JPS62169105A - Planar light source - Google Patents

Abstract

PURPOSE:To enlarge a planar light source in size and to thin in thickness, by housing the light source in a light leading section, making the thickness of a light guiding section smaller than that of the light leading section, leading most of the rays of light of the light source to the light guiding section under a condensed state, and causing the primary reflecting light from the side facing the light emitting surface to have a directed angle against the light emitting surface. CONSTITUTION:Even when the thickness of the light guiding section 4 of a light emitting panel B is made thinner than the diameter of a fluorescent lamp A which is a light source, led rays of light are reflected (primary reflecting light) by a plane of reflection on the side facing a light emitting surface 3 and directly reach the light emitting surface 3 and, therefore, the light leading efficiency of the rays of light 1 of the light source is not lowered. Moreover, since a light leading section 2 only is made thicker and the fluorescent lamp A is housed in the light leading section 2, most of the rays of light 1 emitted from the lamp A are condensed by means of the light reflecting layer 8 of the light leading section surrounding the fluorescent lamp A and led to the light guiding section 4. The light leading efficiency of the rays of light 1 can extremely be improved. The light emitting surface 2 and light leading section 2 form a recess part and a liquid-crystal display 7 is put in the recess part. Therefore, thickness of the whole display including a back light source can be made smaller and weight of the whole body can be reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a surface light source, and more specifically, it is suitable for being installed as a light source for various displays, especially as a back light source on the back side of a liquid crystal display cell, and has a remarkable light output efficiency. Relating to an improved surface light source.

(Prior Art) In recent years, with the rapid development of the information society, terminal devices that transfer various types of information to humans have come into widespread use.

Most of these terminal displays are so-called CRTs, and although these CRTs have many advantages such as excellent color display functions, image adjustment functions, and fewer signal cables, they do not require high-voltage power supplies or thick walls. Because it requires a display tube made of glass, it is large, heavy, and takes up space, so various flat displays have been proposed, mainly for wall-mounted, portable, and portable displays. Of these, the most promising is a liquid crystal display that can be driven by an IC and can be easily colored.

(Problems to be solved by the invention) Conventional liquid crystal displays have a light-reflecting layer on the back and display information using external light from the front, and do not require a special light source. Widely used as displays for desktop calculators, battery-powered calculators, watches, etc. However, when such liquid crystal displays are used in terminals or televisions instead of conventional CRTs, the viewing angle, contrast, and display quality are poor due to insufficient brightness, especially for 10- to 12-inch LCDs. Make the size larger than 8
When used for large-capacity display of about 20 to 25 lines of 0 characters, problems arise in terms of display quality.

Furthermore, since it does not have a special light source, its display quality is affected by changes in external light environment conditions, and it has the disadvantage that it completely loses its display function in the absence of external light.

In order to solve these problems, there has recently been much research into backlight sources installed on the backside of liquid crystal displays. These backlight sources include organic dispersion type EL,
Various products have been proposed, such as thin-film EL, those using light emitting diode arrays, those that combine a light source such as a fluorescent lamp or lamp with a light guide plate, a Fournel type light guide plate, and a lighting box, but for large displays. However, there is no known material that is satisfactory in terms of uniformity, light efficiency, color rendering properties, etc.

Among these, a promising method is a method in which a light source such as a fluorescent lamp is installed on the side of a translucent panel such as an acrylic board, and light is emitted from one side of the panel. Firstly, if the panel is made thinner than the diameter of the fluorescent lamp, there is a problem that the light guide efficiency will be significantly reduced.Secondly, most of the introduced light is straight light parallel to the light emitting surface, so the light emitted from the light emitting surface is There is a problem of low efficiency, and a third problem is that the larger the panel is made, the more the difference in illuminance occurs between the vicinity of the light source and the center of the panel.

Therefore, the main object of the present invention is to provide a surface light source that is large enough to replace a CRT, that allows the light output panel to be made thin regardless of the size of the light source such as a fluorescent lamp, and that has improved light output efficiency. be.

These objects of the present invention have been achieved by the following invention.

(Means for solving the problems) That is, the present invention consists of a light source and a light emitting panel,
The light-emitting panel includes a light guide section that introduces light from a light source, a light guide surface, and a light reflection layer that reflects the introduced light.

In a surface light source consisting of a light guide section that guides introduced light to a light output surface and a light output surface, the light source is enclosed in the light guide section, the thickness of the light guide section is smaller than the thickness of the light guide section, and the light reflective layer is is a surface characterized by having a shape in which most of the light source light is focused and introduced into the light guide part, and the primary reflected light from the side opposite to the light exit surface is oriented at an angle with respect to the light exit surface. It is a light source.

(Preferred Embodiments) Next, the present invention will be described in further detail with reference to the accompanying drawings that schematically show preferred embodiments of the surface light source of the present invention.

FIG. 1 shows a cross-sectional view of one example of the surface light source of the present invention, and FIG.
The figure shows a plan view thereof, and FIG. 3 shows a cross-sectional view of a conventional surface light source.

A conventional surface light source using an acrylic plate or the like has a light guide section (light guide surface 6 ) is attached with a light source A such as a fluorescent lamp, and has the disadvantage that if the thickness of the light output panel B is made thinner than the diameter of the fluorescent lamp A, the introduction efficiency of the light source light 1 decreases. It is also known that the light source A is provided on a different plane from the light emitting panel B, and the light source light is reflected and introduced parallel to the light emitting panel B. If it is thinner than the diameter,
The introduction efficiency of light generated from light source A is low.

Also, if the light output panel B is made thicker, the light guide efficiency will improve, but
This does not meet the current trend toward thinning and weight reduction. In addition, since a large proportion of the light introduced from light source A is light that travels straight through light output panel B parallel to the light output surface, there is a problem that the light output efficiency from light output surface 3 is low, and furthermore, the light output near light source A The illuminance of the surface 3 was high, and the further the distance from the light source A, the lower the illuminance, and the illuminance was non-uniform over the entire light emitting surface 3.

The surface light source of the present invention solves the problems of the prior art as described above, and as schematically shown in FIGS. 1 and 2, it consists of a light source A and a light emitting panel B. It consists of a light guide section 2 that introduces the light source light 1, a light guide section 6, a light reflecting surface 8 that reflects the introduced light 1, a light guide section 4 that guides the introduced light to the light output surface 3, and the light output surface 3. The light source is enclosed in the light guide part, the thickness of the light guide part is smaller than the thickness of the light guide part, and the light reflecting surface prevents most of the light source light 1 from being directly introduced into the light guide part 4. , is introduced into the light guide section 4 as reflected light 5, and is characterized by a shape in which it is reflected at an angle oriented with respect to the light exit surface 3.

With the above configuration, even if the thickness of the light guide section 4 of the light output panel B is made thinner than the diameter of the fluorescent lamp A that is the light source, the introduced light will be transmitted to the reflective surface opposite to the light output surface. (-order reflected light) and directly reaches the light emitting surface, so that the light guide efficiency of the light source light l is not reduced.As shown in the example shown in the figure, only the light guide part 2 is made thicker to make the fluorescent lamp A. By including this in the light guide section 2, most of the light l emitted from the fluorescent lamp A is focused by the light reflection layer 8 of the light guide section that surrounds the fluorescent lamp A, and is introduced into the light guide section 4. Because you can
The light guiding efficiency of the light source light l can be significantly improved compared to the conventional example (shown in the third figure).

Furthermore, in the example shown in the third figure, most of the light source light 1 sent to the light emitting surface 3 of the light emitting panel B is straight light that is parallel to the light emitting surface 3, so the proportion of light that reaches the light emitting surface 3 is small. As the distance from the light source increases, the component of repeatedly reflected light (higher-order reflected light) becomes the majority, and the light efficiency decreases. In the case of a surface light source, most of the light source light 1 is focused around the light source, reflected by the light reflection layer 8 provided on the outside of the light output panel B, and oriented at an angle with respect to the light output surface 3. Since the primary reflected light that reaches directly to the light output surface 3 is used, there is little optical loss along the way.

The light output efficiency of the light 1 introduced into the light guide section 4 is significantly improved, and uniform illuminance can be provided over the entire light output surface 3 due to the design of the reflective surface. Specifically, for example, it is possible to combine two or more light sources to achieve uniform illuminance.

Further, even if the light source is a single tree, it is possible to make the illuminance uniform without any distance difference from the light source, and it is also possible to provide an arbitrary illuminance distribution.

Such an effect can be achieved by providing a light reflection M8 on the outer surface of the light emission panel B excluding the light emission surface 3 and the light guide surface 6, and changing the angle and shape of the light reflection layer around the fluorescent lamp A, especially below, for example. By using a reflective lens shape such as an inclined surface, a concave or convex reflective lens shape, a Fresnel lens shape, or a microlens array shape, the amount of light reaching the light emitting surface 3 of the light source A can be freely changed. , the amount of light reaching the light emitting surface 3 can be made uniform.

The light emitting panel B that exhibits the effects of the present invention as described above is:
It can be formed from any material with excellent translucency, such as glass material, but from the viewpoint of ease of molding and translucency, acrylic resin, acrylonitrile-styrene copolymer resin,
It is preferably formed from a translucent plastic material such as cellulose acetobutyrate resin, cellulose propionate resin, polymethylpentene resin, polycarbonate resin, polystyrene resin, polyester resin, or a composite material or copolymer material thereof.

In addition, reaction-curing epoxy resins, acrylic resins,
Methacrylic resin, urethane resin, etc. can also be used. As the molding method, any known method such as injection molding, compression molding, cast molding, cutting, polishing, etc. can be applied.

The light reflecting layer 8 of the light emitting panel B obtained in this way is
As shown in FIGS. 1 and 2, a light reflective metal such as nickel, aluminum, silver, or gold is deposited, sputtered, plated, or
It is formed by a silver mirror reaction, or by applying a reflective metal-containing paint, or by bonding a light-reflecting material such as an aluminum sheet to prevent the light source light 1 from leaking to the outside of the panel B. This is effective, including the effect of reflecting some of the leaked light back into the interior. Furthermore, it is also effective to form a layer with a light shielding agent or a light absorbing agent in unnecessary portions to prevent undesigned external light from entering. These reflective surfaces can be treated with scattering properties or use retroreflective materials such as glass beads, as long as they do not disturb the optical design, or they can also be diffusely reflected using uneven surfaces. It is possible.

Further, it is preferable to form a light diffusion layer 9 on the light emitting surface 3. For example, the light emitting surface may be sandpaper polished, sandblasted, honed, puffed, hairline processed, embossed, etc. during or after molding of the light emitting panel. A transparent resin layer that has been roughened through processing, press processing, etc., or contains a light-diffusing material such as white pigments such as silica, alumina, titanium oxide, zinc oxide, barium sulfate, and magnesium oxide, and glass beads with a specific diameter. By forming by coating methods such as dipping, roll coating, blade coating, and spray coating, or by adhering these layers, the light reaching the light emitting surface 3 is diffusely reflected or diffused, and the illuminance from the light emitting surface 3 is made uniform. The viewing angle can be expanded as well. In addition, such a light diffusing layer can be formed by preparing a ground glass plate, a light diffusing glass plate, a light diffusing plastic sheet, etc. separately and integrating them at the same time during molding, or by placing them between the liquid crystal self and the light emitting surface 3 during use. They may be mounted or bonded together, and it is also advantageous in terms of efficiency improvement and thermal design to arrange a light-reflecting condenser mirror or heat sink on the opposite side of the light guide section of the light source.

In the light emitting panel B as described above, the light emitting surface 3 and the light guide section 2 form a recess as shown in the first diagram, and by placing the liquid crystal display 7 in this recess, the back surface of the liquid crystal display 7 is illuminated. However, the liquid crystal display 7 can be clearly viewed regardless of the environment. Further, by forming the light emitting panel of the present invention into such a shape, the thickness of the entire display including the back light source can be reduced, and the overall weight can be reduced.

The present invention has been described above by exemplifying the preferred embodiments of the present invention, but the configuration is such that most of the light from the light source A is reflected light and can be introduced into the light guide section 4 as light having an angle with respect to the light output surface. The surface light source of the present invention is not limited to the shape shown in the drawings, but may have any shape as long as 0. For example,
The light guide portion 2 (light source A) of the light emitting panel B is not limited to the two locations shown in the figure, but may be one, three, or four locations, and the shape of the light emitting panel B is not limited to a rectangle, but may be a disc shape. ,
The shape of the light source may be any shape such as an elliptical plate shape, a polygonal shape, or a rectangular shape with rounded corners.
The shape is not limited to, and may be any shape, such as an annular shape, depending on the shape of the light emitting panel B.

(Function/Effect) In the surface light source of the present invention as described above, the light from the light source is not incident on the light guide section in parallel, but as reflected light having directionality, so that most of the incident light is The light can be directed at an angle with respect to the light emitting surface, and the light from the light source can be efficiently guided to the light emitting surface.

Further, in a preferred embodiment of the present invention, the light guide portion can be made thin regardless of the thickness of the fluorescent lamp used as the light source, so that the demand for thinner and lighter displays can be satisfied. For the same reason, the light guide part can be made thicker than the diameter of the fluorescent lamp so that more than half of the fluorescent lamp can be fitted into it, and the light guide part can be made thinner than the diameter of the fluorescent lamp, so that the light can be emitted from the fluorescent lamp. Since most of the light emitted can be collected and introduced into the light guide, the efficiency of using the light from the light source can be significantly increased even if the light guide is thinner than the diameter of the fluorescent lamp.

In addition, by forming a light reflective layer on the outer surface of the light emitting panel except for a part of the light emitting surface, and appropriately controlling the angle and shape of the light source, the light from the light source can be distributed uniformly over the entire light emitting surface. Therefore, the illuminance on the light exit surface can be made even more uniform.

(Example) .

Using polymethyl methacrylate resin (Parapet HR1 manufactured by Kyowa Gas Chemical Co., Ltd.), it has a shape as shown in Figs. 1 and 2, with a size of 240 mm x 180 mm, a light guide part thickness of 12 mm, and a light guide part thickness of 22 layers. A panel was molded by injection molding, and aluminum was vacuum-deposited on the outer surface except for the light-emitting surface and the light-guiding surface to form a light-reflecting layer. Further, glass beads (manufactured by Toshiba Ballotini) were kneaded with the above acrylic resin at a ratio of 10z1% to prepare a sheet having a thickness of 2ff and 1ml, and this was bonded to the light emitting surface. Two 15W fluorescent lamps were used as light sources, and they were fitted into the recesses formed in the light guide, and the upper surface was sealed with an aluminum sheet to provide a surface light source of the present invention.

When a liquid crystal display was placed on the light emitting surface of this surface light source and the surface light source was turned on, the liquid crystal display showed excellent viewing angles and contrast, and exhibited a high display function that was uniform throughout.

As described above, the surface light source of the present invention is very useful as a back light source for various displays such as liquid crystal displays.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a cross section of an example of a surface light source of the present invention, FIG. 2 corresponds to the plan view of FIG. 1, and FIG. 3 shows a cross section of a conventional surface light source. It is a figure shown diagrammatically. A; light source B; light output panel 1; light source light 2; light guide section 3; light output surface 4; light guide section 5; reflected light 6; light guide surface 7; liquid crystal display 8; light reflection layer 9; light diffusion layer

Claims (8)

[Claims] (1) Consisting of a light source and a light output panel, the light output panel includes a light guide section that introduces the light source light, a light guide surface, a light reflection layer that reflects the introduced light, and a light guide section that guides the introduced light to the light output surface. In a surface light source consisting of a light emitting surface and a light emitting surface, the light source is enclosed in a light guiding part, the thickness of the light guiding part is smaller than the thickness of the light guiding part, and the light reflecting layer focuses most of the light from the light source. What is claimed is: 1. A surface light source characterized in that the light is introduced into a light guide section and has a shape such that reflected light is oriented at an angle with respect to a light exit surface. (2) The surface light source according to claim (1), wherein the light emitting panel is configured such that the introduced light is reflected by a light reflecting surface on the side opposite to the light emitting surface and irradiates the entire light emitting surface. (3) The light emitting panel is made of a single light-transmitting plate, and the light guide section provided at at least one end of the light-transmitting plate is formed approximately at right angles to the light-emitting surface. The surface light source described in item (1). (4) The surface light source according to claim (1), wherein the surface of the light emitting panel excluding the light emitting surface and the light guiding surface is light reflective. (5) The surface light source according to claim (1), wherein the light emitting surface is light diffusive. (6) The surface light source according to claim (1), wherein the light emitting panel is rectangular and a light source is provided at at least one end thereof. (7) The surface light source according to claim (1), wherein the light emitting panel is disc-shaped and an annular light source is provided around the disc-shaped light emitting panel. (8) The surface light source according to claim (1), wherein the light emitting panel is integrally molded from a translucent resin.