JP2005025972A - Surface lighting system and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a surface lighting system to obtain uniform surface illumination light by entering light emitted from a point light source such as a semiconductor light emitting element and the like into a light guide plate, and by uniforming unevenness of a quantity of light produced thereby. <P>SOLUTION: This surface lighting system is composed of a light source device 1 comprising a point-like light source 11 which at least one semiconductor emitting element emits and a light guide pipe 12 to linearly expand light emitted from the light source 11, a light entering end face 21 where the light source device 1 is adjacently provided, a prism array 23 provided side by side on the back perpendicularly to the light entering direction, and a light guide plate 2 having a light emitting surface 22 facing the prism array 23, and the surface lighting system is structured so that a reflecting sheet is provided adjacently to the back of the light guide plate 2, light scattering objects 3 are scattered in the guide plate 2, to illuminate an adjacently provided object to be illuminated from the light emitting surface 22 by diffusing light passing through the guide plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface illumination device that illuminates a display device such as a liquid crystal display device, and in particular, a configuration of a light guide plate that efficiently expands light from a light source in a planar shape, and a liquid crystal display device that is illuminated by the surface illumination device. About.
[0002]
[Prior art]
A flat display device commonly called a flat display has various display functions integrated on a pair of opposed flat substrates. A liquid crystal display device (LCD), a plasma display device (PDP), an electroluminescence display device (EL), and the like are well known depending on the display function, and are put into practical use according to each application.
[0003]
However, since only the liquid crystal display device is a passive display device that does not emit light by itself, some illumination is required for the liquid crystal display panel at the time of display. One of the features of a flat display is that it is thin, so in a liquid crystal display device, it is important how to illuminate while maintaining the thin shape.
Liquid crystal display devices have different configurations depending on how they are illuminated, that is, how the liquid crystal display panel is illuminated, and are roughly divided into two types: reflective liquid crystal display devices and transmissive liquid crystal display devices. .
[0004]
In the case of a reflective liquid crystal display device, at least external light serving as a light source for illumination passes through one transparent substrate, passes through a liquid crystal layer, is reflected by a reflective film provided on the other substrate, and again. Return through the liquid crystal layer. In the meantime, the light reciprocating through the liquid crystal layer is modulated by the liquid crystal layer, and a display formed by being transmitted or shielded is visually recognized.
This reflection type liquid crystal display device can be used in a bright place, but cannot be used in a dark place, when lighting depends only on external natural light. Therefore, recently, in order to visually recognize a liquid crystal display image using a surface illumination device, it has been devised so that it can be illuminated from the front (front) side of the liquid crystal display panel and can be viewed even in a dark place, and is called front light type illumination.
[0005]
On the other hand, a transmissive liquid crystal display device is widely used in a small screen mobile phone, a large screen personal computer, a liquid crystal TV, and the like, and a backlight type surface illumination device is used for illumination. Backlight-type illumination is configured to illuminate from the back (back) side of the liquid crystal display panel, and is formed by transmitting or blocking light reaching the surface from the back of the liquid crystal display panel through the liquid crystal layer. Visually check the display.
[0006]
However, in applications such as mobile phones, it can be visually recognized by external light illuminated from the front surface of the liquid crystal display panel, and the battery of the backlight surface illumination device is made to last longer. In other words, a transflective film is provided on the other substrate of the liquid crystal display panel, so that it is a reflective liquid crystal display device according to external light from the front surface, and a transmissive liquid crystal display according to illumination light from a backlight type surface illumination device. Visible as a device. Therefore, the liquid crystal display device having such a configuration 1 is called a transflective liquid crystal display device.
[0007]
A device that uniformly illuminates the entire surface of an object to be illuminated, such as a liquid crystal display panel, whether it is a front light type or a backlight type, is called a surface illumination device. In order not to impair the thin features of the object to be illuminated, various devices have been made to make the illumination light uniform while the surface illumination device is also made thin.
FIG. 7 is a perspective view schematically illustrating a configuration example of the light source device. In the light source device 1, for example, a semiconductor light emitting element such as a light emitting diode is used for the light source 11. However, the light emitted from the light source 11 such as a semiconductor light emitting element is a beam light that is generally close to a dot shape and spreads radially.
[0008]
FIG. 7A shows an example using a light guide pipe. The light emitted from the light source 11 is expanded into a wide line like an arrow drawn with a broken line through a light guide pipe 12 made of a transparent acrylic resin, for example, and then the light incident end face of the light guide plate 2 21 is incident.
The light guide pipe 12 has one end surface or both end surfaces at the end in the longitudinal direction serving as a light incident wall surface 121. On one wall surface that intersects the light incident wall surface 121, for example, a saw-tooth light guide prism array 123 is provided. It has been. The other wall surface facing the light guide prism array 123 is a light emitting wall surface 122.
[0009]
The beam light emitted from the light source 11 and incident into the light guide pipe 12 from the light incident wall surface 121 in a dot shape is reflected in a direction intersecting with the light incident on the inclined surface of the light guide prism array 123 provided continuously. The light exits from the exit wall 122 as a flat light beam as indicated by an arrow drawn by a linear broken line corresponding to the length of the light guide pipe 12. Then, for example, the light enters the light guide plate 2 from the light incident end face 21 of the light guide plate 2 disposed close to the light emitting wall surface 122.
[0010]
When the light guide pipe 12 is used, there is an advantage that the spot-like light emitted from the light source 11 can be spread and emitted in advance so as to be uniform in the width direction of the light guide plate 2. However, in the case of the light source device 1 using the light guide pipe 12, the light source 11 is attached to the light incident wall surface 121 of the light guide pipe 12, so that the number of the light sources 11 can be increased in order to increase the light quantity. It is hard to do.
[0011]
FIG. 7B shows a configuration in which, for example, the light source 11 made of a semiconductor light emitting element is directly attached to the light incident end face 21 of the light guide plate 2. The beam light emitted radially from the point light source 11 radiates and enters the light guide plate 2 from the light incident end face 21 of the light guide plate 2 as indicated by the arrows drawn with broken lines.
When the light source is directly attached to the light guide plate 2, light can be incident from the light source 11 into the light guide plate 2 with almost no loss. Moreover, the amount of light can be easily increased by increasing the number of light sources 11. However, as a matter of course, the light incident on the light guide plate 2 has a large difference in brightness and a large amount of light.
[0012]
FIG. 8 is a schematic diagram showing unevenness in the amount of light of the surface illumination device. 8A shows an example in which the light guide pipe 12 is used in the light source device 1, and FIG. 8B shows an example in which the semiconductor light emitting element of the light source 11 is directly attached to the light incident end face 21 of the light guide plate 2. It is. The unevenness in the amount of light is originally a halftone, but it is difficult to illustrate, so it is indicated by hatching in this figure.
In FIG. 8A, light emitted from the light source 11 is expanded as a light beam flat in the width direction of the light guide plate 2 by the light guide pipe 12. However, the light emitted from the light guide pipe 12 is not uniform in the width direction. For this reason, the light propagating through the light guide plate 2 causes unevenness in the amount of light called, for example, a strip shape or a stripe shape. That is, even if the light guide pipe 12 is used as the light source 11, it is troublesome to uniformly enter the entire surface of the light guide plate 2 without unevenness in the amount of light.
[0013]
In FIG. 8B, since the light source 11 is directly attached to the light incident end face 21 of the light guide plate 2, the brightness of the light emitted radially from the light source 11 appears as unevenness in the light guide plate 2 as it is. It is troublesome to eliminate the unevenness of the light amount uniformly.
Accordingly, various proposals have been made in order to reduce unevenness in the amount of light incident on the light guide plate from the light source. For example, a light scatterer is mixed in the light guide plate or an optical member is added.
[0014]
FIG. 9 is a schematic side view of an example for reducing unevenness in the amount of light. The surface illumination device 10 shown here is an example in which the light scatterer 3 is mixed in the light guide plate 2. That is, in the transparent plastic material constituting the light guide plate 2, for example, light scatterers 3 such as glass coarse particles are scattered. Further, the reflection sheet 4 is provided close to the back side of the light guide plate 2, and the lens sheet 7 is provided close to the light emitting surface 22 on the opposite surface side.
[0015]
The light indicated by the broken line incident on the light guide plate 2 is diffusely reflected and scattered by the light scatterer 3, and the light emitted from one light emitting surface 22 is directed vertically by the lens sheet 7 as illumination light 5. Exit. The light directed to the other side is once emitted from the back side to the outside, then reflected by the reflection sheet 4 provided nearby, returned to the light guide plate 2 again, emitted from the light emission surface 22 and perpendicular to the lens sheet 7. Is converted into illumination light 5. (For example, refer to Patent Document 1).
[0016]
FIG. 10 is a schematic side view of another example for reducing unevenness in the amount of light. The surface illumination device 10 shown here is an example in which a prism array 23 is provided on the light guide plate 2 and a diffusion sheet 8 is provided nearby. That is, a prism array 23 is provided in a stepped manner on the back side of the light guide plate 2 made of a transparent plastic material, and the diffusion sheet 8 is provided close to the light emitting surface 22 on the opposite surface side. It has become.
[0017]
Light indicated by a broken line incident from the light source 11 is reflected by the prism array 23 and emitted from the light emitting surface 22. Further, in order to reduce unevenness in the amount of light, the light is diffused by the diffusion sheet 8 provided close to the light emitting surface 22 and leveled to become the illumination light 5. (For example, refer nonpatent literature 1.).
[0018]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-45651 (Example, FIG. 1)
[0019]
[Non-Patent Document 1]
Matsushita Technical Journal Vol. 47 No. 3 p. 2 (2001)
[0020]
[Problems to be solved by the invention]
As described above, in the surface illumination device, the illumination light is expanded to the size of the object to be illuminated without losing the light amount emitted from the light source while maintaining a simple configuration, so that the unevenness of the light amount does not occur in the illumination light. Is important.
That is, in order to obtain uniform illumination light by a surface illumination device, for example, in a light source device, a light guide pipe is used to expand a dotted light source as a line light source in the width direction of the light guide plate, or the light guide plate Has been devised such as mixing light scatterers. However, it is necessary to attach a lens sheet, a diffusion sheet, a reflection sheet, or the like as a lighting device. Therefore, it has been insufficient to construct a simpler and cheaper lighting device.
[0021]
Therefore, the present invention provides a uniform surface illumination light even if a light scatterer is scattered in the light guide plate and a prism array is provided to use a light guide pipe as the light source or directly attach the light source to the light guide plate. It is an object of the present invention to provide a liquid crystal display device including a surface illumination device that is provided and a liquid crystal display panel that is illuminated by the surface illumination device according to the present invention.
[0022]
[Means for Solving the Problems]
The above-described problem is that, in the first aspect of the present invention, in claim 1, the light source device includes a light guide plate, a light guide plate, and a reflective sheet, and the light source device emits at least one semiconductor light emitting element. The light guide plate includes a point light source and a light guide pipe that linearly expands the light emitted from the light source, and the light guide plate intersects the light incident direction on the back surface and the light incident direction on the back surface. The reflecting sheet is formed of a transparent thin plate having a prism array in which the first steep slope and the second gentle slope are continuous in a side view, and a light emitting surface facing the prism array. Is arranged near the back of the light guide plate, and the light guide plate has light scatterers scattered in the plate, and scatters light passing through the plate and reflects it on the steep slope. It illuminates an object to be illuminated by being emitted from the light exit surface It is solved by configured planar illumination device.
[0023]
In other words, the light source device has a light guide pipe so that the light is expanded linearly to the full width of the light guide plate. This light is guided from the light incident end face of the light guide plate. The light guide plate is provided with a prism array on the back surface, and light scatterers are scattered in the plate. In addition, a reflective sheet is provided near the back surface of the light guide plate.
In the light guide plate, the incident light is scattered by the light scatterer and then goes directly to the light exit surface, and the light that is reflected by the first steep slope of the prism array and then goes to the light exit surface. Both are emitted from the light exit surface to become illumination light.
[0024]
In any case, most of the light incident on the light guide plate is once scattered by the light scatterer. Therefore, even if the light incident from the light guide pipe in the light guide plate has a band-like light amount unevenness, the light amount unevenness is scattered and eliminated by the light scatterer, and uniform illumination light can be obtained.
Next, a second invention of the present invention relates to claim 2 or 3. First, in claim 2, the light source includes a light source and a light guide plate, and the light source includes a point-like light source emitted from at least one semiconductor light emitting element, and the light guide plate has a light incident on the light source. A light guide plate comprising a transparent thin plate having an end face, a double prism array that is formed in a sawtooth shape parallel to the light incident end face, and a light output surface that faces the double prism array The light scatterers are scattered in the plate and scatter the light passing through the plate, and the light is reflected by the two-sided prism array and emitted from the light emitting surface to illuminate the object to be illuminated nearby. This is solved by the surface illumination device configured as described above.
[0025]
Further, in claim 3, the two-ridge-connected prism array has a second ascending slope, a first apex, a third descending steep slope, and an ascending first steep slope in a side view with the light emitting surface facing up. The four steep slopes and the second apex are connected in order, and the two-mountain prism array is arranged such that the second apex and the valley of the second steep slope next to the second steep slope are the second gentle slope. This is solved by the surface illumination device according to claim 2 configured to be continuous at the slope.
[0026]
In other words, the double mountain prism array is formed by dividing the top of the conventional single prism array into two peaks and connecting the second steep slope up to the first peak of the first mountain and the first mountain. Each of the steep slopes of the second steep slope of the second peak of the second mountain connected from the third steep slope descending next through the V-shaped valley enters the light guide plate from the light source. So that it becomes a reflective surface of the light.
[0027]
Then, the light that has passed through the second steep slope without being completely reflected and once emitted out of the prism, that is, out of the light guide plate, is returned to the light guide plate again at the third steep slope down the first mountain. It can be reflected by the fourth steep slope that leads to.
In addition, a downward gentle slope is connected between the second apex and the valley of the second steep slope that continues next. That is, the light propagation path is gradually expanded in the light guide plate in the light traveling direction.
[0028]
As a result, the thickness of the light guide plate gradually increases between each of the two-sided prism array and the next two-sided prism array, so that the light scattered by the light scatterer is more efficient. Can be directed to the next double prism array. Moreover, if the downward slope of the second gentle slope that connects each of the two-sided prism array is adjusted: θ, the distance between the two-sided prism array that is connected to the light emitting surface gradually increases as the distance from the light source increases. It is also possible to increase the reflection efficiency on the second and fourth steep slopes that are close to each other, that is, by gradually reducing the thickness T of the light guide plate.
[0029]
As a result, the amount of light transmitted through the prism array of the light guide plate and leaked and lost can be reduced, and light scattering by the light scatterer is improved to reduce unevenness in the amount of light and enter the light guide plate from the light source. The reflected light can be efficiently reflected and used as uniform illumination light.
Next, a third aspect of the present invention relates to claim 4, 5 or 6. First, in claim 4, the light scatterer is solved by the surface illumination device according to claim 1, wherein the light scatterer is formed of a coarse particle of glass.
[0030]
That is, since the material of the light guide plate is made of transparent plastics and is formed by molding, coarse particles of glass are previously mixed in the material as a light scatterer.
The glass coarse particles may be spherical, but may not necessarily be spherical but may be a pulverized polyhedron. Since the coarse particles are mixed to reduce unevenness of the light strip in the light guide plate, literally, the light reflected by the steep slope of the prism array is directed to the light exit slope in the light guide plate. It is enough to be scattered.
[0031]
Further, in claim 5, the light scatterer is solved by the surface illumination device according to claim 1, wherein the light scatterer is formed of a coarse particle of plastics incompatible with the plastics of the light guide plate.
That is, the material of the light guide plate is made of transparent plastics by molding. Therefore, as the light scatterer mixed in the material in advance, for example, thermosetting plastics having heat resistance at the time of molding is used as plastics incompatible with the material of the light guide plate.
[0032]
The coarse particles of these plastics may be spherical as in the case of the coarse particles of glass, or may be a polyhedron that is not necessarily spherical but pulverized. Furthermore, in order for the light reflected by the steep slope of the prism array to effectively travel to the light exit slope, it is only necessary to literally be scattered in the light guide plate.
Furthermore, in claim 6, the light scatterer is solved by the surface illumination device according to claim 1, wherein the light scatterer is formed of a coarse metal particle.
[0033]
In other words, the metal coarse particles are made of metal spheres having a metallic luster. Since the coarse metal particles themselves are opaque to light, the light guide plate becomes opaque if mixed in a large amount. Therefore, it is sufficient to be literally scattered.
Finally, according to a fourth aspect of the present invention, in claim 7, the liquid crystal display panel is disposed near the light emitting surface of the surface illumination device according to claim 1 or 2 and illuminated from the back side. This is solved by the liquid crystal display device configured.
[0034]
In other words, the surface illumination device according to the present invention eliminates unevenness in the amount of light that occurs in the light guide plate, whether the light source is incident on the light guide plate through the light guide pipe or the light source is directly attached to the light guide plate. Can be suppressed. In view of this, the surface illumination device according to the present invention is arranged close to the rear surface side of the transmissive liquid crystal display panel with the light emission surface facing each other.
[0035]
As a result, it is possible to achieve backlight-type illumination without unevenness in light quantity while taking advantage of the thin features of the liquid crystal display panel, so that it is possible to realize a very thin and very light display device for mobile phones, PDAs, etc. it can.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
1 is a partially cutaway perspective view schematically showing the first invention of the present invention, FIG. 2 is a schematic diagram showing the behavior of light in FIG. 1, and FIG. 3 is a schematic diagram of the second invention of the present invention. FIG. 4 is a schematic diagram showing the behavior of light in FIG. 3, FIG. 5 is a diagram illustrating the effect of the present invention, and FIG. 6 is a schematic diagram of the fourth invention of the present invention.
[0037]
In the figure, 1 is a light source device, 11 is a light source, 12 is a light guide pipe, 121 is a light incident wall surface, 122 is a light exit wall surface, 123 is a light guide prism array, 2 is a light guide plate, 21 is a light incident end surface, 22 is Light exit surface, 23 is a prism array, 231 is a first steep slope, 232 is a first gentle slope, 24 is a double prism array, 241 is a first vertex, 242 is a second vertex, 243 is a first 2 steep slopes, 244 is a 3rd steep slope, 245 is a 4th steep slope, 246 is a 2nd gentle slope, 3 is a light scatterer, 4 is a reflective sheet, 5 is illumination light, 6 is a liquid crystal display device, 61 is A liquid crystal display panel 10 is a surface illumination device.
[First Embodiment] (First Invention: Claim 1)
FIG. 1 shows a partially cutaway perspective view schematically showing the first invention of the present invention, and FIG. 2 shows a schematic diagram showing the behavior of light. In FIG. 1, the surface illumination device 10 includes a light source device 1, a light guide plate 2, and a reflection sheet 4.
[0038]
In FIG. 1A, the light source device 1 includes a point light source 11 emitted from at least one semiconductor light emitting element, and a light guide pipe 12 that linearly expands the light emitted from the light source 11.
The light guide pipe 12 is made of a molded product of transparent acrylic plastics, for example, and the light source 11 is provided close to one end or both ends in the longitudinal direction. The light emitted from the light source 11 enters the light guide pipe 12, and although not shown here, a light guide prism array is provided on one wall surface as shown in FIG. Is emitted as linear light from the other light emission wall surface 122.
[0039]
Since the light incident end face 21 of the light guide plate 2 faces and is close to the light emitting wall surface 122, the light emitted from the light guide pipe 12 spreads to the full width of the light guide plate 2 and enters.
The light guide plate 2 is also made of a molded product of transparent acrylic plastics, for example, and light scatterers 3 are scattered in the plastics constituting the light guide plate 2. That is, it molds using the plastics which knead | mixed the light-scattering body 3 beforehand in the plastics to shape | mold.
[0040]
On the back side of the light guide plate 2 is provided a prism array 23 in which a first steep slope 231 and a first gentle slope 232 are arranged in parallel in a sawtooth shape in parallel with the light incident end face 21. The steep slope 231 serves as a reflection surface for light propagating through the light guide plate 2. Further, the surface side of the light guide plate 2 facing the prism array 23 is a light emitting surface 22.
[0041]
The reflection sheet 4 is formed, for example, by metallizing an aluminum thin film on the surface of a thin plate of acrylic plastics, and has a configuration close to the prism array 23 on the back side of the light guide plate 2.
In FIG. 1 (B), instead of the light source device 1 shown in FIG. 1 (A), a light source 11 made of a semiconductor light emitting element such as a light emitting diode is directly attached to the light incident end face 21 of the light guide plate 2. It has a configuration.
[0042]
Light scatterers 3 are scattered in the light guide plate 2. Further, a prism array 23 in which a first steep slope 231 and a first gentle slope 232 are connected is provided on the back side of the light guide plate 2, and the surface side of the light guide plate 2 facing the prism array 23 is a light emitting surface 22. It has become. Further, on the back side of the light guide plate 2, the reflection sheet 4 is provided close to the prism array 23.
[0043]
In FIG. 2, a part of the light indicated by the thick arrows incident from the light incident end face 21 of the light guide plate 2 is, for example, on the first steep slope 231 of the prism array 23 as indicated by the broken line in the light guide plate 2. The light is reflected and emitted from the light emitting surface 22 as illumination light 5. Further, another part of the incident light indicated by the thick arrow is directed to the light emitting surface 22 while being scattered by the light scatterer 3 or to the first steep slope 231, for example. Of the incident light indicated by the thick arrows, for example, light that has passed through the first steep slope 231 and exited from the light guide plate 2 is reflected by the reflection sheet 4 and again in the light guide plate 2. Is incident on. Further, another part of the incident light indicated by the thick arrow is emitted while being scattered by the light scatterer 3 before being emitted from the light emitting surface 22, for example.
[0044]
In any case, the light indicated by the broken line propagating through the light guide plate 2 will be scattered if it hits the light scatterer 3. Moreover, as shown in the side view in the figure, scattering by the light scatterer 3 occurs in all three-dimensional directions. Therefore, the band-like light amount unevenness caused when entering from the light incident end face 21 due to the light guide pipe of the light source device or the light / dark light quantity unevenness caused due to the configuration in which the light source is directly attached to the light incident end face 21. Is leveled by the light scatterer 3 in the light guide plate 2, and unevenness in the amount of light is erased when illuminating an object to be illuminated not shown as illumination light 5 from the light exit surface 22.
[Second Embodiment] (Second Invention: Claim 2 or 3)
FIG. 3 shows a partially cutaway perspective view schematically showing the second invention of the present invention, and FIG. 4 shows a schematic diagram showing the behavior of light. In FIG. 3, the surface illumination device 10 includes a light source 11 and a light guide plate 2.
[0045]
In FIG. 3A, a light source 11 is a semiconductor light emitting element that emits light in at least one dot shape. In this case, three light sources 11 are directly attached to the light incident end face 21 of the light guide plate 2. Yes.
The light guide plate 2 is made of a molded product of transparent acrylic plastics, for example, and the light scatterers 3 are scattered in the plastics constituting the light guide plate 2. That is, it molds using the plastics which knead | mixed the light-scattering body 3 beforehand in the plastics to shape | mold.
[0046]
On the back side of the light guide plate 2, there is provided a double prism array 24 arranged in a sawtooth shape in parallel with the light incident end face 21, and the surface side facing the double prism array 24 emits light. A surface 22 is formed.
The double mountain prism array 24 has a shape in which the apex of the prism array is divided into two. That is, when viewed from the side with the light output surface 22 facing up, the second rising steep slope 243, the first vertex 241, the third falling steep slope 244, the fourth rising steep slope 245, and the second vertex 242. It is the structure that and are connected in order. In addition, the second apex 242 and the valley of the second steep slope 243 that continues next are connected by the second gentle slope 246 that descends.
[0047]
In FIG. 3 (B), the light source device 1 is arranged close to the light guide plate 2 in place of the light source 11 shown in FIG. 3 (A). The light source device 1 includes a point light source 11 emitted from at least one semiconductor light emitting element and a light guide pipe 12 that linearly expands the light emitted from the light source 11.
Light scatterers 3 are scattered in the light guide plate 2. A double prism array 24 is provided on the back side of the light guide plate 2, and the light emitting surface 22 is the surface facing the double prism array 24.
[0048]
In FIG. 4, a part of the light indicated by the thick arrows incident from the light incident end face 21 of the light guide plate 2 is, for example, the second of the prism array 24 in the double mountain array, as indicated by the broken line in the light guide plate 2. The light is reflected by the steep slope 243 and emitted from the light emitting surface 22 as the illumination light 5, and the light scatterer 3 scatters in the meantime. Further, another part of the incident light indicated by the thick arrow is directed directly to the light emitting surface 22 while being scattered by the light scatterer 3 or to the second steep slope 243, for example. Of the incident light indicated by the thick arrow, for example, the light that has passed through the second steep slope 243 that has gone up and once exited from the light guide plate 2 is guided again from the third steep slope 244 that has come down. Illumination light 5 that enters the light plate 2, is reflected by the fourth rising steep slope 245, exits from the light exit surface 22, and illuminates an unillustrated object near the light exit surface 22; Become.
[0049]
Further, in the double mountain prism array 24, the second gentle slope 246 between the valleys of the second apex 242 and the next rising second steep slope 243 has a downward slope. The direction in which light propagates in the light guide plate 2 is expanded. As a result, the light that has not been reflected by the reflecting surfaces such as the second steep slope 243 and the fourth steep slope 245 in the foreground is propagated more efficiently forward, and the subsequent reflecting surfaces are more efficiently reflected. .
[0050]
Further, the distance between the first vertex 241 and the second vertex 242 of the two-sided prism array 24 and the light emitting surface 22, that is, the thickness T of the light guide plate 2: the second gentle slope 246 emits light. When the inclination angle θ formed with the emission surface 22 is adjusted, the thickness T of the light guide plate 2 gradually decreases as the light travels in the traveling direction. As a result, the first vertex 241 and the first vertex 241 gradually approach the light emitting surface 22, and light reflection at the second steep slope 243 and the fourth steep slope 245 is facilitated.
[0051]
In any case, in FIGS. 3 to 4, the light indicated by the broken line propagating through the light guide plate 2 scatters in any one-dimensional direction when it hits the light scatterer 3. Accordingly, unevenness in the amount of light and darkness that occurs when the light source 11 is directly attached to the light incident end face 21, and unevenness in the band-shaped amount of light that occurs when the light enters the light incident end face 21 due to the light guide pipe 12 of the light source device 1 Is leveled by the light scatterer 3 in the light guide plate 2.
[0052]
In addition, the two-sided prism array 24 reflects light that has leaked out of the light guide plate 2 into the light guide plate 2 and is reflected by the two reflecting surfaces of the second steep slope 243 and the fourth steep slope 245. There is also an effect that is repeated. As a result, unevenness in the amount of light is eliminated when the illumination light 5 is emitted from the light emission surface 22.
[Third Embodiment] (Third Invention: Claim 4, 5 or 6)
2 or 4, the material of the light guide plate 2 is formed by molding transparent plastics. Therefore, the light scattering body 3 is kneaded in advance in the plastic material constituting the light guide plate 2.
[0053]
First, of the light scatterer 3, soda glass, borosilicate glass, quartz glass, or the like can be used for the coarse particles of glass. Flint glass (lead glass) is more effective as the light scatterer 3 because of its high refractive index. Depending on the purpose, transparent colored glass may be used.
If the coarse particles are spherical, for example, particles having a diameter of several tens of μm are used. However, in the case of a pulverized polyhedron, it does not necessarily have a spherical shape, and is a size that can be sieved with a nominal size of a mesh sieve, for example, 53 to 125 (standard sieve opening of 53 to 125 μm in JIS). It's okay.
[0054]
In addition, in order for the light reflected by the reflecting surfaces such as the first steep slope 231, the second steep slope 243, and the fourth steep slope 245 provided on the back side of the light guide plate 2 to head toward the light exit surface 22 effectively, It is sufficient that the light guide plate 2 is moderately dispersed in the light guide plate 2. For example, mixing of about 1% by weight is also effective.
Next, coarse particles made of plastics that are incompatible with the plastics that are the material of the light guide plate 2 can be used as the light scatterer 3. The material of the light guide plate 2 is made of transparent plastics by molding. Therefore, as the light scatterer 3 mixed in the material of the light guide plate 2 in advance, for example, thermosetting plastics that are thermally incompatible with the material of the light guide plate 2, for example, acrylic plastics. Melamine-based, phenol-based, and epoxy-based resins can be used.
[0055]
If these plastics coarse particles are spherical, particles having a diameter of several tens of μm, for example, are used. However, it is not necessarily spherical, and in the case of a pulverized polyhedron, the nominal size of a mesh sieve, for example, 53 to 125 may be used.
In addition, in order for the light reflected by the reflecting surfaces such as the first steep slope 231, the second steep slope 243, and the fourth steep slope 245 provided on the back side of the light guide plate 2 to head toward the light exit surface 22 effectively, It is sufficient that the light guide plate 2 is moderately dispersed in the light guide plate 2. For example, mixing of about 5% by weight is also effective.
[0056]
Furthermore, the light scatterer 3 can also be comprised by the coarse particle body of a metal. The metal coarse particles are made of metal, such as aluminum and nickel, which are easily reflected and scattered in the plastics of the base material of the light guide plate 2.
When the metal coarse particles are spherical, for example, particles having a diameter of several to several tens of μm are used. However, it is not always necessary to have a spherical shape, and in the case of a polyhedron, the nominal size of a mesh screen, for example, 53 to 125 may be used.
[0057]
Since the coarse metal particles themselves are opaque to the light, the light guide plate itself becomes opaque if mixed in a large amount. Accordingly, it may be literally scattered, and the mixing amount of the light guide plate with respect to the material is, for example, about 0.1% by weight.
FIG. 5 illustrates the effect of the present invention. That is, the illumination light emitted in the vertical direction from the surface of the light guide plate 2 from the surface illumination device 10 having the prism array 23 on the back side and the light guide plate 2 in which the light scatterers 3 are scattered and the reflection sheet 4 is combined. 5 shows the result of measuring the light quantity of 5 while scanning the entire surface of the light guide plate 2 in a grid pattern. Luminance (cd / cm ² ) Is set to 100% for the position of the latest Y = 0 in the light source device 1.
[0058]
The curve shown by the solid line shows the effect of the present invention. The curve indicated by the broken line indicates the unevenness in the amount of illumination light 5 emitted from the surface illumination device 10 that does not include the light scatterer 3 in the light guide plate 2 and that does not have a reflection sheet close to the back side of the light guide plate 2. This is a reference example in the case where the light incident from the light source device 1 has a band-like bright and dark light amount unevenness in the light guide plate 2. When viewed in the width direction of the light guide plate 2, that is, in the X direction, in the reference example of the dashed curve, the band-like light and darkness is particularly clear in the immediate vicinity of the light source device 1.
[0059]
On the other hand, in the case of a solid local line in which the light scatterers 3 are scattered in the light guide plate 2 and the reflection sheet 4 is provided close to the back side of the light guide plate 2, the light scattering included in the light guide plate 2. Scattering occurs by the body 3. Further, light that has passed through the prism array 23 and leaked out of the light guide plate 2 is returned to the light guide plate 2 by the reflection sheet 4.
Then, even if it is the light source device 1 which provided the light guide pipe 12, even if it directly attaches a light source to the light-guide plate 2, as shown with the continuous line of a continuous line, the light quantity nonuniformity can be improved significantly.
[0060]
Light scatterers are scattered in the light guide plate, and a prism array is provided on the back side of the light guide plate. It has been confirmed that the light guide plate 2 in which the continuous prism array is provided on the back side and the light scatterers are scattered has the characteristic of greatly improving the unevenness of the light amount.
[Fourth Embodiment] (Fourth Invention: Claim 7)
FIG. 6 schematically shows a liquid crystal display device 6 that illuminates the liquid crystal display panel 61 in a backlight manner by the surface illumination device 10 according to the present invention. The surface illumination device 10 shown in FIG. 6A is a combination of the light guide plate 2 and the reflection sheet 4 in which the light scatterers 3 are scattered, and the light guide plate 2 is provided with a prism array 23. . The surface illumination device 10 shown in FIG. 6B has a configuration in which a double prism array 24 is provided on the light guide plate 2 in which the light scatterers 3 are scattered.
[0061]
Whether using the light source device 1 in which the point light source 11 is expanded to the full width of the light guide plate 2 by a light guide pipe, or when the point light source 11 such as a semiconductor light emitting element is directly attached to the light guide plate 2. Since the light is scattered by the light scatterer 3 in the light guide plate 2, unevenness in the amount of light and darkness generated in the light guide plate 2 is diffused.
As a result, the liquid crystal display panel 61 can prevent unevenness in the amount of light generated in the light guide plate 2 due to the light source from reaching the illumination light 5, and the liquid crystal display device 6 illuminated uniformly can be obtained.
[0062]
The silhouette of the unevenness in the amount of light in the light guide plate caused by the light source exemplified here is variously deformed depending on the configuration of the light source. Therefore, various modifications can be made to the type, specifications, content, and the like of the light scatterers mixed in the light guide plate depending on the unevenness of the amount of light.
In addition, specifications such as pitch and height of the prism array provided on the light guide plate and the double prism array are not uniquely determined, and various modifications are possible.
[0063]
【The invention's effect】
According to the surface illumination device according to the present invention, when a light source device using a light guide pipe is used as a light source incident on the light guide plate, a semiconductor light emitting device chip or the like is directly attached to the light guide plate. However, unevenness in the amount of light caused by the light source can be reduced with a simple configuration.
[0064]
Therefore, the present invention will be increasingly multifunctional, diversified, light and thin, and will contribute greatly to the field of display devices such as liquid crystal display devices that require external illumination.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view schematically showing a first invention of the present invention.
FIG. 2 is a schematic diagram showing the behavior of light in FIG.
FIG. 3 is a partially cutaway perspective view schematically showing a second invention of the present invention.
4 is a schematic diagram showing the behavior of light in FIG. 3. FIG.
FIG. 5 is a diagram illustrating the effect of the present invention.
FIG. 6 is a schematic diagram of the fourth invention of the present invention.
FIG. 7 is a perspective view schematically illustrating a configuration example of a light source device.
FIG. 8 is a schematic diagram showing unevenness in the amount of light of the surface illumination device.
FIG. 9 is a schematic side view illustrating an example of reducing unevenness in light amount.
FIG. 10 is a schematic side view of another example for reducing unevenness in the amount of light.
[Explanation of symbols]
1 Light source device
11 Light source
12 Light guide pipe
121 Light entrance wall 122 Light exit wall
123 Light Geite Prism Array
2 Light guide plate
21 Light incident end face
22 Light exit surface
23 Prism array
231 First steep slope 232 First gentle slope
24 Futamiyama prism array
241 first vertex 242 second vertex
243 2nd steep slope 244 3rd steep slope
245 4th steep slope 246 2nd gentle slope
3 Light scatterers
4 reflection sheet
5 Illumination light
6 Liquid crystal display device
61 LCD panel
10 surface lighting device

Claims (7)

A light source device, a light guide plate, and a reflective sheet;
The light source device comprises a point light source emitted by at least one semiconductor light emitting element, and a light guide pipe that linearly expands the light emitted from the light source,
The light guide plate is arranged in a sawtooth shape in parallel with the light incident end face near the light source device and the back surface so as to intersect the light incident direction, and the first steep slope and the first gentle slope are connected in a side view. A transparent thin plate having a prism array and a light emitting surface facing the prism array,
The reflection sheet is provided close to the back surface of the light guide plate,
The light guide plate has light scatterers scattered in the plate, scatters light passing through the plate, reflects the light from the steep slope, and emits light from the light emitting surface to illuminate an object to be illuminated nearby. A surface illumination device. A light source and a light guide plate;
The light source comprises a point light source emitted by at least one semiconductor light emitting element,
The light guide plate includes: a light incident end face near the light source; a double prism array formed in a sawtooth shape parallel to the light incident end face; and a light facing the double prism array Consisting of a transparent thin plate having an exit surface,
The light guide plate includes light scatterers scattered in the plate, scatters light passing through the plate, and reflects the object to be illuminated by reflecting it from a two-sided prism array to be emitted from the light emitting surface. A surface illumination device characterized by being illuminated. The two-sided prism array includes a second ascending slope, a first apex, a descending third steep slope, an ascending fourth steep slope, The vertices are connected in order,
3. The surface illumination according to claim 2, wherein the two-sided prism array has the second apex and the valley of the second steep slope next to each other connected by a downward second gentle slope. apparatus. 3. The surface illumination device according to claim 1, wherein the light scatterer is made of a coarse particle of glass. 3. The surface illumination device according to claim 1, wherein the light scatterer comprises a coarse particle of plastics incompatible with the plastics of the light guide plate. 3. The surface illumination device according to claim 1, wherein the light scatterer is made of a metal coarse particle. 3. A liquid crystal display device, wherein the liquid crystal display panel is illuminated from the back side close to the light emitting surface of the surface illumination device according to claim 1 or 2.

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