JP2011210410A - Backlight unit, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-quality backlight unit in which thermal deformation of a front frame hardly occurs, and to provide a liquid crystal display device.SOLUTION: The backlight unit 3 has a light guide plate 30 and linear light sources 70 arranged in opposition on the side face of the light guide plate 30 housed in a case 10 with one face open, and a front frame 100 is installed covering the periphery part of the light guide plate 30 on the opening part 12 of the case 10. The front frame 100 is constructed of a plurality of plates 102-105, and at least one of the plates 102-105 is arranged with clearances 106-109 between the other plates so that its expansion may not be suppressed by other plates when it expands by heat generated from the linear light sources 70.

Description

  The present invention relates to a backlight unit and a liquid crystal display device, and more particularly to a technique for preventing deformation of a front frame of an edge light type backlight unit.

  An edge light type backlight unit generally contains a rectangular light guide plate and a linear light source disposed opposite to a side surface of the light guide plate in a box-type housing having one open surface. It has a structure in which a substantially square annular front frame is attached so as to cover the outer peripheral edge of the light guide plate (Patent Document 1).

  In recent years, the backlight unit has also become larger with the increase in the screen size of the liquid crystal display device. As a result, the front frame has also become larger. However, when the substantially square annular front frame becomes larger, it becomes bulky and the backlight unit is assembled. However, there are concerns that it will be difficult to handle and high costs. Therefore, as a method for solving these problems, for example, as shown in FIG. 14, the front frame 900 is divided into four strip-shaped plates 902 to 905 corresponding to the respective sides of the light guide plate. Reducing the size has been done.

JP 2006-128036 A

  However, when the backlight unit having the front frame 900 as shown in FIG. 16 is turned on, the plates 902 to 905 are expanded by the heat generated from the linear light source and mainly in the longitudinal direction (the direction of the arrow in the figure). Stretch. In particular, in the case of an edge light type backlight unit, since the linear light source is located on the back side of the plate, the heat of the linear light source is easily transmitted to the plate, and the degree of expansion is large because the plate becomes hotter. Furthermore, if the backlight unit is increased in size, the longitudinal dimension of each plate 902 to 905 becomes longer, and the degree of expansion further increases.

  On the other hand, each plate 902 to 905 has screws 990a because both ends in the longitudinal direction are fixed by the ends of other plates arranged on both sides, or when each plate 902 to 905 is screwed. Since the screwing point is fixed by ˜990h, it is not possible to extend straight in the longitudinal direction within the fixed range, and the range is bent within the range. If such a bent state continues for a long time, the plate is deformed, and even if the backlight unit is turned off, it does not return to its original shape while being bent. If this is done, the appearance of the backlight unit will be reduced, which is undesirable in terms of quality, and if the front frame is thermally deformed, problems such as a gap will occur between the backlight unit and other members in the liquid crystal display device, resulting in liquid crystal display. It is not preferable in terms of the quality of the apparatus.

  In view of the above problems, it is a primary object of the present invention to provide a high-quality backlight unit and a liquid crystal display device in which thermal deformation of the front frame hardly occurs.

  In order to achieve the above object, according to one aspect of the backlight unit of the present invention, a light guide plate and a linear light source disposed opposite to the side surface of the light guide plate are accommodated in a housing having one open surface. A backlight unit in which a front frame is attached to an opening of a housing so as to cover a peripheral portion of the light guide plate, and the front frame includes a plurality of plates, and at least one of the plates. One is characterized in that a clearance is provided between the plate and the other plate so that the expansion is not suppressed by the other plate when the plate is expanded by the heat generated from the linear light source.

  One aspect of the liquid crystal display device according to the present invention includes the backlight unit and a liquid crystal panel.

  In the backlight unit and the liquid crystal display device according to the present invention, the front frame is composed of a plurality of plates, and at least one of the plates is another plate when expanded by the heat generated from the linear light source. In order to prevent the expansion of the plate, a clearance is provided between the plate and the other plate. Therefore, even if the plate arranged with the clearance is expanded and expanded, the expansion is caused by the other plate. It is difficult to suppress and the plate is unlikely to be bent. Therefore, even if the backlight unit is lit for a long time, the plate is hardly deformed by heat, and as a result, the front frame is hardly deformed.

The partially broken perspective view which shows schematic structure of the liquid crystal display device which concerns on this embodiment 1 is an exploded perspective view showing a schematic configuration of a backlight unit according to the present embodiment. The perspective view for demonstrating the attachment state of a front frame Top view showing the front frame The enlarged view which shows the part enclosed by the virtual line in FIG. The figure which shows the state of the plate before expansion The figure which shows the state of the plate after expansion The top view which shows the front frame which concerns on the modification 1. The top view which shows the front frame which concerns on the modification 2. The top view which shows the front frame which concerns on the modification 3. The top view which shows the front frame which concerns on the modification 4. The top view which shows the front frame which concerns on the modification 5. The top view which shows the principal part of the front frame which concerns on the modification 6. The top view which shows the principal part of the front frame which concerns on the modification 7. The perspective view which shows the principal part of the front frame which concerns on the modification 7. The top view which shows the front frame which concerns on a prior art example

Hereinafter, a liquid crystal display device and a backlight unit according to the present embodiment will be described with reference to the drawings.
[Liquid Crystal Display]
FIG. 1 is a partially broken perspective view showing a schematic configuration of the liquid crystal display device according to the present embodiment. As shown in FIG. 1, a liquid crystal display device 1 according to this embodiment includes a liquid crystal panel 2 that forms a color image based on an image signal from the outside, and a backlight unit 3 disposed on the back surface of the liquid crystal panel 2. With.

[Backlight unit]
2 is an exploded perspective view showing a schematic configuration of the backlight unit according to the present embodiment. In FIG. 2, the X-axis direction is the left-right direction (longitudinal direction) of the liquid crystal display device, and the Y-axis direction is the liquid crystal display device. The up-down direction (short direction) and the Z-axis direction are the front-rear direction of the liquid crystal display device (the upper side of the page indicated by the arrow is the front). Note that the drawings other than FIG. 2 also indicate the same direction when the directions are described in the X axis, the Y axis, and the Z axis.

  As shown in FIG. 2, the backlight unit 3 according to the present embodiment is, for example, a 32-inch edge light type (side light type) backlight unit, and includes a housing 10, a reflection sheet 20, a light guide. An optical plate 30, a diffusion sheet 40, a prism sheet 50, a polarizing sheet 60, a plurality of linear light sources 70, a plurality of heat sinks 80, a front frame 100, and the like are provided.

  The housing 10 is made of, for example, a metal made of a galvanized steel plate or the like, and has a box-shaped housing main body 11 with an open front surface, and a rectangular ring extending so as to project outward from the opening of the housing main body 11. The plate attachment portion (opening portion) 12 is provided with a plurality of screw holes 13a to 13h. In the housing 10, a reflection sheet 20, a light guide plate 30, a diffusion sheet 40, a prism sheet 50, and a polarizing sheet 60 are stacked in that order from the bottom surface side. The linear light sources 70 placed on the heat sink 80 are respectively arranged on the side surfaces.

  The reflection sheet 20 is a substantially square sheet made of, for example, PET (polyethylene terephthalate), and is disposed on the back side of the light guide plate 30, and reflects light reaching the back side of the light guide plate 30 to the front side. The reflection sheet 20 may be a metallic foil having metallic luster or an Ag sheet.

  The light guide plate 30 is a substantially square plate material made of, for example, PC (polycarbonate) or acrylic resin, and a dot pattern (not shown) is formed on the surface as a light lighting element for collecting light. The light emitted from the linear light source 70 is reflected or diffused by the light collecting element, and is transmitted through the light guide plate 30 to be mixed and averaged, and is emitted from the front surface spreading toward the liquid crystal panel 2 side. The daylighting element is not limited to a dot pattern, and includes an uneven prism.

The diffusion sheet 40 is a substantially square film made of, for example, PET or PC resin, and is laminated in a state of being in close contact with the front surface of the light guide plate 30.
The prism sheet 50 is a substantially rectangular optical sheet formed by forming a uniform prism pattern with an acrylic resin on one surface of a face material made of polyester resin, for example, and is laminated in close contact with the diffusion sheet 40. Yes.

  The polarizing sheet 60 is, for example, a substantially square film made by bonding a PC film, a polyester film, and an acrylic resin, or made of PEN (polyethylene naphthalate), and is laminated in close contact with the prism sheet 50. Yes.

  Each linear light source 70 is made of, for example, a ceramic-made long substrate 71 facing the upper side surface and the lower side surface of the light guide plate 30, and the substrate 71 along the longitudinal direction of the substrate 71. It is an LED module comprising a plurality of LED elements 72 mounted at regular intervals in a row.

  The linear light source 70 is not limited to the LED module. For example, a light emitting module using a semiconductor light emitting element such as LD (laser diode) or OEL (organic electroluminescence), or a lamp such as a cold cathode discharge lamp or a hot cathode discharge lamp may be used.

  Each linear light source 70 emits light toward the light guide plate 30 when power is supplied from a lighting circuit (not shown) attached to the back surface of the housing 10. The emitted light enters the light guide plate 30 from the side surface of the light guide plate 30, exits from the front surface of the light guide plate 30, and then passes through the diffusion sheet 40, the prism sheet 50, and the polarizing sheet 60, The light is emitted from the opening 101 of the frame 100 to the outside of the backlight unit 3, further passes through the liquid crystal panel 2, and is emitted to the outside of the liquid crystal display device 1.

  The heat sink 80 is made of, for example, aluminum, and has a mounting surface for mounting the linear light source 70, and the mounting surface and the length of the side surface so that the mounting surface faces the side surface of the light guide plate 30. They are arranged with their directions matched.

[Front frame]
FIG. 3 is a perspective view for explaining an attached state of the front frame. FIG. 4 is a plan view showing the front frame. FIG. 5 is an enlarged view showing a portion surrounded by an imaginary line in FIG. 4, wherein (a) shows a state before expansion, and (b) shows a state after expansion.

  As shown in FIG. 3, the front frame 100 has a substantially rectangular ring shape, and is composed of four strip-like plates 102 to 105 corresponding to each side of the light guide plate 30. In a state where the upper, lower, left, and right plates 102 to 105 are attached to the respective sides of the plate attachment portion 12 of the housing 10, the region surrounded by the plates 102 to 105 is the opening 101 of the front frame 100. By dividing the front frame 100 into the four plates 102 to 105 in this way, the size of each member is reduced, making it easy to handle when assembling the backlight unit.

  As shown in FIG. 4, the upper plate 102 is a long plate shape having a substantially isosceles trapezoidal shape in plan view arranged along the longitudinal direction of the front frame 100, for example, among two parallel sides in plan view. The length L1 of the short side (the upper base of the trapezoid) is 637 [mm], the length L2 of the long side (the lower base of the trapezoid) is 720 [mm], and the width (the height of the trapezoid) W1 is 19 [mm]. The thickness is 3.5 [mm]. The lower plate 103 has the same shape as the upper plate 102 and is arranged along the longitudinal direction of the front frame 100.

  The left plate 104 is a long plate having a substantially isosceles trapezoidal shape in plan view, which is disposed along the short direction of the front frame 100 and has a shorter length in the longitudinal direction than the upper plate 102 and a wider width. Of the two parallel sides in plan view, the length L3 of the short side (the upper base of the trapezoid) is 392 [mm], the length L4 of the long side (the lower base of the trapezoid) is 434 [mm], and the width (the trapezoidal shape) Height) W2 is 21 [mm], and the thickness is 3.6 [mm]. The right plate 105 has the same shape as the left plate 104 and is arranged along the short side direction of the front frame 100.

  The reason why the width W2 of the left and right plates 104, 105 is wider than the width W1 of the upper and lower plates 102, 103 is that the upper and lower plates 102, 103 are expanded more than the left and right plates 104, 105. For example, the amount is large and the strength of the front frame 100 needs to be secured.

  Each of the plates 102 to 105 is arranged with a clearance from the other plate so that the expansion is not suppressed by the other plate when it is expanded by the heat generated from the linear light source 70. Specifically, each of the plates 102 to 105 is arranged so that the short side is on the inside in a plan view, and gaps 106 to 109 are provided between adjacent plates, and the gaps 106 to 109 are It is located at four corner portions of the plate mounting portion 12.

  The mode of each of the gaps 106 to 109 will be described by taking the gap 108 as an example. As shown in FIG. 5A, for example, the hypotenuse 103a of the lower plate 103 and the hypotenuse 104a of the left plate 104 are substantially parallel. The sum of the angle θ1 of the long side corner of the lower plate 103 and the angle θ2 of the short side corner of the left plate 104 is about 90 °. The width W3 of the gap 108, that is, the distance between the hypotenuses 103a and 104a in the direction orthogonal to the hypotenuses 103a and 104a is, for example, 0.5 [mm].

  The width W3 of the gap 108 can be determined based on, for example, the elongation rates of the lower plate 103 and the left plate 104. The elongation rates of the plates 103 and 104 are, for example, from the gap 108, as shown in FIG. It can be calculated by integrating the linear expansion coefficients of the materials of the plates 103 and 104 to the maximum distance L5 from the nearest through hole 110c and the maximum width L6 from the gap 108 to the nearest through hole 110f. . The width W3 of the gap 108 is preferably designed to be larger than the design tolerance of the plates 103 and 104.

  Since the gap 108 is thus provided between the lower plate 103 and the left plate 104, the lower plate 103 and the left plate 104 expand due to the heat of the linear light source 70 as shown in FIG. 5B. Thus, even if the end portions 103b and 104b move in the plate longitudinal direction (in the direction of the arrow in the figure), which is the main extension direction, they do not interfere with each other. That is, even if the lower plate 103 expands to the maximum extent, the hypotenuse 103a moves only to the virtual line V shown in FIG. 5A, and even if the left plate 104 expands to the maximum extent, the hypotenuse 104a does not move to the virtual line V. Therefore, the lower plate 103 and the left plate 104 are not restrained from expansion due to expansion of each other, and are not bent due to the suppression of expansion, so that thermal deformation due to the bending does not occur.

Although the gap 108 has been described above as an example, the same applies to the other gaps 106, 107, and 109.
Each of the plates 102 to 105 may be formed of a resin material such as polycarbonate. The linear expansion coefficient of the resin material is preferably 12 × 10 ⁻⁷ [1 / K] or less, more preferably 2 × 10 ⁻⁷ [1 / K] or more and 7 × 10 ⁻⁷ [1 / from the viewpoint of preventing thermal deformation. K] or less is preferable. In the present embodiment, from the viewpoint of using a resin plate that has high strength and is not easily deformed by reducing the inherent thermal expansion coefficient of the resin, for example, 20-40 [%] for polycarbonate resin PP resin or the like. You may use the resin plate which mixed the glass fiber of the grade.

  Each of the plates 102 to 105 has a pair of through holes 110a to 110h, and screws 90a to 90h inserted into the through holes 110a to 110h are screwed into the screw holes 13a to 13h of the housing 10 as shown in FIG. By this, it is being fixed to the plate attaching part 12 of the said housing | casing 10. FIG.

  As shown in FIG. 4, the distance L7 between the through holes 110a and 110b of the upper plate 102 and the through holes 110c and 110d of the lower plate 103 is 420 [mm], and the through holes 110e and 110f of the left plate 104 are And a distance L8 between the through holes 110g and 110h of the right plate 105 is 347 [mm].

  Further, the through holes 110a to 110d of the upper and lower plates 102 and 103 are long holes, while the through holes 110e to 110h of the left and right plates 104 and 105 are simply circular holes (round holes). The width W4 in the plate longitudinal direction of the through holes 110a and 110b of the upper plate 102 and the through holes 110c and 110d of the lower plate 103 is 10 [mm], the through holes 110e and 110f of the left plate 104, and the right plate 105 The width W5 in the plate longitudinal direction of the through holes 110g and 110h is 4 [mm].

  Since the distance between the through holes of the plates 102 to 105 is substantially equal to the distance between the screw holes corresponding to the through holes, the plates 102 to 105 are not easily displaced in the plate longitudinal direction when attached to the housing 10. For example, in the case of the upper plate 102, the distance L7 between the through holes 110a and 110b is substantially equal to the distance between the screw holes 13a and 13b. The plate 102 is not displaced in the longitudinal direction of the plate when attached to the housing 10. Therefore, it is difficult to cause a problem that one of the gaps 106 and 107 is widened and the other is narrowed due to the displacement of the upper plate 102. The upper plate 102 has been described above, but the same applies to the other plates 103 to 105.

  Since the upper and lower plates 102 and 103 have long holes in the through-holes 110a to 110d, the upper and lower plates 102 and 103 have a configuration in which expansion is hardly further suppressed when they are fixed by screwing. 6A and 6B are diagrams showing a state of the plate before expansion, in which FIG. 6A is a plan view, and FIG. 6B is a cross-sectional view taken along line AA in FIG. FIG. 7 is a cross-sectional view showing the state of the plate after expansion.

  For example, in the case of the upper plate 102, as shown in FIG. 6A, when the backlight unit 3 is not lit and is not expanded, both longitudinal ends of the upper plate 102 in the through holes 110a and 110b are provided. Screws 90a and 90b are located on the side (outside). As shown in FIG. 7, when the backlight unit 3 is turned on and the upper plate 102 is expanded in the direction of the arrow, the positions of the through holes 110a and 110b are moved to both ends in the longitudinal direction of the upper plate 102 due to the expansion. To do. Since the through holes 110a and 110b are elongated holes, the movement of the through holes 110a and 110b is not suppressed by the screws 90a and 90b, and the extension of the upper plate 102 is not suppressed by the screws 90a and 90b.

The upper plate 102 has been described above, but the same applies to the lower plate 104.
On the other hand, the left and right plates 104 and 105 that are less expanded by heat than the upper and lower plates 102 and 103 are more fixed than the upper and lower plates 102 and 103 because the through holes 110e to 110h are round holes. It has become. As described above, if the left and right plates 104 and 105 are fixed, and the upper and lower plates 102 and 103 are easily expanded, it is possible to suppress bending and undulation of the optical sheets 40, 50, and 60. .

  Note that the left and right plates 104 and 105 do not necessarily have round holes, and may be elongated holes like the upper and lower plates 102 and 103. In this case, the left and right plates 104 and 105 are configured such that the expansion is more difficult to be suppressed when they are fixed by screwing.

  The tightening of the screws 90a to 90h is preferably adjusted to a torque that fixes the plates 102 to 105 and allows thermal expansion of the plates 102 to 105.

[Modification 1]
The front frame according to the first modification is basically the same as the front frame 100 according to the above-described embodiment, but the aspect of division into plates is different. In the following, description of common configurations will be omitted or simplified, and differences will be mainly described.

  FIG. 8 is a plan view showing a front frame according to the first modification. As shown in FIG. 8, the front frame 200 according to the first modification includes four strip-like plates 202 to 205 on the top, bottom, left, and right. Each of the plates 202 to 205 includes a pair of through holes 210a to 210d (the through holes of the left and right plates 204 and 205 are not shown), and screws 90a to 90h inserted into the through holes 210a to 210h are provided on the housing 10. The plate 10 is fixed to the housing 10 by being screwed into the screw holes 13 a to 13 h of the plate attachment portion 12.

  Each of the plates 202 to 205 is not a substantially isosceles trapezoid in a plan view but a substantially square shape. The ends of the upper and lower plates 202 and 203 exist on both sides in the longitudinal direction of the left and right plates 204 and 205 with gaps 206 to 209 provided, but are longer than the left and right plates 204 and 205. The left and right plates 204 and 205 do not exist on both longitudinal sides of the upper and lower plates 202 and 203.

  With such a configuration, no matter how much the upper and lower plates 202 and 203 expand in the direction of the arrow due to expansion, the left and right plates 204 and 205 do not suppress the expansion, so that the upper and lower plates 202 and 203 are bent. Will not be deformed. Since the upper and lower plates 202 and 203 are longer than the left and right plates 204 and 205, and the amount of expansion is large, such a configuration is effective. In addition, the upper and lower plates 202 and 203 are likely to become high temperature because the linear light source 70 as a heat source is disposed on the back side, and the amount of expansion thereof is large. Therefore, such a configuration is effective.

  The width W6 of the gaps 206 to 209 along the longitudinal direction of the left and right plates 204, 205 can be determined based on the elongation rate of the left and right plates 204, 205, for example. The rate can be calculated by, for example, integrating the linear expansion coefficients of the materials of the plates 204 and 205 with the distance L9 from the gaps 206 to 209 to the nearest through hole. The width W6 is preferably designed to be larger than the design tolerance of the plates 204 and 205.

[Modification 2]
The front frame according to Modification 2 is basically the same as the front frame 100 according to the above-described embodiment, but the aspect of screwing is different. In the following, description of common configurations will be omitted or simplified, and differences will be mainly described.

  FIG. 9 is a plan view showing a front frame according to the second modification. As shown in FIG. 9, the front frame 300 according to the modified example 2 includes four strip-shaped plates 302 to 305 on the top, bottom, left, and right. Each of the plates 302 to 305 has a through hole (not shown) at the center in the longitudinal direction, and screws 390a to 390d inserted into the through holes are screw holes (not shown) provided at corresponding positions of the plate mounting portion 12 of the housing 10. It is fixed to the housing 10 by being screwed into a not-shown.

  Each of the plates 302 to 305 is screwed at one point in the longitudinal center, and the through hole is not a long hole but a round hole. If the plates 302 to 305 are screwed at one point in this way, the extension of the plates 302 to 305 is not suppressed by the screws 390a to 390d even if the through holes are not long holes.

With such a configuration, the number of screwing points can be reduced, and the assembly of the backlight unit becomes easier.
[Modification 3]
The front frame according to the modified example 3 is basically the same as the front frame 100 according to the above embodiment, but the manner of dividing into plates and the manner of screwing are different. In the following, description of common configurations will be omitted or simplified, and differences will be mainly described.

  FIG. 10 is a plan view showing a front frame according to the third modification. As shown in FIG. 10, the front frame 400 according to the third modification includes four plates 402 to 405 having the same shape. Each of the plates 402 to 405 has a substantially L shape including long pieces 402 a to 405 a and short pieces 402 b to 405 b, and the long pieces 402 a to 405 a constitute about half of the long side of the front frame 400. The short piece portions 402b to 405b constitute about half of the short side of the front frame 400.

Gaps 406 to 409 are provided between the ends of the adjacent plates, and these gaps 406 to 409 are located at the approximate center of each side of the front frame 400.
The width W7 of the gaps 406 and 407 can be determined based on, for example, the elongation rate of the long piece portions 402a to 405a, and the elongation rate of each of the long piece portions 402a to 405a can be determined from the gaps 406 and 407, for example. It can be calculated by integrating the linear expansion coefficient of the material of each of the long piece portions 402a to 405a to the distance L10 to the nearest through hole.

  The width W8 of the gaps 408 and 409 can be determined based on, for example, the elongation rate of the short piece portions 402b to 405b. The elongation rate of each short piece portion 402b to 405b is, for example, the closest from the gaps 408 and 409. It can be calculated by integrating the linear expansion coefficient of the material of each of the short piece portions 402b to 405b to the distance L11 to the through hole.

  The width W7 of the gaps 406 and 407 and the width W8 of the gaps 408 and 409 are preferably designed to be larger than the design tolerances of the long pieces 402a to 405a and the short pieces 402b to 405b.

  Each of the plates 402 to 405 is provided with through holes (not shown) at the corners, and screws 490 a to 490 d inserted into the through holes are screws provided at corresponding positions of the plate mounting portion 12 of the housing 10. The housing 10 is fixed by screwing into a hole (not shown).

  With such a configuration, the number of screwing points can be reduced, the assembly of the backlight unit can be facilitated, and the occurrence of a gap in the corner portion of the front frame 400 can be prevented.

[Modification 4]
The front frame according to the modification 4 is basically the same as the front frame 100 according to the above-described embodiment, but the manner of dividing into plates and the manner of screwing are different. In the following, description of common configurations will be omitted or simplified, and differences will be mainly described.

  FIG. 11 is a plan view showing a front frame according to the fourth modification. As shown in FIG. 11, the front frame 500 according to Modification 4 includes two plates 502 and 503 having the same shape. Each of the plates 502 and 503 has a substantially L shape composed of long pieces 502a and 503a and short pieces 502b and 503b. The long pieces 502a and 503a constitute the long side of the front frame 500, and the short pieces The parts 502b and 503b constitute the short side of the front frame 500.

  Gaps 506 and 507 are provided between the end portions of both plates 502 and 503, and these gaps 506 and 507 are located at two of the four corner portions of the front frame 500.

  The width of the gap 506 (corresponding to the width W3 in FIG. 5A) can be determined based on the elongation rate of the long piece portion 502a of the plate 502 and the short piece portion 503b of the plate 503. For example, the linear expansion coefficient of the material of the plate 502 is integrated to the distance L12 from the gap 506 to the through hole 510a, and the linear expansion coefficient of the material of the plate 503 is integrated to the distance L13 from the gap 506 to the through hole 510c. This can be calculated. The same applies to the width of the gap 507. The widths of the gaps 506 and 507 are preferably designed to be larger than the design tolerances of the long pieces 502a and 503a and the short pieces 502b and 503b.

  Each of the plates 502 and 503 is provided with through holes (not shown) at the corner portions, and long hole through portions 510a to 510d are also provided at both ends. The through portion 510 a is a long hole having a wide width along the longitudinal direction (X-axis direction) of the long piece portion 502 a which is one main extension direction of the plate 502, and the through portion 510 b is the other main portion of the plate 502. It is a long hole having a wide width along the longitudinal direction (Y-axis direction) of the short piece portion 502b which is the extending direction. The through portion 510c is a long hole having a wide width along the longitudinal direction (Y-axis direction) of the short piece portion 503b, which is one main extension direction of the plate 503, and the through portion 510d is the other main extension of the plate 503. This is a long hole having a wide width along the longitudinal direction (X-axis direction) of the long piece portion 503a. The screws 590a to 590f inserted into these through holes are fixed to the housing 10 by screwing them into screw holes (not shown) provided at corresponding positions of the plate mounting portion 12 of the housing 10.

With such a configuration, the number of plates can be reduced, and the assembly of the backlight unit becomes easier.
[Modification 5]
The front frame according to Modification 5 is basically the same as the front frame 100 according to the above embodiment, but the aspect of the clearance is different. In the following, description of common configurations will be omitted or simplified, and differences will be mainly described.

  FIG. 12 is a plan view showing a front frame according to the fifth modification. As shown in FIG. 12, the front frame 600 according to the modified example 5 includes four strip-shaped plates 602 to 605, up, down, left, and right. Each of the plates 602 to 605 includes a pair of through holes 610a and 610b (through holes of plates other than the upper plate 602 are not shown), and screws 90a to 90h inserted into the through holes 610a and 610b are provided on the housing 10. The plate 10 is fixed to the housing 10 by being screwed into the screw holes 13 a to 13 h of the plate attachment portion 12.

  When the front frame 600 is expanded only by the plate (upper plate 602) that covers the portion having the side surface facing the linear light source at the peripheral edge of the light guide plate, the front frame 600 is expanded by the other plate. In order not to suppress the expansion, a clearance is provided between the other plates (left and right plates 604, 605). That is, the front frame 600 is provided with the gaps 606 and 607 only at both ends in the longitudinal direction of the upper plate 602, and no gap is provided at both ends in the longitudinal direction of the lower plate 603. Furthermore, only the through holes 610a and 610b of the upper plate 602 are long holes, and the other through holes are round holes.

  In such a configuration, when the linear light source 70 is disposed only on the back side of the upper plate 602 and the linear light source 70 is not disposed on the back side of the lower plate 603, only the extension of the upper plate 602 is particularly problematic. It is effective when

[Modification 6]
The end surfaces of the plates forming the gaps between the plates do not necessarily have to be linear in plan view. That is, the end surface of the plate does not necessarily have to be flat.

  FIGS. 13A and 13B are plan views showing the main part of the front frame according to the modified example 6. FIG. 13A shows a state before expansion, and FIG. 13B shows a state after expansion. For example, as shown in FIG. 13A, the end surfaces 702a and 703a of the plates 702 and 703 forming the gap 708 between the plates 702 and 703 may be formed in a crank shape in plan view. That is, the end surfaces 702a and 703a of the plates 702 and 703 may be stepped. Moreover, as shown in FIG.13 (b), when the plates 702 and 703 expand | swell, you may become a structure which a mutual edge part meshes | engages.

[Modification 7]
The clearance between the plates is not necessarily configured to be recognized as a gap in plan view. FIG. 14 is a plan view showing the main part of the front frame according to Modification 7.

  FIG. 15 is a perspective view illustrating a main part of a front frame according to Modification 7. For example, as shown in FIGS. 14 and 15, an end surface 803 a of one plate 803 is provided with a protruding portion 803 b, and an end surface 804 a of the other plate 804 has a recessed portion 804 b into which the protruding portion 803 b is fitted. The structure which is provided and cannot be recognized as a clearance gap in planar view may be sufficient. With such a configuration, the bonding strength between the plates increases, and as a result, the strength that can cope with the deformation of the entire front frame can be improved.

[Other variations]
As described above, the liquid crystal display device and the backlight unit according to one embodiment of the present invention have been specifically described based on the embodiment, but the content of the present invention is not limited to the above embodiment. For example, the structure which combined suitably the partial structure of the said embodiment and its modification may be sufficient.

  The backlight unit according to the present invention can be used as, for example, a liquid crystal television, a liquid crystal display, a planar light source for general illumination, and the like.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal panel 3 Backlight unit 10 Housing | casing 12 Opening part 13a-13h Screw hole 30 Light guide plate 70 Linear light source 90a-90h Screw 100 Front frame 102-105 Plate 110a-110h Long hole

Claims (6)

A light guide plate and a linear light source disposed opposite to the side surface of the light guide plate are accommodated in a housing that is open on one side, and the front frame is in a state of covering the peripheral portion of the light guide plate in the opening of the housing. An attached backlight unit,
The front frame is composed of a plurality of plates, and at least one of the plates has another plate so that the expansion is not suppressed by another plate when the plate is expanded by heat generated from the linear light source. A backlight unit characterized in that a clearance is provided between the plate and the plate.   2. The backlight unit according to claim 1, wherein the light guide plate is substantially square, and the front frame is formed of four strip-shaped plates corresponding to the sides of the light guide plate.   The opening of the housing is provided with a plurality of screw holes for screwing the plates, and the plates are provided with through holes at positions corresponding to the screw holes. The through-hole of a plate arranged with a clearance between other plates is a long hole having a wide width along the main extension direction of the plate. Backlight unit.   The plate arranged with a clearance between the other plate is a plate arranged along the longitudinal direction of the housing, and the through hole of the plate is a long hole. The backlight unit according to claim 3.   The plate which covers the part which has the side surface which opposes the said linear light source in the peripheral part of the said light-guide plate is provided with a clearance between other plates, The any one of Claim 1 to 4 characterized by the above-mentioned. The backlight unit described in the crab.   A liquid crystal display device comprising the backlight unit according to claim 1 and a liquid crystal panel.

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