JP2005037814A - Liquid crystal display - Google Patents

Abstract

The present invention provides a liquid crystal display device capable of preventing the occurrence of display spots by preventing an increase in temperature at the end of a liquid crystal panel without increasing the weight of the device.
At least a rear frame, a reflector, a backlight unit, and a liquid crystal display element provided on the rear frame, and the reflector, backlight unit, and liquid crystal display element from above are arranged. A liquid crystal display device comprising a metal front frame 6 fastened to the rear frame 1 by fastening means so as to be sandwiched. A heat diffusion plate 11 is provided in a region from the vicinity of the cold cathode tube 7 of the backlight unit 4 to the center of the bottom of the rear frame 1.
[Selection] Figure 3

Description

  The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device that can prevent an increase in temperature at an end portion of a liquid crystal panel and prevent occurrence of a band-like white portion (that is, display spots).

  As a conventional liquid crystal display device, a reflector, a backlight unit (cold cathode tube, reflector, light guide plate, and diffuser), an intermediate frame, and a liquid crystal panel are placed on a rear frame, and the front frame is the rear frame. There are some that are configured by meshing and fastening on the side of the.

  In this liquid crystal display device, the heat generated in the cold cathode tube is mainly radiated from the entire rear frame to the surrounding air, but part of the heat is transferred to the liquid crystal panel, and the end of the liquid crystal panel is heated and heated. Then, a band-like white portion (display spot) is displayed.

  As a technique for preventing such heat diffusion, for example, in a liquid crystal display device described in Patent Document 1, between a storage container of a backlight assembly corresponding to the rear frame and an inverter (circuit board) attached to the storage container. A laminated plate made of a metal and a synthetic resin is interposed. As a result, heat from the inverter (circuit board) is blocked to prevent heat from being transmitted to the reflector plate of the backlight assembly.

JP 2002-350807 A

  However, in order to eliminate the occurrence of display spots, it is necessary to transfer more heat from the cold-cathode tube to the rear frame side, but in the device described in Patent Document 1, heat is not easily transmitted by the laminated plate. There is a problem.

  On the other hand, as a method for suppressing the temperature rise at the end of the liquid crystal panel and facilitating the transfer of heat transmitted to the display panel to the rear frame or front frame, the rear frame plate made of aluminum or the like is used. It is conceivable to increase the thickness to reduce the thermal resistance from the position where the rear-frame cold-cathode tube is installed to the center. However, this method has a problem that the manufacturing cost increases and the weight of the apparatus increases due to the total thickness of the rear frame.

  In view of the above circumstances, the present invention prevents the occurrence of display spots by preventing the temperature rise at the end of the liquid crystal panel without increasing the manufacturing cost and weight of the device. The purpose is to provide.

The liquid crystal display device of the present invention includes at least a rear frame, a reflector, a backlight unit, and a liquid crystal display element provided on the rear frame, and sandwiching the reflector, the backlight unit, and the liquid crystal display element from above. A liquid crystal display device comprising a front frame fastened to the rear frame by fastening means,
A heat diffusion plate is provided in a region from the vicinity of the cold cathode tube of the backlight unit to the central portion of the bottom of the rear frame.

  According to the present invention, the heat diffusion plate (for example, a material having a high thermal conductivity such as an aluminum plate) is attached to the vicinity of the cold cathode tube portion of the rear frame where the temperature gradient becomes the largest. This heat is efficiently transmitted to the center portion of the rear frame, preventing temperature rise at the end of the liquid crystal panel and preventing display spots from occurring. Further, since the heat diffusion plate is partially attached to the region from the vicinity of the cold cathode tube to the central portion of the bottom portion of the rear frame, the weight of the device is larger than the case where the thickness of the heat radiating plate is increased. There is little increase in the number and there is no practical problem.

  The liquid crystal display device of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1
As shown in FIGS. 1 to 3, the liquid crystal display device according to the first embodiment of the present invention includes a metal rear frame 1 having a bottom portion and a side portion, a reflector 2 provided thereon, and a backlight unit. 3. The intermediate frame 4 and the liquid crystal display element 5 and the reflection plate 2, the backlight unit 3, the intermediate frame 4 and the liquid crystal display element 5 are fastened by clamping means such as notches and hooks to engage the hook. The front frame 6 is fastened to the rear frame 1. The front frame 6 is made of metal and has a display window on the upper surface.

  The backlight unit 3 is not particularly limited in the present invention. For example, at least the cold cathode tube 7 and the reflector 8 having an opening along the cold cathode tube 7 and having a substantially U-shaped cross section for emitting light. In addition, it is possible to use a light guide plate 9 and a diffuser plate 10 which are disposed so as to face the reflector 8 through the cold cathode tube 7 and guide light emitted in a certain direction. Further, the liquid crystal display element 3 is not particularly limited in the present invention, and is composed of, for example, a liquid crystal panel 5a and polarizing plates (not shown) disposed on both front and rear surfaces of the liquid crystal panel 5a. Things can be used. The liquid crystal panel 5a generally has two transparent substrates, that is, a thin film transistor (hereinafter referred to as TFT) serving as a switching element on the opposite surface and a TFT array substrate in which pixel electrodes are formed together with wirings, and the opposite surface. A counter substrate on which electrodes are formed is provided. An alignment film that gives initial alignment to the liquid crystal of the liquid crystal panel 5a is formed on the opposing surfaces of the two substrates, and a colored layer and a light-shielding layer are formed on the opposing surface of the counter substrate or on the opposite surface. After the two substrates are held at regular intervals via spacers, they are bonded together by a sealing material over the entire circumference except for the liquid crystal injection port. After the liquid crystal is injected between these two substrates, the liquid crystal injection port is sealed. The liquid crystal panel 5a is produced by sealing with a stopper. Further, a circuit board 5b for driving the liquid crystal display element 5 is further provided.

  Considering that the temperature gradient from the vicinity of the cold cathode tube 7 of the rear frame 1 to the center portion of the rear frame 1 is larger as the temperature is closer to the cold cathode tube 7, heat is generated near the cold cathode tube 7 having a large temperature gradient. If the diffusion plate is used, the temperature in the vicinity of the cold cathode tube 7 can be lowered.

  In the first embodiment, as shown in FIGS. 1 to 3, the heat generated in the cold cathode tube 7 is quickly absorbed and transmitted to the center of the rear frame 1 to dissipate heat to the surrounding air. Thus, in order to prevent the temperature at the end of the liquid crystal panel 5a in the vicinity of the cold cathode tube 7 from increasing, the central portion of the bottom 1a of the rear frame 1 from the vicinity of the cold cathode tube 7 of the rear frame 1 is used. The thermal diffusion plate 11 having a large thermal conductivity is installed in the area leading to the center.

  The heat diffusion plate 11 has an L-shaped cross section extending from the side portion 1b of the rear frame 1 along the axis of the cold cathode tube 7 to the center portion of the bottom portion 1a of the rear frame 1, and has a developed shape. A rectangular plate can be used. The heat diffusing plate 11 is, for example, an adhesive on the outer surface of the rear frame 1 (the outer side surface of the side portion and the back surface of the bottom portion), for example, a high heat conductive adhesive such as DM413HT (thermal conductivity 18 W / m · K) manufactured by DIEMAT. Can be pasted.

  The rear frame 1 has a role like a radiating fin for the cold cathode tube 7 and can be made of an aluminum material having good workability. The amount of heat transfer of the rear frame 1 depends on the thickness of the frame, but is usually 0.5 to 1.2 mm, especially about 0.8 mm in consideration of cost reduction (decrease in manufacturing cost) and weight reduction. A thin plate is used.

  As the heat diffusion plate 11, in order to improve the heat diffusion performance, it is better that the plate thickness is large. However, if the plate thickness is large, the weight increases, so that the plate thickness is about 1 mm and the aluminum has a high thermal conductivity. It can be made from a material. In the present invention, the material of the heat diffusing plate 11 is not particularly limited to aluminum, and can be a different metal material because it is partially attached. For example, it has a higher thermal conductivity than that of an aluminum material. A material such as copper can be used. When such copper is used as the heat diffusion plate 11, the heat diffusion performance can be further improved as compared with the case of using aluminum. Moreover, since the thermal conductivity of copper is about twice as large as the thermal conductivity of aluminum, the copper thermal diffusion plate has a thickness of 1/2 and a case where an aluminum diffusion plate of twice the thickness is pasted. It is possible to achieve compactness (weight reduction) with equivalent heat diffusion performance.

Next, for a liquid crystal display device having a display size of 15 inches, a temperature analysis of the rear frame was performed for the case where the heat diffusion plate was attached to the rear frame and the case where the heat diffusion plate was not attached (hereinafter referred to as the presence or absence of the heat diffusion plate). . In this analysis model, the bottom of the liquid crystal display device is made of a rear frame 1 made of aluminum (material: A1100) of 0.8 × 312 × 252 (thickness × horizontal × vertical) mm, and a cold cathode tube is placed on a side of 312 mm. 4 is provided. As the heat diffusion plate, an aluminum plate (material: A1100) with a size of 1.0 × 240 × 55 (thickness × width × length) mm formed so as to have an L-shaped cross section was produced. And the heat-diffusion board after shaping | molding was affixed on the center edge of the 312 mm vertical side of the said rear frame with the adhesive agent. In this example, the amount of heat generated by the cold cathode tube was 0.03 W / mm at the 312 mm end of the rear frame. At the bottom of the rear frame, heat is radiated to the ambient air (25 ° C.) by natural convection and radiant heat transfer (heat transfer coefficient: 10 W / m ² · K).

  FIG. 4 shows the temperature distribution according to the analysis result from the lower end to the center of the rear frame 1. Here, the analyzed dimensions of the rear frame are 0.8 mm in thickness and 140 mm from the lower end to the center. In FIG. 4, the temperature distribution is shown for both the case where there is a thermal diffusion plate which is an embodiment of the present invention (curve I) and the case where there is no thermal diffusion plate which is a comparative example (curve II). It can be seen that by attaching the diffusion plate, the temperature at the end of the rear frame 1, that is, when there is a heat diffusion plate (curve I), the temperature of the cold cathode tube portion is reduced by 2.7 ° C.

  Accordingly, since the temperature change of several degrees is determined depending on the presence or absence of the heat diffusing plate, in order to prevent the occurrence of display spots at the display end of the liquid crystal panel 5a, the amount of temperature drop (2.7 in the above embodiment). C) is effective.

Embodiment 2
Next, a second embodiment of the present invention will be described. In the display spots of the liquid crystal panel 5a, the center of the panel edge is emphasized due to the characteristics of the polarizing plate. Therefore, the occurrence of display spots can be prevented by cooling around the center of the cold cathode tube portion. However, since it is desired to transfer more heat to the central portion of the rear frame where the temperature is low, it is desirable that the heat diffusion plate has a large conductive cross-sectional area.

  Therefore, in the second embodiment, in order to realize both the weight reduction of the thermal diffusion plate and the improvement of the thermal diffusivity that could not be achieved by the thermal diffusion plate 11 having the rectangular shape in the first embodiment, FIG. As shown in FIG. 4, the heat diffusion plate 21 has a substantially trapezoidal shape, and the short side 21a of the heat diffusion plate 21 is on the outer surface side of the side portion 1b of the rear frame 1 along the axis of the cold cathode tube 7. The long side 21b of the heat diffusing plate 21 is arranged at the center of the back surface of the bottom 1a of the rear frame 1 so as to be substantially parallel to the short side 21a. In addition, the heat diffusion plate 21 has a short side 21a and the vicinity thereof bent upward and the cross section has an L shape.

  In the second embodiment, since the heat diffusing plate 21 has a trapezoidal shape that spreads toward the center of the rear frame 1, the heat collected in the cold-cathode tube portion is used for the rear frame 1 having a low temperature. It can guide efficiently by the central part of the. Thereby, the temperature of the cold cathode tube part can be lowered.

1 is an exploded perspective view showing a liquid crystal display device according to Embodiment 1 of the present invention. It is a perspective view which shows the reflector and thermal diffusion plate of FIG. It is sectional drawing of the liquid crystal display device of FIG. It is a figure which shows the temperature distribution of the rear flame | frame about the case where the thermal diffusion plate which is an Example of this invention exists (curve I), and the case where there is no thermal diffusion plate which is a comparative example (curve II). It is a perspective view of a rear frame and a heat diffusing plate according to Embodiment 2 of the present invention.

Explanation of symbols

  1 rear frame, 1a bottom, 1b side, 2 reflector, 3 backlight unit, 4 intermediate frame, 5 liquid crystal display element, 5a liquid crystal panel, 5b drive circuit board, 6 front frame, 7 cold cathode tube, 8 reflector, 9 light guide plate, 10 diffusion plate, 11 heat diffusion plate, 21 heat diffusion plate, 21a short side, 21b long side.

Claims (4)

At least a rear frame, a reflector, a backlight unit, and a liquid crystal display element provided on the rear frame, and fastening with the rear frame by fastening means so as to sandwich the reflector, backlight unit, and liquid crystal display element from above A liquid crystal display device comprising a front frame,
A liquid crystal display device in which a heat diffusion plate is provided in a region from the vicinity of the cold cathode tube of the backlight unit to the center of the bottom of the rear frame. The heat diffusion plate has a rectangular shape and extends from an outer surface of a side portion of the rear frame along an axis of the cold-cathode tube to a central portion of a rear surface of the bottom portion of the rear frame. 1. A liquid crystal display device according to 1. The heat diffusion plate has a substantially trapezoidal shape, and the short side of the heat diffusion plate is disposed on the outer surface side of the side portion of the rear frame along the axis of the cold cathode tube, and the length of the heat diffusion plate is long. The liquid crystal display device according to claim 1, wherein the side is disposed at a central portion of the back surface of the bottom portion of the rear frame substantially parallel to the short side. The liquid crystal display device according to claim 1, wherein the heat diffusion plate is made of copper.

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