JPS62278503A - Plane light source - Google Patents

Abstract

PURPOSE:To increase the angle of a visual field, to reduce layer thickness and weight, and to control the quantity of light and its wavelength according to the environment by guiding light from a light source to a light projection surface efficiently through the constitution of the light source and a light projection panel consisting of a light guide surface, a light guide part, a light reflecting layer, and the convex light projection surface. CONSTITUTION:The light source A and the light projection panel which consists of the light guide surface 1, light guide part 2, light reflecting layer 8, and light projection surface 3 are provided, and the light from the light source A is incident slantingly on the convex light projection surface 3 through the guide part 2 to increase the angle of the visual field of a liquid crystal display 5. An optical filter is provided at the periphery of the light source A to control the quantity of light and hue. Thus, the light from the light source is guided to the light projection surface efficiently to obtain the plane light source which is sized large and thin on the whole.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a surface light source, and more specifically, to a light source for various displays, particularly a light source installed on the back side of a liquid crystal display cell as a back light source. This invention relates to a surface light source with significantly improved light output efficiency and viewing angle of a liquid crystal display.

(Prior art) In recent years, with the rapid development of the information society, terminals that transfer various information to humans have become popular! U devices are widely used. Most of these terminal displays are so-called CR
Although these CRTs have many advantages such as excellent color display functions, image adjustment functions, and fewer signal cables, they require a high-voltage power supply and a display tube made of thick glass. Therefore, various types of flat displays have been proposed, mainly for wall-mounted, portable, and portable applications. It 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 and contrast display quality are poor due to insufficient brightness, especially for devices around 10 to 12 inches. Make the size larger than 80
When used for large-capacity display of about 20 to 25 lines of characters, a problem arises 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 conditions, and there is a drawback that the 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 provided on the side surface of a translucent panel such as an acrylic plate, and light is emitted from one side of the panel. Although this method is promising, it does not solve the inherent narrow viewing angle problem of liquid crystal displays. Known methods for solving this problem include roughening the light emitting surface of the light emitting panel and using a light diffusing agent such as alumina or glass beads to diffuse the emitted light. However, with this method, the light diffusing properties are insufficient, and the light diffusing agent also has some degree of light absorption, so the larger the display becomes, the less effective it becomes, and in fact, the brightness is insufficient in the center of the display. A problem arises.

Furthermore, since this method uses fluorescent lamps as the light source,
There is a layer between the thickness of the light emitting panel. In other words, installing the fluorescent lamp on the side of the panel is the thinnest condition, but if the panel is made thinner than the diameter of the fluorescent lamp, there is a problem that the light guiding efficiency will decrease significantly, and most of the introduced light will be placed on the light output surface. Since the light travels in a straight line parallel to , there is a problem in that the light output efficiency from the light output surface is low. Furthermore, as the panel becomes larger, there is a problem that a difference occurs in the illuminance between the vicinity of the light source and the central portion 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. unable to respond. In addition, considering not only the amount of light, that is, brightness, but also white balance, color rendering, and eye strain of the user, it is also desirable to adjust the wavelength from the light emitting surface to obtain light of an appropriate hue. In this case, only white light is emitted, which has the disadvantage that electrical regulation is not possible.

Therefore, the main object of the present invention is to be large enough to replace a CRT, to be able to expand the viewing angle, which is a disadvantage of the wood quality of liquid crystal displays, and to make the light emitting panel the same size as a light source such as a fluorescent lamp. It is an object of the present invention to provide a surface light source that can be made thin regardless of the problem and 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,
The light emitting panel is a surface light source characterized in that the light emitting panel includes a light guiding surface, a light guiding portion, a light reflecting layer, and a light emitting surface, and the emitting surface has a convex curved shape.

(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. still,
In order to facilitate explanation, all figures are not scaled to the original size, but are drawn compressed in the length direction.

7jfJ1 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 preferred example of the surface light source of the present invention, and FIG. shows a top view of the light source;
FIG. 5 shows a cross-sectional view of a conventional surface light source.

As shown in Figure 5, a conventional surface light source using an acrylic plate or the like has a light guide section (light guide surface 1 ) is attached with a light source A such as a fluorescent lamp, and one component of the light from the light IIA is emitted almost perpendicularly from the light emitting surface 3 (arrow), so that the field of view of the liquid crystal display 5 installed above it is The angle cannot be improved, and if the light emitting surface 3 is made light diffusive with a light diffusing agent in order to improve this viewing angle, the brightness of the light emitting surface will decrease as the light diffusivity increases. Ta. Furthermore, considering the thickness of the light emitting panel, if the thickness of the light emitting panel B is made thinner than the diameter of the fluorescent lamp A, there is a drawback that the introduction efficiency of the light source light 6 decreases.

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. Furthermore, 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 was a problem that the light output efficiency from the light output surface 3 was low, and furthermore, the illuminance of the light output surface 3 near the light source A was high, and the illuminance decreased as the distance from the light source A increased, and the illuminance was non-uniform over the entire light output surface 3.

Furthermore, when a fluorescent lamp is used as the light source A, the light intensity of the fluorescent lamp is always uniform, so the light intensity of the light output surface 3 cannot be arbitrarily controlled, and the Unable to adapt to the usage environment. In addition, considering not only the amount of light, that is, brightness, but also white balance, color rendering, and eyelid fatigue of the user, it is also desirable to adjust the wavelength from the light emitting surface 3 to obtain light of an appropriate hue.
When the light source A is a fluorescent lamp, only white light is emitted, so there is a problem in that it is impossible to electrically adjust the wavelength of the light.

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 to 4,
By making the light emitting surface 3 not planar but convexly curved, the viewing angle of the liquid crystal display 5 disposed on the light emitting surface 3 can be expanded.

Furthermore, in the preferred embodiment shown in the second figure, the light guide section 7 is integrally formed at the end of the light output panel B, and the light guide section 7 is disposed, for example, shifted upward from the horizontal plane of the light output panel B. The overall thickness including the liquid crystal display 5 can be made thinner, and the light 6 from the light source A can be emitted by shaping the reflecting surface 8 below the light guide part 7 into an appropriate shape or giving it an appropriate angle. Instead of light parallel to surface 3,
The light can be sent to the light emitting surface 3 via the light guide section 2 as light directed at an angle relative to the light emitting surface 3, and the viewing angle of the liquid crystal display can be further expanded.

With the above configuration, the light (arrow) emitted from the light emitting surface 3 can be introduced even if the thickness of the light guide section 2 of the light emitting panel B is made thinner than the diameter of the fluorescent lamp A that is the light source. The light is reflected by the reflective surfaces 4 and 8 on the side facing the light emitting surface 3 (-order reflected light), and reaches the light emitting surface 3 directly, expanding the viewing angle of the liquid crystal display 5 and guiding the light source light 6. No reduction in light efficiency.

Furthermore, the example shown in the third figure is an example in which the light emitting surface 3 has a plurality of convex curved shapes, and when the light sources A are present on both sides of the panel, two light sources A are provided in accordance with the number (2) of the light sources A. For example, if four light beams A are provided on each side of the panel, it is also possible to divide the entire light emitting surface into four parts and add four convex curved shapes. With this configuration, even if the curvature of the convex curved surface shape is increased, there is no need to increase the thickness of the light emitting panel B accordingly.
Since the light emitting surface of the panel B is curved, the problem of the panel B becoming thick does not occur.

Furthermore, in another preferred embodiment of the invention, a light control filter 9 is provided around the light source A. The light control filter 9 can freely change the intensity and hue of the light from the light source A, and functions as a light amount filter and/or a wavelength filter.

First of all, if the light control filter 9 is a light amount filter, any structure may be used as the light amount filter as long as the amount of light emitted from the fluorescent lamp A can be adjusted.

Some preferred examples are as follows.

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

In this embodiment, the above-mentioned layer becomes a light intensity filter, 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. Such a light amount control layer is made by preparing an appropriate ink or paint and applying it to a fluorescent lamp A.
Print around the area, or apply using methods such as rolling, spraying, electrostatic painting, baking, or inkjet methods.
Methods such as vapor deposition, CVD, and sputtering, methods such as forming a dyed layer in advance and then dyeing it directly on the light source, or forming it on another transparent substrate in advance and bonding, etc. It may be formed by any method. Of course, such a light intensity filter is not formed uniformly on the tube wall of the fluorescent lamp A, but is formed in a line, stripe, or dot shape with an appropriate density difference or concentration difference, or it is formed with a transparent filter. Light shielding material layers having different Aa degrees are formed stepwise or continuously. By forming the light amount filter 9 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 9 is provided around it.

The principle of this example is exactly the same as the case (1) above, and for example, a tubular filter 9 made of transparent glass or plastic is formed, and on its surface, as in (1) above,
A method of forming a light-absorbing layer or a light-reflecting layer having a density difference or concentration difference may be used. Furthermore, after the tubular body is provided, a film or the like having the above-mentioned light amount adjustment function may be attached to the surface thereof. It is also possible to make a flexible cylindrical sheet and feed it by rotating it on two axes.

By providing a light amount filter 9 having such a configuration and rotating this filter 9 using appropriate means (not shown) such as a gear or a belt, the amount of light reaching the light output surface can be arbitrarily controlled. Although the above description has been made using a tubular filter as an example 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 can be achieved by coloring the light absorption layer in the above embodiments (1) and (2) in a color that absorbs light of a specific wavelength. can. In other words, the ``A light filter 9 is yellow, orange, let, blue, green,
The wavelength of the light from the light source to the light emitting surface can be adjusted to any desired wavelength by rotating or sliding the dimmer filter 9 with such a configuration according to the user's preference. can be 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 9 used in the present invention can serve as the above-mentioned light amount filter and wavelength filter at the same time. For example, in the second configuration example, there is a method of providing both light amount adjustment and color tone adjustment functions on the same filter.
There is a method in which multiple filters are stacked one on top of the other and controlled independently.The latter method allows many adjustments such as the amount of light, color tone, and shade of color, and is suitable for more precise adjustment.

The light emitting panel B that exhibits the effects of the present invention as described above is:
It can be formed from any translucent material, such as glass material, but in terms 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 used.

Light reflecting layer 4.8 of light emitting panel B obtained in this way
As shown in FIGS. 2 and 3, a light-reflecting metal such as nickel, aluminum, aluminum, silver, or gold is vapor-deposited on the light-emitting surface 3 and other parts of the light-guiding part 7 except for the light-guiding surface 1. It is formed by sputtering, plating, silver mirror reaction, etc., or it is formed by applying reflective metal-containing paint, or by laminating light-reflective materials such as aluminum sheets, and the light source light 6
It is effective to prevent light from leaking out of panel B, including the effect of reflecting some of the leaked light back inside. 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.

Furthermore, by forming a light diffusion layer 10 on the light emitting surface 3, the viewing angle of the liquid crystal display 5 can be further expanded in addition to expanding the viewing angle due to the convex curved shape of the light emitting surface 3.

Such a light diffusing layer is not preferable because if the light diffusing property is increased too much, the illuminance of the light emitting surface will decrease. The light-diffusing layer 10 can be processed, for example, by sand vapor polishing, sandblasting, honing, puff polishing, hairline processing, embossing, etc., on the light-emitting surface during or after molding the light-emitting panel.
A transparent resin layer whose surface has been roughened by pressing, etc., or which contains a light-diffusing material such as a white pigment such as silica, alumina, titanium oxide, zinc oxide, barium sulfate, or magnesium oxide, or a light-diffusing material such as glass beads having a specific diameter, is immersed. Formed by coating methods such as roll coating, blade coating, and spray coating,
Alternatively, by adhering these layers, the light reaching the light output surface 3 can be diffusely reflected or diffused, the illuminance from the light output surface 3 can be made uniform, and the viewing angle can be widened.

In addition, such a light diffusing layer can be prepared by separately preparing a ground glass plate, a light diffusing glass plate, a light diffusing plastic sheet, etc.
They may be integrated at the same time during molding, or may be placed or bonded between the liquid crystal display 5 and the light emitting surface 3 during use. Further, it is also advantageous in terms of efficiency improvement and thermal design to arrange a light-reflecting condensing mirror or a heat sink on the opposite side of the light guide portion of the light source.

The light emitting panel B of the preferred example of the present invention as described above has a second
~ 3 As shown in the figure, the light emitting surface 3 and the light guiding part 7 form a recess, and by placing the liquid crystal display 5 in this recess, the back surface of the liquid crystal display 5 is illuminated, and the liquid crystal display 5 is controlled by the environment. can be clearly seen. 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 as long as the light emitting surface has a convex curved shape, for example, a spherical shape, a cylindrical surface shape, or any other arbitrary curved shape, the present invention can be applied. The light source is not limited to the illustrated shape, and may have any shape. For example, the light guide portion 8 (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. It may be of any shape, such as a disc, an elliptical plate, a polygon, or a rectangle with rounded corners.
Therefore, the shape of the light source is not limited to the rod-shaped fluorescent lamp A, but may be any shape such as an annular shape depending on the shape of the light output panel B.

(Function/Effect) The surface light source of the present invention as described above has a light emitting surface having a convex curved shape, so that the light emitted from the light emitting surface is not perpendicular to the light emitting panel but is diffused outward. Therefore, the viewing angle of the liquid crystal display placed on the light emitting surface can be expanded.Furthermore, in a preferred embodiment of the present invention, in addition to the effect of expanding the viewing angle due to the above-mentioned convex curved shape, the light from the light source can be expanded. Instead of being incident parallel to the light guide,
Since it enters the light emitting surface as reflected light with directionality, most of the incident light can be oriented at an angle with respect to the light emitting surface, and the light from the light source can be efficiently emitted. The viewing angle of the liquid crystal display can be further expanded.

Further, in another 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. At the same time, the viewing angle of the liquid crystal display can be further expanded.

In addition, for the same reason, by making the light guide part thicker than the diameter of the fluorescent lamp, fitting more than half of the fluorescent lamp into it, and connecting this light guide part with the light guide part, the light guide part becomes fluorescent. Since it 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 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 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 more uniform, and the viewing angle of the liquid crystal display can be further expanded.

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 Fig. 2 and Fig. 4, the size was 200 ml, LIIX120 rhyme, the center thickness of the light guide part was 75111111, and the peripheral thickness was 9 mm. A light emitting panel having a light guide portion having a thickness of 25 mm 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 acrylic resin to prepare a 2 mm thick sheet, which was bonded to the light emitting surface. Two 15W fluorescent lamps were used as the light source.
The light guide was fitted into a recess 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 rotating handle provided at one end was formed from the acrylic resin of Example 1, and black dots were printed on the surface of the polychloride resin, the number of dots changing continuously. I pasted vinyl sheets together and prepared two wooden dimmer filters. A 15W fluorescent lamp is attached to each of these, and these are fitted into the recesses of the light guide part of the light output panel of Example 1, and the upper surface is sealed with an aluminum sheet, so that the above-mentioned dimmer filter can be freely rotated from the outside. In this way, a surface light source of the present invention was obtained.

When eight liquid crystal displays were 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 and exhibited excellent viewing angles and contrast, and a high display function that was uniform throughout. 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 Instead of the dot-printed sheet in Example 2, a sheet with a width equal to the circumferential length of the fluorescent lamp and having seven highly transparent rainbow colors arranged vertically and continuously was used, and the other parts were the same as in Example 2. A surface light source of the present invention was obtained in the same manner as in Example 2. 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 color sums.

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 the drawing]

1 to 3 are diagrams schematically showing a cross section of an example of the surface light source of the present invention, FIG. 4 corresponds to the plan view of FIG. 2, and FIG. FIG. 3 is a diagram schematically showing a cross section. A: Light source B: Light output panel 1: Light guide surface 2: Light guide section 3: Light output surface 4: Light reflection layer 5: Display 6: Light source light 7: Light guide section 8: Light reflection layer 9: Light control filter 10: Light Diffusing Layer Agent Patent Attorney Announcement 1) yI Hiro sr'a*Figure 1Figure 3

Claims (9)

[Claims] (1) Consisting of a light source and a light output panel, the light output panel consisting of a light guide surface, a light guide section, a light reflection layer, and a light output surface,
A surface light source characterized in that the light emitting surface has a convex curved shape. (2) The surface light source according to claim (1), wherein the light emitting surface has a number of convex curved surfaces corresponding to the number of light sources. (3) A light guide section that houses the light source is formed at the end of the light output panel, and the light guide section has a shape in which the light incident from the light source is guided to the light guide section as reflected light having an angle to the light output surface. A surface light source according to claim (1). (4) The light emitting panel is composed 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 of the light emitting panel excluding the light emitting surface and the light guiding surface is
The surface light source according to claim (1), which 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 integrally molded from a translucent resin. (9) The surface light source according to claim (1), wherein a dimmer filter is attached to the periphery or a part of the light source.