JP4838508B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device having a sidelight-type backlight having a light source as a cold cathode tube. More specifically, the present invention relates to an electromagnetic wave radiated from a hot-side lead wire when a cold cathode tube is driven at high frequency alternating current. The present invention relates to a technique for preventing display defects.

  In a transmissive or transflective liquid crystal display device, a backlight unit 2 is provided on the back side of the liquid crystal panel 1 as shown in FIGS. In this example, the backlight unit 2 is a side light (edge light) type, and includes a light guide plate 21 made of, for example, polycarbonate and a light source 22 that emits light from the side of the light guide plate 21 as a basic configuration. ing.

  In the case of a liquid crystal display device for small equipment such as a cellular phone, a light emitting diode is used for the light source 22. For example, in a large equipment such as a car navigation system, as described in Patent Document 1, the light source 22 is used. For example, a cold cathode tube (CCFT) having a large light emission amount is used.

  The cold cathode tube includes a straight tube type, an L-shaped tube, a U-shaped tube, and the like. In this example, as shown in FIG. 8, an L-shaped cold cathode tube is used as the light source 22. The cold cathode tubes are disposed along two adjacent side surfaces (light incident surfaces 21a and 21b) of the light guide plate 21 (hereinafter, the cold cathode tubes are denoted by reference numeral 22 as a light source).

  As shown in FIG. 7, a light reflecting sheet 23 is arranged on the back surface 21 e side of the light guide plate 21 in order to improve the light irradiation efficiency with respect to the liquid crystal panel 1, but in order to further increase the light irradiation efficiency, the light reflecting sheet 23. In addition, bent pieces 231 and 232 are formed so as to cover the side surfaces (reverse light incident surfaces 21c and 21d) opposite to the light incident surfaces 21a and 21b.

  In addition, an optical film group 24 including a light diffusion sheet, a prism sheet (brightness enhancement sheet), and the like is laminated on the light irradiation surface 21f side of the light guide plate 21 with respect to the liquid crystal panel 1, and a backlight including these components. The unit 2 is disposed on the back side of the liquid crystal panel 1 in a state of being housed in the housing recess 31 of the unit case 3 whose upper surface is open.

  Normally, the cold cathode tube 22 is driven by high-frequency alternating current by an inverter power supply (not shown). In particular, in the case of an L-shaped tube type, the cold cathode tube 22 is connected to the electrode terminals 221 and 222 of the cold cathode tube 22 as shown in FIG. The hot side lead wire 223 and the cold side (ground side) lead wire 224 are wired in the unit case 3 along the light incident surfaces 21c and 21d.

  9 shows the wiring state of the hot-side lead wire 223 in the unit case 3. When the cold cathode tube 22 is driven, an electromagnetic wave (electromagnetic field) is generated from the hot-side lead wire 223 by a high-frequency current. An electromagnetic wave is also generated from the cold cathode tube 22. This may cause a flicker (beat) phenomenon in which the display on the liquid crystal panel 1 flickers.

  This flicker phenomenon occurs regardless of whether it is an STN liquid crystal panel or a TFT liquid crystal panel. However, in the case of a TFT liquid crystal panel, the common electrode on the counter substrate side is a so-called solid electrode, and is easily affected by electromagnetic waves. (VCOM voltage) becomes unstable, and the flicker phenomenon appears remarkably.

  In order to prevent this, for example, a metal shield cover 4 having a frame-shaped shield plate 42 around the opening 41 for light irradiation is placed on the unit case 3, and the cold cathode tube 22 and the hot lead wire 223 are removed. The radiated electromagnetic wave is shielded. Since the cold side lead wire 224 is connected to the ground (ground) of the power source, no electromagnetic waves are generated from the cold side lead wire 224.

JP 2003-195295 A

  However, the width of the shield plate 42 of the shield cover 4 is naturally limited in relation to the light irradiation area of the backlight unit 2. Therefore, when the hot-side lead wire 223 is wired in the vicinity of the shield plate 42 as shown by a chain line A in FIG. 9, the electromagnetic wave radiated from the hot-side lead wire 223 is shielded by the shield plate 42. However, when the hot side lead wire 223 is placed away from the shield plate 42 as shown by a solid line in FIG. 10 due to vibration or the like, electromagnetic waves radiated from the hot side lead wire 223 are transmitted from the shield plate 42. Leakage occurs, and a part of the display on the liquid crystal panel 1 is disturbed by the flicker phenomenon.

  For the cold cathode tube 22, a rubber cap (not shown) covering the electrode terminals 221 and 222 is tightly fitted between the light guide plate 21 and the inner wall of the unit case 3, whereby the shield plate Since it is held in the vicinity of 42, there is no position shift unlike the hot lead wire.

  Accordingly, an object of the present invention is caused by misalignment of the hot lead wire in a liquid crystal display device in which the hot lead wire connected to the cold cathode tube of the backlight unit is wired along the side surface of the light guide plate. The object is to prevent display defects of the liquid crystal panel due to leakage electromagnetic waves.

In order to solve the above problems, the invention described in claim 1 includes a liquid crystal panel and a backlight unit disposed on the back side of the liquid crystal panel in a state of being housed in a unit case having an open upper surface. The backlight unit is a side light type in which a light source is disposed along a predetermined side surface that is a light incident surface of a light guide plate, and a cold cathode tube driven by high-frequency alternating current is used as the light source, At least a part of the hot lead wire of the tube is wired along the side surface of the light guide plate in the unit case, and an electromagnetic wave radiated from the hot lead wire is applied to a part of the upper surface opening of the unit case. In the liquid crystal display device covered with a shielding plate for shielding, the hot lead wire is placed in the unit case near the shielding plate. Is provided with a lead wire supporting means for supporting the positioning,
The lead wire support means comprises a foldable support plate made of paper or synthetic resin as a base material, and the support plate is bent on the support plate so that the hot-side lead wire is closer to the shield plate side. It is characterized in that a support portion for supporting the height position is formed .

According to a second aspect of the present invention, in the first aspect, the support portion is a support base that supports the hot-side lead wire by bending the support plate in a step shape .

  The invention according to claim 3 is the bent piece according to claim 2, which is bent along the side surface of the light guide plate other than the light incident surface on the light reflecting sheet disposed on the bottom surface side of the light guide plate. Is provided, and the support plate is formed with an upright piece held by the bent piece.

  According to a fourth aspect of the present invention, in the third aspect, the upright piece is held by the bent piece by being inserted between the bent piece and a side surface of the light guide plate. At least the surface facing the side surface is a light reflecting surface.

  A fifth aspect of the present invention is characterized in that, in the third aspect, the upright piece is held by an adhesive on the outer surface side of the bent piece.

  A sixth aspect of the present invention is characterized in that, in the second aspect, the support plate is formed integrally with a light reflecting sheet disposed on a bottom surface side of the light guide plate.

According to the first aspect of the present invention, the hot-side lead wire is supported by the lead wire support means at a predetermined height position near the shield plate side, that is, within the shielding region of the shield plate. It is possible to prevent display defects on the liquid crystal panel due to leakage electromagnetic waves caused by the shift. In addition, since the lead wire support means is a foldable support plate made of paper or synthetic resin as a base material, there is no deterioration over time due to temperature, humidity, etc., and high reliability support is possible and assembly work is also possible. It can be done efficiently.

According to the second aspect of the present invention, the hot side lead wire can be supported in a plane because the support portion for supporting the hot side lead wire can be supported by bending the support plate stepwise. In addition to being able to support stably without being influenced by the above, assembly work is also easy.

In addition, when the light reflecting sheet disposed on the bottom side of the light guide plate is provided with a bent piece that is bent along the side surface of the light guide plate other than the light incident surface, the support plate holds the bent piece. According to the invention described in claim 3 , in which the standing piece is formed, the support plate can be applied retrospectively without changing the existing backlight unit.

  The invention according to claim 4, wherein when the upright piece is inserted and held between the bent piece and the side surface of the light guide plate, at least a surface of the upright piece facing the side surface of the light guide plate is a light reflecting surface. Accordingly, the support plate can be held without impairing the light irradiation efficiency on the liquid crystal panel.

  In addition, according to the invention described in claim 4 in which the upright piece is held by the adhesive on the outer surface side of the bent piece, the mounting operation of the support plate can be easily performed, and the same as in claim 4. The light irradiation efficiency to the liquid crystal panel is not impaired.

  According to the invention of claim 6, wherein the support plate is formed integrally with the light reflecting sheet disposed on the bottom side of the light guide plate, the manufacturing cost and assembly workability are further improved, Since the number of parts is reduced, parts management is also facilitated.

  Next, a preferred embodiment of the present invention will be described with reference to FIGS. 1 to 6, but the present invention is not limited to this. In the following description of the embodiment, except for the lead wire support means for supporting the hot-side lead wire 223 on the side opposite to the light-receiving surface 21c of the light guide plate 21, the other components will be described with reference to FIGS. Since there is no need to change the conventional example described, the description thereof is omitted.

  That is, also in this embodiment, as shown in FIG. 8, an L-shaped cold cathode tube 22 is used as the light source of the backlight unit 2, and the hot side connected to the electrode terminals 221 and 222 is used. The lead wire 223 and the cold-side lead wire 224 are routed along the anti-light receiving surfaces 21 c and 21 d of the light guide plate 21.

  Further, as shown in FIG. 7, a light reflecting sheet 23 is disposed on the back surface 21e side of the light guide plate 21, and an optical film including a light diffusion sheet and a prism sheet on the front surface 21f side of the light guide plate 21. A group 24 is placed. The upper opening of the unit case 3 is covered with, for example, a metal shield cover 4 having a frame-shaped shield plate 42 around the opening 41 for light irradiation.

  First, a first embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a cross-sectional view similar to FIG. 9 showing the wiring portion of the hot-side lead wire 223, and FIG. 2 is a perspective view showing a lead wire support means for the hot-side lead wire 223, which is the main part of the present invention. is there.

  The light reflecting sheet 23 is a bendable sheet made of paper or synthetic resin as a base material. The light reflecting sheet 23 is bent so as to cover the anti-light incident surfaces 21c and 21d of the light guide plate 21 as in the conventional example. The pieces 231 and 232 are formed. In this embodiment, one bent piece 231 is integrally formed with a lead wire supporting means 5A for supporting the hot-side lead wire 223.

  That is, the lead wire support means 5A includes the bent portion 231 of the light reflecting sheet 23 as an upstanding piece 51. The upstanding piece 51 and the upper end of the upstanding piece 51 are stepped toward the inner wall surface of the unit case 3. And a bent leg piece 52.

  On the leg piece 52, a support base (support part) 52a for supporting the hot-side lead wiring 223 is formed by bending a part of the leg piece 52 in a step shape. The height of the support base 52a is set such that electromagnetic waves radiated from the hot-side lead wiring 223 do not leak from the shield plate 42 to the liquid crystal panel 1 side, but the hot-side lead wiring 223 with respect to the shield plate 42. Is preferably as close as possible.

  In order to ensure the support of the hot-side lead wiring 223, it is preferable that the lower end 52 b of the leg piece 52 is brought into contact with the bottom plate 32 of the unit case 3. In some cases, the hot-side lead wiring 223 may be fixed to the support base 52a with an adhesive. In order to improve the assembly workability, it is preferable to provide a perforation 53 in advance at the bent portion as shown in FIG.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the lead wire supporting means 5B is configured to be separated from the light reflecting sheet 23. This is so that it can be applied later to the existing backlight unit 2.

  The lead wire support means 5B is made of a foldable support plate made of paper or synthetic resin as a base material, and the standing piece 51 formed separately from the bent portion 231 of the light reflecting sheet 23, and the standing piece 51 A leg piece 52 bent stepwise from the upper end toward the inner wall surface of the unit case 3 is provided, and a support base 52a similar to that of the first embodiment is formed on the leg piece 52 by bending.

  The lead wire supporting means 5B can hold the upright piece 51 on the light reflecting sheet 23 side by inserting it between the anti-light incident surface 21c of the light guide plate 2 and the bent portion 231 of the light reflecting sheet 23. In this case, since at least the surface of the upright piece 51 that faces the light incident surface 21c is a light reflecting surface, the surface becomes an alternative to the light reflecting surface by the bent portion 231 of the light reflecting sheet 23. The light irradiation efficiency to the panel 1 is not impaired.

  Next, a third embodiment of the present invention will be described with reference to FIG. The lead wire support means 5C in the third embodiment is formed by folding a foldable support plate made of paper or synthetic resin as a base material into a U-shape.

  That is, the lead wire support means 5C has a pair of leg pieces 52, 52 that are arranged in parallel with the same length, and a support base 52a that is bridged between the upper ends of the leg pieces 52, 52. Between the bent portion 231 and the inner wall surface of the unit case 3.

  The lead wire support means 5C can be applied later to the existing backlight unit 2 in the same manner as the lead wire support means 5B in the second embodiment, but is not easily moved by vibration or impact. For example, it is preferably fixed to the bent portion 231 of the light reflecting sheet 23 with the adhesive 54. In addition, you may fix to the inner wall surface side of the unit case 3 with the adhesive material 54. FIG.

  Thus, according to the present invention, the hot lead wire 223 is supported in the vicinity of the shield plate 42 by the lead wire supporting means 5 (5A to 5C), and the hot lead wire 223 is on the bottom plate 32 side of the unit case 3. To prevent it from falling off. Therefore, the electromagnetic wave radiated from the hot lead wire 223 does not leak from the shield plate 42 to the liquid crystal panel 1 side, and a stable liquid crystal display without flicker phenomenon can be realized.

  The lead wire support means 5 is simply formed by forming a perforation 53 as a fold line on a light-reflective film sheet or a foldable support plate made of paper or synthetic resin, and bending it along the perforation 53. Since it can be formed, it is advantageous in terms of workability.

  The above has described each configuration example of the lead wire support means 5 according to the present invention based on the illustrated example. However, the shape and configuration of the lead wire support means 5 are not limited to the above embodiment, and the hot-side lead wire 223 is shielded. An appropriate shape can be selected as long as it can be supported in the vicinity of the plate 42.

  For example, as shown in FIG. 5, the upper end of the bent portion 231 of the light reflecting sheet 23 can be extended, and the extended portion can be bent into a V shape to form the support portion 55 of the hot-side lead wire 223. The V-shaped support portion 55 can be formed separately from the bent portion 231 of the light reflecting sheet 23. In that case, the upright piece 51 is connected to at least one end of the V-shaped support portion 55 as in the second embodiment described with reference to FIG. 3, and the upright piece 51 is folded on the light reflecting sheet 23. What is necessary is just to hold | maintain at the music part 231 side.

  As another example, as shown in FIG. 6, the leg piece 52 connected to the upper end of the bent portion 231 of the light reflecting sheet 23 has its lower end 52 b directed toward the corner of the bottom plate 32 of the unit case 3. The hot-side lead wire 223 can be supported by the inclined surface. Also in this example, the leg piece 52 is used as a simple plate material, or the upright piece 51 is connected to the plate material, and is disposed obliquely between the bent portion 231 of the light reflecting sheet 23 and the inner wall surface of the unit case 3. Such a mode may be included in the present invention.

Sectional drawing which shows typically the lead wire support part which concerns on 1st Embodiment of this invention. The perspective view which shows the lead wire support part of the said 1st Embodiment. Sectional drawing which shows typically the lead wire support part which concerns on 2nd Embodiment of this invention. Sectional drawing which shows typically the lead wire support part which concerns on 3rd Embodiment of this invention. Sectional drawing which shows typically the lead wire support part which concerns on the modification of this invention. Sectional drawing which shows typically the lead wire support part which concerns on another modification of this invention. The perspective view which shows the structural example of the conventional liquid crystal display device typically. The top view which shows typically the structural example of the backlight unit contained in the said conventional liquid crystal display device. Explanatory drawing which shows typically the wiring state of the hot side lead wire in the said conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight unit 21 Light-guide plate 21a, 21b Light incident surface 21c, 21d Anti-light incident surface 22 Cold cathode tube 221, 222 Electrode terminal 223 Hot side lead wire 224 Cold side lead wire 23 Light reflecting sheet 231,232 Bending Piece 24 Optical film group 3 Unit case 31 Storage recess 32 Bottom plate 4 Shield cover 41 Opening 42 Shield plate 5 Lead wire support means 51 Standing piece 52 Leg piece 52a Support base 53 Perforation

Claims (6)

A liquid crystal panel, and a backlight unit disposed on the back side of the liquid crystal panel in a state of being housed in a unit case having an open upper surface, the backlight unit being a light incident surface of the light guide plate A side light type in which a light source is arranged along the side surface of the cold-cathode, and a cold-cathode tube driven by high-frequency alternating current is used as the light source, and at least a part of the hot-side lead wire of the cold-cathode tube is in the unit case. In the liquid crystal display device wired along the side surface of the light guide plate and covered with a shield plate that shields electromagnetic waves radiated from the hot lead wire on a part of the upper surface opening of the unit case.
In the unit case, lead wire support means for supporting the hot side lead wire at a predetermined height position near the shield plate side is provided ,
The lead wire support means comprises a foldable support plate based on paper or synthetic resin,
The liquid crystal display device , wherein the support plate is formed with a support portion that is bent to support the hot-side lead wire at a predetermined height near the shield plate . The liquid crystal display device according to claim 1, wherein the support portion is a support base that supports the hot-side lead wire by bending the support plate in a step shape . The light reflecting sheet disposed on the bottom side of the light guide plate is provided with a bent piece that is bent along the side surface of the light guide plate other than the light incident surface, and the bent piece is provided on the support plate. The liquid crystal display device according to claim 1 , further comprising an upright piece that is held by the liquid crystal display.   The upright piece is held by the bent piece by being inserted between the bent piece and the side surface of the light guide plate, and at least the surface of the upright piece facing the side surface is a light reflecting surface. The liquid crystal display device according to claim 3.   The liquid crystal display device according to claim 3, wherein the standing piece is held by an adhesive on an outer surface side of the bent piece. The liquid crystal display device according to claim 1 , wherein the support plate is formed integrally with a light reflecting sheet disposed on a bottom surface side of the light guide plate.

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