JPH05150236A - LCD lighting device - Google Patents

Abstract

PURPOSE:To enhance the utilizing efficiency of light and to improve the brightness of a front surface by making an intermediate reflecting body project forward among plural tube-like light sources and making one part of a diffusing plate approach the intermediate reflecting body. CONSTITUTION:The plural tube-like light sources 12 are arranged. Then, the intermediate reflecting plate 16 which reflects the light emitted to the side part from the light sources 12 toward a liquid crystal display plate 11 side is formed at the intermediate position of the adjacent light sources 12 of a reflecting plate 13 by being made to project forward. Besides, a curved recessed part 17 is formed at a part corresponding to the intermediate position between the adjacent light sources 12 of the diffusing plate 14. A metallic plate whose reflectivity is 90% is used for the plate 13 and the side wall 13a of the plate 13 is formed by being inclined so as to reflect the light from the light sources 12 forward. The plate 16 is obtained by bending and forming one part of the plate 13 into a round shape by giving a pair of inclined surfaces. Therefore, the arriving distance of the light to the plate 14 from the light sources 12 can be shortened more and illuminance on the plate 14 is made large. Besides, a backlight system corresponding to high brightness is realized in cooperation with the shape of the plate 13.

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 with a backlight, and more particularly to a liquid crystal lighting device used in a large color liquid crystal display.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device having a thin backlight mechanism has been widely used as a display device for a laptop computer or the like.

Currently, these lighting devices (backlights)
As shown in FIG. 6, a plurality of tubular light sources 2 such as cold cathode tubes and hot cathode tubes are arranged immediately below (rearward) the liquid crystal display panel 1, and a plurality of tubular light sources 2 for adjusting the light quantity are provided in front of the plurality of tubular light sources 2. A so-called direct type backlight system, in which a film 3 (writing curtain) and a diffusion plate 4 having a light diffusing function are sequentially provided, is often used as a high brightness system of a color LCD unit.

Reference numeral 5 in the drawing denotes a reflection case for reflecting the light emitted backward from the tubular light source 2 to the front.

[0005]

However, in the direct type backlight light type liquid crystal lighting device, the surface brightness of the diffuser plate 4 just above the center between the plurality of arranged tubular light sources 2 is the lowest brightness. When the light quantity adjusting film 3 attempts to make the brightness on the diffuser plate 4 uniform, the brightness at the center between the lowest tubular light sources 2 is smoothed. This is because the surface brightness of the diffuser plate 4 immediately above the tubular light source 2 having the highest brightness is forcibly reduced due to the dot-shaped dot pattern formed on the light quantity adjusting film 3 to cause the tubular light source 2 having the lowest brightness. This is because the surface brightness of the diffusion plate 4 immediately above the central portion between the two is smoothed.

Therefore, the utilization efficiency of light is lowered, and in particular,
It cannot be said that this is an optimal backlight system for low power consumption, which has been increasingly demanded in recent years, and especially color LCDs.
This is a problem from the standpoint of achieving the high brightness required by the unit.

In view of the above problems, it is an object of the present invention to provide a liquid crystal lighting device capable of improving the light utilization efficiency and improving the brightness on the diffusion plate.

[0008]

1 to 5, a tubular light source 12 for illuminating the liquid crystal display panel 11 from the rear side, and a rearward illumination from the tubular light source 12 are provided. Reflector 13 for reflecting light to the liquid crystal display 11 side
A diffuser plate 14 disposed in front of the tubular light source 12 for diffusing the direct light from the tubular light source 12 and the reflected light from the reflector plate 13 to the liquid crystal display plate 11, and uniformizing the amount of light to the diffuser plate 14. And a light amount adjusting body 15 for
A plurality of tubular light sources 1 arranged adjacent to the reflector 13 are provided.
An intermediate reflector 16 that reflects the light from the tubular light source 12 to the side toward the liquid crystal display panel 11 is formed at the intermediate position between the two, and the intermediate reflector 16 is formed between the adjacent tubular light sources 12 of the diffusion plate 14. The portion 17 corresponding to the intermediate position of the
It has been retracted so as to be close to 6.

According to a second aspect of the present invention, in the liquid crystal lighting device according to the first aspect, the distance between the center of the tubular light source 12 and the diffusion plate 14 is L, the diameter of the tubular light source 12 is D, and they are adjacent to each other. The distance between the centers of the tubular light sources 12 is P, and the diffusion plate 1
4 is F, the receding dimension at the intermediate position 17 is the intermediate reflector 1
When the top portion 16a of 6 is arranged at a distance of P / 2 from the center of the tubular light source 12, the top portion 16a of the intermediate reflector 16 is provided.
The separation distance Q between the diffuser plate 14 and the diffuser plate 14 is set so that the following equation is established.

[0010]

[Equation 2]

3 and 5, the tubular light source 12 according to the first aspect of the present invention is provided outside the effective display area L of the liquid crystal display panel 11, and an effective display is performed from the tubular light source. The light source reflector 21 that reflects the light traveling outside the region L to the effective display region L is provided.

[0012]

In the means for solving the problems according to claims 1 and 2 of the present invention, the forward light from the tubular light source 12 is directly fed to the tubular light source 1.
The backward light from 2 is reflected by the reflector 13 and then uniformly distributed forward by the light quantity adjuster 15, and further diffused by the diffuser 14 to illuminate the liquid crystal display panel 11 from the rear. .. In addition, the light to the side of the tubular light source 12 is directed to the intermediate reflector 16
Is reflected to the liquid crystal display panel 11 side. In this case, since the intermediate reflector 16 is formed so as to project forward, and the part 17 of the diffusion plate 14 corresponding to the intermediate position upper portion between the adjacent tubular light sources 12 is set back, the intermediate reflection from the tubular light source 12 is made. The reaching distance from the body 16 to the diffusion plate 14 can be reduced.

According to the third aspect of the present invention, the light emitted from the tubular light source 12 to the outside of the effective display area L is reflected toward the effective display area L side and indirectly illuminates the liquid crystal display panel 11. Then, the diffuser plate 1 corresponding to the portion directly above the conventional tubular light source 12 is used.
It is possible to prevent lamp streaks that have occurred on the No. 4 above.

[0014]

【Example】

(First Embodiment) FIG. 1 is a sectional view of a liquid crystal lighting device showing a first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part of the liquid crystal lighting device. As shown in the figure, the liquid crystal lighting device of this embodiment includes a tubular light source 12 that illuminates the liquid crystal display panel 11 from behind.
A reflecting plate 13 for reflecting the backward irradiation light from the tubular light source 12 toward the liquid crystal display panel 11 side; and a direct light from the tubular light source 12 arranged in front of the tubular light source 12 and the reflecting plate 13 A diffuser plate 14 for diffusing the reflected light to the liquid crystal display plate 11 and a light amount adjuster 15 for equalizing the amount of light to the diffuser plate 14 are provided, and a plurality of the tubular light sources 12 are arranged adjacent to the reflector plate 13. An intermediate reflector 16 that reflects light from the tubular light source 12 to the side toward the liquid crystal display panel 11 is formed at an intermediate position between the tubular light sources 12 so as to project forward, and the tubular light sources 12 adjacent to the diffusion plate 14 are formed. A curved concave portion 17 is formed in a portion corresponding to an intermediate position between the two.

The tubular light source 12 is composed of four cold cathode tubes having a diameter of 6.5 mm arranged at equal intervals.

The reflector 13 has a reflectance of 9 as shown in FIG.
A 0% metal plate is used. Side wall 1 of the reflector 13
3a is formed to be inclined so as to reflect the light from the tubular light source 12 forward.

The diffusion plate 14 is formed in a rectangular flat plate shape using, for example, milky white translucent acrylic, and is arranged in parallel with the display plate behind the display plate.

The light quantity adjusting body 15 is a film-like writing 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 tubular light source 12.

The intermediate reflector 16 is formed by bending a part of the reflection plate 13 into a mountain shape having a pair of inclined surfaces.

The top 16a of the intermediate reflector 16 has a distance L between the center of the tubular light source 12 and the diffuser plate 14, and the tubular light source 12
Is D, the distance between the centers of adjacent tubular light sources 12 is P,
When the receding dimension of the diffuser plate 14 at the intermediate position 17 is F, the diffuser plate 14 is arranged at a position horizontally spaced from the center of the tubular light source 12 by P / 2, and the top portion 16a of the intermediate reflector 16 and the diffuser plate 14 are disposed. The separation distance Q is set so that the following equation is satisfied.

[0021]

[Equation 3]

In the figure, H is a reflection plate 13 and a diffusion plate 14.
It shows the separation distance from.

Here, the expression (1) is set so that the light emitted from the lamp in the horizontal direction of the tubular light source 12 is effectively used, and as a result, the light utilization efficiency is improved.

Now, let us consider a light ray A emitted from a certain tubular light source 12a in the tangential direction of an adjacent tubular light source 12b.

In FIG. 2, assuming that the horizontal axis is x, the vertical axis is y, and the origin is (0, 0), y-tan (90 ° -θ) x = 0 is generally obtained by the tangent theorem. Therefore, in FIG. 2, the distance b in the y-axis direction of the (P, O) ray A from the centers of the adjacent tubular light sources 12b is: b = tan (90 ° −θ) · P (2) , The distance from the contact point M between the light ray A and the tube surface of the tubular light source 12 to the center of the tubular light source 12, that is, the radius D / 2 of the tubular light source 12,

[0026]

[Equation 4]

[0027] From the expressions (2) and (3), the following expressions (4) and (5) can be derived.

[0028]

[Equation 5]

Here, by substituting x = P / 2 into the equation (5), and considering the depth dimension F of the recess 17, the top 16a of the intermediate reflector 16 and the recess 17 of the diffuser plate 14 are formed. The separation distance Q can be derived as in equation (1). As a result, as shown in FIG. 2, the apex 16a located at the distance Q from the recess 17 of the diffuser plate 14 is shaded so that the light is emitted in front of the light ray A extending from the center of the tubular light source 12 to the tangential direction of the adjacent tubular light source 12. The light directly reaches the diffusing plate 14 or the concave portion 17 thereof, and among the lights emitted rearward of the light ray A, only the lights emitted by the adjacent tubular light sources 12 are emitted by the intermediate reflector 16. It is configured to be reflected in the forward direction.

The concave portion 17 is a portion of the diffusion plate 14, that is, a portion corresponding to an intermediate position between adjacent tubular light sources 12 is a curved surface having an arcuate cross section. This allows
The distance between the diffuser plate 14 and the intermediate reflector 16 is further shortened, and the brightness can be improved by shortening the optical path.

The light quantity adjusting body 15 has a similar shape in accordance with the curved shape of the diffusion plate 14.

When the tubular light source 12 is made to emit light in use in the liquid crystal lighting device having the above-described configuration, the light from the tubular light source 12 to the front is directly transmitted, and the light from the tubular light source 12 to the rear is once reflected by the reflection plate 13. After being reflected, the light quantity adjuster 15 uniformly distributes the light forward, and the diffuser 14 diffuses the light to illuminate the display plate from the rear.

At this time, the light to the side of each tubular light source 12 is reflected to the liquid crystal display panel 11 side by the intermediate reflector 16 as shown in FIG.

Here, the optical concept of reflection at the intermediate reflector 16 will be described.

The front surface (back surface) illuminance E (lx) of the light emitted from the tubular light source 12 is generally as follows.

E · Z = Kn · (Iθ / d) · cosθ (6) where, Kn: effective length of lamp / distance from the front surface of the lamp to the back surface of the diffusion plate Iθ: in the θ direction per 1 m of tubular tubular light source Luminous intensity (c
d) θ: vertical angle d: distance from the surface of the tubular tubular light source to the irradiated point (back surface of the diffuser plate) (m) Z: effective lamp length (m) In the present embodiment, effective lamp length Z = 0. 24m (φ
6.5 mm) and Kn = 0.78.

Further, as shown in FIG. 1, regarding the reflected light beam B from the tubular light source 12 by the reflector 13 and the intermediate reflector 16, the surface brightness R of the tubular light source 12 is R = 8000 (cd /
m ² ), diameter D = 0.0065 (m), total energy of luminous intensity Iθ of the tubular light source 12 = 8000 × 0.00
65 = 52 (cd), the reflected light component from the surface of the tubular light source 12 divides the surface of the tubular light source 12 into a set of point tubular light sources, and the luminous intensity of the tubular light source 12 in the normal direction per point tubular light source. Iθ is Iθ = R · 2πD / (number of divisions), and the distance d ₁ from the tube surface of the tubular light source 12 to the intermediate reflector 16 and the distance d ₂ from the intermediate reflector 16 to the back surface of the diffuser plate 14 are Originally, the back surface illuminance E ₀ of the diffusion plate 14
Can be roughly calculated as in equation (7).

E ₀ = {Iθ / (d ₁ + d ₂ ) ² } ρ (7) (ρ: reflectance of the reflector 13 and the intermediate reflector 16 = 0.
9) Therefore, by reducing the distance that the light emitted from the surface of the tubular light source 12 reaches the surface (rear surface) of the diffusing plate 14 by being reflected by the reflecting plate, that is, d ₁ + d ₂ ,
Based on the equation (7), the back surface illuminance E ₀ of the diffusion plate 14 can be increased.

Accordingly, the inclined intermediate reflector 16 is arranged between the tubular light sources so as to project forward of the reflector 13 and corresponds to the intermediate position between the adjacent tubular light sources 12 of the diffusion plate 14. By forming the concave portion 17 in the portion, d ₁
By reducing + d ₂ , the back surface illuminance E ₀ between the tubular light sources of the diffusion plate 14 can be increased.

The distance between the center of the tubular light source 12 and the diffuser plate 14 is L, the diameter of the tubular light source 12 is D, the distance between the centers of adjacent tubular light sources 12 is P, and the top of the intermediate reflector 16 is described. When 16a are equidistant from the center of the tubular light source 12 at a distance of P / 2, the top 1 of the intermediate reflector 16
The separation distance Q between the 6a and the recess 17 of the diffusion plate 14 is

[0041]

[Equation 6]

Since the setting is made as follows, the diffusion plate 14
Conventionally, of the light emitted rearward of the light ray A that goes from the center of the tubular light source 12 to the tangential direction of the adjacent tubular light source 12 by grazing the apex 16a at the separation distance Q from the concave portion 17 of
Light that cannot be effectively used as the surface brightness of the diffusion plate 14 can be reflected to the liquid crystal display panel 11 side only by irradiating the plurality of tubular light sources 12 with each other.

This light is emitted mainly in the oblique front direction of the tubular light source 12, and contributes to the portion of the diffuser plate 14 where the brightness is the lowest, that is, the recess 17 brightness up. Therefore, the brightness of the diffusion plate 14 can be improved as a whole.

(Second Embodiment) FIG. 3 is a sectional view of a liquid crystal lighting device showing a second embodiment of the present invention.

The liquid crystal lighting device of the present embodiment has a tubular light source 1.
2 is provided outside the effective display area L of the liquid crystal display panel 11, and is provided with a C-shaped metal light source reflector 21 that reflects the light traveling from the tubular light source 12 outside the effective display area L to the effective display area L. Is. In the figure, 22 is a light scattering substance, and it is desirable to form the ends densely and the center roughly. Further, 23 is a plastic chassis.

According to this embodiment, not only the same effect as the first embodiment is obtained, but also the light source 12 indirectly illuminates the effective display area L, so that the lamp stripes can be eliminated and the uneven brightness can be reduced. ..

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 first embodiment, the intermediate reflector 16
Was formed in a mountain shape having a pair of inclined surfaces, but FIG.
The tubular light source 12 may be formed in a curved shape.
It goes without saying that the shapes of the intermediate reflector 16 and the recess 17 can be determined by the luminous intensity of the light emitted from the direction.

Further, in the second embodiment, the intermediate reflector 16 is simply formed so as to project on the reflection plate 13 and the recess 17 is formed on the diffusion plate 14. However, as shown in FIG. 5, the diffusion plate 14 is inclined. A pair of wedge-shaped illuminating devices are arranged adjacent to each other so that the tips 24 thereof are abutted, and the tips 24 are attached to the intermediate reflector 16.
It may be used as the top 16a or the recess 17. In addition,
Reference numeral 25 in FIG. 5 denotes a support member that supports the diffusion plate 14.

[0050]

As is apparent from the above description, according to the first and second aspects of the present invention, the lateral light from the tubular light source is directed to the liquid crystal display panel side at the intermediate position between the adjacent tubular light sources of the reflector. Since an intermediate reflector that reflects light is provided and the part of the diffuser plate that corresponds to the intermediate position between the adjacent tubular light sources is retracted, the light reaching distance from the tubular light source to the diffuser plate can be further reduced, and the diffuser The illuminance on the plate becomes large, and the backlight system can be realized in correspondence with the above-mentioned shape of the reflecting plate to cope with high brightness, and the effect is great.

As a result, the yield in mass production is improved, the cost is reduced, and the effect is great.

According to the third aspect, it is possible to prevent the generation of lamp stripes on the illumination surface, and it is possible to improve the display quality by reducing uneven brightness.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of a liquid crystal lighting device.

FIG. 3 is a cross-sectional view of a liquid crystal lighting device showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a liquid crystal lighting device showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a liquid crystal lighting device showing another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional liquid crystal lighting device.

[Explanation of symbols]

 11 Liquid Crystal Display Plate 12 Tubular Light Source 13 Reflector 14 Diffuser 15 Light Quantity Adjuster 16 Intermediate Reflector 21 Light Source Reflector

Claims (3)

[Claims] 1. A tubular light source for illuminating a liquid crystal display plate from the rear, a reflector for reflecting illumination light from the tubular light source to the liquid crystal display plate side, and a tubular light source arranged in front of the tubular light source. The diffuser plate for diffusing the direct light and the reflected light from the reflector plate to the liquid crystal display plate, and a light amount adjusting body for making the light amount to the diffuser plate uniform, the tubular light source is arranged in a plurality,
At the intermediate position between the adjacent tubular light sources of the reflector, an intermediate reflector that reflects the light from the tubular light sources to the side of the liquid crystal display plate is formed to project forward, and the adjacent tubular light sources of the diffuser plate are formed. A liquid crystal lighting device, wherein a portion corresponding to an intermediate position between the two is retracted so as to be close to the intermediate reflector. 2. The liquid crystal lighting device according to claim 1, wherein the distance between the center of the tubular light source and the diffusion plate is L, the diameter of the tubular light source is D, the distance between the centers of adjacent tubular light sources is P, and the diffusion plate. When the top of the intermediate reflector is arranged at a distance of P / 2 from the center of the tubular light source, the separation distance Q between the top of the intermediate reflector and the diffuser plate is A liquid crystal lighting device, characterized in that the formula is set to hold. [Equation 1] 3. The tubular light source according to claim 1, wherein the tubular light source is provided outside the effective display area of the liquid crystal display plate, and a light source reflector that reflects light traveling from the tubular light source outside the effective display area to the effective display area is provided. A liquid crystal lighting device characterized by the above.