JPH04225324A - Illuminating apparatus for liquid crystal - Google Patents

Abstract

PURPOSE:To effectively use light quantity which does not contribute fully for surface brightness of a diffuser in the plural light sources with each other. CONSTITUTION:A reflecting film 18 is formed inside of side wall sheathing tube 17 in light source 12. A light from a luminous element 16 to side direction is reflected by the reflecting film 18 and the diffuser 14 is irradiated with a reflecting light from the reflecting film 18. Thereby, brightness of the diffuser 14 is improved as a whole.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal lighting device (liquid crystal panel backlight) for illuminating a transmissive liquid crystal panel from the back side.

0002

2. Description of the Related Art In recent years, display devices having a thin backlight mechanism have been widely used as display devices for laptop-type personal computers and the like.

At present, these LCD lighting devices (backlights) include a plurality of light sources such as cold cathode tubes and hot cathode tubes (fluorescent lamps) behind (directly below) the liquid crystal display board (panel) 1, as shown in FIG. ) 2, and a light adjusting film (lighting curtain) 3 and a diffusion plate 4 having a light diffusing function were attached in front of the plurality of light sources 2. This backlight type lighting device structure is often used as a high-brightness compatible system, especially for color LCD units.

[0004] Reference numeral 5 in the figure is a reflecting portion that reflects the light from the light source 2 toward the rear and side toward the front.

[0005]

[Problem to be solved by the invention] However, the light source 1
In the so-called direct type back light system, which has a light amount adjusting film 3 having a light reflection pattern, the surface brightness of the diffuser plate directly above the center between the plurality of lamps 2 is the lowest in brightness. In such a configuration, when attempting to equalize the brightness on the diffuser plate with the lighting curtain 3, the brightness will be smoothed to the lowest brightness in the center between the lamps. This is because the brightness on the diffuser plate directly above the lamp 2 with the highest brightness is forced by the dot pattern formed on the lighting curtain 3 to the diffuser plate 4 directly above the central part between the lamps with the lowest brightness. This is because the brightness is smoothed to .

[0006] As a result, the light utilization efficiency decreases, and in particular,
It cannot be said to be optimal as a high-brightness type backlight system compatible with the low power consumption color LCD units that have been increasingly requested in recent years, and there are problems from the standpoint of achieving high brightness on the diffuser plate required by color LCD units. It was hot.

In view of the above-mentioned problems, the present invention provides an illumination device for a liquid crystal display that can effectively utilize the amount of light that does not directly contribute to the surface brightness of the diffuser plate by simply irradiating the light sources with each other as the surface brightness of the diffuser plate. For the purpose of providing.

[0008]

[Means for Solving the Problems] As shown in FIGS. 1 to 4, the means for solving the problems according to the present invention includes a light source 12 that illuminates a liquid crystal display panel 11 from behind, and a light source 12 that illuminates a liquid crystal display panel 11 from behind. a reflector 13 that reflects the light toward the display panel 11; a diffuser 14 disposed in front of the light source 12 that diffuses direct light from the light source 12 and reflected light from the reflector 13 to the liquid crystal display panel 11; A liquid crystal lighting device comprising a light amount adjustment body 15 that equalizes the light amount of the plate 14, in which a plurality of the light sources 12 are arranged, and each light source 12 is composed of a light emitting body 16 and an exterior tube 17 covering the light source 16. A reflective film 18 is formed on the inner surface of the side of the exterior tube 17 of each light source 12 to reflect the light from the light emitter 16 to the side. It is configured to irradiate onto the diffuser plate 14.

[0009]

[Operation] In the above problem solving means, when in use, the forward light from the light source 12 is directly reflected, and the backward light from the light source 12 is once reflected by the reflection section 13, and then reflected by the light amount adjusting member 15.
The light is distributed to the front by the diffuser plate 14, and further diffused by the diffuser plate 14 to illuminate the display board from the rear.

At this time, the amount of light radiated laterally from the light emitters 16 was conventionally only irradiated between adjacent light sources 12 and could not be effectively used as surface brightness of the diffuser plate 14; is reflected by the reflective film 18 on the inner surface of the side portion of the outer tube 17. This reflected light is scattered when passing through the front part of the exterior tube 17, and this scattered light is irradiated onto the diffuser plate 14 from between the light sources 12, contributing to increasing the brightness of the lowest brightness part.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a liquid crystal illumination device showing an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part showing the range of direct light from the light source to the back surface of the diffuser plate, and FIG. Similarly, FIG. 4 is an enlarged cross-sectional view of the main part showing component light reflected from the light source by the reflecting portion, and FIG. 4 is a diagram similarly showing the relationship between the light source and the reflective film.

As shown in the figure, the liquid crystal lighting device of this embodiment is installed in a laptop type personal computer, etc., and includes a light source 12 (fluorescent lamp) that illuminates a liquid crystal display panel 11 from the rear, and a light source 12 (fluorescent lamp) that illuminates a liquid crystal display panel 11 from behind. a reflecting section 13 that reflects the light irradiated to the rear toward the liquid crystal display board 11; The light source includes a diffuser plate 14 for adjusting the light intensity of the diffuser plate 14, and a light amount adjusting body 15 for making the light intensity of the diffuser plate 14 uniform.

The light source 12 includes a light emitter 16 as shown in FIG.
(filament) and the exterior tube 17 (fluorescent tube) that covers it
A straight cold cathode tube or hot cathode tube consisting of
Four are placed at regular intervals.

As shown in FIG. 4, an arcuate reflective film 18 is formed on the inner surface of the side of the outer tube 17 of each light source 12 to reflect the light emitted from the light emitter 16 to the side.
is configured so that the reflected light irradiates onto the diffuser plate 14 from between the light sources 12.

The reflective film 18 is a phosphor coated on the inner surface of the outer tube 17, and is formed by removing the phosphor coated on the entire inner surface of the outer tube 17 except for a region having a desired formation angle θ. It is an aperture type.

Here, the formation angle θ of the reflective film 18 is such that the amount of light that could not be effectively utilized as the luminance on the diffuser plate even including the component reflected by the reflecting portion is reflected by the reflective film 18 and diffused. In order to effectively improve the brightness on the board, the angle range is set as shown below.

The case where the light source pitch P=32 (mm) and the light source diameter D=6.5 mm will be explained below.

1) Regarding the angular range of light directly reaching the back surface of the diffuser plate 14 from the light source 12, the adjacent light source 1 in FIG.
It is sufficient that the range is smaller than the irradiation angle θ1 of the light C1, which is the tangent to the angle θ1 of the light C1. This θ1 is an angle based on the vertical direction of the light source 12, and in FIG. 2, the horizontal axis is x, the vertical axis is y,
If the origin is (0,0), then in general, y-tan(90°-θ1)・x=0 Therefore, in FIG. 2, b1 is b1=tan(90°-θ1)・P=tan(90°-
θ1)・32...(1) Also, D/2 (radius of light source 12) is

[0020]

[Math 1]

From equations (1) and (2), the following equation (3) and the value of θ1 can be derived.

[0022]

[Math 2]

2) As for the component light reflected from the fluorescent tube light source by the reflection section, as in 1), it suffices if the range is smaller than the irradiation angle θ2 of the irradiation light C2, which is tangent to the adjacent light source 12. That is, in FIG. 3, if the horizontal axis is x, the vertical axis is y, and the origin is (0,0), then generally, y-
tan (90°-θ2) x-(d-L) {1+tan
(90°-θ2)・tanθ2}=0 ∴y-tan
(90°-θ2)・x-2・(d-L)=0 where d
is the distance from the center of the light source 12 to the light amount adjustment body 15, and L is the distance between the reflection section 13 and the light amount adjustment body 15.

Therefore, in FIG. 3, b2 is also D/
2 (radius of light source 12) is

[0025]

[Math 3]

From equations (4) and (5), the following equation (6) can be derived.

[0027]

[Math 4]

Note that there are two solutions for θ2 that satisfy equation (6), but as shown in FIG. 3, the larger solution is the angle about the tangent C3, and the ray between C3 and C2 is Even if the light is reflected by the reflection part 13, it is not irradiated to the diffuser plate 14 side and does not contribute to the brightness on the diffuser plate 14. Therefore, we will take the smaller solution that satisfies equation (6).

From 1) and 2), the angle at which the reflective film 18 is formed is in the range of θ1 to (180−θ2) as measured from the vertical direction of the light source 12, as shown in FIG.

Note that the relationship between θ1 and θ2 is as shown in FIG.
θ1>θ2, and the reflective film 18 is formed so that its front side is more open than its rear side.

Note that the angle ranges of θ1 and θ2 mentioned above are examples of the minimum angle ranges, and it is also possible to widen both ends to a certain minute angle with respect to the vertical direction of the light source. Generally, when the light source pitch is P (mm) and the light source diameter is D (mm), equations (3) and (6) become as shown in equations (7) and (8) below, and the angular range is It is determined.

[0032]

[Math 5]

As shown in FIG. 1, the reflecting section 13 is formed into a box shape with an open front so as to accommodate the plurality of light sources 12, and its side walls are inclined so as to reflect the light from the light sources 12 forward. It is formed by

The diffusion plate 14 is made of, for example, milky-white translucent acrylic, is formed into a rectangular flat plate, and is disposed behind the display panel and parallel to the display panel.

The light amount adjusting member 15 is a film-like lighting curtain in which a dot pattern is formed on a 188 μm polyethylene terephthalate (PET) sheet by aluminum vapor deposition in accordance with the mounting position of the light source 12.

In the liquid crystal illumination device having the above structure, when the light source 12 is made to emit light during use, the light emitted from the light source 12 toward the front is directly reflected, and the light emitted from the light source 12 toward the rear is once reflected by the reflection section 13. After that, the light is uniformly distributed forward by the light amount adjustment body 15, and further diffused by the diffuser plate 14 to illuminate the display board from the rear.

At this time, the arc-shaped reflective film provided on the lateral inner surface of the exterior tube 17 of the light source 12 is as shown in FIGS.
Just by irradiating each other between multiple light sources 12, the diffuser plate 14
The amount of light that cannot be effectively used as surface brightness is reflected inside the exterior tube 17 of the light source 12.

Here, as shown in FIG. 4, since the reflective film 18 is formed so that the front part thereof is more open than the rear part, the light from the light emitting body 16 diagonally backward is transmitted through the reflective film. At 18, the light is directly reflected diagonally forward of the exterior tube 17. Then, this light is scattered while passing through the front part of the exterior tube 17, and is irradiated mainly in the diagonally forward direction of the light source 12.
This contributes to increasing the brightness of the portion of the diffuser plate 14 where the brightness is lowest. Therefore, the overall brightness of the diffuser plate 14 can be improved.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, in the above embodiment, the reflective film 18 is formed in an arc shape, but the present invention is not limited to this. For example, a part of the exterior tube 17 may be formed in a flat plate shape, and the reflective film 18 can be formed in a flat shape accordingly. The membrane 18 may also be formed into a flat plate.

[0041]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, a reflective film is formed on the inner surface of the side of the exterior tube of a plurality of light sources, so that conventionally, only a plurality of light sources irradiate each other. The light that could not be used effectively as surface brightness of the diffuser plate is
The light can be irradiated onto the diffuser plate from between the light sources. Therefore, there is an excellent effect that the overall brightness can be improved by increasing the amount of light diagonally in front of the light source and improving the brightness of the lowest brightness portion of the diffuser plate.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal lighting device showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part showing the range of direct light from the light source to the back surface of the diffuser plate.

FIG. 3 is an enlarged cross-sectional view of a main part showing component light reflected from the light source by a reflecting section.

FIG. 4 is a diagram similarly showing the relationship between a light source and a reflective film.

FIG. 5 is a cross-sectional view of a conventional LCD lighting device.

[Explanation of symbols]

11 Liquid crystal display board 12 Light source 13 Reflection part 14 Diffusion plate 15 Light amount adjustment body 16 Luminous body 17 Exterior pipe 18 Reflective film

Claims (1)

[Claims] 1. A light source that illuminates a liquid crystal display board from the rear, a reflecting part that reflects backward irradiation light from the light source toward the liquid crystal display board, and a reflecting part arranged in front of the light source that illuminates the direct light from the light source and A diffuser plate that diffuses the reflected light from the reflective section to the liquid crystal display board, and a light amount adjuster that equalizes the light amount of the diffuser plate, a plurality of the light sources are arranged, and each light source includes a light emitting body and a light emitting body. In the LCD lighting device, a reflective film is formed on the inner surface of the side of the exterior tube of each light source to reflect light from the light emitter to the side, and the reflective film reflects the reflected light. What is claimed is: 1. A lighting device for a liquid crystal display, characterized in that the lighting device is configured to irradiate light onto a diffuser plate between adjacent light sources.