JP2005243503A - 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 wherein incident light efficiency to a light guide plate has been elevated while suppressing a thickness increase of a light guide plate even if the number of light emitting tubes is made to be plural. <P>SOLUTION: This is the backlight device provided with the light guide plate 9 and a plurality of light emitting tubes 5, 7 arranged at light incident end face 9a of the light guide plate 9 opposed to each other. The mutually neighboring light emitting tubes 5, 7 are mutually separated, and among these mutually neighboring light emitting tubes 5, 7, the diameter D2 of the light emitting tube 7 positioned on the rear side while taking the light incident end face 9a as the reference in these neighboring light emitting tubes 5, 7 is larger than the diameter D1 of the light emitting tube 5 positioned on the front side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a backlight device that illuminates a liquid crystal panel from the back side and a liquid crystal display device including the backlight device. More specifically, the thickness of a light guide plate is devised by arranging the arrangement of a plurality of arc tubes that are light sources. The present invention relates to a backlight device and a liquid crystal display device in which the light entrance efficiency from the arc tube to the light guide plate is increased while suppressing an increase in the light intensity.

As a light source of a backlight device that illuminates a liquid crystal panel, an arc tube such as a cold cathode fluorescent lamp has been conventionally used. For example, see Patent Document 1.
Japanese Patent Laid-Open No. 10-106329

  In addition, in a backlight device used for a liquid crystal display device of a notebook computer, it is common to use a single arc tube for miniaturization and weight reduction. However, in recent years, in order to improve image quality and brightness. Increasingly, two or more arc tubes are mounted.

  8 and 9 show a conventional example in which two arc tubes 30a and 30b are mounted. The two arc tubes 30 a and 30 b are arranged along the extending direction of the light incident end face 31 a of the light guide plate 31 and are arranged in the thickness direction of the light guide plate 31. The periphery of the arc tubes 30 a and 30 b is covered with a reflector 32.

In Patent Document 2, as shown in FIG. 11, the light incident end face 45a of the light guide plate 45 is inclined, and three arc tubes 44a, 44b, and 44c are arranged in parallel on the inclined face.
JP-A-9-90135

  In the conventional example shown in FIG. 9, since the two light emitting tubes 30a and 30b are arranged in the thickness direction of the light guide plate 31, the light guide plate 31 is thicker than when one light emitting tube is mounted. End up. When the light guide plate 31 made of a transparent resin material such as acrylic resin becomes thicker, it becomes heavier. The increase in thickness and weight of the light guide plate 31 is disadvantageous particularly when applied to a portable device such as a notebook computer.

  Further, in the configuration of Patent Document 2 shown in FIG. 11, the three arc tubes 44 a, 44 b, 44 c are arranged side by side in a direction inclined with respect to the thickness direction of the light guide plate 45, and the thickness direction of the light guide plate 45 is The thickness of the light guide plate 45 required for arranging the three light-emitting tubes 44a, 44b, 44c in parallel can be reduced compared to the case where they are arranged in parallel.

  However, since the adjacent arc tubes 44a and 44b and 44b and 44c are in contact with each other, the light reflected by the reflector 43 cannot pass between the adjacent arc tubes, so that the light incident on the light incident end face 45a is not transmitted. Light incident efficiency is poor. In other words, only light that goes directly from the light emitting tubes 44a, 44b, and 44c to the light incident end face 45a can be used effectively.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a backlight that increases the light incident efficiency to the light guide plate while suppressing an increase in the thickness of the light guide plate even if the number of arc tubes is plural. An apparatus and a liquid crystal display device are provided.

  The backlight device of the present invention includes a plurality of arc tubes arranged to face the light incident end face of the light guide plate, adjacent arc tubes among the plurality of arc tubes are spaced apart from each other, and the light incident end face The dimension of the bulging portion in the thickness direction of the light guide plate of the arc tube located on the rear side with respect to the arc tube located on the front side with respect to the reference is larger than 0 and smaller than the diameter of the arc tube located on the rear side It is characterized by being arranged.

  The liquid crystal display device of the present invention includes a liquid crystal panel, a light guide plate disposed on the back side of the liquid crystal panel, and a plurality of arc tubes arranged to face the light incident end face of the light guide plate. Adjacent arc tubes among the arc tubes are spaced apart from each other and bulged in the thickness direction of the light guide plate of the arc tube located on the rear side with respect to the arc tube located on the front side with respect to the light incident end face It is characterized in that it is arranged so that the dimension thereof is larger than 0 and smaller than the diameter of the arc tube located on the rear side.

  Since the adjacent arc tubes are separated from each other, light that is not directed directly to the light incident end surface (light reflected by the reflector covering the periphery of the arc tube) is directed to the light incident end surface through the gap generated by the separation. Can do. Thereby, the light entrance efficiency to the light incident end face can be improved.

  Among these adjacent arc tubes, the arc tube located on the rear side with respect to the light incident end face bulges in the thickness direction of the light guide plate from the arc tube located on the front side, and the dimension of the bulge portion is The diameter is smaller than the diameter of the arc tube located on the rear side. That is, both the adjacent arc tubes are arranged so that a part of the rear arc tube protrudes from the front arc tube in the light guide plate thickness direction when viewed from the light incident end face side. . As a result, the rear arc tube is not overlapped with the front arc tube as viewed in the thickness direction of the light guide plate by the amount of the bulge. Therefore, in this non-overlapping portion, the light emission located on the rear side The light from the tube is not blocked by the front-side arc tube located immediately in front of the arc tube, and the light incident efficiency to the light incident end face can be increased. This realizes further improvement in the light incident efficiency from the arc tube to the light guide plate in combination with the use of the above-described gap between adjacent arc tubes as a light path.

  In addition, the dimensions of the bulging part are smaller than the diameter of the rear arc tube, that is, they are not displaced so much that all the parts of the rear arc tube protrude from the front arc tube. The increase in the thickness of the light guide plate can be suppressed.

  Further, when the number of arc tubes is three or more, if the bulging direction of the bulging portion described above (a misalignment direction along the thickness direction of the light guide plate) is set to the same direction among a plurality of arc tubes, light is incident. Since a plurality of arc tubes are stacked in the thickness direction of the light guide plate like a staircase when viewed from the end face side, the thickness of the light guide plate increases as the number of arc tubes increases. When there are three or more arc tubes, if the bulge directions of the above-mentioned bulge portions of the second and subsequent arc tubes are alternately reversed with respect to the light incident end face, the light tubes are guided in proportion to the number of arc tubes. It is possible to prevent the thickness of the light plate from increasing.

  In addition to shifting the position of the light guide plate in the thickness direction between adjacent arc tubes as described above, the diameter of the arc tube located on the rear side is made larger than the diameter of the arc tube located on the front side. In this case, the portion where the two do not overlap can be further increased, and the light incident efficiency to the light incident end face can be further improved.

  In addition, the backlight device of the present invention includes a plurality of arc tubes arranged to face the light incident end face of the light guide plate, and the adjacent arc tubes among the plurality of arc tubes are separated from each other. Among these, the diameter of the arc tube located on the rear side with respect to the light incident end face is larger than the diameter of the arc tube located on the front side.

  The liquid crystal display device of the present invention includes a liquid crystal panel, a light guide plate disposed on the back side of the liquid crystal panel, and a plurality of arc tubes arranged to face the light incident end face of the light guide plate. The adjacent arc tubes are spaced apart from each other, and the diameter of the arc tube located on the rear side of the adjacent arc tubes with respect to the light incident end face is larger than the diameter of the arc tube located on the front side. It is characterized by.

  Since the adjacent arc tubes are separated from each other, light that is not directed directly to the light incident end surface (light reflected by the reflector covering the periphery of the arc tube) is directed to the light incident end surface through the gap generated by the separation. Can do. Thereby, the light entrance efficiency to the light incident end face can be improved.

  Further, since the diameter of the arc tube located on the rear side is made larger than the diameter of the arc tube located on the front side, a part of the rear arc tube is seen on the front side arc tube as viewed from the light incident end face side. Protruding from the light guide plate in the thickness direction. As a result, the rear arc tube is not overlapped with the front arc tube as viewed in the thickness direction of the light guide plate by the dimension of the protruding portion. The light from the tube is not blocked by the front-side arc tube located immediately in front of the arc tube, and the light incident efficiency to the light incident end face can be increased. This realizes further improvement in the light incident efficiency from the arc tube to the light guide plate in combination with the use of the above-described gap between adjacent arc tubes as a light path.

  According to the backlight device of the present invention, it is possible to increase the thickness and weight of the light guide plate by using the light from the arc tubes arranged behind the arc tube arranged at the position closest to the light incident end face. It is possible to improve while suppressing. By improving the light utilization efficiency, it is possible to suppress heat generation at the location where the arc tube is arranged.

  According to the liquid crystal display device of the present invention, it is possible to increase the thickness and weight of the light guide plate by using light from the luminous tubes arranged in parallel behind the luminous tube arranged at the position closest to the light incident end face. It is possible to improve while suppressing. As a result, it is possible to prevent the luminance of the liquid crystal panel from being lowered. In addition, the heat utilization efficiency can be improved, so that heat generation at the arc tube arrangement location can be suppressed, and deterioration of the image quality of the liquid crystal panel due to the heat generation is suppressed.

[First Embodiment]
FIG. 1 is a schematic plan view of a liquid crystal display device 1 according to the present embodiment. The liquid crystal display device 1 is disposed so as to face a rectangular liquid crystal panel 3, a light guide plate disposed on the back side of the liquid crystal panel 3, and a light incident end surface (lower end surface in FIG. 1) of the light guide plate. A plurality of (for example, two in this embodiment) arc tubes 5 and 7 are provided.

  FIG. 6 is a schematic cross-sectional view of the liquid crystal display device 1. Between the liquid crystal panel 3 and the light guide plate 9, optical sheets such as a prism sheet 25b and a diffusion sheet 25a are disposed. A reflective sheet 24 is disposed on the back surface of the light guide plate 9. The periphery of the arc tubes 5 and 7 is covered with a reflector 11.

  The light emitting tubes 5 and 7, the reflector 11, the light guide plate 9, the reflection sheet 24, the optical sheets 25a and 25b, and the like constitute the backlight device according to this embodiment.

  FIG. 7 is an exploded perspective view of the liquid crystal display device 1. The liquid crystal panel 3 encloses a liquid crystal material in two glass substrates 38 and 39, forms a color filter on the upper (display screen side) glass substrate 38, and the lower (light guide plate 9 side) glass substrate 39. Is formed with thin film transistors, and polarizing plates 37a and 37b having a function of passing light in one direction and shielding light in the other direction by absorption, reflection or scattering are disposed outside the upper and lower glass substrates 38 and 39, respectively. Configured.

  In addition, the liquid crystal display device 1 further includes a circuit board 47 on which a driving integrated circuit (driver IC) 46 for driving the liquid crystal panel 3 and a controller (control integrated circuit) for controlling them are mounted. .

  As shown in FIG. 6, the light guide plate 9 is made of a transparent resin material such as an acrylic resin having reflective dots 9 b formed on the bottom surface. One end surface (left end surface in FIG. 6) of the light guide plate 9 is a light incident end surface 9a that receives light from the arc tubes 5 and 7.

  As shown in FIG. 1, both the luminous tubes 5 and 7 extend in parallel along the lower end portion of the liquid crystal panel 3 (the portion corresponding to the light incident end surface 9a of the light guide plate 9). As the arc tubes 5 and 7, a hot cathode fluorescent lamp that discharges thermoelectrons by heating with a filament or a cold cathode fluorescent lamp that discharges by applying a high voltage without heating when discharging is used. However, the latter is preferable as the light source of the backlight device of the liquid crystal display device because the tube is thin and the lifetime is relatively long.

  As shown in FIG. 2, the two arc tubes 5 and 7 are arranged to be separated from each other along a direction (arrow A direction) perpendicular to the light incident end surface 9 a of the light guide plate 9. The arc tube 5 is disposed on the side close to the light incident end face 9 a, and the arc tube 7 is disposed behind the arc tube 5. That is, the arc tube 5 is disposed between the light incident end face 9 a and the arc tube 7.

  As shown in FIG. 2, the arc tube 5 and the arc tube 7 have a circular cross section. The arc tube 5 has a diameter D1 of, for example, 1.8 mm, and the arc tube 7 has a diameter D2 of, for example, 2.0 mm. That is, in the adjacent arc tubes 5 and 7, the diameter D2 of the arc tube 7 positioned on the rear side is made larger than the diameter D1 of the arc tube 5 positioned on the front side with respect to the light incident end face 9a. . A line connecting the central axes of the arc tubes 5 and 7 is parallel to a direction (arrow A direction) perpendicular to the light incident end face 9a.

  A reflector 11 covers the periphery of the arc tubes 5 and 7. The reflector 11 guides the light emitted from the arc tubes 5 and 7 to the light incident end face 9a of the light guide plate 9 without leaking to the surroundings. As shown in FIG. 1, the arc tube 5 is provided with, for example, rubber rings 41 at two locations, and the light emission 7 is also provided with, for example, rubber rings 42 at two locations. These rings 41 and 42 function as spacers that maintain a predetermined distance between the arc tubes 5 and 7 and the reflector 11 and between the arc tube 5 and the arc tube 7. The ring is not limited to rubber but may be made of resin. The positions of the ring 41 and the ring 42 along the longitudinal direction of the arc tube are shifted so as not to collide with each other.

  By maintaining the gaps between the arc tubes 5 and 7 and the reflector 11 and between the arc tube 5 and the arc tube 7 at a predetermined size, the reflectors 11 of the light emitted from the arc tubes 5 and 7 are used. The light incident efficiency to the light incident end face 9a is increased by effectively using the reflection of the light, and the light emission efficiency can be prevented from being lowered due to mutual heat generation due to the distance between the light emitting tubes 5 and 7 being too close.

  Further, as shown in FIG. 1, holders 40 are attached to both ends of both the arc tubes 5 and 7. The holder 40 is made of, for example, rubber or resin, and has holes corresponding to the thicknesses of both end portions of both the arc tubes 5 and 7. Both arc tubes 5 and 7 are positioned and held in the case with both ends fitted into the holes.

  When electric power is supplied to the arc tube 5 and the arc tube 7, light is emitted from the arc tubes 5 and 7. Light emitted from each arc tube 5, 7 is repeatedly reflected by the reflector 11 or directly enters the light incident end face 9 a of the light guide plate 9.

  At this time, since the adjacent arc tubes 5 and 7 are separated from each other, the light not directly directed to the light incident end face 9a through the gap generated by the separation, that is, reflected by the reflector 11 covering the periphery of the arc tubes 5 and 7 is reflected. The emitted light can be directed to the light incident end face 9a as shown by a one-dot chain line in FIG. Thereby, the light-incidence efficiency to the light-incidence end surface 9a can be improved.

  Furthermore, since the rear arc tube 7 has a larger diameter than the front arc tube 5, the light from the rear arc tube 7 is blocked by the front arc tube 5 compared to the case where the diameter is the same in both. Therefore, it is possible to increase the number of components that enter the light incident end face 9a and to increase the light incident efficiency to the light incident end face 9a. As a result, the amount of surface light emitted from the light guide plate 9 toward the liquid crystal panel 3 can be increased, and a reduction in luminance of the liquid crystal panel 3 can be prevented.

  Furthermore, in this embodiment, since both the light-emitting tubes 5 and 7 are not arranged in the thickness direction of the light guide plate 9, an increase in the thickness of the light guide plate 9 can be suppressed, and an increase in the weight of the light guide plate 9 can be suppressed accordingly. As a result, an increase in thickness and weight of the entire backlight device and the entire liquid crystal display device can be suppressed.

  The light incident from the light incident end surface 9a is uniformly directed toward the liquid crystal panel 3 by the reflective dots 9b (see FIG. 6) formed on the light guide plate 9 or the reflective sheet 24 disposed on the back surface of the light guide plate 9. Reflected. The light emitted from the light guide plate 9 is incident on the liquid crystal panel 3 with its direction changed by the diffusion sheet 25a and the prism sheet 25b so that the light enters the liquid crystal panel 3 almost perpendicularly.

  The diameters of the above-mentioned arc tubes 5 and 7 can be arbitrarily set. For example, the diameters of 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2 mm, which are already existing as arc tube for an existing backlight device, If an appropriate combination is selected from 4 mm, it is not necessary to design and manufacture a new arc tube.

  In general, an arc tube such as a cold cathode fluorescent lamp has a higher impedance than a smaller one, and the smaller the diameter, the smaller the diameter of the arc tube, the higher the applied voltage. Get higher. Therefore, if the impedance of each arc tube and the driver (inverter) that supplies electric power to each arc tube are mismatched, the operation efficiency of the inverter may be reduced.

  Therefore, in the present embodiment, as shown in FIG. 7, the arc tube 5 having a small diameter uses a driver 28 appropriately matched to the impedance of the arc tube 5, and the arc tube 7 having a large diameter has this By using the driver 27 that is appropriately matched to the impedance of the arc tube 7, it is possible to prevent the efficiency of the driver from decreasing and the amount of heat generation from increasing.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same component as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  FIG. 3 shows the arrangement relationship of the arc tubes 13 and 15 according to this embodiment. Each arc tube 13 and 15 is, for example, a cold cathode fluorescent lamp, as in the first embodiment. Both the luminous tubes 13 and 15 extend in parallel along the lower end portion of the liquid crystal panel 3 (the portion corresponding to the light incident end face 9a of the light guide plate 9).

  The two arc tubes 13 and 15 are arranged apart from each other along a direction (arrow A direction) perpendicular to the light incident end surface 9 a of the light guide plate 9. An arc tube 13 is disposed near the light incident end face 9a, and an arc tube 15 is disposed behind the arc tube 13. That is, the arc tube 13 is disposed between the light incident end face 9 a and the arc tube 15.

  Both the arc tube 13 and the arc tube 15 have a circular cross section and the same diameter, for example, a diameter of 2 mm. The positions of the light emitting tubes 13 and 15 in the thickness direction of the light guide plate 9 are shifted. That is, the line connecting the central axes of the arc tubes 13 and 15 is not parallel to the direction perpendicular to the light incident end face 9a (the direction of arrow A).

  In addition, the light-emitting tubes 13 and 15 are displaced so that positions along the thickness direction of the light guide plate 9 have portions that overlap each other and portions that do not overlap each other. That is, the dimension t1 of the portion where the rear arc tube 15 bulges in the light guide plate thickness direction with respect to the front arc tube 13 with respect to the light incident end face 9a is greater than 0, and It is smaller than the diameter d of the arc tube 15.

  A dimension t1 of the bulged portion in the thickness direction of the light guide plate is, for example, 0.5 mm. The dimension t2 in the light guide plate thickness direction of the portion where both the arc tubes 13 and 15 overlap is made larger than the above t1.

  When electric power is supplied to the arc tube 13 and the arc tube 15, light is emitted from the arc tubes 13 and 15. Light emitted from each of the arc tubes 13 and 15 is repeatedly reflected by the reflector 11 or directly incident on the light incident end face 9 a of the light guide plate 9.

  Here, the arrangement relationship of the arc tubes 13 and 15 of this embodiment will be described in comparison with the comparative example shown in FIG. In FIG. 10, the two arc tubes 34 a and 34 b are arranged side by side along a direction (lateral direction in FIG. 10) perpendicular to the light incident end surface 33 a of the light guide plate 33. Both the arc tubes 34a and 34b have the same diameter, and both are positioned so as to overlap each other when viewed from the light incident end face 33a side. The periphery of the arc tubes 34 a and 34 b is covered with a reflector 36. In this comparative example, the thickness of the light guide plate 33 does not increase as compared with the case where one arc tube is mounted, but the light emitted from the arc tube 34b arranged on the rear side when viewed from the light incident end face 33a side. Is largely blocked by the front arc tube 34a, and the amount of light incident on the light incident end face 33a is reduced, resulting in a decrease in the luminance of the liquid crystal panel. To compensate for this, if the amount of light emitted from the arc tube 34b is increased too much, the amount of heat generation increases, and this heat generation may cause uneven brightness.

  On the other hand, in the present embodiment, as shown in FIG. 3, both arc tubes are arranged such that a part of the rear arc tube 15 bulges in the light guide plate thickness direction with respect to the front arc tube 13. 13 and 15 are shifted in the thickness direction of the light guide plate 9 to produce a portion where they do not overlap. Therefore, compared to the conventional example shown in FIG. Light incident efficiency on the end face 9a can be increased. As a result, the amount of surface light emitted from the light guide plate 9 toward the liquid crystal panel 3 can be increased, and a reduction in luminance of the liquid crystal panel 3 can be prevented.

  Furthermore, the dimension t1 of the bulging portion is suppressed to be smaller than the diameter of the rear arc tube 15, that is, the rear arc tube 15 is not positioned as indicated by a one-dot chain line in FIG. The increase in the thickness of the light guide plate 9 can be suppressed, and the increase in the weight of the light guide plate 9 can be suppressed accordingly. As a result, an increase in thickness and weight of the entire backlight device and the entire liquid crystal display device can be suppressed.

  Further, since the adjacent arc tubes 13 and 15 are separated from each other, the light that does not go directly to the light incident end surface 9a through the gap generated by the separation, that is, the light reflected by the reflector 11 that covers the periphery of the arc tubes 13 and 15 is reflected. The light can be directed to the light incident end face 9a as shown by the one-dot chain line shown in FIG. 2 in the first embodiment. Also by this, the light entrance efficiency to the light incident end face 9a can be improved.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same component as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  FIG. 4 shows the arrangement relationship of the three arc tubes 17, 18, 19 according to the present embodiment. Each arc tube 17, 18, 19 is, for example, a cold cathode fluorescent lamp. All the arc tubes 17, 18, 19 extend in parallel along the lower end portion of the liquid crystal panel 3 (the portion corresponding to the light incident end surface 9 a of the light guide plate 9).

  Each arc tube 17, 18, 19 is aligned along a direction (arrow A direction) perpendicular to the light incident end face 9 a of the light guide plate 9. Adjacent arc tubes are separated from each other. The arc tube 17 is disposed on the side closest to the light incident end face 9a, the arc tube 18 is disposed behind the arc tube 17, and the arc tube 19 is disposed behind the arc tube. That is, the arc tube 17 is disposed between the light incident end face 9 a and the arc tube 18, and the arc tube 18 is disposed between the arc tube 17 and the arc tube 19.

  Each arc tube 17, 18, and 19 has a circular cross section and an equal diameter, for example, 2 mm in diameter. Among the arc tubes 17, 18, and 19, the adjacent arc tubes are displaced in the thickness direction of the light guide plate 9. That is, a part of the arc tube 18 bulges upward in FIG. 4 with respect to the arc tube 17, and a part of the arc tube 19 bulges downward in FIG. The bulging directions of the bulged portions of the second and subsequent arc tubes 18 and 19 are alternately reversed with reference to the light incident end face 9a. A line connecting the central axis of each arc tube 17, 18, 19 is a mountain line as shown by a one-dot chain line in FIG. 4, and is parallel to a direction (arrow A direction) perpendicular to the light incident end face 9a. is not.

  The adjacent arc tubes 17 and 18 are shifted so that positions along the thickness direction of the light guide plate 9 overlap with each other and portions that do not overlap each other. That is, the dimension t3 of the portion in which the rear arc tube 18 bulges in the light guide plate thickness direction with respect to the front arc tube 17 with respect to the light incident end face 9a is greater than 0, and It is smaller than the diameter d of the arc tube 18.

  Similarly, the adjacent arc tubes 18 and 19 are displaced so that the positions along the thickness direction of the light guide plate 9 have portions that overlap each other and portions that do not overlap each other. That is, the dimension t4 of the portion where the rear arc tube 19 bulges in the light guide plate thickness direction with respect to the front arc tube 18 with respect to the light incident end face 9a is greater than 0, and It is smaller than the diameter d of the arc tube 19.

  When electric power is supplied to each arc tube 17, 18, 19, light is emitted from each arc tube 17, 18, 19. The light emitted from each arc tube 17, 18, 19 is repeatedly reflected by the reflector 11 or directly enters the light incident end face 9 a of the light guide plate 9.

  At this time, the arc tubes 17 and 18 are displaced in the thickness direction of the light guide plate 9 to generate a portion where they do not overlap, so that the light from the rear arc tube 18 enters the light incident end face 9a. The light incident efficiency can be increased, and the arc tubes 18 and 19 are also displaced from each other in the thickness direction of the light guide plate 9 so that the portions do not overlap with each other. It is possible to increase the light incident efficiency of the light to the light incident end face 9a. As a result, the amount of surface light emitted from the light guide plate 9 toward the liquid crystal panel 3 can be increased, and a reduction in luminance of the liquid crystal panel 3 can be prevented.

  Further, since the adjacent arc tubes are separated from each other, the light not directly directed to the light incident end face 9a, that is, the light reflected by the reflector 11 through the gap generated by the separation is shown in FIG. 2 in the first embodiment. It can be made to face to the light-incidence end surface 9a like the dashed-dotted line shown by. Also by this, the light entrance efficiency to the light incident end face 9a can be improved.

  Furthermore, in the present embodiment, the first arc tube 17 and the third arc tube 19 as counted from the light incident end face 9a side are positioned so as to be moved downward in FIG. 4, and the second arc tube 18 is In contrast to the arc tubes 17 and 19, they are positioned so as to be moved upward in FIG. 4, so that the second and third arc tubes 18 and 19 are both shifted upward or downward stepwise (see FIG. 4). As compared with the conventional example shown in FIG. 11, an increase in the thickness of the light guide plate 9 can be suppressed. Note that the second arc tube 18 may be shifted downward in FIG. 4, and the third arc tube 19 may be shifted upward in FIG.

  As an example requiring three arc tubes, in addition to simply improving the luminance, a backlight device using a continuous additive color mixing (field sequential) method is conceivable. In this method, three light emitting tubes for red, blue and green light emission are sequentially irradiated, and the liquid crystal dots are repeatedly turned on / off in synchronization with this. For example, when displaying the liquid crystal dots in red, the liquid crystal dots of the pixels to be displayed in red are opened when red light is emitted from the red arc tube. Also, when displaying the liquid crystal dots in white, when the red, blue, and green arc tubes emit light and the liquid crystal dots that you want to display are opened, the afterimage phenomenon of the human eye (brain) causes red, blue, and green Light overlaps in the brain and appears white on the principle of the three primary colors. As the arrangement of the three light emitting tubes in this case, for example, the blue light emitting tube having the lowest luminous efficiency is positioned closest to the light incident end face, the red light emitting tube is behind it, and the green light emitting tube is behind this. Arrange the arc tube.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same component as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  FIG. 5 shows the arrangement relationship of the three arc tubes 20, 21, and 22 according to this embodiment. Each arc tube 20, 21, 22 is, for example, a cold cathode fluorescent lamp. All the arc tubes 20, 21, and 22 extend in parallel along the lower end portion of the liquid crystal panel 3 (the portion corresponding to the light incident end surface 9a of the light guide plate 9).

  Each arc tube 20, 21, 22 is aligned along a direction (arrow A direction) perpendicular to the light incident end face 9 a of the light guide plate 9. Adjacent arc tubes are separated from each other. The arc tube 20 is disposed on the side closest to the light incident end face 9a, the arc tube 21 is disposed behind the arc tube 20, and the arc tube 22 is disposed behind the arc tube. That is, the arc tube 20 is disposed between the light incident end face 9 a and the arc tube 21, and the arc tube 21 is disposed between the arc tube 20 and the arc tube 22.

  Each arc tube 20, 21 and 22 has a circular cross section. The diameters D3, D4, and D5 of each arc tube 20, 21, and 22 are D3 <D4 <D5. Alternatively, D3 <D4 = D5, and further D3 = D4 <D5 may be set. Among the arc tubes 20, 21, and 22, adjacent arc tubes are displaced in the thickness direction of the light guide plate 9. That is, a part of the arc tube 21 bulges upward in FIG. 5 with respect to the arc tube 20, and a part of the arc tube 22 bulges downward with respect to the arc tube 21 in FIG. The bulging directions of the bulged portions of the second and subsequent arc tubes 21 and 22 are alternately reversed with reference to the light incident end face 9a. A line connecting the central axes of the arc tubes 20, 21, and 22 is a mountain line as shown by a one-dot chain line in FIG. 5, and is parallel to a direction perpendicular to the light incident end face 9a (arrow A direction). is not.

  Adjacent arc tubes 20 and 21 are displaced so that positions along the thickness direction of the light guide plate 9 are overlapped and non-overlapped. That is, the dimension t5 of the portion where the rear arc tube 21 bulges in the light guide plate thickness direction with respect to the front arc tube 20 with respect to the light incident end face 9a is greater than 0, and It is smaller than the diameter D4 of the arc tube 21.

  Similarly, the light emitting tubes 21 and 22 adjacent to each other are displaced so that positions along the thickness direction of the light guide plate 9 are overlapped and non-overlapped. That is, the dimension t6 of the portion where the rear arc tube 22 bulges in the light guide plate thickness direction with respect to the front arc tube 21 with respect to the light incident end face 9a is greater than 0, and It is smaller than the diameter D5 of the arc tube 22.

  When power is supplied to each arc tube 20, 21, 22, light is emitted from each arc tube 20, 21, 22. Light emitted from each arc tube 20, 21, 22 is repeatedly reflected by the reflector 11 or directly enters the light incident end face 9 a of the light guide plate 9.

  At this time, the arc tubes 20 and 21 are shifted in the thickness direction of the light guide plate 9 to generate a portion where they do not overlap. Therefore, the light from the rear arc tube 21 enters the light incident end face 9a. The light incident efficiency can be increased, and the light emitting tubes 21 and 22 are shifted in the thickness direction of the light guide plate 9 to generate a portion where they do not overlap. It is possible to increase the light incident efficiency of the light to the light incident end face 9a. Furthermore, in this embodiment, since the diameter of the arc tube on the back side is made larger at least between the adjacent arc tubes, this also makes it possible to enlarge the non-overlapping portion, and the light emission on the back side The light entrance efficiency of the light from the tube to the light incident end face 9a can be further enhanced by the synergistic effect of shifting the position and changing the diameter.

  Further, since the adjacent arc tubes are separated from each other, the light not directly directed to the light incident end face 9a, that is, the light reflected by the reflector 11 through the gap generated by the separation is shown in FIG. 2 in the first embodiment. It can be made to face to the light-incidence end surface 9a like the dashed-dotted line shown by. Also by this, the light entrance efficiency to the light incident end face 9a can be improved.

  In the present embodiment, as in the third embodiment, the first arc tube 20 and the third arc tube 22 counted from the light incident end face 9a side are positioned so as to be moved downward in FIG. Since the second arc tube 21 is positioned so as to be moved upward in FIG. 5 in contrast to the arc tubes 20 and 22, both the second and third arc tubes 21 and 22 are stepped upward or downward. As compared with the case where the position is shifted to (the conventional example shown in FIG. 11), an increase in the thickness of the light guide plate 9 can be suppressed. The second arc tube 21 may be shifted downward in FIG. 5, and the third arc tube 22 may be shifted upward in FIG.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  You may combine 1st Embodiment shown in FIG. 2, and 2nd Embodiment shown in FIG. Further, the number of arc tubes may be four or more.

  Specific examples of the liquid crystal display device include a notebook computer, a portable information terminal, an electronic still camera, a video camera, a monitor, and other devices equipped with a plurality of arc tubes as light sources.

1 is a schematic plan view of a liquid crystal display device according to a first embodiment of the present invention. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube which concerns on the 4th Embodiment of this invention. 1 is a schematic cross-sectional view of a backlight device according to an embodiment of the present invention and a liquid crystal display device including the backlight device. 1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention. It is a model top view of the liquid crystal display device of a prior art example. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube in the prior art example. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube in a comparative example. It is a schematic diagram which shows the arrangement | positioning relationship of the some arc tube in another prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 3 ... Liquid crystal panel, 5 ... Light emission tube, 7 ... Light emission tube, 9 ... Light guide plate, 9a ... Light incident end surface, 11 ... Reflector, 13 ... Light emission tube, 15 ... Light emission tube, 17 ... Light emission tube 18 ... arc tube, 19 ... arc tube, 20 ... arc tube, 21 ... arc tube, 22 ... arc tube, 27, 28 ... driver for arc tube, 40 ... rubber holder, 41 ... rubber ring, 42 ... rubber ring.

Claims (8)

A backlight device comprising a light guide plate and a plurality of arc tubes arranged to face the light incident end face of the light guide plate,
Adjacent ones of the plurality of arc tubes are spaced apart from each other and in the thickness direction of the light guide plate of the arc tube located on the rear side with respect to the arc tube located on the front side with respect to the light incident end face. The backlight device is characterized in that the size of the bulging portion is larger than 0 and smaller than the diameter of the arc tube located on the rear side. 2. The bulging direction of the bulging portion of the second and subsequent arc tubes is alternately reversed with respect to the light incident end face when there are three or more arc tubes. Backlight device. 2. The backlight device according to claim 1, wherein, in the adjacent arc tubes, a diameter of the arc tube located on the rear side is larger than a diameter of the arc tube located on the front side. A backlight device comprising a light guide plate and a plurality of arc tubes arranged to face the light incident end face of the light guide plate,
Among the plurality of arc tubes, adjacent arc tubes are separated from each other, and among these adjacent arc tubes, the diameter of the arc tube located on the rear side with respect to the light incident end surface is the diameter of the arc tube located on the front side. A backlight device characterized by being larger. A liquid crystal display device comprising: a liquid crystal panel; a light guide plate disposed on a back side of the liquid crystal panel; and a plurality of arc tubes arranged to face the light incident end surface of the light guide plate,
Adjacent ones of the plurality of arc tubes are spaced apart from each other and in the thickness direction of the light guide plate of the arc tube located on the rear side with respect to the arc tube located on the front side with respect to the light incident end face. The liquid crystal display device is characterized in that the size of the bulging portion is arranged to be larger than 0 and smaller than the diameter of the arc tube located on the rear side. The bulging direction of the bulging portion of the second and subsequent arc tubes is alternately reversed with the light incident end face as a reference when the number of arc tubes is three or more. Liquid crystal display device. 6. The liquid crystal display device according to claim 5, wherein, in the adjacent arc tubes, a diameter of the arc tube located on the rear side is larger than a diameter of the arc tube located on the front side. A liquid crystal display device comprising: a liquid crystal panel; a light guide plate disposed on a back side of the liquid crystal panel; and a plurality of arc tubes arranged to face the light incident end surface of the light guide plate,
Among the plurality of arc tubes, adjacent arc tubes are separated from each other, and among these adjacent arc tubes, the diameter of the arc tube located on the rear side with respect to the light incident end surface is the diameter of the arc tube located on the front side. A liquid crystal display device characterized by being larger.

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