JP5161449B2 - Liquid crystal display device and backlight - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a direct type backlight and a liquid crystal display device using the same.

  The use of liquid crystal display devices has expanded to the field of large display devices such as TVs. In a large display device, a direct type backlight is often used in order to obtain sufficient brightness. A fluorescent tube is mainly used as a light source of the backlight. In order to accommodate a large screen, the fluorescent tube becomes long. Further, the luminous efficiency is better when the diameter of the fluorescent tube is smaller. Therefore, many thin and long fluorescent tubes are used in a large-screen liquid crystal display device.

  Since the thin and long fluorescent tube is mechanically unstable, an intermediate holder is used in the middle of the terminal portion that supports the fluorescent tube. This intermediate holder affects the light emission of the fluorescent tube and may cause unevenness of the backlight. “Patent Document 1” is an example of reducing the influence on the uneven brightness of the intermediate holder. Further, “Patent Document 2” is cited as a device that devises a direct-type backlight structure to facilitate the production of a direct-type backlight.

JP 2004-318176 A JP 2006-114445 A

  In a display device such as a TV, in addition to simply displaying an image, a speaker is often built in the device. In this case, vibration due to sound from the speaker affects the backlight. When the fluorescent tube is thin and long, this vibration affects variously.

  The intermediate holder described in “Patent Document 1” reduces the influence of the intermediate holder on the luminance when a thin and long fluorescent tube is supported by the intermediate holder. However, with respect to vibration due to sound as described above, there arises a problem that another new sound is generated due to the interaction between the intermediate holder and the fluorescent tube. This is recognized as noise. Such a problem is not described in “Patent Document 1”.

  On the other hand, even if there is no built-in speaker, if there is an AC power supply that generates a certain frequency in the display device, the fluorescent tube resonates with this AC, causing interference with the intermediate holder and noise. It may occur.

  The present invention is to take measures against noise caused by vibration of a fluorescent tube due to electromagnetic waves from a speaker or an AC power source as described above.

  In order to support the fluorescent tube in the middle, an intermediate holder is used. The inner diameter of the portion of the holder that accommodates the fluorescent tube is increased in advance in order to insert the fluorescent tube. In the present invention, it has been found that the difference between the outer shape of the fluorescent tube and the inner diameter of the intermediate holder is a cause of noise. In order to prevent this, the present invention adopts the following configuration.

(1) A liquid crystal display device having a liquid crystal display panel and a backlight including at least two fluorescent tubes, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and the middle of the fluorescent tube The portion is supported by an intermediate holder capable of supporting two fluorescent tubes, and the distance between the two fluorescent tubes supported by the intermediate holder is greater than the distance at the connection support portion with the frame. A liquid crystal display device characterized in that the distance at is larger.
(2) The liquid crystal display device according to (1), wherein the distance between the two fluorescent tubes is 0.4 mm or more greater than the distance at the attachment portion with the frame.
(3) The liquid crystal display device according to (1), wherein the material of the intermediate holder has a larger coefficient of thermal expansion than the material of the frame.
(4) When the tolerance of the diameter of the fluorescent tube is ± a and the tolerance of the inner diameter of the intermediate holder accommodating the fluorescent tube is ± b, the distance between the two fluorescent tubes is (2) The liquid crystal display device according to (1), wherein the distance in the intermediate holder is 2 × (a + b) or more than the distance in the connection support portion.

(5) A liquid crystal display device having a liquid crystal display panel and a backlight including at least two fluorescent tubes, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and the middle of the fluorescent tube The portion is supported by an intermediate holder capable of supporting two fluorescent tubes, and the distance between the two fluorescent tubes supported by the intermediate holder is greater than the distance in the connection support portion with the frame. A liquid crystal display device characterized in that the distance at is smaller.
(6) The liquid crystal display device according to (5), wherein the distance between the two fluorescent tubes is 0.4 mm or more smaller than the distance at the attachment portion with the frame.
(7) The liquid crystal display device according to (5), wherein the material of the intermediate holder has a larger coefficient of thermal expansion than the material of the frame.
(8) When the tolerance of the diameter of the fluorescent tube is ± a and the tolerance of the inner diameter of the portion of the intermediate holder that accommodates the fluorescent tube is ± b, the distance between the two fluorescent tubes is (5) The liquid crystal display device according to (5), wherein the distance in the intermediate holder is 2 × (a + b) or less than the distance in the connection support portion.

(9) A backlight for a liquid crystal display device including at least two fluorescent tubes, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and the intermediate portion of the fluorescent tube has two The distance between the two fluorescent tubes supported by the intermediate holder that can support the fluorescent tubes and supported by the intermediate holder is larger at the intermediate holder than at the connection support portion with the frame. Backlight characterized by that.
(10) The backlight according to claim 9, wherein the distance between the two fluorescent tubes is 0.4 mm or more greater than the distance at the attachment portion with the frame at the intermediate holder.

(11) A backlight for a liquid crystal display device including at least two fluorescent tubes, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and the intermediate portion of the fluorescent tube has two The distance between the two fluorescent tubes supported by the intermediate holder that can support the fluorescent tube and the intermediate holder is smaller than the distance in the connection support portion with the frame. Backlight characterized by that.
(12) The backlight according to claim 11, wherein the distance between the two fluorescent tubes is 0.4 mm or more smaller than the distance between the intermediate holder and the attachment portion with the frame.

(13) A liquid crystal display device having a backlight including a liquid crystal display panel and a fluorescent tube, wherein both ends of the fluorescent tube are supported by the frame by connection support portions to the frame, and an intermediate portion of the fluorescent tube is the fluorescent tube The distance between the fluorescent tube and the center line in the direction parallel to the fluorescent tube of the frame is greater in the intermediate holder than in the connection support portion with the frame. A liquid crystal display device characterized by being large.
(14) The distance between the center line of the frame in the direction parallel to the fluorescent tube and the fluorescent tube is 0.4 mm or more larger in the intermediate holder than in the connection support portion with the frame. The liquid crystal display device according to (13).
(15) The tolerance of the diameter of the fluorescent tube is ± a, the intersection of the inner diameters of the portions of the intermediate holder that accommodate the fluorescent tube is ± b, the center line of the frame in a direction parallel to the fluorescent tube, and the When the mounting tolerance of the intermediate holder is ± c, and the tolerance of the connection support portion between the center line of the frame parallel to the fluorescent tube and the frame of the fluorescent tube is ± d, the fluorescent tube of the frame The distance between the center line in the parallel direction and the fluorescent tube is (a + b + c + d) or more larger in the intermediate holder than in the connection support portion with the frame. (13) .

(16) In a liquid crystal display device having a backlight including a liquid crystal display panel and a fluorescent tube, both ends of the fluorescent tube are supported by the frame by connection support portions to the frame, and an intermediate portion of the fluorescent tube supports the fluorescent tube The distance between the fluorescent tube and the center line in the direction parallel to the fluorescent tube of the frame supported by the intermediate holder can be smaller in the intermediate holder than in the connection support portion with the frame. A liquid crystal display device.
(17) The distance between the center line of the frame in the direction parallel to the fluorescent tube and the fluorescent tube is 0.4 mm or more smaller in the intermediate holder than in the connection support portion with the frame. The liquid crystal display device according to (16).
(18) The tolerance of the diameter of the fluorescent tube is ± a, the intersection of the inner diameters of the portions of the intermediate holder that accommodate the fluorescent tube is ± b, and the center line of the frame in a direction parallel to the fluorescent tube When the mounting tolerance of the intermediate holder is ± c, and the tolerance of the connection support portion between the center line of the frame parallel to the fluorescent tube and the frame of the fluorescent tube is ± d, the fluorescent tube of the frame The distance between the center line in the parallel direction and the fluorescent tube is (a + b + c + d) or less smaller in the intermediate holder than in the connection support portion with the frame. .

(19) A backlight for a liquid crystal display device including a fluorescent tube, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube supports the fluorescent tube. The distance between the fluorescent tube and the center line in the direction parallel to the fluorescent tube of the frame is supported by the intermediate holder that can be larger than that in the connection support portion with the frame. Back light.
(20) The distance between the center line of the frame in a direction parallel to the fluorescent tube and the fluorescent tube is 0.4 mm or more in the intermediate holder than in the connection support portion with the frame. The backlight according to (19).
(21) The tolerance of the diameter of the fluorescent tube is ± a, the intersection of the inner diameters of the portions of the intermediate holder that accommodate the fluorescent tube is ± b, the center line of the frame in a direction parallel to the fluorescent tube, and the When the mounting tolerance of the intermediate holder is ± c, and the tolerance of the connection support portion between the center line of the frame parallel to the fluorescent tube and the frame of the fluorescent tube is ± d, the fluorescent tube of the frame The backlight according to (19), wherein a distance between a center line in a parallel direction and the fluorescent tube is greater by (a + b + c + d) or more in the intermediate holder than in a connection support portion with the frame.

(22) A liquid crystal display backlight including a fluorescent tube, wherein both ends of the fluorescent tube are supported by the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube can support the fluorescent tube The distance between the fluorescent tube and the center line in the direction parallel to the fluorescent tube of the frame supported by the intermediate holder is smaller in the intermediate holder than in the connection support portion with the frame. Backlight.
(23) The distance between the center line of the frame in the direction parallel to the fluorescent tube and the fluorescent tube is 0.4 mm or more smaller in the intermediate holder than in the connection support portion with the frame. The backlight according to (22).
(24) The tolerance of the diameter of the fluorescent tube is ± a, the intersection of the inner diameters of the portions of the intermediate holder that accommodate the fluorescent tube is ± b, the center line of the frame in a direction parallel to the fluorescent tube, and the When the mounting tolerance of the intermediate holder is ± c, and the tolerance of the connection support portion between the center line of the frame parallel to the fluorescent tube and the frame of the fluorescent tube is ± d, the fluorescent tube of the frame The backlight according to (22), wherein the distance between the center line in the parallel direction and the fluorescent tube is smaller by (a + b + c + d) or more in the intermediate holder than in the connection support portion with the frame.

  According to the means (1) to (4), the two fluorescent tubes in the liquid crystal display device are always pressed to the outside in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube, so that the sound from the outside No noise is generated between the fluorescent tube and the intermediate holder even if such vibrations are applied.

  According to the means (5) to (8), the two fluorescent tubes in the liquid crystal display device are always pressed inside the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tubes, so that the sound from the outside No noise is generated between the fluorescent tube and the intermediate holder even if such vibrations are applied.

  According to the means (9) and (10), the two fluorescent tubes in the backlight are always pressed to the outside in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube, so that the voice or the like from the outside No noise is generated between the fluorescent tube and the intermediate holder even when the vibration is applied.

  According to the means (11) and (12), the two fluorescent tubes in the backlight are always pressed inside the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube, so that the sound or the like from the outside No noise is generated between the fluorescent tube and the intermediate holder even when the vibration is applied.

  According to the means (13) to (15), the fluorescent tube in the liquid crystal display device is always pressed in the outer direction of the liquid crystal display device in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube. No noise is generated between the fluorescent tube and the intermediate holder even if vibration such as sound is applied from the outside.

  According to the means (16) to (18), the fluorescent tube in the liquid crystal display device is always pressed in the inner direction of the liquid crystal display device in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube. No noise is generated between the fluorescent tube and the intermediate holder even if vibration such as sound is applied from the outside.

  According to the means (19) to (21), the fluorescent tube in the backlight is always pressed in the outer direction of the backlight in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube. Even if vibrations such as sound are applied, no noise is generated between the fluorescent tube and the intermediate holder.

  According to the means (22) to (24), the fluorescent tube in the backlight is always pressed in the inner direction of the backlight in the fluorescent tube holding portion of the intermediate holder that supports the fluorescent tube. Even if vibrations such as sound are applied, no noise is generated between the fluorescent tube and the intermediate holder.

  The detailed contents of the present invention will be disclosed according to the embodiments.

  FIG. 1 is a schematic view of a liquid crystal display device. A liquid crystal display panel 1 is accommodated in a frame-like front frame 2. The peripheral portion of the liquid crystal display panel 1 is covered with the front frame 2 so that only the effective screen portion is visible. A backlight 3 is installed behind the liquid crystal display panel 1. An image is formed by switching light from the backlight 3 by the liquid crystal panel 1. In order to efficiently extract light toward the liquid crystal display panel 1, the backlight 3 is composed of various parts.

  FIG. 2 is an exploded perspective view of the backlight portion. This backlight is a backlight for a large display device such as a TV, and is a so-called direct type backlight. The mold frame on which the liquid crystal panel is placed includes a long side mold frame 313 and a short side mold frame 312. This is to increase the material yield.

  The liquid crystal display panel 1 is placed on the mold frame. An IC driver and a flexible wiring board for driving the liquid crystal panel are installed around a liquid crystal display panel (not shown). The flexible wiring board is bent and installed backward in order to reduce the outer shape of the liquid crystal display device. The flexible wiring board receiver 313 formed on the mold frame receives the flexible wiring board.

  In the mold frame, three diffusion sheets 32, 33, and 34 are installed facing the back surface of the liquid crystal display panel 1. The roles of the diffusion sheets 32, 33, and 34 are to diffuse light from the light source and give uniform light to the liquid crystal display panel 1. The diffusion sheets 32, 33, and 34 generally have concavity and convexity on the surface, and thus have a light collecting effect. Because of this light condensing effect, three diffusion sheets are used instead of one. A diffusion sheet having a thickness of about 0.2 mm is used.

  A diffusion plate 35 is installed under the diffusion sheet 34. The role of the diffusion plate 35 is to make the light from the fluorescent tube 37 as a light source uniform and direct it toward the liquid crystal display panel 1. The thickness of the diffusion plate 35 is 1 mm. The diffusion plate 35 is installed on the side mold 36.

  Under the side mold 36, a plurality of fluorescent tubes 37 serving as light sources are installed. The amount of light from the light source 37 directly affects the brightness of the screen. In this embodiment, 16 fluorescent tubes are used. The fluorescent tube 37 is installed on the lower frame 39. On the other hand, a reflection sheet 38 is installed between the lower frame 39 and the fluorescent tube 37 in order to direct as much light as possible from the fluorescent tube toward the liquid crystal display panel 1 side.

  When the screen becomes larger, the fluorescent tube 37 becomes longer. On the other hand, since the luminous efficiency of the fluorescent tube 37 is higher when the tube diameter is smaller, the fluorescent tube 37 for the liquid crystal backlight is thin and long. In this embodiment, the length of the fluorescent tube is 790 mm, and the diameter of the fluorescent tube is 3 mm. In order to prevent the fluorescent tube 37 from moving or damaged by vibration or the like, an intermediate holder 40 formed of resin is installed. The intermediate holder 40 is attached to the lower frame 39 via the reflection sheet 38.

  The fluorescent tube 37 is driven by an inverter. The inverter is attached to an inverter board 41 installed on the back side of the lower frame 39. This inverter is protected by an inverter cover 42.

  FIG. 3 is a plan view in which the reflection sheet 38 and the intermediate holder 40 are attached to the lower frame 39. 4 is a cross-sectional view taken along the line AA in FIG. The reflection sheet 38 is installed in the lower frame 39 in the shape of a bag. A total of eight intermediate holders 40 are installed in two rows. One intermediate holder 40 holds the two fluorescent tubes 37.

  FIG. 5 shows a state in which the fluorescent tube 37 is attached to the lower frame 39. The fluorescent tube 37 is driven by an inverter. The white side of the terminal portion is on the high voltage side, and the black side of the terminal portion is on the low voltage side. As can be seen from this figure, one intermediate holder 40 holds two fluorescent tubes 37.

  FIG. 6 is a perspective view of the intermediate holder 40 as viewed from the front side. The intermediate holder 40 includes a base portion 401, a fluorescent tube holding portion 402, and a spacer portion 403. The fluorescent tube 37 is set in the fluorescent tube holding unit 402 and holds the fluorescent tube 37. As will be described later, the spacer portion 403 keeps the distance between the fluorescent tube 37 and the diffusion plate 35. FIG. 7 is a perspective view of the intermediate holder 40 as seen from the back side. The attachment portion 404 is for attaching the intermediate holder 40 to the lower frame 39. The intermediate holder 40 is made of polycarbonate.

  FIG. 8 shows a state where the intermediate holder 40 is attached to the lower frame 39 and holds the fluorescent tube 37. The intermediate holder 40 is attached to the lower frame 39 by a holding portion 404. The fluorescent tube holding unit 402 holds the fluorescent tube 37. The spacer portion 403 keeps the distance between the reflection sheet 38 and the diffusion plate 35 attached to the lower frame 39 or the distance between the fluorescent tube 37 and the diffusion plate 35 constant. The diffusion plate 35 is as thin as 1 mm, and when the display screen is enlarged, the diffusion plate 35 is bent and becomes the center of the screen, so the distance from the fluorescent tube 37 is reduced. Since the deflection of the diffuser plate 35 varies, it appears as variations in the luminance of the backlight. The spacer portion 403 of the intermediate holder 40 has a role of keeping the distance between the diffusion plate 35 and the fluorescent tube 37 and the like constant and suppressing variations in luminance.

  FIG. 9 is a schematic view showing a state in which one intermediate holder 40 holds two fluorescent tubes 37. FIG. 10 shows a part of the AA cross section of FIG. Details are omitted in FIGS. 9 and 10. FIG. 10 shows the relationship between the fluorescent tube 37 and the holding portion of the intermediate holder 40. The diameter φ2 of the fluorescent tube 37 is 3 mm, but the variation is about 0.1 mm. On the other hand, the variation in the inner diameter of the intermediate holder holding portion 402 is about 0.1 mm. Therefore, the fluorescent tube 37 may not be inserted into the intermediate holder holding part 402 unless the inner diameter φ1 of the intermediate holder holding part 402 is 3.2 mm. Therefore, the inner diameter of the intermediate holder holding part 402 needs to be 3.2 mm. That is, there is always an average gap of 0.2 mm between the fluorescent tube 37 and the inside of the intermediate holder holding portion 402. FIG. 11 shows an enlarged plan view of the state in which the fluorescent tube 37 is installed in the intermediate holder holding portion 402 of FIG. As shown in FIG. 11, there is always a gap g between the inner side of the intermediate holder holding portion 402 and the fluorescent tube 37. If this interval g is zero, there is a variation in the diameter of the fluorescent tube 37 or the inner diameter of the intermediate holder holding portion 402, so that the fluorescent tube 37 may not be inserted into the intermediate holder holding portion 402 at a constant rate.

  In this state, when a sound wave is applied from a speaker or the like in the display device, the fluorescent tube 37 vibrates as indicated by an arrow vb shown in FIG. As a result, the fluorescent tube 37 and the intermediate holder holding part 402 collide with each other at a constant period, and noise is generated. Since the fluorescent tube 37 used in the backlight is long and thin, vibration due to sound waves is easily generated.

  The same problem occurs when a high frequency power source is present in the liquid crystal display device, and the fluorescent tube vibrates due to resonance between the electromagnetic wave caused by the high frequency and the fluorescent tube. Since the fluorescent tube 37 of the backlight uses a high frequency power source such as an inverter, such a problem is likely to occur. Such vibrations due to high frequencies also occur when no sound is being output, so the problem is likely to become obvious.

  FIG. 12 is a conceptual diagram showing the first embodiment of the present invention. FIG. 12 shows only the intermediate holder 40 and the two fluorescent tubes 37 taken out from the backlight. As conceptually shown in FIG. 12, the two holders in the intermediate holder holding unit 402 have a larger distance than the interval between the two fluorescent tubes 37 near the lower frame 39 where the socket 371 of the fluorescent tube 37 is attached. The interval between the fluorescent tubes 37 is larger.

  By adopting such a relationship, the relationship between the fluorescent tube 37 and the intermediate holder holding portion 402 inside the intermediate holder holding portion 402 is as shown in FIG. That is, since the fluorescent tube 37 is pressed against the intermediate holder holding portion 402 by a force such as F shown in FIG. 13, the fluorescent tube 37 does not vibrate even when an impact such as a sound wave is applied. There is no noise. The important point here is how much the interval between the two fluorescent tubes is increased at the intermediate holder portion.

  First, it is necessary to consider the component tolerance of the fluorescent tube 37 and the intermediate holder 40. The variation in the outer shape of the fluorescent tube 37 is ± 0.1 mm. The variation of the inner diameter of the intermediate holder holding part 402 is also ± 0.1 mm. In order for the fluorescent tube 37 to be able to be inserted into the intermediate holder holding portion 402 even if the parts vary, the inner diameter of the intermediate holder holding portion 402 must be 0.2 mm larger than the outer shape of the fluorescent tube 37. Since one intermediate holder has two holding portions, in order to keep the two holding portions 402 in the state shown in FIG. 13, it is necessary to double at least 0.2 mm, at least 0.4 mm. . That is, in order to always keep the relationship between the fluorescent tube 37 and the intermediate holder holding portion 402 as shown in FIG. 13, the distance between the two fluorescent tubes 37 in the socket portion 371 is larger than the interval between the two holding portions 402 of the intermediate holder 40. However, 0.4mm must be reduced in advance. Since this includes the case where the stress becomes zero, a difference of 0.4 mm or more is necessary in order to generate the stress in all cases.

  On the other hand, it is necessary to avoid the relationship between the fluorescent tube 37 and the intermediate holder holding part 402 as shown in FIG. Here, the use temperature range has the greatest influence among the use environments. In general, a display device is required to guarantee a use environment of about 0 ° C. to 40 ° C. Therefore, even when the environment becomes the most disadvantageous, the relationship between the fluorescent tube 37 and the intermediate holder holding portion 402 only needs to hold the relationship shown in FIG.

  The backlight is assembled in an atmosphere of 25 ° C. Assume that the stress F is zero in the state shown in FIG. 13 at this temperature. When the temperature of the outside air at which the display device operates changes, a difference in thermal expansion between the lower frame 39 to which the fluorescent tube 37 is attached and the intermediate holder 40 that holds the fluorescent tube 37 becomes a problem. When the operating temperature is guaranteed from 0 ° C. to 40 ° C., the difference from the assembly temperature of 25 ° C. is maximum at 0 ° C. It is assumed that the temperature of the backlight decreases as the temperature of the outside air decreases. In this case, the difference in thermal expansion between the lower frame and the intermediate holder with respect to the inner space df of the fluorescent tube 37 shown in FIG. 13 may be evaluated. The value of df is 23 mm in this embodiment.

The lower frame 39 is made of iron and has a thermal expansion coefficient of 1.2 × 10 ⁻⁵ / ° C. On the other hand, the intermediate holder 40 is made of polycarbonate and has a thermal expansion coefficient of 7 × 10 ⁻⁵ / ° C. Therefore, when the temperature changes from 25 ° C. to 0 ° C., the difference caused by the difference in thermal expansion coefficient with respect to the interval df is 25 × 23 mm × (7−1.2) × 10 ⁻⁵ / ° C. = 0. 033 mm. Therefore, in order to assemble the backlight at 25 ° C. and prevent a gap between the fluorescent tube 37 and the intermediate holder holding portion 402 until 0 ° C., the distance between the two fluorescent tubes 37 in the socket portion 371 is 0.43 mm must be made smaller than the distance between the two holding portions 402 in advance. Since this includes the case where the stress is zero, a difference of 0.43 mm or more is necessary to generate the stress in all cases.

  The interval between the socket portions 371 of the fluorescent tube 37 can be set relatively accurately. Moreover, since the intermediate holder 40 is also formed of a resin mold, it can be set relatively accurately. Therefore, according to the present embodiment, the fluorescent tube 37 is surely pressed to the inner side of the intermediate holder holding portion 402 with a predetermined force, so that the fluorescent tube 37 and the intermediate holder holding portion 402 The generation of noise between the two can be avoided.

  14 and 15 show a second embodiment of the present invention. The difference from the first embodiment is that the interval between the socket portions 371 of the two fluorescent tubes 37 is larger than the interval between the two holding portions 402 of the intermediate holder 40. Variations in the diameter of the fluorescent tube 37, variations in the inner diameter of the intermediate holder holding portion 402, and the like are the same as those in the first embodiment. Therefore, in the second embodiment, contrary to the first embodiment, the distance between the socket portions 371 of the fluorescent tube 37 needs to be 0.4 mm or more larger than the distance between the two holding portions 402 of the intermediate holder 40.

  Also in Example 2, when the backlight is assembled at 25 ° C. and the operating temperature is guaranteed from 0 ° C. to 40 ° C., it is necessary to evaluate the thermal expansion coefficients of the lower frame 39 and the intermediate holder 40. In this case as well, the numerical values are the same except that the problematic expansion direction is opposite to that in the first embodiment. Therefore, in Example 2, when the operating temperature range is taken into consideration, the interval between the socket portions 371 of the fluorescent tube 37 may be 0.43 mm or more larger than the interval between the two holding portions 402 of the intermediate holder 40.

  16 and 17 show a third embodiment of the present invention. The difference between the present embodiment and the first and second embodiments is that the interval between the two holding portions 402 of the intermediate holder 40 and the interval between the socket portions 371 of the two fluorescent tubes 37 are not shifted, but the intermediate holder holding portion 402. Is shifted from the position of the socket portion 371 of the fluorescent tube 37 to press the fluorescent tube 37 in one direction of the intermediate holder holding portion 402.

  The value of dd shown in FIG. 16 for keeping the fluorescent tube 37 in contact with one of the intermediate holder holding portions 402 is the variation in the diameter of the fluorescent tube 37 and the intermediate holder holding portion as described in the first embodiment. It is necessary to decide in consideration of the variation in the inner diameter of 402. In the present embodiment, the effect of pressing the fluorescent tube 37 against the intermediate holder holding portion 402 by increasing or narrowing the distance between the two fluorescent tubes 37 by the intermediate holder holding portion 402 is not intended. Therefore, the difference between the position of the fluorescent tube 37 at the socket portion 371 and the position at the intermediate holder holding portion 402 may be determined in consideration of the tolerance between the diameter of the fluorescent tube 37 and the inner diameter of the intermediate holder holding portion 402. In other words, if the tolerances of the inner diameters of the fluorescent tube 37 and the intermediate holder holding portion 402 are ± 0.1 mm, respectively, it is only necessary to shift by 0.2 mm.

  In this embodiment, in addition to this, a distance y1 from the center of the lower frame 39 to the center of the intermediate holder 40 shown in FIG. 16 and a distance from the center of the lower frame 39 to the centers of the socket portions 371 of the two fluorescent tubes 37 are shown. It is necessary to consider the variation in the distance y2. Then, it is necessary to determine dd shown in FIG. 16 including variations between y1 and y2. For example, if the tolerances of y1 and y2 are each 0.2 mm, the total tolerance of the fluorescent tube, the intermediate holder holding part, and y1 and y2 is 0.6 mm. Therefore, the design value of the difference dd between y1 and y2 needs to be 0.6 mm. By setting in this way, it is possible to always press the two fluorescent tubes 37 in one direction of the intermediate holder holding portion 402 as shown in FIG.

When the use environment temperature is taken into consideration, in the third embodiment, a difference occurs between the two fluorescent tubes 37. Also in this case, it is assumed that the backlight is assembled at 25 ° C., the operating temperature range is guaranteed from 0 ° C. to 40 ° C., and the external temperature becomes 0 ° C. In this case, the difference in thermal expansion is in the direction in which the force with which the outer fluorescent tube 37 shown in FIG. On the other hand, the inner fluorescent tube 37 is in a direction in which the force pressed against the intermediate holder holding portion 402 increases. Therefore, it is only necessary to consider the outer fluorescent tube 37 that the fluorescent tube 37 is always pressed against the intermediate holder holding portion 402 within the operation guarantee range. The influence of the difference in thermal expansion in this case may be considered for df / 2 = 11.5 mm, which is half of that in the first embodiment. Then, the influence of the difference in thermal expansion is 25 × 11.5 mm × (7−1.2) × 10 ^{−5 /} ° C. = 0.17 mm. Therefore, in order to always press the fluorescent tube 37 against the intermediate holder holding part 402 in consideration of the operating temperature range, dd shown in FIG. 16 may be 0.617 or more.

  18 and 19 show a fourth embodiment of the present invention. In this embodiment, as in the third embodiment, the fluorescent tube 37 is pressed in one direction by shifting the position of the intermediate holder holding portion 402 from the socket portion 371 of the fluorescent tube 37. The direction in which the tube 37 is pressed against the intermediate holder holding portion 402 is reverse.

  That is, as shown in FIG. 18, the distance y1 from the center of the lower frame to the center of the intermediate holder is smaller than the distance y2 from the center of the lower frame to the centers of the socket portions 371 of the two fluorescent tubes 37. As shown in FIG. 19, stress corresponding to the difference dd between y1 and y2 causes the fluorescent tube 37 to be pressed against the intermediate holder holding portion 402. The amount of dd in this case can also be determined in the same manner as in the third embodiment, and dd is 0.6 mm in this embodiment.

  The case where the temperature of the operating environment changes can be considered as in the third embodiment. When the operating environment is changed from 0 ° C. to 25 ° C. at the time of assembling the backlight, it is the inner fluorescent tube 37 in FIG. In this case as well, the fluorescent tube 37 can always be pressed against the intermediate holder holding portion 402 by considering the same as in the third embodiment and setting the value of dd in FIG. 18 to 0.617 mm or more.

  The above embodiment is a case where the intermediate holder 40 holds the two fluorescent tubes 37. The present invention need not limit the number of fluorescent tubes 37 supported by the intermediate holder 40 to two. In this case, the situation differs depending on whether the intermediate holder 40 holds only one fluorescent tube 37, holds an even number of fluorescent tubes 37, or holds three or more odd numbers.

  FIG. 20 shows a case where the intermediate holder 40 holds one fluorescent tube 37. In this case, the difference of y1-y2 is the sum of the tolerance of the fluorescent tube 37, the tolerance of the inner diameter of the intermediate holder holding portion 402, the tolerance of y1, and the tolerance of y2. For example, when the tolerance of the fluorescent tube 37 and the inner diameter of the intermediate holder holding part 402 are ± 0.1 mm, and the tolerances of y1 and y2 are ± 0.2 mm, respectively, the difference between y1 and y2 is the sum of the tolerances. It is necessary to be 0.6 mm or more.

  FIG. 21 shows a case where the intermediate holder 40 has four holding portions 4021 to 4024. Thus, when the holding part exists in the intermediate holder 40 in an even number, a method like Example 1 or Example 2 is applicable. In this case as well, basically, the fluorescent tube 37 has a diameter tolerance twice that of the sum of the inner diameter tolerances of the intermediate holder holding portion 402, and the distance between the fluorescent tubes in the socket portion 371 and the intermediate holder holding of the fluorescent tube. What is necessary is just to give a difference in the space | interval of the part 402. FIG. That is, when the tolerance of the fluorescent tube diameter is ± 0.1 mm and the tolerance of the inner diameter of the intermediate holder holding portion 402 is ± 0.1 mm, f1-d1 in FIG. What is necessary is just to be 4 mm or more.

On the other hand, when the influence of the operating environment temperature is taken into consideration, the influence of the difference in thermal expansion becomes larger as the number of holding parts 402 of the intermediate holder becomes four and the interval between the holding parts becomes larger. Also in this case, it is assumed that the temperature at the time of assembling the backlight is 25 ° C., and 0 ° C. is the largest temperature change. At that time, for example, in FIG. 21, when the interval between the fluorescent tube 37 held by the intermediate holder holding portion 4021 and the fluorescent tube 37 held by the intermediate holder holding portion 4022 is 69 mm, the fluorescent tube is caused by thermal expansion. The amount by which the interval between the intermediate holder holding portions 402 is larger than 37 is 25 × 46 mm × (7−1.2) × 10 ^{−5 /} ° C. = 0.1 mm. Therefore, the difference between d1 and f1 in FIG. 21 needs to be 0.5 mm or more.

  For the other fluorescent tubes 37, for example, the fluorescent tubes 37 held by the intermediate holder holding portion 4023 or 4024, the difference between d2 and f2 is preferably 0.5 mm. Alternatively, the difference between d2 and f2 may be reduced in proportion to the difference between d1 and d2. That is, in FIG. 21, since d2 is 1/3 of d1, the influence of thermal expansion can be expected to be reduced accordingly. Therefore, the influence of the difference in thermal expansion on the difference between d2 and f2 can be about 0.03 mm to 0.1 mm.

  When the number of holding portions 402 of the intermediate holder 40 is an odd number of 3 or more, as in the case of the first or second embodiment, only the difference between the interval of the socket portion 371 of the fluorescent tube 37 and the interval of the intermediate holder holding portion 402 is used. It is difficult to press the tube 37 against the intermediate holder holding portion 402. This is because the central fluorescent tube 37 cannot be pressed against the intermediate holder holding portion 402 only by this method. In this case, it is necessary to use the method of Example 1 or Example 2 together with the method of Example 3 or Example 4. Alternatively, only the method of Example 3 or Example 4 may be used.

It is a general-view figure of a liquid crystal display device. It is a disassembled perspective view of a backlight. It is a top view of the lower frame in which a fluorescent tube is accommodated. It is AA sectional drawing of FIG. It is a top view of the state where the fluorescent tube was accommodated in the lower frame. It is an upper perspective view of an intermediate holder. It is a downward perspective view of an intermediate holder. It is sectional drawing of the condition where the intermediate holder was attached to the lower frame. It is a top view which shows the relationship between a fluorescent tube and an intermediate holder. It is a conceptual sectional view of the situation where a fluorescent tube is supported by an intermediate holder. It is an enlarged plan view near an intermediate holder. 1 is a conceptual plan view of Example 1. FIG. 3 is an enlarged plan view of the vicinity of an intermediate holder according to Embodiment 1. FIG. 3 is a conceptual plan view of Example 2. FIG. 6 is an enlarged plan view of the vicinity of an intermediate holder according to Embodiment 2. FIG. 6 is a conceptual plan view of Example 3. FIG. 6 is an enlarged plan view of the vicinity of an intermediate holder according to Embodiment 3. FIG. 10 is a conceptual plan view of Example 4. FIG. 6 is an enlarged plan view of the vicinity of an intermediate holder in Example 4. FIG. FIG. 10 is a conceptual diagram showing one form of Example 5. It is a conceptual diagram which shows the other form of Example 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel, 2 ... Front frame, 3 ... Back light, 32, 33, 34 ... Diffusion sheet, 35 ... Diffusion plate, 36 ... Side mold, 37 ... Fluorescent tube, 8 ... Reflection sheet, 39 ... Lower frame, DESCRIPTION OF SYMBOLS 40 ... Intermediate holder, 41 ... Inverter board, 42 ... Inverter cover, 311 ... Mold frame long side, 312 ... Mold frame short side, 312 ... Flexible wiring board receptacle, 371 ... Fluorescent tube socket, 402 ... Intermediate holder holding part, 403 ... spacer part.

Claims (12)

A liquid crystal display device having a liquid crystal display panel and a backlight including at least two fluorescent tubes,
Both ends of the fluorescent tube are supported on the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube is supported by an intermediate holder capable of supporting two fluorescent tubes,
The intermediate holder has a holding portion that supports the two fluorescent tubes,
The fluorescent tube is pressed against the holding portion of the intermediate holder, and the distance between the two fluorescent tubes supported by the intermediate holder is smaller than the distance at the connection support portion with the frame. A liquid crystal display device characterized by being larger.   2. The liquid crystal display device according to claim 1, wherein a distance between the two fluorescent tubes is 0.4 mm or more greater than a distance between the intermediate holder and an attachment portion with the frame.   The liquid crystal display device according to claim 1, wherein the material of the intermediate holder has a larger coefficient of thermal expansion than the material of the frame.   When the tolerance of the diameter of the fluorescent tube is ± a and the tolerance of the inner diameter of the portion of the intermediate holder that accommodates the fluorescent tube is ± b, the distance between the two fluorescent tubes is the connection support with the frame The liquid crystal display device according to claim 1, wherein a distance in the intermediate holder is 2 × (a + b) or more larger than a distance in the portion. A liquid crystal display device having a liquid crystal display panel and a backlight including at least two fluorescent tubes,
Both ends of the fluorescent tube are supported on the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube is supported by an intermediate holder capable of supporting two fluorescent tubes,
The intermediate holder has a holding portion that supports the two fluorescent tubes,
The fluorescent tube is pressed against the holding portion of the intermediate holder, and the distance between the two fluorescent tubes supported by the intermediate holder is smaller than the distance at the connection support portion with the frame. A liquid crystal display device characterized by being smaller.   6. The liquid crystal display device according to claim 5, wherein a distance between the two fluorescent tubes is 0.4 mm or more smaller than a distance between the intermediate holder and an attachment portion with the frame.   The liquid crystal display device according to claim 5, wherein the material of the intermediate holder has a larger coefficient of thermal expansion than the material of the frame.   When the tolerance of the diameter of the fluorescent tube is ± a and the tolerance of the inner diameter of the portion of the intermediate holder that accommodates the fluorescent tube is ± b, the distance between the two fluorescent tubes is the connection support with the frame The liquid crystal display device according to claim 5, wherein the distance in the intermediate holder is 2 × (a + b) or more smaller than the distance in the portion. A backlight for a liquid crystal display device including at least two fluorescent tubes,
Both ends of the fluorescent tube are supported on the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube is supported by an intermediate holder capable of supporting two fluorescent tubes,
The intermediate holder has a holding portion that supports the two fluorescent tubes,
The fluorescent tube is pressed against the holding portion of the intermediate holder, and the distance between the two fluorescent tubes supported by the intermediate holder is larger than the distance at the connection support portion with the frame. Backlight characterized by being larger.   10. The backlight according to claim 9, wherein the distance between the two fluorescent tubes is greater by 0.4 mm or more than the distance between the intermediate holder and the attachment portion with the frame. A backlight for a liquid crystal display device including at least two fluorescent tubes,
Both ends of the fluorescent tube are supported on the frame by connection support portions with the frame, and an intermediate portion of the fluorescent tube is supported by an intermediate holder capable of supporting two fluorescent tubes,
The intermediate holder has a holding portion that supports the two fluorescent tubes,
The fluorescent tube is pressed against the holding portion of the intermediate holder, and the distance between the two fluorescent tubes supported by the intermediate holder is larger than the distance at the connection support portion with the frame. Backlight characterized by being smaller.   12. The backlight according to claim 11, wherein the distance between the two fluorescent tubes is smaller by 0.4 mm or more than the distance at the attachment portion with the frame at the intermediate holder.

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