JP2008166295A - Lighting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting apparatus having a backlight structure which illuminates a liquid display panel from a rear surface and can realize a high luminance and a high uniformity and a long service life. <P>SOLUTION: The lighting apparatus 1 is composed of a plurality of light guide plates 6a to 6e arranged on a light receiving surface side of a FP and cold cathode tubes 2b to 2e arranged closer to a rear surface side than a light emitting surface of the light guide plates of the light receiving surface side. Furthermore, the light apparatus 1 is provided with reflectors 4b to 4e attached on the cold cathode tubes 2b to 2e and on an opposite side of the light receiving surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illumination device for a display device, and more particularly to a backlight structure illumination device that is used in a liquid crystal display device and illuminates a liquid crystal display panel from the back.

  In recent years, liquid crystal display panels have been able to save space and have been evaluated by the market for their low power consumption. Not only display devices for portable computers and monitors for portable televisions, but also monitors for desktop personal computers and home use. Applications as flat-screen TVs are expanding. There are two types of illumination devices (backlight units) that illuminate the liquid crystal display surface of the liquid crystal display panel from the back, that is, a direct type and a side light type.

  FIG. 41 shows a schematic structure of a conventional direct illumination device. The direct type illumination device shown in FIG. 41 is arranged directly below the display surface rear surface (illuminated surface side) of a flat panel (FP) such as a liquid crystal display panel. In the direct type illumination device, a plurality of cold cathode fluorescent lamps (light emitting tubes) 502a to 502d, which are straight tubular light sources, are arranged below a diffusion plate (optical sheet) 500 serving as a surface light emitting unit, and the periphery thereof reflects light. It is covered with a member (reflector) 504. In the direct type illumination device, light emitted from the cold cathode fluorescent lamps 502a to 502d or light reflected by the reflector 504 is incident on the diffusion plate 500, is made uniform by the diffusion plate 500, and is irradiated to the flat panel FP. .

  FIG. 42 shows a conventional sidelight type illumination device. The sidelight type illumination device shown in FIG. 42 is disposed on the illuminated surface side of a flat panel FP such as a liquid crystal panel. The backlight unit includes a light source unit having cold cathode tubes 510 and 512 and reflectors 506 and 508, a light guide unit having a diffusion plate 516, a light guide plate 514, and a reflection plate 518. The diffusion plate 516 may be composed of a plurality of sheets depending on the light distribution specification of the light guide unit.

  In order to increase the brightness of the backlight unit, two sets of cold cathode tubes 510 and 512 are disposed at both ends of the light guide plate 514 together with the reflectors 506 and 508. Light emitted from the cold cathode tubes 510 and 512 to the side surface of the light guide plate 514 enters from the end face of the light guide plate 514 and is guided while being totally reflected inside the light guide plate 514. Further, light emitted to the reflectors 506 and 508 side of the cold cathode tubes 510 and 512 is reflected by the reflectors 506 and 508, and is also incident from the end face of the light guide plate 514 and is similarly guided through the light guide plate 514.

  A part of the light L1 being guided is emitted toward the reflecting plate 518 or the diffusion plate 516, and the light emitted toward the diffusion plate 516 is diffused in the direction of the flat panel FP by the diffusion plate 516. In addition, the light L <b> 2 emitted to the reflection plate 518 side is reflected by the reflection plate 518, passes through the light guide plate 514, and then enters the diffusion plate 516. This light also diffuses in the direction of the flat panel FP. The flat panel FP is illuminated by the diffused light from these two types of paths.

The sidelight type backlight unit guides the inside of the light guide plate 514 by arranging optical elements that break the light guide conditions such as the diffusion surface of the diffusion plate 516 and the refractive reflection surface of the reflection plate 518 at an arbitrary density. Since the light quantity distribution of the light rays to be adjusted can be adjusted, illumination with very high uniformity is possible. In addition, even if deterioration such as a reduction in the amount of light emitted from the light emitting surfaces of the cold cathode tubes 510 and 512 occurs, the distance between the cold cathode tubes and the surface to be illuminated is long, so that the unevenness is less noticeable. Have. On the other hand, since the cold cathode tubes 510 and 512 are disposed on the end face of the light guide plate 514, the number of cold cathode tubes that can be disposed is limited, and it is difficult to achieve high brightness.

  On the other hand, the direct system has the advantage that the brightness of the lighting device can be easily increased by increasing the number of cold cathode tubes 502a to 502d, but the distance between the cold cathode tubes 502a to 502d and the surface to be illuminated is short. Therefore, there is a problem that luminance unevenness is likely to occur. It is possible to optimize the distance between the cold cathode tubes 502a to 502d, the characteristics of the diffusion plate 500, or the shape of the reflector 504 so as not to cause unevenness. However, when conditions change, for example, the cold cathode tube 502a There is a problem that unevenness easily occurs due to the deterioration that reduces the light emission amount of a part of the ~ 502d light exit surface.

  The objective of this invention is providing the illuminating device which can implement | achieve high brightness | luminance, high uniformity, and long life.

  The above object is arranged between a plurality of light guide plates arranged on the illuminated surface side of the display panel and the plurality of light guide plates, and arranged on the back side from the light exit surface of the light guide plate on the illuminated surface side. This is achieved by an illumination device characterized by having an arc tube.

  In addition, the above object is provided in the vicinity of an incident surface of a transparent parallel plate-shaped substrate and an end portion on the substrate side where light emitted from a light source is incident, and is inclined upward from the substrate surface toward the incident surface. And an inclined portion having an inclination angle α set so that light incident from the incident surface is totally reflected by the inclined surface and then totally reflected in the substrate. Achieved by lighting device.

  Furthermore, the above object is achieved by a visible light source comprising a transparent member having a cavity, a discharge gas layer sealed in the cavity, and a phosphor layer formed flat on the discharge gas layer side. Achieved.

  As described above, according to the present invention, high luminance, high uniformity, and long life can be realized, so that a display device suitable for use in a flat panel display such as a liquid crystal display device can be realized.

[First Embodiment]
A lighting apparatus according to a first embodiment of the present invention will be described with reference to FIGS. First, an outline of the basic configuration of the lighting apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an illuminating device 1 according to the present embodiment arranged on a surface to be illuminated of a flat panel (hereinafter, representatively referred to as a liquid crystal panel) FP such as a liquid crystal panel. The illuminating device 1 has a plurality of light guide plates 6a to 6e arranged separately from each other. A plurality of light emitting tubes (cold cathode tubes) 2a to 2f are arranged on both side surfaces of each light guide plate 6a to 6e. The cold cathode fluorescent lamps 2a to 2f are provided on the back side of the light guide plates 6a to 6e facing the light exit surfaces of the light guide plates 6a to 6e that are on the surface to be illuminated of the liquid crystal panel FP among the surfaces of the light guide plates 6a to 6e. Yes. On the opposite side of the illuminated surface of the liquid crystal panel FP with respect to the cold cathode tubes 2b to 2e, a plurality of light guide plates 6a to 6e or directly to the diffusion plate 8 are irradiated with light from the cold cathode tubes 2b to 2e as light reflecting members. Reflectors 4b to 4e are provided. Cold cathode fluorescent lamps 2a and 2f and reflectors 4a and 4f are arranged on one side of the light guide plates 6a and 6e. The diffusion plate 8 is disposed between the light guide plates 6a to 6e and the liquid crystal panel FP.

  The illuminating device 1 according to the present embodiment having such a basic configuration can be regarded as a backlight structure combining a sidelight system and a direct system, or a sidelight type backlight unit is used as a liquid crystal panel FP. It can also be seen as a structure in which a plurality of lines are aligned along the surface. According to this basic structure, the number of arc tubes can be increased as compared with the conventional sidelight-type backlight structure, thereby making it possible to increase the brightness.

  Further, since the cold cathode tubes 2a to 2f are arranged between the light guide plates 6a to 6e and on the back side from the light exit surfaces of the light guide plates 6a to 6e, any one of the cold cathode tubes 2a to 2f is deteriorated. However, since the light emitted from the cold cathode tube adjacent to the light guides the light guide plates 6a to 6e, the shortage of the light quantity can be compensated. For example, since the light guide plate 6b is provided between the cold cathode tubes 2b and 2c, most of the light beams emitted from the cold cathode tube 2b pass through the light guide plate 6b and illuminate the adjacent cold cathode tube 2c side. For this reason, even if the light emission amount of the cold cathode fluorescent lamp 2c decreases due to deterioration or the like, the emitted light from the surrounding cold cathode fluorescent lamps 2a, 2b, 2d, 2e, etc. guides through the light guide plates 6a to 6e and Since it reaches the tube 2c side, the occurrence of uneven brightness can be suppressed as compared with the conventional direct type backlight structure.

Hereinafter, the lighting apparatus according to the present embodiment will be described more specifically with reference to examples.
(Example 1-1)
Example 1-1 of this embodiment will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The illuminating device 1 has a plurality of light guide plates 6a to 6e arranged separately from each other. Cold cathode tubes 2b, 2c, 2d, and 2e are sequentially arranged on both side surfaces of the light guide plates 6b, 6c, and 6d, respectively. Unlike the basic configuration shown in FIG. 1, the cold cathode tubes 2a and 2f are not arranged on one side of the light guide plates 6a and 6e.

  The reflector 4 has the same configuration as that of the reflector 504 used in the conventional direct illumination device shown in FIG. 41. In FIG. 2, the reflector 4a is provided to face the left side surface of the light guide plate 6a. A reflector 4c is provided to face the right side surface of the light guide plate 6e. A reflector 4b is provided on the entire lower surface including the opposing surfaces of the cold cathode fluorescent lamps 2b to 2e. The reflector 4b can reflect the light emitted from the cold cathode tubes 2b to 2e to the light guide plates 6a to 6e or directly to the diffusion plate 9. In the present embodiment, two diffusion plates 8 and 9 are laminated and disposed between the liquid crystal panel FP and the light guide plates 6a to 6e.

  The outer diameters of the cold cathode fluorescent lamps 2b to 2e arranged so as to be sandwiched between the light guide plates 6a to 6e are, for example, d = 2.6 mm. The light guide plates 6a to 6e are thin plate acrylic substrates of 5 mm (thickness) × 90 mm (width), for example, and the distance d1 between adjacent substrates with the cold cathode tube 2 interposed therebetween is, for example, d1 = 5 mm. The reflectors 4a to 4c are configured by a diffuse reflection plate having white inner walls surrounding the light guide plates 6a to 6e and the cold cathode fluorescent lamps 2b to 2e. The two diffused plates 8 and 9 that are stacked are arranged, for example, 20 mm away from the light guide plates 6a to 6e.

  For example, the light beam emitted from the cold cathode fluorescent lamp 2b is divided into a component L1 that goes directly to the diffusion plates 8 and 9 from a gap between the light guide plates 6a and 6b and a component L2 that enters the light guide plate 6b. At this time, the light quantity ratio between the components L1 and L2 is determined by the dimensional ratio between the light guide plates 6a and 6b and the cold cathode fluorescent lamp 2b. In this embodiment, about 40% of the light becomes the component L1, and the remaining 60%. A certain amount of light is incident on both side surfaces of the light guide plates 6a and 6b as the component L2.

The component L2 incident on the light guide plate 6b is further emitted as components L3 and L4 toward the diffusion plates 8 and 9. The component L3 is a component that is emitted from the light guide plate 6b, is incident on the cold cathode tube 2c, is scattered and reflected, and is emitted toward the diffusion plates 8 and 9 from the gap between the light guide plates 6b and 6c. The component L4 is a component that is emitted toward the diffusion plates 8 and 9 directly from the gap between the light guide plates 6c and 6d after being emitted from the light guide plate 6c.

  The ratio of the components L3 and L4 is determined by the dimensional ratio between the light guide plate 6 and the cold cathode tube 2 in the same manner as the light quantity ratio of L1: L2. In this example, the ratio of the component L3 was approximately 25%, and the ratio of the component L4 was approximately 40%. The remaining 35% of light enters the light guide plate 6d at the next stage, and thereafter proceeds while repeating the same operation.

  Thus, the light beam emitted from the cold cathode fluorescent lamp 2b reaches the surrounding cold cathode fluorescent lamps 2c to 2e by the light guide plates 6a to 6e and is emitted. For this reason, the light rays emitted from the gaps between the light guide plates 6a to 6e are not only the cold cathode tubes 2b to 2e disposed in the gaps but also the light rays emitted from the surrounding cold cathode tubes 2b to 2e.

  Light rays emitted from between the light guide plates 6 a to 6 e travel while spreading and enter the diffusion plates 8 and 9. The diffusing plates 8 and 9 transmit incident light and scatter it in all directions, and reflect and scatter about 1/2 light. The reflected diffused light is reflected by the reflector 4b via the light guide plates 6a to 6e and the cold cathode tubes 2b to 2e, and then passes again through the light guide plates 6a to 6e and the cold cathode tubes 2b to 2e. 9 and half of the light is emitted toward the liquid crystal panel FP. At this time, uneven brightness can be prevented from being visually recognized by adjusting the distance between the diffusion plates 8 and 9, the diffusion characteristic, the distance from the reflector 4b, or the distance between the cold cathode fluorescent lamps 2b to 2e.

  However, since the characteristics of the cold cathode fluorescent lamps 2b to 2e change with time and have individual differences, the degree is less than that of a direct type backlight of a conventional structure, but even if there is no problem at the beginning of the life, Luminance unevenness may occur. In the present embodiment, measures are also taken for such a problem, which will be described below.

  Here, when the light quantity of an arbitrary cold-cathode tube 2 is reduced to 70%, the in-plane luminance unevenness in the backlight to which this embodiment is applied and the general direct-type backlight not applied will be compared. (1) In the case of a general direct type backlight, it is about 70% (generally the same as the decrease in the amount of light in the cold cathode tube), whereas (2) in the case of the backlight of this embodiment, About 40% (light rays 40% directly from the cold-cathode tubes 2b to 2e toward the diffusion plates 8 and 9 change to 28%, but light guide plates 6a to 6e guide light from the surrounding cold-cathode tubes 2b to 2e. The amount of light 60% is not changed). As described above, according to the present embodiment, even if the light emission amount of any one of the cold cathode fluorescent lamps 2b to 2e is reduced, the influence of luminance unevenness is relatively small, and uniform illumination is possible. A long-life lighting device can be realized.

(Example 1-2)
Example 1-2 of this embodiment will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. In the illumination device 1 according to the present embodiment, a diffusion pattern 10 in which a diffusion layer is patterned as an element for changing the light beam angle during light guide is provided on the back surface of the light guide plates 6a to 6e of the illumination device 1 in Embodiment 1-1. It is characterized in that Further, the diffusion plate 9 is removed from the diffusion plates 8 and 9, and only one diffusion plate 8 is disposed. Since other components are the same as those shown in the embodiment 1-1, the description thereof is omitted.

  Light rays emitted from the cold cathode tubes 2a to 2e and incident on the light guide plates 6a to 6e travel while repeating total reflection inside the light guide plates 6a to 6e, but are incident on the diffusion pattern 10 formed on the back surfaces of the light guide plates 6a to 6e. The diffused light is diffusely reflected, and about 1/4 component does not satisfy the total reflection condition, and is emitted from the light exit surfaces of the light guide plates 6a to 6e and enters the diffusion plate 8. This is the same principle as a conventional sidelight type backlight.

  For example, the light beams L1 and L2 emitted from the cold cathode fluorescent lamp 2b can be emitted from a wide range by traveling through the light guide plates 6a to 6e. Similarly, the light beams emitted from the cold cathode tubes 2a, 2c to 2f are emitted to the diffusion plate 8 while proceeding in the light guide plates 6a to 6e. Therefore, from any point on the light guide plates 6a to 6e, a plurality of cold cathodes are used. The light beams emitted from the tubes 2a to 2f are mixed and emitted.

  By setting the diffusion pattern 10 to an appropriate size and arrangement density, substantially uniform emission light can be obtained from the light guide plates 6a to 6e. For this reason, in Example 1-1, it is possible to use only one diffusion plate 8 as the diffusion plates 8 and 9, which are required for making the light quantity uniform. Compared to Example 1-1, the light emission components from the light guide surfaces 6a to 6e where the light emission characteristics of the cold cathode fluorescent lamps 2b to 2e are less likely to appear are increased, so only one diffusion plate 8 is used. In spite of this, it is possible to reduce unevenness in luminance based on solid-state differences in the emission intensity of the cold cathode fluorescent lamps 2b to 2e and changes with time.

(Example 1-3)
Example 1-3 of this embodiment will be described with reference to FIGS. FIG. 4 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. FIG. 5 is a partially enlarged view of the vicinity of the cold cathode fluorescent lamp 2c. The illuminating device 1 according to the present embodiment is characterized in that a diffusing plate 12 is disposed as a light scattering element between adjacent ones of the light guide plates 6a to 6e on the light exit surface side of the illuminating device 1 in Embodiment 1-2. Have. The other constituent elements are the same as those shown in the embodiment 1-2, and the description thereof is omitted.

  In the structure shown in Example 1-2 described above, the density of the light beam directly emitted from the cold cathode fluorescent lamps 2a to 2e to the diffusion plate 8 is higher than the density of the light beam emitted from the light exit surfaces of the light guide plates 6a to 6e. Become bigger. For this reason, in this embodiment, the diffusion plate 12 is stretched between adjacent ones of the light guide plates 6a to 6e on the light emission surface side, and the amount of light emitted directly from the cold cathode tubes 2a to 2e to the diffusion plate 8 is caused by the diffusion plate 12. The light quantity is reduced to about ½, and the remaining light quantity of about ½ is diffusely reflected. The diffusion plate 12 has a thickness that is approximately 1/5 or less of the thickness of the light guide plates 6a to 6e. Most of the reflected light component on the diffusion plate 12 is incident on the light guide plates 6a to 6e, and part of the light component is scattered by the diffusion pattern 10 and is emitted from the light exit surfaces of the light guide plates 6a to 6e. By doing so, the difference in light density between the light emitted from the light guide plates 6a to 6e and the light emitted from between the light guide plates 6a to 6e can be reduced, and the cold cathode tubes 2a to 2e can be reduced. The influence of the variation in the amount of light on the display can be further reduced.

  In this embodiment, the diffusion plate 12 is stretched between adjacent ones of the light guide plates 6a to 6e on the light exit surface side. However, instead of the diffusion plate 12, an anisotropic diffusion plate (difference different in diffusivity depending on the incident direction) is used. An isotropic scatterer may be stretched over. Light rays that travel upward from the respective end surfaces of the light guide plates 6a to 6e are diffused strongly, and light rays that travel from the respective end surfaces of the light guide plates 6a to 6e to the opposite other end surface are weakly diffused (if possible, do not diffuse). Even if it is not the plate 12, the direct light from the cold cathode fluorescent lamps 2a to 2e can be diffused and made uniform without obstructing the progress of light between the light guide plates 6a to 6e. That is, in the anisotropic scattering plate, a relationship of A <B is established between the scattering degree A in the direction parallel to the illuminated surface and the scattering degree B in the direction orthogonal to the illuminated surface. As the anisotropic diffusion plate, for example, a liquid crystal polymer resin in which a material having refractive index anisotropy is aligned and dispersed in a material having no refractive index anisotropy can be used.

In the present embodiment, the amount of light emitted from the gap to the diffusion plate 8 is reduced by stretching the diffusion plate 12 that diffuses and reflects about 1/2 of the light amount to the gap between the light guide plates 6a to 6e. A reflecting plate may be used instead of the diffusing plate 12. FIG. 6 shows an example in which, instead of the diffusing plate 12, a reflecting plate 14 having a reflecting surface substantially coinciding with the light guide plates 6a to 6e is disposed in the gap between the light guiding plates 6a to 6e. FIG. 6 shows a partially enlarged view of the vicinity of the cold cathode tube 2c. The reflection plate 14 is disposed at a substantially central portion of a surface that is a gap between the light guide plates 6b and 6c and substantially coincides with the light emission surface of the light guide plates 6b and 6c. The reflection plate 14 and the light guide plates 6b and 6c have no light. There is a gap through which L1 and L2 can pass. Thereby, of the light emitted from the cold cathode fluorescent lamp 2c, some of the lights L1 and L2 are directly incident on the diffusion plate 8, and the remaining lights L3 and L4 are incident on the light guide plates 6b and 6c.

  FIG. 7 shows an example in which, instead of the diffusion plate 12, a wedge-shaped reflection plate 16 having a convex reflection surface formed toward the cold cathode tubes 2b to 2e is arranged in the gap between the light guide plates 6a to 6e. FIG. 7 shows a partially enlarged view of the vicinity of the cold cathode tube 2c. The reflection plate 16 is disposed at substantially the center of the gap between the light exit surfaces of the light guide plates 6b and 6c, and the reflection plate 16 and the light guide plates 6b and 6c have gaps through which light L1 and L2 can pass. Thereby, of the light emitted from the cold cathode fluorescent lamp 2c, some of the lights L1 and L2 are directly incident on the diffusion plate 8, and the remaining lights L3 and L4 are incident on the light guide plates 6b and 6c.

  6 and 7 can also reduce the light amount difference between the light emitted from the light guide plates 6a to 6e and the light emitted from between the light guide plates 6a to 6e. It is possible to further reduce the influence of variations in the amount of light between the cathode tubes 2a to 2e on the display.

(Example 1-4)
Example 1-4 of this embodiment will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. 9 and 10 are partially enlarged views of the vicinity of the cold cathode tube 2c of FIG. The illuminating device 1 according to the present embodiment is characterized in that the light incident surfaces 18 of the respective end surfaces of the light guide plates 6a to 6e provided with the diffusion pattern 10 of the illuminating device 1 in the embodiment 1-2 are inclined. ing. As shown in FIGS. 8 to 10, the light incident surfaces 18 of the light guide plates 6a to 6e on both sides of the cold cathode fluorescent lamps 2b to 2e are spaced apart from each other on the light exit surface side of the adjacent light guide plates 6a to 6e. It arrange | positions so that it may become smaller than a space | interval. The other constituent elements are the same as those shown in the embodiment 1-2, and the description thereof is omitted.

  In the light guide plates 6a to 6e of the present embodiment, a polycarbonate plate having a refractive index n of 1.41 or more is used as a base material. The polycarbonate plate is a thin plate having a trapezoidal cross section with a thickness t1 of about 8 mm, a width on the light emission surface side of 90 mm, and a width on the back surface side of 86.6 mm. The light incident surfaces 18 at the end portions of the light guide plates 6a to 6e are formed so that the angle θ formed with the diffusion pattern 10 forming surface on the rear surfaces of the light guide plates 6a to 6e is 102 °. The distance d2 between adjacent back surfaces of the light guide plates 6a to 6e (the surface on which the diffusion pattern 10 is formed) is about 3.4 mm, and the thickness t1 of the light guide plates 6a to 6e is about 8 mm. The exit surface end portions are in contact with each other.

  For this reason, according to the configuration of the present embodiment, in Embodiments 1-1 to 1-3, the light beam that has been directly incident on the diffusion plate 8 from between the light guide plates 6a to 6e can enter the light guide plates 6a to 6e. become able to. For example, in FIG. 9, since the angle θ formed by the light incident surface 18 and the diffusion pattern 10 forming surface is 102 ° (= 90 ° + 12 °), the cold cathode tube 2 c is emitted and directly incident on the diffusion plate 8. The incident angles θ2 and θ3 at which the light rays L1 and L2 are incident on the light guide plates 6b and 6c are 51 ° or more and satisfy the total reflection condition of polycarbonate having a refractive index n = 1.59 or more. Can be handled. In the present embodiment, since the light guide plates 6a to 6e for emitting light uniformly exist on the entire surface on the diffusion plate 8 side, illumination with very high uniformity can be performed.

  Also, as illustrated in FIG. 10, most of the light beam L3 that exits the light guide plate 6c and enters the light guide plate 6b is refracted in a direction that avoids the cold cathode tube 2c. For this reason, the light beam L3 emitted from the cold cathode fluorescent lamp 2c can be guided to a farther distance, and the luminance unevenness based on the difference in light emission intensity of the cold cathode fluorescent lamps 2b to 2e and the change with time can be further reduced.

FIG. 11 shows a modification in which cold cathode fluorescent lamps 2a and 2f with C-type reflectors 4a and 4c similar to the sidelight type backlight unit are arranged outside the light guide plates 6a and 6e at both ends. Even if it is such a structure, the effect of a present Example can be acquired. Of course, in other embodiments, it is possible to adopt a configuration in which the cold cathode tubes 2a and 2f with the C-shaped reflectors 4a and 4c shown in FIG. 11 are arranged.

(Example 1-5)
Example 1-5 of this embodiment will be described with reference to FIG. FIG. 12 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The illuminating device 1 according to the present embodiment is the second between the light guide plates 6a to 6e and the diffusion plate 8 without providing the diffusion pattern 10 on the back surface of the light guide plates 6a to 6e of the illumination device 1 in Example 1-4. It is characterized in that the light guide plate 20 is disposed and the diffusion pattern 10 is provided on the back surface thereof. In addition, the optical bonding resin layer 22 is disposed between the light guide plates 6a to 6e and the second light guide plate 20. Since other components are the same as those shown in the embodiment 1-4, the description thereof is omitted.

  The second light guide plate 20 has the same configuration as a light guide plate with a diffusion pattern used in a general sidelight type backlight unit. For example, a plurality of diffusion patterns 10 are formed on one side of a polycarbonate substrate. The optical bonding resin layer 22 is also called an optical adhesive, and has a refractive index n that is matched to that of polycarbonate and has a high transmittance. The 2nd light guide plate 20 is affixed on the light guide plates 6a-6e via the optical joining resin layer 22. FIG.

  For example, light rays L1 and L2 incident on the contact surface of the optical bonding resin layer 22 out of the light rays that are emitted from the cold cathode tube 2b and incident / guided on the light guide plates 6a to 6e are reflected by the optical bonding resin layer 22. Without being transmitted, the light enters the second light guide plate 20. The light beam guided in the light guide plates 6 a to 6 e is not totally emitted except for the optical bonding resin layer 22 and emitted to the second light guide plate 20 side. For this reason, light travels to the second light guide plate 20 with high efficiency via the optical bonding resin layer 22. These light rays L 1 and L 2 are guided through the second light guide plate 20, scattered by the diffusion pattern 10, emitted from the light exit surface of the second light guide plate 20, and reach the diffusion plate 8. In the configuration of the present embodiment, the locality of the cold cathode tubes 2b to 2e is almost completely lost, so that the luminance unevenness based on the difference between the cold cathode tubes 2b to 2e and changes with time can be further reduced.

(Example 1-6)
Example 1-6 of this embodiment will be described with reference to FIGS. FIG. 15 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. 14 and 15 are partially enlarged views of the vicinity of the cold cathode tube 2c of FIG. The illuminating device 1 according to the present embodiment forms a recess 24 below the cold cathode tubes 2b to 2e of the reflector 4b of the illuminating device 1 according to the embodiment 1-4, and the cold cathode tubes 2b to 2e in each recess 24. It has a feature in that it accommodates. That is, the tube centers of the cold cathode fluorescent lamps 2b to 2e in the other embodiments are located on the back side of the light guide plates 6a to 6e, but in this embodiment, the light guide plates 6a to 6e are further irradiated. The light guide plates 6a to 6e are located away from the rear surface when viewed from the surface. Since other components are the same as those shown in the embodiment 1-4, the description thereof is omitted.

  In the present embodiment, the cold cathode tubes 2b to 2e are accommodated in the respective recesses 24 as in the light rays L1 to L3 shown in FIGS. 14 and 15, so that the cold cathode tubes 2b to 2e between the light guide plates 6a to 6e are stored. Since interference such as reflection, refraction, and absorption of the light beams L1 to L3 by 2e is reduced, the light beams L1 to L3 can be guided to the farther light guide plates 6a to 6e with low loss.

In addition, the recessed part 24 which is the characteristic of a present Example is applicable similarly to the above-mentioned Example 1 thru | or 5 and the Example in this embodiment after this. For example, in FIG. 16, the concave portions 24 are formed below the cold cathode tubes 2 b to 2 e of the reflector 4 b of the lighting device 1 shown in FIG. 2 of Example 1-1, and the cold cathode tubes 2 b to 2 are formed in the concave portions 24. It is characterized in that 2e is accommodated.
Moreover, FIG. 17 has shown the state which provided the recessed part 24 in the illuminating device 1 shown in FIG. 4 of Example 1-3. Thus, as shown in FIG. 18, the light beam L1 emitted from the light guide plate 6b in the direction of the light guide plate 6c is incident on the adjacent light guide plates 6a to 6e without being blocked by the cold cathode tube 2c and the diffusion plate 12c. it can. For this reason, the emitted light from each of the cold cathode fluorescent lamps 2b to 2e can be guided to the farther light guide plates 6a to 6e, and uneven brightness due to variations in the amount of light of the cold cathode fluorescent lamps 2b to 2e due to changes over time is less likely to occur.
FIG. 19 shows a state in which the recess 24 is provided in the lighting device 1 according to a modification of Example 1-3 illustrated in FIG.
Thus, the concave portion 24 can be easily provided in the reflector 4b to accommodate the cold cathode fluorescent lamps 2b to 2e, so that the absorption of light rays by the cold cathode fluorescent lamps 2b to 2e between the light guide plates 6a to 6e can be reduced and further away. Various illumination devices that can guide the light beams L1 to L3 with low loss can be realized.

(Example 1-7)
Example 1-7 of this embodiment will be described with reference to FIGS. FIG. 20 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The illuminating device 1 according to the present embodiment is a triangle that becomes a plurality of concave and convex portions having a triangular cross section instead of providing the diffusion pattern 10 on the rear surface of the light guide plates 6a to 6e of the illuminating device 1 shown in FIG. A feature is that a concave portion 26 is provided. The triangular concave portion 26 has an isosceles triangular shape with an apex angle of 70 °, and is formed on the back surface of the light guide plates 6a to 6e so that the area ratio is 20% at a pitch of 1 mm. Since other components are the same as those shown in the embodiment 1-4, the description thereof is omitted.

  The triangular recessed part 26 provided in the back surface of the light-guide plates 6a-6e of a present Example functions as a spreading | diffusion element which changes the light ray angle during light guide similarly to the diffusion pattern 10 of Example 1-4. However, since the concave triangular slope is used for light diffusion, the method of diffusing the emitted light is different from the case where the diffusion pattern 10 is used. The difference will be described with reference to FIG. FIG. 21A shows the rays of scattered light in the light guide plates 6a to 6e (example 6c in the figure) of Example 1-4. The light beam L1 being guided is incident on one of the diffusion patterns 10 formed in a dot shape and travels through the light guide plate 6c as a light beam L2 scattered at a plurality of traveling angles. The spread of the exit angle of the light beam L2 from the diffusion pattern 10 is a predetermined range centered on the incident angle of the light beam L1 to the diffusion pattern 10, and therefore the light guide plate does not satisfy the total reflection condition. The component of the light beam L3 emitted from the 6c light exit surface is slightly deviated from the total reflection condition. Accordingly, most of the light beam L3 emitted from the light guide plate 6c is a component substantially parallel to the light exit surface of the light guide plate 6c.

  FIG. 21B shows light rays of scattered light in the light guide plates 6a to 6e (6c is illustrated in the figure) of the present embodiment. The convergent light beam L1 during the light guide is reflected once on the back surface of the light guide plate 6c, enters the inclined surface of the triangular concave portion 26, and becomes a divergent light beam L2 reflected in a direction substantially perpendicular to the light exit surface of the light guide plate 6c. The divergent light beam L2 is incident on the diffusion plate 8 as a divergent light beam L3 that is emitted from the light guide plate 6c and is emitted substantially vertically.

As described above, the light guide plates 6a to 6e having the diffusion pattern 10 arranged on the back face have many light components emitted obliquely from the light exit faces of the light guide plates 6a to 6e, whereas the triangular recess 26 is formed on the back face. In the light guide plates 6a to 6e of the present embodiment, the light components in the direction along the normal direction of the substrate surface increase. Therefore, by providing a distribution in the arrangement density of the triangular concave portions 26 on the back surfaces of the light guide plates 6a to 6e, light can be easily emitted from almost the entire surface of the light guide plates 6a to 6e. In addition, when the diffusion pattern 10 is used, an optical path changing means for directing a light beam traveling in an oblique direction toward the surface to be illuminated is required. On the other hand, when the triangular concave portion 26 of this embodiment is used, Since the light emitted from the optical plates 6a to 6e is directed toward the illuminated surface from the beginning, there is no need to provide an optical path changing means. Therefore, the diffusing characteristic of the diffusing plate 8 can be lowered, and the lighting device 1 with high efficiency / low cost can be realized. It should be noted that the triangular concave portion 26 shown in the present embodiment, of course, produces the same effect even if it is formed on the back surface of the light guide plates 6a to 6e disclosed in other embodiments of the present embodiment.

(Example 1-8)
Example 1-8 of this embodiment will be described with reference to FIG. FIG. 22 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The illuminating device 1 according to the present embodiment is a reflective type as a reflective optical path changing element between the diffusion plate 8 of the illuminating device 1 shown in FIG. 20 of Example 1-7 and the illuminated surface of the liquid crystal display panel FP. It is characterized in that the polarizing plate 28 is disposed. The other constituent elements are the same as those shown in the embodiment 1-7, and the description thereof is omitted.

  The reflective polarizing plate 28 has a function of selectively transmitting linearly polarized light having a predetermined polarization direction and reflecting light having another polarization direction. As the reflective polarizing plate 28, for example, DBEF manufactured by 3M Corporation can be used. In this embodiment, the transmission polarization axis of the reflective polarizing plate 28 and the transmission polarization axis on the illuminated surface side of the liquid crystal panel FP are matched. Note that the diffusion plate 8 of this example has a lower diffusivity than the diffusion plate 8 of Example 1-7.

  As shown in FIG. 21B of Example 1-7, when the light beam L3 whose main component is an emission direction substantially perpendicular to the light emission surfaces of the light guide plates 6a to 6e is emitted, the emitted light beam has a relative scattering degree. After being scattered by the low diffusion plate 8, the light enters the reflective polarizing plate 28. The reflective polarizing plate 28 has a transmission polarization axis set in a direction parallel to the light source, and reflects polarized components other than this direction. The reflected reflected light beam L1 is incident again on the reflective polarizing plate 28 through the diffusion plate 8, the light guide plates 6a to 6e, and the reflectors 4a to 4c. During this time, the reflected light beam L1 is disturbed in polarization and becomes almost non-polarized light. By repeating the reflection cycle at the reflective polarizing plate 28 several times, almost all light passes through the reflective polarizing plate 28 as linearly polarized light. As described above, since the directions of the polarization transmission axes of the reflective polarizing plate 28 and the illuminated surface side of the liquid crystal panel FP coincide with each other, almost all of the emitted light from the reflective polarizing plate 28 is used for image display. Can contribute.

  In addition, about half of the light reflected by the reflective polarizing plate 28 is present. For this reason, even if luminance unevenness occurs in the light emitted from the light guide plates 6a to 6e, between the component that first passes through the reflective polarizing plate 28 and the component that passes through the reflective polarizing plate 28 after being reflected once. The brightness unevenness cancels out. Therefore, in this embodiment, the unevenness in the amount of light can be suppressed low.

  Thereby, even if the unevenness of luminance is not completely eliminated by the diffuser plate 8, sufficiently uniform illumination can be performed, and therefore, the diffuser plate 8 having a lower diffusivity than the diffuser plate 8 used in Example 1-7 can be used. . Thus, according to the present embodiment, a highly efficient backlight unit can be realized by the combination of the diffusion plate 8 having a low diffusivity and the reflective polarizing plate 28.

(Example 1-9)
Example 1-9 of this embodiment will be described with reference to FIG. FIG. 23 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The illuminating device 1 according to the present embodiment is the back surface of the second light guide plate 20 of the illuminating device 1 shown in FIG. 12 of Example 1-5, and does not have a plurality of diffusion patterns 10 arranged at a predetermined density. It is characterized in that a plurality of optical bonding resin layers 22 are arranged in the region. Since other components are the same as those shown in the embodiment 1-5, the description thereof is omitted.

The light beams emitted from the cold cathode fluorescent lamps 2b to 2e are incident on the light guide plates 6a to 6e and guided. The light beams L1 incident on the light guide surfaces 6a to 6e contacting the light bonding resin layer 22 are optically bonded. The light enters the second light guide plate 20 without being reflected by the contact surface with the resin layer 22. The light beam guided through the light guide plates 6a to 6e is efficiently incident on the second light guide plate 20 because it does not exit the light guide plates 6a to 6e except for the optical bonding resin layer 22. The light beam L1 is guided through the second light guide plate 20, enters the diffusion pattern 10, exits from the second light guide plate 20, and enters the diffusion plate 8 as a light beam L2. According to the present embodiment, since the locality of the cold cathode tubes 2b to 2e is almost completely lost, it is possible to ignore the luminance variation due to the temporal change of the cold cathode tubes 2b to 2e and the difference in solids.

  As described above with reference to the specific examples, according to the present embodiment, even when a plurality of cold cathode tubes are arranged directly under the surface to be illuminated, the luminance due to the deterioration of the cold cathode tubes and the solid difference Luminance unevenness due to variation can be reliably prevented. Thereby, a high-output and highly uniform illumination device can be realized.

[Second Embodiment]
A lighting device according to a second embodiment of the present invention will be described with reference to FIGS. The present embodiment relates to a backlight structure of a display device, and more particularly to a light guide plate structure of a sidelight type backlight unit that illuminates a liquid crystal display panel from the back.

  As a light guide plate for a conventional sidelight type backlight unit, a transparent plastic substrate such as acrylic is used. As the plastic substrate, there are a parallel plate substrate having a uniform thickness and a so-called wedge substrate which becomes thinner in a direction away from the substrate side end on the light source (arc tube) side.

  When a parallel plate-like substrate is used for the light guide plate, the substrate needs to be thick in order for light from the light source to enter the light guide plate with high light utilization efficiency. On the other hand, in order to reduce the thickness, weight, and cost of the liquid crystal display panel, it is necessary to make the substrate thinner. In this way, a parallel plate-like substrate has a trade-off relationship with respect to the substrate thickness. For this reason, the light-guide plate of a parallel plate-shaped board | substrate has the problem that high efficiency, weight reduction, and cost reduction cannot be compatible.

  On the other hand, when a wedge-shaped substrate is used for the light guide plate, light guided through the light guide plate gradually leaks out from the light guide plate without being totally reflected, so it is necessary to provide a taper angle that forms a wedge shape with high accuracy. is there. Therefore, the wedge-shaped substrate cannot suppress the manufacturing cost and has a problem that it is not suitable for a large-sized backlight unit. An object of the present embodiment is to provide a lighting device that is small and lightweight, has high light utilization efficiency, and can be manufactured at low cost.

  The light guide plate of the illuminating device according to the present embodiment is generally composed of a parallel plate-like substrate, but an inclined portion is provided in the vicinity of the incident surface SO at the end portion of the light guide plate on which light emitted from the light source enters. It has a feature in that. The inclined portion is formed of a material having the same refractive index as that of the parallel plate substrate.

  The inclined portion has an inclined surface having an upward slope from the parallel flat substrate surface (the light exit surface or the back surface facing it) toward the incident surface SO. The angle between the inclined surface and the plane of the parallel plate substrate (hereinafter referred to as the tilt angle) is such that light incident on the inclined portion from the incident surface SO is totally reflected on the inclined surface and then totally reflected on the parallel plate substrate. Is set to

  The length of the inclined surface (hereinafter referred to as the inclined length) in a cross section cut by a plane perpendicular to both the inclined surface and the parallel plate substrate surface is such that incident light from the incident surface SO does not enter the inclined surface more than once. Is set to

  By providing such an inclined portion, the opening area of the reflector surrounding the light source, that is, the area of the incident surface SO of the light guide plate is increased, and the light utilization efficiency can be increased. Further, if the light use efficiency is the same, the plate thickness of the parallel plate substrate of the light guide portion can be formed thin.

Hereinafter, the lighting apparatus according to the present embodiment will be described more specifically with reference to examples.
(Example 2-1)
Example 2-1 of this embodiment will be described with reference to FIGS. FIG. 24 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The lighting device 1 includes a light source unit 34 and a light guide unit 36. Although this illuminating device 1 also has a reflecting plate, a diffusion sheet, etc., it is unnecessary for the description of the present embodiment, and hereinafter, illustration and description thereof will be omitted unless necessary in the present embodiment.

  The light source unit 34 includes the cold cathode tube 2 and the reflector 4. The light guide unit 36 includes a parallel plate-like substrate 6 made of a transparent base material such as acrylic resin, and an incident surface SO of an end portion on the side of the parallel plate-like substrate 6 on which light emitted from the opening of the reflector 4 of the light source unit 34 enters. It has the inclination parts 30 and 32 provided in the vicinity. The inclined portions 30 and 32 are made of the same material as the parallel plate substrate 6. The parallel plate substrate 6 is disposed substantially parallel to the illuminated surface of the liquid crystal panel FP. In the present embodiment, the surface closer to the illuminated surface of the liquid crystal panel FP on the surface of the parallel flat substrate 6 is the light emitting surface, and the far side is the back surface.

  The inclined portion 30 is formed on the light emission surface side of the parallel plate substrate 6 and has an inclined surface 30a that is inclined upward toward the incident surface SO. The inclination angle α of the inclined portion 30 is set so that light incident on the inclined portion 30 from the incident surface SO is totally reflected by the inclined surface 30a and then totally reflected within the parallel plate substrate 6 as well. Similarly, the inclined portion 32 also has an inclined surface 32a with an inclination angle α and is formed on the back side of the parallel plate substrate 6.

  The inclination length l of each of the inclined portions 30 and 32 is set so that the incident light from the incident surface SO does not enter the inclined surfaces 30a and 32a more than once. The incident surface SO includes the incident surface SO-side end surfaces of the inclined portions 30 and 32 and the incident surface SO-side end surface of the parallel flat substrate 6 and is substantially in the same plane.

  Next, the illumination operation of the illumination device 1 according to the present embodiment will be described with reference to FIG. FIG. 25 shows a state in which light emitted from the light source unit 34 is guided in the light guide unit 36. First, the incident light L1 from the light source unit 34 enters the incident surface SO at an incident angle of 0 ° to 90 °. When the refractive index of the light guide 36 is n, the incident light L1 is guided to the light guide 36 as refracted light L2 having a refraction angle of 0 ° to (90 ° −θ) according to the refractive index n on the incident surface SO. Is done. Here, the angle θ is an incident angle of the refracted light L2 incident on the inclined surface 30a or the inclined surface 32a when the inclination angle α = 0.

Therefore, assuming that the refractive index of air is n0 = 1.0, for the incident surface SO, from Snell's law and total reflection condition,
n · sin (90 ° -θ)
= N0 · sin (90 °)
= 1
∴ (90 ° −θ) = sin ⁻¹ (1 / n) (1)
It becomes.

  The inclination angle α of each of the inclined portions 30 and 32 is such that the light L2 guided to the light guide portion 36 is totally reflected by either the inclined surface 30a or the inclined surface 32a, and then in the parallel plate substrate 6 It is set to totally reflect. For example, the light L3 totally reflected by the inclined surface 30a does not enter the opposing inclined surface 32a but enters the back surface of the parallel plate substrate 6 and thereafter repeats total reflection in the parallel plate substrate 6 thereafter. Light guide. Similarly, the light totally reflected by the inclined surface 32a does not enter the opposing inclined surface 30a, but enters the back surface of the parallel plate substrate 6 and thereafter repeats total reflection in the parallel plate substrate 6 thereafter. Light guide.

  The inclination length l of the inclined portions 30 and 32 is such that the light totally reflected by the inclined surface 30a (32a) does not enter the opposite inclined surface 32a (30a) again with respect to all the light incident from the incident surface SO. Length is set.

  In order to maximize the effect of the present embodiment, the inclined portions 30 and 32 desirably have a larger inclination angle α and desirably have a shorter inclination length l. Therefore, each value is actually set so that the following relational expression is established. Hereinafter, a case where the refracted light L2 is incident on the inclined portion 30 as shown in FIG. 25 will be described as an example.

here,
h: plate thickness of parallel portion of parallel flat substrate 6 n: refractive index of light guide portion Δh: height of light incident surface SO of inclined portion 30 from light exit surface of parallel flat substrate 6 Δ = n · Δh ( = Optical distance)
It is.

When the light beam L1 is refracted by the incident surface SO at a refraction angle of (90 ° −θ) and enters the inclined surface 30a having the inclination angle α as the refracted light L2, the incident angle of the refracted light L2 on the inclined surface 30a is θ−α. It becomes. Then, the totally reflected light L3 reflected by the inclined surface 30a enters the back surface of the parallel plate substrate 6 at an incident angle θ-2α. Therefore, in order for the light L2 guided to the light guide part 36 to be totally reflected by the inclined surface 30a and then totally reflected in the parallel plate substrate 6, the inclination angle α of the inclined part 30 is Snell's law. From the total reflection condition
n · sin (θ-2α)
≧ n0 · sin (90 °) = 1
・ N · sin (θ-2α) ≧ 1 Equation (2)
Need to be satisfied.

Further, in order to prevent the incident light from the incident surface SO from entering the inclined surfaces 30a and 32a more than once, the inclination length l of each of the inclined portions 30 and 32 is as shown in FIG.
(N · h + Δ) · tan (θ) = n · l · cos (α)
∴ (h + Δh) · tan (θ) = l · cos (α) (3)
Need to be satisfied.

Furthermore, referring to FIG.
n · l · sin (α) = Δ
Ｌ l · sin (α) = Δh Equation (4)
Moreover, from the equation (1),
n · cos (θ−α) = 1 Expression (5)
It is.

  In this embodiment, acrylic resin is used as a material for forming the light guide 34. The refractive index of the acrylic resin is n = 1.49. Therefore, from equation (1), θ = 47.84 °. Further, by substituting the value of θ into the equation (2), the inclination angle α = 5.68 ° is obtained.

The plate thickness of the parallel portion of the parallel plate substrate 6 is h = 10 mm, and the height from the light exit surface of the parallel plate substrate 6 on the incident surface SO of the inclined portion 30 is Δh = 0.6 mm. Substituting into equation (3) to obtain the slope length l,
l = (10 + 0.6) · tan (47.84 °) / cos (5.68 °)
= 11.76 mm
It becomes.

  According to this embodiment, the width of the opening of the reflector 4 can be increased by 1.2 mm (= 2 · Δh) compared with the case where a conventional parallel plate type light guide plate having a thickness of 10 mm is used. The amount of light introduced into the light unit 36 can be increased by 8% compared to the conventional art. As a result, the reflector 4 and the cold cathode tube 2 can be further separated from each other, so that the emitted light emitted from the cold cathode tube 2 to the reflector 4 side can be easily taken out to the light guide unit 36 side. In the present embodiment, the parallel plate substrate 6 and the inclined portions 30 and 32 are illustrated as being formed separately, but the parallel plate substrate 6 and the inclined portions 30 and 32 have a refractive index. They may be bonded with substantially the same adhesive or may be integrally formed.

(Example 2-2)
Example 2-2 of this embodiment will be described with reference to FIGS. FIG. 26 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The same components as those in Example 2-1 are denoted by the same reference numerals, and description thereof is omitted. The present embodiment is characterized in that the inclined portion 30 is removed from the lighting device 1 of Embodiment 2-1, and the inclined portion 32 is provided only on the incident surface SO side of the back surface of the parallel plate substrate 6 (inclined portion installation surface). have.

  Further, the incident surface SO is characterized in that the angle formed by the inclined portion installation surface and the incident surface SO is formed to be an obtuse angle. Here, an angle formed by a perpendicular drawn from the light exit surface of the parallel flat substrate 6 to the back surface and the incident surface SO is defined as an inclination angle β. Contrary to the above, it is possible to take a configuration in which the inclined portion 32 is removed while leaving the inclined portion 30. In that case, the incident surface SO is formed such that the angle formed by the incident surface SO and the light exit surface (inclined portion installation surface) of the parallel flat substrate 6 is an obtuse angle. As described above, this embodiment is characterized in that the inclined portion of the incident surface SO is on one of the light exit surface and the back surface of the parallel plate substrate 6.

  Next, the illumination operation of the illumination device 1 according to the present embodiment will be described with reference to FIG. FIG. 27 shows a state in which light emitted from the light source unit 34 is guided in the light guide unit 36. First, most of the light L5 incident on the light guide portion 36 is directed to the surface where the inclined portion 32 is not provided, but all of the light L5 is emitted from the light emission surface and the back surface of the parallel plate substrate 6. The tilt angle β is set so that the light L6 is totally reflected. Further, the inclination length l is set to a length that does not enter the inclined portion 32 when the light L5 is totally reflected and guided.

  Further, a part of the light L1 incident from the incident surface SO is directed to the inclined portion 32 as shown in the figure, but is totally reflected by the inclined surface 32a and after being totally reflected by the inclined surface 32a. The tilt angle α is set so that the light is totally reflected by the light exit surface 6 and the back surface 6. Thereafter, the light L2 totally reflected by the inclined surface 32a of the inclined portion 32 is guided as light L3 while repeating total reflection on the light exit surface and the back surface of the parallel plate substrate 6.

  In order to maximize the effects of the present embodiment, it is desirable that the inclination angle β and the inclination angle α are larger and the inclination length l is shorter. Therefore, each value is actually set so that the following relational expression is established. Hereinafter, a case where the refracted light L2 enters the inclined portion 32 as shown in FIG. 27 will be described as an example.

First, the incident light L1 from the light source unit 34 is incident on the incident surface SO at an incident angle β to (90 ° + β). When the refractive index of the light guide 36 is n, the incident light L1 is guided to the light guide 36 as a refracted light L2 having a refraction angle β to (90 ° + β−θ) according to the refractive index n on the incident surface SO. Is done. Here, the angle θ is an incident angle of the refracted light L2 incident on the inclined surface 32a when the inclination angle α = 0. Accordingly, when the light beam L1 is refracted by the incident surface SO at a refraction angle of (90 ° + β−θ) and enters the inclined surface 32a having the inclination angle α as the refracted light L2, the incident angle of the refracted light L2 on the inclined surface 32a is θ +
β-α. Then, the totally reflected light L3 reflected by the inclined surface 32a enters the light exit surface of the parallel plate substrate 6 at an incident angle θ + β-2α. Therefore, in order for the light L2 incident from the incident surface SO to be totally reflected by the inclined surface 32a and further totally reflected by the light exit surface and the back surface of the parallel plate substrate 6, the inclination angle α of the inclined portion 32 is Snell's From the law and total reflection conditions,
n · sin (θ + β-2α) ≧ 1 Equation (6)
Need to be satisfied.

Further, the inclination angle β is Snell so that the light L6 directed to the light emission surface of the parallel plate substrate 6 without the inclined portion 32 is totally reflected by the light emission surface and the back surface of the parallel plate substrate 6. From the law and total reflection conditions,
n · sin (θ−β) ≧ 1 Formula (7)
Need to be satisfied.
In addition, on the incident surface SO, from Snell's law and total reflection conditions,
n · sin (90−θ) = 1
・ N · cos (θ) = 1 (8)

Further, the incident light from the incident surface SO is inclined two or more times so that the reflected light of the light traveling toward the light exit surface of the parallel flat substrate 6 without the inclined portion 32 does not enter the inclined portion 32. In order to prevent the light from entering 32a, the inclination length l of the inclined portion 32 is determined by referring to FIG.
l≈h · tan (θ + β) −h · tan (β) (9)
Need to be satisfied.
Here, when the length of the incident surface SO is LSO,
LSO≈h / cos (β) + l · tan (α) (10)
It is.

  In this embodiment, acrylic resin (n = 1.49) is used as a material for forming the light guide section 34 as in the case of Example 2-1. The plate thickness of the parallel portion of the parallel plate substrate 6 is h = 10 mm. From equation (8), θ = 47.84 °. Therefore, β = 5.685 ° from the equation (7). Thus, the inclination angle α = 5.685 ° is obtained from the equation (6). Further, from the equations (9) and (10), the inclination length l≈12.5 mm and the length of the incident surface SO≈11.3 mm.

  Also in this embodiment, as in the case of Example 2-1, the opening width of the reflector 4 can be widened compared to the case of using a conventional parallel plate light guide plate, and the amount of light introduced into the light guide section 36 can be reduced. It can be increased by 9% compared with the conventional technology. Further, the leakage current can be reduced by separating the reflector 4 and the cold cathode tube 2 from the conventional one.

  In Examples 2-1 and 2-2, the inclined surfaces 30a and 32a are flat surfaces, but may be curved or multi-planar. However, in order to guide all light rays while repeating total reflection at the parallel flat plate portions beyond the inclined portions 30 and 32 of the light guide portion 36, the incident angle condition is satisfied for arbitrary light incident from the incident surface SO. It is necessary, and the inclination angle cannot be larger than the angle α in any part of the inclined surfaces 30 and 32.

  Further, in Examples 2-1 and 2-2, the structures of the inclined portions 30 and 32 are determined so that all the light rays do not enter the inclined portion more than twice. It is also possible to adopt a structure that does not enter more than three times. In this case, if the inclined surfaces 30a and 32a are formed as flat surfaces, the inclined length l can be increased to approximately twice that of the above embodiment.

Further, it is possible to determine the structure so that the inclination length l is increased and the light does not enter more than K times. The structure determination method in this case is the same as the method for determining the structure so as not to reflect three or more times. When the inclined surfaces 30a and 32a are formed in a plane, the inclination angle φ to be changed is the same as in Example 2-1. 2-
The inclination angle f of 2 may be approximately (1 / K) times, and the inclination length f to be changed may be approximately K times the inclination length l of Examples 2-1 and 2-2. Therefore, the relationship of φ · f≈α · l is established.

(Example 2-3)
Example 2-3 of this embodiment will be described with reference to FIG. FIG. 28 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The same components as those in Examples 2-1 and 2-2 are denoted by the same reference numerals, and the description thereof is omitted. The present embodiment is characterized in that the inclined portions 30 and 32 described in the embodiment 2-1 are provided at both end portions of the tendency plate-like substrate 6 made of transparent acrylic. Both end portions of the parallel plate substrate 6 are incident surfaces SO and SO ′, and light source portions 34 and 34 ′ are formed to face the two incident surfaces SO and SO ′, respectively. That is, inclined portions 30 and 32 and a light source portion 34 are formed on the left incident surface SO in the drawing, and inclined portions 30 ′ and 32 ′ and a light source portion 34 ′ are formed on the right incident surface SO ′ in the drawing. Yes.

  The light emitted from the light source unit 34 enters the light guide unit 36 from the incident surface SO and is guided while being totally reflected in the parallel plate substrate 6 by narrowing the light guide path by the inclined unit 30. Diffusion dots or reflective elements for extracting light from the light guide unit 36 toward the liquid crystal display panel FP on the light exit surface (or back surface) of the parallel flat substrate 6 and the light exit surface (or back surface) of the inclined surface 30a, Alternatively, a refractive element (both not shown) is provided. The light emitted from the light source 34 at one end of the light guide 36 and guided through the parallel plate substrate 6 to reach the other end has a structure in which the inclined portions 30 ′ and 32 ′ are opened in the traveling direction. Therefore, the light reaches the incident surface SO ′ while being totally reflected, a part of the light is reflected by the incident surface SO ′, and most of the remaining light is incident on the light source 34 ′ and is reflected by the reflector 4 ′ or the cold cathode tube 2 ′. After being reflected and scattered, the light enters the light guide 36 again from the incident surface SO ′. The optical action between the re-incident light and the inclined parts 30 ′ and 32 ′ is the same as the optical action between the light emitted from the light source part 34 ′ and the inclined parts 30 ′ and 32 ′. Propagates in the opposite direction with total reflection.

(Example 2-4 and its modifications)
Example 2-4 of this embodiment will be described with reference to FIG. FIG. 29 is a schematic cross-sectional view showing the illumination device 1 according to the present example disposed on the illuminated surface side of the liquid crystal panel FP. The same components as those in Examples 2-1 to 2-3 are denoted by the same reference numerals, and description thereof is omitted. The present embodiment is characterized in that the inclined portions 30 (or 32) described in the embodiment 2-2 are provided at both end portions of the tendency plate-like substrate 6 made of transparent acrylic. As in Example 2-3, both end portions of the parallel flat substrate 6 are incident surfaces SO and SO ′, and light source portions 34 and 34 ′ are formed to face the two incident surfaces SO and SO ′, respectively. An inclined portion 32 is formed on the back surface side of the parallel flat substrate 6 on the incident surface SO, and an inclined portion 32 ′ is formed on the back surface side of the parallel flat substrate 6 on the incident surface SO ′. The light guiding operation according to the present embodiment is the same as that described in Embodiments 2-2 and 2-3, and thus the description thereof is omitted.

  Next, a modification of the present embodiment will be described with reference to FIG. In the illuminating device 1 shown in FIG. 30, instead of the inclined portion 32 ′ on the incident surface SO ′ side shown in FIG. 29, an inclined portion 30 ′ is formed on the light exit surface side of the parallel flat substrate 6 on the incident surface SO ′. It has a feature in that. Even with such a configuration, the same light guiding operation as in Examples 2-2 and 2-3 can be obtained.

(Example 2-5 and its modifications)
Example 2-5 of the present embodiment will be described with reference to FIG. FIG. 31A is a plan view of the light guide unit 36 viewed from the liquid crystal display panel FP side. FIG. 31B shows a schematic cross section taken along line AA in FIG. 31A, and FIG. 31C shows a schematic cross section taken along line BB in FIG. The same components as those in Examples 2-1 to 2-4 are denoted by the same reference numerals, and the description thereof is omitted. The present embodiment is characterized in that the inclined portion structure described in Embodiment 2-3 with reference to FIG. 28 is formed on all four end sides of the parallel plate substrate 6. And four light source parts 34, 34 ', 34 ", 34'" are arrange | positioned facing four entrance planes SO, SO ', SO ", SO'". The light guiding operation according to the present embodiment is the same as that described in the above embodiments 2-1 to 2-4, and therefore the description thereof is omitted.

  Next, a modification of the present embodiment will be described with reference to FIG. FIG. 32A is a plan view of the light guide unit 36 viewed from the liquid crystal display panel FP side. FIG. 32B shows a schematic cross section cut along line AA in FIG. 32A, and FIG. 32C shows a schematic cross section cut along line BB in FIG. The illuminating device 1 according to this modification is characterized in that the inclined portion structure described in Embodiment 2-4 with reference to FIG. 29 is formed on all four end sides of the parallel plate substrate 6. . The inclined portions 30 and 30 ′ formed on the light emission surface side of the parallel plate substrate 6 and the inclined portions 32 and 32 ′ formed on the back surface side are alternately arranged around the parallel plate substrate 6. By doing so, it is possible to avoid the overlapping of the inclined portions at the four corners of the light guide 36.

  As described above with reference to the specific examples, according to the present embodiment, the reflector opening area, that is, the area of the incident surface SO of the light guide unit can be increased, so that the light use efficiency can be increased, and the high brightness. Can be realized. Moreover, since the flat part of a light guide part can be made thin, a low-cost, lightweight, and thin illuminating device can be implement | achieved.

  The illuminating device 1 according to the first and second embodiments is a liquid crystal display device having a liquid crystal display panel in which liquid crystal is sealed between two opposing substrates, and is disposed immediately below the illuminated surface of the liquid crystal display panel. It is suitable for use as a backlight type lighting device.

[Third Embodiment]
A visible light source (including a fluorescent discharge tube, or a fluorescent discharge tube and a reflector) used in the lighting apparatus according to the third embodiment of the present invention will be described with reference to FIGS. The present embodiment relates to a visible light source that emits visible light by causing ultraviolet light emitted by discharge emission of mercury or the like to enter a phosphor, and in particular, a cold cathode suitable as a light source of an illumination device for a liquid crystal display device Regarding the tube.

  As a light source of an illuminating device for a liquid crystal display device, a cold cathode tube in which a phosphor emitting light in three primary color bands is applied to the inner wall of a glass tube is used. FIG. 33 shows, for example, a part of the vicinity of the tube wall of the cross section in the tube axis direction of the cold cathode tube 510 mounted on the backlight unit shown in FIG. In the cold cathode tube 510, the phosphor 552 is dispersed in the binder 554 to form a layer, and is fixed to the inner wall of the glass tube 550 having an annular cross section perpendicular to the tube axis.

  The cold cathode tube 510 shown in FIG. 33 has the following two problems with respect to light loss (loss) in the phosphor 552 fixed to the inner wall of the glass tube 550. First, the light L1 emitted outward from the glass tube 550 will be described. The phosphor layer 558 has a smooth surface substantially parallel to the inner wall of the glass tube 550. A space filled with a discharge gas or a vacuum space 560 is formed between the phosphor layer 558 and the glass tube 550.

  When the light L1 passes through the space 560 and the glass tube 550 and exits outside the glass tube 550, a part of the light L2 is totally reflected at the interface between the phosphor layer 558 and the space 560 and enters the phosphor layer 558. I will return. Further, the light L3 that has passed through the region where the phosphor layer 558 and the glass tube 550 are in close contact with each other also undergoes total reflection at the interface between the glass tube 550 and the outside of the glass tube 550. Light rays returning to the inside of the phosphor layer 558 are absorbed by the phosphor 552, but since these return lights reach about 20% of the incident light intensity, the amount of light emitted to the outside of the glass tube 550 is reduced to a negligible level.

Next, the light beam L4 from the phosphor 552 toward the discharge gas layer 556 in the tube will be described. The surface of the phosphor layer 558 on the discharge gas layer 556 side has irregularities following the arrangement shape of the phosphor 552 having a diameter of about 3 to 10 μm, or the ratio of the phosphor 552 itself being exposed is high. Since reflection on the surface (particularly total reflection) does not occur, the light beam L4 is easily emitted to the discharge gas layer 556. However, the light beam L4 incident on the discharge gas layer 556 is partially absorbed in the discharge gas layer 556, and the amount of light emitted outside the glass tube 550 is reduced. As described above, the conventional cold cathode fluorescent lamps have a problem that the light emission efficiency that is so large that the amount of light absorbed in the tubes cannot be ignored cannot be obtained. An object of the present embodiment is to provide a discharge arc tube having excellent luminous efficiency by reducing light absorbed in the cold cathode tube.

The discharge arc tube according to the present embodiment is characterized first in that the inner surface of the phosphor layer facing the discharge gas layer in the tube is shaped so that the emitted light does not easily enter the discharge gas layer. Specifically, the surface on the discharge gas layer side is set to a flat surface having smooth curved irregularities of about 10 ⁻⁷ m or less. Since there is a high probability that light emitted to the discharge gas layer side is totally reflected at the interface between the discharge gas layer and the phosphor layer, it is possible to reduce light absorption in the discharge gas layer.

The second feature is that the outer surface of the phosphor layer facing the inner wall of the glass tube is shaped so that the emitted light is easily emitted outside the tube. Specifically, the probability that the phosphor is exposed on the outer surface of the phosphor layer facing the inner wall of the glass tube, and the light beam going out of the tube is totally reflected at the interface between the phosphor layer and the space or the outer wall of the glass tube. Reduce.
Alternatively, the surface of the phosphor layer facing the inner wall of the glass tube is formed with an uneven surface that substantially follows the shape of the phosphors and their arrangement by the binding material that fixes the phosphors. Thereby, the probability that the light beam going out of the tube is totally reflected at the interface between the phosphor layer and the space or the outer wall of the glass tube can be reduced.

  Third, the phosphor layer is formed on the outer wall of the glass tube. By forming the phosphor layer on the outer wall of the glass tube, the phosphor layer on the ultraviolet incident side can be easily formed flat with a smooth curved surface.

  The fourth feature is that the surface accuracy of the surface of the phosphor layer facing the discharge gas layer is about the visible light wavelength. As a result, light scattering at the interface between the discharge gas layer and the phosphor layer can be reduced to reduce the return light from the phosphor layer to the discharge gas layer.

  Fifth, the phosphor layer and the ultraviolet ray source are separated, and the visible light source is characterized in that an uneven surface is provided on the side from which visible light is emitted. Specifically, it is a visible light source composed of an ultraviolet light source and a phosphor layer, and has a structure for extracting visible light converted by the phosphor layer from one surface of the phosphor layer. The surface to be taken out has an uneven surface reflecting the shape of the phosphor.

Sixth, the visible light source is characterized in that the phosphor surface facing the ultraviolet light source is flattened. Specifically, the surface close to the ultraviolet ray source of the phosphor layer has irregularities of about 10 ⁻⁷ m or less.

Hereinafter, the visible light source according to the present embodiment will be described more specifically using examples.
(Example 3-1)
Example 3-1 of the present embodiment will be described with reference to FIGS. FIG. 34 shows a cross section perpendicular to the tube axis of the cold cathode fluorescent lamp according to Example 3-1. The cold cathode tube 50 includes a transparent outer tube 52 made of hard glass having an outer diameter of 2.8 mm and an inner diameter of 2.6 mm, for example, and a transparent inner tube 58 made of quartz having an outer diameter of 2.4 mm and an inner diameter of 2.0 mm, for example. Are combined. A phosphor layer 56 is formed on the outer wall of the inner tube 58. The phosphor layer 56 includes a phosphor 62 and a binding material 64 for dispersing and holding them. A cavity is formed in the inner tube 58, and a discharge gas is enclosed in the cavity to form a discharge gas layer 60.
In the present embodiment, the phosphor layer 56 is bonded to the outer wall of the inner tube 58, and the bonded surface is flat with a smooth curved surface. For this reason, the discharge gas layer 60 side of the phosphor layer 56 is formed flat. On the other hand, the outer surface of the phosphor layer 56 opposite to the discharge gas layer 60 is not in contact with the inner wall surface of the outer tube 52, and the phosphor 62 is exposed on the outer surface of the phosphor layer 56. Therefore, the outer surface of the phosphor layer 56 has an uneven surface that substantially follows the radius of the phosphor 62 (about 1.5 to 5 μm) and the arrangement shape of the phosphor 62.

  The phosphor layer 56 according to the present embodiment is formed as follows. First, a phosphor coating solution is prepared. This is a solution obtained by dissolving a binder (water glass) 64 in a volume ratio of 5% with respect to the phosphor 62 in a solvent obtained by adding 0.6% (weight%) of ammonium polymethacrylate to water. It is. This coating solution is allowed to flow along the outer wall surface of the vertically placed quartz tube (inner tube 58), and after the quartz tube is baked, the phosphor layer 56 is dried with hot air.

  When the internal structure of the phosphor layer 56 formed in this way is observed, the binder material 64 enters between a large number of generally spherical phosphors 62 to form a dense film. In the example, there is not enough binding material 64 to fill the gaps in phosphor 62. For this reason, minute irregularities on the surface of the quartz tube (inner tube 58) serve as the core of film formation, and water glass accumulates from there, resulting in a dense film at the interface with the quartz tube. However, as the distance from the quartz tube surface increases, the water glass becomes insufficient, and the water glass is not sufficiently buried between the phosphors 62. As a result, the surface of the phosphor layer 62 that is not in contact with the quartz tube is formed with an uneven surface on the order of several μm that directly reflects the outer shape of the phosphor 62 and the arrangement thereof.

  FIG. 35 shows a part of the vicinity of the tube wall of the cross section in the tube axis direction of the cold cathode tube 50 of the present embodiment. The light guide path of the emitted light by the cold cathode tube 50 will be described with reference to FIG. A space 54 is formed between the surface of the phosphor layer 56 opposite to the discharge gas layer 60 and the inner wall of the outer tube 52, and refracted light L1 of light incident from the space 54 to one point P on the inner wall surface of the outer tube 52. Are guided through the outer tube 52 having a refractive index larger than that of the space 54 and are all emitted from the outer wall surface of the outer tube 52.

  Next, the light beam that travels from the phosphor 62 toward the inner wall of the outer tube 52 will be described. On the surface of the phosphor layer 56 on the inner wall side of the outer tube 52, the phosphor 62 and an uneven surface following the arrangement shape thereof are formed, and there are also places where the phosphor 62 itself is exposed (not shown). Therefore, reflection on the surface of the phosphor layer 56 on the inner wall side of the outer tube 52 is difficult to occur, and the light beam L2 is easily emitted to the outer tube 52. In this region, since the emitted light substantially parallel to the inner wall of the outer tube 52 is totally reflected at the interface with the space 54 like the light beam L3, the light can be emitted out of the outer tube 52 with high efficiency. .

  Next, light traveling toward the discharge gas layer 60 will be described. The phosphor layer 56 has a smooth surface substantially parallel to the inner wall of the inner tube 58. Accordingly, a part of the light emitted from the phosphor 62 is totally reflected at the interface between the phosphor layer 56 and the inner tube 58 and returned to the phosphor layer 56 side as returned light L4. Next, the light incident on the inner tube 58 is further totally reflected at the interface between the inner tube 58 and the discharge gas layer 60 and returned as return light L5. In this way, only a part L 6 of the light emitted from the phosphor 62 toward the discharge gas layer 60 is incident on the discharge gas layer 60.

  Thus, according to the present embodiment, the inner surface of the phosphor layer 56 facing the discharge gas layer 60 in the inner tube 58 is flattened, so that the light emitted to the discharge gas layer 60 side is the interface with the inner tube 58. Therefore, it is possible to increase the probability of total reflection at the interface between the inner tube 58 and the discharge gas layer 60, and to reduce light absorption in the discharge gas layer 60. In addition, since the phosphor layer 56 is formed on the outer wall of the inner tube 58, the phosphor layer 56 on the ultraviolet incident side can be easily formed flat.

In addition, according to the present embodiment, the phosphor 62 is exposed on the outer surface of the phosphor layer 56 facing the inner wall of the outer tube 52, or the uneven surface substantially following the shape of the phosphor 62 and the arrangement shape thereof is formed on the phosphor layer 56. Since it is formed on the outer surface, it is possible to reduce the probability that a light beam traveling outward from the outer tube 52 is totally reflected by the interface between the phosphor layer 56 and the space 54 or by the space 54 and the inner and outer walls of the outer tube 52.

Further, in the present embodiment, the surface accuracy of the surface of the phosphor layer 56 facing the discharge gas layer 60 is made uneven so as to be about the visible light wavelength, for example, about 10 ⁻⁷ m or less. As a result, light scattering at the interface between the discharge gas layer 60 and the phosphor layer 56 can be reduced, and the return light from the phosphor layer 56 to the discharge gas layer 60 can be reduced.

  Table 1 shows a comparison of light transmission, absorption, and reflection amounts in each part of the cold cathode tube 50 according to this embodiment and the conventional cold cathode tube. As is apparent from Table 1, it can be seen that the cold cathode tube according to the present example is superior in any of visible light transmittance, absorption rate, and reflectance.

(Example 3-2)
Example 3-2 of the present embodiment will be described with reference to FIGS. FIG. 36 shows a cross section orthogonal to the tube axis of the ultraviolet light source, which is a visible light source according to Example 3-2. As an ultraviolet ray source, a mercury discharge tube 72 using a quartz tube as a bulb is used. The outer diameter of the mercury discharge tube 72 is 2.6 mm, and the inner diameter is 2.0 mm. The periphery of the mercury discharge tube 72 is covered with a concave mirror 74 made of aluminum except for a part of the opening region. The cross section of the mirror surface of the concave mirror 74 is a semicircle having a radius r = 4 mm from the point P at the tip of the mercury discharge tube 72. An injection filter 76 made of hard glass is attached to the opening of the concave mirror 74.

FIG. 37 is a diagram showing the configuration of the injection filter 76 in more detail. In FIG. 37, a phosphor layer 78 is provided on the surface of the hard glass substrate 82 on the mercury discharge tube 72 side, and an ultraviolet reflecting film 82 is provided on the opposite surface.
A large number of phosphors 86 are immobilized on the phosphor layer 78 via binders 88. Further, the phosphor layer 78 is in contact with the hard glass substrate 80 with an uneven surface through the space 84. The uneven surface is formed by exposing phosphor particles (diameter: 3 μm to 10 μm).

  The phosphor layer 78 according to the present embodiment is formed as follows. First, a phosphor coating solution is prepared. This is a solution obtained by dissolving a binder (water glass) 88 in a volume ratio of 35% with respect to a phosphor 86 in a solvent obtained by adding 0.6% (weight%) of ammonium polymethacrylate to water. It is. On the other hand, a water repellent material is formed on the phosphor-coated surface of the hard glass substrate 80. The film forming material is metal fluoride (in this example, magnesium fluoride is used). Using a pulling method, a coating solution is applied to the phosphor-coated surface of the hard glass substrate 80, and after baking the hard glass substrate 80, the phosphor film 88 is dried with hot air.

When the internal structure of the phosphor layer 78 formed in this way is observed, the binder substance 88 is inserted between the phosphors 86 having a substantially spherical shape to form a dense film. Compared with the phosphor layer 56 in Example 3-1, the amount of water glass is large, and the gap between the phosphors 86 is sufficiently reached to form a dense film. However, since the surface of the hard glass substrate 80 is formed with a water-repellent substance, a portion where the phosphor layer 78 film surface is not in contact with the surface of the hard glass substrate 80 is formed as a result of the coating liquid not being sufficiently wetted. . In a portion not in contact with the surface of the hard glass substrate 80, an uneven surface reflecting the outer shape and arrangement shape of the phosphor 86 is generated.

Thus, in the present embodiment, unlike the embodiment 3-1, the phosphor layer 78 and the mercury discharge tube 72 are separated. The phosphor layer 78 is disposed so that the uneven surface faces the visible light emission side. On the other hand, the surface of the phosphor layer 78 facing the mercury discharge tube 72 is a flat surface having irregularities of about 10 ⁻⁷ m or less. Thereby, the emitted light can be obtained with high efficiency in the same manner as in Example 3-1.

(Example 3-3)
Example 3-3 of this embodiment will be described with reference to FIGS. FIG. 38 shows a cross section orthogonal to the tube axis of the ultraviolet light source, which is a visible light source according to this embodiment. As an ultraviolet ray source, a mercury discharge tube 90 similar to that in Example 3-2 using a quartz tube as a bulb is used. An aluminum mirror 92 having a U-shaped cross section is provided around the mercury discharge tube 90. The light guide plate 100 is fixed to the opening of the aluminum mirror 92 through the ultraviolet reflecting film 102. A phosphor layer 94 is formed on the surface of the U-shaped reflecting surface facing the opening. As shown in FIG. 39, the phosphor layer 94 is formed in close contact with the surface of the aluminum mirror 92, and a large number of phosphors 86 are fixed via a binder 88. Further, the surface opposite to the surface of the aluminum mirror 92 is an uneven surface having unevenness of 5 to 10 μm. The phosphor layer 94 of this example is formed by the method disclosed in Example 3-1.

A phosphor layer 94 is also formed on part of the outer surface of the mercury discharge tube 90. The phosphor layer 94 on the outer surface of the mercury discharge tube 90 is formed between the intersections with the outer diameter of the perpendicular drawn from the upper and lower corners of the U-shaped aluminum mirror 92 to the outer diameter of the mercury discharge tube 90. FIG. 40 shows a part of the phosphor layer 94 on the outer surface of the mercury discharge tube 90. The phosphor layer 94 on the outer surface of the mercury discharge tube 90 has the same configuration as the phosphor layer 94 on the surface of the aluminum mirror 92.
The light from the phosphor layer 94 on the outer surface of the mercury discharge tube 90 does not enter the phosphor layer 94 formed on the aluminum mirror 92, and the amount of visible light is reduced by reducing the light incident on the phosphor layer 94 more than once. Loss (20% loss per incident) can be suppressed, and high power-visible light conversion efficiency can be obtained.

  Table 2 shows a comparison between the light emission rate according to this embodiment and the conventional example. As is clear from Table 2, it can be seen that the visible light source of this example is superior in overall efficiency. The efficiency generated in principle when converting from ultraviolet light to visible light is not included in the numerical value because both are the same.

The lighting device according to the first embodiment described above can be summarized as follows.
(Appendix 1)
A plurality of light guide plates arranged on the illuminated surface side of the display panel;
An illuminating device, comprising: an arc tube disposed between the plurality of light guide plates and disposed on a back side of a light exit surface of the light guide plate on the illuminated surface side.

(Appendix 2)
In the lighting device according to attachment 1,
A light reflecting member is provided on the opposite side of the surface to be illuminated with respect to the arc tube.

(Appendix 3)
In the lighting device according to attachment 1 or 2,
A light scattering element is disposed between the illuminated surface between the light guide plates and the arc tube.

(Appendix 4)
In the lighting device according to attachment 3,
The illuminating device, wherein the light scattering element is an anisotropic scatterer having different diffusivity depending on the incident direction of light.

(Appendix 5)
In the lighting device according to any one of appendices 1 to 4,
A lighting device, wherein a reflecting plate is disposed between the illuminated surface between the light guide plates and the arc tube.

(Appendix 6)
In the lighting device according to any one of appendices 1 to 5,
The light incident surface of the end portion of the light guide plate has an obtuse angle with the back surface of the light guide plate.

(Appendix 7)
In the illumination device according to appendix 6,
The light guide plate is formed of a transparent member having a refractive index n = 1.41 or more,
The obtuse angle is in a range of more than 90 ° and not more than 102 °.

(Appendix 8)
In the lighting device according to any one of appendices 1 to 7,
An illumination device, wherein a diffusion element is provided on a surface of the light guide plate.

(Appendix 9)
In the lighting device according to attachment 8,
The diffusing element is a plurality of diffusing patterns provided on the back surface of the light guide plate.

(Appendix 10)
In the lighting device according to attachment 8,
The diffusing element is a plurality of concavo-convex portions having a triangular cross section formed on the back surface of the light guide plate.

(Appendix 11)
The lighting device according to any one of appendices 8 to 10,
A lighting device comprising: a second light guide plate having a close contact portion that is optically in close contact with the surfaces of the plurality of light guide plates.

(Appendix 12)
In the lighting device according to attachment 11,
The illuminating device, wherein the diffusing element is provided in the second light guide plate instead of the plurality of light guide plates.

  The illumination device according to the second embodiment described above can be summarized as follows.

(Appendix 13)
A transparent parallel plate substrate;
Provided in the vicinity of the incident surface of the substrate side end portion where the light emitted from the light source is incident, an inclined surface having an upward slope from the substrate surface toward the incident surface, and light incident from the incident surface is the inclined surface. And an inclined portion having an inclination angle α set so as to be totally reflected and then totally reflected in the substrate.

(Appendix 14)
In the lighting device according to attachment 13,
The inclination angle α is
n · sin (θ-2α) ≧ 1
A lighting device characterized by satisfying
However,
θ: incident angle of light incident on the inclined surface when the inclination angle α = 0, n: refractive index of the inclined portion.

(Appendix 15)
In the lighting device according to attachment 13 or 14,
The length of the inclined surface (inclined length l) in a cross section cut by a plane perpendicular to both the inclined surface and the substrate surface so that incident light from the incident surface does not enter the inclined surface more than a predetermined number of times. A lighting device characterized by being set.

(Appendix 16)
In the lighting device according to attachment 13,
The inclined portion is provided in the vicinity of the incident surface of the installation surface of either the light exit surface of the substrate or the back surface facing it.
The illuminating device, wherein the incident surface is formed such that an angle formed by the incident surface and the installation surface is an obtuse angle.

(Appendix 17)
In a liquid crystal display device having a liquid crystal display panel in which liquid crystal is sealed between two opposing substrates, and an illumination device provided on an illuminated surface of the liquid crystal display panel,
The said illuminating device is an illuminating device described in any one of Additional remarks 1 thru | or 16. The liquid crystal display device characterized by the above-mentioned.

The visible light source according to the third embodiment described above can be summarized as follows.
(Appendix 18)
A transparent member with a cavity;
A discharge gas layer enclosed in the cavity;
A visible light source comprising: a phosphor layer formed flat on the discharge gas layer side.

(Appendix 19)
A transparent member with a cavity;
A discharge gas layer enclosed in the cavity;
A visible light source comprising: a phosphor layer including a phosphor and a binder, and having a concavo-convex surface substantially following the arrangement shape of the phosphor on a side opposite to the discharge gas layer.

(Appendix 20)
A transparent member with a cavity;
A discharge gas layer enclosed in the cavity;
A phosphor layer including a phosphor and a binding material, the discharge gas layer side being formed flat, and an uneven surface substantially following the arrangement shape of the phosphor formed on the opposite side of the discharge gas layer. Visible light source characterized by

(Appendix 21)
In the visible light source according to any one of appendices 18 to 20,
The visible light source, wherein the phosphor layer is formed on an outer wall of the transparent member.

(Appendix 22)
In the visible light source according to any one of appendices 18 to 20,
The visible light source, wherein the phosphor layer is disposed apart from the transparent member.

It is a schematic sectional drawing which shows the outline of the basic composition of the illuminating device by the 1st Embodiment of this invention, and shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-1 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-2 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-3 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is the elements on larger scale near the cold-cathode tube 2c of the illuminating device by Example 1-3 in 1st Embodiment of this invention. It is the elements on larger scale near the cold-cathode tube 2c of the illuminating device which concerns on the modification of Example 1-3 in 1st Embodiment of this invention. It is the elements on larger scale near the cold cathode tube 2c of the illuminating device which concerns on the other modification of Example 1-3 in 1st Embodiment of this invention. It is an illuminating device by Example 1-4 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is the elements on larger scale near the cold-cathode tube 2c of the illuminating device by Example 1-4 in 1st Embodiment of this invention. It is the elements on larger scale near the cold-cathode tube 2c of the illuminating device by Example 1-4 in 1st Embodiment of this invention. It is an illuminating device which concerns on the modification of Example 1-4 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-5 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-6 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is the elements on larger scale of the cold cathode tube 2c vicinity of the illuminating device by Example 1-6 in 1st Embodiment of this invention. It is the elements on larger scale of the cold cathode tube 2c vicinity of the illuminating device by Example 1-6 in 1st Embodiment of this invention. It is an illuminating device which concerns on the modification of Example 1-6 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device which concerns on the other modification of Example 1-6 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is the elements on larger scale near the cold cathode tube 2c of the illuminating device shown in FIG. It is the elements on larger scale near the cold-cathode tube 2c of the illuminating device which concerns on the further another modification of Example 1-6 in 1st Embodiment of this invention. It is an illuminating device by Example 1-7 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is a figure explaining the difference in the way of the diffusion of the emitted light with the triangular recessed part 26 of the illuminating device 1 by Example 1-7 in 1st Embodiment of this invention, and the diffusion pattern 10. FIG. It is an illuminating device by Example 1-8 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 1-9 in 1st Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 2-1 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is a figure explaining the illumination operation of the illuminating device by Example 2-1 in the 2nd Embodiment of this invention. It is an illuminating device by Example 2-2 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is a figure explaining the illumination operation of the illuminating device by Example 2-2 in the 2nd Embodiment of this invention. It is an illuminating device by Example 2-3 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 2-4 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by the modification of Example 2-4 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by Example 2-5 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is an illuminating device by the modification of Example 2-5 in the 2nd Embodiment of this invention, Comprising: It is a schematic sectional drawing which shows the state arrange | positioned at the to-be-illuminated surface side of liquid crystal panel FP. It is a figure which shows a part of tube wall vicinity of the cross section of the tube axis direction of the conventional cold cathode tube. It is a figure which shows the cross section orthogonal to the tube axis of the cold cathode tube by Example 3-1 in the 3rd Embodiment of this invention. It is a figure which shows a part of tube wall vicinity of the cross section of the tube-axis direction of the cold cathode tube by Example 3-1 in the 3rd Embodiment of this invention. It is a figure which shows the cross section orthogonal to the tube axis | shaft of the ultraviolet light source of the visible light source by Example 3-2 in the 3rd Embodiment of this invention. It is a figure which shows in more detail the structure of the emission filter 76 of the visible light source by Example 3-2 in the 3rd Embodiment of this invention. It is a figure which shows the cross section orthogonal to the tube axis | shaft of the ultraviolet light source of the visible light source by Example 3-3 in the 3rd Embodiment of this invention. It is a figure which shows the fluorescent substance layer 94 vicinity by the side of the aluminum mirror 92 by Example 3-3 in the 3rd Embodiment of this invention in detail. It is a figure which shows the fluorescent substance layer 94 vicinity by the side of the mercury discharge tube 90 by Example 3-3 in the 3rd Embodiment of this invention in detail. It is a schematic sectional drawing which shows schematic structure of the conventional illuminating device of a direct type. It is a schematic sectional drawing which shows schematic structure of the conventional illuminating device of a sidelight system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illuminating device 2a-2f, 50 Cold cathode tube 4a-4e Reflector plate 6a-6e Light guide plate 8, 9, 12 Diffuser plate 10 Diffusion pattern 14, 16 Reflector plate 18 Light incident surface 20 2nd light guide plate 22 Optical joining resin layer 24 Recessed portion 26 Triangular recessed portion 28 Reflective polarizing plate 30, 32 Inclined portion 34 Light source portion 36 Light guide portion 52 Outer tube 54 Spaces 56, 78, 94 Phosphor layer 58 Inner tube 60 Discharge gas layers 62, 86, 96 Phosphor 64, 88, 98 Binder 70 Visible light source 72, 90 Mercury discharge tube 74 Concave mirror 76 Eject filter 80, 102 UV reflection film 82 Hard glass substrate 84 Space 92 Aluminum mirror 100 Light guide plate FP Flat panel (liquid crystal panel)

Claims (10)

A plurality of light guide plates arranged on the illuminated surface side of the display panel;
An illuminating device, comprising: an arc tube disposed between the plurality of light guide plates and disposed on a back side of a light exit surface of the light guide plate on the illuminated surface side. The lighting device according to claim 1.
A light reflecting member is provided on the opposite side of the surface to be illuminated with respect to the arc tube. The lighting device according to claim 1 or 2,
The light incident surface of the end portion of the light guide plate has an obtuse angle with the back surface of the light guide plate. The lighting device according to claim 3,
The light guide plate is formed of a transparent member having a refractive index n = 1.41 or more,
The obtuse angle is in a range of more than 90 ° and not more than 102 °. In the illuminating device of any one of Claims 1 thru | or 4,
An illumination device, wherein a diffusion element is provided on a surface of the light guide plate. The lighting device according to claim 5.
The diffusing element is a plurality of concavo-convex portions having a triangular cross section formed on the back surface of the light guide plate. A transparent parallel plate substrate;
Provided in the vicinity of the incident surface of the substrate side end portion where the light emitted from the light source is incident, an inclined surface having an upward slope from the substrate surface toward the incident surface, and light incident from the incident surface is the inclined surface. And an inclined portion having an inclination angle α set so as to be totally reflected and then totally reflected in the substrate. The lighting device according to claim 7.
The inclination angle α is
n · sin (θ-2α) ≧ 1
A lighting device characterized by satisfying
However,
θ: incident angle of light incident on the inclined surface when the inclination angle α = 0, n: refractive index of the inclined portion. A transparent member with a cavity;
A discharge gas layer enclosed in the cavity;
A visible light source comprising: a phosphor layer formed flat on the discharge gas layer side. The visible light source according to claim 9,
The visible light source, wherein the phosphor layer is formed on an outer wall of the transparent member.