ends of the arc tube are provided with leads for supplying electric power, so the amount of light is small. As a result, a dark portion is likely to occur at the corner on the lamp unit side as in the case of using an LED package, but when using a backlight equipped with the light diffusing member of the present invention, Generation | occurrence | production can be suppressed and the effect similar to what used the LED package can be acquired.

  The present invention can be used for an electronic device in which a plurality of substrates are arranged side by side.

L Liquid crystal display device Lm Liquid crystal module Bm Backlight module 1 Frame 2 Lamp unit 21 Base 22 LED package 3 Light guide plate 4 Reflecting plate 5 Light diffusion member 51 Lower diffusion sheet 52 Upper diffusion sheet 53 Lens sheet 6 Holding member

Claims (6)

A light guide plate;
A lamp unit that is disposed along a light incident surface formed on a side surface of the light guide plate and emits light toward the light incident surface;
A backlight module including a light diffusing member that is disposed on a light exit surface side of the light guide plate and diffuses light emitted from the light exit surface;
The backlight module, wherein the light diffusing member includes a protrusion that covers a corner of the light exit surface on the light incident surface side.   The backlight module according to claim 1, wherein the light diffusion member is a laminated body in which a diffusion sheet and a lens sheet are bonded together. The light guide plate includes two or more light incident surfaces,
The backlight module according to claim 1, wherein the lamp unit is provided on each of the light incident surfaces. The lamp unit includes LEDs arranged in a straight line and a connector for supplying power to the end portion,
The backlight module according to any one of claims 1 to 3, wherein the protruding portion is formed so as to cover at least a portion of the light exit surface that overlaps the connector. The lamp unit includes an arc tube,
The backlight module according to any one of claims 1 to 3, wherein the protruding portion is formed so as to cover at least a portion of the light exit surface that overlaps a lead wire provided at an end portion of the arc tube.   A liquid crystal display device comprising the backlight module according to claim 1.

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