JPH06308490A - Back light - Google Patents

Abstract

PURPOSE:To deal with the miniaturization, to reduce the number of parts, thereby facilitating assembling of the parts, to make the brightness uniform and to have the displaying mechanism of the lighting and turning off of a light by making a light transmission plate have a projection part, making a container surface have a recessed part and optically conducting a part of the recessed part to the outside of the container. CONSTITUTION:In an arbitrary part on the surface other than the surface of the light incident end part of the light transmission plate 1 arranged close to a linear light source 4, a pair of the recessed and projection parts 12, 13 which is constituted of the light transmission plate 1 and the container 7 is provided and a part of at least one recessed part 13 thereamong is optically conducted to the outside of the container. That is, an optically conducting part 14 between a part of the recessed part 13 and the outside of the container is provided. The optical conducting in this case means a window (hole) through which the inside light beams are recognized from the outside of the container 7 and the window may be either opened for conducting or closed with light transmitting substance, but the closed state is rather preferable from the viewpoint of preventing foreign matters from entering. Thus, the light transmission plate 1 is fixed to the container 7 without interposing an optically heterogeneous matter into the light transmission plate 1 and a pressing element between the light transmission plate 1 and the light source 4 is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for a panel which illuminates a transmissive or semi-transmissive panel from the back side.

[0002]

2. Description of the Related Art Recently, a liquid crystal display device having a thin and easy-to-read backlight mechanism has been used as a display device for a laptop or notebook type word processor or computer. . In such a backlight, as shown in FIG. 1, at one end of a light-transmitting light guide plate,
An edge light system that is provided with a linear light source such as a fluorescent tube is often used. In the case of this edge light method, as shown in FIG. 2, one wide surface of the light guide plate is partially covered with a light diffusing substance, and almost the entire surface is covered with a light diffusing reflector or film. There were many things that were done.

In terms of handling, the above-mentioned backlight is often fixed to the container in order to prevent the light guide plate from unnecessarily moving inside the backlight.
Conventionally, as a fixing method, there is a method of fixing to a backlight or a container of a display device using a screw or the like as shown in FIG. According to this method, an optical foreign substance such as a screw that attenuates light is present in the light guide plate, so that not only the utilization efficiency of the light incident on the light guide plate is lowered, but also the optical foreign substance of the effective light emitting portion is used. There is a problem in that a low-luminance portion is generated around the area and the luminance uniformity in the effective light emitting portion is impaired. Further, since screws and the like are used, there has been a problem that the number of parts and the number of assembling steps increase accordingly.

As another fixing method for the light guide plate, there is a method for fixing the light guide plate to the container by forming a pressing element of the light guide plate on the container of the backlight or the display device itself as shown in FIG. In this method, since the pressing element (the light transmittance is usually less than 100%) is interposed between the light guide plate and the light source, the light incident efficiency from the light source to the light guide plate is reduced.
There has been a problem that a low-luminance portion is generated around the pressing element of the effective light-emitting portion and the luminance uniformity in the effective light-emitting portion is impaired. Further, since the pressing element is interposed between the light guide plate and the light source, there is a problem that the backlight volume is increased by the amount of the pressing element. In order to meet the demand for cost reduction (reduction of the number of parts, reduction of assembly man-hours, etc.), its improvement has been desired.

The term "effective light emitting portion" as used herein means a portion that is actually used as planar illumination within the light emitting surface of the light guide plate. Therefore, in the case of a backlight used in a liquid crystal display device such as a word processor or a personal computer, it substantially corresponds to the display area of the display device.

Further, conventionally, the function of recognizing whether the backlight is lit or not lit by a portion other than the display portion of a word processor, a personal computer or the like using the backlight is provided with an LED or the like. However, such a method inevitably causes an increase in the number of constituent parts and a problem in downsizing the outer shape of the display device, is simple and does not increase the number of parts, and the number of steps for assembling the backlight is also large. A backlight configuration that does not increase is desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight corresponding to miniaturization, which has a small number of parts and is easy to assemble, and has a uniform luminance in the effective light emitting portion, and a display of lighting and non-lighting. It is to provide a backlight with a mechanism.

[0008]

As a result of various studies on the shape of the light guide plate of the backlight and the shape of its container, the present inventors have completed a backlight that meets the above-mentioned object.

That is, according to the present invention, a plate made of a translucent material having a linear light source close to at least one side surface end portion and having a light diffusing function for allowing light incident from the side surface end portion to be emitted from one wide surface. In a backlight for a panel composed of a light guide plate and a container enclosing the light guide plate, a convex portion is provided at an arbitrary position on a surface other than the light incident end surface of the light guide plate, and a corresponding container surface. The present invention relates to a backlight for a panel in which at least a pair of concave and convex portions are formed with a concave portion at a position, and at least one of the concave portions has a shape in which the concave portion is optically connected to the outside of the container.

Next, the present invention will be described in more detail with reference to the drawings. The present invention basically comprises the edge light type light emitting section shown in FIGS. 1 and 2, and a container for holding and protecting the same. In the figure, reference numeral 1 denotes a plate-shaped light guide plate, which is made of a material such as quartz, glass, a light-transmitting natural or synthetic resin, for example, an acrylic resin, which efficiently transmits light.

Reference numeral 4 is a linear light source, and in a preferred embodiment,
Arrange the linear light source so that the central axis of the linear light source is substantially parallel to the end face of the light guide plate so that light is incident on the end face of the light guide plate. It is arranged in a state of being covered with the reflection plate or the film 5. The linear light source 4 includes a fluorescent tube, a tungsten incandescent tube, an optical rod, an LED array, and the like, but a fluorescent tube is preferable, and in terms of uniformity of luminance distribution of an effective light emitting area and power saving, It is preferable that the length of the uniform light emitting portion excluding the electrode portion is substantially equal to the length of the end portion of the adjacent light guide plate.

In order to cause a light beam incident from the side end portion of the light guide plate 1 to be emitted from one wide surface of the light guide plate, it is usually to give a light diffusing function to the other wide surface of the light guide plate. The application method is a light-scattering substance such as SiO ₂ or BaS.
A method in which a paint containing O ₄ , TiO _2, etc., a printing ink is printed in dots on the surface of the light guide plate by a method such as screen printing, or the surface of the light guide plate is roughened or small. There are a method of forming a hole, a method of providing a small protrusion, and a method of providing a state in which a portion having a refractive index different from that of the material of the light guide plate is distributed in the light guide plate itself.

In the figure, reference numeral 2 denotes a light diffusing plate which scatters the light emitted from the surface of the light guide plate and allows the light to pass therethrough, and one or more sheets are used as necessary. The light guide plate 3 and the film 3 are arranged so as to cover almost the entire surface of the light guide plate on the side opposite to the light exit surface of the light guide plate.

The light emitting portion of the present invention is basically constructed as described above, but the light emitting portion is enclosed in a container with the light emitting surface opened. The present invention, in any location on the surface other than the light incident end surface of the light guide plate close to the linear light source,
The light guide plate and the container have a pair of concavo-convex portions, and at least one of the concave portions is partly electrically connected to the outside of the container. Next, the configuration will be described. FIG. 5 shows a part of one embodiment thereof.

Reference numeral 7 in FIG. 5 is a container. 12, 1 in the figure
Reference numeral 3 denotes a concavo-convex portion that forms a pair with the light guide plate and the container surface, and it is sufficient if at least a pair of concavo-convex portions is provided. FIG. 5 shows the convex portion (12) on the light guide plate side and the concave portion (13) on the container side. Reference numeral 14 is an optical conduction portion between a part of the concave portion (13) and the outside of the container. The term "optical conduction" as used herein means a window (hole) through which light inside can be recognized from the outside of the container, and it may be open conduction or closed with a light transmitting substance. The closed state described above is a preferred embodiment in order to prevent foreign matter from entering from the outside.

The method of forming the convex portion on the light guide plate is not particularly limited, but generally, there is a method of integrally forming it at the time of injection molding of the light guide plate. The shape of the convex portion is not particularly limited as long as it has a function of fixing the light guide plate, but may be a prismatic shape such as a columnar shape, a conical shape, or a quadrangular prism shape, or a pyramidal shape such as a quadrangular pyramid shape. Also, the size of the convex portion is not particularly limited as long as it has strength to fix the light guide plate, but it is preferable to be small for downsizing the backlight, and the height is 0.5 mm.
Generally, the width is about 5 mm and the width is about 0.5 mm to 5 mm. In addition, when the projection is provided with a light emitting function and is also used as a light emitting function to the outside of the backlight container, the height may be set to 5 mm or more depending on the structure of the display device used. There is.

The present invention is a mechanism for recognizing the light of the above-mentioned convex portion of the light guide plate from the outside of the backlight container, but more preferably, the convex portion is provided with a light diffusion means.
As the light diffusing means, a light scattering substance such as SiO 2 is used.
₂ , paint such as BaSO ₄ , TiO ₂ or the like, or printing ink on the surface of the convex portion or the surface opposite to the light guide plate corresponding to the convex portion by a method such as printing, or The surface or the opposite surface of the light guide plate corresponding to the convex portion is roughened, or a method in which substances having different refractive indexes are distributed in the light guide plate corresponding to the convex portion itself or the convex portion is used. . In addition, a light diffusing means is provided on the surface opposite to the light guide plate corresponding to the convex portion,
Further, if the convex portion is formed in a lens shape, a prism shape, or the like, the light beam diffused and reflected by the surface on the opposite side of the light guide plate corresponding to the convex portion is condensed by the lens action of the convex portion in any direction. Dispersed and preferred.

Reference numeral 7 in FIG. 5 is a container for enclosing the light emitting portion of the present invention, and the method of forming this recess is not particularly limited.
When the container is made of a plastic material such as ABS, ACS, PC, etc., it is common to mold the container as a unit during injection molding. Further, when the case is made of a metal material such as iron, aluminum or SUS, it is general to use the same forming method at the time of molding. The shape and size of the concave portion may be any shape as long as the corresponding convex portion can be fixed, and in any case, the shape and size are appropriately determined according to the respective shapes.

In the present invention, it is essential that a part of the above-mentioned concave portion is electrically connected to the outside of the container, but its size is not particularly limited, and the lighting state of the backlight is visually recognized. If it is big enough,

The position of the concave-convex portion which characterizes the present invention is at a position other than the light incident surface of the light guide plate which is close to the linear light source, preferably at a position other than the effective light emitting portion of the light guide plate, that is, at the relatively end of the light guide plate. It is a department. By setting it like this,
It is possible to make the brightness in the effective light emitting portion more uniform.

[0021]

[Effects of the Invention] By adopting the structure of the present invention,
(1) The light guide plate can be fixed to the container without causing an optical foreign substance such as a screw to exist in the light guide plate, so that the light utilization efficiency does not decrease, and the brightness in the effective light emitting portion is uniform. In addition, the number of parts and the number of assembling steps for housing the light emitting portion in the container can be reduced, and (2) there is no pressing element between the light guide plate and the light source, thus reducing the light incident efficiency. No, (3) it is a small-sized and relatively low-cost backlight, and (4) it is possible to check the lighting state for a short time even on a portion other than the display surface of the display device, which is preferable for storage. .

[0022]

COMPARATIVE EXAMPLES AND EXAMPLES Next, the present invention will be described in more detail with reference to Comparative Examples and Examples. A rectangular acrylic plate having a thickness of 4 mm (205 mm × 160 mm, Delaglass A manufactured by Asahi Kasei Corporation) as shown in FIG. (Normal tube manufactured by Nakai Kogyo Co., Ltd.), and the outer circumference of the tube is covered with Ag film (Nakai Kogyo Co., Ltd.) as shown in FIG.
The light emitted from a slit having a width of 4 mm facing the end of the light guide plate of the Ag film was arranged so as to enter the light guide plate from the end of the light guide plate.

On the other hand, an ink containing a light-scattering substance (titania) was screen-printed on a surface of the light guide plate with a circular dot pattern at a pitch of 1 mm. Created. The light diffusing substance coverage is 20% at the minimum point (near the linear light source), 95% at the maximum point (center of the light guide plate), and in the middle, these ratios are sequentially increased from the point with the lowest coverage rate. It was drawn so that it would be the value.

The effective light emitting area of the light guide plate is 204 mm ×
Printing on the surface of the light guide plate was performed by centering the light guide plate so that the length was 152 mm. The end of the Ag film on the light emitting surface side of the light guide plate was adhered to the surface of the light emitting surface of the light guide plate with a double-sided tape.

White light diffuse reflector made of polyester having a thickness of 0.13 mm (Melinex 329 manufactured by ICI)
Was placed so as to cover the entire surface of the light guide plate coated with the light scattering material. The light diffusion plate (8B36 made by GE) made of polycarbonate with a thickness of 0.18 mm is arranged so that the rough surface side is the opposite side to the light guide plate side and covers almost the entire light exit surface of the light guide plate. Placed in. In the cold cathode tube, 3 from the inverter
Constant current by applying an alternating voltage of 0 KHz (tube current 5 mA)
The brightness of the surface when it is driven by a brightness meter (Topcon BM-
8).

First, as shown in FIG. 3, the brightness was measured while the light guide plate was fixed with screws (2 mmΦ × 6 mm, made of iron) so as to be integrated with the plastic case. At this time, the average luminance of 99 points (evenly divided) within the effective light emitting area was 1300 cd / m ² . Further, the lowest luminance of the low luminance portion (9 in FIG. 3) near the screw generated in the effective light emitting portion of the light guide plate was 700 cd / m ² (Comparative Example 1).

Next, as shown in FIG. 4, the light guide plate is replaced by screws and pressing elements (2 mm × 2 mm, made of ABS and integrated with the backlight plastic case 11 in FIG. 4). A backlight was constructed in the same manner as in Comparative Example 1 except that it was pressed with, and the average luminance measured by the same measuring machine was 1.
It was 300 cd / m ² . In addition, the minimum luminance of the low luminance portion near the pressing element generated in the effective light emitting portion of the light guide plate is 75.
It was 0 cd / m ² . Further, the outer shape of the backlight is increased by the amount corresponding to the pressing element (Comparative Example 2).

Next, as shown in FIG. 5, on the surface of the light guide plate on the side of the reflection plate (the side opposite to the light emitting surface), four small projections are formed at the portion where the effective light emitting portion (8 in FIG. 5) is deviated. A small portion that mechanically joins a light guide plate provided with a portion (a cylindrical shape having a height of 2 mm and a diameter of 2 mmΦ) to a position corresponding to these small convex portions of the plastic container (7 in FIG. 5) of the backlight. A small convex portion of the light guide plate and a small concave portion hole of the container were united in a container having a concave portion (a cylindrical hole having a diameter of 2 mmΦ) and fixed to form a backlight. An opening communicating with the outside of the backlight container was provided at the bottom of one small recess, and the surface of the small projection corresponding to the small recess was roughened. The other configurations were the same as those in Comparative Example 1, and the luminance was measured in the same manner. The average brightness was 1300 cd / m ² , and no low brightness part was observed near the small convex part in the effective light emitting part of the light guide plate. In addition, light of a small convex portion was confirmed from the outside of the backlight container (Example 1).

Next, instead of making the surface of the small convex portion corresponding to the small concave portion provided with the opening in Example 1 a rough surface, a light scattering material is formed on the surface opposite to the light guide plate corresponding to that portion. A backlight was constructed in the same manner as in Example 1 except that the ink containing (titania) was printed and the opening of the small recess was closed with a red transparent plate. The average brightness was 1300 cd / m ^2. Then, the bright light of the small convex portion was observed as red bright light from the outside of the backlight container (Example 2).

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional backlight.

FIG. 2 is a sectional view of a conventional backlight.

FIG. 3 is a schematic view of an embodiment in which a light guide plate is fixed with a conventional screw.

FIG. 4 is a schematic diagram of an embodiment in which a light guide plate is fixed by a conventional pressing element.

FIG. 5 is a schematic diagram of an embodiment of the present invention.

[Explanation of symbols]

 1: Light guide plate 2: Light diffusion plate 3: Light reflection plate or the same film 4: Linear light source 5: Light reflection plate or the same film 6: Light scattering substance 7: Backlight container 8: Effective light emitting part 9: Low brightness Part 10: Screw 11: Holding element 12: Convex part 13: Concave part corresponding to the convex part 14: Opening part of the concave part

Claims (2)

[Claims] 1. A plate made of a translucent material having a linear light source close to at least one side surface end portion and having a light diffusing function for allowing light incident from the side surface end portion to be emitted from one wide surface of the light guide plate. In a backlight for a panel composed of a light guide plate and a container enclosing the light guide plate, a convex portion is provided at an arbitrary position on a surface other than the light incident end surface of the light guide plate, and a corresponding container surface. A backlight for a panel, which has a concave portion at least one portion to form at least a pair of concave and convex portions, and at least a portion of the concave portion is in a shape that is electrically connected to the outside of the container. 2. The backlight according to claim 1, wherein a light diffusing function is provided on a surface of a convex portion corresponding to a concave portion which is electrically connected to the outside of the container.