JP2006236749A - Light source device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of corresponding to a solid color too while having good color reproducibility, even when a white color light source to emit white color light having low color rendering property is used. <P>SOLUTION: An internally illuminated signboard 1 has a display panel 3 on which information such as characters and illustrations is printed as a sign image 2 on its surface, and a backlight device 4 disposed on the back side of this display panel 3 to project the sign image 2 by irradiating light at night. In the backlight device 4, a filter layer 11 for correcting color rendering properties to make spectral intensity in respective wavelength regions of blue, green, and red in emitted light from a light emitting surface 75 almost constant by absorbing optical components in a prescribed wavelength region among respective wavelength regions of blue, green, and red in the emitted light from a white light emitting diode 6 is formed on the light emitting surface 75 of a light guide plate 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface light source device used as a backlight device or the like in an internally illuminated signboard or a liquid crystal display device, and a display device using the surface light source device as a backlight device. More specifically, the present invention relates to a technique for improving the color rendering properties of white light emitted from a surface light source device.

  Display devices such as internally illuminated signboards and liquid crystal display devices generally include a display panel and a backlight device that irradiates light from the back side of the display panel. The backlight device includes a white light source such as a cold cathode discharge tube, a halogen lamp, and a metal halide lamp, and a light guide plate disposed opposite to the back side of the display panel. Light emitted from the white light source is transmitted to the light guide plate. After entering, the light is emitted from the surface (emitting surface) facing the display panel while traveling through the light guide plate toward the back side of the display panel.

  Among such display devices, an internally illuminated signboard uses a display panel in which a color sign image is formed on the surface of a transparent base material by printing or the like, and reflects a daylight to display a color image. At night, a white image incident on the display panel transmits a sign image to display a color image. On the other hand, in a liquid crystal display device, a liquid crystal panel (display panel) in which liquid crystal is held between a pair of substrates on which liquid crystal driving transparent electrodes are formed is used, and an electric field is applied to the liquid crystal between the pair of substrates. By controlling the orientation of the liquid crystal for each pixel, the external light or the light incident from the backlight device is modulated for each pixel. At that time, the display light is colored by the red, green, and blue color filters formed in each pixel to display a color image.

Here, in recent years, it has been proposed to use a white light-emitting diode as a white light source, and such a white light-emitting diode has an advantage of being small in size, high in luminance, and low in driving voltage (for example, patents). References 1 and 2).
Utility Model Registration No. 3095940 JP 2002-244122 A

  However, the emitted light from the white light emitting diode generally has a spectral intensity around 468 nm in the blue wavelength region, and a spectral intensity around 518 nm in the green wavelength region, as shown in FIG. In addition, since it is very large compared to the spectral intensity around 635 nm which is the red wavelength region, even if it is white light, the color rendering is low, such as being actually bluish. Therefore, when a color image is displayed using the light emitted from the white light emitting diode, it is difficult to predict the color of the displayed color image, for example, an image that is more bluish than the predicted color is displayed. There is. Further, there is a problem in that an image displayed using external light and an image displayed using light emitted from the backlight device are different in color even though they are the same color image.

  In view of the above problems, an object of the present invention is to provide a light source device capable of obtaining good color reproducibility even when a white light source with low color rendering properties is used, and a display device using the light source device. There is to do.

  In order to solve the above problems, in the present invention, in the surface light source device including a white light source and a light guide plate that emits light from the white light source and is emitted from the light exit surface, the white light source At least one part of the light path from the light guide plate to the light exit surface of the light guide plate partially absorbs a light component in a predetermined wavelength region of the visible light region included in the exit light from the white light source and exits from the light exit surface. A color rendering correction filter means for leveling the relative intensity of the spectrum distribution curve of the emitted light is arranged.

  In the present invention, a display panel capable of displaying a color image in a transmission mode, a white light source, and a light guide plate from which light emitted from the white light source is incident and emitted from the light exit surface toward the back side of the display panel And a backlight device comprising: a light component in a predetermined wavelength region of a visible light region included in light emitted from the white light source at least at one position of an optical path from the white light source to the display panel. Color rendering property correction filter means for leveling the relative intensity of the spectrum distribution curve of the light emitted from the light exit surface by partially absorbing the light is disposed.

  In the present invention, when the white light source is a white light emitting diode, the color rendering correction filter means is a blue component absorption filter capable of absorbing a part of a blue component, that is, a yellow color having a complementary color relationship with blue. Configured as a filter. That is, the light emitted from the white light emitting diode generally has a spectral intensity around 468 nm in the blue wavelength region, compared with a spectral intensity around 518 nm in the green wavelength region and a spectral intensity around 635 nm in the red wavelength region. Therefore, it is only necessary to absorb a part of the blue component of the three primary colors (red, green, and blue) of light and level the spectral intensities of the three primary colors to improve color rendering.

  The present invention uses an image displayed using external light and light emitted from a backlight device when the display panel can display a color image even in a reflection mode using external light. Thus, there is an advantage that a color image having the same quality as the displayed image can be displayed.

  In the present invention, the backlight device may include a reflective surface on the side opposite to the light exit surface of the light guide plate. In this case, the color rendering correction filter means includes the white light source and the light guide plate. , Between the reflecting surface and the light guide plate, and between the light guide plate and the display panel.

  In the present invention, the color rendering property correction filter means includes a colored film that can partially absorb the light component in the predetermined wavelength region and a colored coating layer layer that includes a color material that partially absorbs the light component in the predetermined wavelength region. Can be configured. When the latter is adopted, there is an advantage that the number of parts can be reduced when the display device is assembled.

  In the present invention, the light guide plate is printed with a large number of dots for correcting the light quantity distribution of the emitted light from the light emitting surface, and the large number of dots are formed on the ink forming the dots with light in the predetermined wavelength region. It is preferable that the color rendering property correction filter unit is configured by including a color material that partially absorbs the components. With this configuration, it is possible to configure the color rendering property correction filter means simply by changing the ink components used to form the dots.

  In the present invention, when the display device is an internally illuminated signboard, the display panel is formed by printing predetermined information on a transparent substrate in color. On the other hand, when the display device is a liquid crystal display device, the display panel is a liquid crystal panel in which liquid crystals are held between a pair of substrates on which liquid crystal driving transparent electrodes are formed. By applying an electric field to the liquid crystal for each pixel and controlling the alignment of the liquid crystal between each substrate, external light or light incident from the backlight device is modulated by each pixel equipped with a color filter to display a color image To do.

  In the present invention, the spectral distribution curve of the emitted light from the light exit surface of the light guide plate is partially absorbed by the color rendering property correction filter by the light component in the predetermined wavelength region of the emitted light from the white light source whose spectral distribution is not flat. Since the relative intensity of the color is leveled, color rendering can be improved. That is, even when the white light source is a white light emitting diode and the spectral intensity in the blue wavelength region of the emitted light is larger than the spectral intensity in the green wavelength region and the red wavelength region, the three primary colors of light (red, green, blue) Can be leveled. Therefore, even when the color rendering property of the emitted light from the white light source is low, an image can be displayed using white light having a high color rendering property, so that a color image with excellent color reproducibility can be displayed. Even when such an improvement is made, it is only necessary to add a color rendering correction filter, so that there is no significant increase in cost.

  An example of a surface light source device and a display device to which the present invention is applied will be described with reference to the drawings.

[Application example for internally illuminated signboards]
(overall structure)
1A and 1B are respectively a front view and a longitudinal sectional view showing an internally illuminated signboard (display device) to which the present invention is applied. FIGS. 2A and 2B are an explanatory diagram showing an enlarged cross section of the internally illuminated signboard of FIG. 1 and an explanatory diagram showing a schematic configuration of a backlight device used for the internally illuminated signboard.

  As shown in FIGS. 1 (a) and 1 (b), an internally illuminated signboard 1 has a display panel 3 in which information such as letters and illustrations is screen-printed on a transparent substrate 30 as a color sign image 2, The display panel 3 has a backlight device 4 (surface light source device) that is disposed on the back side of the display panel 3 and projects a sign image 2 by irradiating light at night or the like. The illuminated signboard 1 has two struts 51 and 52 that are upright with their lower end portions buried in the ground, and two horizontal members 53 that are horizontally stretched between the struts 51 and 52. 54. A solar module unit 56 is attached to the upper ends of the two columns 51 and 52, and power can be supplied to the internally illuminated signboard 1. A control box 57 is installed at a side position of the column 51, and the operation of the internally illuminated signboard 1 is controlled by a control panel (not shown) configured inside the column. The control panel can be configured as a sequence control mechanism or the like. For example, during bright hours during the day, the power supplied from the solar module unit 56 is driven and controlled to be stored in a battery (not shown), while at night or the like. In the dark time zone, the drive control is performed so that the power stored in the battery is supplied to the backlight device 4 and the sign image 2 of the display panel 3 is irradiated from the back side.

  As the display panel 3, a well-known one can be used, and detailed description thereof will be omitted. However, a transparent plate material such as polyethylene terephthalate or polypropylene obtained by screen-printing the sign image 2 on a transparent film such as polyethylene terephthalate or polypropylene. In this case, the transparent film and the transparent plate material constitute the transparent substrate 30 of the display panel 3. In addition, as the display panel 3, a screen obtained by directly printing the signature image 2 on a transparent plate material can be used. In this case, the transparent plate material constitutes the transparent base material 30 of the display panel 3.

  As shown in FIGS. 2A and 2B, the backlight device 4 includes a plurality of white light emitting diodes 6 (white light sources) arranged in two upper and lower stages, and light emitted from the white light emitting diodes 6 vertically. The light guide plate 7 is incident from the end surfaces 71 and 72 of the first and second surfaces. The light guide plate 7 is opposed to the back surface of the display panel 3 at a predetermined interval, and a large number of light scattering dots 8 for reducing luminance unevenness are formed on the light emitting surface 75 thereof. . Further, in the light guide plate 7, the opposite surface 76 is formed with unevenness 761 that travels while reflecting incident light and emits the light toward the display panel, and the reflection plate 9 (reflection surface) is overlapped. Are arranged. The reflection plate 9 reuses light leaked from the light guide plate 7 and is formed of, for example, a single layer film or a multilayer film of aluminum, aluminum alloy, silver, silver alloy or the like on the inner surface of the substrate 91. What formed the light reflection layer 92 can be used.

  The white light emitting diodes 6 are arranged along the upper and lower end surfaces 71 and 72 of the light guide plate 7 at intervals of 1 cm, for example, and light incident on the light guide plate 7 from the end surfaces 71 and 72 is reflected inside the light guide diodes 7. The light travels and is emitted as planar light from the light exit surface 75 of the light guide plate 7 toward the back surface of the display panel 3.

  The light guide plate 7 is made of PMMA (polymethyl methacrylate) having a very high light transmittance, and has a plate shape with a thickness of about 1 cm. The upper and lower end surfaces 71 and 72 on which the light emitted from the white light emitting diode 6 is incident are cut into, for example, a V shape, thereby forming a recess for housing the white light emitting diode 6, and the light guide plate The light that travels straight through 7 is reflected by the V-shaped portion to prevent light leakage at the end faces 71 and 72.

  The scattering dots 8 on the light exit surface 75 of the light guide plate 7 are for reducing luminance unevenness on the light exit surface 75, and are formed by screen printing white ink in the form of dots in this embodiment. . The dot pattern is formed so that the dots become larger as the distance from the light emitting diode 6 increases, so that the luminance can be sufficiently developed even at a position away from the light emitting diode 6. Such a dot pattern is determined as an optimum condition by simulating the distribution of the diffused dots and the output luminance using predetermined simulation software.

  In this embodiment, a commercially available white light emitting diode 6 is used, and the relationship between the emission wavelength and the spectral intensity (spectral distribution curve) is as described with reference to FIG. That is, even though the emitted light from the white light emitting diode 6 is white light, the spectrum intensity in the vicinity of 468 nm that is the blue wavelength region is actually the spectral intensity and red wavelength in the vicinity of 518 nm that is the other green wavelength region. It is larger than the spectral intensity around 635 nm, which is the region, and is bluish as a whole.

  Therefore, in this embodiment, the light output surface 75 of the light guide plate 7 has a color rendering property correction filter layer 11 (color rendering property correction filter means) that can partially absorb light components in the blue wavelength region on the lower layer side of the dots 8. ), The relative intensities of red, green, and blue are leveled in the spectrum distribution curve of the emitted light from the light emitting surface 75, as indicated by a one-dot chain line L0 in FIG.

  In the internally illuminated signboard 1 configured in this way, the emitted light from the white light emitting diode 6 enters the light guide plate 7 as shown by an arrow L1, and then passes from the light emitting surface 75 to the back side of the display panel 3. It is emitted toward. At this time, the light emitted from the white light emitting diode 6 is corrected by the color rendering property correction filter layer 11 so that the spectral intensities in the blue, green, and red wavelength regions are substantially constant, and then the light emission surface. Since the light is emitted from 75, the color rendering property of the white light emitted from the light emitting surface 75 is high. Therefore, in the internally illuminated signboard 1 and the backlight device 4 of this embodiment, even when the color rendering property of the light emitted from the white light emitting diode 6 is low, an image can be displayed using white light having a high color rendering property. A color image with excellent properties can be displayed. Therefore, in the internally illuminated signboard 1 of this embodiment, the image displayed in the transmission mode using the light emitted from the backlight device 4 at night is compared with the image displayed in the daytime and natural light (external light). However, there is almost no difference in color developability, and any of them can display a high-quality color image.

  In addition, since the internally illuminated signboard 1 and the backlight device 4 of this embodiment have good color reproducibility, it is possible to use a solid color for the sign image 2 as well as a gradation color.

  Furthermore, even when such an improvement is made, it is only necessary to add the color rendering property correction filter layer 11, so that a significant cost increase is not caused.

  Furthermore, since the white light emitting diode 6 is used as the white light source of the backlight device 4, the backlight device 4 can be reduced in size and weight and can save power compared with the case where a cold cathode discharge tube or the like is used. You can also plan.

(Method for forming filter layer 11)
In this embodiment, when the color rendering property correction filter layer 11 is formed, first, the light emitting surface 75 of the light guide plate 7 is impregnated with a diluted solution of ethanol (Japanese Pharmacopoeia Disinfection Ethanol 76.9-81.4 Vol.%). Wipe it with gauze, adjust the surface, and let it air dry. The color rendering property correction filter layer 11 formed here has a low transmittance with respect to the wavelength component in the blue wavelength region in the light emitted from the white light emitting diode 6, and the wavelength component in the green wavelength region and the red wavelength region. In other words, the filter has a high transmittance, that is, a yellow filter. In this embodiment, a colored coating layer of a yellow filter is formed with a transparent yellow ink for offset printing. Specifically, about 50 g of transparent yellow ink is put on a kneading plate and taken by a roller, and then the transparent yellow ink is thinly stretched on the light emitting surface 75 of the light guide plate 7 which has been leveled. This operation is performed several times so that the light transmission density becomes 1.2 to 1.5, and then the ink is naturally dried to form a colored coating layer, which is used as the color rendering property correction filter layer 11. did. As the transparent yellow ink, either an oxidation polymerization dry type or a UV cure type can be used.

  In the filter layer 11 formed in this way, when white light from the light emitting diode 6 passes, the light component in the blue wavelength region in the white light is absorbed by the filter layer 11, so each wavelength of blue, green, and red The spectral intensity of the region becomes substantially constant. Here, whether or not the spectral intensities of the blue, green, and red wavelength regions in white light are substantially constant can be determined by a color reproduction method using a color chart. As the color chart, for example, ISO color target or KODAK Q-60 color target can be used. The 17th, 18th, and 19th color wedges A to L corresponding to red, green, and blue in this chart are in close contact with the filter layer 11 in order, and pass through the filter layer 11 and the color wedge. The step color density of each component of the light from the light emitting diode 6 is measured. Then, color reproduction curves for each light component can be drawn, and color reproducibility (color rendering) can be evaluated from the overlapping and similarity of these curves. For this reason, it can be judged from the result whether the spectrum intensity of each wavelength region of blue, green, and red is constant.

  In addition, as a color rendering property correction filter layer 11 (colored coating film layer), an appropriate amount of an aqueous dye such as metanyl yellow or seriton fast yellow is added to a medium such as polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), gelatin, In addition, an oil-based coating material obtained by adding an appropriate amount of an oily dye such as oil yellow to a layer formed from an aqueous coating material obtained by mixing, linseed oil, tung oil, phenol, etc. A layer formed from a pigment such as a gravure transparent yellow ink for printing soft packaging materials, and a coating material obtained by adding the water-based dye, the oil-based dye, or the pigment to a vehicle and mixing them A layer formed from can also be used.

(Modification 1)
In the above embodiment, the color rendering property correction filter layer 11 is formed on the light exit surface 75 of the light guide plate 7. However, the light emitting surface of the light emitting diode 6, the upper and lower end surfaces 71 and 72 of the light guide plate 7, the surface of the reflector 9, and the like. Alternatively, a filter layer may be formed, or a filter layer may be formed at a plurality of locations.

  In addition to forming the color rendering property correction filter layer 11, for example, a filter function is provided in a gap between the light emitting diode 6 and the light guide plate 7, a gap between the light guide plate 7 and the display panel 3, and the like. A colored film may be arranged.

(Modification 2)
3A and 3B are explanatory views showing an enlarged cross section of another example of the internally illuminated signboard, and an explanatory diagram showing a schematic configuration of a backlight device used for the internally illuminated signboard. . In addition, since the basic configuration of the internally illuminated signboard of the present embodiment is the same as that of the internally illuminated signboard described above, portions having corresponding functions are denoted by the same reference numerals and description thereof is omitted. .

  As shown in FIGS. 3 (a) and 3 (b), the internally illuminated signboard 1A of the present embodiment is also a display panel on which a sign image 2 with information such as characters and illustrations is printed on the surface as in the above embodiment. 3 and a backlight device 4A that is disposed on the back side of the display panel 3 and projects a sign image 2 by irradiating light at night or the like. In addition, a plurality of white light emitting diodes 6 arranged in two upper and lower rows, and a light guide plate 7 on which light emitted from the light emitting diodes 6 enters from upper and lower end surfaces 71 and 72 are provided.

  In the light guide plate 7, a large number of dots 8 </ b> A for reducing luminance unevenness are formed on the light exit surface 75. In addition, the opposite surface 76 is formed with unevenness 761 that travels while reflecting incident light and emits the light toward the display panel, and the reflecting plate 9 is disposed in an overlapping manner.

  In the backlight device 4A configured as described above, the dot-like dots 8A on the light emitting surface 75 of the light guide plate 7 are for reducing luminance unevenness on the light emitting surface 75. In addition to the above functions, the color rendering property correction filter layer (color rendering property correction filter means for correcting the spectral intensities of the blue, green, and red wavelength regions in the light emitted from the white light emitting diode 6 to be substantially constant. ). That is, the dots 8A are formed by screen-printing dots-shaped white ink for light diffusion added with filtering ink capable of absorbing the light component in the blue wavelength region of the light emitted from the white light emitting diode 6. Has been.

  As such a filtering ink, for example, a pigment such as a transparent yellow ink for offset printing or a gravure transparent yellow ink for soft packaging material printing can be used, and an appropriate amount of pigment is added to the white ink for light diffusion. This can be used as a raw material for the dots 8A. In this embodiment, good results could be obtained when an amount of pigment corresponding to 13% of the total volume of white ink was added. In addition to the pigments described above, an appropriate amount of water-based dye such as metanil yellow or seriton fast yellow is added to a medium such as polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), gelatin, etc. as the filtering ink. Use water-based coating materials obtained by mixing, and oil-based coating materials obtained by adding an appropriate amount of oily dyes such as oil yellow to a medium such as linseed oil, tung oil, phenol, etc. Can do.

  In the internally illuminated signboard 1A configured as described above, the emitted light from the white light emitting diode 6 enters the light guide plate 7 as shown by an arrow L1, and then travels from the light emitting surface 75 toward the back side of the display panel 3. Are emitted. At that time, the emitted light from the white light emitting diode 6 is corrected by the dots 8A so that the spectral intensities in the blue, green, and red wavelength regions are substantially constant, and then emitted from the light emitting surface 75. Therefore, the color rendering property of the white light emitted from the light emitting surface 75 is high. Therefore, in the internally illuminated signboard 1A and the backlight device 4A according to the present embodiment, even when the color rendering property of the light emitted from the white light emitting diode 6 is low, an image can be displayed using white light having a high color rendering property. A color image with excellent properties can be displayed. Therefore, in the internally illuminated signboard 1 of this embodiment, an image displayed in the transmission mode by using the light emitted from the backlight device 4A at night, and an image displayed in the reflection mode by natural light (external light) at night. Even in the case of the above, there is almost no difference in color developability, and any of them can display a high-quality color image. In addition, since the internally illuminated signboard 1A and the backlight device 4A of this embodiment have good color reproducibility, it is possible to use a solid color for the sign image 2 as well as a gradation color. Furthermore, even when such improvement is achieved, it is only necessary to change the ink material for forming the dots 8A, so that a significant increase in cost is not caused. Furthermore, since the white light emitting diode 6 is used as the white light source of the backlight device 4A, the backlight device 4A can be reduced in size and weight and can save power compared to the case where a cold cathode discharge tube or the like is used. You can also plan.

[Example of application to liquid crystal display devices]
Each of the backlight devices 4 and 4A described above can be used for a liquid crystal display device (display device). 4A and 4B show a liquid crystal display device in which the backlight devices 4 and 4A having the above-described configuration are incorporated.

  As shown in FIGS. 4A and 4B, the liquid crystal display devices 10 and 10A are both transflective liquid crystal display devices. The liquid crystal display device 10 shown in FIG. The light emitting surface 75 of the light guide plate 7 is incorporated in the liquid crystal display device 10A shown in FIG. The backlight device 4A having a configuration in which the dots 8A formed in the above also have a filter function is incorporated.

  In any of the liquid crystal display devices 10 and 10A, a known liquid crystal panel 3A (display panel) as a display panel can be used, and a detailed description thereof will be omitted. A transparent electrode (not shown) for driving the liquid crystal is formed, and the liquid crystal 40 is held between the pair of substrates 31 and 32. In the liquid crystal panel 3A, polarizing plates 61 and 62 are disposed on the back side where the white light emitted from the backlight devices 4 and 4A is incident and on the front side where the display light is emitted. As the liquid crystal panel 3A, an active matrix liquid crystal panel in which a thin film transistor (TFT) or a thin film diode element (TFD) as a non-linear element for pixel switching is formed in each pixel 300 can be used. In addition, as the liquid crystal panel 3A, a passive matrix liquid crystal panel in which transparent pixel electrodes for driving liquid crystals on a pair of substrates extend in directions orthogonal to each other can be used.

  On the inner surface of the counter substrate 31, a light reflecting layer 33 made of a single layer film or a multilayer film of aluminum, aluminum alloy, silver, silver alloy, etc., and red (R), green at positions corresponding to the respective pixels 300. Color filter layers 341R, 342R, 341G, 342G, 341B, and 342B of (G) and blue (B) are formed. The light reflection layer 33 is for display in the reflection mode, and the light reflection layer 33 is formed with a light transmission window 330 that enables display in the transmission mode.

  In the thus configured liquid crystal display devices 10 and 10A, the white light emitted from the backlight devices 4 and 4A is incident on the liquid crystal panel 3A and then transmitted through the light reflecting layer 33 as indicated by an arrow L1. The light enters the liquid crystal layer 40 from the window 330 and exits from the element substrate 32 side. At that time, the display light is optically modulated by the liquid crystal layer 40 in each pixel 300 to display an image in the transmission mode.

  On the other hand, external light such as sunlight incident from the side of the element substrate 32 is reflected by the light reflecting layer 33 through the liquid crystal layer 40 and again through the liquid crystal layer 40 as indicated by an arrow L2. It is emitted from the side. At that time, the display light is optically modulated by the liquid crystal layer 40 in each pixel 300 to display an image in the reflection mode.

  Here, the white light emitted from the backlight devices 4 and 4A has a color rendering property correction filter layer 11 (color rendering property correction filter means) configured in the backlight devices 4 and 4A, or has a filter function. In the dot 8A (color rendering property correction filter layer, color rendering property correction filter means), the light is corrected so that the spectral intensities in the blue, green, and red wavelength regions are substantially constant. For this reason, since it is white light with high color rendering properties, it is possible to display a color image with high brightness and saturation on the liquid crystal panel 3A. Therefore, it is possible to eliminate the difference in color development between the color image displayed in the transmissive mode and the color image displayed in the reflective mode.

[Other embodiments]
Furthermore, in the above embodiment, the white light emitting diode 6 is used as the white light source, but in addition to this, a white light source that combines blue, green, and red light emitting diodes, a cold cathode discharge tube, a halogen lamp, a metal halide lamp, etc. Of course, the present invention can be applied. Regardless of which white light source is used, light in a predetermined wavelength region of the blue, green, and red wavelength regions of white light emitted from the white light source in a color rendering property correction filter such as a colored coating layer. What is necessary is just to correct | amend so that the spectral intensity of each wavelength range may become substantially constant by absorbing a component.

(a), (b) is the front view which shows the internally illuminated signboard to which this invention is applied, respectively, and its longitudinal cross-sectional view. (a) And (b) is explanatory drawing which expands and shows the cross section of the internally illuminated signboard of FIG. 1, and explanatory drawing which shows schematic structure of the backlight apparatus used for this internally illuminated signboard. It is explanatory drawing which expands and shows the cross section of another example of an internally illuminated signboard, and explanatory drawing which shows schematic structure of the backlight apparatus used for this internally illuminated signboard. (a), (b) is a schematic sectional drawing which respectively shows the liquid crystal display device to which this invention is applied. It is a figure which shows the relationship between the light emission wavelength of white light emitting diode, and spectral intensity.

Explanation of symbols

1, 1A Interior-lit signboard (display device)
2 Sign image (display panel)
3 Display panel 30 Transparent substrate 4, 4A Backlight device 6 White light emitting diode (white light source)
7 Light guide plate 75 Light exit surface 8, 8A Dot 9 Reflector 11 Color rendering property correction filter layer (color rendering property correction means / colored coating layer)
10, 10A Liquid crystal display device (display device)
3A LCD panel (display panel)
31, 32 Substrate 300 Pixel 40 Liquid crystal 33 Reflective film layer 341, 342 Color filter 330 Light transmission window

Claims (9)

In a surface light source device including a white light source, and a light guide plate that emits light emitted from the white light source and is emitted from the light exit surface,
At least one portion of the light path from the white light source to the light exit surface of the light guide plate partially absorbs a light component in a predetermined wavelength region of the visible light region included in the light emitted from the white light source and emits the light. A surface light source device, wherein color rendering correction filter means for leveling the relative intensity of a spectrum distribution curve of light emitted from a surface is arranged. In Claim 1, the white light source is a white light emitting diode,
The surface light source device, wherein the color rendering correction filter means is a blue component absorption filter capable of absorbing a part of a blue component. A back panel comprising a display panel capable of displaying a color image in a transmissive mode, a white light source, and a light guide plate through which light emitted from the white light source enters and is emitted from the light exit surface toward the back side of the display panel In a display device having a light device,
At least one portion of the optical path from the white light source to the display panel absorbs a part of the light component in a predetermined wavelength region in the visible light region included in the light emitted from the white light source and exits from the light emitting surface. A display device comprising color rendering correction filter means for leveling a relative intensity of a spectral distribution curve of incident light. In Claim 3, the white light source is a white light emitting diode,
The display device, wherein the color rendering property correction filter means is a blue component absorption filter capable of absorbing a part of a blue component.   5. The display device according to claim 3, wherein the display panel is capable of displaying a color image even in a reflection mode using external light. In any one of Claims 3 thru | or 5, The said backlight apparatus is provided with a reflective surface on the opposite side to the light-projection surface of the said light-guide plate,
The color rendering property correction filter means is disposed at least at one position between the white light source and the light guide plate, between the reflective surface and the light guide plate, and between the light guide plate and the display panel. A display device characterized by being made.   The display device according to claim 6, wherein the color rendering property correction filter unit includes a colored coating layer containing a color material that partially absorbs a light component in the predetermined wavelength region. In claim 6, the light guide plate is printed with a large number of dots for correcting the light amount distribution of the emitted light from the light emitting surface,
The multiple dots constitute the color rendering property correction filter means by including a color material that partially absorbs the light component in the predetermined wavelength region in the ink forming the dots. Display device.   9. The display device according to claim 3, wherein the display panel is formed by printing various information on a transparent base material in color.