JP2012141385A - Backlight chassis of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight chassis for supporting a backlight of a liquid crystal display device which has high torsional rigidity and strong resistance to shock.SOLUTION: The metal backlight chassis 9 for supporting a backlight arranged in a back surface side of a liquid crystal panel constituting a liquid crystal display device includes one or more beads 12 having one or more step portions 13 having different heights formed in a bottom surface portion thereof.

Description

  The present invention relates to a backlight chassis that supports a backlight of a liquid crystal display device.

In a liquid crystal display device, a backlight is disposed on the back surface of the liquid crystal panel, and an image is displayed by blocking or transmitting light emitted from the backlight for each pixel of the liquid crystal panel. .
In recent years, liquid crystal display devices such as liquid crystal televisions have been increased in screen size, and a standard liquid crystal television 32V type display unit has a size of about 400 mm × about 700 mm. The display portion is about 800 mm × about 1400 mm.
As the screen size has increased, the weight has increased, and in addition to the problem of transport, the demand for weight reduction has increased due to needs such as wall hanging.

Such a liquid crystal display device is disclosed in Patent Document 1, for example. In this liquid crystal display device, a backlight chassis is disposed on the back surface of the liquid crystal panel as a metal reflector having substantially the same area as the liquid crystal panel.
Since this backlight chassis has almost the same area as the display part of a liquid crystal television, it is one of the main causes of weight increase accompanying the increase in screen size, and the weight reduction directly leads to the weight reduction of the liquid crystal display device. . In addition, the thinning of the backlight chassis reduces the material cost of the backlight chassis, leading to a reduction in product manufacturing costs.

For small LCD TVs, a resin-made backlight chassis may be used. However, when the screen is enlarged, the backlight chassis cannot be increased in thickness in order to ensure the rigidity and strength of the backlight chassis, leading to a further increase in weight. Further, in the resin backlight chassis having a thickness of 3 to 4 mm, the heat generated by the backlight or the circuit board is trapped inside the device, leading to deterioration in device performance such as image quality deterioration and reliability.
Therefore, the backlight chassis is mainly manufactured by processing a metal plate such as a steel plate or an aluminum plate.

Thinning is progressing to reduce the weight of metal backlight chassis, but as the thickness is reduced, the backlight chassis is more likely to be distorted. Handling the chassis becomes difficult.
A plurality of circuit boards are disposed on the back surface of the backlight chassis. When these circuit boards are directly attached to the backlight chassis, there is a concern that the backlight chassis may be bent or deformed by the weight of the circuit board.

JP 2002-90736 A

However, in the technique described in Patent Document 1 described above, when a large impact is applied to the liquid crystal display device due to overturning or dropping, the backlight chassis and the circuit board are damaged due to large deflection of the backlight chassis. Or the backlight chassis may be permanently deformed, resulting in an unsolved problem of failure.
Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems, and when the backlight chassis is thinned, it is easy to handle in the manufacturing process such as assembly and transportation, and is directly attached to the backlight chassis. In addition to suppressing deflection and deformation due to the weight of the printed circuit board, it also suppresses large deflection and permanent deformation of the backlight chassis when a large impact is applied due to falling, dropping, etc. It is an object of the present invention to provide a backlight chassis for a liquid crystal display device that can meet the demands for making a display.

In order to achieve the above object, a backlight chassis of a liquid crystal display device according to one embodiment of the present invention is a metal backlight that supports a backlight disposed on the back side of a liquid crystal panel constituting the liquid crystal display device. The light chassis is characterized in that it includes at least one bead in which one or more step portions having different heights are formed on the bottom surface.
In the backlight chassis of the liquid crystal display device according to another aspect of the present invention, the bead is formed by press working.

In the backlight chassis of the liquid crystal display device according to another aspect of the present invention, the maximum height of the bead is set to 2 mm or more, and the height of the stepped portion is ¼ or more of the maximum height. It is characterized by being set to a range of 3/4 or less.
Moreover, the backlight chassis of the liquid crystal display device according to another embodiment of the present invention is characterized in that it is made of a steel plate having a thickness of less than 1.0 mm.

A backlight chassis of a liquid crystal display device according to another embodiment of the present invention is characterized in that a cross section of a ridge line portion where a bottom surface and a side surface intersect with each other is an arc shape having a curvature radius of 10 mm or more.
A backlight chassis of a liquid crystal display device according to another aspect of the present invention is characterized in that an arc-shaped cross section of the ridge line portion is provided continuously along the outer periphery of the bottom surface of the backlight chassis.

  According to the present invention, when the backlight chassis is thinned, it is easy to handle in the manufacturing process such as assembly and transportation, and the bending and deformation due to the weight of the circuit board directly attached to the backlight chassis are suppressed. To provide a backlight chassis that can respond to the demand for weight reduction of large-sized liquid crystal display devices by suppressing large deflection and permanent deformation of the backlight chassis when a large impact is applied due to falling or dropping. Can do.

1 is a schematic exploded perspective view showing a liquid crystal display device to which the present invention can be applied. 1 is a front view showing a backlight chassis according to the present invention. It is sectional drawing on the AA line of FIG. It is sectional drawing on the BB line of FIG. It is a cross-sectional enlarged view of embossing. It is a front view which shows the comparative example which has a bead without a level | step-difference part. It is a front view which shows the comparative example without a bead. It is explanatory drawing which shows torsional rigidity evaluation conditions. It is a figure which shows the state which fixed the backlight chassis in the case of performing an impact test to aluminum frames, Comprising: (a) is a front view which expands and shows a part, (b) is a cross section which expands and shows a part FIG. 4C is an enlarged plan view of the fixing claw, and FIG. 4D is an enlarged side view of the fixing claw. It is a figure which shows other embodiment of this invention, Comprising: (a) is a front view, (b) is a cross-sectional view, (c) is a longitudinal cross-sectional view. It is a figure which shows other embodiment of this invention, Comprising: (a) is a front view, (b) is a cross-sectional view, (c) is a longitudinal cross-sectional view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic exploded perspective view showing a liquid crystal display device such as a liquid crystal television and a liquid crystal monitor to which the present invention can be applied.
The liquid crystal display device 1 has a front cover 2, a color filter 3, a liquid crystal panel 4, a diffusion plate 5, a polarizing plate 6, for example, a backlight 7 composed of CCFL (cold cathode tube) from the front side, and the light from the backlight 7. The liquid crystal panel 4 includes at least a reflecting plate 8, a backlight 7, a backlight chassis 9 that supports the reflecting plate 8, a circuit board 10 that is mounted on the back side of the backlight chassis 9, and a back cover 11.

  As shown in FIG. 2, the backlight chassis 9 is formed by bending an electrogalvanized mild steel plate having a thickness of, for example, 0.8 mm into a box shape with the front surface opened by pressing, and includes a bottom plate portion 9a and a bottom plate portion 9a. The side plate portions 9b to 9e are formed by bending the upper, lower, left and right end portions of the face plate portion 9a forward, and the flange portions 9f to 9i are formed by bending the front step portions of the side plate portions 9b to 9e outward. .

  The bottom plate portion 9a is formed in parallel so that two beads 12 extending in the up-down direction with a predetermined interval in the left-right direction have a convex shape protruding to the front side. As shown in FIG. 3, each bead 12 is formed by pressing so as to be inclined and inclined side walls 12 a and 12 b inclined obliquely inward from the front surface of the bottom plate portion 9 a, and front side ends of these inclined side walls 12 a and 12 b. It is comprised with the top | upper surface 12c which connects between parts.

Each bead 12 is formed with a step 13 that suppresses the expansion of the width W of the opening of the bead 12 at a position that divides the length in the vertical direction into, for example, three equal parts. As shown in FIG. 4, these stepped portions 13 are stepped portions connecting the inclined side walls 13 a and 13 b inclined obliquely inward from the front surface of the bottom plate portion 9 a and the front side end portions of the inclined side walls 13 a and 13 b. It is comprised with the top | upper surface 13c. The bead 12 is set to a height h2 that is lower than the bead height h1.
Here, the height h2 of the stepped portion 13 is preferably set to ¼ or more and ¾ or less of the maximum height h1 of the bead 12. More preferably, it is set to 1/3 or more and 2/3 or less.

When the height h2 of the stepped portion 13 is set to be less than ¼ of the maximum height h1 of the bead 12, stress concentrates on the stepped portion 13 and is likely to buckle locally. Moreover, when the height h2 of the stepped portion 13 exceeds 3/4 of the maximum height h1 of the bead 12, the effect of suppressing the expansion of the width W of the opening of the bead 12 is impaired.
The top surface of the bead 12 includes a top surface 12c having a maximum height h1, a top surface 13c having a step height h2, and a wall portion connecting them, except for holes and step portions for attaching other parts. It is preferable to be constituted by a smooth surface.

  Further, if the number of beads 12 is one or more, it is effective to ensure the rigidity of the backlight chassis 9, but if the size of the backlight chassis 9 is increased, it is more effective to provide a plurality of beads 12. It is preferable to determine the arrangement of the beads 12 in consideration of the positional relationship that does not interfere with the components attached to the backlight chassis 9. Moreover, since the metal mold | die at the time of a press becomes complicated, if it increases too much, it will become economically disadvantageous. For this reason, the number of beads 12 is more preferably about 2 to 4.

  Furthermore, the maximum height h1 of the bead 12 is preferably 2 mm or more in order to ensure the rigidity of the bottom plate 9a. Further, the maximum height of the bead 12 that can be stretch-formed without cracking by pressing depends on the material of the metal plate. For example, in the case of a steel plate having a thickness of 0.8 mm or less, the upper limit is about 15 mm, but it can be adjusted by the width of the bead 12, the angle of the wall, the radius of curvature of the ridgeline, and further by the pressing process. In order to suppress surface distortion after press working, 10 mm or less is more suitable.

The width W of the bead 12 is preferably set to 10 mm or more in order to improve the rigidity of the backlight chassis 9. When the size of the backlight chassis 9 is increased, it is effective that the bead width W is wider. However, the arrangement of the beads 12 is determined in consideration of the positional relationship that does not interfere with the components attached to the backlight chassis 9. The bead width is preferably set to 50 mm or less.
The length of the bead 12 is preferably set to 1/2 or more of the backlight chassis dimension in the length direction of the bead 12 in order to ensure the rigidity of the backlight chassis 9. More preferably, it is 80% or more of the backlight chassis dimension in the length direction of the bead 12.

  The length of the stepped portion 13 may be at least as long as it can be stretched by press working, and is preferably set to 5 mm or more. Moreover, it is preferable to set it to 3 times or less of the width W of the bead 12. When the stepped portion 13 becomes longer, the proportion occupied by the lower portion of the bead height h1 increases, and there is a concern that the effect of improving the rigidity of the backlight chassis 9 may be impaired. Therefore, it is more preferable to set the width W of the bead 12 to be twice or less. good.

The width of the stepped portion 13 may be the same as the width W of the bead maximum height portion.
If the number of the step portions 13 is one or more per bead 12, it is effective for suppressing deformation at the time of impact. It is more preferable that the length of the bead 12 is longer, since the spread of the inclined side walls 12a and 12b of the bead 12 can be further suppressed by providing a plurality of step portions 13. However, if the number of the stepped portions 13 is excessively large, the proportion of the low bead height is increased, and there is a concern that the effect of improving the rigidity of the backlight chassis 9 may be impaired. It is preferable that

  Further, the six truncated cone-shaped embosses 14 provided at the center between the beads 12 of the bottom plate 9a shown in FIG. 2 are for attaching the circuit board 10, and are shown in the enlarged sectional view of FIG. Thus, it is comprised by the embossed side part 14a protruded from the bottom face board part 9a to the back side, and the top | upper surface part 14b which obstruct | occludes the upper surface of this embossed side part 14a, for example, the outer diameter 30mm in the bottom face plate part 9a, The surface portion 14b has an outer diameter of 10 mm and a height of 10 mm, and a screw fixing hole is formed at the center of the top surface portion 14b.

Furthermore, as shown in FIG. 10, in the metal backlight chassis 9 having an opening on one side, the cross-section of the ridge line portion where the bottom plate portion 9 a and the side plate portions 9 b to 9 e intersect has an arc shape with a radius of 10 mm or more. By using a curved surface, the amount of displacement at the time of impact can be suppressed.
As the radius of curvature R of the cross-section of the ridge line portion increases, the residual deformation decreases. This is presumed to be because stress that tends to concentrate on the ridge line portion at the time of impact is dispersed as the curvature radius R increases.
In particular, as shown in FIG. 11, it is desirable for the four corners between the side plate portions 9b to 9e to be continuous with an arc surface along the outer periphery of the bottom surface in order to suppress deformation due to the load, and further to the flange-shaped frame. Furthermore, the shape which continues along the outer periphery is more preferable.

In addition, the flange that is expanded outward from the front end of the side face has a higher rigidity when the end is further folded back to the bottom side, suppressing deflection and deformation due to the weight of the directly mounted circuit board, etc. It is suitable for doing.
In the backlight chassis 9 of the present invention, a thin and lightweight backlight chassis can be efficiently manufactured at low cost by pressing a metal plate.

In particular, it is more preferable to obtain the shape of the backlight chassis of the present invention by producing the bottom portion by overhanging and bending the outer peripheral wall portion, or by combining the bottom portion overhanging and the outer peripheral wall portion.
The material of the metal plate is not particularly limited as long as there is no problem in forming processing, and mild steel plates, high-tensile steel plates, stainless steel plates, aluminum plates, and aluminum alloy plates can be used.

Furthermore, plating for preventing corrosion and surface treatment and coating as required may be applied. For example, a steel sheet that is subjected to chemical conversion treatment that imparts functions such as fingerprint resistance, corrosion resistance, and lubrication to the surface after electroplating or hot dipping of pure zinc or zinc alloy on the surface is suitable.
Further, the plate thickness can be arbitrarily determined as necessary, but in order to reduce the weight of the TV chassis, it is preferably less than 1.0 mm when a steel plate is used. More preferably, 0.8 mm or less where the effect of the present invention becomes remarkable is suitable.
In the case of an aluminum plate, it is preferably less than 1.5 mm.

Example 1
A liquid crystal television backlight chassis (W720 mm × H400 mm × D25 mm) equivalent to 32 inches was prototyped by press working.
Three types of electrogalvanized mild steel sheets with a thickness of 1.0, 0.8, and 0.6 mm were used as metal plates, and inventive examples 1 to 8 and comparative examples 9 to 13 of the present invention were formed by stretch forming and bending. processed.
The shape of the obtained backlight chassis is the same as that shown in FIG. 2 for the inventive examples 1 to 8, and the comparative examples 9 and 10 have the beads 12 as shown in FIG. The step portion is not formed, and Comparative Examples 11 to 13 have a configuration in which the bead 12 itself is not formed as shown in FIG.

Thickness of each invention example 1-8, bead width, bead maximum height h1, height h2 and length of the stepped portion, height ratio (= height of the stepped portion / maximum height of the bead), Table 1 below shows the plate thickness, bead width and bead maximum height of Comparative Examples 9 and 10, and the plate thicknesses of Comparative Examples 11-13.
The six frustoconical embossments placed in the center are for mounting the circuit board. The bottom surface has an outer diameter of 30 mm, the top surface has an outer diameter of 10 mm, and a height of 10 mm. A hole was made.
The rigidity and impact resistance of these backlight chassis were evaluated by the following two methods.

Evaluation 1) Torsional Rigidity Measurement As shown in FIG. 8, when a pair of diagonal positions located at opposite corners of the backlight chassis 9 are fixedly supported, and the remaining pair of opposite corner positions are simultaneously lifted by 20 mm. The load was measured.
The load obtained with a backlight chassis having a plate thickness of 1.0 mm and no beads (Comparative Example 13) was defined as 100, and the result of relative comparison was defined as torsional rigidity.

Evaluation 2) Impact test An impact test was performed according to JIS C60068-2-27 (1995).
The backlight chassis 9 was placed on a horizontal surface plate so that the back surface was on the upper side, and the height of the center point was measured to 1/10 mm with a laser displacement meter.
A 200 mm × 300 mm × 1.6 mmt resin substrate 10 (total weight 1000 g) soldered with various electronic components was fixed to the top surface portion 14b of the six embosses 14 at the center of the bottom surface of the backlight chassis 9 with M3 screws.

The backlight chassis 9 to which the substrate 10 is attached is screwed to an aluminum frame 21 as shown in FIG. 9, and the speed of the aluminum frame 21 is half a sine wave and the front side (chassis opening) from the back side. An impact with an action time of 11 ms and a peak acceleration of 500 m / s ² was applied once in the direction.
Thereafter, the substrate 10 is removed from the backlight chassis 9, and the backlight chassis 9 is placed on a horizontal surface plate in the same manner as before the impact is applied. The height of the center point is measured with a laser displacement meter, and before and after the impact. The change in height was obtained as the amount of displacement.
The obtained results are also shown in Table 1 below.

As is clear by comparing Comparative Examples 11 to 13, when the bead 12 is thinned, the torsional rigidity of the backlight chassis 9 decreases as the thickness decreases, and the amount of displacement due to impact decreases as the thickness decreases. To increase.
When a bead is added to the thinned backlight chassis 9, as shown in Comparative Examples 9 to 10, the torsional rigidity is improved as compared with Comparative Examples 11 to 12 without the bead, but the displacement due to the impact is increased. It became.

On the other hand, in Invention Examples 1 to 8 of the present invention, by providing the step portion 13 in the bead 12, the displacement amount due to the impact is reduced while maintaining the torsional rigidity substantially the same, and both of them are compatible. Has succeeded.
From this, according to the present invention, it is clear that the backlight chassis 9 can be thinned and can be significantly reduced in weight.

(Example 2)
A backlight chassis (W940 mm × H530 mm × D25 mm) of a liquid crystal television equivalent to 42 inches larger than Example 1 was prototyped by press working.
Two types of hot-dip galvanized steel sheets with a thickness of 1.0 and 0.7 mm are used as metal plates, and inventive examples 14 to 18 and comparative examples 19 to 21 of the present invention are processed by stretch forming, bending forming and drawing. did.
The shape of the obtained backlight chassis 9 is the predetermined curvature radii R0.5 mm and 5.0 mm at the ridges between the bottom plate 9 a and the side plates 9 b to 9 e of the backlight chassis 9 in Invention Examples 14 to 17. A circular arc surface 31 of 10.0 mm and 20.0 mm is formed. FIG. 10 shows an example of a curvature radius of 10 mm.

On the other hand, as for Invention Example 18, as shown in FIG. 11, an arcuate surface 31 having a radius of curvature of 20 mm is formed on the ridge line portion between the bottom plate 9a and the side plates 9b-9e of the backlight chassis 9 by drawing. At the same time, arcuate surfaces 32 having a radius of curvature of about 25 mm are formed at the four corners where the side plate portions 9b to 9e are joined.
On the other hand, in Comparative Example 19, the bead 12 is provided but the stepped portion 13 is not provided, and an arc portion having a radius of curvature of 0.5 mm is provided at the ridge line portion between the bottom plate portion 9a and the side plate portions 9b to 9e. .

Further, in Comparative Examples 20 and 21, the bead 12 itself was not formed, and an arc portion having a curvature radius of 0.5 mm was provided at the ridge line portion between the bottom plate portion 9a and the side plate portions 9b to 9e.
Inventive Examples 14 to 18 and Comparative Examples 19 to 21 were also subjected to the torsional rigidity test shown in FIG. 8 and the impact test using the aluminum frame shown in FIG. The results are shown in Table 2.

As is apparent from Table 2, by providing the step portion 13 on the bead 12, the impact resistance is greatly improved while maintaining the torsional rigidity substantially the same (Invention Example 14), and the curved surface of the ridge line portion is further improved. In Invention Examples 16 to 17 in which the radius of curvature R of each is 10 mm or more, the amount of displacement at the time of impact is further suppressed.
In Invention Example 18 in which the curved surface of the ridge line portion is continued to the corners of the four corners of the backlight chassis 9 by the circular arc surface, the amount of displacement at the time of impact has been further significantly reduced.
From the above results, it is clear that the backlight chassis can be thinned and greatly reduced in weight according to the present invention.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 2 ... Front cover, 3 ... Color filter, 4 ... Liquid crystal panel, 5 ... Diffusing plate, 6 ... Polarizing plate, 7 ... Backlight, 8 ... Reflecting plate, 9 ... Backlight chassis, 9a ... Bottom Face plate portion, 9b to 9e ... Side plate portion, 9f to 9i ... Flange portion, 10 ... Circuit board, 11 ... Back cover, 12 ... Bead, 12a, 12b ... Inclined sidewall, 12c ... Top surface, 13 ... Stepped portion, 13a , 13b ... inclined wall, 13c ... stepped surface, 14 ... embossed, 14a ... embossed side surface, 14b ... top surface, 21 ... aluminum frame, 31, 32 ... arc surface

Claims (6)

A metal backlight chassis that supports a backlight disposed on the back side of a liquid crystal panel constituting a liquid crystal display device,
A backlight chassis for a liquid crystal display device, comprising at least one bead having one or more step portions having different heights on a bottom surface portion.   The backlight chassis of the liquid crystal display device according to claim 1, wherein the bead is formed by press working.   The maximum height of the bead is set to 2 mm or more, and the height of the stepped portion is set to a range of 1/4 or more and 3/4 or less of the maximum height. Or a backlight chassis of the liquid crystal display device according to 2;   The backlight chassis of the liquid crystal display device according to any one of claims 1 to 3, wherein the backlight chassis is made of a steel plate having a thickness of less than 1.0 mm.   5. The backlight chassis of a liquid crystal display device according to claim 1, wherein a cross section of the ridge line portion where the bottom surface and the side surface intersect is an arc shape having a curvature radius of 10 mm or more.   6. The backlight chassis of a liquid crystal display device according to claim 5, wherein an arc-shaped cross section of the ridge line portion is provided continuously along the outer periphery of the bottom surface of the backlight chassis.

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