JP2007073194A - Direct backlight device and thin display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct backlight device capable of enhancing directivity of light emitted from respecting light emitting areas when a strip-like luminance distribution is provided in a display screen of a liquid crystal display device by forming the plurality of light emitting areas with a plurality of light sources and independently controlling luminance of the respective light emitting areas, high in luminance uniformity in the display screen of the liquid crystal display device when all the light emitting areas are lit, and having a simple structure. <P>SOLUTION: A plurality of cylindrical light sources 2 capable of forming a plurality of light emitting areas, and allowing luminance of the respective light emitting areas to be independently adjusted are arranged in parallel with each other between a diffusion layer 4 for diffusing and emitting light entered therein and a planar reflecting plate 3a for reflecting light which are arranged oppositely to each other; reflecting walls 5 each having a height in the normal direction from the reflecting plate 3a is mounted on the reflecting plate 3a so as to be positioned between the cylindrical light sources 2 when viewed from a plane parallel with the reflecting plate 3a; the height (e) of the reflecting wall 5 located at both ends is set smaller than the height (d) of the reflecting walls 5 located at positions other than both the ends. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a direct type backlight device including a plurality of cylindrical light sources capable of independently adjusting brightness, and a thin display device such as a liquid crystal TV and a liquid crystal monitor using the direct type backlight device.

  In a direct backlight device used in a conventional liquid crystal display device, all light sources are always turned on when the liquid crystal display device is used. For example, when displaying an image in which a dark region occupies most of the display screen. There was a problem that the contrast could not be taken sufficiently, such as white floating.

  Further, there is a problem that the contrast cannot be improved even when the luminance of all light sources is adjusted according to the average luminance in the display screen of the liquid crystal display device. For example, when a dark region occupies most of the display screen, it is possible to improve the apparent contrast by reducing the luminance of all light sources. However, since the brightness adjustment of the bright area is performed at the same level as that of the dark area, the relative brightness in the display screen does not change, and the contrast is not effectively improved.

  In order to solve the above-described problems, the backlight of the liquid crystal display device has a plurality of light emitting regions, and each of these light emitting regions is provided with a fluorescent lamp, and each fluorescent lamp is sequentially turned on and off one by one. A liquid crystal display device is disclosed (for example, see Patent Document 1).

  In such a device, a plurality of cylindrical light sources are divided into each light emitting area, and the brightness of each light emitting area is adjusted independently, thereby providing a band-like luminance distribution in the display screen and improving the contrast in the display screen. Can be made. For example, when a dark region occupies most of the display screen of the liquid crystal display device, only the brightness of the dark region is reduced and the brightness of the bright region is not changed, thereby improving the contrast in the display screen of the liquid crystal display device. Here, providing the striped luminance distribution in the display screen by adjusting the luminance of the cylindrical light source in each light emitting region is referred to as strip-shaped control.

  When performing strip-shaped control, if the directivity of light emitted from the light emitting area is low, the light is dispersed outside the light emitting area, and light is superimposed on other areas that are turned off, so the contrast in the display screen decreases. To do. On the other hand, when the directivity of the light emitted from each light emitting area is high, the light is not dispersed in other areas that are turned off, so that the contrast in the display screen is improved. Here, the directivity indicates the spread of the luminance distribution on the display screen of each light emitting area, and the directivity increases when the spread of the luminance distribution becomes narrow.

  In order to increase the directivity of each light emitting region when performing strip-shaped control, in Patent Document 2, a plurality of paraboloids are provided on a substrate, and a plurality of light sources are provided in a space defined by each paraboloid, A direct type backlight device in which a light shielding layer is provided on the light source is disclosed. The light shielding layer is formed on the surface facing the parabolic opening of the light source. Thereby, the light emitted from the light source in the direction of the opening can be blocked, and a bright illumination means with high directivity can be provided.

Japanese Patent Laid-Open No. 11-202286 (page 4, FIG. 1) JP 2002-278470 A (5th page, FIG. 3)

  However, the direct type backlight device disclosed in Patent Document 2 has a problem in that it is difficult to manufacture and has a high cost due to its complicated structure. Further, when all the light emitting areas are turned on, there is a problem that the contact portion of each paraboloid becomes a local dark portion on the display screen, and the luminance uniformity in the display screen is deteriorated. In order to solve the problem caused by the dark part, it is necessary to take measures such as widening the distance between the paraboloid and the light diffusing plate or using a large number of light diffusing plates to diffuse the dark part. Other problems such as thickening of the substrate and an increase in optical members occur.

  The present invention has been made to solve the above-described problems. When performing strip-shaped control, the directivity of light emitted from each light emitting area is improved and all the light emitting areas are turned on. An object of the present invention is to provide a direct type backlight device having a simple structure with high luminance uniformity in the display screen of a liquid crystal display device.

  In the direct type backlight device according to the present invention, a plurality of cylindrical light sources capable of independently adjusting brightness are arranged in parallel between the diffusion layer and the reflecting plate, and have a height in the normal direction from the reflecting plate. The reflecting wall is arranged on the reflecting plate so as to be positioned between the cylindrical light sources, and the height of the reflecting walls located at both ends of the plurality of reflecting walls is lower than the height of the reflecting wall located at other than both ends. It is characterized by.

  In the direct type backlight device according to the present invention, a plurality of cylindrical light sources capable of independently adjusting the brightness are arranged in parallel between the diffusion layer and the reflecting plate, and the height from the reflecting plate in the normal direction is set. A reflecting wall having a thickness of 2 is placed on the reflecting plate so as to be positioned between the cylindrical light sources, and the height of all the reflecting walls is equal to or less than the sum of the shortest distance between the reflecting plate and the cylindrical light source and the tube diameter of the cylindrical light source. It is characterized by that.

  According to the present invention, when the strip-like control is used, it is possible to realize a direct type backlight device having a simple structure in which the contrast of the liquid crystal display device is improved and the luminance uniformity in the display screen is high.

  The direct type backlight device according to the present invention can be applied to any backlight device including columnar light sources arranged in parallel, but hereinafter, it is assumed to be applied to a liquid crystal display device including a liquid crystal panel. A case where a cold cathode tube that is common in a liquid crystal display device is used as a cylindrical light source will be described.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing a basic configuration of a direct type backlight device 1 (hereinafter referred to as the present device 1) according to Embodiment 1 of the present invention. In the entire embodiment 1, for convenience of explanation, as shown in FIG. 1 (a), the left and right directions with respect to the paper surface are the X direction or the vertical direction, the direction perpendicular to the paper surface is the Y direction or the horizontal direction, and the paper surface. Thus, the vertical direction is defined as the Z direction or the vertical direction. The apparatus 1 includes a cold cathode tube 2, which is a cylindrical light source capable of independently adjusting the brightness, a reflector 3, a diffusion layer 4, and a reflecting wall 5. The size of the apparatus 1 in the XY plane is The angle is about 30 inches (length 384 mm × width 644 mm). The bottom surface portion 3 a of the reflector 3 and the diffusion layer 4 face each other with a predetermined distance, and the cold cathode tube 2 is located between the bottom surface portion 3 a of the reflection plate 3 and the diffusion layer 4.

  The cold cathode tubes 2 have a tube diameter of 4 mm, 16 are arranged in parallel with the Y direction as the longitudinal direction, and emit light. In the first embodiment, eight units are formed with two cold cathode tubes 2 as one unit, and inverter control is performed for each unit.

  The reflecting plate 3 is composed of a bottom surface portion 3 a and a side surface portion 3 b and reflects light emitted from the cold cathode tube 2 toward the diffusion layer 4. Of the reflector 3, the bottom surface portion 3a is disposed on the lower surface of the cold cathode tube 2 in parallel with the XY plane, and the side surface portion 3b is disposed at an angle α = 60 ° with respect to the bottom surface portion 3a. .

  The diffusion layer 4 is a light diffusion plate having a thickness of about 2 mm and two light-concentrating diffusion sheets having a thickness of about 0.2 mm stacked on the upper surface of the cold cathode tube 2 in an XY plane. They are arranged in parallel. The diffusion layer 4 faces the bottom surface portion 3a of the reflector 3 with the cold cathode tube 2 in between, and the light directly emitted in the direction of the diffusion layer 4 out of the light emitted from the cold cathode tube 2, and the reflector The light reflected in the direction of the diffusion layer 4 by the bottom surface portion 3a and the side surface portion 3b of 3 is incident on the diffusion layer 4, is diffused while passing through the diffusion sheet, and is further disposed above the diffusion layer 4. Head to the LCD panel (not shown).

  The reflecting wall 5 is a flat surface located at the center between the respective units composed of the cold cathode fluorescent lamps 2 and is disposed upright on the bottom surface portion 3a of the reflecting plate 3, that is, parallel to the YZ plane. Specifically, the reflecting wall 5 is a thin plate-like member having a predetermined height in the normal direction from the bottom surface portion 3a of the reflecting plate 3 and extending in the Y direction. A reflective film that reflects the light emitted from 2 is coated. Therefore, the light emitted from the cold cathode fluorescent lamp 2 is reflected by the reflection wall 5 in addition to the reflection plate 3. In addition, a plurality of reflection walls 5 are installed in the apparatus 1 and are arranged so as to partition each of the plurality of light emitting regions. In the first embodiment, eight units divided by the reflecting wall 5 are defined as light emitting areas E1 to E8. The intervals in the X direction of the light emitting areas E1 to E8 are 48 mm, respectively.

  In FIG. 1A, the distance in the normal direction from the bottom surface portion 3a of the reflector 3 to the position closest to the bottom surface portion 3a of the reflector 3 of the cold cathode tube 2, that is, the bottom surface portion 3a of the reflector 3 and the cold cathode. The shortest distance from the tube 2 is a, the tube diameter of the cold cathode tube 2 is b, and the distance from the diffusion layer 4 to the normal line to the position closest to the diffusion layer 4 of the cold cathode tube 2, that is, the diffusion layer 4 and the cold cathode. C is the shortest distance from the tube 2, d is the height of the reflecting wall 5 that partitions the light emitting regions E2 to E7 among the plurality of reflecting walls 5, that is, the reflecting walls 5 located at both ends, and the light emitting regions E1 and E2. The height of the reflecting wall 5 that partitions E7 and E8, that is, the height of the reflecting wall 5 located at both ends is denoted by e, and the angle formed by the bottom surface portion 3a of the reflecting plate 3 and the side surface portion 3b of the reflecting plate 3 is denoted by α. In the present apparatus 1, a is 4 mm, b is 4 mm as described above, c is 18 mm, and α is 60 ° as described above.

Next, the action of the reflecting wall 5 on the locus of light emitted from the cold cathode tube 2 will be described with reference to FIGS. 2 and 3.
FIG. 2 is an enlarged view of one unit when the reflection wall 5 is not provided in the apparatus 1 of FIG. 1A, and represents a conventional general direct type backlight apparatus. In FIG. 2, a pair of cold cathode tubes 2 are arranged in parallel with respect to the bottom surface portion 3 a of the reflector 3 and the diffusion layer 4, and 201 to 204 indicate the trajectories of light emitted from the cold cathode tubes 2.

  In FIG. 2, the light emitted from the cold cathode tube 2 is reflected by the bottom surface portion 3a of the reflector 3 as 201 and 204, or directly toward the diffusion layer 4 as 202 and 203, and greatly increases in the X direction. After the dispersion, the diffusion layer 4 is reached.

  FIG. 3 is an enlarged view of one unit when the reflection wall 5 is provided in the apparatus 1 of FIG. 1A. In addition to the pair of cold cathode tubes 2 installed as shown in FIG. One reflection wall 5 is provided outside the cold cathode tube 2 in the X direction. The two reflecting walls 5 having a predetermined height are installed so as to stand upright on the bottom surface portion 3 a of the reflecting plate 3. Reference numerals 301 to 306 in FIG. 3 indicate the trajectory of light emitted from the cold cathode fluorescent lamp 2.

  In FIG. 3, only light that has passed through the upper end of the reflecting wall 5 in the Z direction after being emitted from the cold cathode fluorescent lamp 2 directly reaches the diffusion layer 4 as indicated by 301 and 306. When the reflecting wall 5 becomes high, the amount of light that can pass through the upper end of the reflecting wall 5 is limited, and the dispersion in the X direction of the light that can pass through the upper end of the reflecting wall 5 is suppressed. On the other hand, the light reflected by the reflecting wall 5 and the bottom surface portion 3a of the reflecting plate 3 is diffused only after being reflected so that it can pass above the upper end of the reflecting wall 5 as in 302 to 305. Reach layer 4. Therefore, any light that reaches the diffusion layer 4 is suppressed from being dispersed in the X direction by the reflection wall 5 and concentrated on the diffusion layer 4 above the unit.

  FIG. 4 is a graph for explaining a general luminance distribution in the case of FIG. 2 and FIG. The vertical axis indicates the luminance of light emitted from the diffusion layer 4, and the horizontal axis indicates the position in the X direction in the diffusion layer 4. Reference numeral 401 denotes a luminance distribution when the reflection wall 5 is not provided, and reference numeral 402 denotes a luminance distribution when the reflection wall 5 is provided. On the horizontal axis, one unit in FIG. 2 or FIG. 3 is located near the position of the diffusion layer 4 where the luminance of the luminance distribution 401 or 402 peaks. In FIG. 4, as shown in the luminance distribution 402, when the reflection wall 5 is provided, the luminance on the diffusion layer 4 near the position of the unit is increased compared to the luminance distribution 401 without the reflection wall 5. The spread of luminance in the X direction is suppressed and directivity is improved.

  Furthermore, the directivity improvement obtained by the reflecting wall 5 in the present invention will be described in detail with reference to FIGS.

  FIG. 5 is a graph showing the luminance distribution when the height of the reflecting wall 5 is changed in the apparatus 1 of FIG. The vertical axis represents the luminance on the diffusion layer 4, and the horizontal axis represents the position in the X direction in the diffusion layer 4. Here, only the cold-cathode tube 2 in the light-emitting region E4 is turned on, and the luminance on the diffusion layer 4 is measured at each position in the X direction with the Y-direction position fixed at the center. In FIG. 5, 501 does not include the reflecting wall 5, 502 indicates that the height of the reflecting wall 5 is 8 mm, 503 indicates that the height of the reflecting wall 5 is 12 mm, and 504 indicates the height of the reflecting wall 5. Shows the luminance distribution in the case where all are 16 mm.

  In FIG. 5, when the height of the reflecting wall 5 is increased, the peak value of the luminance is increased, and the spread of the luminance in the horizontal axis direction is narrowed. Even when the diffusing layer 4 is composed of only a light diffusing plate without using two diffusing sheets, the luminance distribution is the same as in FIG.

  FIG. 6 is a graph showing the half-value width of the luminance in the case of FIG. 5, the vertical axis shows the half-value width of the luminance on the diffusion layer 4, and the horizontal axis shows the height of the reflecting wall 5. Here, when the reflecting wall 5 is not provided (height 0 mm), the full width at half maximum is obtained from the luminance measured when the height of the reflecting wall 5 is all 4 mm, 8 mm, 12 mm, and 16 mm. In FIG. 6, the full width at half maximum becomes narrower as the reflecting wall 5 is made higher.

  As shown in FIGS. 5 and 6, by providing the reflecting wall 5 as in the present apparatus 1 in FIG. 1A, the directivity of light emitted from the cold cathode tube 2 can be improved, and further reflected. As the height of the wall 5 is increased, the half width of the luminance is narrowed, and a luminance distribution with higher directivity can be obtained.

  Next, the effect | action with respect to strip | belt-shaped control of the reflective wall 5 is demonstrated. The band-shaped control is intended to improve the contrast in the display screen by adjusting the luminance of each light emitting area in accordance with the luminance distribution in the display screen of the liquid crystal display device. The controllability of the band-shaped control can be determined by the difference in brightness between when the light emission is at the maximum level and when the light is turned off in each light-emitting area. If the controllability of the band-shaped control is good, the difference in brightness between the light-emitting areas increases. As a result, the brightness difference between the bright part and the dark part in the display screen is increased, and the contrast is improved.

  As shown in FIG. 3, the reflection wall 5 suppresses the dispersion of the light reaching the diffusion layer 4 in the X direction, so that the luminance of the cold cathode tube 2 of the unit is strongly reflected in the luminance on the diffusion layer 4. . Therefore, the contrast is improved.

  FIG. 7 shows that the cold cathode tubes 2 in the light emitting areas E1, E2, E5 and E6 are turned off and the cold cathode tubes 2 in the light emitting areas E3, E4, E7 and E8 are turned on in the apparatus 1 of FIG. It is a graph which shows distribution of relative luminance in the case. The vertical axis represents relative luminance, and the horizontal axis represents the position of the diffusion layer 4 in the X direction. Here, the luminance is measured at the same location as the location where the luminance is measured in FIG. 5, and the relative luminance is obtained with the maximum luminance on the diffusion layer 4 being 1. E1 to E8 on the horizontal axis correspond to the light emitting areas E1 to E8 of the apparatus 1 in FIG. A solid line 701 indicates the relative luminance distribution when the reflecting wall 5 is not provided, and a dotted line 702 indicates the relative luminance distribution when the height of the reflecting wall 5 is all 8 mm. Note that m / n, which is the contrast of the light emitting regions E3 to E6, is evaluated with the maximum value of the relative luminance in the light emitting regions E3 and E4 as m and the minimum value of the relative luminance in the light emitting regions E5 and E6 as n.

  In FIG. 7, the maximum value m of the relative luminance is larger when the height of the reflecting wall 5 is all 8 mm than when the reflecting wall 5 is not provided, and the minimum value n of the relative luminance is that of the reflecting wall 5. It is smaller when the height of the reflecting wall 5 is all 8 mm than when it is not provided. That is, the value of m / n is larger when the reflecting wall 5 is provided than when the reflecting wall 5 is not provided, and the contrast in the E3 to E6 region on the diffusion layer 4 is increased.

  FIG. 8 is a graph showing the value of m / n when the height of the reflecting wall 5 is changed in the apparatus 1 of FIG. The vertical axis represents m / n in the light emitting regions E3 to E6, and the horizontal axis represents the height of the reflecting wall 5. The light emitting area to be turned on and off, the luminance measurement location, and the selection method of m and n are the same as in FIG. Here, m / n was measured when the height of all the reflection walls 5 was 0 mm, 4 mm, 8 mm, 12 mm, 13 mm, 14 mm, and 16 mm. In addition, the height of the reflecting wall 5 indicates that the reflecting wall 5 is not provided.

  In FIG. 8, it can be seen that as the height of the reflecting wall 5 increases, the value of m / n increases and the contrast is improved.

  FIG. 9 shows an image of the relative luminance distribution observed on the diffusion layer 4 in the state shown in FIG. This is achieved by extending the relative luminance in the Y direction, which is the longitudinal direction of the cold cathode tube 2, based on the relative luminance on the diffusion layer 4 at each position in the X direction at the center of the Y direction obtained in FIG. This represents the XY plane of the diffusion layer 4 when the strip control is performed. This image diagram is represented by a gray scale of 256 gradations where 1 which is the maximum value of the relative luminance in FIG. 7 is R = B = G = 255. E1 and E8 in FIG. 9 correspond to the light emitting areas E1 and E8 in FIG.

  FIG. 9A shows an image of the relative luminance distribution obtained from the relative luminance 701 in FIG. 7 and without the reflection wall 5, and FIG. 9B is obtained from the relative luminance 702 in FIG. An image of the relative luminance distribution when the height of the reflection wall 5 is all 8 mm is shown. From FIG. 9, when the reflecting wall 5 is not provided, the spread of the two bright portions is large. However, when the reflecting wall 5 is provided, the two bright portions are narrowly spread, particularly in the dark portion at the central portion. It can be visually confirmed that the contrast is enhanced and the contrast is improved.

  As shown in FIGS. 7 to 9, by providing the reflecting wall 5 as in the present apparatus 1 in FIG. 1A, the controllability of the strip control can be improved, and the height of the reflecting wall 5 is further increased. The higher the control, the higher the controllability of the belt-like control.

  Next, the effect of luminance uniformity of the apparatus 1 will be described.

  As shown in FIG. 3, by providing the reflecting wall 5, dispersion of light emitted from the cold cathode fluorescent lamp 2 in the X direction can be suppressed, but the light is condensed on the diffusion layer 4 on each light emitting region. The light reaching the diffusion layer 4 on one light emitting region from another light emitting region is reduced. Conventionally, when the luminance of all the light emitting areas is the same, the amount of light superimposed on both ends is smaller than the central part of the diffusion layer 4, but the light reaching from the other light emitting areas is reflected by the reflecting wall 5. Since the overlap of light is suppressed and the reflection wall 5 is not provided, a decrease in luminance at the end is larger than that in the case where the reflection wall 5 is not provided, and this may be observed as luminance unevenness on the diffusion layer 4. . In addition, since the light entering the portion directly above the reflecting wall 5 of the diffusing layer 4 is reduced, a local dark portion is generated on the diffusing layer 4, which may cause uneven brightness. Note that as the height of the reflecting wall 5 is increased, the dispersion of light from the cold cathode fluorescent lamp 2 in the X direction is suppressed and the luminance of the end portion is greatly reduced. It is considered that the light entering the upper portion is reduced and local dark portions on the diffusion layer 4 are likely to be generated, and the possibility of uneven luminance is increased.

  FIG. 10 is a graph showing a relative luminance distribution when the reflection wall 5 is not provided in the apparatus 1 and when the height of the reflection wall 5 is all 8 mm. Since the vertical axis, the horizontal axis, the measurement location of the luminance, and the method of obtaining the relative luminance are the same as those in FIG. Here, all the cold cathode fluorescent lamps 2 are turned on. In FIG. 1A, the distance a + b from the bottom surface portion 3a of the reflector 3 to the position closest to the diffusion layer 4 of the cold cathode tube 2 is 8 mm.

  In FIG. 10, a solid line 1001 indicates a relative luminance distribution when the reflecting wall 5 is not provided, and a dotted line 1002 indicates a relative luminance distribution when the height of the reflecting wall 5 is all 8 mm. As shown in FIG. 10, the relative luminance distribution 1002 when the reflecting wall 5 is provided is substantially equal to the relative luminance distribution 1001 when the reflecting wall 5 is not provided. Therefore, it can be seen that when the height of the reflecting wall 5 is 8 mm, the luminance unevenness does not occur, and the same luminance uniformity as that without the reflecting wall 5 can be maintained.

Next, the case where this state is observed on the diffusion layer 4 will be described.
FIG. 11 shows an image of the relative luminance distribution observed on the diffusion layer 4 when the reflection wall 5 is not provided in the apparatus 1 and when the height of the reflection wall 5 is all 8 mm. This is obtained from the relative luminance in FIG. 10 by the same method as in FIG. 9. FIG. 11A shows an image of the relative luminance distribution when the reflecting wall 5 is not provided, and FIG. An image of the relative luminance distribution when the height of the wall 5 is all 8 mm is shown.

  When viewing FIG. 11 (b), luminance unevenness is not observed, and FIGS. 11 (a) and 11 (b) are substantially equal, and it can be seen that the luminance uniformity is maintained visually.

  Although the light reaching the both end portions of the diffusing layer 4 and the light entering the portion directly above the reflective wall 5 may be reduced due to the installation of the reflective wall 5, there is a possibility that uneven luminance is observed. As described above, even when the height of the reflection wall 5 is the height closest to the diffusion layer 4 of the cold cathode tube 2, the luminance of the end portion of the diffusion layer 4 or the portion directly above the reflection wall 5 of the diffusion layer 4. The decrease in brightness does not occur, and uneven brightness is not observed. Therefore, when the reflecting walls 5 having the same height are installed, the height of the reflecting wall 5 is the height from the bottom surface portion 3a of the reflecting plate 3 to the position closest to the diffusion layer 4 of the cold cathode tube 2, that is, reflecting. As long as it is less than the sum of the shortest distance a between the bottom surface portion 3a of the plate 3 and the cold cathode tube 2 and the tube diameter b of the cold cathode tube 2, the reflective wall 5 is not provided at any height. The same relative luminance distribution is obtained, and the same luminance uniformity can be maintained.

In FIG. 1A, the shortest distance a between the bottom surface portion 3a of the reflector 3 and the cold cathode tube 2, the tube diameter b of the cold cathode tube 2, the height d of the reflecting wall 5 located at both ends, and located at both ends. When the height e of the reflecting wall 5 is used, the conditions of the heights d and e of the reflecting wall 5 that can maintain the uniformity of the brightness when the reflecting walls 5 having the same height are installed are as follows: 1).
0 ≦ d = e ≦ a + b Formula (1)
In order to maximize the directivity and contrast while maintaining the uniformity of brightness, the height of the reflecting wall 5 is set to the height closest to the diffusion layer 4 of the cold cathode tube 2, that is, a + b. Is desirable. FIG. 1B shows a schematic configuration diagram in the case where the height of the reflection wall 5 is set to the height closest to the diffusion layer 4 of the cold cathode tube 2. In addition, in the figure, the same code | symbol is attached | subjected to the structure same as FIG. 1 (a), and the description is abbreviate | omitted.

  In the above description, the reflection walls 5 have the same height. However, when the reflection walls 5 having the same height are at the height closest to the diffusion layer 4 of the cold-cathode tube 2, the brightness is reduced. Since luminance unevenness is not observed, even if the height of some of the plurality of reflection walls 5 is lower than the position closest to the diffusion layer 4 of the cold cathode tube 2, the luminance due to the decrease in luminance It is thought that unevenness is not observed. That is, as long as the height of the reflecting wall 5 is not more than the sum of the shortest distance a between the bottom surface portion 3a of the reflecting plate 3 and the cold cathode tube 2 and the tube diameter b of the cold cathode tube 2, the height of the reflecting wall 5 is increased. Even if the lengths are not all the same, it is considered that uneven brightness is not observed.

  As described above, according to the first embodiment, by providing the reflecting wall 5, it is possible to obtain a direct type backlight device having a high contrast showing directivity and controllability of strip-shaped control. And the controllability of directivity and strip | belt-shaped control can further be improved by making this reflective wall 5 high.

  In addition, the simple structure in which the reflecting plate 3 includes the reflecting wall 5 makes it possible to easily manufacture a direct type backlight device having high directivity and high controllability for strip-shaped control at low cost.

  Further, when the height of the reflecting walls 5 is all the same, a direct type back with sufficient uniformity of luminance is maintained by making it equal to or less than the height closest to the diffusion layer 4 of the cold cathode tube 2. A light device can be obtained.

  By applying the direct type backlight device as described above to a liquid crystal display device which is one of thin display devices, a liquid crystal display device with high directivity and controllability of band-like control and sufficiently uniform luminance can be obtained. be able to. Further, such a liquid crystal display device can be easily manufactured at low cost.

Embodiment 2. FIG.
In Embodiment 1, although the case where all the reflection walls 5 were the same height was described, you may make it the height of the reflection walls 5 differ. In the second embodiment, among the reflecting walls 5 arranged in parallel in the X direction, the reflecting walls 5 positioned at both ends are lower than the reflecting walls 5 positioned at both ends, and the reflecting walls 5 positioned at the ends other than the both ends. A case where the height d is higher than the position closest to the diffusion layer 4 of the cold cathode tube 2 will be described.

  FIG. 12 is a schematic configuration diagram showing a basic configuration of the device 1 according to the second embodiment of the present invention. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the second embodiment, the height e of the reflection walls 5 that divide the light emitting regions E1 and E2, and E7 and E8 in FIG. The height of the reflection wall 5 that partitions the light emitting regions E2 to E7, that is, the height d of the reflection wall 5 positioned at both ends is lower.

First, with reference to FIG. 13 and FIG. 14, the action of the reflection wall 5 in the second embodiment on the locus of light emitted from the cold cathode tube 2 will be described.
FIG. 13 is an enlarged view of the right side of the present apparatus 1 in FIG. 1 (a), where the height of the reflection wall 5 is all equal and higher than the position closest to the diffusion layer 4 of the cold cathode tube 2. Show.
FIG. 14 is an enlarged view of the right side of the apparatus 1 in FIG. 12, and the reflection wall 5 located at the right end is lower than the reflection wall 5 located outside the right end, and the height of the reflection wall 5 located outside the right end is shown. The case where is higher than the position closest to the diffusion layer 4 of the cold cathode tube 2 is shown.

  In FIG. 13, the light from each light emitting region is suppressed from spreading in the X direction by the reflection wall 5, and thus the light reaching the right end region of the diffusion layer 4 indicated by 1301 from other regions is reduced. Thereby, in the diffusion layer 4, the luminance at the right end is lowered, the luminance uniformity is impaired, and luminance unevenness may occur.

  On the other hand, in FIG. 14, the height of the reflecting wall 5 located at the right end is lower than that of the reflecting wall 5 located at the right end in FIG. A lot of light reaches the right end region of the diffusion layer 4 indicated by 1401. Accordingly, it is possible to prevent a decrease in luminance at the right end of the diffusion layer 4 as compared with the case where the heights of the reflection walls 5 are all the same.

  As an example in which the height e of the reflecting wall 5 positioned at both ends is set lower than the height d of the reflecting wall 5 positioned other than both ends, the height d is set to 12 mm and will be described below.

  15 to 17 are graphs showing the distribution of relative luminance. Since the vertical axis, the horizontal axis, the measurement location of the luminance, and the method of obtaining the relative luminance are the same as those in FIG. Here, all the cold cathode fluorescent lamps 2 are turned on.

  15, the solid line 1501 indicates the relative luminance distribution when the reflecting wall 5 is not provided, the dotted line 1502 indicates the relative luminance distribution when the height of the reflecting wall 5 is all 12 mm, and the solid line 1601 indicates the reflecting wall 5 in FIG. 17, the dotted line 1602 shows the distribution of relative luminance when the height d of the reflecting wall 5 positioned at both ends is 12 mm and the height e of the reflecting wall 5 positioned at both ends is 0 mm. , The solid line 1701 does not include the reflecting wall 5, and the dotted line 1702 indicates that the height d of the reflecting wall 5 positioned at both ends is 12 mm and the height e of the reflecting wall 5 positioned at both ends is 4 mm. The distribution of relative luminance is shown.

  In FIG. 15, the relative luminance distribution 1502 when the height of the reflecting wall 5 is all 12 mm is compared with the relative luminance distribution 1501 when the reflecting wall 5 is not provided, from the central portion of the diffusion layer 4, for example, the light emitting region E <b> 3. In E6, although there is a partial decrease, there is no problem of uneven brightness because it is not a significant decrease in brightness but a smooth curve. However, the luminance is greatly reduced at both ends of the diffusion layer 4 and is observed as luminance unevenness.

  In FIG. 16, the relative luminance distribution 1602 when the height d of the reflecting wall 5 positioned at both ends is 12 mm and the reflecting wall 5 positioned at both ends is not provided (the height is 0 mm) is the height of the reflecting wall 5 in FIG. 15. Compared to the relative luminance distribution 1502 when the thickness is all 12 mm, the relative luminance is improved as a whole and approaches the relative luminance distribution 1601 when the reflecting wall 5 is not provided. This setting has the effect of increasing the lowered relative luminance. Note that there are places where the relative luminance at both ends of the diffusion layer 4 is higher than the relative luminance at the central portion, such as the light emitting regions E2 and E7, and the relative luminance distribution is not smooth, but the luminance uniformity within the allowable range is Show.

  In FIG. 17, the relative luminance distribution 1702 when the height d of the reflecting wall 5 positioned at both ends is 12 mm and the height e of the reflecting wall 5 positioned at both ends is 4 mm is the height of the reflecting wall 5 in FIG. The reduction of the relative luminance at both ends of the diffusion layer 4 as shown by the relative luminance distribution 1502 when the thickness is all 12 mm is improved, and the height d of the reflecting wall 5 positioned at both ends in FIG. A curve in which the relative luminance distribution does not increase as shown by the relative luminance distribution 1602 when the reflecting walls 5 located at both ends are not provided (height 0 mm), and the relative luminance distribution is smooth. It has become. Further, the relative luminance distribution has the same shape as the relative luminance distribution 1701 when the reflecting wall 5 is not provided. Accordingly, the luminance unevenness is not observed, and the same luminance uniformity as that in the case where the reflecting wall 5 is not provided can be maintained.

  In the above description, the case where the height d of the reflecting wall 5 positioned at both ends is set to 12 mm and the height e of the reflecting wall 5 positioned at both ends is set to 0 mm and 4 mm is described. When the height d of the reflecting wall 5 to be set is 12 mm, the best relative luminance distribution is shown when the height e of the reflecting wall 5 located at both ends is set to 4 mm.

  In the first embodiment, there is a restriction that the height of the reflecting wall 5 for maintaining the uniformity of luminance is “the height of the reflecting wall 5 is equal to or less than the position closest to the diffusion layer 4 of the cold cathode tube 2”. As shown in FIGS. 15 to 17, even when the height of the reflection wall 5 is higher than the position closest to the diffusion layer 4 of the cold cathode tube 2, the height e of the reflection wall 5 located at both ends is located at other than the both ends. By making the height lower than the height d of the reflecting wall 5, it is possible to widen the restriction on the height of the reflecting wall 5 for maintaining the uniformity of luminance.

  As described in the first embodiment, when the heights of the reflection walls 5 are all the same, diffusion is achieved by setting the height of the reflection walls 5 to be equal to or less than the position closest to the diffusion layer 4 of the cold cathode tube 2. Since the luminance at both ends of the layer 4 does not decrease, the height e of the reflection walls 5 located at both ends in the second embodiment is also applied to the diffusion layer 4 of the cold cathode tube 2 in order to keep the luminance uniform. It is desirable to be below the closest position.

  Furthermore, by adjusting the height e of the reflecting walls 5 located at both ends, it is possible to bring the relative luminance distribution to the same level as when the reflecting walls 5 are not provided. In the size of the apparatus of the second embodiment, as shown in FIG. 17, when the height d of the reflecting wall 5 located at both ends is 12 mm, the height e of the reflecting wall 5 located at both ends is 4 mm. It is desirable to make it.

The controllability of the strip control at this time will be described with reference to FIG.
FIG. 18 is a graph showing the distribution of relative luminance when the strip control similar to that in FIG. 7 is performed. Since the light emitting area to be turned on or off, the vertical axis, the horizontal axis, the measurement location of the luminance, and the method for obtaining the relative luminance are the same as those in FIG. The solid line 1801 indicates the relative luminance distribution when the height of the reflecting wall 5 is all 8 mm, and the dotted line 1802 indicates the height d of the reflecting wall 5 located at both ends of the reflecting wall 5 and 12 mm. The relative luminance distribution when the height e is 4 mm is shown.

  In FIG. 18, the difference between the maximum value m and the minimum value n of the relative luminance is that the height of the reflection wall 5 located at both ends is 12 mm and the positions at both ends, compared to the case where the height of the reflection wall 5 is all 8 mm. The height when the height e of the reflecting wall 5 is 4 mm is larger, and the controllability of the strip-shaped control is good. Moreover, the value of m / n is large, and the contrast in the light emitting regions E3 to E6 on the diffusion layer 4 is such that the height d of the reflecting wall 5 located at both ends is set to be higher than the height of the reflecting walls 5 being 8 mm. The height becomes 12 mm when the height e of the reflecting wall 5 located at both ends is 4 mm.

  Further, from FIG. 8, the m / n value when the height of the reflecting wall 5 is all 12 mm is about 3.8. On the other hand, from FIG. 18, the m / n value is about 3.8 when the height of the reflecting wall 5 located at both ends is 12 mm and the height e of the reflecting wall 5 located at both ends is 4 mm. Thus, there is no influence on the contrast by reducing the height e of the reflecting walls 5 located at both ends.

In the above description, the case where the height d of the reflecting wall 5 positioned at both ends is set to 12 mm is described as an example of the case where the height of the reflecting wall 5 is set higher than the position closest to the diffusion layer 4 of the cold cathode tube 2. However, even if the height d of the reflecting wall 5 positioned at both ends is other than 12 mm, the brightness uniformity can be maintained by adjusting the height e of the reflecting wall 5 positioned at both ends. Hereinafter, the case where the height d of the reflecting wall 5 located at both ends other than 12 mm is other than 12 mm will be described.
Table 1 shows the heights of the reflecting walls 5 positioned at both ends when the luminance uniformity is the best with respect to the height d of the reflecting walls 5 positioned at other than the both ends in the direct type backlight device in FIG. e.

In Table 1, the first level indicates the height d of the reflecting wall 5 located at both ends, and the second level is visually observed when the reflecting wall 5 positioned at both ends is at the height indicated by the first level. When the luminance unevenness is not observed, the height e of the reflecting walls 5 positioned at both ends is shown.
In Table 1, when the height d of the reflecting wall 5 located at both ends is 12 mm, the best height for maintaining the uniformity of the brightness at the height e of the reflecting wall 5 located at both ends is 4 mm. This is as shown in FIG.
Further, when the height d of the reflecting wall 5 located at both ends is 8 mm, the height e of the reflecting wall 5 located at both ends is 8 mm. This means that the height of the reflecting wall 5 is all 8 mm. This is the same as the condition for maintaining the uniformity of luminance described in the first embodiment.

When the height d of the reflecting wall 5 located at both ends is 10 mm and 13 mm, the best heights for maintaining the luminance uniformity are 6 mm and 4 mm, respectively. Will be described below.
19 and 20 are graphs showing the distribution of relative luminance. Since the vertical axis, the horizontal axis, the measurement location of the luminance, and the method of obtaining the relative luminance are the same as those in FIG. Here, all the cold cathode fluorescent lamps 2 are turned on.

  In FIG. 19, the solid line 1901 indicates that the height of the reflecting wall 5 is all 10 mm, and the dotted line 1902 indicates the height d of the reflecting wall 5 located at both ends other than 10 mm and the height of the reflecting wall 5 positioned at both ends. The relative luminance distribution when e is 6 mm is shown.

  From FIG. 19, the relative luminance at both ends of the diffusion layer 4, which had been reduced when the height of the reflecting wall 5 was all 10 mm, is 10 mm and the height d of the reflecting wall 5 located at both ends is 10 mm. When the height e of the reflecting wall 5 is 6 mm, the improvement is made, and the curve of relative luminance becomes smooth.

  In FIG. 20, the solid line 2001 indicates that the height of the reflecting wall 5 is all 13 mm, and the dotted line 2002 indicates that the height d of the reflecting wall 5 located at both ends is 13 mm and the height of the reflecting wall 5 positioned at both ends. When e is set to 0 mm, a one-dot chain line in 2003 indicates a relative luminance distribution when the height d of the reflecting wall 5 positioned at both ends is 13 mm and the height e of the reflecting wall 5 positioned at both ends is set to 4 mm.

From FIG. 20, the relative luminance at both ends of the diffusion layer 4, which had been reduced when the height of the reflecting wall 5 was all 13 mm, is such that the height d of the reflecting wall 5 positioned at both ends is 13 mm and at both ends. When the height e of the reflection wall 5 is set to 0 mm or 4 mm, the reflection wall 5 is improved. By setting the reflection wall 5 as described above, it is possible to prevent uneven brightness due to a sharp decrease in luminance at both ends.
In addition, the height of the reflecting wall 5 located at both ends is the same as in FIG. 16 when the height d of the reflecting wall 5 located at both ends is 12 mm and the height e of the reflecting wall 5 located at both ends is 0 mm. When e is set to 0 mm, the relative luminance at both ends of the diffusion layer 4, for example, the vicinity of the light emitting region E7 is slightly high, and the relative luminance distribution is not smooth, but the luminance uniformity within the allowable range is shown. Similarly to FIG. 17 when the height d of the reflecting wall 5 positioned at both ends is 12 mm and the height e of the reflecting wall 5 positioned at both ends is 4 mm, the height of the reflecting wall 5 positioned at both ends is the same as in FIG. When e is 4 mm, the relative luminance distribution curve is smoother, and a relative luminance distribution with better luminance uniformity can be obtained.

Furthermore, the case where the height of the reflecting wall 5 is set to 14 mm will be described below with reference to FIG.
FIG. 21 is a graph showing the distribution of relative luminance, which is exactly the same as FIGS. 19 and 20 except for the height of the reflecting wall 5. In FIG. 21, the solid line 2101 indicates that the height of the reflection wall 5 is 14 mm, and the dotted line 2102 indicates the height d of the reflection wall 5 located at both ends other than both ends is 14 mm and the height of the reflection wall 5 located at both ends. When e is 0 mm, the alternate long and two short dashes line 2103 indicates the relative luminance distribution when the height d of the reflecting wall 5 positioned at both ends is 14 mm and the height e of the reflecting wall 5 positioned at both ends is 4 mm.

  From FIG. 21, the relative luminance distributions 2102 and 2103 when the height e of the reflecting wall 5 located at both ends is 0 mm and 4 mm are compared with the relative luminance distributions 1702, 1902 and 2003 in FIGS. Since the curve is not smooth, uneven brightness may be observed as compared with the case where the height d of the reflecting wall 5 located at both ends is 10 mm, 12 mm, or 13 mm. However, when the height of the reflecting wall 5 is all 14 mm, the relative luminance at both ends of the diffusion layer 4 is lowered, and the height d of the reflecting wall 5 located at both ends is 14 mm and located at both ends. When the height e of the reflection wall 5 is 0 mm or 4 mm, the reflection wall 5 is improved, and the curve of the relative luminance distribution is smoother.

  As described above, in the present apparatus 1 according to the first or second embodiment, when the heights of the reflecting walls 5 are all the same, the height of the reflecting wall 5 that maintains the uniformity of the brightness is the cold cathode tube 2. However, if the height e of the reflecting wall 5 located at both ends is made lower than the height d of the reflecting wall 5 located at both ends, the luminance uniformity can be improved. The height of the reflecting wall 5 that is the limit to be maintained can be increased to 13 mm in the reflecting walls 5 other than both ends. In addition, even when the height d of the reflection wall 5 located at both ends is 14 mm, the luminance reduction at both ends of the diffusion layer 4 can be improved, so that a certain level of luminance uniformity can be maintained. it can. In addition, when the height d of the reflection wall 5 located at the other end than the both ends is set to 10, 12, 13 mm in the size of the apparatus 1, the height e of the reflection wall 5 located at both ends is 6 mm, 4 mm, and 4 mm, respectively. It was confirmed that it was suitable.

  In the above description, the height e of the reflecting wall 5 positioned at both ends is the optimum height for maintaining the luminance uniformity. Accordingly, when the height d of the reflection wall 5 located at both ends other than both ends is larger than the height at the position closest to the diffusion layer 4 of the cold cathode tube 2, that is, between the bottom surface portion 3 a of the reflector 3 and the cold cathode tube 2. When the sum of the shortest distance a and the tube diameter b of the cold-cathode tube 2 is larger than a + b, the height e of the reflection walls 5 located at both ends is higher than the height of the position closest to the diffusion layer 4 of the cold-cathode tube 2. It can be seen that the luminance uniformity can be maintained if the distance is small, that is, the sum of the shortest distance a between the bottom surface portion 3a of the reflecting plate 3 and the cold cathode tube 2 and the tube diameter b of the cold cathode tube 2 is less than a + b. However, as described in the first embodiment, the condition of the height of the reflecting wall 5 that maintains the uniformity of luminance when the heights of the reflecting walls 5 are all the same is closest to the diffusion layer 4 of the cold cathode tube 2. Since the sum of the shortest distance a between the bottom surface portion 3a of the reflector 3 and the cold cathode tube 2 and the tube diameter b of the cold cathode tube 2 is equal to or less than a + b, in Embodiment 2, It is considered that the upper limit of the height e of the reflection walls 5 positioned at both ends for maintaining the uniformity of luminance is also a + b.

  Here, the shortest distance a between the bottom surface portion 3a of the reflector 3 and the cold cathode tube 2 in FIG. 12, the tube diameter b of the cold cathode tube 2, the shortest distance c between the diffusion layer 4 and the cold cathode tube 2, When the height d of the reflecting wall 5 positioned and the height e of the reflecting wall 5 positioned at both ends are used, the directivity and the controllability of the strip-shaped control are higher than in the first embodiment, and the luminance uniformity is maintained. The condition of the height of the reflecting wall 5 that can be expressed by the following expressions (2) and (3).

a + b <d Formula (2)
0 ≦ e ≦ a + b Formula (3)
In the present apparatus 1 in FIG. 12, a + b is 8 mm.

  In the present apparatus 1 of FIG. 12, the shortest distance c between the diffusion layer 4 and the cold cathode tube 2 is 18 mm. Further, as described above, the height d of the reflecting wall 5 located at both ends other than both ends, which can sufficiently maintain the luminance uniformity, is less than 14 mm. The upper limit of the height d is determined and can be expressed as in equation (4).

a + b <d <a + b + c / 3 Formula (4)
In the present apparatus 1 in FIG. 12, a + b + c / 3 is 14 mm.

  In the formula (4), the height d of the reflecting wall 5 positioned at both ends is less than (a + b + c / 3), but the shortest distance a between the bottom surface portion 3a of the reflecting plate 3 and the cold cathode tube 2, and the cold cathode tube When the shortest distance c between the diffusion layer 4 and the cold cathode tube 2 is increased without changing the size of the tube diameter b of 2, the upper limit of d can be increased as, for example, (a + b + c / 2). it can. If the shortest distance c between the diffusion layer 4 and the cold cathode tube 2 is increased, the space between the reflection wall 5 and the diffusion layer 4 is expanded, and light emitted from the cold cathode tube 2 is reflected on the reflection wall 5 of the diffusion layer 4. This is because it is difficult to generate a local dark portion because it easily enters the upper portion.

  As described above, according to the second embodiment, the uniformity of luminance is maintained by making the height e of the reflecting wall 5 located at both ends lower than the height d of the reflecting wall 5 located at both ends. The height limitation of the reflection wall 5 that can be made can be broader than when the heights of the reflection walls 5 are all the same. Therefore, the directivity and the controllability of the strip-shaped control can be further improved by increasing the height d of the reflecting wall 5 located at the positions other than both ends as in this configuration.

Embodiment 3 FIG.
In the second embodiment, the case where the height e of the reflecting wall 5 positioned at both ends is set lower than the height d of the reflecting wall 5 positioned at both ends, and the height of the reflecting wall 5 positioned at both ends is described. The case where d is the same height has been described as an example. However, the height of the reflecting wall 5 is not two-stage height of “high” and “low”, but has a plurality of heights. May be. In the third embodiment, a case will be described in which the height of the reflection walls 5 arranged in parallel to the X direction is increased as the height of the reflection wall 5 is closer to the center in the X direction.

FIG. 22 is a schematic configuration diagram showing a basic configuration of the device 1 according to the third embodiment of the present invention. In the figure, the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the third embodiment, the height of the reflecting wall 5 that partitions the light emitting areas E1 and E2, and E7 and E8 in FIG. 12 showing the basic configuration of the second embodiment is set to 5a, the light emitting areas E2 and E3, and E6 and E7. The height of the reflecting wall 5 for partitioning is 5b, the height of the reflecting wall 5 for partitioning the light emitting regions E3 and E4 and E5 and E6 is 5c, and the height of the reflecting wall 5 for partitioning the light emitting regions E4 and E5 is 5d. The reflection wall 5 near the center of the apparatus 1 is higher than the near reflection wall 5, that is, 5a <5b <5c <5d.
Here, the height of the highest reflecting wall 5 is 5d = 16 mm, which is a height not mentioned in the second embodiment.

  FIG. 23 is a graph showing a distribution of relative luminance in the apparatus 1 shown in FIG. In FIG. 23, the solid line 2301 indicates the relative luminance distribution when the height of the reflecting wall 5 is all 16 mm, and the dotted line 2302 indicates the height of the reflecting wall 5 5a = 4 mm, 5b = 8 mm, 5c = 12 mm, 5d = The relative luminance distribution in the case of 16 mm is shown. Since the vertical axis, the horizontal axis, the measurement location of the luminance, and the method of obtaining the relative luminance are the same as those in FIG. Here, all the cold cathode fluorescent lamps 2 are turned on.

In FIG. 23, when the heights of the reflection walls 5 are all 16 mm, the relative luminance is reduced at the left end of the diffusion layer 4 and the upper portions of the reflection walls 5. As a result, the step of the relative luminance distribution curve is conspicuous. For this reason, a dark part is generated at the left end of the diffusion layer 4 and the upper part of the reflection wall 5, and there is a high possibility that luminance unevenness is observed.
On the other hand, when the height of the reflecting wall 5 is gradually changed like 5a, 5b, 5c and 5d, the left end of the diffusing layer 4 and the reflection are compared with the case where the height of the reflecting wall 5 is all 16 mm. The decrease in relative luminance of the wall 5 portion, particularly the portions of the reflecting wall 5 between the light emitting regions E5 and E6, E6 and E7, and E7 and E8 is improved, and the curve of relative luminance is smoothed. In addition, in the light emitting areas E1 to E4, the relative luminance is lower overall as compared with the case where all the reflecting walls 5 are 16 mm, but there is no decrease in the relative luminance in the upper part of the reflecting walls 5. Is smooth. Therefore, when the height of the reflecting wall 5 is gradually changed, uneven brightness is not observed.

  Thus, if the height of the reflecting wall 5 is gradually increased from both ends toward the center of the apparatus 1, the height of the reflecting wall 5 located at the center of the apparatus is maintained while maintaining the uniformity of luminance. 5d can be made higher than the height d of the reflecting wall 5 located at the positions other than both ends in the second embodiment.

Next, the improvement in contrast will be described with reference to FIG.
FIG. 24 shows the relative values when the height of the reflecting wall 5 is 8 mm and when the height of the reflecting wall 5 is 5a = 4 mm, 5b = 8 mm, 5c = 12 mm, and 5d = 16 mm as shown in FIG. 25 is a graph showing a luminance distribution, in which a solid line 2401 in FIG. 24 indicates the relative luminance distribution in the former case, and a dotted line in 2402 indicates the relative luminance distribution in the latter case. The vertical axis, the horizontal axis, the measurement location of luminance, and the method of obtaining relative luminance are the same as those in FIG. In the light emitting region to be turned on or off, in the third embodiment, E1, E3, E5, and E7 are turned off, and E2, E4, E6, and E8 are turned on.

  In FIG. 24, when the height of the reflecting wall 5 is 5a <5b <5c <5d as in 2402, the light emitting regions E1 to E3 and the height of the reflecting wall 5 are all 8 mm, and Although there is no significant difference in the relative luminance of E6 to E8, the relative luminance difference is large in the central portion of the diffusion layer 4, that is, the light emitting regions E3 to E6. This is because the height 5d of the central portion of the reflecting wall 5 is made the highest, and the effect of improving the contrast by increasing the height of the reflecting wall 5 at the central portion of the diffusion layer 4 appears greatly. is there.

  As described above, as shown in the third embodiment, the strip-shaped control is performed while maintaining the uniformity of luminance by increasing the height of the reflection wall 5 from both ends toward the center of the apparatus 1. The controllability can be further improved. In particular, it is possible to obtain a direct type backlight device having a good contrast at the center of the screen display device.

  In the above description, the case where the height 5d of the reflecting wall 5 located at the center of the apparatus 1 is set to the highest height has been described. However, even if the height of the reflecting walls 5c and 5d on the center side of the apparatus 1 is made equal. good. In this way, the high contrast region is widened, and the controllability of the belt-like control at the center of the diffusion layer 4 is further improved. In that case, it is necessary to devise such as reducing the height of the reflecting wall 5 other than 5c and 5d, such as 5a and 5b.

Embodiment 4
In the first to third embodiments, as shown in FIGS. 1, 12, and 22, the planar reflecting wall 5 is described as standing upright at equal intervals on the bottom surface portion 3 a of the reflecting plate 3. The interval between them may be changed, or the reflection wall 5 may be installed obliquely.

  FIG. 25 is a schematic configuration diagram showing an example of a basic configuration of the device 1 according to the fourth embodiment of the present invention. In the figure, the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the fourth embodiment, light emitted from the cold-cathode tube 2 has an inverted V-shaped cross section instead of the flat reflecting wall 5 installed upright in FIG. 12 showing the basic configuration of the second embodiment. A reflecting member extending in the Y direction, the surface of which is reflected, is used as the reflecting wall 5 and is installed on the bottom surface portion 3 a of the reflecting plate 3. Similar to the second embodiment, the height e of the two reflecting walls 5 positioned at both ends is lower than the height d of the reflecting walls 5 positioned at both ends.

  In this case, as shown in the second embodiment, the angle and the length of the reflecting wall 5 installed obliquely with respect to the bottom surface portion 3a of the reflecting plate 3 are changed while maintaining the uniformity of luminance, thereby controlling the directivity and the band shape. It is possible to improve the controllability.

  Further, as shown in the first and third embodiments, the heights of these reflection walls 5 may all be the same, or may be changed depending on the positions where the reflection walls 5 are installed. In that case, as shown in the first embodiment or the third embodiment, the angle and length of the reflecting wall 5 are changed while maintaining the uniformity of the brightness, and the directivity and the controllability of the strip-shaped control are further improved. Can be planned.

  As described above, according to the fourth embodiment, the directivity and the controllability of the strip-like control as described in the first to third embodiments are improved, and the shape of the reflecting wall 5 is further changed to control the optical path. By performing the above, it is possible to obtain a direct type backlight device with better directivity.

  By the way, in the above description, the diffusion layer 4 in the present apparatus 1 is described as a case where two diffusion sheets are stacked on the light diffusion plate, but the diffusion layer 4 may have any configuration. For example, a condensing type diffusion sheet may be provided on the reflection layer 3 side of the diffusion layer 4, or the light diffusion plate may be used alone. Further, a configuration using a light diffusion plate and a prism sheet having a light condensing effect on the observer side may be used.

  Moreover, although the case where two cold cathode tubes 2 are used as one unit and the same luminance control is performed for each unit has been described, the cold cathode tubes 2 may be subjected to band-like control one by one. This makes it possible to have a finer luminance distribution than when the cold cathode fluorescent lamps 2 are controlled every two.

  Further, the number of the cold cathode tubes 2 is three or more to be one unit, the number of the cold cathode tubes 2 in one unit is varied depending on the position in the apparatus 1, or the number of the cold cathode tubes 2 is changed in accordance with the light emitting region. The number of cold cathode fluorescent lamps 2 may be arbitrarily changed. Further, the height of the reflecting wall 5 may be changed in accordance with the position and area of the light emitting region. In this way, a finer direct type backlight device can be obtained by performing different brightness control depending on the location of the display screen.

  Furthermore, a direct type backlight device may be configured with a U-shaped cold cathode tube 2 instead of the straight tube cold cathode tube 2 as a cylindrical light source. By doing in this way, when this apparatus 1 is enlarged, a favorable image with little brightness nonuniformity is realizable.

  Also, here, the case where the present invention is applied to a backlight device using a cylindrical light source has been described, but a backlight in which LED light sources are linearly arranged in parallel is simulated by arranging the cylindrical light sources in parallel. You may apply to a light apparatus etc.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows this apparatus which concerns on Embodiment 1 of this invention. It is an enlarged view which shows an optical path in Embodiment 1 of this invention. It is an enlarged view which shows an optical path in Embodiment 1 of this invention. It is a graph for demonstrating general luminance distribution in Embodiment 1 of this invention. It is a graph which shows the luminance distribution of this apparatus concerning Embodiment 1 of this invention. It is a graph which shows the half value width of the brightness | luminance of this apparatus which concerns on Embodiment 1 of this invention. It is a graph for demonstrating the contrast in Embodiment 1 of this invention. It is a graph which shows the contrast of this apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the image of the contrast observed on the diffusion layer 4 in Embodiment 1 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 1 of this invention. It is a figure which shows the image of the uniformity of the brightness | luminance observed on the diffusion layer 4 in Embodiment 1 of this invention. It is a schematic block diagram which shows this apparatus which concerns on Embodiment 2 of this invention. It is an enlarged view which shows an optical path in Embodiment 2 of this invention. It is an enlarged view which shows an optical path in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a graph for demonstrating the contrast in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 2 of this invention. It is a schematic block diagram which shows this apparatus which concerns on Embodiment 3 of this invention. It is a graph for demonstrating the uniformity of the brightness | luminance in Embodiment 3 of this invention. It is a graph for demonstrating the contrast in Embodiment 3 of this invention. It is a schematic block diagram which shows an example of this apparatus which concerns on Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Direct type backlight apparatus 2 Cold cathode tube 3a Bottom part of reflecting plate 4 Diffusion layer 5 Reflecting wall

Claims (10)

A direct-type backlight device in which a plurality of cylindrical light sources capable of independently adjusting brightness are arranged in parallel between a diffusion layer and a reflector,
A reflecting wall having a height in the normal direction from the reflecting plate is disposed on the reflecting plate between the cylindrical light sources,
A direct type backlight device characterized in that, among the plurality of reflection walls, the height of the reflection wall located at both ends is lower than that of the reflection wall located outside the both ends.   2. The direct type backlight device according to claim 1, wherein the height of the reflecting walls located at both ends is equal to or less than a sum of a shortest distance between the reflecting plate and the cylindrical light source and a tube diameter of the cylindrical light source. A direct-type backlight device in which a plurality of cylindrical light sources capable of independently adjusting brightness are arranged in parallel between a diffusion layer and a reflector,
A reflecting wall having a height in the normal direction from the reflecting plate is disposed on the reflecting plate between the cylindrical light sources,
A direct type backlight device characterized in that the height of all the reflecting walls is equal to or less than the sum of the shortest distance between the reflecting plate and the cylindrical light source and the tube diameter of the cylindrical light source.   The direct-type backlight device according to claim 2, wherein the height of the reflecting wall located at other than both ends is higher than the sum of the shortest distance between the reflecting plate and the cylindrical light source and the tube diameter of the cylindrical light source. The shortest distance between the reflector and the cylindrical light source is a,
The tube diameter of the cylindrical light source is b,
The shortest distance between the diffusion layer and the cylindrical light source is c,
If the height of the reflection wall located at both ends is d,
The direct-type backlight device according to claim 4, wherein d <a + b + c / 3 is satisfied.   4. The height of the reflection wall is increased as the positions where the plurality of reflection walls are arranged from both ends toward the central portion. 5. Direct type backlight device.   The cylindrical light source which adjoins continuously and performs the same brightness | luminance adjustment is made into 1 unit, The reflective wall was provided between the said units, The direct bottom of any one of Claims 1-6 characterized by the above-mentioned. Type backlight device.   The direct type backlight device according to any one of claims 1 to 6, wherein the cylindrical light source is a straight tube type cold cathode tube.   The direct type backlight device according to any one of claims 1 to 6, wherein the cylindrical light source is a U-shaped cold cathode tube. A liquid crystal panel is arranged in the direct type backlight device according to any one of claims 1 to 9, and the direct type backlight device is disposed between the liquid crystal panel and a reflector of the direct type backlight device. A thin display device characterized in that a diffusion layer is located.

Images