JP2004185868A - Backlight device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device and a liquid crystal display device having a light guide plate without generating variations in illuminance. <P>SOLUTION: A roughly quadrilateral light guide plate 15 is disposed in a manner that one side thereof is opposite to a line shape light source 16. The light source 16 and the light guide plate 15 are stored in a backlight housing 14. The length of a 1st side wall 15a including the side opposite to the light source 16 of the light guide plate 15 is shorter than that of a 2nd side wall 15b on an opposite side of the 1st side wall 15a, and an inner wall of the backlight housing 14 is shaped in almost a quadrilateral shape corresponding to the shape of the light guide plate 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device incorporating a backlight device for providing a backlight to a liquid crystal panel.
[0002]
[Prior art]
In a liquid crystal display device, a liquid crystal panel for displaying information is held in a backlight housing that also functions as a decorative plate. A backlight device is provided below the liquid crystal panel to make the liquid crystal display easier to see. The backlight device generally has a light source, a light guide plate for guiding light from the light source to the entire lower side of the liquid crystal panel, and an optical sheet for performing optical processing on the light from the light guide plate. These members are housed in a backlight housing.
[0003]
The light source is formed of, for example, an elongated fluorescent tube, and is provided on a side surface of a flat light guide plate. The light projected from the light source to the side surface of the light guide plate propagates through the light guide plate and exits from the surface of the light guide plate toward the liquid crystal panel. A reflection panel is provided on the opposite side of the liquid crystal panel with respect to the light guide plate, so that light incident on the light guide plate from the light source is emitted only in the direction of the liquid crystal panel.
[0004]
The light emitted from the light guide plate is irradiated on the liquid crystal panel after being subjected to predetermined optical processing such as diffusion or focusing by an optical sheet. As a result, the background of the liquid crystal panel becomes moderately bright, and the display on the liquid crystal panel is made easy to see.
[0005]
[Patent Document 1]
JP-A-11-162223
[Problems to be solved by the invention]
FIG. 1 is a plan view of an example of a conventional backlight device. The light source 1 and the light guide plate 2 are housed in a backlight housing 3. The light guide plate 2 has ears 2 a protruding from the left and right sides, and the movement of the light guide plate 2 in the Y direction is restricted by fitting the ears 2 a into the recesses of the backlight housing 3. You. The movement of the light guide plate 2 in the X direction is restricted by the side wall of the backlight housing 3. In addition, movement of the light guide plate 2 in a direction perpendicular to the XY directions (that is, a direction perpendicular to the paper surface) is regulated by a decorative plate (not shown) attached to the backlight housing 3.
[0007]
As described above, when the light guide plate 2 has the ears 2a, the intensity of the backlight light emitted from the light guide plate 2 to the liquid crystal panel (disposed over the light guide plate 2) is reduced. Unevenness occurs. That is, when the light projected from the linear light source 1 propagates through the light guide plate 2, a part of the light enters the ear 2a and is irregularly reflected. As a result, there is a problem that light becomes locally strong near the base of the ear portion 2a and illuminance unevenness occurs in a corresponding portion of the liquid crystal panel.
[0008]
FIG. 2 is a plan view of another example of the conventional backlight device. In the backlight device shown in FIG. 2, the light guide plate 2 is fixed to the bottom surface of the backlight housing 3 using an adhesive. The adhesive is provided in an area 2b (a shaded area) having a certain width along the left and right sides of the light guide plate 2. When the light guide plate 2 is fixed using an adhesive, the illuminance unevenness caused by the ears 2a does not occur as in the example shown in FIG. 1 described above, but along the left and right edges due to the reflection of the adhesive. There is a problem that illuminance unevenness occurs near the region 2b.
[0009]
The present invention has been made in view of the above points, and has as its object to provide a backlight device and a liquid crystal display device having a structure for fixing a light guide plate without generating uneven illuminance.
[0010]
[Means for Solving the Problems]
According to the present invention, in order to solve the above problems, a linear light source, a substantially quadrangular light guide plate arranged with one side thereof facing the light source, and the light source and the light guide plate are surrounded. And a backlight housing that is housed and held inside the backlight device, wherein a length of a first side wall including a side of the light guide plate facing the light source is opposite to the first side wall. The backlight device is provided, wherein the length is smaller than the length of the second side wall on the side, and the inner wall of the backlight housing forms a substantially quadrilateral corresponding to the shape of the light guide plate.
[0011]
According to the backlight device of the present invention, when the light guide plate attempts to move to the light source side, both side walls of the backlight housing first come into contact with the light guide plate and do not move any further. Thereby, destruction of the light source due to collision of the light guide plate can be avoided. Since there is no need to provide fixing projections on the light guide plate or fix with an adhesive, local light emission unevenness of the light guide plate does not occur, and good illumination can be secured as a backlight device. it can.
[0012]
In the backlight device described above, at least one of the third and fourth side walls extending between the first side wall and the second side wall of the light guide plate has a saw-toothed unevenness, and the backlight housing has The serrations may be formed on the inner wall to engage with the serrations. Further, the backlight housing may be formed of a transparent member. Further, each of the third and fourth side walls extending between the first side wall and the second side wall of the light guide plate may form an equal obtuse angle with the first side wall.
[0013]
Further, according to the present invention, there is provided a liquid crystal display device including a liquid crystal panel and a backlight device provided below the liquid crystal panel, wherein the backlight device includes a linear light source, and one side of the light source. A light guide plate having a substantially quadrangular shape arranged in a state where the light guide plate faces each other, and a backlight housing which holds and holds the light source and the light guide plate therein so as to surround the light source and the light guide plate. The length of the opposing light incident side wall is smaller than the length of the side wall opposite to the light incident side wall, and the side wall of the backlight housing forms a substantially quadrilateral corresponding to the shape of the light guide plate. Is provided.
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 3 is an exploded perspective view of a liquid crystal display device incorporating the backlight device according to the first embodiment of the present invention. FIG. 4 is a plan view of the backlight device shown in FIG.
[0015]
The liquid crystal display device 10 shown in FIG. 3 includes a liquid crystal panel 11, a backlight device 12, and a decorative plate 13. A backlight device 12 is provided below the liquid crystal panel 11, and a decorative plate 13 is provided above the liquid crystal panel 11. The liquid crystal panel 11 is a display panel that displays an image based on an input electric signal. The decorative plate 13 is a frame-shaped housing formed by processing a metal plate such as stainless steel (SUS), iron, or aluminum, and functions as an outer frame of the liquid crystal display device 10. The decorative plate 13 also has a function of reinforcing the liquid crystal panel 11.
[0016]
The backlight device 12 is an illumination device for irradiating light from the back side of the liquid crystal panel 11 so that the display on the liquid crystal panel 11 can be clearly seen. The backlight device according to the present embodiment is configured as a so-called edge light type in which light is introduced from the side wall (edge) of the light guide plate.
[0017]
The backlight device 12 is configured by arranging a light guide plate 15 and a light source 16 in a backlight housing 14. A reflection sheet 17 is disposed below the light guide plate 14. Further, an optical sheet 18 is disposed above the light guide plate 14.
[0018]
The light guide plate 15 is made of a substantially quadrangular transparent plate. The light guide plate 15 is a member for propagating light introduced from one of the side walls 15a (first side wall) and emitting the light from the surface, and is formed of transparent acrylic (PMMA) or the like. The thickness of the light guide plate 15 is large at the first side wall 15a and gradually decreases toward the opposite side wall 15b (second side wall). Thereby, the light incident from the first side wall 15a is efficiently emitted from the surface while propagating toward the second side wall.
[0019]
The light source 16 has a linear light source made of a cold cathode tube or the like, and is arranged along the first side wall 15 a of the light guide plate 15. The light source 16 includes a reflector 16a that surrounds the cold cathode tube and efficiently reflects light from the cold cathode tube. The light projected from the linear light source is efficiently reflected by the reflector 16a and travels toward the first side wall 15a of the light guide plate 15.
[0020]
The reflection sheet 17 is disposed on the back surface of the light guide plate 15 and is provided for reflecting light leaked from the light guide plate 4 and returning light to the inside of the light guide plate 4 again. The optical sheet 18 is disposed between the light guide plate 15 and the liquid crystal panel 11, and is provided to collect and diffuse light emitted from the light guide plate 15 and to efficiently emit light to the back side of the liquid crystal panel 11. .
[0021]
The backlight housing 14 is a box-shaped housing formed of a resin molded product such as polycarbonate. The backlight housing 14 accommodates the reflection sheet 17, the light guide plate 15, and the optical sheet 18 in a stacked state, and accommodates and holds the light source 16 along the first side wall 15a of the light guide plate 15. I do.
[0022]
In the liquid crystal display device 10 having the above configuration, as shown in FIG. 4, the light guide plate 15 of the backlight device 12 has a dimension A on the first side wall 15a side of the second side when viewed from the liquid crystal panel side. It is formed as a substantially quadrilateral (trapezoid in FIG. 4) smaller than the dimension B on the side wall 15b side. Therefore, the housing portion of the backlight housing 14 is also formed in a substantially quadrilateral shape corresponding to the shape of the light guide plate 15.
[0023]
Here, unlike the conventional light guide plate, the light guide plate 15 does not have an ear portion, and is not configured to be fixed with an adhesive or the like. That is, the shape of the light guide plate 15 is set to be a substantially quadrilateral shape such that the dimension A on the first side wall 15a side is smaller than the dimension B on the second side wall 15b side, so that the movement of the light guide plate in the X direction. Can also be regulated in the Y direction. That is, the movement of the light guide plate can be restricted in both the X and Y directions by the inner wall of the backlight housing.
[0024]
In particular, when the light guide plate 15 moves to the light source 16 side, both side walls of the backlight housing 14 first contact the light guide plate 15 and do not move any further. Thereby, the destruction of the light source 16 due to the collision of the light guide plate 15 can be avoided. Since there is no need to provide a fixing projection on the light guide plate 15, local unevenness in light emission of the light guide plate due to the projection does not occur, and good illumination as a backlight device can be secured.
[0025]
In this embodiment, since the shape of the light guide plate 15 is trapezoidal, the third side wall 15c and the fourth side wall 15d extending between the first side wall 15a and the second side wall 15b are each formed of the first side wall 15a. An equal obtuse angle is formed with respect to the side wall 15a. However, the angles of the third side wall 15c and the fourth side wall 15d with respect to the first side wall 15a do not necessarily have to be equal, and for example, one of the angles may be 90 degrees. However, if this angle (obtuse angle) is too large, the intensity of light emitted from the light guide plate 15 will not be uniform on the left and right, so it is preferable that both angles are equal obtuse angles as in this embodiment.
[0026]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an exploded perspective view of a liquid crystal display device incorporating a backlight device according to a second embodiment of the present invention, and FIG. 6 is a plan view of the backlight device shown in FIG. 3 and FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted.
[0027]
The liquid crystal display device 20 shown in FIG. 5 has basically the same configuration as the liquid crystal display device 10 shown in FIG. 3, but the third and fourth side walls 15c and 15d of the light guide plate 15A of the backlight device 12A. Is provided with serrated irregularities. The serrated irregularities are small triangular irregularities having a pitch of about 0.5 to 1 mm, and are provided over the entirety of the third and fourth side walls 15c and 15d. Correspondingly, the side walls of the backlight housing are also formed with saw-toothed unevenness, and the unevenness of the light guide plate 15 is configured to mesh with the unevenness of the light guide plate 15A and the backlight housing. When the irregularities of the side wall of the 14 mesh with each other, the light guide plate 15A is restricted so that the movement in the X direction is reduced in addition to the movement in the X direction due to the trapezoidal shape.
[0028]
Further, since the irregularities of the light guide plate 15A are fine irregularities, light is irregularly reflected at the irregularities, and the amount of light returning to the inside of the light guide plate 15A increases. As a result, the illuminance of the backlight device can be increased.
[0029]
The finer the unevenness, the greater the amount of reflection. Thus, unevenness in the vicinity of the corner can be improved by making the unevenness finer in a portion that is likely to be darker than the periphery of the corner of the light guide plate 15A.
[0030]
Next, a modified example of the backlight device 12 according to the above-described first embodiment will be described.
[0031]
FIG. 7 is a plan view of a first modification of the backlight device 12. A backlight device 12B shown in FIG. 7 has the same configuration as the backlight device 12, but differs in that it has a backlight housing 14B (hatched portion) formed of a transparent material. When the backlight housing is formed of a transparent material as described above, light from the surroundings passes through the backlight housing 14B and enters the light guide plate 15, so that the illuminance of the backlight device can be further improved.
[0032]
In particular, in a portion surrounded by a dotted line circle in FIG. 7, light from the light source 16 passes through the backlight housing 14 and enters the light guide plate 15. For this reason, the light from the light source (the portion surrounded by the circle in FIG. 7) that is blocked by the backlight housing due to the trapezoidal light guide plate can be transmitted and guided into the light guide plate 15. Thereby, it is possible to prevent a decrease in illuminance at a corner portion of the backlight device 12B near the light source 16.
[0033]
FIG. 8 is a plan view of a second modification of the backlight device 12. A backlight device 12C shown in FIG. 8 has the same configuration as the backlight device 12, but includes a backlight housing 14C having a quadrangular accommodating portion, and a side wall of the backlight housing 14C and a side wall of the light guide plate 15. The difference is that a transparent member 19 (hatched portion) is provided between them.
[0034]
That is, when the housing portion of the backlight housing 14C is formed in a quadrangular shape, a space is formed between the trapezoidal light guide plate 15 and the third and fourth side walls. The transparent member 19 has a shape that fills this space, and is attached to the inner wall of the backlight housing 14C. Thereby, the light from the light source 16 passes through the transparent member 19 and is introduced into the light guide plate 16, and as described in the first modification shown in FIG. Illuminance can be prevented from decreasing.
[0035]
As described above, the present specification discloses the following inventions.
[0036]
(Supplementary Note 1) A linear light source,
A substantially quadrangular light guide plate arranged with one side facing the light source,
A backlight device having a backlight housing that holds and holds the light source and the light guide plate therein so as to surround the light source,
A length of a first side wall of the light guide plate including a side facing the light source is smaller than a length of a second side wall opposite to the first side wall,
The backlight device according to claim 1, wherein an inner wall of the backlight housing forms a substantially quadrilateral corresponding to a shape of the light guide plate.
[0037]
(Supplementary Note 2) The backlight device according to Supplementary Note 1, wherein
At least one of third and fourth side walls extending between the first side wall and the second side wall of the light guide plate is formed with saw-tooth-like irregularities, and the inner wall of the backlight housing is A backlight device, wherein a serrated shape is formed to engage with the serrated shape.
[0038]
(Supplementary Note 3) The backlight device according to Supplementary Note 2, wherein
The backlight device, wherein the size of the saw-toothed irregularities is smaller near a corner of the light guide plate than near a center.
[0039]
(Supplementary Note 4) The backlight device according to Supplementary Note 1, wherein
A backlight device, wherein the backlight housing is formed of a transparent member.
[0040]
(Supplementary Note 5) The backlight device according to Supplementary Note 1, wherein
A portion of the backlight device for accommodating the light guide plate is formed in a quadrilateral, and third and fourth side walls extending between the first side wall and the second side wall of the light guide plate and the backlight. A backlight device, wherein a transparent member is arranged in a space formed between the light housing and an inner wall of the light housing.
[0041]
(Supplementary Note 6) The backlight device according to Supplementary Note 1, wherein
Each of the third and fourth side walls extending between the first side wall and the second side wall of the light guide plate forms an equal obtuse angle with the first side wall. Backlight device.
[0042]
(Supplementary Note 7) A liquid crystal display device having a liquid crystal panel and a backlight device provided below the liquid crystal panel,
The backlight device includes a linear light source, a substantially quadrangular light guide plate arranged with one side thereof facing the light source, and holds and holds the light source and the light guide plate therein so as to surround the light source and the light guide plate. A backlight housing,
The length of the light incident side wall of the light guide plate facing the light source is smaller than the length of the side wall opposite to the light incident side wall,
A liquid crystal display device, wherein a side wall of the backlight housing forms a substantially quadrilateral corresponding to a shape of the light guide plate.
[0043]
【The invention's effect】
As described above, according to the present invention, when the light guide plate attempts to move to the light source side, both side walls of the backlight housing first contact the light guide plate and do not move any further. Thereby, destruction of the light source due to collision of the light guide plate can be avoided. Since there is no need to provide fixing projections on the light guide plate or fix it with an adhesive, local light emission unevenness of the light guide plate does not occur, and good illumination can be secured as a backlight device. it can.
[Brief description of the drawings]
FIG. 1 is a plan view of an example of a conventional backlight device.
FIG. 2 is a plan view of another example of a conventional backlight device.
FIG. 3 is an exploded perspective view of the liquid crystal display device incorporating the backlight device according to the first embodiment of the present invention.
FIG. 4 is a plan view of the backlight device shown in FIG.
FIG. 5 is an exploded perspective view of a liquid crystal display device incorporating a backlight device according to a second embodiment of the present invention.
6 is a plan view of the backlight device shown in FIG.
FIG. 7 is a plan view of a first modification of the backlight device shown in FIG.
FIG. 8 is a plan view of a second modified example of the backlight device shown in FIG.
[Explanation of symbols]
10, 20 liquid crystal display device 11 liquid crystal panel 12, 12A, 12B, 12C backlight device 13 decorative plate 14, 14A, 14B, 14C backlight housing 15 light guide plate 15a first side wall 15b second side wall 15c third Side wall 15d Fourth side wall 16 Light source 16a Reflector 17 Reflective sheet 18 Optical sheet 19 Transparent member

Claims (5)

A linear light source,
A substantially quadrangular light guide plate arranged with one side facing the light source,
A backlight device having a backlight housing that holds and holds the light source and the light guide plate therein so as to surround the light source,
A length of a first side wall of the light guide plate including a side facing the light source is smaller than a length of a second side wall opposite to the first side wall,
The backlight device according to claim 1, wherein an inner wall of the backlight housing forms a substantially quadrilateral corresponding to a shape of the light guide plate. The backlight device according to claim 1, wherein
At least one of a third and a fourth side wall extending between the first side wall and the second side wall of the light guide plate is formed with a saw-toothed unevenness, and the saw tooth is formed on an inner wall of the backlight housing. A backlight device characterized in that saw-toothed irregularities are formed so as to engage with the irregularities. The backlight device according to claim 1, wherein
A backlight device, wherein the backlight housing is formed of a transparent member. The backlight device according to claim 1, wherein
Each of the third and fourth side walls extending between the first side wall and the second side wall of the light guide plate forms an equal obtuse angle with the first side wall. Backlight device. A liquid crystal display device having a liquid crystal panel and a backlight device provided below the liquid crystal panel,
The backlight device,
A linear light source,
A substantially quadrangular light guide plate arranged with one side facing the light source,
A backlight housing that holds and holds the light source and the light guide plate therein so as to surround the light source and the light guide plate,
The length of the light incident side wall of the light guide plate facing the light source is smaller than the length of the side wall opposite to the light incident side wall,
A liquid crystal display device, wherein a side wall of the backlight housing forms a substantially quadrilateral corresponding to a shape of the light guide plate.

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