JP2010192299A - Backlight device, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device in which the spacing between a diffusion plate and a light source is maintained to be constant, while luminance unevenness is prevented. <P>SOLUTION: The backlight device 23 has a light source 3 arranged in a case 25 and a diffusion plate 2 arranged in front of the light source 3. The device has a diffusion plate bending prevention member 1 of which one end is engaged with a through hole 27 provided in the diffusion plate 2 and prevents bending of the diffusion plate frontwards, and in which the transmittance of at least a part is adjusted so that luminance distribution on the diffusion plate 2 may be nearly uniform. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight device installed in a liquid crystal display device, and more particularly to a device that illuminates a liquid crystal panel from behind.

  When the liquid crystal display device is relatively small, the diffusion plate does not warp to the liquid crystal panel side due to its own weight, and the diffusion plate is fixed or semi-fixed to the edge of the reflection plate or chassis. As long as the liquid crystal panel is attached and held by the spacer, no uneven brightness occurs in the liquid crystal panel.

  In recent liquid crystal display devices, there has been a demand for an increase in the size of the display screen as the use of video display means expands. As the size of liquid crystal display devices increases, the diffusion plate inevitably increases in size, and the increased diffusion plate tends to bend due to its own weight due to its flexibility, and the amount of deflection tends to increase. I came.

  The phenomenon that the diffuser plate and the optical sheet such as a polarizing reflection film attached to the diffuser plate tend to bend toward the light source side is restricted by the intervention of a spacer (a spacer provided between the bottom plate of the chassis and the diffuser plate). However, the phenomenon that the diffusion plate or the optical sheet tends to bend toward the liquid crystal panel cannot be regulated by the spacer. Therefore, the distance between the liquid crystal panel and the diffusing plate may be uneven due to the bending, resulting in uneven brightness of the liquid crystal panel. When the bending becomes large, the optical sheet attached to the diffusing plate contacts the liquid crystal panel. As a result, the liquid crystal panel may be damaged.

  With respect to this problem, the conventional technology (for example, see Patent Document 1) is intended to prevent the bending of the diffusion plate toward the liquid crystal panel, and is intended to prevent the diffusion plate. By providing a through hole and using a columnar fixing member, the above-described bending is prevented, luminance unevenness in the liquid crystal panel is prevented, and deterioration in image quality is prevented.

Japanese Patent No. 4009263

  In the thing of patent document 1, in order to prevent bending of a diffuser plate etc., the permeation | transmission hole is opened in the diffuser plate which is originally translucent and has a diffusion effect, and the fixing member for preventing bending is a diffuser plate. It is said that a transparent material is used so that it will not be affected by the incident light.

  However, if the fixing members are all made of a transparent material, the light generated by the light source and transmitted through the fixing members is not diffused by the diffusion plate, and light leakage to the surface of the backlight device occurs. Of the light emitted from the light source, the light that has passed through that portion (the portion of the fixing member that is engaged with the diffuser) has passed through the optical sheet or liquid crystal panel, and thus has a bright portion (high brightness). Part) appears on the liquid crystal panel, and there is a problem that luminance unevenness is visually recognized on the liquid crystal display device.

  Thus, it has been difficult to achieve both luminance uniformity on the diffusion plate while maintaining the function of suppressing the deflection of the diffusion plate toward the liquid crystal panel.

  The present invention has been made in view of the above-described problems. In a liquid crystal display device and a backlight device used in the liquid crystal display device, the backlight is maintained while maintaining a constant distance between the diffusion plate and the light source. An object of the present invention is to provide a device capable of reducing the occurrence of uneven brightness in the apparatus.

  A first aspect of the present invention is a housing having an open surface on one side, a light source disposed in the housing, a light source disposed on the open surface of the housing, and diffusing light emitted from the light source. A diffusing plate that transmits the light, and the diffusing plate is prevented from bending in the light transmitting direction of the diffusing plate, and at least a part of the transmittance so that the luminance distribution of the light transmitted through the diffusing plate is substantially uniform. It is a backlight apparatus which has a bending prevention member in which is adjusted.

  The second invention is the backlight device according to the first invention, wherein one end of the deflection preventing member is engaged with a through hole formed in the diffusion plate.

  According to a third aspect of the invention, the back of the first aspect or the second aspect, wherein the one end portion of the deflection preventing member is made of a material having a transmittance equal to or lower than the transmittance of the diffusion plate. Light device.

  A fourth invention is the backlight device according to any one of the first to third inventions, an optical sheet disposed at a position where the light emitted from the light source is transmitted through the diffusion plate, and the light. Is a liquid crystal display device having a liquid crystal panel disposed at a position where the light passes through the optical sheet.

  According to the present invention, in the liquid crystal display device and the backlight device used in the liquid crystal display device, the occurrence of uneven brightness in the backlight device is reduced while keeping the distance between the diffusion plate and the light source constant. There is an effect that can be.

It is sectional drawing which shows schematic structure of the liquid crystal display device 21 which concerns on embodiment of this invention. It is II arrow directional view in FIG. It is an enlarged view of the III section in FIG. It is a figure which shows the modification of the fixing member. It is a figure which shows the modification of the fixing member. It is a figure which shows the modification of the installation form of the spacer 8 and the lamp holder 4. FIG.

  In the following description, a liquid crystal backlight device used as a linear light source such as a direct type CCFL (Cold Cathode Fluorescent Lamp; lamp) 3 is exemplified, but the same applies to a liquid crystal backlight device using a point light source such as an LED. Can think.

  The liquid crystal display device 21 includes a backlight device 23, an optical sheet (an optical sheet composed of a polarizing reflection film) 6 disposed on the front surface of the diffusion plate 2 of the backlight device 23, and a front surface of the optical sheet 6. The liquid crystal panel 7 is provided. Then, the light emitted from the backlight device 23 illuminates the liquid crystal display device 21 through the diffusion plate 2 and the optical sheet 6. In addition, the liquid crystal display device 21 is driven by a drive device or the like (not shown) that drives the liquid crystal panel 7, modulates the light emitted from the backlight device 23, and adds gradations. The video is displayed. 1 is the front side of the liquid crystal display device 21, and the lower side of FIG. 1 is the rear side of the liquid crystal display device 21.

  The backlight device 23 includes a rectangular bowl-shaped casing (bottomed case) 25, and a cylindrical CCFL 3 is disposed in the casing 25 on the bottom side of the casing 25. The CCFL 3 is installed on the reflecting member 5 (housing 25) via the lamp holder 4. A plurality of CCFLs 3 are arranged in the vertical or horizontal direction so as to face the entire surface (bottom surface) of the reflecting member 5. The distance between each CCFL 3 and the bottom surface of the reflecting member 5 is a constant value that is equal to each other.

  A rectangular flat plate-shaped diffusion plate 2 is disposed in front of CCFL 3 (on the side opposite to the bottom of housing 25 with CCFL 3 in between; the opening side of housing 25). That is, the diffusing plate 2 is disposed on the open surface of the housing 25 having one open surface. The diffusion plate 2 is made of a material such as acrylic (PMMA), polycarbonate (PC), or polystyrene (PS) containing a diffusion material, and has a thickness of about 2 mm and is milky white.

  A reflector (reflecting member) 5 is disposed behind the CCFL 3. 1 is a diagram showing a part of the liquid crystal display device 21. In FIG. 1, although the flat bottom plate of the casing 25 and the reflection member 5 is displayed, the casing 25 and the reflection plate are displayed. The side plate of the member 5 is not displayed. The diffusion plate 2, the optical sheet 6, and the liquid crystal panel 7 are provided in the casing 25 so that the thickness direction thereof coincides with the front-rear direction of the backlight device 23 and closes the opening of the casing 25. ing.

  The backlight device 23 is provided with a diffusion plate deflection preventing member (fixing member) 1 and a spacer 8. The fixing member 1 is formed, for example, in a rod shape, and one end portion in the longitudinal direction (the upper end portion in FIGS. 1 and 3) engages with a through hole (through hole) 27 formed in the diffusion plate 2. Yes. A portion on the other end side in the longitudinal direction of the fixing member 1 extends from the diffusion plate 2 to the rear side (the lower side in FIGS. 1 and 3). And the other end part of the fixing member 1 in the longitudinal direction is engaged with the housing 25, the diffusion plate 2 is pulled to the rear side, and the diffusion plate 2 is bent forward (the transmission direction of light emitted from the CCFL 34). Is preventing.

  In addition, the spacer 8 formed in a rod shape (for example, a tall conical shape) has a bottom surface located on the bottom side of the housing 25, the top is in contact with the diffusion plate 2, and the diffusion plate 2 is rearward ( CCFL3 side) is prevented from being bent.

  Further, the transmittance of at least a part of the fixing member 1 (the transmittance of visible light emitted from the CCFL 3) is adjusted so that the luminance distribution on the diffusion plate 2 by the CCFL 3 becomes substantially uniform.

  Explaining with a specific example, a portion (joining portion; engaging portion) 9 of the fixing member 1 engaged with the through hole 27 of the diffusion plate 2 is made of the same material as the diffusion plate 2.

  Further, as shown in FIG. 3, the fixing member 1 is connected to a spot facing portion 31 of the diffusion plate 2 in which a cylindrical through hole 29 is formed in the diffusion plate 2 and a frusto-conical spot facing is performed. ing.

  The fixing member 1 includes a joint portion (connection portion) 9 engaged with a 90 ° counterbore portion 31, a fixing portion 11 fixed to the reflecting member 5, and a connecting portion connecting the joint portion 9 and the fixing portion 11. 10 and is formed in a cylindrical body shape (may be a shape such as a square body shape). That is, for example, it is formed in the shape of a countersunk screw having the joint 9 as a head.

  The joint portion 9 of the fixing member 1 has a tapered shape in order to strengthen locking with the diffusion plate 2 in consideration of the thickness of the diffusion plate 2, and has a wider cross-sectional area. It has a structure that can be locked.

  The material constituting the joint 9 of the fixing member 1 is such that the light emitted by the CCFL 3 and the light emitted by the CCFL 3 and reflected by the reflecting member 5 and incident on the diffusion plate 2 is not affected by the presence of the fixing member 1. In addition, it is adjusted so as to have the same transmittance as that of the diffusion plate 2 (so that the luminance unevenness on the diffusion plate 2 does not occur due to the presence of the fixing member 1).

  For example, when the transmittance of the diffusing plate 2 is 50%, the luminance unevenness on the diffusing plate 2 can be suppressed by setting the transmittance of the joint 9 to about 50%. At this time, it is desirable that an optical coupling agent such as silicon grease is applied to the diffusion plate 2 and the joining portion 9 so that the diffusion plate 2 and the joining portion 9 are optically continuous. Furthermore, the transmittance may be adjusted by making the transmittance of the junction 9 (all of the junction 9 or a part of the junction 9) lower than the transmittance of the diffusion plate 2.

  The connecting portion 10 and the fixing portion 11 of the fixing member 1 are preferably formed of transparent members so that light incident on the diffusion plate 2 from the CCFL 3 and the reflection member 5 is not affected. The fixing member 1 can be manufactured as one fixing member (as an integral fixing member) by injection molding of two colors or the like.

  Further, as shown in FIG. 3, in order to fix the fixing member 1 to the reflecting member 5, the tip of the fixing portion 11 is inserted into the screw hole 12 formed by tapping the reflecting member 5 as shown in FIG. The male screw is screwed into the.

  Here, the backlight device 23 will be further described.

  The spacer 8 and the lamp holder 4 of the backlight device 23 are integrally formed by molding, for example. More specifically, the spacer 8 and the lamp holder 4 are integrated with each other through a rectangular flat plate-shaped substrate portion 33. The spacer 8 is erected from one surface in the thickness direction of the substrate portion 33 at one end portion in the longitudinal direction of the substrate portion 33. The lamp holder 4 is provided on the other end portion in the longitudinal direction of the substrate portion 33 on one surface in the thickness direction of the substrate portion 33. Two umbrella-shaped locking portions 35 are provided on the other surface in the thickness direction of the substrate portion 33, and these locking portions 35 are provided in the reflective member 5 and the housing 25. The spacer 8, the lamp holder 4, and the (substrate portion 33) are integrally installed on the reflecting member 5 and the housing 25 by engaging with the holes.

  Moreover, in FIG.1 and FIG.3, although the position of the fixing member 1 and the position of the spacer 8 have shifted | deviated in the left-right direction, this was drawn shifting for convenience of explanation, As understood from FIG. 2, the position of the fixing member 1 and the position of the spacer 8 coincide with each other in the left-right direction of FIG. 1 or 3 (the direction in which the CCFLs 3 are arranged at a predetermined interval). ing. As illustrated in FIGS. 1 and 3, the position of the fixing member 1 and the position of the spacer 8 may be shifted in the left-right direction in these drawings.

  Further, as understood from FIG. 2, the fixing member 1 and the spacer 8 are provided at the center of the interval between the two CCFLs 3 in the direction in which the CCFLs 3 are arranged at a predetermined interval (the left-right direction in FIG. 2). It has been. Furthermore, in the longitudinal direction of CCFL 3 (up and down direction in FIG. 2), the fixing member 1 is disposed between the spacers 8 provided with a predetermined interval. Note that, as indicated by a two-dot chain line in FIG. 2, the fixing member 1 may be provided in the vicinity of the spacer 8.

  According to the backlight device 23, one end portion of the fixing member 1 is engaged with the through hole 27 formed in the diffusion plate 2 to prevent the diffusion plate 2 from being bent forward, and the diffusion plate Since the transmittance of a part of the fixing member 1 is adjusted so that the luminance distribution on 2 is substantially uniform, the distance between the diffusion plate 2 and the CCFL 3 is kept constant while the backlight device 23 The occurrence of uneven brightness can be reduced.

  In other words, by using the fixing member 1, the diffusion plate 2 that is large and thin, and whose bending tends to expand is prevented from bending toward the side opposite to the CCFL 3 side. Since the interval can be maintained at a constant value, uneven brightness of light emitted from the diffusion plate 2 can be eliminated. When the backlight device 23 is used for the liquid crystal display device 21, the bent diffusion plate 2 is bent. This prevents the liquid crystal panel 7 from being damaged by touching the liquid crystal panel 7.

  Further, according to the backlight device 23, the fixing member 1 has a two-color configuration and light transmittance and the like are adjusted (for example, the joining portion 9 is made of a translucent material, and other portions are made transparent). Therefore, the uniformity of luminance on the diffusion plate 2 can be ensured. That is, a part of the light emitted from the CCFL 3 passes through the space in the casing 25 and passes through the diffusion plate 2 (the portion of the diffusion plate 2 not engaged with the fixing member 1) to the front side of the diffusion plate 2. Further, another part of the light emitted from the CCFL 3 passes through the transparent connecting portion 10 of the fixing member 1, passes through the joint portion 9 made of a translucent material, and passes through the bonding plate 9. Since it comes out to the front side, the intensity of light is appropriately reduced when passing through the joint 9. And the situation where the brightness | luminance of the junction part 9 of the fixing member 1 becomes high compared with the brightness | luminance of the other site | part of the diffusion plate 2 can be avoided, and the time the brightness | luminance unevenness generate | occur | produces in the backlight apparatus 23 is reduced. Can do.

  Moreover, the backlight device 23 illustrated in FIGS. 1 to 3 has a configuration in which a difference in transmittance between a part of the fixing member 1 and the diffusion plate 2 is eliminated, and the configuration of the fixing member 1 is one of the features. is there. That is, generally speaking, in order to make the fixing member 1 and the diffusion plate 2 an integral structure, a configuration in which a through hole is provided in the diffusion plate 2 and the fixing member 1 is engaged or screwed is considered. In this configuration, the uniformity of the light diffusion effect is lost due to the presence of the opening (through hole) of the diffusion plate 2. Therefore, in the backlight device 23, in addition to eliminating the bending of the diffusion plate 2 using the fixing member 1, the engaging portion 9 that is a part of the fixing member 1 is made to be a transmission material of the diffusion plate 2 using a semitransparent material, for example. Therefore, the light emitted from the CCFL 3 always passes through the diffusion plate 2, the fixing member 1, and the joint 9, and the light emitted from the diffusion plate 2 to the liquid crystal panel 7 is uniform. Thus, it is possible to keep the brightness unevenness in the diffusing plate 2 from occurring.

  As described above, according to the backlight device 23, the fixing member 1 combined with the diffusion plate 2 and the transmittance is fixed to the reflecting member 5 (housing 25) over a plurality of locations, and so on. By preventing the diffusion plate 2 from being bent on the side opposite to the arrangement side (front side), the luminance unevenness generated in the liquid crystal display device 21 can be reduced, and the diffusion plate 2 is provided on the liquid crystal panel 7. It is possible to reduce the damage to the liquid crystal panel 7 due to contact with the liquid crystal.

  The material used for the fixing member 1 and the spacer 8 is not limited in any way, but an external force (vibration) is applied to the backlight device 23 by using a material having a certain degree of elasticity such as a resin material. In addition, even when a drop impact is applied, the reliability improvement effect of preventing structural destruction of the fixing member 1 is also achieved.

  In addition, you may change the form of the fixing member 1 suitably.

  For example, as shown in FIG. 4, even if the shape of the fixing member is changed, the same effect as described above can be obtained.

  The fixing member 1b shown in FIG. 4 includes a disk-shaped joint portion 9b engaged with a cylindrical counterbore portion 37 formed on the diffusion plate 2, and a fixing portion fixed to the reflecting member 5 (FIG. 4). Are not shown) and a connecting portion 10 that connects the joint portion 9 and the fixing portion (not shown in FIG. 4). Note that the form of engagement with the reflecting member 5 and the material of the joint 9b and the like are the same as those shown in FIGS.

  Here, the joint portion 9b of the fixing member 1b takes into account the degree of the thickness (2 mm) of the diffusion plate 2 described above, leaving a necessary and sufficient thickness to support the weight of the diffusion plate 2, and the spot facing portion 37. Determining the depth of. Specifically, it is desirable to perform the spot facing process until the thickness remaining after forming the spot facing portion 37 (thickness of the diffusion plate 2) is about 0.5 mm. That is, it is desirable that the depth of the spot facing portion 37 be about 1.5 mm.

  Further, as shown in FIG. 5, the spot facing portion 37 may be filled using the disk-shaped member 13. In a state where the spot facing portion 37 is filled with the disk-shaped member 13, the joint portion 9 b of the fixing member 1 b is hidden behind the spot facing portion 37 when viewed from the front side (the upper side in FIG. 5) of the diffusion plate 2. There is no such thing.

  Further, the material of the disk-shaped member 13 has a transmittance equivalent to that of the diffusion plate 2 so that light incident on the diffusion plate 2 from the CCFL 3 and the reflection member 5 is not affected by the presence of the fixing member 1. To be adjusted. Preferably, it is conceivable that the disc-like member 13 is made of the same material as the diffusion plate 2. By making the same material, it is possible to make the transmittance of the diffusion plate 2 and the transmittance of the disk-like member 13 substantially equal, and to suppress uneven brightness on the diffusion plate 2. At this time, an optical coupling agent such as silicon grease is applied between the diffusing plate 2, the disk-shaped member 13, and the bonding portion 9 b, and the diffusing plate 2, the disk-shaped member 13, the bonding portion 9 b, Is desirably optically continuous. The fixing member 1b is preferably formed of a transparent member so as not to be affected by light incident on the diffusion plate 2 from the CCFL 3 and the reflecting member 5. Therefore, the fixing member 1b does not need to be injection-molded in two colors, and can be manufactured at a low cost.

  Further, in the above description, the spacer 25 and the like are provided integrally with the casing 25 and the like by sandwiching the casing 25 and the reflection member 5 with the locking portion 35 provided on the substrate portion 33. A configuration in which either the housing 25 or the reflection member 5 is sandwiched by the locking portion 35 provided on the substrate portion 33 and the spacer 8 or the like is provided integrally with the housing 25 or the like may be employed. For example, as shown in FIG. 6, the reflection member 5 may be provided with a through hole larger than the substrate portion 33 and sandwich only the housing 25.

  In order to further reduce the luminance unevenness generated in the liquid crystal display device 21, the amount of light transmitted through the joint 9 in FIG. 1, the joint 9b in FIG. 4, and the disc-like member 13 in FIG. It is effective to use the same amount of light that passes through the diffusion plate 2. Therefore, for example, in the case of the disk-shaped member 13 in FIG. 5, since the joint portion 9 b is formed of a transparent member, the transmittance of the disk-shaped member 13 needs to be lower than that of the diffusion plate 2. As a result, the amount of light transmitted through the disk-shaped member 13 and the amount of light transmitted through the diffusion plate 2 can be made the same.

  Further, in the fixing member 1 (1b), the whole is made of a transparent material, and the end surface 39 (see FIGS. 3 and 4) of the joint portion 9 (9b) is colored (light of a translucent material or the like). By covering with a material whose transmittance is appropriately adjusted, the same effect as when the joint 9 (9b) of the fixing member 1 (1b) is made translucent may be obtained.

  The above-described backlight device 23 is a backlight device having a configuration in which a light source is disposed in a housing and a diffusion plate is disposed in front of the light source, and prevents the diffusion plate from being bent forward. And at least a part of the transmittance is adjusted so that the luminance distribution on the diffuser plate is substantially uniform.

  In the above description, the backlight device 23 is used for the liquid crystal display device 21, but the backlight device 23 may be used for other devices.

1, 1b Fixing member 2 Diffusion plate 3 CCFL
4 Lamp holder 5 Reflective member 6 Optical sheet 7 Liquid crystal panel 8 Spacer 9, 9b Joint portion 10 Connection portion 11 Fixing portion 12 Screw hole 13 Disk-shaped member 21 Liquid crystal display device 23 Backlight device 25 Housing 27 Through hole (through hole) )

Claims (4)

A housing having one open surface;
A light source disposed in the housing;
A diffusion plate that is disposed on the open surface of the housing and diffuses and transmits the light emitted from the light source;
Bending in which at least part of the transmittance is adjusted so that the diffusion plate is prevented from bending in the light transmission direction of the diffusion plate and the luminance distribution of the light transmitted through the diffusion plate is substantially uniform. A prevention member;
A backlight device comprising:   The backlight device according to claim 1, wherein one end portion of the deflection preventing member is engaged with a through hole formed in the diffusion plate.   3. The backlight according to claim 1, wherein the one end portion of the deflection preventing member is made of a material having a transmittance equal to or lower than the transmittance of the diffusion plate. apparatus. The backlight device according to any one of claims 1 to 3,
An optical sheet disposed at a position where the light emitted from the light source passes through the diffusion plate;
A liquid crystal panel disposed at a position where the light passes through the optical sheet;
A liquid crystal display device comprising:

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