JPH11249136A - Back light device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently take in external light and further to adopt a light emitting diode(LED) as an internal light source. SOLUTION: A wedge-shaped back light transmission plate 3 is arranged on the back of a color liquid crystal display(LCD) panel 2, a wedge-shaped external light introduction prism is arranged while being overlapped on the internal light reflecting plane of that back light transmission plate 3, an LED 5 is arranged on the end face of the back light transmission plate 3, and the end face of the external light introduction prism is confronted with an external light take-in window 6. Since external light can be efficiently taken in by arranging the external light introducing means while overlapping it on the internal light reflecting plane of the internal light introducing means arranged on the back of a member to be illuminated and further the member to be illuminated can be efficiently illuminated almost without loss light, even when the internal light source is turned off, the member to be illuminated can be illuminated sufficiently light only with external light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a backlight device most suitable for illuminating a color liquid crystal display panel or the like built in an electronic viewfinder of a video camera from the back.

[0002]

2. Description of the Related Art The inventor of the present invention has disclosed in, for example,
The prior invention of the backlight device disclosed in Japanese Patent Application Publication No. 60028 or the like has been invented first. The prior application invention illuminates a color liquid crystal display panel, which is a member to be illuminated, incorporated in an electronic viewfinder of a video camera from the back side thereof using an internal light source and external light such as sunlight. is there. In the prior invention, a prism for introducing external light such as sunlight is disposed on the back of the color liquid crystal display panel, and a lens for introducing internal light is disposed on the back of the prism for introducing external light. Then, external light, such as sunlight, entering from the external light intake window is introduced through the external light introducing prism to irradiate the back of the color liquid crystal display panel, and at the same time, internal light emitted from the internal light source is introduced into the internal light source. The light was introduced through a lens and an external light introducing prism to illuminate the back surface of the color liquid crystal display panel, and a direct-type fluorescent tube was used as an internal light source.

[0003]

However, since the direct-type fluorescent tube has a large volume and requires a booster circuit to light it, the circuit board on which the booster circuit is mounted also becomes large. The entire internal light source system becomes larger,
It is difficult to reduce the size of the entire viewfinder. Also,
The direct-type fluorescent tube has a problem that it consumes a lot of power when lit and is uneconomical.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to efficiently take in external light such as sunlight, and to use an ultra-compact, light-emitting diode or the like as an internal light source. It is an object of the present invention to provide a backlight device that can employ the above light source.

[0005]

According to the present invention, there is provided a backlight device in which an internal light introducing means is disposed on a back surface of a member to be illuminated, and an internal light reflecting surface of the internal light introducing means is provided. The external light introducing means is disposed on the external light introducing means, and the external light introducing end face of the external light introducing means faces the external light introducing window, and the internal light source is disposed on the internal light introducing end face of the internal light introducing means. .

In the backlight device of the present invention configured as described above, since the external light introducing means is disposed on the internal light reflecting surface of the internal light introducing means disposed on the back of the illuminated member, the internal light In addition to being able to efficiently take in external light without being hindered by the light guide path, the illuminated member can be efficiently illuminated from the back with almost no loss of light, and Since the light source can be disposed on the internal light introducing end face of the internal light introducing means, it is possible to employ a micro light source such as a light emitting diode as the internal light source.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a backlight device in which the present invention is applied to backlighting of a color liquid crystal display panel will be described below with reference to the drawings.

First Embodiment of Backlight Device FIGS. 1 to 3 show a first embodiment of a backlight device 1 according to the present invention. A backlight light guide plate 3, which is an internal light introducing means formed of a synthetic resin such as acrylic, glass, or the like, having a small size, is superposed on a back surface 2a of the color liquid crystal display panel 2 arranged in a shape. Backlight light guide plate 3
Further, on the rear side, an external light introducing prism 4 which is an external light introducing means which is formed in a substantially wedge-shaped and large size by a synthetic resin such as acrylic or glass or the like is superimposed, and is opposite to the vertical direction of the backlight light guide plate 3. It is arranged in the direction. Then, a plurality of ultra-small light sources such as a plurality of light emitting diodes 5 are disposed at equal intervals along the internal light introducing end face 3a formed horizontally at the lower end of the backlight light guide plate 3, and an external light introducing prism is provided. External light introduction end face 4a formed on the upper end of
Is exposed to an external light intake window 6 formed of a synthetic resin such as acrylic, glass, or the like. At this time, the back side of the backlight light guide plate 3 is formed on the obliquely cut internal light reflecting surface 3b, and the front side is formed on the inside / outside light guiding surface 3c parallel to the color liquid crystal display panel 2. Further, both sides of the external light introducing prism 4 are external light reflecting surfaces 4b,
4c, and an external light guide surface 4d that is obliquely cut is formed at the lower end. Then, an external light introducing prism 4 is provided on the anti-slope surface 3 b of the backlight light guide plate 3.
Of the external light exit surface 4d are superimposed.

Therefore, according to the first embodiment of the backlight device 1, as shown in FIG. 1, when the light emitting diode 5 and the like are turned on, the internal light IL emitted from the light emitting diode 5 and the like is backed up. The light is guided from the internal light introducing end face 3a of the light guide plate 3, is reflected by the internal light reflecting surface 3b, and is transmitted from the internal and external light guiding surface 3c to the rear surface 2a of the color liquid crystal display panel 2.
And the color liquid crystal display panel 2 can be efficiently illuminated from the back. Therefore, a micro light source such as the light emitting diode 5 can be adopted as the internal light source.

On the other hand, as shown in FIGS. 2 and 3, external light OL such as sunlight, which is incident on the external light introducing window 6 from all directions, is introduced from the external light introducing end face 4a of the external light introducing prism 4. After being reflected by the external light reflecting surfaces 4b and 4c, the light is efficiently introduced into the backlight light guide plate 3 from the external light output surface 4d, and is radiated from the internal and external light output surface 3c to the back surface 2a of the color liquid crystal display panel 2. The color liquid crystal display panel 2 can be efficiently illuminated from the back. Therefore, the external light OL can be efficiently taken in without being hindered by the light guide path of the internal light IL, and the loss light of the taken external light OL (which reaches the back surface 2a of the color liquid crystal display panel 2). (E.g., light that escapes to the outside of the backlight light guide plate 3 or the external light introducing prism 4 before the light is emitted). The panel 2 can be efficiently illuminated from the back surface 2a.

According to this backlight device 1, as shown in FIG. 1, a light diffusing means which is a light diffusing surface 11 such as a minute groove or unevenness is provided on the internal light reflecting surface 3b of the backlight light guide plate 3. The light diffusing sheet 12 and the prism sheet 13 are formed on the light guiding surface 3 c of the backlight light guide plate 3.
It is preferable to provide light diffusion means such as

With this configuration, the light emitting diode 5
When the external light IL emitted from the internal light introducing end face 3a and introduced into the backlight light guide plate 3 from the internal light introducing end face 3a is reflected by the external light reflecting surface 3b, the external light IL is widely diffused by the light diffusing means such as the light diffusing surface 11. You. Then, the internal light IL diffused in a wide range passes through the light diffusion means such as the light diffusion sheet 12 and the light diffusion prism 13 from the inside / outside deriving surface 3c and is again irradiated to the back surface 2a of the color liquid crystal display panel 2. Widespread. Then, a part of the diffused internal light IL returns to the internal light reflecting surface 3b side, is reflected and diffused again, and returns to the internal / external light guiding surface 3c. In this manner, a uniform surface light source can be obtained by repeatedly reflecting and diffusing the internal light IL, and finally, the surface light source of the internal light IL can evenly illuminate the entire back surface 2a of the color liquid crystal display panel 2. Therefore, even if a very small internal light source such as the light emitting diode 5 is used, the back surface 2a of the color liquid crystal display panel 2 can be sufficiently illuminated.

According to this backlight device 1,
As shown in FIGS. 2 and 3, light reflecting means such as light reflecting sheets 15 and 16 are provided on the external light reflecting surfaces 4b and 4c of the external light introducing prism 4, and light diffusing means such as a Fresnel-shaped prism 17 is provided. It is preferable to form or provide the light diffusion sheet 18 on the external light guide surface 4d.

With this configuration, the external light OL that has entered the external light introducing window 6 and has been introduced into the external light introducing prism 4 from the external light introducing end face 4a can be reflected by the light reflecting sheets 15, 1.
6, the light can be efficiently reflected, and the light can be diffused over a wide range by a light diffusion means such as a Fresnel prism 17. Then, when the reflected and diffused external light OL is guided into the backlight light guide plate 3 from the external light outgoing surface 4d, the light is diffused over a wide area again by the light diffusing means such as the light diffusing sheet 18. A part of the external light OL irradiated from the inside / outside light guiding surface 3c of the backlight light guide plate 3 to the back surface 2a of the color liquid crystal display panel 2 is reflected by the inside / outside light guiding surface 3c and becomes the external light introducing prism 4
Then, the light is reflected and diffused again, and returns to the inside / outside light guide surface 3c. In this way, by repeating the reflection and diffusion of the external light OL, a uniform surface light source is obtained as the external light OL emitted from the inside / outside light outgoing surface 3c to the back surface 2a of the color liquid crystal display panel 2, and the external light OL is obtained. Finally, the OL surface light source can uniformly and brightly illuminate the entire back surface 2a of the color liquid crystal display panel 2.

In particular, the light diffusing means such as the Fresnel prism 17 formed on the light reflecting surfaces 4b and 4c of the external light introducing prism 4 can freely change the reflection direction of the external light OL. The direction of taking in the external light OL can be freely set, and the effect of taking in the external light OL can be increased. Further, if the light diffusion sheet 18 is replaced with a prism sheet, the direction in which the external light OL is led out can be freely changed, and the same light diffusion effect can be expected. Further, if the light diffusion sheet 18 and the prism sheet are used in an overlapping manner, a diffusion effect of the external light OL over a wide range due to a synergistic effect can be expected. The light reflecting surfaces 4b and 4c of the external light introducing prism 4 may be mirror surfaces. However, by providing the light reflecting sheets 15 and 16, the reflection efficiency of the external light OL can be increased. If a silver film, an aluminum film, or the like is deposited on the substrate 4c, the reflection efficiency of the external light OL is further increased. In this case, the reflection sheets 15 and 16 become unnecessary.

[Second Embodiment of Backlight Device] Next, FIGS. 4 and 5 show a second embodiment of the backlight device 1 of the present invention.
In this case, in order to introduce the internal light IL into the internal light introduction surface 3a of the backlight light guide plate 3, the backlight is formed in a substantially wedge shape with a synthetic resin such as acrylic or glass. One or two internal light introducing plates 21,
The internal light introducing plates 21 and 22 are arranged such that microminiature light sources such as the light-emitting diodes 5 are opposed to the internal light introducing end faces 21a and 22a of the internal light introducing plates 21 and 22, respectively. Light diffusing means such as Fresnel-shaped prisms 23 and 24 are formed on the internal light reflecting surfaces 21b and 22b of these internal light introducing plates 21 and 22, and a light reflecting sheet is formed on the outermost reflecting surface 22b. Light reflecting means such as 25 are provided. Then, these internal light exit surfaces 21c
A light diffusing unit such as a light diffusing sheet 26 is arranged between the light guide plate 3 and the internal light introducing surface 3a of the backlight light guide plate 3, and further a light diffusing unit such as a Fresnel-like prism sheet 27 is arranged.

According to the second embodiment of the backlight device 1, the internal light I emitted from the light-emitting diode 5 and the like is provided.
L is the internal light introducing plate 2 from the internal light introducing end faces 21a, 22a.
1, 22 and these internal light reflecting surfaces 21
b and 22b, are widely reflected and diffused by light diffusing means such as Fresnel prisms 23 and 24 and light reflecting means such as light reflecting sheet 25, and then diffused widely by light diffusing means such as light diffusing sheet 26. After that, the light is further diffused by a light diffusion means such as a Fresnel prism 27. In this manner, a uniform surface light source is obtained by repeatedly reflecting and diffusing the internal light IL, and the internal light I
The L surface light source is finally introduced into the backlight light guide plate 3 from the internal light introduction end face 3a, and uniformly illuminates the entire back surface 2a of the color liquid crystal display panel 2 in the manner described in the first embodiment. Can be. Therefore, according to the second embodiment, regardless of the size of the color liquid crystal display panel 2, the back surface of the color liquid crystal display panel 2 is provided by a small and very small internal light source such as one or two light emitting diodes 5. 2a
Can be evenly and evenly illuminated.

Third Embodiment of Backlight Device Next, FIG. 6 shows a third embodiment of the backlight device 1 according to the present invention. In this case, an external light intake window is provided. 6
Is provided with a convex lens 31 so that the range S for taking in external light OL such as sunlight entering the external light introducing prism 4 from the external light introducing window 6 can be further expanded. is there.

Next, FIGS. 7 and 8 show the overall configuration of an electronic viewfinder 41 of a video camera incorporating the backlight device 1 of the present invention. Upper and lower divided lens barrels 43 and 44 are fixed in a main cabinet 42 fixed to the camera, and the color liquid crystal display panel 2 is vertically attached to the front ends of the lens barrels 43 and 44. The backlight light guide plate 3, the external light introducing prism 4, and the like are held by a prism holder 45 and arranged vertically on the front surface of the color liquid crystal display panel 2 in the main cabinet 42. It is fitted on the upper surface of the main cabinet 41. A circuit board 46 on which a drive circuit of the color liquid crystal display panel 2 is mounted is mounted horizontally above the upper lens barrel 43, and a circuit board 47 on which a micro light source such as the light emitting diode 5 is mounted. It is mounted horizontally below the lower lens barrel 44. A sub-cabinet 49 having an eye cap 48 attached to the rear end is attached to the rear end of the main cabinet 42, and a plurality of sub-cabinets 43, 44 are provided on the rear side of the color liquid crystal display panel 2 and inside the lens barrels 43, 44. An optical system 50 in which lenses and filters are arranged is incorporated. At this time, since the light emitting diode 5 and the like do not require a booster circuit such as a direct-type fluorescent tube, the circuit board 46
Of the backlight device 1 can be reduced in size and weight.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical concept of the present invention. For example, the illuminated member of the present invention is not limited to a color liquid crystal display panel, but can be applied to various members requiring back illumination. Further, the present invention is not limited to a backlight device of an electronic viewfinder of a video camera, but is applicable to backlight devices of various optical devices.

[0021]

The backlight device of the present invention configured as described above has the following effects.

According to the first aspect of the present invention, the external light introducing means is disposed on the internal light reflecting surface of the internal light introducing means disposed on the back surface of the illuminated member so that the external light can be efficiently taken in and the loss can be reduced. Since the illuminated member can be efficiently illuminated from the back without generating much light, even if the internal light source is turned off, the illuminated member can be illuminated sufficiently with only external light. it can. In addition, since the internal light source can be arranged on the internal light introducing end face of the internal light introducing means, it is possible to employ a micro light source such as a light emitting diode as the internal light source. Compared to the prior invention using a fluorescent tube,
High economic efficiency due to reduction of power consumption can be realized. If a micro light source such as a light emitting diode is used as an internal light source, a booster circuit for lighting a direct-type fluorescent tube is not required, and a circuit board is also reduced, thereby realizing a small and lightweight backlight device. be able to.
And if you take in the external light and use the internal light source together,
The member to be illuminated can be illuminated extremely brightly, and video shooting with a video camera or the like can be easily performed continuously for a long time.

According to a second aspect of the present invention, since the internal light source is constituted by one or a plurality of light emitting diodes, the size and weight of the entire view finder and the like due to the reduction in size and weight of the backlight device are combined with a high power saving effect. Can be realized.

According to the third aspect of the present invention, since the light diffusing means is provided between the back surface of the member to be illuminated and the internal light introducing means, the internal light and the external light can be diffused over a wide range to obtain a uniform surface light source. As a result, the member to be illuminated can be uniformly and brightly illuminated.

According to a fourth aspect of the present invention, since the light diffusing means is provided between the internal light introducing means and the external light introducing means, the internal light and the external light can be diffused over a wide range to obtain a uniform surface light source. Thus, the illuminated member can be uniformly and brightly illuminated.

According to a fifth aspect of the present invention, since the light reflecting means and / or the light diffusing means are provided on the external light reflecting surface of the external light introducing means, the external light is efficiently reflected and diffused to obtain a uniform surface light source. Accordingly, the illuminated member can be uniformly and brightly illuminated.

According to a sixth aspect of the present invention, the internal light emitted from one or a plurality of light emitting diodes is introduced into one or a plurality of substantially wedge-shaped internal light introducing plates, and the introduced internal light is subjected to these light. Light is reflected and / or diffused by the light reflecting means and / or the light diffusing means in almost the entire area in the length direction to obtain a uniform surface light source, and the uniform surface light source is introduced into the internal light introducing means to be illuminated. Since the member is illuminated, the member to be illuminated can be uniformly and brightly illuminated.

According to a seventh aspect of the present invention, since the convex lens is arranged in the external light introducing window of the external light introducing means facing the external light introducing end face, the range of taking in external light such as sunlight can be greatly expanded. Thus, even when the internal light source is turned off, the member to be illuminated can be illuminated sufficiently with only the external light, and a high power saving effect can be realized.

According to the eighth aspect of the present invention, the illuminated member is constituted by a color liquid crystal display panel, so that the photographed image can be displayed very bright in addition to the reduction in size and weight of the viewfinder of the video camera, and It is possible to realize a high-performance viewfinder with which eyes are hardly tired even after performing for a long time continuously.

[Brief description of the drawings]

FIG. 1 is a cross-sectional side view illustrating an optical path of internal light in a first embodiment of a backlight device in which the present invention is applied to backlighting of a color liquid crystal display panel.

FIG. 2 is a cross-sectional side view illustrating one introduction path of external light in the first embodiment.

FIG. 3 is a cross-sectional side view for explaining another introduction path of external light in the first embodiment.

FIG. 4 is a perspective view showing two internal light introducing plates and a light emitting diode in a backlight device according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional side view illustrating an internal light introduction path in the second embodiment.

FIG. 6 is a cross-sectional side view illustrating a range of taking in external light in a backlight device according to a third embodiment of the present invention.

FIG. 7 is an exploded perspective view of an electronic viewfinder of a video camera using the backlight device of the present invention.

FIG. 8 is a cross-sectional side view of the electronic viewfinder of the above in an assembled state.

[Explanation of symbols]

1 is a backlight device, 2 is a color liquid crystal display panel which is a member to be illuminated, 3 is a backlight light guide plate which is an internal and external light introducing means, 4 is an external light introducing prism which is an external light introducing means, and 5 is an internal light source. A light emitting diode, 6 is an external light intake window, 11 is a light diffusing surface as a light diffusing means, 12 and 13
Is a light diffusion sheet and a prism sheet as light diffusion means,
Reference numerals 15 and 16 denote light reflection sheets as light reflection means, 17 and 18 denote prisms and light diffusion sheets as light reflection means and light diffusion means, 21 and 22 denote internal light introducing plates, and 23 and 24 denote light diffusion means. A prism, 25 is a light reflection sheet as light reflection means, 26 is a light diffusion sheet as light diffusion means, 2
Reference numeral 7 denotes a prism sheet as a light diffusing unit.

Claims (8)

[Claims] 1. An internal light introducing means disposed on a back surface of a member to be illuminated, an internal light source disposed on an internal light introducing end face of the internal light introducing means, and an internal light reflecting surface of the internal light introducing means. Placed
A backlight device comprising an external light introducing means whose external light introduction end face faces an external light introduction window. 2. The backlight device according to claim 1, wherein said internal light source comprises a light emitting diode. 3. The backlight device according to claim 1, wherein a light diffusing means is provided between the back surface of the illuminated member and the internal light introducing means. 4. The backlight device according to claim 1, wherein a light diffusing means is provided between the internal light introducing means and the external light introducing means. 5. The backlight device according to claim 1, wherein a light reflecting means and / or a light diffusing means is provided on an external light reflecting surface of the external light introducing means. 6. One or a plurality of substantially wedge-shaped internal light introducing plates for introducing internal light to the internal light introducing end face of the internal light introducing means, and the internal light introducing end faces of these internal light introducing plates. One or a plurality of light emitting diodes disposed opposite to each other, and light reflection for reflecting and / or enlarging the internal light introduced into these internal light introducing plates over substantially the entire area in the longitudinal direction of these internal light introducing plates. The backlight device according to claim 1, further comprising a unit and / or a light magnifying unit. 7. The backlight device according to claim 1, wherein a convex lens is arranged on the external light introducing window facing the external light introducing end face of the external light introducing means. 8. The backlight device according to claim 1, wherein the illuminated member is formed of a liquid crystal display panel.