JP2004279864A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which prevents the occurrence of deflection in sheets and decreases display defects even in either case the device is placed vertically or horizontally. <P>SOLUTION: The liquid crystal display device 10 is equipped with the translucent sheets 50b of an approximately rectangular shape formed with pores 50c to 50h across adjacent two sides and a back light unit 21 formed with protrusions 22a to 22c, 22e and 22f loosely fitted into the pores 50c to 50e, 50g and 50h. The pores 50c to 50e, 50g and 50h are formed to a regular triangle having one side parallel to the sides of the sheets 50b at which the pores are formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmissive liquid crystal display device having a backlight.
[0002]
[Prior art]
Liquid crystal display devices include a transmission type having a backlight and a reflection type using a reflected light such as a natural light or a room light without a backlight. Here, the transmissive backlight includes a direct type, a sidelight type, and the like. A large-screen liquid crystal display device mainly employs a direct type. The direct backlight is a surface light source in which a plurality of cold cathode tube lamps are arranged directly below a liquid crystal panel.
[0003]
On the other hand, a sidelight-type backlight is configured by a light-collecting unit including a lamp and a lamp holder having a reflector, and a light-guiding unit that guides light. The condensing section efficiently outputs the irradiation light of the lit lamp to one side surface. In addition, the light guide section makes the light from the condensing section travel while totally reflecting the light into the light guide plate to form a planar light source.Some of the light is scattered by the white dot pattern on the back surface of the light guide plate to form a flat light source. It is taken out to the surface as a light source.
[0004]
Between the backlight and the liquid crystal display, an optical sheet such as a prism sheet for improving the brightness of the backlight by aligning the light emitted from the backlight at a wide angle within a certain angle range, and the light guide described above. A diffusion sheet or the like for diffusing light from the light plate is provided.
[0005]
Since these sheets expand and bend due to the heat of the backlight, various methods have been proposed to prevent such bending.
[0006]
For example, Patent Literature 1 discloses a liquid crystal display device in which a side hole is formed in a side wall of a housing and a protrusion of an optical sheet is inserted into the side hole to prevent the optical sheet from bending when a backlight is used. It has been disclosed.
[0007]
Further, for example, in Patent Document 2, a long hole is formed in a longitudinal direction of each optical sheet, and the long hole is engaged with a positioning protrusion formed on a frame, thereby bending or displacing the optical sheet due to thermal stress. There is disclosed a liquid crystal display device for preventing such a problem.
[0008]
[Patent Document 1]
JP 2000-19512 [Patent Document 2]
JP 2001-91947 A
[Problems to be solved by the invention]
However, in Patent Document 1, the lateral hole is formed only on one side of the optical sheet, and in Patent Document 2, the long hole is formed only on one side of the optical sheet. At the time of inflation, there is a possibility that the seat portion located above the lateral hole or the elongated hole may lose its own weight and bend in the installed state.
[0010]
Further, in Patent Document 1 and Patent Document 2, it is assumed that the installation direction of the liquid crystal display device is only horizontal, so that the liquid crystal display device may be bent when used vertically.
[0011]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a liquid crystal display device in which sheets do not bend and display failures are reduced regardless of whether the device is placed vertically or horizontally.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a backlight unit accommodating a light source, a translucent reinforcing plate disposed on the front surface of the backlight unit, and a substantially rectangular transparent plate disposed on the front surface of the reinforcing plate. A light-emitting sheet and a liquid crystal panel disposed on a front surface of the sheet, wherein the sheet has a plurality of holes formed on two adjacent sides, and a projection formed on the backlight unit to be loosely fitted into the hole. It is characterized by the following.
[0013]
As described above, since the holes are provided on the two sides of the sheet, the sheet does not bend when the apparatus is placed vertically or horizontally, and display defects can be reduced.
[0014]
Further, in the above liquid crystal display device, it is desirable that any one of the pair of the hole and the projection is fitted. Further, the size of the hole into which the protrusion fits loosely can be increased as the distance from the hole into which the protrusion fits increases.
[0015]
Thus, when the backlight is turned off, the sheet can be positioned so that the periphery of the sheet is a space at equal intervals, and a space for expansion can be secured.
[0016]
Further, in the above liquid crystal display device, the hole may be an equilateral triangle having one side parallel to the side of the formed sheet.
[0017]
Thus, regardless of whether the liquid crystal display device is placed vertically or horizontally, the sheet can be stretched without stress in both the long side and the short side during thermal expansion.
[0018]
Further, in the liquid crystal display device described above, it is preferable that the liquid crystal display device is installed such that any side of the sheet where the hole is formed faces upward.
[0019]
As a result, the sheet is suspended and does not bend under its own weight when expanded.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention can be applied to a transmission type liquid crystal display device. In this embodiment, a liquid crystal display device having a direct type backlight will be described as an example.
[0021]
1 is a plan view of a liquid crystal display device, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, FIG. 4 is a plan view of sheets, and FIG. FIG. 6 is a diagram illustrating another shape of the hole.
[0022]
In FIG. 1, the housing is omitted. As shown in FIG. 1, a front frame 11 of the liquid crystal display device 10 has a substantially rectangular frame shape, and an opening 12 is formed in a size of a liquid crystal screen. The front frame 11 has a shape obtained by bending the outer end of the frame toward the back side, that is, an L-shaped cross section (see FIGS. 2 and 3). The front frame 11 can be integrally formed by metal molding or resin molding.
[0023]
The front frame 11 has a plurality of through holes. A through hole 11a (12 in FIG. 1) through which screws for fixing to a backlight unit to be described later are formed on the front surface, and a through hole (not shown) for passing screws to fix to a housing to be described later is formed on the side surface. ) Is formed. The shape of the through hole is not particularly limited, and may be, for example, a circle, a long axis circle, or the like.
[0024]
The front frame 11 is fixed to the backlight unit. At this time, a back plate 20 serving as the bottom of the backlight unit is provided so as to face the front frame 11. The back plate 20 has a side surface portion 20 a formed by bending an end portion so as to partially overlap the front frame 11 (see FIG. 2). Further, a through hole (not shown) is formed in the back plate 20 at a portion overlapping a screw hole of a side frame 22 described later. The back plate 20 can be integrally formed by metal molding or resin molding.
[0025]
FIG. 2 shows the configuration of the liquid crystal display device 10 along the line AA in FIG. The liquid crystal display device 10 includes a liquid crystal module 30 and a housing 40 that supports the liquid crystal module 30. The liquid crystal module 30 is disposed on the front surface of the backlight unit 21 in the order of the liquid crystal display 50 and the front frame 11, and the liquid crystal display 50 is sandwiched between the backlight unit 21 and the front frame 11.
[0026]
The backlight unit 21 includes a frame-shaped side frame 22 forming a side surface, a detachable back plate 20 that covers an opening of the side frame 22 opposite to the liquid crystal display 50, and a liquid crystal display 50 of the side frame 22. A light-transmitting reinforcing plate 23 covering the opening on the side of the liquid crystal display 50 provided on the side frame 22 on the side of the liquid crystal display 50, the reinforcing plate 23 is sandwiched between the side frame 22 and the liquid crystal between the front frame 11. An upper frame 24 for holding the display 50 and a lamp 25 attached to the side frame 22 are provided.
[0027]
It is desirable that a reflector (not shown) or the like be provided on the back plate 20 and the side frame 22 on the side of the lamp 25 to effectively use light.
[0028]
Cylindrical projections 22 a to 22 f are formed on the front side of the side frame 22, and the holes 50 c to 50 h of the sheets 50 b of the liquid crystal display 50 and the through hole 24 a of the upper frame 24 are fitted. A screw hole (not shown) is formed on the front side of the side frame 22 at a portion overlapping the through hole 11a of the front frame 11, and a through hole (not shown) of the back plate 20 is formed on the rear side of the side frame 22. A screw hole (not shown) is formed in a portion overlapping with. Then, the side frame 22 and the back plate 20 are screwed. The fixing means of the back plate 20 is not limited to a screw, and may be, for example, a fitting type.
[0029]
The upper frame 24 is a substantially L-shaped frame that covers a part of the front and side surfaces of the side frame 22. A through hole (not shown) is formed in the upper frame 24 at a portion overlapping the through hole (not shown) of the front frame 11 and the screw hole (not shown) of the side frame 22. Then, the front frame 11, the top frame 24, and the side frames 22 are screwed.
[0030]
The side frame 22 and the upper frame 24 can be integrally formed by metal molding or resin molding.
[0031]
The reinforcing plate 23 is a support for preventing the liquid crystal display 50 from bending, and has a plate thickness of about 2 to 3 mm and is made of a translucent resin such as acrylic or polycarbonate. The light-diffusing function can be added to the reinforcing plate 23 by surface processing.
[0032]
The lamp 25 is supported by a lamp support 27 (see FIG. 3) attached to the side frame 22 and an O-ring 26 fitted on the outer periphery of the lamp 25. As the lamp 25, for example, a cold cathode fluorescent lamp can be used. It is preferable that the lamp support 27 and the O-ring 26 be made of an elastic material such as rubber in order to prevent the lamp 25 from being damaged. The lead wire 25 a from the lamp 25 penetrates through the lamp support 27 and the side frame 22, and is guided to the back side of the back plate 20.
[0033]
A through hole (not shown) is formed on the side surface of the housing 40 at a portion overlapping the through hole on the side surface of the front frame 11. Then, the housing 40 and the front frame 11 are screwed. As described above, the front frame 11 is fixed to the backlight unit 21, that is, the liquid crystal display device 10 is integrated.
[0034]
The liquid crystal display 50 includes a liquid crystal panel 50a in which liquid crystal is sealed between two glass substrates with transparent electrodes and a polarizing plate is attached to the front and back surfaces of the glass substrate, and a light diffusion sheet disposed on the back surface of the liquid crystal panel 50a. And sheets 50b in which light-collecting sheets and the like are laminated. For the sheets 50b, a resin having good translucency can be used, and for example, PET can be used.
[0035]
As shown in FIG. 4, the sheets 50b have a substantially rectangular shape, and have holes 50c to 50h on two adjacent sides. Here, four holes 50e to 50h are formed on the long side of the sheet 50b, and two holes 50c and 50d are formed on the short side. When the liquid crystal display device 10 is placed horizontally, the holes 50e to 50h are arranged so as to face up, and when the liquid crystal display device 10 is vertically arranged, the holes 50c and 50d are arranged so as to face up. These holes 50c to 50h are formed in the projections 50i to 50n of the sheets 50b. As shown in the enlarged view of FIG. 5, the hole 50f is a circular hole, the holes 50c and 50d can be substantially rectangular holes, and the holes 50e, 50g, and 50h are long holes along the long side direction. be able to. The hole 50f fits with the protrusion 22d, and the holes 50c to 50e and 50g to 50h loosely fit with the protrusions 22a to 22c and 22e to 22f of the side frame 22 described above. This is because the holes 50f serve as a reference for positioning the seals 50b, and when the sheets 50b expand, the sheets 50b extend in each direction with the positional relationship between the holes 50f and the side frames 22 fixed. , 50d, 50e, 50g, and 50h are designed corresponding to the positions of the holes 50f so that the sheets 50b are not bent.
[0036]
In this way, by the holes 50f fitted into the projections 22d, when the backlight is turned off, the sheet can be positioned so that the periphery of the sheet becomes a space at equal intervals, and a space for expansion can be secured. The holes 50c to 50e and 50g to 50h loosely fitted to the projections 22a to 22c and 22e to 22f allow the sheets 50b to thermally expand due to the heat of the backlight regardless of whether the liquid crystal display device 10 is placed vertically or horizontally. It does not bend. Therefore, a favorable display state can be maintained.
[0037]
The size of these holes is designed in consideration of the thermal expansion of the material. That is, if the rate of expansion of the sheets 50b is large, it is necessary to increase the size of the holes and play. Hereinafter, calculation examples of the optimal sizes of the holes 50c to 50e and 50g to 50h will be described.
[0038]
For example, the linear expansion coefficient α (X direction: α _X , Y direction: α _Y ) of the sheets 50 b is α _X = 2.65 × 10 ⁻⁵ , α _Y = 1.95 × 10 ⁻⁵ , and the long side It is assumed that X is X = 870 (mm), short side Y is Y = 550 (mm), and the temperature increase ΔT of the sheet 50b when using the backlight is ΔT = 80 (K).
[0039]
Since the projection 22d and the hole 50f fit each other, it becomes a reference. The length X1 in the X direction from the projection 22d to the projections 22a and 22b is X1 = 382 (mm), and the length X2 from the projection 22d to the projection 22f is X2 = 385. (Mm), the length X3 from the protrusion 22d to the protrusion 22e is X3 = 135 (mm), the length X4 from the protrusion 22d to the protrusion 22c is X4 = 250 (mm), and the Y direction from the protrusion 22d to the protrusion 22b is The length Y1 is Y1 = 185 (mm), and the length Y2 in the Y direction from the protrusion 22d to the protrusion 22a is Y2 = 375 (mm).
[0040]
The minimum size required for play in each hole is proportional to the coefficient of linear expansion of the sheet, the distance from the projection 22d, and the temperature rise when the backlight is used. The play of the holes 50c and 50d in the X direction is f (X1), the play of the hole 50h in the X direction is f (X2), and the play of the hole 50c in the Y direction is f (Y2), and is calculated using the following formula. I do.
[0041]
f (X1) = n (αX ・ ΔT ・ X1) ≒ 4.9 (mm)
f (X2) = n (αX ・ T ・ X2) ≒ 4.9 (mm)
f (Y2) = n (αX ・ ΔT ・ Y2) ≒ 3.6 (mm)
Here, the coefficient n was set to n = 6. f (X1), f (X2) and f (Y2) are play required on the projection 22d side, respectively. Therefore, in the case of the hole 50h, for example, a play of about 4.9 (mm) is required on the protrusion 22d side of the protrusion 22f, and the size of the hole 50h is designed to be larger. The hole 50d requires a play of about 1.8 (mm) in the Y direction, 50e and 50g requires play of 3.2 (mm) and 1.8 (mm) in the X direction on the side of the protrusion 22d. Is set at least as large as each play. In addition, since the hole 50d is located closer to the protrusion 22d than the hole 50c, the hole 50d may have a size equivalent to that of the hole 50c. Similarly, the holes 50e and 50g may have the same size as the hole 50h.
[0042]
Further, the shapes of the holes 50c to 50e and 50g to 50h other than those for positioning may be regular triangles as shown in FIG. For example, a regular triangle having one side of 6 mm can be used, and the diameters of the protrusions 22a to 22f can be 3 mm. Here, the holes 50e, 50g, and 50f formed on the long sides of the sheets 50b are arranged such that one side is parallel to the long side. On the other hand, the holes 50c and 50d formed on the short side of the sheets 50b are arranged such that one side is parallel to the short side.
[0043]
As described above, by forming the holes 50c to 50e and 50g to 50h as equilateral triangles, the sheet 50b has a long side during thermal expansion regardless of whether the liquid crystal display device 10 is placed vertically or horizontally. It can be extended in both directions on the short side without stress. The hole is not particularly limited as long as it has a shape having sides parallel to the sides of the sheets 50b to be formed, and may be, for example, a triangle or another polygon.
[0044]
【The invention's effect】
According to the present invention, a plurality of holes are formed on two adjacent sides of the sheet, and a projection is formed on the backlight unit to loosely fit in the holes, so that the apparatus can be placed vertically or horizontally. The sheet does not bend, and display defects can be reduced. Also, when the liquid crystal display device is installed in either the vertical or horizontal direction, the sheet can be stretched without stress in both the long side and the short side during thermal expansion. The sheet can be positioned so as to have equal spaces, and a space for expansion can be secured. Furthermore, it does not bend under its own weight during expansion.
[Brief description of the drawings]
FIG. 1 is a plan view of a liquid crystal display device of the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 1;
FIG. 4 is a plan view of sheets of the present invention.
FIG. 5 is an enlarged view of a main part of FIG. 4;
FIG. 6 is a view for explaining another shape of the hole of the present invention.
[Explanation of symbols]
10 Liquid crystal display device 21 Backlight units 22a to 22f
50b Sheets 50c to 50h Hole

Claims (5)

A backlight unit that accommodates a light source, a translucent reinforcing plate disposed in front of the backlight unit, a substantially rectangular translucent sheet disposed in front of the reinforcing plate, and A liquid crystal panel disposed on the front side, wherein the sheet has a plurality of holes formed on two adjacent sides thereof, and the backlight unit has projections which are loosely fitted in the holes. Display device. The liquid crystal display device according to claim 1, wherein any one pair of the hole and the protrusion is fitted. 3. The liquid crystal display device according to claim 2, wherein the size of the hole in which the protrusion fits loosely increases as the distance from the hole in which the protrusion fits increases. 4. The liquid crystal display device according to claim 1, wherein the hole is an equilateral triangle having one side parallel to a side of the formed sheet. 5. The liquid crystal display device according to any one of claims 1 to 4, wherein the liquid crystal display device is installed so that any one of the sides of the sheet where the holes are formed faces upward.

Images