JP5271649B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device including an edge light (side light) type backlight (hereinafter also referred to as an illumination device).

  In order to reduce the thickness of a liquid crystal display device including a liquid crystal panel, an edge light (side light) type backlight (illumination device) that irradiates light from the left or right or upper and lower ends of the liquid crystal panel may be used. As a light source of this illuminating device, a light emitting diode (LED: Light Emitting Diode) is known, for example, in Patent Document 1.

  Patent Document 1 discloses a configuration in which LEDs are arranged on a side surface of a light guide plate on the back of a liquid crystal panel, the LEDs are held by a light source fixing member having high thermal conductivity, and a liquid crystal panel, a light guide plate, a liquid crystal panel, and a light guide plate. A configuration is described in which an optical sheet (diffusion sheet) is held by a plastic frame coupled to a light source fixing member.

JP 2006-156324 A (FIGS. 39 to 42)

  In recent years, liquid crystal display devices have been increased in screen size (30 inches or more), and when a sidelight type illumination device using an LED light source is used for such a large screen device, the length of the LED light source and the heat dissipation member is large. Become. For example, when an LED light source is arranged on the short side of a device with a screen size of 32 inches, the length of the LED light source and the heat radiating member becomes as large as about 40 cm. The influence of position fluctuation) is large, and the optical performance is deteriorated. For this reason, it is necessary to fix the heat dissipation member on which the LED light source is mounted and the frame for holding the liquid crystal panel, the light guide plate, and the like with screws or the like.

  In Patent Document 1, a frame that holds an optical sheet, a liquid crystal panel, and the like is made of a resin such as plastic. On the other hand, a light source fixing member conducts heat from an LED light source. Made of high metal. When the metal part and the resin part are fixed with, for example, screws, the coefficients of thermal expansion are different from each other. Therefore, when the temperature rises, stress is generated in the frame that is the resin part due to the difference in expansion amount. When the liquid crystal display device is used as a television receiver, ON / OFF is repeatedly used several times a day, and the temperature of the heat radiating member and the frame is repeatedly increased and decreased each time. In other words, stress is repeatedly applied to the resin frame, cracks are generated in the frame, and the resin frame is warped to relieve the stress, and force is applied to the adjacent optical sheet, resulting in uneven brightness. There is a problem of doing.

  The present invention has been made in view of the above problems, and provides a technique suitable for improving the reliability of a liquid crystal display device.

The liquid crystal display device according to the present invention includes a light source disposed on the end side of the liquid crystal panel and a light source mounted on which the light source is mounted in order to irradiate light from the end side to the center of the liquid crystal panel. A substrate, a metal lamp holder that is bonded to the light source mounting substrate with a heat conductive adhesive, and heat of the light source is transmitted through the light source mounting substrate and the heat conductive adhesive; and a back side of the liquid crystal panel A light guide plate for guiding the light from the light source to the liquid crystal panel, an optical sheet disposed between the liquid crystal panel and the light guide plate, and a metal made for holding the liquid crystal panel A panel frame,
The panel frame is attached to the lamp holder via the optical sheet support, a first low friction member is interposed between the lamp holder and the optical sheet support, and the optical sheet support and the panel The second low friction member is interposed between the frame and the frame.

  According to the present invention, even if a member having a different thermal expansion coefficient is used in the lamp holder and the optical sheet support, or a member having a different thermal expansion coefficient is used in the optical sheet support and the panel frame, the low friction member Since they slide with each other, it is difficult for stress to occur in the optical sheet frame, so that reliability can be ensured over a long period of time. Therefore, according to the present invention, a highly reliable liquid crystal display device can be provided.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 100 includes a liquid crystal panel module 120, a front bezel 110 that is a casing surrounding the liquid crystal panel module 120, and a stand 150 for allowing the liquid crystal display device 100 to stand by itself. Here, for the sake of explanation, the vertical and horizontal directions and the front and back surfaces are defined with reference to the display screen 121 of the liquid crystal panel module 120. That is, when a user who watches the liquid crystal display device 100 faces the display screen 121, the front side of the display screen 121 is “front” and the back side is “back”, and the liquid crystal panel module faces the user. The right side of 120 in the horizontal direction is defined as “right” and the left side is defined as “left”. Further, the upper side in the vertical direction of the liquid crystal panel module 120 toward the user is defined as “upper” and the lower side is defined as “lower”. A back cover (not shown) is disposed on the back side of the liquid crystal panel module 120.

  2 and 3 are a front view and a perspective exploded view of the liquid crystal panel module 120, respectively.

  As shown in FIG. 3, the liquid crystal panel module 120 includes a panel frame 2, a liquid crystal panel 1, a low friction member a3, an optical sheet support 11, a low friction member b5, a light source unit 20, an optical sheet group 12, a guide, The optical plate 13, the reflection sheet 14, and the back cover 15 are configured. Here, the illumination device 10 is made from the optical sheet support 11 to the back cover 15, and the panel frame 4 and the like are fixed to the light source unit 20 by screws 4b as shown in FIG. Details of each component will be described later.

  4 is a cross-sectional view taken along line XX in FIG. The light source unit 20 includes a light source 21, a light source mounting substrate 22, a heat conductive adhesive 23, and a lamp holder 24.

  Next, the function and arrangement of each component will be described.

  In this embodiment, the light source 21 is a plurality of light emitting diodes (LEDs). For example, a plurality of sets of red, blue, and green LEDs are arranged in the vertical direction at the left and right end portions of the liquid crystal panel 1 to form an edge light type. A backlight, that is, a lighting device is configured. The light from the light source 21 is used to display an image on the liquid crystal panel 1. The liquid crystal panel 1 is discharged in the horizontal direction (left-right direction) from the left and right end portions toward the center side. The LED as the light source 21 may be a white LED, or may be configured to emit white light in two different colors (for example, yellow and blue). FIG. 4 shows only a cross section on one side of the liquid crystal panel 1, but the cross section on the other side is also symmetric. Further, in this embodiment, an example is shown in which the light sources 21 are arranged at both the left and right ends of the liquid crystal panel 1, but the present invention can be applied to those arranged only at one of the left and right ends. Further, the present invention can be similarly applied to an illumination device having a configuration in which the light source unit 130 is disposed on both or one of the upper and lower ends.

  The light source mounting board 22 is mounted with an LED as the light source 21 and has a function of supplying power to the LED. A plurality of light sources 21 are arranged in a line in the vertical direction on the mounting surface of the light source mounting substrate 22, and are arranged so that light strikes the side surfaces of the light guide plate 13. The light source mounting substrate 22 is bonded to a metal lamp holder 24 (for example, made of aluminum) for holding the light source mounting substrate 22 with a heat conductive adhesive 23 (for example, a heat conductive adhesive or silver paste). . Thereby, the heat from the light source 21 is transmitted to the lamp holder 24 through the light source mounting substrate 22 and the heat conductive adhesive 23.

  The light guide plate 13 is made of, for example, a transparent resin such as acrylic or PC (polycarbonate) with a dot pattern or a textured surface formed on the surface, and uniformizes incident light from the side surface as a surface light source. It has a function of emitting light to the side (the liquid crystal panel 1 direction) and the opposite surface (the reflective sheet 14 direction).

  The reflection sheet 14 is a resin sheet member, and has a function of reflecting the light emitted from the opposite surface (the reflection sheet 14 side) of the light guide plate 13 and returning it to the light guide plate 13. For example, the one molded with a white resin having good reflectivity or the one coated with a paint with good reflectivity is used.

  The optical sheet group 12 is configured by stacking a plurality of optical sheets (diffusion sheets, prism sheets, etc.) in the thick direction, diffusing the light emitted from the light guide plate 13 to the display screen side, further uniforming, It also has a function of improving luminance.

  The liquid crystal panel 1 has a configuration in which a liquid crystal is sandwiched between two substrates, and controls transmission / blocking of light emitted from the illumination device 10 by turning on / off the liquid crystal constituting the pixel in accordance with a video signal. It functions as a shutter.

  As shown in FIG. 4, the light guide plate 13, the reflection sheet 14, and the optical sheet group 12 are sandwiched between the lamp holder 24, the cover 15, and the optical sheet support 11. Pinched. The back cover 15 is fixed to the lamp holder 24 by a plurality of screws 4a from the back side, and the optical sheet support 11 and the panel frame 2 are fixed and attached to the lamp holder 24 by a plurality of screws 4b from the front side.

  The back cover 15 has a function of protecting the light source device from the back side and holding the member. For example, a metal plate is used for thinning.

  The optical sheet support 11 has a frame shape as shown in FIG. 2 and has a function of holding the edge of the optical sheet group 12 and the edge of the light guide plate 13. The optical sheets of the optical sheet group 12 are thin and easily distorted when affected by heat. As a result, luminance unevenness and the like occur. Therefore, the optical sheet support 11 is provided so that the heat of the light source 21 is not transmitted as much as possible through the lamp holder 24. Consists of resin. Furthermore, since the optical sheet support 11 is adjacent to the light guide plate 13 and the optical sheet group 12, if the light reflectivity is poor, the light is absorbed and the luminance is reduced. For example, the optical sheet support 11 is molded from a white resin having good reflectivity. Those having a surface coated with a good or reflective paint are used.

  The panel frame 2 has a function of holding the edge of the liquid crystal panel 1. For example, a metal plate is used for thinning.

  The low friction member b5 is sandwiched between the optical sheet support 11 and the lamp holder 24, and the low friction member a3 is sandwiched between the optical sheet support 11 and the panel frame 2.

  Hereinafter, functions of the low friction member a3 and the low friction member b5 will be described while explaining heat propagation.

  In the present embodiment, a plurality of heat sources are the light sources 21 arranged. Most of the heat of the light source 21 is transmitted to the lamp holder 24 through the light source mounting substrate 22 and the heat conductive adhesive 23. The heat of the lamp holder 24 is transmitted to the metal back cover 15 and is radiated by a heat radiating member (not shown) attached to the back cover 15 or the back cover 15 itself.

  On the other hand, the optical sheet support 11 is made of resin as described above. Further, in order to reduce the thickness of the liquid crystal display device 100 or the liquid crystal panel module 120, the thickness t of the attachment portion of the optical sheet support 11 to the lamp holder 24 is designed to be thin. Heat from the light source 21 is also transmitted to the optical sheet support 11 through the lamp holder 24. However, since the optical sheet support 11 is a resin having low thermal conductivity, heat is applied to the optical sheet group 12 and the liquid crystal panel 1. Difficult to communicate.

As described above, the optical sheet support 11 is made of a resin material, and the adjacent lamp holder 24 is made of a metal material, which have different thermal expansion coefficients. For example, the optical sheet support 11 is PC (polycarbonate, coefficient of thermal expansion 70 [× 10 ⁻⁶ / ° C.]), and the lamp holder 24 is aluminum (thermal expansion coefficient 23 [× 10 ⁻⁶ / ° C.]. ]), The optical sheet support 11 was about 55 ° C., and the lamp holder 24 was about 60 ° C. When the screen size is 32 inches, the expansion amount is about 1.7 mm for the optical sheet support 11 and about 0.6 mm for the lamp holder 24.

  When the members having different expansion amounts are fixed with the screws 4b at a plurality of positions as described above, the optical sheet support 11 made of resin tends to be longer than the metal lamp holder -24, and stress is generated. End up.

The same phenomenon occurs for the optical sheet support 11 coupled to the panel frame 2. For example, the optical sheet support 11 is a PC as described above, and the temperature rise when the panel frame 2 is a steel plate (thermal expansion coefficient 12 [× 10 ⁻⁶ / ° C.]) is as described above. About 55 degreeC and the panel frame 2 were about 50 degree | times. When the screen size is 32 inches, the expansion amount is about 1.7 mm for the optical sheet support 11 and about 0.2 mm for the panel frame 2.

  When the members having different expansion amounts are fixed with the screws 4b at a plurality of positions as described above, the resin-made optical sheet support 11 is further stressed to be relatively longer than the metal panel frame 2. End up. As a result, for example, cracks occur or luminance unevenness occurs as described below.

  When the liquid crystal display device 1 is used as a television receiver, the user repeatedly uses the power ON / OFF several times a day. That is, when the switch is turned on, the temperature rises and stress is generated in the optical sheet support 11. When the switch is turned off, the temperature is lowered and returns to the original. As described above, the temperature is repeatedly raised and lowered, and the generation of stress is repeated each time, and there is a problem that cracks occur in the resin optical sheet support 11 when used for a long period of time.

  Further, when the power is turned on, the temperature rises and the optical sheet support 11 is relatively stressed to stretch, and the optical sheet support 11 is warped to reduce the stress. Since the optical sheet support 11 sandwiches the optical sheet group 12, there is a problem that uneven brightness occurs when stress is applied to the optical sheet due to warpage.

  In order to solve this problem, in this embodiment, the low friction member b5 is disposed between the optical sheet support 11 and the lamp holder 24, and / or the low friction member a3 is disposed between the optical sheet support 11 and the panel frame 2. By disposing, the distortion of the optical sheet support 11 is relieved by changing (sliding) the relative position of the optical sheet support 11 with respect to the difference in the expansion amount due to the temperature rise. The low friction member a3 and the low friction member b5 are sheet-like members made of, for example, a fluororesin, such as a Teflon (registered trademark) sheet. When the low friction member b5 is interposed between the lamp holder 24 and the optical sheet support 11, the low friction member b5 may be bonded to either the lamp holder 24 or the optical sheet support 11. When the low friction member a3 is interposed between the lamp holder 24 and the optical sheet support 11, the low friction member a3 may be adhered to either the optical sheet support 11 or the panel frame 2. In addition to the Teflon (registered trademark) sheet, for example, a sheet or a film containing a lubricant can be used as the low friction members a3 and b5.

  In the above description, one side of both short sides of the liquid crystal panel module 120 has been described, but the same applies to the other side.

  As described above, even when used for a long period of time, the above configuration makes it difficult for stress to occur in the optical sheet support 11, thereby preventing occurrence of cracks and uneven brightness, and providing a highly reliable liquid crystal display over a long period of time. A device can be realized.

The perspective view of the liquid crystal display device regarding embodiment of this invention Front view of the liquid crystal panel module 120 Perspective exploded view of the liquid crystal panel module 120 XX sectional view of FIG.

Explanation of symbols

1 Liquid crystal panel 2 Panel frame 3 Low friction member a
4a, 4b Screw 5 Low friction member b
DESCRIPTION OF SYMBOLS 10 Illuminating device 11 Optical sheet support 12 Optical sheet group 13 Light guide plate 14 Reflective sheet 15 Back cover 20 Light source part 21 Light source 22 Light source mounting board 23 Thermal conductive adhesive 24 Lamp holder 100 Liquid crystal display device 110 Front bezel 120 Liquid crystal panel module 121 Display 150 screen stand

Claims (2)

In a liquid crystal display device equipped with a liquid crystal panel,
In order to irradiate light from the end side of the liquid crystal panel toward the center, a light source disposed on the end side of the liquid crystal panel;
A light source mounting substrate on which the light source is mounted;
A lamp holder made of metal, which is bonded to the light source mounting substrate with a heat conductive adhesive, and heat of the light source is transmitted through the light source mounting substrate and the heat conductive adhesive;
A light guide plate disposed on the back side of the liquid crystal panel for guiding light from the light source to the liquid crystal panel;
An optical sheet disposed between the liquid crystal panel and the light guide plate;
An optical sheet support made of resin for holding the optical sheet attached to the lamp holder;
A metal panel frame for holding the liquid crystal panel,
The panel frame is attached to the lamp holder via the optical sheet support;
A first low friction member is interposed between the lamp holder and the optical sheet support, and a second low friction member is interposed between the optical sheet support and the panel frame. Liquid crystal display device.   2. The liquid crystal display device according to claim 1, wherein the low friction member is a sheet-like member made of a fluororesin.

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