JP2002343125A - Surface illumination equipment and image display equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain surface illumination equipment and image display equipment, which can illuminate a comparatively large area uniformly using point light sources. SOLUTION: The surface illumination equipment consists of light source units 10A and 10B, which consists of light emitting diodes 11 and 11a, and a linear light guide body 15. The both end surfaces are made a reflection slope surface 17, and the linear light guide body 15 is adhered with no crevice by the reflection slope surface 17, and it is arranged along with an incident end surface 21 of the light guide plate 20. The light emitting diodes 11 and 11a are arranged at the upper surface side and under surface side of the linear light guide body 15, facing the reflection slope surface 17. The light emitted from the light emitting diodes 11 and 11a are incident to the inside of the light guide body 15 from the reflection slope surface 17, and while going on in its longer direction, it is reflected at a back surface 18 and emitted toward the surface light guide plate 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread illuminating device and a video display device, and more particularly to a spread illuminating device optimal as a front light of a reflective display device and a video display device provided with the illuminating device.

[0002]

2. Description of the Related Art Conventionally, with the spread of mobile phones and PDAs (Personal Digital Assistants), it has been desired to provide a video display device with low power consumption and high display quality. As a display device that satisfies this, a reflection type liquid crystal display device has been attracting attention.

[0003] Since this type of reflective liquid crystal display device uses external light as illumination light in a bright place, a transmissive liquid crystal display device and a transflective liquid crystal display device do not always require a backlight. Thus, low power consumption can be achieved. On the other hand, in a dark place, auxiliary lighting means (front light) for illuminating the display surface of the display device from above is required to improve visibility.

[0004] As a front light, a side light system in which a linear light source is arranged on an incident end face of a planar light guide plate which emits light in a planar manner is mainly used. Conventionally, a cold cathode tube has been used as a bright linear light source. However, there are problems such as the necessity of an inverter circuit, high power consumption, and short life. Therefore, as an illumination light source of a small display device such as a mobile phone, a light-emitting diode that does not require an inverter circuit, consumes low power, and has a long life has been used.

[0005] For example, Japanese Patent Application Laid-Open No. 10-260405 discloses a planar lighting device in which light-emitting diodes are arranged on both end faces of a linear light guide. However, a light emitting diode as a light source of a video display device having a relatively large display surface such as an electronic book device cannot provide a sufficient amount of light, and when the length of the linear light guide is long, the amount of light in the length direction varies. (Particularly, the amount of light in the central portion is reduced). In order to cope with insufficient light quantity, it is conceivable to arrange a plurality of light emitting diodes on both end faces of the linear light guide. It becomes difficult to mount it on a video display device.

Japanese Patent Application Laid-Open No. 2000-330112 discloses a planar lighting device in which a light source unit in which a light emitting diode is disposed on one end surface of a linear light guide is arranged in series along the incident end surface of a planar light guide plate. Is disclosed. However, in this device, since the emitted light of the light emitting diode is directed only to the linear light guide facing the light emitting diode, there remains a problem that the arrangement portion of the light emitting diode appears as a dark line on the image display surface. .

It is an object of the present invention to provide a planar illumination device and an image display device that can illuminate a relatively large area uniformly using a point light source.

Another object of the present invention is to provide a planar illumination device and a video display device having a compact configuration.

[0009]

In order to achieve the above objects, a spread illuminating apparatus according to the present invention comprises a point light source and a light source for guiding light emitted from the point light source and extending along a longitudinal direction. A plurality of light source units, each having a point light source disposed on the upper surface side and / or the lower surface side of the linear light guide, and a linear light guide that emits light linearly from the linear light guide. A planar light guide plate that receives the emitted light from the incident end face and emits the illumination light as planar illumination light, wherein the plurality of light source units are
The planar light guide plate is arranged in series along the incident end face.

In the planar illuminating device having the above-described configuration, a plurality of light source units are arranged in series along the incident end face of the planar light guide plate. Light can be incident on the planar light guide plate with a bright distance and a uniform light amount, and thus a wide area can be illuminated evenly. In particular, the point light sources of each light source unit are arranged three-dimensionally on the upper surface side and / or lower surface side of the linear light guide, so to speak, the linear light guides can be arranged in series without a break, It is possible to suppress unevenness in the light amount in the longitudinal direction of the linear light guide without generating dark lines in the planar light guide plate.

A plurality of point light sources may be provided in one light source unit. That is, a plurality of point light sources may be provided on the upper surface side and the lower surface side of the linear light guide. By arranging a plurality of point light sources in this manner, the light amount increases and the light amount unevenness further decreases. In addition, even when a plurality of point light sources are arranged on the upper surface side and the lower surface side of the linear light guide, the width of the linear light guide in the short side direction is not increased, and a compact configuration can be achieved.

A plurality of point light sources provided in one light source unit may be independently controllable for lighting. By selectively lighting a point light source having a predetermined spectral characteristic according to the characteristics of the display device and the characteristics of external light, the spectral characteristics of the illumination light of the light source unit can be changed, and the color balance of the display device can be changed. Can be adjusted.

In the spread illuminating apparatus according to the present invention, each linear light guide has reflection slopes at both ends thereof for reflecting light emitted from the point light source, and all reflection slopes have the same inclination angle. It is preferred that If the inclination angles of the reflection slopes at both ends are equal, a plurality of linear light guides can be arranged in series without any gap, and light can be uniformly incident in the longitudinal direction on the incident end face of the planar light guide plate. Can be.

Further, it is preferable that the point light sources are arranged near at least one of the respective reflection slopes formed at both ends of each linear light guide. The light emitted from the point light source passes through the upper surface and / or lower surface, reaches a reflection slope near the light source, is reflected by the reflection slope, and is guided into the linear light guide.

Preferably, a light emitting diode is used as the point light source. Light-emitting diodes have low power consumption and long life, and can be reduced in size and weight, including their driving circuits, and have no danger such as cracking like cold cathode tubes. Further, when a plurality of point light sources are provided in one light source unit, light sources having different spectral characteristics may be used as each point light source. By combining point light sources having different spectral characteristics, a light source having arbitrary spectral characteristics can be obtained, and the color balance of the display device can be adjusted.

Further, the light source unit may include a reflection housing surrounding the linear light guide. The light leaked from the linear light guide is reflected by the reflection housing and is incident on the linear light guide again, so that the light can be used effectively. Furthermore, if this reflection housing is used as a holding member for the light source unit, the light source unit can be made compact.

Also, the plurality of light source units may be independently controllable for lighting. By lighting only necessary portions in accordance with the usage of the display device, power saving can be achieved.

Further, the image display device according to the present invention is characterized in that the planar illumination device is arranged on a display surface of a reflection type display device. This makes it possible to display an image that is bright and has little unevenness in light amount.

Further, it is preferable that the reflection type display device includes a liquid crystal exhibiting a cholesteric phase at room temperature.
A display device using this type of liquid crystal is small, lightweight, and thin, and has an advantage that power consumption can be reduced because a display state can be maintained even after power supply is stopped after display driving is completed. I have.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a spread illuminating apparatus and a video display apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a configuration of a spread illuminating apparatus 1 according to a first embodiment in an exploded state, and FIG. 2 shows a cross section in an assembled state.

The planar lighting device 1 includes a light source unit 10
A and 10B are arranged in series along the incident end face 21 of the planar light guide plate 20. Each light source unit 10A, 10B
Is a light emitting diode 11 that is a point light source, and a linear light guide that converts light from the light emitting diode 11 into a linear shape and emits the light from the side surface (outgoing surface) 16 along the longitudinal direction toward the incident end surface 21. And the body 15. As the light emitting diode 11, it is preferable to use a chip type high brightness light emitting diode that emits white light.

Both end faces of each linear light guide 15 are reflection slopes 17.
The inclination angle of each reflection slope 17 is, for example, 45.
° and are joined in close contact with each other. Also, the V on the back surface 18 of the linear light guide 15 at a predetermined interval.
A groove 18a having a shape is formed.

The light emitting diode 11 has a reflection slope 17 at one end.
Is provided so as to face the upper surface of each linear light guide 15 in the vicinity. The light emitted from each light emitting diode 11 is reflected by the reflection slope 17 and guided inside each linear light guide 15, and is uniformly spread in the longitudinal direction while repeating total internal reflection, and has a V-shaped groove 18 a. Are emitted from the emission surface 16 toward the incident end surface 21 of the planar light guide plate 20 while changing the direction.

The planar light guide plate 20 has a flat bottom surface 22,
The upper surface 23 is a well-known one in which a plurality of inequality prisms having a sawtooth shape are formed. Light emitted from the exit surface 16 of the linear light guide 15 is transmitted from the incident end face 21 to the planar light guide plate 20.
And is spread in a planar shape while repeating total internal reflection therein. The light path is converted downward by the upper surface 23 (micro prism surface), and is emitted from the bottom surface 22 as uniform planar illumination light. Although not shown in FIGS. 1 and 2, the reflective liquid crystal display device is installed such that the display surface faces the bottom surface 22.

The light emitting diode 11 and the linear light guide 15 are held by a reflector (reflection housing) 14, and the inner surface of the reflector 14 is a reflection surface. The reflector 14 surrounds the linear light guide 15 other than the emission surface 16, and
Light leaking from other places is reflected and re-entered into the linear light guide 15, thereby effectively utilizing the light.

A reflecting sheet (not shown) is attached to the reflecting slope 17 of the linear light guide 15 using a transparent adhesive sheet. A double-sided reflection sheet is used for the reflection slope 17 to which the linear light guide 15 is joined. Note that a reflective film may be coated instead of the reflective sheet, and the reflective surface may be configured by other methods.

In the planar lighting device 1 having the above-described configuration, since the plurality of light source units 10A and 10B are arranged in series in the longitudinal direction, even if the incident end face 21 of the planar light guide plate 20 becomes long, the light source unit can be used. It is sufficient to increase the number, and each light source unit itself does not become so long, and a uniform bright light amount can be obtained in the longitudinal direction despite the use of the point light sources.

In particular, the light emitting diode 11 is a linear light guide 1
5 are arranged on the upper surface (or may be the lower surface), and the linear light guides 15 are joined without a break. Therefore, no dark line is generated in the planar light guide plate 20 and the linear light guides 15 The unevenness in the light amount in the longitudinal direction is eliminated.

When the V-shaped groove 18a provided on the back surface 18 of the linear light guide 15 is arranged so that the portion far from the light emitting diode 11 becomes dense, a more uniform light amount can be obtained in the longitudinal direction.

(Second Embodiment, see FIG. 3) FIG. 3 shows a configuration of a spread illuminating apparatus 2 according to a second embodiment in an exploded state. The spread illuminating device 2 includes a rear surface 18 of the linear light guide 15.
Is a light diffusion surface, a diffraction grating surface, or a hologram surface having the same function as that of the groove 18a. Other configurations, functions, and effects are the same as those of the spread illuminating apparatus 1 according to the first embodiment. In FIG. 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 4 shows a configuration of a planar lighting device 3 according to a third embodiment in an exploded state, and FIG. 5 shows a cross section in an assembled state.

The spread illuminating device 3 includes the light source units 1
The reflection slope 1 is also provided on the lower surface side of the linear light guide 15 of 0A and 10B.
7, a light emitting diode 11a facing the light emitting diode 7 is arranged. In other words, light is incident on both sides of each linear light guide 15 by the light emitting diodes 11 and 11a, so that the light amount can be increased and the light amount can be made more uniform.

Further, the V-shaped groove 18a formed on the back surface 18 of the linear light guide 15 is arranged so that the end is coarse and the center is dense. By increasing the density of the groove 18a located at the central portion far from the light emitting diodes 11, 11a, a more uniform light amount can be obtained in the longitudinal direction.

The other structures, functions and effects of the spread illuminating device 3 are the same as those of the spread illuminating device 1 according to the first embodiment. In FIGS. The reference numerals are used, and the description is omitted.

(Refer to FIG. 6 for the fourth embodiment) The spread illuminating apparatus according to the fourth embodiment is similar in configuration to the spread illuminating apparatus 3 according to the third embodiment. The point is that the light emitting diodes 11 and 11a arranged in the units 10A and 10B have different spectral characteristics. For example, in a liquid crystal display device disposed immediately below the planar light guide plate 20, red spectral reflectance (or spectral transmittance) is used.
Is extremely low, a white light emitting diode and a red light emitting diode are arranged in the respective light source units 10A and 10B. As described above, in the case of a display device in which red color is insufficient, it is possible to supplement the red color by turning on the red light emitting diode.

FIG. 6 shows an example of a circuit for controlling the light source units 10A and 10B. This control circuit includes a power supply 102
And a switching circuit 1 for turning on and off the supply of power from the power supply 102 to each of the light emitting diodes 11 and 11a.
01 and a control unit 100 for controlling the operation of the switching circuit 101. The switching circuit 101 receives light-emitting diodes 11, 11 according to an instruction from the control unit 100.
a is independently turned on and off.

As described above, the linear light guide that guides light incident from both ends and radiates the light linearly, and the plurality of point light sources that irradiate light to both ends of the linear light guide are described. A planar light guide plate that guides light emitted from a linear light guide and emits it as planar illumination light, and a control unit that independently turns on and off each point light source. With the lighting device and the display device including the same, the spectral characteristics of the illumination light from the planar lighting device can be changed. Thereby, the color development of the display device is corrected by the illumination light of the planar illumination device, and a good color balance can be obtained in total.

When this planar illumination device is used in combination with a reflection type display device (when external light is used as illumination light), not only is it used as auxiliary illumination in a dark environment but also at a predetermined spectral luminance. By selectively turning on a light source having characteristics (in the fourth embodiment, for example, by turning on only a red diode), it can be used as a means for color balance correction even in a bright field.

(Fifth Embodiment, see FIGS. 7 and 8) FIG. 7 shows the structure of a spread illuminating apparatus 5 according to a fifth embodiment in an exploded state. The planar lighting device 5 includes three light source units 10
A, 10B, and 10C are arranged in series, and each light source unit 1
0A, 10B, and 10C can be independently controlled for lighting. In the planar light guide plate 20 in which the upper surface 23 is constituted by a microprism array having a scalene triangular shape, the light incident from the incident end face 21 is guided in a direction perpendicular to the ridge line of the prism. That is, each light source unit 10
The light emitted from A, 10B, and 10C is exclusively the area A,
B and C are respectively illuminated.

Therefore, when it is only necessary to observe at least one of the images in the areas A, B, and C, unnecessary power consumption can be prevented by selectively lighting the light source units 10A, 10B, and 10C. . FIG. 7 shows a state where the light source unit 10A is turned on and the light source units 10B and 10C are turned off. Further, each light source unit 10A,
In 10B and 10C, the light emitting diodes 11 and 11a
May be independently controllable.

FIG. 8 shows the light source units 10A, 10B, 10
1 shows an example of a circuit for controlling C. The control circuit includes a power supply 112 and the light emitting diodes 11 and 11 from the power supply 112.
The control circuit 110 includes a switching circuit 111 for turning on and off the supply of power to a, and a control unit 110 for controlling the operation of the switching circuit 111. Switching circuit 111
Is the light emitting diode 1 according to an instruction from the control unit 110.
1, 11a are turned on and off independently for each of the regions A, B, and C.

The other structure, operation and effect of the spread illuminating device 5 are the same as those of the spread illuminating devices 1 and 3 of the first and third embodiments. The same members have the same reference characters allotted, and description thereof will not be repeated.

(Sixth Embodiment, See FIG. 9) FIG. 9 shows a cross section of an image display device 60 according to a sixth embodiment. The image display device 60 is a combination of the planar illumination device 3 and the reflection type liquid crystal display device 61, and the planar light guide plate 20.
And the display surface 61a of the display device 61 are disposed so as to face each other.

The reflection type liquid crystal display device 61 is composed of a liquid crystal display element 62 formed by laminating a polarizing plate, a wave plate and a liquid crystal cell, and a reflection member 63 provided on the lower surface of the liquid crystal display element 62. The liquid crystal cell is a liquid crystal exhibiting a cholesteric phase at room temperature, for example, a chiral nematic liquid crystal obtained by adding a sufficient amount of a chiral agent to a nematic liquid crystal to exhibit a cholesteric phase. Are held so as to keep the interval of.

In this image display device 60, the illumination light emitted from the bottom surface 22 of the planar light guide plate 20 is applied to the display device 61.
The light is then reflected and modulated, and again enters the planar light guide plate 20 as image light. Further, the image light passes through the planar light guide plate 20 and is emitted upward from the upper surface 23. By using the spread illuminating device 3, a bright and even image can be obtained.

It is needless to say that any one of the liquid crystal display device 61 and the planar lighting devices 1, 2, 3, and 5 may be combined, and the same applies to the seventh embodiment described below.

(Seventh Embodiment, see FIG. 10) FIG. 10 shows a cross section of an image display device 70 according to a seventh embodiment. The image display device 70 is a combination of the planar illumination device 3 and a full-color reflective liquid crystal display device 71, and the bottom surface 22 of the planar light guide plate 20 and the display surface 71a of the display device 71 face each other. Are arranged as follows.

The liquid crystal display device 71 includes a liquid crystal cell 72B for selectively reflecting blue and a liquid crystal cell 72 for selectively reflecting green.
It has a three-layer structure of a liquid crystal cell 72R that performs G and red selective reflection, and a light absorbing layer 73 for absorbing light not reflected by each liquid crystal cell is disposed at the lowermost layer.

The operation of the illumination light in the image display device 70 is the same as that in the sixth embodiment. By using the planar illumination device 3, a bright and even image can be obtained.

(Other Embodiments) The spread illuminating apparatus and the video display apparatus according to the present invention are not limited to the above embodiments, but can be variously modified within the scope of the invention.

In particular, the detailed structure and shape of the linear light guide and the planar light guide plate are arbitrary, and the detailed configuration of the reflection type liquid crystal display device is also arbitrary.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a spread illuminating apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing the spread illuminating apparatus according to the first embodiment.

FIG. 3 is an exploded perspective view showing a spread illuminating apparatus according to a second embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a planar lighting device according to a third embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a spread illuminating apparatus according to the third embodiment.

FIG. 6 is a block diagram showing an example of a control circuit of a spread illuminating apparatus according to a fourth embodiment of the present invention.

FIG. 7 is an exploded perspective view showing a spread illuminating apparatus according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing an example of a control circuit of the spread illuminating apparatus according to the fifth embodiment.

FIG. 9 is a schematic sectional view showing an image display device according to a sixth embodiment of the present invention.

FIG. 10 is a schematic sectional view showing an image display device according to a seventh embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3, 5 ... Planar lighting device 10A, 10B, 10C ... Light source unit 11, 11a ... Light emitting diode 14 ... Reflector 15 ... Linear light guide 17 ... Reflection slope 20 ... Planar light guide plate 21 ... Incident end face 60, 70: Video display device 61, 71: Reflective liquid crystal display device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 G02F 1/13357 G09F 9/00 336 G09F 9/00 336B // F21Y 101: 02 F21Y 101: 02 (72) Inventor Ichiro Fujishiro 2-13-13 Azuchicho, Chuo-ku, Osaka City, Osaka International Building Minolta Co., Ltd. F-term (reference) 2H038 AA55 BA06 2H089 HA40 QA11 TA02 TA17 TA18 TA20 2H091 FA08X FA08Z FA14Z FA23X FA41X FA45X GA02 LA11 LA18 5G435 AA03 AA18 BB12 BB16 EE22 FF03 FF08 GG23 GG26

Claims (10)

[Claims] 1. A point light source and a linear light guide that guides light emitted from the point light source and emits the light linearly from a side surface along a longitudinal direction, wherein each of the point light sources has a linear shape. A plurality of light source units arranged on an upper surface side and / or a lower surface side of the light guide; and a planar light guide plate which receives light emitted from the linear light guide from an incident end face and radiates it as planar illumination light. And the plurality of light source units are arranged in series along the incident end face of the planar light guide plate. 2. A light guide according to claim 1, wherein each of the linear light guides has reflection slopes at both ends thereof for reflecting light emitted from the point light source, and all the reflection slopes have the same inclination angle. Item 2. The planar lighting device according to Item 1. 3. The linear light guide according to claim 1, wherein the point light sources are arranged near at least one of respective reflection slopes formed at both ends of the linear light guide. Planar lighting device. 4. The spread illuminating apparatus according to claim 1, wherein the point light source is a light emitting diode. 5. The light source unit according to claim 1, wherein a plurality of point light sources are arranged in one light source unit, and each point light source has a different spectral characteristic.
Alternatively, the planar lighting device according to claim 4. 6. The light source unit according to claim 1, wherein the light source unit includes a reflection housing surrounding the linear light guide. Planar lighting device. 7. The spread illuminating apparatus according to claim 5, wherein the reflection housing holds the light source unit. 8. The light source unit according to claim 1, wherein lighting control of each of the plurality of light source units can be independently performed. Item 8. The planar lighting device according to item 7. 9. The spread illuminating device according to claim 1, 2, 3, 4, 5, 6, 7, or 8 is a display surface of a reflective display device. An image display device characterized by being disposed on the top. 10. The image display device according to claim 9, wherein the reflection type display device includes a liquid crystal exhibiting a cholesteric phase at room temperature.