JP4504119B2 - Backlight unit and liquid crystal display device - Google Patents

Description

  The present invention relates to a sidelight type backlight unit and a liquid crystal display device characterized by the shape of a light guide plate and the positional relationship between the light guide plate and an LED as a light source.

  2. Description of the Related Art Conventionally, a liquid crystal display device using a liquid crystal display panel in which liquid crystal is sealed between two transparent substrates is known as a type of display device that displays various images such as characters and graphics.

  As such a liquid crystal display device, a configuration is known in which the display area of the liquid crystal display panel is brightly displayed using irradiation light from a backlight unit disposed on the non-viewing side of the liquid crystal display panel.

  And as the backlight unit, the reason is that the sidelight type (edge light type) backlight unit using a light guide plate is advantageous in reducing the thickness and heat countermeasures as compared to the direct type backlight unit. Many have been adopted.

  The sidelight type backlight unit will be further described. In the light guide plate, the light incident from the light incident surface provided on the side surface of the light guide plate and incident on the inside thereof is subjected to multiple reflection in the light guide plate. By emitting this light from the surface of the light guide plate that is disposed opposite to the liquid crystal display panel, the light from the backlight unit is irradiated as planar light toward the display area of the liquid crystal display panel. Yes. In addition, a reflection plate is disposed on the back surface of the light guide plate so that light leaking from the back surface of the light guide plate can be returned to the light guide plate (see, for example, Patent Document 1).

  FIG. 7 shows a main configuration of a general liquid crystal display device.

  In the liquid crystal display device 20, liquid crystal is sealed in a state where a spacer (not shown) for adjusting the inter-substrate dimension is interposed between the pair of transparent substrates 11a and 11b, and the outside of the pair of transparent substrates 11a and 11b. The liquid crystal display panel 10 having polarizing plates 12a and 12b disposed on the surface thereof is provided, and the backlight unit 1 is mounted so as to face the non-viewing side of the liquid crystal display panel 10.

  The backlight unit 1 includes a light guide plate 2, a reflector plate 3, a diffuser plate 4, a frame case 5 in which a recess for housing them is formed, and an LED 6 as a light source. More specifically, the diffusion plate 4 is disposed on the surface of the light guide plate 2 on the side facing the liquid crystal display panel 10, while the reflection plate 3 is disposed on the back side of the light guide plate 2. It is stored in the recess.

  Further, as shown in FIG. 8, the LED 6 has a plurality of predetermined intervals along the extending direction of the end surface 2 a so as to face the side end surface 2 a that is flush with the light guide plate 2. Are arranged. Each LED 6 emits light by power supplied from a circuit board (not shown) disposed in the backlight unit 1 through an electrode terminal (not shown), and is emitted from the light emitting surface of the LED 6. The light functions as a surface light source by the light guide plate 2, and is configured to irradiate the liquid crystal display panel 10 with irradiation light substantially uniformly by the action of the diffusion plate 4 and the reflection plate 3.

JP 2002-270022 A

  However, in the backlight unit having the above-described configuration, an area that is an intermediate portion between the positions where the LEDs 6 of the light guide plate 2 are disposed in the vicinity of the end surface 2a where the LEDs 6 are disposed (hereinafter referred to as an LED disposed area). 8 is indicated by shading in FIG. 8, since the light irradiated from the LED 6 is not easily incident and is not easily affected by multiple reflection in the light guide plate 2, the luminance is lower than that in other regions.

  That is, as shown in FIG. 9, out of the light emitted from the LED 6, only the light emitted mainly from the irradiation surface of the LED 6 that faces the end surface 2 a of the light guide plate 2 is the liquid crystal display panel 10. It was used as light for illuminating the display area. Moreover, the light irradiated from the irradiation surface facing the end surface 2a of the light guide plate 2 is also reflected by the end surface 2a of the light guide plate 2 depending on the irradiation angle with respect to the end surface 2a of the light guide plate 2, and the liquid crystal display Since the light is not used as light for irradiating the display area of the panel 10, the luminance between the LED disposed area of the light guide plate 2 and the in-plane portion corresponding to the display area of the liquid crystal display panel 10 of the light guide plate 2 There was a clear difference.

  According to the experimental result, the luminance of the measurement point (indicated by point A in FIG. 8) in the region corresponding to the display region at the end of the end surface 2a of the light guide plate 2 in the backlight unit 20 is set to 100. In this case, the luminance of the measurement point (indicated by the point B in FIG. 8) in the region between the LEDs is 20 to 30, and in the liquid crystal display panel 10 that performs image display using the backlight unit 1, The area between the LEDs on the light guide plate 2 was clearly visible as a dark part in the display area.

  If all the areas between the LEDs of the light guide plate 2 which are dark portions are arranged so as to correspond to the non-display areas in the liquid crystal display device 20, the problem of visibility of the liquid crystal display panel 10 is solved. When realized, the non-display area becomes a large area, which is contrary to the recent demand for narrowing the frame.

  Therefore, the present invention can improve the visibility of the liquid crystal display panel by increasing the brightness of the area between the LEDs in the light guide plate and reducing the brightness difference in the area corresponding to the display area of the liquid crystal display panel. Further, it is an object of the present invention to provide a backlight unit capable of narrowing the frame and a liquid crystal display device using the backlight unit.

In order to achieve the above-described object, in the backlight unit of the present invention, a plurality of LEDs are arranged at predetermined intervals along the side end face of the light guide plate, and light emitted from each LED is transmitted to the side of the light guide plate. It is made to enter into the inside of the light guide plate from the end face, and to radiate the display area of the liquid crystal display panel by emitting multiple reflections within the light guide plate and emitting it as plane light from the surface facing the liquid crystal display panel of the light guide plate The light guide plate is formed with a convex portion extending so as to partition each of the LEDs at an end of the light guide plate on the side end face side, and the light guide plate A narrow groove extending in the arrangement direction of the convex portions is formed in a region facing the liquid crystal display panel and corresponding to a non-display region of the liquid crystal display panel adjacent to the convex portions. has been Iruko The features.

  Furthermore, the backlight unit of the present invention is provided with an LED light reflector that reflects the light emitted from the LEDs and enters the light guide plate on the side of the convex portion of the light guide plate. It is characterized by being.

  The liquid crystal display device of the present invention includes the backlight unit having any one of the above-described configurations.

  According to the backlight unit of the present invention, the light emitted from each LED partitioned by the convex portion is also incident on the inter-LED disposition region of the light guide plate. The brightness of the area corresponding to the display area of the liquid crystal display panel can be improved, and as a result, the brightness difference in the area corresponding to the display area of the liquid crystal display panel can be reduced.

  Further, the area between the LEDs is provided by a narrow groove formed in a region corresponding to the non-display area of the liquid crystal display panel adjacent to the convex portion on the surface of the light guide plate facing the liquid crystal display panel. Can be reflected in the in-plane direction with respect to the narrow groove inside the light guide plate, so that the brightness of the region corresponding to the display region of the liquid crystal display panel in the region between the LEDs is further improved. As a result, the luminance difference in the area corresponding to the display area of the liquid crystal display panel can be reduced.

  Furthermore, by the LED light reflecting plate disposed on the side of the convex portion of the light guide plate, the light emitted from the LED can be reflected so as to enter the inside direction of the light guide plate. The irradiation light of the LED can be used effectively, and the luminance can be further improved in the region corresponding to the display region of the liquid crystal display panel in the region between the LEDs. As a result, the liquid crystal display panel The luminance difference in the area corresponding to the display area can be reduced.

  In addition, the convex portion is formed so as to partition each LED at the side end portion of the light guide plate, so that even if the outer dimensions of the light guide plate itself are increased, the frame is narrowed. It will not be against the request.

  According to the liquid crystal display device of the present invention, by using the backlight unit having any one of the above-described structures, the brightness difference in the area corresponding to the display area of the liquid crystal display panel is reduced and the visibility is improved. Can be made.

  Hereinafter, the backlight unit and the liquid crystal display device of the present invention will be described with reference to FIGS. In the following embodiments, only the characteristic part of the backlight unit of the present invention will be described, and the overall configuration of the backlight unit and the liquid crystal display device using the backlight unit will be described above. The backlight unit and the liquid crystal display device are the same as those in FIG.

  FIG. 1 is a main part plan view showing the positional relationship between the light guide plate 2 and the LED 6 in the first embodiment of the backlight unit 1 of the present invention, and FIG. 2 shows the irradiation light of the LED 6 into the light guide plate 2. It is explanatory drawing which shows an incident state.

  As shown in these drawings, in the backlight unit 1 of the present embodiment, a plurality of light sources serving as the light source of the backlight unit 1 are arranged on the side of the light guide plate 2 so as to face the end surface 2a of the light guide plate 2. LEDs 6 are aligned. And in the area | region corresponding to the non-display area | region of the said liquid crystal display panel 10 in the arrangement | positioning side edge part of the said LED6 of the said light-guide plate 2, the convex-shaped part 7 extended so that each of each said LED6 might be divided. Each LED 6 is formed on the inner side of an end surface (hereinafter referred to as a convex portion end surface) 7a constituting the convex portion 7, and is formed on two side surfaces (hereinafter referred to as convex portions) of the convex portion 7. (Referred to as side surfaces) 7b and 7c. In the present embodiment, the size of the gap between the LED 6 and the end surface 2a of the light guide plate 2 and the convex portion side surfaces 7b and 7c is 0.2 to 0.5 mm, preferably 0.2 to 0.3 mm. ing.

  In the backlight unit 1 of the present embodiment in which the light guide plate 2 and the LED 6 configured as described above are disposed, as shown in FIG. 2, the light irradiated from the irradiation surface of the LED 6 facing the end surface 2a. Most of the light is incident as it is from the end surface 2 a toward the in-plane direction of the light guide plate 2, that is, the region corresponding to the display region of the liquid crystal display panel 10. Further, the light reflected on the end face 2a and the light emitted from the irradiation surface of the LED 6 facing the convex portion side surfaces 7b and 7c are directed from the convex portion side surfaces 7b and 7c toward the region where the LEDs are disposed. Incident.

  In this way, the light emitted from the LED 6 is made to enter the area corresponding to the non-display area of the liquid crystal display panel in the area between the LED arrangement of the light guide plate 2. The brightness of the area corresponding to the display area of the liquid crystal display panel 10 in the intermediate area can be increased, and the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 can be reduced.

  According to the experimental result, in the backlight unit 1 of the present embodiment, the luminance of the measurement point (indicated by point A in FIG. 1) in the region facing the display region at the end of the end surface 2a of the light guide plate 2 Is 100 to 100, the luminance of the measurement point (indicated by point B in FIG. 1) of the LED is 50 to 60. Compared with the conventional backlight unit 1 described above, this embodiment The brightness of the area between the LEDs of the backlight unit 1 was significantly improved, and the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 could be reduced.

  FIG. 3 is a main part plan view showing the positional relationship between the light guide plate 2, the LED 6, and the LED light reflecting plate 8 in the second embodiment of the backlight unit of the present invention, and FIG. It is explanatory drawing which shows the incident state to the inside of the said light-guide plate. Note that description of portions common to the above-described first embodiment is omitted.

  The backlight unit of the present embodiment is arranged on the side of the convex portion 7 of the light guide plate 2 in the first embodiment, more specifically, on the end surface 7a of each convex portion 7 of the light guide plate 2. A LED light reflecting plate 8 that reflects the light emitted from the LED 6 and enters the light guide plate 2 is disposed. In the present embodiment, the LED 6 is disposed inside the convex portion end surface 7a so as to be interposed in a gap between the end surface 2a, the convex portion side surfaces 7b and 7c, and the LED light reflection plate 8. It is installed. In this embodiment, the dimension of the gap between the LED 6 and the end surface 2a and the convex side surfaces 7b and 7c is 0.2 to 0.5 mm, preferably 0.2 to 0.3 mm. A gap dimension with the LED light reflection plate 8 is 0.3 to 1.0 mm, preferably 0.5 to 1.0 mm.

  And in the backlight unit of this embodiment, as shown in FIG. 4, most of the light irradiated from the irradiation surface of the LED 6 facing the end surface 2a is directly from the end surface 2a to the surface of the light guide plate 2. Incident light is incident in an inward direction, that is, an area corresponding to the display area of the liquid crystal display panel 10. In addition, the light reflected on the end surface 2a, the light emitted from the irradiation surface of the LED 6 facing the convex-shaped side surfaces 7b and 7c, and the light reflected on the LED light reflecting plate 8 are the convex shapes. Incident from the side surfaces 7b and 7c toward the region between the LEDs.

  And by setting it as the structure which makes the light irradiated from the said LED6 inject into the area | region between said LED arrangement | positioning of the said light-guide plate 2 in this way, it respond | corresponds to the display area | region of the said liquid crystal display panel 10 in the said area | region between LED arrangement | positioning. The brightness of the area to be displayed can be increased, and the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 can be reduced.

  According to the experimental result, in the backlight unit 1 of the present embodiment, the luminance of the measurement point (indicated by point A in FIG. 3) in the region facing the display region at the end portion of the end surface 2a of the light guide plate 2. Is 100, the luminance of the measurement point (indicated by point B in FIG. 3) in the area between the LEDs is 60 to 70. Compared with the conventional backlight unit described above, the LED The brightness of the area corresponding to the display area of the liquid crystal display panel 10 in the area between the arrangements has been remarkably improved, and the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 can be reduced.

  And FIG. 5 is a principal part top view which shows the positional relationship of the light-guide plate 2, LED6, and LED light reflection board 8 in 3rd Embodiment of the backlight unit 1 of this invention, FIG. 6 is VI in FIG. It is -VI sectional drawing and is explanatory drawing which shows the reflection state in the said light-guide plate 2 of the irradiation light of said LED6.

  As shown in these drawings, the backlight unit 1 of the present embodiment is a surface facing the liquid crystal display panel 10 of the light guide plate 2 in the second embodiment described above, and is adjacent to the convex portion 7. A narrow groove 9 extending in the arrangement direction of the convex portions 7 is formed in a region corresponding to the non-display region of the liquid crystal display panel.

  In the backlight unit 1 of the present embodiment, much of the light emitted from the irradiation surface of the LED 6 facing the end surface 2a is directly from the end surface 2a to the in-plane direction of the light guide plate 2, that is, the The light enters the area corresponding to the display area of the liquid crystal display panel 10. Further, the light reflected from the end surface 2a, the light irradiated from the irradiation surface of the LED 6 facing the convex-part side surfaces 7b and 7c, and the light reflected from the LED light reflection plate 8 are reflected by the LED arrangement. Incident toward the gap area.

  In the present embodiment, the narrow groove 9 formed on the surface of the light guide plate 2 facing the liquid crystal display panel 10, in other words, using the internal protruding portion of the light guide plate 2 of the narrow groove 9. The light incident on the area corresponding to the non-display area of the liquid crystal display panel 10 in the area between the LEDs is reflected in the in-plane direction in the light guide plate 2 from the position where the narrow groove 9 is formed. Thus, the brightness of the area corresponding to the display area of the liquid crystal display panel 10 in the area between the LEDs can be further improved. As a result, the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 can be reduced. Can be small.

  According to the experimental result, the luminance of the measurement point (indicated by point A in FIG. 5) in the area corresponding to the display area at the end of the end face 2a of the light guide plate 2 in the backlight unit 1 of the present embodiment. When 100, the luminance of the measurement point (indicated by point B in FIG. 5) in the area between the LEDs is 70 to 80. Compared with the conventional backlight unit 1 described above, the LED The brightness of the area corresponding to the display area of the liquid crystal display panel 10 in the area between the arrangements has been remarkably improved, and the brightness difference in the area corresponding to the display area of the liquid crystal display panel 10 can be reduced.

  In addition, in this embodiment, arrangement | positioning of the said LED light reflection board 8 is also omissible. In that case, the luminance of the measurement point (indicated by the point B in FIG. 5) in the area between the LEDs is slightly lower than the numerical value obtained in the backlight unit 1 of the present embodiment. However, even in that case, the brightness of the region corresponding to the display region of the liquid crystal display panel 10 in the region between the LEDs is significantly improved as compared with the conventional backlight unit 1 described above, and the liquid crystal display panel The luminance difference in the area corresponding to the ten display areas can be reduced.

  Then, the liquid crystal display device of the present invention uses the backlight unit 1 having the configuration of any of the above-described embodiments, thereby reducing the luminance difference in the region corresponding to the display region of the liquid crystal display panel 10, Visibility can be improved.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed.

The top view which shows the positional relationship and luminance difference of a light-guide plate and LED in the backlight unit of 1st Embodiment of this invention. Explanatory drawing which shows the incident state to the inside of the light-guide plate of the irradiation light of LED in the backlight unit of FIG. The top view which shows the positional relationship and luminance difference of a light-guide plate and LED in the backlight unit of 2nd Embodiment of this invention. Explanatory drawing which shows the incident state to the inside of the light-guide plate of the irradiation light of LED in the backlight unit of FIG. The top view which shows the positional relationship and luminance difference of a light-guide plate and LED in the backlight unit of 3rd Embodiment of this invention. Explanatory drawing which shows the incident state to the inside of the light-guide plate of the irradiation light of LED in the backlight unit of FIG. Sectional drawing which shows the principal part structure of a general liquid crystal display device The top view which shows the positional relationship and luminance difference of the light-guide plate and LED in the conventional backlight unit Explanatory drawing which shows the incident state to the inside of the light-guide plate of the irradiation light of LED in the backlight unit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight unit 2 Light-guide plate 2a End surface 3 Reflecting plate 4 Diffusion plate 5 Frame case 6 LED
7 Convex part 7a Convex part end face 7b, 7c Convex part side surface 8 LED light reflector 9 Narrow groove 10 Liquid crystal display panel 11a, 11b Transparent substrate 12a, 12b Polarizing plate 20 Liquid crystal display device

Claims (3)

A plurality of LEDs are arranged along the side end surface of the light guide plate at a predetermined interval, and light emitted from each LED is incident on the inside of the light guide plate from the side end surface of the light guide plate and multiplexed inside the light guide plate. A backlight unit configured to irradiate a display area of the liquid crystal display panel by reflecting and emitting as planar light from a surface facing the liquid crystal display panel of the light guide plate,
A convex portion extending so as to partition each LED is formed at an end of the light guide plate on the side end surface side, and is a surface facing the liquid crystal display panel of the light guide plate. And a narrow groove extending in the arrangement direction of the convex portions is formed in a region corresponding to the non-display region of the liquid crystal display panel adjacent to the convex portions. . 2. The backlight according to claim 1, wherein an LED light reflection plate that reflects the light emitted from the LED and enters the light guide plate is disposed on a side of the convex portion of the light guide plate. unit. A liquid crystal display device comprising the backlight unit according to claim 1 .