JP2737114B2 - Surface light source - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source, and more particularly, to a light source of various displays, particularly suitable for being installed as a back light source on the back surface of a liquid crystal display cell, and has a remarkable light emission efficiency. It relates to an improved surface light source. (Prior Art) In recent years, with the rapid progress of the information-oriented society, terminal devices that transfer various kinds of information to humans have been used very frequently. Most of these terminal displays are so-called CRTs.These CRTs have many advantages such as excellent color display function and image adjustment function, and require less signal cables. Since a display tube made of thick glass is required, it has the drawbacks of being large, heavy, and taking up space. Therefore, various flat flat displays have been proposed mainly for applications such as wall-mounted, portable, and portable types. Of these, the most promising are
It is a liquid crystal display that can be driven by IC and is easy to colorize. (Problem to be Solved by the Invention) A conventional liquid crystal display is provided with a light reflection layer on the back surface,
A method of displaying information using external light from the front,
Since no special light source is required, it is widely used as a desktop calculator, a battery-powered calculator, a display of a clock or the like. However, when such a liquid crystal display is used in place of a conventional CRT as a terminal or a television, the viewing angle, contrast, and display quality are inferior due to insufficient brightness, particularly, 10 to 12 inches. The display quality is problematic for a large-capacity display of about 20 to 25 lines of 80 characters, with a size larger than that. In addition, since there is no special light source, there is a disadvantage that display quality is affected by changes in external light environment conditions, and the display function is completely lost in the absence of external light. In order to solve such a problem, recently, many studies have been made on a back light source installed on the back surface of a liquid crystal display. As these back light sources, organic dispersion type EL,
Various things such as a thin film EL, a light emitting diode array, a combination of a light source such as a fluorescent lamp or a lamp and a light guide plate, a Fresnel type light guide plate, and an illumination box have been proposed. There are no known compounds which are satisfactory in terms of uniformity, light efficiency, color rendering and the like. Among these, a promising method is known in which a light source such as a fluorescent lamp is provided on the side of a translucent panel such as an acrylic plate and light is emitted from one side of the panel. First, if the panel is thinner than the diameter of the fluorescent lamp, there is a problem that the light guide efficiency is significantly reduced. Secondly, since most of the introduced light is straight light parallel to the light exit surface, the light exits from the light exit surface. The third problem is that the efficiency is low, and the third problem is that the larger the panel, the lower the illuminance near the light source and the central portion of the panel. Therefore, a main object of the present invention is to provide a surface light source which is large enough to be substituted for a CRT, can make a light emitting panel thin regardless of the size of a light source such as a fluorescent lamp, and has excellent light emitting efficiency. The object of the present invention has been achieved by the following present invention. (Means for Solving the Problems) That is, the present invention relates to a surface light source including a light emitting panel (B) made of a translucent plate and a light source (A) installed at one or more side edges thereof. , The light emitting panel (B)
A light guide part (2) having a concave portion at a depth of at least one side end for housing the entire light source (A); a light guide surface having a thickness smaller than that of the light guide part (2); (3) is located below the upper end of the light guide section (2), and has a plate-shaped light guide section (4) having an inclined surface below the light guide section (2). The light-emitting panel (B) has a shape integrally molded from resin, and the entire outer peripheral surface of the light-emitting panel (B) except for the light-emitting surface (3) and the light-guiding surface (6) is light-reflective. The surface light source is characterized in that the light source (A) is housed therein, and the entire inner surface of the concave portion is a light guide surface (6) into which light from the light source is to be taken. (Embodiment of the Invention) Next, the present invention will be described in more detail with reference to the accompanying drawings which schematically show preferred embodiments of the surface light source of the present invention. FIG. 1 is a sectional view of an example of a surface light source according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view of a conventional surface light source. A conventional surface light source using an acrylic plate or the like is, as shown in FIG. 3, a light guide portion (light guide surface 6) of a light output panel B provided with a light reflection layer 8 in a portion except for the light output surface 3 and the light guide surface 6. ), A light source A such as a fluorescent lamp is additionally provided. If the thickness of the light emitting panel B is smaller than the diameter of the fluorescent lamp A, there is a disadvantage that the efficiency of introducing the light source light 1 is reduced. Further, a light source A is provided on a plane different from the light emitting panel B to reflect the light from the light source and to introduce the light in parallel to the light emitting panel B. However, similarly to the above, the light emitting panel B is When the diameter is smaller than the diameter, the efficiency of introducing light generated from the light source A is low. Further, if the light output panel B is made thicker, the light guide efficiency is improved, but this does not conform to the current tendency to reduce the thickness and weight. In addition, since the light introduced from the light source A occupies a large proportion of light traveling straight in the light emitting panel B in parallel to the light emitting surface,
There is a problem that the light emitting efficiency from the light emitting surface 3 is low. Further, the illuminance of the light emitting surface 3 near the light source A is high, and the illuminance decreases as the distance from the light source A is increased. The surface light source of the present invention has solved the above-mentioned problems of the prior art, and as shown schematically in FIGS. 1 and 2, a light emitting panel (B) made of a translucent plate and its light emitting panel (1). A light source (A) installed at more than one side end, and a depth at which the light emitting panel (B) houses the entire light source (A) at at least one side end. A light guide portion (2) having a concave portion, and a thickness smaller than that of the light guide portion (2);
And a light guide surface (3) located below the upper end of the light guide (2) and having a plate-shaped light guide (4) having an inclined surface below the light guide (2). A light-emitting surface (3) of the light-emitting panel (B) having a shape integrally molded from a light-transmitting resin;
In addition, the entire outer peripheral surface of the light emitting panel (B) except for the light guide surface (6) is made light-reflective, the light source (A) is housed in the concave portion, and the entire inner surface of the concave portion is a light guide surface ( 6). With the above configuration, even if the thickness of the light guide portion 4 of the light emitting panel B is smaller than the diameter of the fluorescent lamp A, which is the light source, the introduced light is not reflected on the reflecting surface on the side facing the light emitting surface. (Primary reflected light) and directly reach the light-emitting surface, so that the light guide efficiency of the light source light 1 is not reduced. Further, as shown in the example of the drawing, by increasing the thickness of only the light guide 2 and including the fluorescent lamp A in the light guide 2, the light 1 emitted from the fluorescent lamp A is emitted.
Can be condensed by the light reflecting layer 8 of the light guide section surrounding the fluorescent lamp A and can be introduced into the light guide section 4. Can be significantly improved. The light source light 1 sent to the light emitting surface 3 of the light emitting panel B is
In the example shown in FIG. 3, most of the light is straight light parallel to the light exit surface 3, so that the ratio of light reaching the light exit surface 3 is small, and the light is repeatedly reflected as the distance from the light source increases (higher-order reflected light). In the case of the surface light source of the present invention, most of the light source light 1 is a light source. And the primary reflected light that is reflected by the light reflecting layer 8 provided outside the light emitting panel B and reaches the light emitting surface 3 at an angle directed to the light emitting surface 3 is used. Therefore, light loss on the way is small, the light output efficiency of the light 1 introduced into the light guide portion 4 is remarkably improved, and uniform illuminance can be given over the entire light output surface 3 by designing the reflection surface. Specifically, for example, uniform illuminance can be obtained by combining two or more light sources, and even one light source can be made uniform without a perspective difference from the light source. Any illuminance distribution can be given. Such an effect can be obtained by providing the light reflecting layer 8 on the outer surface of the light emitting panel B except the light emitting surface 3 and the light guiding surface 6 and making the light reflecting layer around the fluorescent lamp A, particularly the lower light reflecting layer, an inclined surface.
Since the amount of light reaching the light emitting surface 3 from the light source A can be freely changed, the amount of light reaching the light emitting surface 3 can be made uniform. Light emitting panel B having the above-described advantageous effects of the present invention
Can be formed from any of the light-transmitting materials, for example, a glass material, but from the viewpoint of moldability and light-transmitting properties, acrylic resin, acrylonitrile-styrene copolymer resin, cellulose acetobutyrate It is preferably formed of a light-transmitting plastic material such as a resin, a cellulose propionate resin, a polymethylpentene resin, a polycarbonate resin, a polystyrene resin, a polyester resin, or a composite material or a copolymer thereof. Further, a reaction-solidifying epoxy resin, an acrylic resin, a methacrylic resin, a urethane resin, or the like can also be used. As a molding method, any of known methods such as injection molding, compression molding, cast molding, cutting, and polishing can be applied. The light reflecting layer 8 of the light emitting panel B thus obtained
As shown in FIGS. 1 and 2, a light-reflective metal such as nickel, aluminum, silver, or gold is vapor-deposited and sputtered on portions other than the light exit surface 3 and the light guide surface 6 of the light guide portion 2. It is formed by plating, silver mirror reaction, or the like, or by applying a reflective metal-containing paint, or by bonding a light reflective material such as an aluminum sheet, so that the light source light 1 leaks out of the panel B. Is effective, including the effect of reflecting some leaked light back inside. Also, it is effective as a means to form a layer with a light-shielding agent or a light absorbing agent for preventing unnecessary light from entering outside light, which is not designed. These reflecting surfaces can be treated in a scattering manner, or a retroreflective material such as glass beads can be used as long as the optical design is not disturbed. It is possible. In addition, it is preferable to form a light diffusion layer 9 on the light emitting surface 3. For example, sandpaper polishing, sand blasting, honing, buffing, hairline processing, embossing may be performed during or after forming the light emitting panel. , Immersing a transparent resin layer containing a white pigment such as silica, alumina, titanium oxide, zinc oxide, barium sulfate, and magnesium oxide, and a light diffusing material such as glass beads having a specific diameter. , Roll coating, blade coating, spray coating, etc.
Alternatively, by adhering these layers, the light reaching the light emitting surface 3 is diffusely reflected or diffused, thereby making the illuminance from the light emitting surface 3 uniform and widening the viewing angle. Such a light diffusing layer is prepared by separately preparing a ground glass plate, a light diffusing glass plate, a light diffusing plastic sheet, or the like, and integrating them at the same time during molding or using a crystal cell 7 at the time of use.
And the light emitting surface 3 may be placed or laminated.
It is also advantageous in terms of efficiency improvement and thermal design to arrange a light-reflecting condenser mirror or heat sink on the side of the light source opposite to the light guide. The light emitting panel B as described above has a light emitting surface 3 as shown in FIG.
And the light guide 2 form a recess, and the liquid crystal display 7 is placed in the recess to illuminate the back surface of the liquid crystal display 7 so that the liquid crystal display 7 can be seen clearly regardless of the environment. be able to. Further, by making 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. Although the present invention has been described by exemplifying a preferred embodiment of the present invention, most of the light from the light source A can be reflected light and introduced into the light guide section 4 as light having an angle with respect to the light exit surface. As long as it has a configuration, the surface light source of the present invention is not limited to the illustrated shape, and may have any shape. For example, the light guide part 2 (light source A) of the light emitting panel B is not limited to the two places shown in the figure, but may be one place, three places, or four places, and the shape of the light guide panel B is not limited to a rectangle. Any shape such as a disk shape, an elliptical plate shape, a polygonal shape, and a rectangular shape having a rounded corner may be used. May be used. (Example) Using a polymethyl methacrylate resin (Parapet HR, manufactured by Kyowa Gas Chemical Co., Ltd.), the size as shown in FIGS. 1 and 2 is 240 mm × 180 mm, the thickness of the light guide section is 12 mm, and the thickness of the light guide section is A 22 mm light-emitting panel was formed by an injection molding method, and aluminum was vacuum-deposited on the outer surface excluding the light-emitting surface and the light-guiding surface to form a light reflecting layer. Further, glass beads (manufactured by Toshiba Barotini) were kneaded with the above acrylic resin at a ratio of 10% by weight to prepare a 2 mm-thick sheet, which was bonded to the light emitting surface. Two 15 W fluorescent lamps were used as light sources, fitted into recesses formed in the light guide, and the upper surface was sealed with an aluminum sheet to obtain a surface light source of the present invention. When a liquid crystal display was mounted on the light emitting surface of the surface light source and the surface light source was turned on, the liquid crystal display exhibited a high viewing angle, a high contrast, and a uniform high display function. As described above, the surface light source of the present invention is very useful as a back light source for various displays such as a liquid crystal display. (Effect of the Invention) In the surface light source of the present invention as described above, the light from the light source is not incident parallel to the light guide portion but is incident as reflected light having directivity, so that most of the incident light is In addition, light having an angle directed to the light emitting surface can be obtained, and light from the light source can be efficiently guided to the light emitting surface. Further, in the preferred embodiment of the present invention, the light guide portion can be made thin regardless of the thickness of the fluorescent lamp as a light source, so that the demand for a thinner and lighter display can be satisfied. Further, for the same reason, the light guide portion is made thicker than the diameter of the fluorescent lamp, and the entirety of the fluorescent lamp is fitted therein, and the light guide portion can be made thinner than the diameter of the fluorescent lamp. Since most of the irradiated light can be condensed and introduced into the light guide, even if the light guide is thinner than the diameter of the fluorescent lamp, the light source light utilization efficiency can be significantly increased. In addition, a light reflecting layer is formed on the outer surface of the light emitting panel except for a part of the light emitting surface and the like, and by appropriately controlling the angle and shape of the light emitting panel with respect to the light source, light from the light source is uniformly distributed over the entire light emitting surface. Therefore, the illuminance on the light emitting surface can be made more uniform.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing a cross section of an example of a surface light source according to the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. It is a figure which shows the cross section of the surface light source of technology schematically. A; light source B; light-emitting panel 1; light-source light 2; light-guiding unit 3; light-emitting surface 4; light-guiding unit 5; reflected light 6; light-guiding surface 7; liquid crystal display 8; light-reflecting layer 9;

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References Japanese Utility Model Showa 53-159287 (JP, U)                 Showa Sho 53-33386 (JP, U)                 Actual opening Sho 51-31384 (JP, U)                 Shokai Sho 57-167478 (JP, U)                 Shokai Sho 59-14014 (JP, U)                 Jikken Sho53-37594 (JP, Y2)                 United States Patent 3464133 (US, A)

Claims (1)

(57) [Claims] A surface light source comprising a light-emitting panel (B) made of a light-transmitting plate and a light source (A) installed at one or more side edges thereof, wherein the light-emitting panel (B) has at least one side thereof. A light guide portion (2) having a concave portion having a depth to accommodate the entire light source (A) at an end portion; a light guide surface (3) having a thickness smaller than that of the light guide portion (2); A shape integrally molded from a light-transmitting resin so as to have a plate-shaped light guide portion (4) having an inclined surface below the light guide portion (2) and located below the upper end of (2). A light-emitting panel (B) except for the light-emitting surface (3) and the light-guiding surface (6) of the light-emitting panel (B). A surface light source characterized in that the entire inner surface of the recess is a light guide surface (6) into which light from the light source is to be taken. 2. The surface light source according to claim 1, wherein the light emitting panel is configured to irradiate the entire light emitting surface by being reflected by the light reflecting surface on the side facing the light emitting surface of the introduced light. 3. The surface light source according to claim 1, wherein the light emitting surface has a light diffusing property. 4. 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. 5. The surface light source according to claim 1, wherein the light emitting panel has a disk shape, and an annular light source is provided around the light emitting panel.