JP4659708B2 - Backlight device and liquid crystal display device - Google Patents

Description

  The present invention relates to a backlight device used as a light source for a liquid crystal television or the like and a liquid crystal display device using the backlight device, and in particular, supports an optical sheet constituting the backlight device so as not to cause wrinkles and uniform luminance. The present invention relates to a backlight device and a liquid crystal display device using the backlight device.

  Conventionally, a backlight device used for a liquid crystal display device such as a liquid crystal television has a diffusion plate made of an acrylic plate or the like disposed in front of a fluorescent lamp as a light source, and an ITO sheet, a diffusion film, a prism sheet, a reflective polarizing film in front of the diffusion plate. An optical sheet such as is arranged. These diffusion plates and optical sheets have different expansion coefficients. For this reason, each time the backlight device is turned on, the backlight device expands at different elongation amounts as the temperature starts to rise from room temperature. At this time, if the optical sheet is in close contact with the diffuser plate partially or entirely, the amount of expansion / contraction is different, and ring-shaped wrinkles are generated on the optical sheet side. When wrinkles occur, shadows appear on the front LCD panel, resulting in uneven brightness.

  Conventionally, as a countermeasure, when the irradiation surface of the backlight device is supported vertically, a plurality of pins are provided on the abutting surface of the reflector base plate with which the upper end of the diffusing plate abuts, and a hole is formed at the upper end. The formed diffusion plate and each optical sheet were locked to the pins, and the diffusion plate and the optical sheet were held in a state of being suspended by their own weight. In this state, an external force is not applied to the optical sheet in the thickness direction, and the optical sheet is held so that it can freely expand and contract through a minute gap without being in close contact with the diffusion plate. With this configuration, a relatively small-sized backlight device can be held without generating a noticeable size wrinkle.

However, when the size of the backlight device is increased, it becomes difficult to hold the optical sheet without being in close contact with the diffusion plate, and the optical sheet is in close contact with the diffusion plate in part or on the entire surface, thereby causing wrinkles. When the size of the wrinkles becomes conspicuous, the shadow may be reflected on the liquid crystal panel on the front surface, resulting in uneven brightness. As a countermeasure for this, as described in Patent Document 1, there is one in which an appropriate portion of the end portion of the optical sheet is pressed.
JP-A-11-281966

  Thus, conventionally, in order to prevent wrinkles generated on the optical sheet, attempts have been made to hold down the appropriate portion of the edge of the optical sheet. As the light device becomes even larger, the elongation of the optical sheet also increases proportionally, and the generation of wrinkles cannot be completely prevented by simply pressing the appropriate portion of the edge of the optical sheet. Accordingly, the present invention can reliably prevent wrinkling of the optical sheet and maintain uniform brightness even in a large-sized backlight device in which the amount of expansion of the optical sheet due to thermal expansion is large. The purpose was to propose a backlight device and a liquid crystal display device.

  In order to solve the above-described problems, a backlight device according to the present invention includes a rectangular diffusion plate disposed in front of a light source, and one or more optical sheets having substantially the same shape as the diffusion plate are stacked on the front surface of the diffusion plate. The arranged backlight device is characterized in that a plurality of peripheral edges of the optical sheet are supported by applying tension in the extending direction.

  The backlight device of the present invention is a backlight device in which a rectangular diffusion plate is disposed in front of a light source, and one or more optical sheets having substantially the same shape as the diffusion plate are stacked on the front surface of the diffusion plate. The engagement holes formed at a plurality of locations on the edge of the optical sheet, the longitudinal direction being held substantially perpendicular to the optical sheet, the distal end is engaged with the engagement hole, and the base end is the back And an elastic plate fixed to the side surface of the light device casing, and the elastic plate is elastically deformed inward to engage the engagement hole at the tip thereof to apply tension to the optical sheet in the extending direction. It is characterized by being supported.

  Here, when the irradiation surface of the backlight device is held vertically, each of the optical sheets engages with an elastic plate in an engagement hole formed in each of opposing edge portions in the vertical direction, and the upper side The restoring force at the time of elastic deformation of the elastic plate installed at the edge portion of the elastic plate is made larger than the restoring force at the time of elastic deformation of the elastic plate installed at the lower edge portion.

  Further, the backlight device of the present invention is a backlight device in which a diffusion plate is disposed in front of the light source and a plurality of optical sheets are disposed on the front surface of the diffusion plate. An engagement hole formed and projecting substantially perpendicularly to the optical sheet on the outer backlight device housing side opposite to the engagement hole, and the engagement hole on the one side is engaged. The engaging protrusion is engaged with the optical sheet on the outer side of the opposite backlight device housing on the other side of the engaging hole, and the engaging hole on the other side is engaged. An elastic plate, and the elastic plate is elastically deformed inward, the engagement hole is engaged with the tip of the elastic plate, and the optical sheet is supported by applying tension in the extending direction. Features.

  Here, the engagement hole and the elastic plate or / and the engagement protrusion engaged with the engagement hole can be provided at both ends of either one of the longitudinal direction and the short direction of the backlight device. Moreover, it is preferable to project a check claw at a portion that has passed through the engagement hole on the outer side of the elastic plate and the engagement protrusion. The liquid crystal display device of the present invention is characterized in that a liquid crystal panel is disposed in front of the backlight device.

  As described above, according to the present invention, by supporting the edge of the outer periphery of the optical sheet in the extending direction and having a tension, even if the optical sheet repeats thermal expansion and contraction, the expansion and contraction of the optical sheet is achieved. Is absorbed and no longer adheres to the diffuser, eliminating the occurrence of wrinkles caused by wrinkles between the optical sheet and the diffuser when heated and expanded, thereby providing a backlight device and a liquid crystal display device with stable brightness. It is done. Furthermore, the backlight device and the liquid crystal display device can be increased in size.

  Hereinafter, a case where the present invention is applied to a backlight device of a liquid crystal television will be described with reference to the drawings. 1 to 3 are external views of a liquid crystal television. In the figure, reference numeral 100 denotes a liquid crystal panel for displaying an image, 101 denotes a front cabinet, 102 denotes a rear cabinet, 103 denotes operation buttons of the liquid crystal television main body, 104 denotes a speaker, and 105 denotes a stand.

  Next, the internal configuration of the liquid crystal television will be described with reference to FIGS. The liquid crystal panel 100 is held by a holding bracket to constitute a liquid crystal panel unit 110, and an optical sheet 111 constituted by a reflection / polarization sheet, a prism sheet, a diffusion sheet, a diffusion plate, or the like is disposed on the back surface thereof. A reflective sheet 116 is fixed to the liquid crystal panel 100 side of the backlight chassis 117 with a lamp clip (not shown), and a plurality of pieces having both ends fixed by a lamp holder upper 113 and a lamp holder lower 114 are fixed to the front surface of the reflective sheet 116. A lamp 115 is arranged.

  As an assembling procedure of this portion, after fixing the reflection sheet 116 with a lamp clip to the liquid crystal panel 100 side of the backlight chassis 117, the lamp holder lower 114 is fixed to the backlight chassis 117 with the reflection sheet 116 interposed therebetween. Next, the lamp 115 is arranged in a lamp fixing groove provided at a predetermined interval on the lamp holder lower 114 so that the left and right positions are aligned, and then the lamp holder upper 113 is aligned, and both ends of the lamp 115 are covered. By fixing the lamp holder bottom 114, the light source portion is completed.

  Next, after the optical sheet 111 is held, the liquid crystal panel unit 110 fixed to the front cabinet 101 and the backlight chassis 117 are screwed in advance, so that the display optical system of the liquid crystal television is attached to the front cabinet 101. To complete. On the back surface of the backlight chassis 117 (the surface opposite to the liquid crystal panel 100) is a liquid crystal such as a drive circuit unit of the liquid crystal panel 100, a lamp 115 drive circuit unit, a video or audio signal receiving circuit unit or a signal processing circuit unit. A unit for driving the TV and various controls is mounted, and the liquid crystal television unit constituted by these series of steps is covered with the rear cabinet 102 and fixed to the front cabinet 101 by screws to complete the liquid crystal television main body.

  6 is an exploded perspective view showing a state in which the backlight device is taken out from the liquid crystal television of FIG. 1 and the liquid crystal panel 100 is removed and placed horizontally, and FIG. 7 is an exploded perspective view of the backlight device of FIG. FIG. 8 is a cross-sectional view taken along the line AA in a state where it is mounted, and FIG. 8 is a cross-sectional view taken along the line BB in FIG. As shown in these drawings, in the backlight device, a fluorescent tube 5 serving as a light source is disposed at the bottom of a box-shaped sheet metal backlight shield 1, and the end on the open side of the backlight shield 1 is outside. The optical member holding portion 1a is provided so as to protrude one step further, and the rectangular diffusion plate 2 and optical sheets 3 and 4 are held. The optical sheet used here is an ITO sheet, a diffusion film, a prism sheet, a reflective polarizing film, or the like. In addition, a liquid crystal panel 100 is disposed in front of the optical sheet 4, and a bezel 14 holds the outer periphery of the liquid crystal panel 100 to constitute a liquid crystal television.

  On the side surface of the outer periphery of the backlight shield 1, elastic plates 6 to 13 made of a metal plate or a resin plate are held perpendicular to the surface of the liquid crystal panel 100, and the lower end of the elastic plate 6 to 13 is secured to the backlight shield 1 by screws 15. It is concluded. Upper portions of the elastic plates 6 to 13 protrude upward from the optical member holding portion 1 a of the backlight shield 1. On the outer surface near the upper end of the elastic plates 6 to 13 and the like, check claws 6a and 7a and the like are erected.

  Optical sheets 3 and 4 are supported on the optical member holding portion 1a by applying tension outwardly by elastic plates 6, 8, 11, and 13 and elastic plates 7, 9, 10, and 12, respectively. Yes. That is, square holes 3a are formed on the outer peripheral edge of the optical sheet 3, and a rectangular notch 3b is formed. The elastic plates 6, 8, 11, 13, etc. are inserted into the square holes 3 a while being curved inward, and are held when they pass through the check claws 6 a, etc. Similarly, square holes 4a are formed in the outer peripheral edge of the optical sheet 4, and a rectangular notch 4b is formed. The elastic plates 7, 9, 10, 12, etc. are inserted into the square holes 4 a while being bent inward, and are held when they pass through the check pawls 7 a, etc.

  At this time, the notch 3b of the optical sheet 3 prevents the optical sheet 3 from interfering with the elastic plates 7, 9, 10, 12 and the like to which the optical sheet 4 is locked. Similarly, the notch 4b of the optical sheet 4 prevents the optical sheet 4 from interfering with the elastic plates 6, 8, 11, 13 and the like on which the optical sheet 3 is locked. In this way, the liquid crystal panel 100 supported by the bezel 14 is placed in front of the optical sheets 3 and 4 held therein, thereby forming a liquid crystal television. A notch 2a is also formed in the outer peripheral edge portion of the diffusion plate 2 inside the optical sheets 3 and 4 so that the elastic plates 6 to 13 and the diffusion plate 2 do not interfere with each other.

  In the backlight device described above, since the optical sheets 3 and 4 are supported by applying tension in the outward direction, the optical sheets 3 and 4 are held in front of the diffusion plate 2 without generating wrinkles even at room temperature. Is done. Here, even if the fluorescent tube 5 is turned on, the ambient temperature rises, and the optical sheets 3 and 4 expand, the expansion amount is absorbed by the restoring operation of the elastic plates 6 to 13 and the like. , 4 are kept pulled in the outward direction as they are and wrinkles are not generated on the surface. As a result, the generation of shadows due to wrinkles is eliminated. Further, the backlight device having this structure can sufficiently cope with an increase in size. Furthermore, even when the liquid crystal display device provided with the backlight device is enlarged, a stable image quality without uneven brightness can be obtained on the screen.

  In the above-described embodiment, the backlight device using the two optical sheets 3 and 4 is used. However, in the same manner for the backlight device using three or more optical sheets, the optical sheets are elastic plates. It is possible to configure so as to be locked. Also, since the screen is usually held vertically in a liquid crystal television, the elastic plate to which the upper edge of the optical sheets 3 and 4 is engaged is more elastic than the elastic plate to which the lower edge is engaged. A large load is applied by the weight of the optical sheets 3 and 4. For this reason, the elastic plate with which the edge of the upper end is engaged is strong, i.e., has a high restoring force when bent, so that it balances the tension of the elastic plate with which the edge of the lower end is engaged. It is preferable to make it.

  In the above-described embodiment, the elastic plates are arranged at all the edges in the four directions of the outer periphery. However, instead of the elastic plates, elasticity is provided on either one of the edges at both ends in the longitudinal direction or the edges at both ends in the short direction. It is also possible to use a plate made of a rigid body that does not have. In the above-described embodiment, the optical sheets 3 and 4 are engaged by disposing the elastic plates at the edges of both ends in the longitudinal direction or both ends in the short direction, but on the diagonal lines of the optical sheets 3 and 4. It is also possible to dispose an elastic plate on the outside and apply tension in the diagonally outward direction.

  The present invention can be used for a backlight device such as a display device in addition to a backlight device used for a liquid crystal display device such as a liquid crystal television.

1 is an external view of a liquid crystal television according to an embodiment of the present invention. 1 is an external view of a liquid crystal television according to an embodiment of the present invention. 1 is an external view of a liquid crystal television according to an embodiment of the present invention. It is a disassembled perspective view which shows the internal structure of a liquid crystal television. It is a disassembled perspective view which shows the internal structure of a liquid crystal television. It is the perspective view which took out and showed the backlight apparatus from FIG. It is an expanded sectional view of the AA line of FIG. It is an expanded sectional view of the BB line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight shield 1a Optical member holding | maintenance part 2 Diffusion plate 2a Notch 3 Optical sheet 3a Square hole 3b Notch 4 Optical sheet 4a Square hole 4b Notch 5 Fluorescent tube 6-13 Elastic plate 6a, 7a Check claw 14 Bezel 15 Screw 100 Liquid crystal panel 101 Front cabinet 102 Rear cabinet 103 Operation buttons 104 Speaker 105 Stand 110 Liquid crystal panel unit 111 Optical sheet 113 Upper lamp holder 114 Lower lamp holder 115 Lamp 116 Reflective sheet 117 Backlight chassis

Claims (4)

A rectangular diffusing plate is disposed in front of the light source, and the diffusing plate is substantially the same shape as the diffusing plate on the front surface of the diffusing plate. A hole,
An elastic plate having a longitudinal direction held substantially perpendicular to the optical sheet, a distal end engaged with the engagement hole, and a base end fixed to the side surface of the backlight device housing;
In the backlight device, the elastic plate is elastically deformed inward, the engagement hole is engaged with the tip of the elastic plate, and the optical sheet is supported by applying tension in the extension direction thereof.
When the illumination surface of the backlight device is held vertically, each optical sheet engages an elastic plate with an engagement hole formed in each of the opposite edge portions in the vertical direction, and the upper edge portion. A backlight device characterized in that a restoring force at the time of elastic deformation of the elastic plate installed in the panel is larger than a restoring force at the time of elastic deformation of the elastic plate installed at the lower edge portion. The backlight device according to claim 1,
The backlight device according to claim 1, wherein the engagement hole and the elastic plate engaged with the engagement hole are provided at both ends in either the longitudinal direction or the short direction of the optical sheet. The backlight device according to claim 1 or 2,
A backlight device, wherein a check claw projects from a portion of the elastic plate that has passed through the engagement hole outside the tip.   4. A liquid crystal display device comprising a liquid crystal panel disposed in front of the backlight device according to claim 1.

Images