JP3322596B2 - Sidelight type surface light source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidelight type surface light source device, and more particularly to a sidelight type surface light source device which corrects the color of illumination light by a wavelength conversion sheet disposed on an emission surface of a plate-like member and emits the light. Applicable. The present invention, the emission surface side of the plate-shaped member or the surface side facing the emission surface,
By forming a light-absorbing region having wavelength selectivity in a region close to the point light source, a change in color tone is effectively avoided, and a local increase in the amount of emitted light near the point light source is reduced.

[0002]

2. Description of the Related Art Conventionally, for example, in a liquid crystal display device,
A liquid crystal display panel is illuminated by a sidelight type surface light source device, thereby reducing the overall shape.

That is, in the sidelight type surface light source device, a primary light source is arranged on a side of a plate-like member (that is, a light guide plate), and illumination light emitted from the primary light source is transmitted from an end face of the light guide plate to the light guide plate. Incident. Further, the sidelight type surface light source device bends the illumination light and emits it from the plane of the light guide plate toward the liquid crystal display panel, whereby the overall shape can be reduced in thickness.

[0004] Such a side light type surface light source device is
There are a system in which the primary light source is configured by a rod-shaped light source such as a fluorescent lamp, and a system in which the primary light source is configured by a point light source such as a light emitting diode. The latter can simplify the driving circuit of the primary light source. And so on.

FIG. 9 is an exploded perspective view showing an example of the latter side light type surface light source device 1, and FIG.
FIG. 2 is a cross-sectional view taken along line AA of FIG. The side light type surface light source device 1 includes a primary light source 3
And the reflection sheet 4, the light guide plate 2, the wavelength conversion sheet 6
Are sequentially laminated.

[0006] The primary light source 3 is formed by mounting a plurality of light emitting diodes 7 as point light sources on a holding member 8 such as a printed circuit board. (Referred to as an incident surface) 2A. Here, as this type of light emitting diode 7, for example, a blue light emitting diode that emits blue illumination light is applied.

The light guide plate 2 is formed in a flat plate shape by injection molding, for example, acrylic (PMMA resin) made of a transparent member, and receives the illumination light of the primary light source 3 from an incident surface 2A. As a result, the light guide plate 2 repeatedly reflects between the reflection sheet 4 side plane (hereinafter referred to as back surface) 2B and the wavelength conversion sheet 6 side plane (hereinafter referred to as emission surface) 2C and propagates the illumination light. At the time of reflection at 2B and the exit surface 2C, components smaller than the critical angle are emitted from the back surface 2B and the exit surface 2C.

Further, the light guide plate 2 has a light scattering surface 2D formed on the back surface 2B. Here, this light scattering surface 2D corresponds to FIG.
As shown in FIG. 1, the back surface 2B is partially formed to have a textured surface so that the degree of light scattering increases gradually from the incident surface 2A side to the other end. The light scattering surface 2D may be formed by selectively adhering a light scattering ink using, for example, magnesium carbonate, titanium oxide or the like as a pigment instead of the grained surface. More specifically, the light-scattering surface 2D forms, for example, a rectangular matted area with a constant pitch or a random arrangement, and the area of each rectangular-shaped area sequentially from the incident surface 2A side toward the other end. Is formed to increase. As a result, the light guide plate 2 has the back surface 2B and the emission surface 2C.
The illumination light that is repeatedly reflected and propagates between the light-emitting surface and the light-scattering surface 2D is scattered by the light scattering surface 2D, and the component that is smaller than the critical angle with respect to the emission surface 2C is increased. In the sidelight type surface light source device 1, the illumination light is thereby emitted from the emission surface 2C.

The reflection sheet 4 is formed of a sheet-like regular reflection member made of a metal foil or the like, or a sheet-shaped irregular reflection member made of a white PET film or the like, and reflects the illumination light leaking from the back surface 2B to form the light guide plate 2. To improve the efficiency of use of illumination light.

The wavelength conversion sheet 6 is a sheet material containing a fluorescent material. The fluorescent material is excited by blue illumination light to emit light, so that the blue illumination light is corrected to white illumination light and emitted. . At this time, the wavelength conversion sheet 6 diffuses and emits these white illumination lights. Thereby, in the sidelight type surface light source device 1, the point light source by the blue light emitting diode 7 is used as the primary light source, and the white illumination light is emitted from the emission surface 2C.

[0011]

However, such a sidelight type surface light source device 1 has a problem in that a region B where the amount of emitted light is extremely high near the light emitting diode 7 is formed. However, there is a disadvantage that only the region on the tip side except for the above can be used.

If the amount of light emitted from these areas B can be reduced to the same extent as other areas, the light emitting surface of the light guide plate 2 can be used effectively, and the sidelight type surface light source device can be downsized accordingly. can do.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a sidelight type surface light source device capable of reducing the amount of emitted light that increases near a point light source.

[0014]

According to the present invention, in order to solve the above-mentioned problems, illumination light emitted from a point light source is guided to the inside of a plate member, and illumination light propagating in the plate member is transmitted to the plate member. The present invention is applied to a sidelight type surface light source device that emits light from an emission surface. In particular, when the sidelight type surface light source device corrects the color of the illumination light emitted from the emission surface by the wavelength conversion sheet disposed on the emission surface of the plate-shaped member, the emission surface side of the plate-shaped member or A light-absorbing region having wavelength selectivity is formed in a region close to the point light source on a surface side facing the light emitting surface.

At this time, the light absorption region is formed so as to selectively exhibit light absorbency with respect to the wavelength of the illumination light emitted from the point light source.

In these cases, the light absorption region is configured such that the degree of light absorption gradually decreases as the distance from the point light source increases.

In these cases, a light absorbing region is formed by printing a complementary color ink with respect to the color of the illumination light emitted from the point light source.

If the light absorbing region is formed in a region close to the point light source, the amount of emitted light in the region close to the point light source can be reduced. At this time, the difference in color from other regions can be corrected by the wavelength selectivity of the light absorption region.

More specifically, a light absorption region is formed so as to selectively exhibit light absorption with respect to the wavelength of the illumination light emitted from the point light source, thereby effectively avoiding a difference in color tone. ,
It is possible to reduce the amount of emitted light that locally increases.

Further, in these cases, the light absorbing region is configured so that the degree of light absorption gradually decreases as the distance from the point light source increases, thereby preventing an unnatural change in the amount of emitted light.

In these cases, it is possible to easily form the light absorption region by printing ink of a complementary color to the color of the illumination light emitted from the point light source.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is an exploded perspective view showing the sidelight type surface light source device according to the embodiment of the present invention in comparison with FIG. In the sidelight type surface light source device 10, a reflection sheet 11 is applied instead of the reflection sheet 4. In the sidelight type surface light source device 10, the same components as those of the sidelight type surface light source device 1 in FIG. 9 are denoted by the corresponding reference numerals, and the duplicate description will be omitted.

In the reflection sheet 11, a light absorbing region 12 is formed in a region near the light guide plate 2 and in the vicinity of the light emitting diode 7. Here, as shown in FIG. 1 in an enlarged manner, the light absorbing region 12 is formed by printing light absorbing ink in a circular shape at a constant pitch. The size is gradually reduced (FIG. 1A). Thereby, the C-C line and D
As shown in FIG. 1B and FIG. 1C, the light reflection characteristic in the direction of the line D is such that the degree of light absorption of the blue illumination light increases as it approaches the light emitting diode 7 with respect to the blue illumination light. It has been done. Thus, in the sidelight type surface light source device 10, a local increase in the amount of emitted light generated near the light emitting diode 7 is reduced.

Further, as shown in FIG.
Is formed by printing a light-absorbing ink having wavelength selectivity so as to selectively absorb the wavelength of the illumination light.
Specifically, it is formed by printing an ink containing a pigment that is complementary to blue. Thus, in the sidelight type surface light source device 10, the local increase in the amount of emitted light is reduced so that the hue of the illumination light emitted from the emission surface is equal to the hue of the other areas.

In the above configuration, the illumination light emitted from the light emitting diode 7 (FIG. 2) enters the inside of the light guide plate 2 from the incident surface 2A, and the illumination light is applied to the back surface 2B and the emission surface 2C.
The light propagates inside the light guide plate 2 while repeating reflection between the light guide plate 2 and the light guide plate 2. At this time, the illumination light is scattered by the light scattering surface 2D formed on the back surface 2B every time the light is reflected by the back surface 2B, and a component having a critical angle or less with respect to the emission surface 2C generated as a result is emitted from the emission surface 2C. Is emitted. At this time, the illumination light is corrected from blue illumination light to white illumination light by the wavelength conversion sheet 6 arranged on the emission surface 2C.

When the light enters the light guide plate 2 from the light emitting diode 7 in this manner, the illumination light has a large amount of light in the vicinity of the light emitting diode 7, so that if no processing is performed, local illumination occurs locally in the region close to the light emitting diode 7. The amount of emitted light increases.

However, in this embodiment, the blue illumination light is absorbed by the light absorbing region 12 formed on the reflection sheet 4 in the vicinity of the light emitting diode 7 (FIG. 1). The amount of emitted light that increases in a region close to is reduced.

Further, at this time, the blue component of the illumination light is selectively absorbed by the wavelength selection characteristics of the ink constituting the light absorbing region 12, whereby the other region is converted from the wavelength conversion sheet 6 with the same hue. Is emitted.

That is, in the sidelight type surface light source device 10, when the light absorbing region 12 is formed by printing, for example, a black ink exhibiting light absorbing characteristics at all wavelengths, the color of the emitted light is higher than the other regions. It turned out to change slightly. This is considered to be due to the characteristics of the wavelength conversion sheet 6, but the exact reason is unknown. That is, as shown in FIG. 4, in the sidelight type surface light source device 10, a part of the blue illumination light BU is converted into almost yellow illumination light Y in the wavelength conversion sheet 6, and this yellow illumination light Y and the blue Illumination light B
U are emitted from the wavelength conversion sheet 6, thereby generating white illumination light. At this time, when the black ink is printed to form the light absorption region 12, the side light type surface light source device 10 emits not only the blue illumination light BU but also the light toward the light absorption region 12 by the wavelength conversion sheet 6. Since the yellow illumination light Y is also absorbed, this light absorption region 1
It is considered that the hue changes in the area corresponding to 2.

According to the experimental results, an ink containing a pigment having a complementary color to blue is printed, and the light absorbing region 12 is formed so as to selectively absorb the blue illumination light BU. Then, the hue of the illumination light emitted from the emission surface could be corrected to the same hue as other areas.

According to the above configuration, ink is printed on the reflection sheet 4 disposed on the back surface 2B, and light that selectively absorbs blue illumination light is provided in a region close to the light emitting diode 7. By forming the absorption region 12, it is possible to effectively avoid a change in color tone with other regions, and to reduce a local increase in the amount of emitted light near the light emitting diode.

In the above-described embodiment, the case has been described where the light absorbing ink is printed in a circular shape at a predetermined pitch to form the light absorbing region 12, but the present invention is not limited to this. When printing a rectangular shape or the like at a fixed pitch or at random instead of the shape, as shown in FIG. 5, when printing ink in a triangular shape so as to extend longer than the light emitting diode 7 side, as shown in FIG. In the case where the rhombic shape is sequentially reduced in size and printed, the light absorbing region 12 can be formed by printing various shapes.

In the above-described embodiment, the case where the light absorbing region 12 is formed by printing a complementary color ink has been described. However, the present invention is not limited to this, and a sheet material or the like whose color gradually becomes thinner is used. The light absorbing region can be created by various methods, such as when the light absorbing region 12 is formed by arranging the light absorbing regions.

Further, in the above embodiment, the case where the light absorbing region 12 is formed so that the degree of light absorption gradually decreases as the distance from the point light source increases, but the present invention is not limited to this, and the present invention is not limited to this. Above the light absorption area 1
If the boundary between the two cannot be recognized, the light absorbing region 12 may be formed stepwise or rapidly so that the degree of light absorption is reduced.

In the above embodiment, the case where a blue light emitting diode is used as a point light source and this blue illumination light is corrected to white light by the wavelength conversion sheet on the emission surface has been described. The present invention is not limited to this, and can be widely applied to a case where illumination light of this point light source is converted into illumination light of a desired color by a wavelength conversion sheet on an emission surface using point light sources of various colors. In this case, for example, FIG.
As shown in the figure, when white illumination light is emitted using a so-called green light emitting diode, the light absorption region 12 is formed so as to selectively exhibit light absorption for this green color, and the above-described embodiment is performed. The same effect as in the embodiment can be obtained. As shown in FIG. 8, when white illumination light is emitted using a red light emitting diode, the light absorption region 12 is formed so as to selectively show light absorption for the red light, The same effect as in the embodiment can be obtained.

Further, in the above-described embodiment, the case where the illumination light of white light is emitted has been described. However, the present invention is not limited to this, and can be widely applied to the case of emitting illumination light of various colors. it can. In this case, depending on the relationship between the illumination light emitted from the light source and the illumination light emitted from the emission surface as the surface light source device, the wavelength of the illumination light emitted from the light source is different from this, if necessary. In some cases, it is necessary to form a light absorption region so as to selectively exhibit light absorption with respect to wavelength.

In the above-described embodiment, the case where the light absorbing region is formed on the reflection sheet has been described. However, the present invention is not limited to this, and the light absorbing region may be formed on the back surface or the front surface of the light guide plate 2. It may be furthermore, when formed on the light guide plate side of the wavelength conversion sheet, further the wavelength conversion sheet, the light conversion region between the light guide plate, or between the light guide plate, or light guide plate,
It may be inserted between the reflection sheets.

Further, in the above-described embodiment, the case where the light scattering surface is formed by forming the textured surface on the back surface of the light guide plate has been described. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can be applied to a case where a light scattering surface is formed by adhering ink, and can be widely applied to a case where a light scattering sheet or the like is arranged to form a light scattering surface.

In the above embodiment, the case where the light scattering surface is formed on the back surface side of the light guide plate has been described. However, the present invention is not limited to this, and the case where the light scattering surface is formed on the output surface of the light guide plate is described. Alternatively, the present invention can be widely applied to a configuration in which a light scattering surface is formed on both the emission surface and the inclined surface.

Further, in the above-described embodiment, the case where the illumination light is incident from one end face has been described. However, the present invention is not limited to this, and the sidelight type surface is also configured to receive the illumination light from the other end face. It can be widely applied to light source devices.

Further, in the above-described embodiment, the case where the present invention is applied to the side light type surface light source device using the light guide plate made of a flat plate-shaped member has been described. However, the present invention is not limited to this. The present invention can be widely applied to a sidelight type surface light source device using a light guide plate having a wedge-shaped cross section.

Further, in the above-described embodiment, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described. However, the present invention is not limited to this, and the present invention is not limited to this. It can be widely applied to a surface light source device.

[0044]

As described above, according to the present invention, a light-absorbing region having wavelength selectivity is formed in a region close to a point light source on the emission surface side of the plate member or on the surface side facing the emission surface. Thus, it is possible to effectively avoid a change in color tone and reduce a local increase in the amount of emitted light near the point light source.

[Brief description of the drawings]

FIG. 1 is a plan view and a characteristic curve diagram showing a light absorption region of a light guide plate applied to a sidelight type surface light source device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing an overall configuration of a sidelight type surface light source device using the light guide plate of FIG.

FIG. 3 is a characteristic curve diagram showing characteristics of a light absorption region in FIG.

FIG. 4 is a partially enlarged view for describing a light absorption region in FIG. 1;

FIG. 5 is a plan view showing a light absorption region applied to another embodiment.

FIG. 6 is a plan view showing a light absorption region formed by rhombic printing.

FIG. 7 is a characteristic curve diagram showing characteristics of a light absorption region applied to another embodiment.

FIG. 8 is a characteristic curve diagram showing characteristics of a light absorption region applied to a red point light source.

FIG. 9 is an exploded perspective view showing a conventional sidelight type surface light source device.

FIG. 10 is a cross-sectional view of FIG. 7 cut along line AA.

FIG. 11 is a plan view showing the back surface of the light guide plate 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 10 Side light type surface light source device 2 Light guide plate 2A Incident surface 3 Primary light source 4, 11 Reflection sheet 6 Wavelength conversion sheet 7 Light emitting diode 12 Light absorption area

Claims (4)

(57) [Claims] 1. A side light type surface light source device for guiding illumination light emitted from a point light source into a plate member and emitting the illumination light propagating through the plate member from an emission surface of the plate member. By the wavelength conversion sheet disposed on the emission surface of the plate-shaped member, the color tone of the illumination light emitted from the emission surface is corrected, and the emission surface side of the plate-shaped member or the surface side facing the emission surface is corrected. A side light type surface light source device, wherein a light absorption region having wavelength selectivity is formed in a region close to the point light source. 2. The side light type surface light source according to claim 1, wherein the light absorbing region selectively shows light absorbing properties with respect to a wavelength of illumination light emitted from the point light source. apparatus. 3. The sidelight type surface according to claim 1, wherein the light absorbing region is formed so that a degree of light absorption gradually decreases as the distance from the point light source increases. Light source device. 4. The light absorption region according to claim 1, wherein the color of the illumination light emitted from the point light source is printed with ink of a complementary color. The side light type surface light source device according to claim 2 or 3.