JPH0432888A - Structure of face light source - Google Patents

Abstract

PURPOSE:To improve brightness on the surface of a display plate by forming a milky light diffusing plate and a light converging plate consisting of a parallel projected stripe face having semispherical continuous bodies or angular polygon continuous lines. CONSTITUTION:The diffusing plate 1 consists of an optical diffusing system applying a glass or plastic plate whose surface is roughened or a glass or plastic plate, a prism, a lens, etc., in which a filler with a proper grain size is blended. The light converging plate 2 consists of an aggregate of fine and semispherical condenser lens-like bodies or a parallel projected stripe face having a function similar to that of the aggregate and a cross section formed like a continuous semicircular curve or a continuous line of angular polygons such as half cuts of regular polygons. Consequently, the quantity of light obliquely advancing in a peripheral direction other than the direction vertical to an LCD element face can be reduced and brightness can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention irradiates a display board of a display device with light from a light source,
The present invention relates to a surface light source structure for improving brightness on a display panel.

[Prior Art] As a light display board, it is desirable to improve the brightness on the display board surface by preventing the luminous flux emitted from the display board from being diffused much in the lateral direction from the display board surface.

For example, a backlit liquid crystal display (hereinafter referred to as LC)
(abbreviated as D) as an example, LCDs are lighter and lighter than conventional cathode tube displays (CRTs).
They have the advantages of thinness and low power consumption, and are used in portable televisions, laptop computers, and word processors, and their demand is rapidly increasing. There are two types of LCDs: a reflective type without a backlight and a transmissive type with a backlight, but the reflective type is dark and has low contrast, making it difficult to see, so the transmissive type with a backlight has become mainstream. There is. Fluorescent lamps are the main light source for backlights, but they consume a lot of power, so they are required to be bright, ie, have high brightness, with as low power consumption as possible. Therefore, to ensure that light passes through the liquid crystal element surface as uniformly and effectively as possible, a reflector is installed on the back of the fluorescent lamp, and a light control film is installed on the front of the fluorescent lamp to eliminate differences in brightness depending on the position of the fluorescent lamp. In addition to the adjustment, a milky-white translucent light diffusing plate is attached.

However, even when using the above reflector and diffuser,
Light traveling in a direction perpendicular to the LCD element surface and light traveling obliquely in other peripheral directions are generated, and this peripheral direction light is completely wasted light with respect to the liquid crystal element surface.

[Problem to be Solved by the Invention] The inventor has studied a method of reducing the light directed toward the periphery as much as possible and improving the brightness of the display panel of a display device or the liquid crystal element board of an LCD, and has developed a method to diffuse the light toward the periphery. They came up with the idea that it would be better to refract the light in a direction perpendicular to the display board or liquid crystal element surface, and after repeated research and testing, they were able to complete the present invention.

[Means for Solving the Problems] According to the present invention, the front surface of the light source is formed from a milky white light diffusing plate and a transparent material, and the surface is a hemispherical continuum, or the cross section is a continuous line of a semicircular curve or a chevron-shaped polygon. A surface light source structure is provided which is characterized by being provided with a light condensing plate made of continuous parallel convex stripes.

That is, the light propagating from the light diffusing plate toward the periphery of the display surface is refracted by the light condensing plate in a direction perpendicular to the display surface as much as possible, thereby increasing the brightness of the display surface.

An embodiment of the present invention will be described based on the drawings. FIG. 1 is a cross-sectional view of a surface light source structure according to the present invention, in which a light condensing plate (2) is laminated on a diffuser plate (1).

The diffusion plate consists of an optical diffusion system using a glass or plastic plate with a rough surface, a glass or plastic plate containing a filler of an appropriate particle size, a prism, a lens, or the like.

In order to have the above function, the light condensing plate must be an aggregate of minute hemispherical condensing lens-like bodies, or a cross section with a similar function to a continuous semicircular curve, or, for example, a regular polygon cut in half. It is necessary to consist of parallel convex stripes with continuous lines of chevron-shaped polygons.

That is, for the above purpose, the light condensing plate is a parallel convex strip made of transparent glass or plastic and having a continuous semicircular curve in cross section, as shown in the partially enlarged plan view of FIG. or, as shown in the partially enlarged plan view of FIG. 3, the surface is preferably a hemispherical aggregate.

The distance between the centers of each of the minute lens-like bodies is 0,
The thickness is preferably 5 mm or less, and in the case of a liquid crystal color display, it is preferably 0.2 mm or less in order to avoid a moiré phenomenon due to light interference with the liquid crystal element.

In this embodiment, the diffuser plate and the light condensing plate are separately molded, but of course they may be molded integrally.

Figure 5 is a cross-sectional view of a fluorescent lamp with a backlight type light source equipped with a surface light source structure, taken in a direction perpendicular to the tube axis. , a light control film (3) is provided on the front surface, and on the light control film, a diffuser plate (1) and a light condensing plate (laminated on the diffuser plate) are installed.
2) is installed.

[Operation] Scattered light emitted from the diffuser plate enters the light condensing plate, and exits as refracted light from each microscopic condensing lens-like body of the light condensing plate. At this time, an incident light ray close to the interface (having a large incident angle) at the interface of the microlens-like body is refracted at the exit surface to a refraction angle smaller than the incident angle, as schematically shown in FIG. Therefore,
Of the light emitted from the diffuser plate, the proportion of light scattered around the diffuser plate is refracted inward as a whole, and the brightness of the liquid crystal element surface is improved.

The above explanation took the brightness improvement of a backlit LCD as an example, but it can also be applied to display boards, advertising boards, etc. in which characters, figures, etc. are illuminated by a light source from behind the board surface. It is also possible to improve the brightness of the

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Using the LCD backlight shown in FIG. 5, the surface brightness was measured in the case where the light condensing plate according to the present invention was attached and in the case where only the conventional diffuser plate was attached.

The surface light source is a cold cathode tube (diameter 7mmφ, lamp voltage 2OOV
, lamp current 6mmA), reflector plate (5) (white plastic molded product with a reflectance of 85% or more), light control film (3) (transmittance / It consists of a plastic film with reflectance that varies depending on the location), a diffuser plate (1) (plastic filled with white filler, total light transmittance 58%), and the long side parallel to the cathode ray tube is 200 mm, and the short side is It is formed into a rectangular shape of 140 mm.

As the light condensing plate (2), one whose surface had continuous parallel convex stripes whose cross section was a semicircular continuum with a diameter of 0.15 mm was used. The measurement positions are No. 3, the center of the surface light source rectangular plate, and 25 mm intervals from the center on the center line parallel to the short side, starting from the top. No, 2. No.

3. No, 4. No, it was set as 5.

The measurement results are shown in Table 1.

Table 1 (Unit: old t) Measurement position Example Comparative example (with light condensing plate) (without light condensing plate) No. 1 610 51 ONo.
2 685 58 ONo, 3
590 515No, 4 6
80 590 No.-5580500 Average 629 539 From Table 1, it can be seen that according to the present invention, the brightness is improved by 10% or more.

Note that when the above surface light source structure was incorporated into a color LCD, the LCD screen became clearer. When the distance between the parallel protrusions was set to 0.5 mm, waves of light shading occurred on the LCD screen, resulting in an unsightly screen.

[Effects of the Invention] According to the present invention, in the case of a liquid crystal surface light source, the brightness can be improved by 10% or more, so it is extremely useful for, for example, backlight type liquid crystal displays. It is extremely useful when applied to display surfaces illuminated by a light source from the rear, such as display boards and advertising displays, to improve brightness.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a surface light source structure according to the present invention, FIG. 2 is a partially enlarged perspective view of an embodiment of a light condensing plate, and FIG. 3 is a partially enlarged plan view of another embodiment of a light condensing plate. FIG. 4 is an explanatory view showing the function of the light condensing plate, and FIG. 5 is a cross-sectional view of the light source portion of a backlight type liquid crystal display equipped with the surface light source structure of the present invention. (1)...diffusion plate, (2)...condensing plate, (3)...
・Dimmer film. (4)...Fluorescent lamp, (5)...Reflector. Figure 1 ＼ゝIall＆ Figure 2 Figure 5

Claims (1)

[Claims] 1. A milky white light diffusing plate in front of the light source, and a parallel convex plate made of a transparent material, the surface of which is a hemispherical continuum, or whose cross section is a continuous line of semicircular curves or continuous lines of chevron-shaped polygons. A surface light source structure characterized by being provided with a light condensing plate consisting of a striped surface. 2. The distance between hemispherical centers of the hemispherical continuum of the light condensing plate is 0.
5mm or less, or the parallel spacing between parallel protrusions is 0.5mm
The surface light source structure according to claim 1, which is as follows. 3. Claim 1, characterized in that it is disposed between a surface light source and a liquid crystal element surface of a backlit color liquid crystal display, and the distance between hemispherical centers or the parallel interval between parallel protrusions is 0.2 mm or less. surface light source structure.