JPS62235905A - Plane optical source - Google Patents

Abstract

PURPOSE:To obtain a thin plane light source improved at the light projecting efficiency of a back light source of a liquid crystal display cell by guiding light radiated from a light source arranged in a light guiding part as reflected light having directivity through a light converging part connecting a photoconductive plane to the light guiding part and thinned in the direction to the light guiding part. CONSTITUTION:The size of the plane optical source can be approximately equal to that of a CRT and a light projecting panel can be thinned independently of the size of a light size such as a fluorescent lamp. Namely, the light source A is included in the photoconductive part 2, light converting part 10 connects the photoconductive part 2 to the light guiding part 4 and is thinned in the direction to the light guiding part 4 and a light reflecting plane 8 is formed so that light converged by the light converging part 10 is led into the light guiding part 4 as reflected light 5 and reflected at an angle directed to a light projecting plane 3. Even if the thickness of the light guiding part 4 is set up thinner than the diameter of the fluorescent lamp A, light led into the light projecting panel B reaches the light projecting plane 3 without reducing its photoconductive efficiency.

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 signals and cables, they do not require high-voltage power supplies or Since the display tube is made of thick glass, it is large, heavy, and takes up a lot of space.
Various types of flat 7-lat displays have been proposed mainly for use in portable devices, and among these, a particularly promising one is a liquid crystal display that can be driven by an IC and can be easily converted into color.

(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. It is widely used as a display for desktop calculators, battery-powered calculators, clocks, 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, the display quality is affected by changes in external light environment conditions, and there is a drawback that the two-display function is completely lost 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.

Furthermore, when using a fluorescent lamp as a light source, the amount of light from the fluorescent lamp is always uniform, so it is not possible to arbitrarily control the amount of light on the light emitting surface, and this is subject to individual differences among LCD display users and the usage environment. In addition, it is also desirable to adjust the wavelength from the light emitting surface to obtain light of an appropriate hue, considering not only the amount of light, that is, brightness, but also white balance, color rendering, and user eye strain. However, when the light source is a fluorescent lamp, only white light is emitted, which has the disadvantage that electrical adjustment is impossible.

Therefore, the main object of the present invention is to provide a surface light source that is large enough to be substituted for a CRT, whose light output panel can be made thin regardless of the size of a light source such as a fluorescent lamp, and which has excellent light output efficiency. .

Another object of the present invention is to provide a surface light source that is large enough to replace a CRT and whose light intensity and/or wavelength can be easily adjusted according to the light environment in which it is used and the individual differences of users. It is to provide.

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,
In a surface light source in which the light emitting panel is composed of a light guiding section, a light guiding surface, a light converging section, a light guiding section, a light reflecting layer, and a light emitting surface, the light source is enclosed in the light guiding section, and the light converging section is a light guiding section. and the light guide part, and the light guide part becomes thinner toward the light guide part, and the light guide part is thinner than the light guide part.

The light reflection layer is a surface light source characterized by having a shape in which most of the light from the light source is focused at the light converging part and introduced into the light guide part, and the reflected light is oriented at an angle with respect to the light output surface. be.

(Preferred Embodiments) The present invention will now be described in more 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.

Furthermore, although the light guiding efficiency can be improved by increasing the thickness of the light emitting panel B, 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.

In addition, when using a fluorescent lamp as a light source, the amount of light from the fluorescent lamp is always uniform, so it is not possible to arbitrarily control the amount of light on the light emitting surface. In addition, it is not only possible to deal with the amount of light, that is, brightness, but also with white balance, color rendering,
Considering the user's eye strain, it is desirable to adjust the wavelength from the light emitting surface to obtain light of an appropriate hue, but if the light source is a fluorescent lamp, only white light is emitted. The problem is that it is not possible to adjust electrically.

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. A light guide section 2 that introduces light source light l, a light guide surface 6, and introduced light 1
It consists of a light converging part lO1 that converges the light and guides it to the light guide part 4, a light guide part 4 that guides the introduced light l to a light output surface 3, a light reflection layer 8, and a light output surface 3, and the light source A is a light guide part 4. The light converging part 10 connects the light guide part and the light guide part, and becomes thinner toward the light guide part 4, and the light guide part 4 is thinner than the light guide part 2, preferably from the light source A. The light reflection surface 8 becomes thinner as the distance increases, and the light reflection surface 8 allows most of the light source light l not to be directly introduced into the light guide section 4, but to be converged by the light converging section 10 and introduced into the light guide section 4 as reflected light 5, and to emit light. It is characterized by a shape that reflects at an angle oriented with respect to the 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 is converged by the light converging section 10, and Reflected by the reflective surface 8 on the side opposite to the light emitting surface 3 (−th reflected light)
In addition, as shown in the example shown in the figure, only the light guide part 2 is made thicker so that the fluorescent lamp A can be placed in the light guide part z without reducing the light guide efficiency of the light source light l. By connecting the thick light guide part 2 and the thin light guide P14 with the light converging part 1O that reduces the thickness of the light guide, most of the light 1 emitted from the fluorescent lamp A is absorbed by the light guide surrounding the fluorescent lamp A. The light is condensed by the light reflection layer 8 and the light convergence part 0 of the light part 2, and the light guide part 4
Therefore, even if the light guide section 4 is made thinner than the conventional example (shown in the third figure), the light guide efficiency of the light source light l can be significantly improved.More preferably, the light guide section 4 By making the light thinner as it goes away from the light source, the introduced light can be uniformly distributed over the entire light exit surface 3.

Furthermore, in the example shown in the third figure, most of the light source light l 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 that 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 collected around the light source and at the light converging part 10, and is reflected by the light reflection layer 8 provided on the outer surface of the light output panel B and preferably having an inclined surface. Since the primary reflected light that has an angle oriented with respect to the light output surface 3 and directly reaches the light output surface 3 is used, there is little optical loss on the way, and the light output efficiency of the light 1 introduced into the light guide section 4 is increased. Furthermore, by slanting the reflecting surface, uniform illuminance can be provided over the entire light emitting surface 3. For example, it is possible to make uniform illumination by combining two or more light sources at both ends of light emitting panel B, and even if there is only one light source, it can be made uniform without any distance difference from the light source. In addition, it is also possible to provide an arbitrary illuminance distribution. Such an effect is achieved by providing a light reflecting layer 8 on the outer surface of the light emitting panel B except for the light emitting surface 3 and the light guiding surface 6, and changing the angle and shape of the light reflecting layer around the fluorescent lamp A, especially below it. For example, by using a reflective lens shape such as an inclined surface, an uneven shape, a concave or convex reflective lens shape, a Fresnel lens shape, a microlens array shape, etc., and further slanting the light reflective layer 8 of the light guide part, the light source A can be Since the amount of light reaching the light emitting surface 3 can be freely changed, the amount of light reaching the light emitting surface 3 can be made uniform.

Furthermore, in another preferred embodiment of the present invention, a light control filter 11 is provided around the light source A. This dimmer filter 1
1 can freely change the intensity and hue of the light from the light source A, and has the function of a light amount filter and/or a wavelength filter.

First of all, when the light control filter 11 is a light intensity filter, such a light intensity filter may have any configuration as long as it can adjust the amount of light emitted from the fluorescent lamp A. Preferred examples are as follows.

(1) f? A mode in which a layer that can control the light of the fluorescent lamp is formed around the F light lamp A, and the fluorescent lamp can be rotated.

In this embodiment, the above-mentioned layer becomes a light amount filter, and for example, a method of forming a layer capable of blocking or absorbing light such as black or other color, a method of forming a layer capable of reflecting light such as white or metallic color, etc. Either is fine. For such a light amount control layer, prepare a suitable ink or paint and apply it to the fluorescent lamp A.
Print around the area, or apply using methods such as rolling, spraying, electrostatic painting, baking, or inkjet methods.
Methods such as evaporation, CVD, sputtering, etc., or methods of forming a dyed layer in advance and dyeing it afterwards, forming it directly on a light source, or forming it on another transparent substrate in advance and bonding it together, etc. Of course, such a light intensity filter is not formed uniformly on the V wall of the fluorescent lamp A, but is formed in a linear, striped, or dot-like manner with appropriate density differences or concentration. Alternatively, light shielding material layers with different transmission densities may be formed stepwise or j! 1X is formed continuously. By forming the light amount filter 11 having such a configuration and rotating the fluorescent lamp A by appropriate means (not shown), the amount of light reaching the light output surface can be easily controlled.

(2) A mode in which the fluorescent lamp A is fixed and a rotatable light amount filter 11 is provided around it.

The principle of this example is also the same as the case (1) above. For example, a tubular filter 11 made of transparent glass or plastic is formed, and the density difference or concentration difference as in (1) above is formed on the surface of the tubular filter 11. A method may be used in which a light absorbing layer or a light reflecting layer is formed with the above-mentioned light field adjustment f! It may be wrapped with a film having f141!1 function, or it may be made into a flexible cylindrical sheet and fed by rotating on two axes. A light amount filter 11 having such a configuration is provided,
By rotating this filter 11 with a suitable means (not shown) such as a gear or a belt.

The amount of light reaching the light emitting surface can be arbitrarily controlled.For ease of explanation, a tubular filter has been used as an example, but the filter is not limited to these examples, and can be any shape and movable filter. It can also be a mechanism.

In addition, the dimmer filter 11 is a wavelength filter 1)
In some cases, the object of the present invention can be achieved by coloring the light absorption layer in the embodiments (1) and (2) above in a color that absorbs light of a specific wavelength. That is, the light control filter 11 may be colored with yellow, orange, red, blue, green, violet, or an intermediate color thereof in any order, and the light control filter 11 having such a configuration may be rotated according to the user's preference. Alternatively, by sliding it, the wavelength of light from the light source to the light output surface can be arbitrarily controlled. Furthermore, in television applications, this method is effective as the simplest way to perform hue adjustment, which is essential.

Furthermore, the light control filter ti used in the present invention can serve as the above-mentioned light amount filter and wavelength filter at the same time. In the configuration example 2, there is a method in which multiple filters are separated and stacked on top of each other and controlled independently.
Many adjustments can be made, such as the shade of color, making it suitable for more precise adjustments.

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 in terms of ease of molding and translucency, acrylic resin, acrylonitrile-styrene copolymer resin,
Cellulose acetobutyrate resin, cellulose propionone) 11 fat.

It is preferable to use a translucent plastic material such as polymethylpentene resin, polycarbonate resin, polystyrene resin, or 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-reflecting material such as nickel, aluminum, silver, or gold is vapor-deposited, sputtered, or plated on the light-emitting surface 3 and other parts of the light-guiding part 2 except for the light-guiding surface 6. ,
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. The transparent resin layer may be roughened by processing or press processing, or may contain a light-diffusing material such as white pigments such as silica, alumina, titanium oxide, zinc oxide, barium sulfate, or magnesium sulfide, or glass beads with a specific diameter. , 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 reduced. It is possible to make the image uniform and widen the viewing angle. 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 fJS design to arrange a light-reflecting condensing mirror or heat sink on the opposite side of the light guide section of the light source.

The light emitting panel B as described above has a light emitting surface 3,
The light guiding part 2 and the light converging part 10 form a recess, and by placing the liquid crystal display 7 in this recess,
The back surface of the liquid crystal display 7 can be illuminated to make the liquid crystal display 7 clearly visible 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.

Although the present invention has been described above by exemplifying the uninvented preferred embodiments, most of the light from the light source A is reflected light, the light is condensed by the light converging section 10, and the light has an angle with respect to the light output surface. As long as the configuration is such that it can be introduced into the light guide section 4 as
The surface light source is not limited to the shape shown in the figure, and may have any shape. The light emitting panel B may be formed in one place or in four places, and the shape of the light emitting panel B is not limited to a rectangle, but may be any shape such as a disk shape, an elliptical plate shape, a polygonal shape, a rectangular shape with rounded corners, etc.
The shape of the light source is not limited to the rod-shaped fluorescent lamp A, but also the light output panel B.
It may be of any shape, such as annular, depending on the shape of.

(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.

Also, for the same reason, the light guide part is made thicker than the diameter of the fluorescent lamp, more than half of the fluorescent lamp is fitted into it, and this light guide part is used as a light converging part! By connecting with the light guide part, the light guide part can be made thinner than the diameter of the fluorescent lamp, so that most of the light emitted from the fluorescent lamp can be collected and introduced into the light guide part.

Therefore, even if the light guide section is thinner than the diameter of the fluorescent lamp, the efficiency of using the light from the light source can be significantly increased.

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 controlling the angle and shape of those light sources, the light from the light source is distributed uniformly over the entire light emitting surface. Therefore, the illuminance on the light exit surface can be made even more uniform.

Furthermore, in a preferred embodiment of the present invention, by attaching a dimmer filter around the light source, the amount and/or wavelength of the light reaching the light emitting surface can be easily and arbitrarily controlled by the user. It is possible to use a display such as a liquid crystal display with the optimum amount of light (brightness/darkness) and/or optimum wavelength light (hue) for each user.

(Example) Example 1 Using polymethyl methacrylate resin (Paravet HR1 manufactured by Kyowa Gas Chemical Co., Ltd.), the shape was as shown in FIGS. 1 and 2, the size was 200 mm x 1201 mm, the center thickness of the light guide part was 4 mm, A light emitting panel with a peripheral thickness of 10 m and a light guide part having a thickness of 25 layers was molded by an injection molding method, 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, 10% by weight of glass beads (manufactured by Toshiba Ballotini) were kneaded with the above-mentioned acrylic resin 4 to prepare a 2 mm thick sheet, which 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.

Example 2 A tubular body with a rotation handle provided at one end was formed from the acrylic resin of Example 1, black dots were printed on the surface, and the number of dots (dots/) was continuously changed. We prepared two dimmer filters by pasting together polyvinyl chloride sheets. A 15W fluorescent light is installed in each of these,
The surface light source of the present invention is constructed by fitting the light output panel into the concave part of the light guide part of the light output panel of Example 1, sealing the upper surface with an aluminum sheet, and allowing the above-mentioned light control filter to rotate freely from the outside. did.

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 became a light-emitting type, with excellent viewing angles and contrast.

The entire display showed uniform and high display function. In addition, by gradually rotating the light control filter, the brightness and darkness of the liquid crystal display changed, making it possible to adjust the brightness of the display surface in response to individual differences and external light.

Example 3 In place of the dot-printed sheet in Example 2, a sheet with a width equal to the circumferential length of a fluorescent lamp and having seven highly transparent rainbow colors arranged vertically and continuously was used.

The other aspects were the same as in Example 2 to obtain a surface light source of the present invention. When this surface light source was used in the same manner as in Example 1, it was possible to change the hue of light on the display surface to various hues.

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 e; 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 10: light Convergence part 11; dimmer filter Fig. 1 Fig. 2

Claims (10)

[Claims] (1) In a surface light source consisting of a light source and a light emitting panel, where the light emitting panel consists of a light guiding part, a light guiding surface, a light converging part, a light guiding part, a light reflecting layer, and a light emitting surface, the light source is in the light guiding part. The light converging part connects the light guiding part and the light guiding part and becomes thinner toward the light guiding part, the light guiding part is thinner than the light guiding part, and the light reflecting layer is such that most of the light from the light source is A surface light source characterized in that the light is condensed by a light converging part and introduced into a light guide part, and has a shape having an angle such that reflected light is oriented with respect to a light output surface. (2) The surface light source according to claim (1), wherein the light guide portion becomes thinner as the distance from the light source increases. (3) The surface light source according to claim (1), wherein the periphery or part of the light guide section is provided with an uneven shape, and the light source light is introduced into the light converging section as reflected light. (4) The light emitting panel is made of a single light-transmitting plate, and the center of the light guide provided at at least one end of the light-transmitting plate is formed above the center of the light guide. A surface light source according to scope item (1). (5) 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. (6) The surface light source according to claim (1), wherein the light emitting surface is light diffusive. (7) 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. (8) 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. (9) The surface light source according to claim (1), wherein the light emitting panel is integrally molded from a translucent resin. (10) The surface light source according to claim (1), wherein a dimmer filter is attached to the periphery or a part of the light source.