JP2732492B2 - Surface light source - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a surface light source, and more particularly, to a light source for various displays, particularly, a light source for a back surface of a liquid crystal display cell. The present invention relates to a surface light source having a significantly improved viewing angle of a display. (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
However, although these CRTs have many advantages such as excellent color display function, image adjustment function, and less signal cables, they require a high-voltage power supply and a display tube made of thick glass. Because of the drawbacks of being large, heavy, and taking up space, various flat-plate flat displays have been proposed mainly for applications such as wall-mounted, flexible, and portable types, and among these, particularly promising. These are liquid crystal displays that can be driven by ICs and are easy to colorize. (Problems to be Solved by the Invention) A conventional liquid crystal display has 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. Further, since there is no special light source, there is a disadvantage that the 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 surface of a translucent panel such as an acrylic plate and light is emitted from one surface of the panel. Although this method is promising, it does not solve the problem of the narrow viewing angle inherent in liquid crystal displays. As a solution to this problem, roughening the light emitting surface of the light emitting panel,
There is known a method of diffusing emitted light using a light diffusing agent such as alumina or glass beads. However,
In this method, the light diffusing property is insufficient, and the light diffusing agent also has a certain level of light absorbency. Problem arises. In addition, as the size of the display increases, the number of people observing the display increases, and as a result, even better light diffusivity, particularly light diffusivity to the left and right of the screen, is required.
There has been almost no response to such a demand for light diffusivity to the left and right. Furthermore, in this method, since a fluorescent lamp is used as a light source, there is a problem of the thickness of the light emitting panel. In other words, it is the thinnest state to install the fluorescent lamp on the side of the panel,
If the panel is thinner than the diameter of the fluorescent lamp, there is a problem that the light guide efficiency is significantly reduced, and since most of the introduced light is straight light parallel to the light output surface, the light output efficiency from the light output surface is low. There is. Furthermore, there is a problem that the larger the panel is, the more the illuminance between the light source and the center of the panel becomes. When a fluorescent lamp is used as the light source, the light intensity of the fluorescent lamp is always uniform, so that the light intensity of the light emitting surface cannot be arbitrarily controlled. Can't respond. In addition, not only light quantity, that is, light and dark, but also white balance and color rendering,
Considering the user's eye strain, it is also desirable to adjust the wavelength from the light emitting surface to obtain an appropriate hue light.However, when the light source is a fluorescent lamp, only white light is emitted, The disadvantage is that it is not possible to adjust it dynamically. Therefore, a main object of the present invention is to increase the viewing angle, which is an essential drawback of the liquid crystal display, particularly the left and right viewing angles with respect to a viewer, which is large enough to replace a CRT. It is an object of the present invention to provide a surface light source which can be reduced in thickness regardless of the size of a light source such as a fluorescent lamp, and which has excellent light emission efficiency. Another object of the present invention is to provide a surface light source that is large enough to replace a CRT and that can easily adjust the light amount and / or wavelength according to the light environment to be used and individual differences among users. To provide. The object of the present invention has been achieved by the following present invention. (Means for Solving the Problems) That is, the present invention comprises a light source and a light emitting panel, and the light emitting panel comprises a light guide surface, a light guide portion, a light reflecting layer, and a light output surface, and the light output surface has a large number. With a convex curved shape (lenticular 4's shape or fly's eye shape)
The light reflecting layer is provided so as to face the light emitting surface. (Preferred Embodiment) 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.
It is to be noted that, in order to facilitate the explanation, each of the drawings is not a uniform scale drawing of an original size, but is drawn with its length direction being compressed. FIG. 1 shows a cross-sectional view of one example of the surface light source of the present invention, FIGS. 2 and 3 show cross-sections of another example of the preferred surface light source of the present invention, and FIG. FIG. 5 shows a plan view of a surface light source, and FIG.
The figure shows a sectional view of a conventional surface light source. As shown in FIG. 5, a conventional surface light source using an acrylic plate or the like is a light guide portion (light guide surface 1) of a light guide panel B provided with a light reflection layer 4 in a portion except for a light guide surface 3 and a light guide surface 1. ), A light source A such as a fluorescent lamp is attached, and one component of the light from the light source A emits light (arrow) almost perpendicularly from the light emitting surface 3, so that the field of view of the liquid crystal display 5 provided thereon is provided. The angle is not improved, and if the light-emitting surface 3 is made to be light-diffusing by a light-diffusing agent to improve the viewing angle, the brightness of the light-emitting surface decreases as the light-diffusing property increases. Was. Further, due to the problem of the thickness of the light emitting panel, there is a drawback that when the thickness of the light emitting panel B is smaller than the diameter of the fluorescent lamp A, the efficiency of introducing the light source light 6 is reduced. Further, if the light output panel B is made thicker, the light guide efficiency is improved, but this does not conform to the current trend of thinning and lightening. In addition, the light introduced from the light source A has a large percentage of light traveling straight in the light emitting panel B in parallel with the light emitting surface, and thus has 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 was high, and the illuminance decreased as the distance from the light source A was increased, and the illuminance was uneven over the entire light emitting surface 3. When a fluorescent lamp is used as the light source A, the amount of light from the light emitting surface 3 cannot be arbitrarily controlled because the amount of light from the fluorescent lamp is always uniform. Inability to handle the usage environment. Also,
In consideration of not only the light amount, that is, light and dark, but also white balance, color rendering, and eyestrain of the user, it is desirable to adjust the wavelength from the light emitting surface 3 to obtain appropriate hue light. In this case, since only white light is emitted, there is a problem that it is impossible to electrically adjust the wavelength of the light. The surface light source of the present invention solves the above-mentioned problems of the prior art. As shown schematically in FIGS. 1 to 4, the light emitting surface 3 is not a flat surface but has many lenticular shapes. By using the fly's eye shape 11, the viewing angle of the liquid crystal display 5 arranged on the light emitting surface 3, particularly to the left and right, can be enlarged. Such a large number of lenticulars and fly eyes
Numerals 11 may be arranged in the light emitting surface 3 in any direction, that is, vertically, horizontally, or randomly. Further, the pitch width of the large number of lenticulars and fly eyes 11 is not particularly limited, but if the pitch width is too large, the light exit surface 3
Is lost, the integration with the display 5 is reduced, and the uniform diffusion of the emitted light becomes insufficient. On the other hand, if the pitch width is too small, the flatness of the light emitting surface 3 is sufficient, but the diffusion efficiency, particularly the diffusion efficiency to the left and right, is not preferable. According to the inventor's detailed research, although it depends on the size of the light emitting panel 3, it is generally 0.01 to 10 m.
m, preferably the flatness of the light emitting surface and the light diffusing property of the light emitting surface when the pitch is preferably 0.05 to 1.5 mm width, especially the light diffusing property to the left and right are the best, and furthermore, these pitch widths are arranged thereon. It has been found that the display function of the display is best exhibited when the pitch is substantially the same as the pixel pitch of the liquid crystal display 5. Further, in the preferred embodiment shown in FIG.
The light guide 7 is integrally formed at an end of the light guide panel B, and the light guide 7 is displaced upward from the horizontal plane of the light output panel B, for example, so that the entire thickness including the liquid crystal display 5 is reduced. Further, by making the reflecting surface 8 below the light guide 7 an appropriate shape or by giving an appropriate angle, the light 6 from the light source A can be transmitted to the light emitting surface 3 instead of the light parallel to the light emitting surface 3. The light at the directed angle can be sent to the light exit surface 3 via the light guide 2 and the viewing angle of the liquid crystal display 5 can be further expanded. With the above configuration, the light (arrow) emitted from the light emitting surface 3 is introduced even if the thickness of the light guide portion 2 of the light emitting panel B is smaller than the diameter of the fluorescent lamp A as a light source. The light is reflected (primary reflected light) on the reflection surfaces 4 and 8 on the side opposite to the light exit surface 3, reaches the light exit surface 3 directly, enlarges the viewing angle of the liquid crystal display 5, and guides the light source light 6. There is no reduction in efficiency. Further, the example shown in FIG. 3 is an example in which the light emitting surface 3 having a large number of lenticulars shapes and fly-eye shapes 11 of the light emitting surface 3 is entirely convexly curved, and the operation in the example shown in FIG. This has an effect, and the viewing angle of the display 5 can be further increased. Further, in the example shown in FIG. 3, the overall convex curved surface shape is only one, but this is divided into a plurality of portions, such as two or three, and a large number of lenticulars or fly surfaces are formed on the surfaces of the plurality of convex curved shapes. Eye shape 11 may be formed. With such a configuration, even if the curvature of the entire convex curved surface shape is large, it is not necessary to increase the thickness of the light emitting panel B accordingly. Does not occur. Further, in another preferred embodiment of the present invention, a dimming filter 9 is provided around the light source A. This dimming filter 9
Is capable of freely changing the intensity and hue of the light from the light source A, and has a function as a light amount filter and / or a wavelength filter. First, when the light control filter 9 is a light amount filter, such a light amount filter may have any configuration as long as it can adjust the amount of light emitted from the fluorescent lamp A. The preferred examples are as follows. (1) A mode in which a layer capable of controlling the light of the fluorescent lamp is formed around the fluorescent lamp A, and the fluorescent lamp is rotatable. In this embodiment, the layer serves as a light amount filter, for example, a method of forming a layer that can block light or absorb light, such as black or other colors, a method of forming a layer that can reflect light, such as white or metallic color, and the like. Either may be used. Such a light quantity control layer is prepared by preparing an appropriate ink or paint and printing it around the fluorescent lamp A, or applying it by a method such as brush, roll, spray, electrostatic coating, baking, and ink jet method. Or a method such as vapor deposition, CVD, sputtering, etc., or a dyeing layer is formed in advance, and it is formed directly on the light source by a method of dyeing later, or it is formed on another transparent substrate in advance and bonded And the like. Of course, such a light amount filter is not formed uniformly on the tube wall of the fluorescent lamp A, but is formed by giving an appropriate density difference or density difference in a linear, striped, or dot shape, or by transmitting light. Light shielding material layers having different concentrations are formed stepwise or continuously. By forming the light amount filter 9 having such a configuration and rotating the fluorescent lamp A by an appropriate means (not shown), the light amount reaching the light emitting surface can be easily controlled. (2) An embodiment in which the fluorescent lamp A is fixed and a rotatable light amount filter 9 is provided around the fluorescent lamp A. The principle of this example is exactly the same as that of the above (1),
For example, a method in which a tubular filter 9 made of transparent glass or plastic is formed, and a light absorbing layer or a light reflecting layer having a density difference or a density difference as described in (1) above may be formed on the surface thereof. Further, after the above-mentioned tubular body is provided, a film or the like having the above-mentioned light amount adjusting function may be wound around the surface thereof. It is also possible to form a flexible tubular sheet and rotate it about two axes to feed it. By providing the light amount filter 9 having such a configuration and rotating the filter 9 by a suitable means (not shown) such as a gear or a belt, the light amount reaching the light emitting surface can be arbitrarily controlled. Although the above description has been made by exemplifying a tubular filter for ease of explanation, the filter is not limited to these examples, and may have any shape and movable mechanism. Further, when the light control filter 9 is a wavelength filter, the object of the present invention is achieved by coloring the light absorbing layer in the above-described embodiments (1) and (2) to a color that absorbs light of a specific wavelength. it can. That is, the light control filter 9 is set to yellow, orange, red, blue, green,
It may be colored in any order with violet or an intermediate color between them, and by rotating or sliding the dimming filter 9 having such a configuration according to the user's preference, the wavelength of light from the light source to the light emitting surface can be arbitrarily set. Can be controlled. In addition, in television applications, it is effective as a method that can perform the essential hue adjustment most easily. Further, the light control filter 9 used in the present invention can simultaneously serve as the light amount filter and the wavelength filter. For example, there are a method in which both functions of light quantity adjustment and color tone adjustment are provided on the same filter, and a method in which the second configuration example is divided into a plurality of filters and superimposed on each other and independently controlled. Is more suitable for more precise adjustment because more adjustments such as light quantity, color tone, and tone of color tone are possible. Light emitting panel B having the above-described advantageous effects of the present invention
Can be formed from any of the materials having excellent light-transmitting properties, for example, a glass material, but from the viewpoint of ease of molding and light-transmitting properties, acrylic resin, acrylonitrile-styrene copolymer resin, cellulose acetobutyrate resin It is preferably formed from a light-transmitting plastic material such as cellulose propionate resin, polymethylpentene resin, polycarbonate resin, polystyrene resin, polyester resin, or a composite material or copolymer thereof. Further, a reaction-solidified epoxy resin, acrylic resin, methacrylic resin, 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 4 of the light emitting panel B thus obtained,
8, a light-reflecting metal such as nickel, aluminum, silver, or gold is deposited and sputtered on portions other than the light exit surface 3 and the light guide surface 1 of the light guide portion 7 as shown in FIGS. , Plating, silver mirror reaction, or the like, or by applying a reflective metal-containing paint, or laminating a light-reflective material such as an aluminum sheet.
It is effective to prevent the leakage from outside the panel B, including the effect of reflecting some of the leakage 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, a light diffusion layer 10 is formed on the light emitting surface 3 so that the viewing angle of the liquid crystal display 5 can be further increased in conjunction with the expansion of the viewing angle due to the numerous lenticulars and fly-eye shapes of the light emitting surface 3. can do. Such a light diffusion layer,
If the light diffusing property is too large, the illuminance on the light emitting surface is reduced, which is not preferable. The light diffusion layer 10 may be roughened by, for example, sandpaper polishing, sandblasting, horning, buffing, hairline processing, embossing, pressing, or the like, during or after forming the light-emitting panel. A transparent resin layer containing a light-diffusing material such as a white pigment such as titanium oxide, zinc oxide, barium sulfate, and magnesium oxide or a glass bead having a specific diameter,
By forming by a coating method such as dipping, roll coating, blade coating, spray coating, or by bonding 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 uniform. And the viewing angle can be widened. Such a light diffusing layer is prepared by separately preparing a ground glass plate, a light diffusing glass plate, a light diffusing plastic sheet, etc., and integrating them at the same time during molding or between the liquid crystal display 5 and the light emitting surface 3 during use. May be placed on or bonded together. 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. As described above, in the light emitting panel B of the preferred embodiment of the present invention, the light emitting surface 3 and the light guide portion 7 form a concave portion as shown in FIGS. 2 and 3, and the liquid crystal display 5 is placed in this concave portion. By illuminating the back of the liquid crystal display 5, the liquid crystal display 5 can be clearly seen regardless of the environment. 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 preferred embodiments of the present invention, the surface light source of the present invention is not limited to the illustrated shape as long as the light emitting surface has a configuration having a large number of lenticulars or fly eyes. Instead, any shape may be used. For example, the shape of each lens surface may be a hemispherical shape, an elliptical surface shape, a shape in which the top of a somewhat protruding rectangular body is a hemispherical shape, and the like, and further, the light guide portion 7 (light source A) of the light emitting panel B. Is not limited to the two places shown in the figure, and is 4
The shape of the light emitting panel B is not limited to a rectangle, but may be any shape such as a disk, an ellipsoid, a polygon, a rectangle having a rounded corner, and the shape of the light source is also a bar. The shape is not limited to the fluorescent lamp A, and may be an arbitrary shape such as an annular shape according to the shape of the light emitting panel B. (Operation / Effect) Since the light emitting surface of the surface light source of the present invention as described above has a large number of lenticulars or fly-eye shapes, the light emitted from the light emitting surface is not perpendicular to the light emitting panel, but is outside. , The viewing angle of the liquid crystal display mounted on the light emitting surface can be increased.
That is, the diffusion angle of light in the case of the surface light source of the present invention, particularly the diffusion angle to the left and right, is very wide, and when the illuminance at the center is 1, the angle at which the illuminance is attenuated by 10% is ± 70 from the center.
゜ ~ ± 80 ゜. Further, from such a wide viewing angle, the illuminance on the light emitting surface is very uniform, and the illuminance unevenness in the length direction of the fluorescent lamp as the light source is very small.
Furthermore, since sufficient light diffusion is possible by the above configuration, the amount of light diffusing agent used for forming the light diffusing layer on the light exit surface or the degree of light diffusing treatment can be reduced, and light attenuation is reduced, High light output efficiency can be obtained. That is, the illuminance of the light emitting surface in the case of the conventionally known surface light source as shown in FIG. 5 is only about 10% of that of the fluorescent light source, but the illuminance of the surface light source of the present invention is 30 to 70% of the light source. Reached. Further, in a preferred embodiment of the present invention, in addition to the effect of expanding the viewing angle due to the above-mentioned lenticulars shape or fly-eye shape, light from the light source is not incident parallel to the light guide, but is projected on the light exit surface. Most of the incident light can be directed at an angle with respect to the light exit surface because it is incident as reflected light with directivity, and the light from the light source is efficiently guided to the light exit surface. Be able to
The viewing angle of the liquid crystal display can be further expanded. In another 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. At the same time, the viewing angle of the liquid crystal display can be further expanded. For the same reason, the light guide section is made thicker than the diameter of the fluorescent lamp, and more than half of the fluorescent lamp is fitted therein, and this light guide section is connected to the light guide section. Since the light can be made thinner than the diameter of the lamp, most of the light emitted from the fluorescent lamp can be collected and introduced into the light guide. Therefore, even if the light guide is thinner than the diameter of the fluorescent lamp,
The light source light utilization efficiency can be significantly increased. Also, 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 exit surface can be made more uniform, and the viewing angle of the liquid crystal display can be further increased. Furthermore, in a preferred embodiment of the present invention, by providing a dimming filter around the light source, the user can easily and arbitrarily control the light amount and / or wavelength of the light reaching the light-emitting surface. A display such as a liquid crystal display can be used with an adequate amount of light (bright and dark) and / or an optimal wavelength of light (hue) for each user. (Example) Example 1 Using a polymethyl methacrylate resin (Parapet HR, manufactured by Kyowa Gas Chemical Co., Ltd.), a shape as shown in FIGS. 2 and 4 and a size of 200 mm × 120 mm, a light guide part thickness of 10 mm, lenticulars Shape pitch width 1.2mm, light guide part thickness 25mm
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. The light emitting surface was slightly roughened by a sand blast method. 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 excellent viewing angle, contrast, and illuminance, and exhibited a high display function that was uniform throughout. Example 2 A tubular body was formed from the acrylic resin of Example 1 above, with one end provided with a rotatable support, black dots were printed on the surface of the tubular body, and the number of dots was continuously changed. A vinyl sheet was stuck and two light control filters were prepared. A 15 W fluorescent lamp is mounted in each of them, fitted into the concave portion of the light guide portion of the light emitting panel of Example 1, the upper surface is sealed with an aluminum sheet, and the dimming filter can be freely rotated from the outside. Thus, the surface light source of the present invention was obtained. When a liquid crystal display was mounted on the light-emitting surface of this surface light source and the surface light source was turned on, the liquid crystal display was of a light emitting type, and exhibited a high viewing angle, excellent contrast, and a uniform high display function as a whole. Also, by gradually rotating the light control filter, the brightness of the liquid crystal display changes,
Dimming of the display surface was possible according to individual differences and external light. Example 3 In place of the dot print sheet in Example 2, a sheet in which seven colors of a rainbow having high transparency are continuously arranged vertically with a width equal to the peripheral length of the fluorescent lamp is used. In the same manner as in Example 2, a surface light source of the present invention was obtained. When this surface light source was used in the same manner as in Example 1, the hue of light on the display surface could be changed 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 a liquid crystal display.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 schematically show cross sections of an example of a surface light source of the present invention, FIG. 4 is a plan view of FIG. 2, and FIG. FIG. 2 is a diagram schematically showing a cross section of a conventional surface light source. A; light source B; light output panel 1; light guide surface 2; light guide portion 3; light output surface 4; light reflection layer 5; display 6; light source light 7; light guide portion 8; light reflection layer 9; light control filter 10; Light diffusion layer 11; lenticular lens shape

Claims (1)

(57) [Claims] A light source and a light emitting panel, wherein the light emitting panel is
A light guide surface, a light guide portion, a light reflection layer, and a light exit surface, wherein the light exit surface has a number of convex curved shapes, and the light reflection layer is provided to face the light exit surface. Surface light source. 2. 2. The surface light source according to claim 1, wherein the pitch width of the convex curved surface shape is in the range of 0.01 to 10 mm. 3. The surface light source according to claim 1, wherein the pitch of the convex curved surface shape corresponds to the pixel pitch of the display. 4. A light guide portion for accommodating a light source is formed at an end of the light emitting panel, and the light guide portion has a shape in which light incident from the light source is guided to the light guide portion as reflected light having an angle on the light emitting surface. The surface light source according to claim (1). 5. 9. The light emitting panel according to claim 1, wherein the light emitting panel is formed of a single light transmitting plate, and a center of the light guide provided at at least one end of the light transmitting plate is formed above a center of the light guide. The surface light source according to the item (2). 6. 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. 7. The surface light source according to claim (1), wherein the light emitting surface has a light diffusing property. 8. 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. 9. The surface light source according to claim (1), wherein the light emitting panel is integrally formed from a translucent resin. 10. The surface light source according to claim 1, wherein a dimming filter is provided around or part of the light source.