WO1997045673A1 - Illuminator - Google Patents

Abstract

An illuminator having a small unevenness of luminance, a high luminance and a wide range of visual angle is obtained. In a downwardly directed illuminator comprising a fluorescent tube as a light source, and a reflector for reflecting the light from the fluorescent tube in the frontward direction thereof, a first prism plate is provided in front of the fluorescent tube with a clearance left therebetween, a second prism plate in front of the first prism plate with a clearance left therebetween, and a diffusion member in front of the second prism plate with a clearance left therebetween.

Description

 Description Lighting equipment Technical field

 INDUSTRIAL APPLICABILITY The present invention is widely used for a liquid crystal display device used in a portable liquid crystal television receiver, a portable liquid crystal monitor, a notebook computer, a palm top computer, and the like. The present invention relates to a lighting device for illuminating a liquid crystal panel or the like. More specifically, the present invention relates to an illumination device called a direct illumination device in which a fluorescent tube as a light source is disposed below an object to be illuminated. Background art

 A liquid crystal display device that displays images using a liquid crystal panel is lighter, smaller, thinner, and more easily consumes less power than a display device that displays images using a conventional brown tube. It is used in various fields such as monitors, television receivers, and multimedia devices. Most of such portable liquid crystal display devices are passive (do not emit light) and have a fluorescent tube or EL inside the liquid crystal display device in order to make the screen of the display device brighter and clarify the displayed image. In many cases, a configuration incorporating a lighting device that uses an LED is used.

 The above-mentioned lighting device is described in detail in Japanese Patent Application Laid-Open No. 5-81909, and the liquid crystal display device incorporating the above-mentioned lighting device is described in detail in Japanese Patent Application Laid-Open No. 7-218157. I have.

Japanese Patent Application Laid-Open No. Hei 5-81,099 discloses that a reflector for reflecting light traveling backward from a light source to the front of the light source is disposed behind the light source, and diffuses light from the light source in front of the light source. A diffusion member is provided, and a restriction member for restricting diffused light is disposed in front of the diffusion member. An illuminating device is disclosed in which a surface (viewer side surface) is provided with saw-toothed irregularities.

 In the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 7-281157, the exterior of the liquid crystal display device includes a lower frame, an upper frame, and a windshield. A circuit board is provided in the lower frame, and a reflection member for reflecting light of the fluorescent tube toward the liquid crystal panel is soldered on the circuit board. A fluorescent tube, which is a light source, is provided in the reflecting member, and a diffusion member housed in a panel support frame is provided above the fluorescent tube, and drives and controls the liquid crystal panel above the diffusion member. Liquid crystal panel to which a flexible circuit board is connected. Above the liquid crystal panel, a windshield is mounted on the upper frame to protect the liquid crystal panel and prevent dust from adhering to the liquid crystal panel surface.

 The lighting device that illuminates the liquid crystal panel is located behind the liquid crystal panel when viewed from the viewer in order to clarify the image. The above two publications are illumination systems called direct illumination systems, in which a light source is disposed almost directly below a liquid crystal panel. As another illumination method, there is a side-light-type illumination device in which a light source is arranged on a side of a liquid crystal panel, and a light guide member for guiding light of the light source is arranged almost directly below the liquid crystal panel. TECHNICAL FIELD The present invention relates to a direct lighting device.

Summary of the Invention

 Looking at the luminance characteristics of the conventional lighting device, there is a problem that the luminance is uneven and the luminance is low, and improvement has been desired.

 Therefore, an object of the present invention is to obtain an illumination device having less luminance unevenness and higher luminance than the conventional illumination device.

In order to achieve the above object, the present invention has at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube. In a direct-type lighting device, a prism plate is provided in front of the fluorescent tube with a first predetermined gap provided, and a second predetermined plate is disposed in front of the prism plate. A diffusion member is provided with a gap, and when viewed from the front of the prism plate, an image obtained by shifting the fluorescent tube in a direction orthogonal to the extension direction of the ridge line of the prism is formed by the prism. The first predetermined gap is set so as to be formed on a vibration plate.

 Also, the present invention provides a first prism plate provided with a first predetermined gap in front of the fluorescent tube, and a second predetermined plate in front of the first prism plate. When the second prism plate is disposed with a gap therebetween, and viewed from the front of the first prism plate, it is orthogonal to the direction in which the ridge line of the first prism extends with respect to the fluorescent tube. An image shifted in the direction is formed on the first prism plate. Similarly, when viewed from the front of the second prism plate, the image of the fluorescent tube is compared with the second prism plate. The first and second predetermined gaps are set so that an image shifted in a direction orthogonal to the extension direction of the ridge line of the prism is formed on the second prism plate.

 Further, according to the present invention, the first prism plate is provided with a first predetermined gap in front of the fluorescent tube, and the second predetermined gap is arranged in front of the first prism plate. The first prism is fixed, the second prism is rotated, and the second prism is oriented with respect to the extension direction of the ridge line of the first prism. The angle formed by the extension direction of the ridge line is changed, and a method for obtaining the angle at which the luminance unevenness is minimized when viewed from above the prism plate is obtained. The invention's effect

As described above, according to the present invention, the predetermined gaps are provided between the fluorescent tube and the prism plate, between the prism plates, and between the prism plate and the diffusion plate. For example, an illumination device having less luminance unevenness and higher luminance than a conventional illumination device can be obtained. In addition, a predetermined gap is provided between the fluorescent tube and the prism plate, between the prism plates, and between the prism plate and the diffusion plate, so that the components have a sufficiently wide gap. Therefore, the temperature rise due to the heat generated by the fluorescent tube is suppressed, the unevenness of the temperature distribution is reduced, and the display unevenness of the liquid crystal panel and the deterioration of the reliability of the liquid crystal caused by the heat generated by the fluorescent tube can be prevented. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a sectional view of a liquid crystal display device using the lighting device of the present invention. FIG. 2 is an exploded perspective view of a main part of the embodiment of the lighting device of the present invention. FIG. 3 is an explanatory diagram of the lighting device of the present invention.

 FIG. 4 is an explanatory diagram showing an embodiment of the illumination device of the present invention when the extension direction of the ridge line of the prism plate is parallel to the extension direction of the fluorescent tube.

 FIG. 5 is an explanatory diagram of the lighting device of the present invention.

 FIG. 6 is an explanatory diagram showing an embodiment of the lighting device of the present invention when the direction of extension of the ridge line of the prism plate is orthogonal to the direction of extension of the fluorescent tube.

 FIG. 7 is an explanatory diagram showing an embodiment of the lighting device of the present invention when two prism plates are used.

 FIG. 8 is a diagram showing a relative positional relationship between the two prisms that minimizes luminance unevenness when both are triangular prism plates.

 FIG. 9 is a diagram showing a relative positional relationship between the two prisms that minimizes luminance unevenness when both of the prisms are waveform prism plates.

 FIG. 10 is a diagram showing a configuration in which one is a triangular prism plate and the other is a waveform prism plate.

Figure 11 shows one of them as a waveform prism and the other as a triangle prism. FIG. 3 is a view showing a configuration as a plate.

 FIG. 12 is an explanatory diagram for creating a viewing angle vs. luminance distribution graph.

 Fig. 13 is a graph of the viewing angle versus the brightness distribution on the lighting device when the viewing angle is changed in the vertical direction.

 Fig. 14 is a graph of the viewing angle versus the brightness distribution on the lighting device when the viewing angle is changed in the horizontal direction.

 FIG. 15 is a diagram showing distributions of luminance and temperature of the lighting device of the present invention.

 FIG. 16 is an exploded perspective view of a conventional sidelight-type lighting device. Detailed description of the invention

 Prior to describing the present invention, a prior art will be described.

 FIG. 16 is an exploded perspective view of a side lighting type lighting device showing an example of the prior art, and also shows a liquid crystal panel which is a passive type display panel provided on the lighting device.

In FIG. 16, a prism plate 110 is provided below the liquid crystal panel 200. The ridge plate 110 has a plurality of ridges formed in parallel at an angle of 45 degrees with respect to the sides of the prim plate. The surface of the prism plate 110 opposite to the surface on which the prism was formed was a flat flat surface, a flat surface having minute irregularities, or a glass surface treatment. It is a plane. Below the prism plate 110, a diffusion plate 130 for diffusing light to reduce luminance unevenness is provided. A light guide plate 160 is provided below the diffusion plate 130, and an L-shaped fluorescent tube 150 is provided on the side of the light guide plate 160. A fluorescent tube reflector plate 152 is provided so as to cover the L-shaped fluorescent tube, and a lower reflector plate 16 is provided below the light guide 160. O

 Most of the light generated from the L-shaped fluorescent tube 150 is guided to the light guide plate by the fluorescent tube reflector plate 152, propagates in the light guide 扳, and emits light from the entire light guide plate to the diffuser plate. I do. At this time, the lower reflector effectively acts for light propagation of the light guide plate and for emitting light toward the diffuser plate. Light emitted from the light guide plate 160 enters the diffuser plate 130 and is diffused to suppress luminance unevenness, which is uneven light. The substantially uniform light emitted from the diffusion plate 130 is controlled by the prism plate 110 so as not to diffuse in an unnecessary direction for viewing the image. The controlled light enters the liquid crystal panel 200 and exits from the liquid crystal panel 200 as light that forms an image. Figure 16 shows all the components separated, but in the actual product they are placed one on top of the other.

 FIG. 1 is a cross-sectional view of a liquid crystal display device using the lighting device of the present invention. The lighting device of the present invention and a liquid crystal display device using the lighting device will be described with reference to FIG.

 In FIG. 1, an outer frame 80 as an exterior of the liquid crystal display device has a concave portion in which a fluorescent tube 50 is provided, and a reflector 60 having a reflecting portion 61 for reflecting light is provided with an outer frame 80. In the recess. The reflector 60 is provided with a fluorescent tube 50. The fluorescent tube 50 used in the embodiment of the present invention is a W-shaped fluorescent tube, but may be a straight tube type, a U-shaped, an N-shaped, an L-shaped fluorescent tube, or the like. In the embodiment of the present invention, the reflector 60 is formed of a white material as the reflection portion 61 of the concave portion in the reflector 60, and the reflection process by another member is not performed for the reflection portion 61. Was. However, a film-like reflecting member may be provided below the fluorescent tube or beside and below the fluorescent tube, or a reflecting material may be provided on the reflecting portion 61 by plating or vapor deposition.

A first prism plate 10 is provided above the fluorescent tube 50 with a gap 12 therebetween. At this time, the width of the gap 12 is set within the fluorescent tube 50 in this embodiment. The diameter is almost equal.

 Further, a gap 22 is provided above the first prism plate 10, and a second prism plate 20 is provided. At this time, the width of the gap 22 was made substantially equal to the inner diameter of the light tube 50 in the present embodiment.

 Further, a diffusion member 30 is provided above the second prism plate 20 with a gap 32 provided. At this time, the width of the gap 32 was made substantially equal to the inner diameter of the fluorescent tube 50 in the present embodiment.

 Further, a liquid crystal panel 200 was provided with a gap (arbitrary gap) provided above the diffusion member 30. In FIG. 1, an STN liquid crystal panel is used. Two liquid crystal panels are installed, one of which is a drive panel and the other is a correction panel.

 As described above, in order to obtain the gaps 12, 22, and 32, the receiving portion is disposed at the upper end of the reflector 60, and the gap members 40, 42 are further provided.

 FIG. 2 is an exploded perspective view of a main part of an embodiment of the lighting device of the present invention. In FIG. 2, a not-shown reflector shown in FIG. 1 is provided below and beside a fluorescent tube 50 as a light source. The fluorescent tube 50 is a W-shaped tube. A first prism plate 10 is provided above the fluorescent tube 50 with a predetermined gap 12 provided therebetween. On the upper surface of the first prism plate 10, a prism having a ridge angle of approximately 90 degrees and a plurality of ridge lines provided in parallel is provided. The extension direction 13 of the plurality of ridge lines 11 on the upper surface of the first prism plate 10 is formed in parallel with the extension direction 53 of the fluorescent tube 50.

Further, a second prism plate 20 is disposed above the first prism plate 10 with a predetermined gap 22 provided therebetween. On the upper surface of the second prism plate 20, there is disposed a prism having a ridge angle of approximately 90 degrees and a plurality of ridge lines provided in parallel. Of the ridge line 2 1 on the upper surface of the second prism plate 20 The extension direction 23 is formed in a direction orthogonal to the fluorescent tube extension direction 53 of the fluorescent tube 50.

 Further, a diffusion member 30 for diffusing light is provided above the second prism plate 20 with a predetermined gap 32 provided.

 When used for a liquid crystal display device, a liquid crystal panel is provided with an appropriate gap above the diffusion member, but is omitted in FIG.

 Next, the operation of the present invention will be described with reference to the explanatory diagrams and embodiments of the present invention shown in FIGS.

 FIG. 3 is a diagram for explaining the operation of the present invention. In FIG. 3, a fluorescent tube 50 having an inner diameter X extends from the front to the back, and a prism plate 10 is provided at the top of the fluorescent tube 50 with a gap X equal to the inner diameter of the fluorescent tube. ing. A plurality of ridge lines 11 are formed on the prism plate 10 in parallel with the direction in which the fluorescent tubes 50 extend. When the lighting device thus arranged is viewed from above the prism plate 10, two fluorescent tube images 51 appear at positions shifted x / 2 from the fluorescent tube 50.

 For example, if the inner diameter of the fluorescent tube 50 is 5 mm, and the gap between the fluorescent tube 50 and the prism plate 10 is also 5 mm, when the lighting device is viewed from above the prism 10 plate, the fluorescent tube 50 The images 51 of the two fluorescent tubes appear at positions shifted by 2.5 mm from.

 FIG. 4 is an embodiment of the present invention using the above operation, and is an embodiment of the lighting device of the present invention in the case where the extending direction of the ridge line of the prism plate is parallel to the extending direction of the fluorescent tube.

 In FIG. 4, a brim plate 10 is provided above a fluorescent tube 50 with a gap having a predetermined size. The ridge line 11 of the prism plate 10 is formed parallel to the direction in which the fluorescent tubes 50 extend.

FIG. 4 (1) is a diagram of the above configuration as viewed from above, in which the fluorescent tube 50 is indicated by a dotted line, and the ridge line 11 indicated by a solid line is the position of the fluorescent tube 50. It is parallel to the extension direction.

 FIG. 4 (2) shows an image of the fluorescent tube 50 when viewed from above the prism plate 10. When the lighting device constructed as shown in Fig. 4 (1) is viewed from above the prism board 0, an image of the fluorescent tube appears at a position shifted by X in a direction orthogonal to the extension direction of the fluorescent tube 50. . That is, a point e, which is the image 51 of the point E, is observed at a position vertically shifted X from the point E on the fluorescent tube 50. In the case of Fig. 4 (2), if the inside diameter of the fluorescent tube is 5 mm (outside diameter is about 6 mm) and the gap between the fluorescent tube 50 and the prism plate 10 is about 5 mm, X is about 2 mm. . 5 mm. As shown in FIG. 4 (2), an image of the fluorescent tube appears at a position shifted up and down by approximately half the inner diameter of the fluorescent tube 50 (in this case, 2.5 mm). Therefore, luminance unevenness can be reduced.

In this case, as shown in FIG. 4 (2), an image of the fluorescent tube appears at a position shifted up and down by approximately 1 Z 2 of the inner diameter of the fluorescent tube 50. That is, if the ratio of the width of the gap between the fluorescent tube 50 and the prism plate 10 to the inner diameter of the fluorescent tube 50 is 1, the image of the fluorescent tube 50 has a length that is half the inner diameter of the fluorescent tube 50. Only the shift appears. Therefore, the shift length can be adjusted according to the shape of the fluorescent tube in order to reduce the uneven brightness. Although the case where the ratio of the width of the gap between the fluorescent tube 50 and the prism plate 10 to the inner diameter of the fluorescent tube 50 is 1 has been described, this ratio is not necessarily required to be 1. It can be appropriately adjusted depending on the shape of the fluorescent tube. However, when the specific power becomes smaller than 1, that is, when the width of the gap between the fluorescent tube 50 and the prism plate 10 becomes smaller than the inner diameter of the fluorescent tube 50, an image of the fluorescent tube 50 is formed. It overlaps with each other and the brightness unevenness increases. Therefore, it is preferable that the width of the gap be approximately equal to or larger than the inner diameter of the pipe. Even when the ratio is 1 or more, it is preferable that the images of the fluorescent tubes are not overlapped. As described above, a plurality of images of the fluorescent tube are shifted up and down and appear, so that an illumination device with less uneven brightness can be obtained. In this case, the luminance at the point E is 18% lower than the luminance of the tube surface of the fluorescent tube 50.

 Note that the reflector 60 in FIG. 1 is omitted in FIG. Further, in the configuration of FIG. 4, if a lighting device is provided by providing a diffusion member with a gap provided above the prism plate 10, a lighting device with reduced brightness but further reduced brightness unevenness can be obtained.

 FIG. 5 is another diagram for explaining the operation of the present invention. In FIG. 5, a fluorescent tube 50 having an inner diameter X (for example, 5 mm) extends left and right, and a prism X 20 is provided above the fluorescent tube 50 with a gap X therebetween. A plurality of ridge lines 21 are formed on the prism plate 20 in a direction perpendicular to the direction in which the fluorescent tubes 50 extend (the left-right direction in the figure). When the lighting device thus arranged is viewed from above the prism, images of the two fluorescent tubes appear at positions shifted from the fluorescent tubes 50 to the left and right of xZ2. That is, a point e, which is an image of the point E, is viewed at a position shifted xZ 2 in the left-right direction of the point E on the fluorescent tube 50.

 FIG. 6 is an embodiment of the present invention using the above operation, and is an explanatory view showing an embodiment of the present lighting device in the case where the ridge of the prism plate extends in a direction perpendicular to the extending direction of the fluorescent tube. . In FIG. 6 (1), a prism plate 20 is provided above a fluorescent tube 50 indicated by a dotted line with a predetermined gap X provided. The ridge line 21 of the prism plate 20 shown by a solid line is formed in a direction 23 orthogonal to the extending direction of the fluorescent tube 50.

FIG. 6 (2) is a diagram showing an image of the fluorescent tube 50 when viewed from above the prism plate 20. When the lighting device configured as shown in FIG. 6 (1) is viewed from above the prism # 20, an image of the fluorescent tube appears at a position shifted by approximately X with respect to the extending direction of the fluorescent tube 50. That is, above the fluorescent tube 50 The point e, which is the image 52 of the point E, is observed at a position shifted X in the left-right direction from the point E having the point. FIG. 6 (2) shows the case where the inner diameter of the fluorescent tube is equal to the width of the gap between the fluorescent tube 50 and the prism plate 10, and X is half the inner diameter of the fluorescent tube. Therefore, an image 52 of the fluorescent tube appears at a position shifted to the left and right by substantially half of the inner diameter of the fluorescent tube 50.

 Since an image of the fluorescent tube appears as described above, a lighting device with high luminance can be obtained. In this case, the luminance at the point E is higher by 20% than the luminance of the fluorescent lamp 50.

 The reflector 60 in FIG. 1 is omitted in FIG. Further, in the configuration shown in FIG. 6, if a diffusion member is provided with a gap provided above the prism plate 10 to form an illumination device, an illumination device with reduced luminance but small luminance unevenness can be obtained.

 In FIG. 7, as shown in FIG. 2, the prism plate 10 is provided with a gap from the fluorescent tube 50, and the prism plate 20 is provided with a gap above the prism plate 10. Is arranged.

 FIG. 7 (1) is a diagram of the lighting device configured as described above, as viewed from above. The fluorescent tube 50 is shown by a dotted line, and the ridge lines 11 and 21 of the prism plates 10 and 20 are shown by solid lines. The extension direction 13 of the ridge line 11 of the prism plate 10 is formed parallel to the extension direction of the fluorescent tube 50. The extension direction 23 of the ridge line 21 of the prism plate 20 is formed in a direction orthogonal to the fluorescent tube extension direction of the fluorescent tube 50.

FIG. 7 (2) is a diagram showing a state of the brightness of the fluorescent tube 50 when viewed from above the second prism plate 20. When the lighting device configured as shown in Fig. 7 (1) is viewed from above the prism plate 20, the fluorescent tube is located in a direction orthogonal to the extension direction of the fluorescent tube 50, that is, a position shifted by X in the vertical direction. The image 54 appears. In this figure, with respect to the inner diameter of the fluorescent tube 50, Assuming that the ratio of the width of the gap between the fluorescent tube 50 and the prism plate 10 is set to a predetermined value and the ridge angle of the prism is approximately 90 degrees, the upper part of the fluorescent tube 50 in FIG. A point e, which is the image 54 of the point E, is generated at a position shifted by X in the vertical direction (in the figure) of the point E with respect to the point E. Further, the image of the point E is shifted by Y in the left and right direction (in the figure) of the point E with respect to the point E on the fluorescent tube 50 by the second prism plate 20. There is a point e which is 5 4. As a result, as shown in FIG. 7 (2), point e, which is an image at four positions, is obtained. The values of X and Y vary the ratio of the width of the gap between the fluorescent tube 50 and the prism plates 10 and 20 to the size of the inner diameter of the fluorescent tube 50 as described in FIG. Can be changed by

 In this case, the brightness at the point E is 3.5% lower than the brightness of the fluorescent tube 50, and the brightness unevenness is greatly improved.

 Note that the reflector 60 in FIG. 1 is omitted in FIG. Further, in the configuration shown in FIG. 7, if a diffusion member is provided with a gap provided above the prism plate 20 to provide an illumination device, an illumination device with reduced luminance but reduced luminance unevenness can be obtained.

 In the above embodiment, a prism plate in which a triangular prism having an apex angle of 90 degrees is arranged on one side of the plate is used, but the top and the concave portion (bottom) of the prism are rounded. It is also possible to use a prism plate or a corrugated prism plate in which the top of a convex semicircle and the concave portion (bottom) of a concave semicircle are connected.

 In addition, when two prism boards are used one on top of the other, a triangle prism board is used for the two prism boards, a wave prism board is used for the two prism boards, and a triangle prism board is used for the two prism boards. Alternatively, any of the configurations in which the other one is a corrugated prism plate may be used.

Next, as shown in Fig. 2, when both of them are triangular prism plates The following describes the relative positional relationship of the prism that optimizes luminance unevenness. First, the extension direction 13 of the prism ridge line 11 of the prism plate 10 on the fluorescent tube side (the lower prism plate) is made to coincide with the extension direction 53 of the fluorescent tube 50. Next, the extension direction 23 of the prism ridge 21 of the upper prism plate 20 is initially arranged so as to be orthogonal to the extension direction of the fluorescent tube (as shown in FIG. 2). Next, while observing the brightness unevenness state of the lighting device from above the upper prism plate, the extension direction 23 of the prism ridge line 21 of the upper prism plate 20 is changed to the lower prism plate 1. Rotate in a plane with respect to the extension direction 1 3 of the ridge line 1 1 of 0. Then, the angle formed by the extension direction 23 of the prism ridge line 21 of the upper prism plate 20 with respect to the extension direction 23 of the prism ridge line 11 of the lower prism plate 10 is adjusted. The angle that minimizes unevenness was determined. As a result, the extension direction 23 of the upper ridge plate 20 of the upper prism plate 20 is 45 ° ± 10 ° with respect to the extension direction 13 of the prism ridge line 11 of the lower prism plate 10. Occasionally, luminance unevenness was minimized.

 Figure 8 shows the relative positional relationship between prisms that minimizes luminance unevenness when both are triangular prism plates, that is, the angle between the ridge lines of the two prism plates is 45 ° ± 10 ° ° is shown.

In addition, the relative positional relationship between the prisms that optimizes the luminance unevenness when both of the structures in FIG. 2 are waveform prism plates is described. The prism plate 10 is arranged so that the extension direction 13 of the ridge line 11 is parallel to the extension direction 53 of the fluorescent tube 50, and the extension direction 2 of the ridge line 21 of the prism plate 20 is arranged. 3 is arranged so as to be orthogonal to the extension direction of the fluorescent tube 50. Then, the prism plate 20 was rotated in the same manner as described above, and the angle at which the luminance unevenness was minimized was obtained. As a result, when the extension direction 23 of the ridge line 21 of the prism 20 plate is the same as the extension direction 13 of the ridge line 11 of the prism 10 plate, that is, when it is substantially parallel. The luminance unevenness was minimized. Fig. 9 shows the relative positional relationship between prisms that minimizes luminance unevenness when both of them are wave-shaped prism plates, that is, the configuration in which the angle between the ridge lines of the two prism plates is 0 °. It is shown.

 Figures 10 and 11 show a configuration in which one is a triangular prism plate and the other is a waveform prism plate.

 FIGS. 13 and 14 are graphs of the viewing angle versus the luminance distribution on the top surface of the lighting device. Graph b shows the viewing angle (degree) of the lighting device when the liquid crystal panel 200 is removed from the liquid crystal display device using the lighting device of the present invention shown in FIG. 1 and the lighting device is viewed from above the diffusion member 30. This is a luminance (Cd.Znf) characteristic graph (measured with a luminance meter: MIN 0 LTA: CS—100). In FIG. 1, the gap 12, the gap 22, and the gap 32 are approximately 5 mm, and the inner diameter of the fluorescent tube is approximately 5 mm. Graph a shows the viewing angle (degrees) versus luminance of the lighting device when the liquid crystal panel 200 is removed and the lighting device is viewed from above the prism plate 110 in Fig. 16 showing an example of the prior art. (C d / nf) Characteristic graph (measured with a luminance meter: MINOLTA: CS-100).

 As shown in Fig. 12, the graph in Fig. 13 passes through the center of the plate surface of the lighting device top 70 and moves the top plate surface in the Y direction (vertical direction with respect to the liquid crystal image) and the X When an axis is drawn in the left-right direction with respect to the image, a normal Z is set at the intersection of the X-axis and the Y-axis, and the viewing angle is shifted vertically in the Y-direction (luminance measurement). FIG. 7 shows the change in luminance of the lighting device with respect to the swing angle when the container is moved. In addition, the graph of FIG. 14 shows the lighting device with respect to the swing angle when the viewing angle is swung in the left and right direction, that is, the X direction with respect to the normal line shown in FIG. 12 (when the luminance measuring device is moved). Of the luminance of the image.

From the graphs in Fig. 13 and Fig. 14, when the viewing angle is changed in the vertical (Y) direction, the luminance value of the lighting device with respect to the swing angle, and the horizontal (X) When the viewing angle is changed, it can be said that the brightness value of the lighting device with respect to the swing angle is higher in the graph b according to the present lighting device than in the graph a according to the conventional lighting device. . Also, the value of the luminance on the normal line is shown in FIGS. 13 and 14, and the graph b shows a value twice that of the graph a.

 Graph b according to the lighting device of the present invention is when the tube current of the fluorescent tube is 8 mA, and graph a according to the conventional lighting device is when the tube current of the fluorescent tube is 5 mA. . However, it can be said that the lighting device of the present invention is superior to the conventional lighting device even when the difference in tube current is taken into account.

 FIG. 15 shows the luminance and temperature distributions of the lighting device of the present invention (measured from the diffuser plate with the panel removed).

Related to luminance unevenness is the difference of each part in the luminance of the plate surface of the lighting device top, the maximum luminance was 1 0 4 0 0 (C d Z m 2), minimum brightness 8 2 8 0 (C d / m ² ), and the luminance unevenness of the lighting device of the present invention is only 20%.

Next, the effect of temperature rise due to the heat generated by the fluorescent tube, which affects the liquid crystal and affects the image display quality, is examined. In the configuration of FIG. 1 showing a liquid crystal display device using the lighting device of the present invention, the temperature on the lower polarizing plate of the liquid crystal panel 200 facing the diffusion member 30 is measured to increase the temperature by the lighting device. The maximum temperature rise of the lower polarizer at an ambient temperature of 40 ° C is approximately 15 ° C. Even if the maximum ambient temperature of the general use environment of 45 ° C is considered, this temperature rise has a margin of approximately 5 ° C compared to the temperature at which the liquid crystal of the general specification causes a phase change. The conditions at this time were as follows: in the configuration of Fig. 1, the gap 12, the gap 22, and the gap 32 were approximately 5 mm, the fluorescent tube was a cold cathode tube manufactured by Harrison, and the tube current was Is 1 O mA and the inside diameter of the tube is approximately 5 mm. In addition, using a cold cathode tube manufactured by Harrison Corporation, the tube current was set to 8 mA, and the temperature on the diffusion plate was changed in the configuration in Fig. 1 with the liquid crystal panel removed. At the time of measurement, the temperature rise at the center of the tube surface was 3.1 (ambient temperature 50 ° C). As for the temperature distribution of the lighting device, the maximum is 53.1 ° C and the minimum is 50.0 ° C as shown in Fig.15.

 As described above, according to the present invention, it is possible to obtain an illuminating device that has less luminance unevenness, has higher luminance, and can suppress a rise in temperature.

 In the above embodiment, the width of the gap between the prism plate and the diffusion plate is 5 mm. However, this gap may be omitted, or may be 5 mm or more. In the above embodiment, the prism apex angle was set to approximately 90 degrees, but the prism apex angle is not necessarily required to be 90 degrees, and a suitable apex angle (for example, from 60 degrees) (Between 120 degrees). Typical apex angles currently on the market are 90 degrees, 95 degrees, and 100 degrees. However, the first gap and the second gap in Fig. 1 must be set for each vertex angle of the prism plate used. For example, when a prism plate with an apex angle of 100 degrees is used, it is necessary to widen the gap when a prism plate with an apex angle of 90 degrees is used. In the above embodiment, the triangular prism plate may be BEF-90Z50 (vertical angle 90 degrees, pitch 50 m) or BEF2—90 / 50 (vertical angle) manufactured by 3M. A 90 degree pitch (50 urn) was used. As the corrugated prism plate, Estilna 425 manufactured by Sekisui Chemical was used. The diffusion member is made by Ewa Shoko. Lus P C — E S — 130 was used.

Claims

The scope of the claims 1. In a direct-type lighting device having at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube, The prism 扳 is provided with a first predetermined gap, and when viewed from the front of the prism plate, the prism is shifted with respect to the fluorescent tube in a direction perpendicular to the extension direction of the ridge line of the prism. The lighting device according to claim 1, wherein the first predetermined gap is set so that an image formed on the prism plate is formed.  2. In a direct-type lighting device having at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube, 1, a prism て is provided with a predetermined gap, a diffusion member is provided with a second predetermined gap in front of the prism plate, and a diffusion member is provided in front of the prism plate. The first predetermined gap is set so that when viewed, an image shifted from the fluorescent tube in a direction perpendicular to the direction in which the ridge of the prism extends is formed on the prism plate. A lighting device characterized by this.  3. The lighting device according to claim 1, wherein an extension direction of the fluorescent tube and an extension direction of a ridge line of the prism are parallel. 4. In a direct-type lighting device comprising at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube, A first prism plate is provided with a first predetermined gap, and a second prism plate is provided with a second predetermined gap in front of the first prism plate. When viewed from the front of the first prism plate, an image obtained by shifting the fluorescent tube in a direction perpendicular to the direction in which the ridge line of the first prism extends is perpendicular to the first prism plate. Pres Similarly, when viewed from the front of the second prism plate, it is shifted with respect to the fluorescent tube in a direction perpendicular to the extension direction of the ridge line of the second prism. An illumination device, wherein the first and second predetermined gaps are set so that an image is formed on the second prism plate.  5. The lighting device according to claim 4, wherein an angle formed by a ridge line of the first and second prisms is an optimum angle without luminance unevenness.  6. The extending direction of the fluorescent tube is parallel to the extending direction of the ridge line of the first prism plate, and the extending direction of the fluorescent tube is orthogonal to the extending direction of the ridge line of the second prism plate. The lighting device according to claim 4, 7. The first and second prisms are triangular prisms, and the angle between the ridges of the first and second prisms is 45. The lighting device according to claim 4, wherein the soil is set to 10 °.  8. The lighting device according to claim 4, wherein the first and second prisms are waveform prisms, and an angle formed by a ridge line of the first and second prisms is 0 °. 9. In a direct-type lighting device comprising at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube, A first prism plate is provided with a predetermined gap of 1, and a second prism plate is provided with a second predetermined gap in front of the first prism board; Further, a diffusion member is provided with a third predetermined gap provided in front of the second prism plate, and when viewed from the front of the first prism plate, the diffusion member is positioned with respect to the fluorescent tube. An image shifted in a direction orthogonal to the extension direction of the ridge line of the first prism is formed on the first prism plate, and similarly, a front image of the second prism plate is formed in front of the second prism plate. When viewed from above, an image shifted from the fluorescent tube in a direction perpendicular to the direction in which the ridge line of the second prism extends is formed on the second prism plate, An illumination device, wherein a second predetermined gap is set.  10. The lighting device according to claim 9, wherein an angle formed by a ridge line of the first and second prisms is an optimum angle without luminance unevenness.  10. The method according to claim 9, wherein the first and second prisms are triangular prisms, and an angle formed by a ridge line of the first and second prisms is 45 ° ± 10 °. Lighting equipment.  10. The illumination device according to claim 9, wherein the first and second prisms are waveform prisms, and an angle formed by a ridge line of the first and second prisms is 0 °.  3. The illuminating device according to claim 4, wherein the width of the first predetermined gap and the second predetermined gap is equal to or larger than the size of the inner diameter of the fluorescent tube.  14. The range of claim 9, wherein the width of the first predetermined gap, the second predetermined gap, and the third predetermined gap is equal to or larger than a substantially inner diameter of the fluorescent tube. Lighting equipment.  15. The lighting device according to claim 4 or 9, wherein the prisms of the first prism plate and the second prism plate have an apex angle of approximately 90 degrees.  16. The vertical angle of the prism between the first prism plate and the second prism plate is substantially 90 degrees, and the width of the first predetermined gap and the width of the second predetermined gap are respectively The lighting device according to claim 4, wherein the lighting device has substantially the same inner diameter as the fluorescent tube. 17. The prism of the first prism plate and the second prism plate has an apex angle of approximately 90 degrees, the first predetermined gap, the second predetermined gap, and the third predetermined gap. The width of the predetermined gap is substantially the same as the inner diameter of the fluorescent tube. The lighting device according to claim 9, wherein  18. In a direct-type lighting device comprising at least a fluorescent tube as a light source and a reflector for reflecting light from the fluorescent tube in front of the fluorescent tube,  A first prism is provided with a first predetermined gap in front of the fluorescent tube, and a second prism is provided with a second predetermined gap in front of the first prism. Arrange the board,  Fixing the first prism, rotating the second prism, and changing the angle formed by the extension direction of the ridge line of the second prism with respect to the extension direction of the ridge line of the first prism;  A method to determine the angle at which the luminance unevenness is minimized when viewed from above the prism plate.