JPH11237633A - Sidelight type surface light source and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decrease of emitted light at a corner part on the side of an incident surface by repeatedly forming projections, which are extended while being inclined obliquely to an end face by a prescribed cross-sectional shape, at the corner part on the side of the end face and forming this projection by connecting a pair of slopes having a prescribed inclination to an emission surface. SOLUTION: A light transmission plate 11 is formed into a cross-sectional wedge by the injection molding of a transparent member such as acryl, for example, and the illuminating light of a primary light source 3 is made incident from an incident surface 11A on the end face. Further, concerning the light transmission plate 11, projections 12 in the prescribed cross-sectional shape are repeatedly formed at both the terminal parts of the incident surface 11A outside the effective light emitting area of a fluorescent lamp 8. In this case, this projection 12 is formed into cross-sectional triangular shape by directly connecting a pair of slopes 12A and 12B extended vertically to an emission surface 11C. Besides, this projection 12 is prepared by forming a groove on the emission surface 11C by a pair of slopes inclined just at a prescribed angle to the emission surface 11C.

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 a liquid crystal display device, and more particularly, to a sidelight type surface light source device formed of a plate-like member whose thickness becomes thinner as the distance from an incident surface increases. It can be applied when configuring. According to the present invention, a projection formed by a pair of slopes extending obliquely with respect to the incident surface is formed at a corner of the exit surface on the incident surface side, so that the effective light emitting area of the effective surface is smaller than the length of the incident surface. Even when a short primary light source is applied, it is possible to reduce a decrease in the amount of emitted light at a corner on the incident surface side.

Further, by forming a minute rough surface at a corner on the end face side of the exit surface so that the proportion of the unit area gradually decreases as the distance from the corner increases, the surface is more effective than the length of the entrance surface. Even when a primary light source having a short light emitting region is applied, it is possible to reduce a decrease in the amount of emitted light at the corner on the incident surface side.

[0003]

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 composed of a rod-shaped light source is arranged on a side of a plate-shaped member (that is, composed of a light guide plate), and illumination light emitted from the primary light source is applied to an end face of the light guide plate. More light enters the light guide plate. 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.

[0005] Such a side light type surface light source device is as follows.
A method in which the light guide plate is formed with a substantially uniform thickness,
There is a type in which the thickness of the light guide plate is gradually reduced as the distance from the primary light source increases, and the latter can emit illumination light more efficiently than the former.

FIG. 7 is an exploded perspective view showing an example of the latter sidelight type surface light source device 1, and FIG. 8 is a cross-sectional view of FIG. 7 cut along line AA. In this sidelight type surface light source device 1, a primary light source 3 is arranged on a side of a light guide plate 2, and a reflection sheet 4, a light guide plate 2, a light diffusion sheet 5, and prism sheets 6 and 7 serving as light control members are sequentially laminated. Formed.

The primary light source 3 is formed by surrounding a fluorescent lamp 8 composed of a cold cathode tube with a reflector 9, and illuminating light from an opening side of the reflector 9 to an end face (hereinafter referred to as an incident face) 2 A of the light guide plate 2. Is incident. Here reflector 9
Is formed of, for example, a sheet material that specularly or irregularly reflects incident light.

The light guide plate 2 is formed in a wedge-shaped cross section 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 which is an end surface. Thereby, the light guide plate 2 repeatedly reflects between the reflection sheet 4 side plane (hereinafter, referred to as a rear surface) 2B and the light diffusion sheet 5 side plane (hereinafter, referred to as an exit 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. 7, light scattering ink made of, for example, magnesium carbonate, titanium oxide, or the like is selectively adhered so that the degree of light scattering gradually increases from the incident surface 2A side toward the wedge-shaped tip. Formed. The light scattering surface 2D is
In some cases, instead of the light scattering ink, the back surface 2B is partially formed on a matte surface (textured surface). Also in this case, similarly, the light scattering surface 2D forms, at a constant pitch, or at random, for example, a rectangular-shaped area having a matte surface, and the area of each rectangular-shaped area increases from the incident surface 2A side toward the wedge-shaped tip. It is formed to increase. Thereby, the light guide plate 2
Makes the light amount distribution of the outgoing light uniform over almost the entire area of the outgoing surface 2C.

Although the illumination light is scattered in this way, the light guide plate 2 basically has a back surface 2B and an emission surface 2C.
And the illumination light is repeatedly reflected and propagates the illumination light, and the angle of incidence of the illumination light on the emission surface is reduced each time the light is reflected on the inclined surface, and a component having a critical angle or less is emitted from the emission surface 2C. . Therefore, the illumination light emitted from the emission surface 2C is formed such that the main emission direction is inclined toward the wedge-shaped tip.

The prism sheets 6 and 7 are arranged to correct the directivity of the light guide plate 2. The light diffusion sheet 5 diffuses the emitted light, and the light scattering surface 2D of the back surface 2B from the emission surface 2C side. In order not to be recognized, furthermore, it is arranged so that the brightness, the shadow and the like of each part of the light guide plate 2 illuminated by the illumination light are inconspicuous.

That is, the light diffusion sheet 5 scatters and emits the illumination light emitted from the light guide plate 2. Each of the prism sheets 6 and 7 is formed of a translucent sheet material such as polycarbonate, and has a prism surface on a surface opposite to a surface facing the light guide plate 2. This prism surface is formed by repeatedly forming protrusions having a triangular cross section extending substantially parallel to one direction. In this example, the prism sheet 6 on the light guide plate 2 side is formed.
The prism sheet 7 is arranged such that the projection extends in a direction substantially orthogonal to the incidence surface 2A, such that the projection extends substantially parallel to the incidence surface 2A.

Thus, the prism sheets 6 and 7 correct the main emission direction of the emitted light to the front direction of the emission surface 2C on the slopes of the triangular projections. Note that a so-called double-sided prism sheet having a structure in which prism surfaces are formed on both sides may be used as the prism sheet. As a result, in the sidelight type surface light source device 1, emitted light can be emitted more efficiently than in a sidelight type surface light source device in which a light guide plate is formed with a substantially uniform thickness.

In the side light type surface light source device 1 according to the principle of emitting illumination light, the reflection sheet 4 is a sheet-shaped regular reflection member made of a metal foil or the like, or a sheet-shaped irregular reflection made of a white PET film or the like. The illumination light, which is formed of a member and leaks from the back surface 2B, is reflected and incident on the light guide plate 2, thereby improving the utilization efficiency of the illumination light.

[0015]

In such a side light type surface light source device 1, the fluorescent lamp 8 is
Electrodes 8A and 8B are formed at both ends.
In the vicinity of A and 8B, a region where the phosphor is not applied is formed in the tube. Therefore, in the fluorescent lamp 8, regions where the illumination light L is not emitted are formed near both ends, and the illumination light is emitted only from the central portion (that is, the effective light emission region) excluding these regions.

Thus, in this type of sidelight type surface light source device, when the length of the fluorescent lamp 8 is shortened, as shown by reference numeral B (FIG. 7), the amount of outgoing light at the incident surface side corner is reduced. There is a problem that the brightness is partially reduced and uneven brightness occurs.

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 a decrease in the amount of emitted light at a corner on an incident surface side.

[0018]

According to the present invention, an illumination light emitted from a predetermined light source is incident on an end face of a plate-like member, and the illumination light is bent to form the plate-like member. The present invention is applied to a sidelight type surface light source device that emits light from an emission surface. In the front emission surface of the side light type surface light source device, a protrusion extending in a predetermined cross-sectional shape in a direction inclined obliquely with respect to the end surface is repeatedly formed at a corner on the end surface side, and this protrusion is emitted. A pair of inclined surfaces having a predetermined inclination with respect to the surface are connected and formed.

At this time, the projections are formed so that the depth decreases as the distance from the end surface increases.

At these times or instead, the projections are formed such that the inclination of the pair of slopes with respect to the emission surface is set equal.

At these times or alternatively, 1
Of the pair of slopes, the angle between the slope mainly used for emitting the illumination light and the normal line of the emission surface is set to be approximately 25 degrees.

At these times, or alternatively, at least one end of the end face extends in a direction perpendicular to the emission surface.
The protrusions formed by the pair of slopes are repeatedly formed.

At this time or in place of this, of the pair of slopes formed on the end face, the angle formed by the slope facing the center of the light source and the normal of the end face is in the range of 40 to 45 degrees. To be.

Alternatively, a liquid crystal display panel,
A side light type surface light source device for supplying illumination light to the liquid crystal display panel, wherein the side light type surface light source device receives illumination light emitted from a predetermined light source from an end surface of the plate member. This is applied when the illumination light is bent and emitted from the emission surface of the plate-shaped member. In this liquid crystal display device, on the exit surface of the plate-like member, a protrusion extending in a predetermined cross-sectional shape is repeatedly formed at a corner on the end surface side in a direction oblique to the end surface, and the protrusion is formed. And a pair of inclined surfaces having a predetermined inclination with respect to the emission surface.

At this time, the projections are formed so that the depth becomes smaller as the distance from the end surface increases.

At this time or in place of this, the projections are set so that the inclination of the pair of inclined surfaces with respect to the emission surface is equal.

At these times or instead of these, 1
Of the pair of slopes, an angle formed by a slope mainly used for emitting illumination light and a normal line of the emission surface is set to approximately 25 degrees.

At this time or in place of this, at least one end of the end face extends in a direction perpendicular to the emission surface.
The protrusions formed by the pair of slopes are repeatedly formed.

At this time or in place of this, the angle formed by the slope facing the center of the light source and the normal to the end face in the range of 40 to 45 degrees among the pair of slopes formed on the end face. To do.

Further, the present invention is applied to a sidelight type surface light source device in which illumination light emitted from a predetermined light source is incident from an end face of a plate member, and this illumination light is bent and emitted from an emission surface of the plate member. The emission surface is formed with a fine rough surface at a corner on the end face side so that the ratio of the emission surface to the unit area gradually decreases as the distance from the corner increases.

The side light type surface light source device illuminates the liquid crystal display panel.

On the exit surface of this type of sidelight type surface light source device, protrusions extending in a predetermined sectional shape are repeatedly formed at the corners on the end surface side of the plate member, and these protrusions are formed as follows.
If a pair of inclined surfaces having a predetermined inclination are connected to the exit surface and formed, the illumination light component having a large incident angle with respect to the exit surface, which is the main illumination light component at this corner, is efficiently emitted. be able to. Also, if this projection is formed to extend in a direction obliquely inclined with respect to the end face, the incident angle of the illumination light component obliquely incident from the end face, which is the main illumination light component at this corner, is reduced. The light can be emitted more efficiently by that amount, and thereby, the amount of light emitted from this corner can be increased. Further, the directivity of the emitted light can be set by the extension direction of the protrusion.

At this time, if the projection is formed so that its depth becomes shallower as the distance from the end surface increases, the boundary between the corner where the projection is formed and another region can be made difficult to perceive. .

At these times or in place of this, if the projections are formed by setting the inclination of the pair of slopes with respect to the emission surface to be equal, the projections can be easily formed.

At these times or in place of these, 1
Of the pair of slopes, if the angle formed by the slope mainly used for emitting the illumination light and the normal line of the emission surface is set to be approximately 25 degrees, the directivity of the illumination light emitted from other regions is improved. Light can be emitted with almost the same directivity.

At this time, or in place of this, at least one end of the end face extends in a direction perpendicular to the emission surface.
By repeatedly forming the projection by the pair of slopes, the illumination light component incident on the slope facing the center of the light source in the slopes can be distributed to the corners.

At this time or in place of this, of the pair of slopes formed on the end face, the angle formed by the slope facing the center of the light source and the normal of the end face is in the range of 40 to 45 degrees. This makes it possible to efficiently distribute the illumination light component obliquely incident on the end face to the corner side by applying to a plate member made of a general transparent member.

Further, the present invention is applied to a liquid crystal display device using the same sidelight type surface light source device, and the sidelight type surface light source device has a plate-like member. If a protrusion extending in a predetermined cross-sectional shape is repeatedly formed in a direction obliquely inclined with respect to the output surface, and the protrusion is formed by connecting a pair of slopes having a predetermined inclination with respect to the emission surface, this corner is formed. It is possible to efficiently emit the illumination light component, which is the main illumination light component in the portion, which is obliquely incident from the end face and is incident on the emission surface at a large incident angle, and it is possible to increase the emission light amount at this corner. it can.

At this time, if the projections are formed so that the depth becomes shallower as the distance from the end face increases, the boundary between the corner and the other area can be made difficult to perceive.

At this time or in place of this, if the projections are formed by setting the inclination of the pair of slopes with respect to the emission surface to be equal, the projections can be easily formed.

At these times or instead of these, 1
Of the pair of slopes, if the angle formed by the slope mainly used for emitting the illumination light and the normal line of the emission surface is set to be approximately 25 degrees, the directivity of the illumination light emitted from other regions is improved. Illumination light can be emitted with substantially the same directivity.

At these times, or alternatively, at least one end of the end face extends in a direction perpendicular to the emission surface.
By repeatedly forming the projection by the pair of slopes, the illumination light component incident on the slope facing the center of the light source in the slopes can be distributed to the corners.

At this time or in place of this, of the pair of slopes formed on the end face, the angle between the slope facing the center of the light source and the normal of the end face is in the range of 40 to 45 degrees. This makes it possible to efficiently distribute the illumination light component obliquely incident on the end face to the corner side by applying to a plate member made of a general transparent member.

The present invention is applied to a sidelight type surface light source device, and a fine rough surface is formed at a corner on the end face side so that a ratio of the light emitting surface to a unit area gradually decreases as the distance from the corner increases. If so, it is possible to select the ratio to the unit area, to keep the directivity degradation within a practically sufficient range, and to promote the emission of the illumination light propagating inside. Can be increased.

As a result, the liquid crystal display panel can be illuminated by the sidelight type surface light source device, and the luminance unevenness of the display screen can be reduced.

[0046]

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

(1) First Embodiment FIG. 1 is an exploded perspective view showing a side light type surface light source device according to an embodiment of the present invention in comparison with FIG. In the sidelight type surface light source device 10, a light guide plate 11 is applied instead of the light guide plate 2. In the sidelight type surface light source device 10, the same configurations as those of the sidelight type surface light source device 1 in FIG. 7 are denoted by the corresponding reference numerals, and the repeated description will be omitted. The reflection sheet 4 is made of white P
An irregular reflection member made of an ET film is applied.

Here, the light guide plate 11 is formed into a wedge-shaped cross section by injection molding, for example, acrylic made of a transparent member, and receives the illumination light of the primary light source 3 from an incident surface 11A which is an end surface. Further, as shown in an enlarged manner by arrow C, the light guide plate 1
In 1, protrusions 12 having a predetermined cross-sectional shape are repeatedly formed on both ends of the incident surface 11 </ b> A outside the effective light emitting area of the fluorescent lamp 8. Here, this projection 12 is formed in a triangular cross section by directly connecting a pair of slopes 12A and 12B extending in a direction perpendicular to the emission surface 11C.

As further shown in FIG. 2, the light guide plate 11
The pair of slopes 12A and 12B are set to have the same inclination with respect to the incident surface 11A, and the pair of slopes 12A and 12B are further inclined.
And 12B form an angle θ of approximately 80 degrees. The angle θ can be set to a desired angle within a range of 80 to 90 degrees to obtain a suitable result. Thus, in this embodiment, the inclined surface 12A facing the effective light emitting area AR on the center side of the fluorescent lamp 8 is inclined at 40 degrees with respect to the incident surface 11A so as to extend in the vertical direction, and the incident surface indicated by a broken line. When no projection is formed on 11A, compared to the range AR1 included in the critical angle α,
A range AR2 included in the critical angle α on the slope 12A is directed to the side surface of the light guide plate 11.

Further, the light guide plate 11 (FIG. 1)
In C, protrusions 13 having a predetermined cross-sectional shape are repeatedly formed at the corners on the incident surface 11A side. Here, this projection 13
It is formed by forming a groove in the emission surface 11C by a pair of inclined surfaces inclined by a predetermined angle with respect to the emission surface 11C. Here, the projection 13 is formed to be inclined with respect to the incident surface 11A so as to extend from the corner to the center of the emission surface 11C. The projections 13 are repeatedly formed at a predetermined pitch in a direction orthogonal to the extending direction, and correspond to changes in the amount of emitted light when the emission surface 11C is formed of a flat surface, and gradually increase in depth as the distance from the corner increases. Is formed so as to decrease.

Further, as shown in FIG. 3 by taking a cross section by a plane perpendicular to the extension direction of the projection 13, the pair of slopes 13A and 13B are set to have the same inclination with respect to the emission surface 11C. A pair of slopes 13A and 13B
Form an angle θ of approximately 50 degrees.
Thereby, in this embodiment, the slope 1 facing the wedge-shaped tip side is used.
3B is inclined at an angle of 25 degrees (angle β) with respect to the exit surface 11C, and when no projection is formed on the exit surface 11C indicated by a broken line, the light enters the exit surface 11C at an incident angle larger than the critical angle. The illumination light component L totally reflected by the emission surface 11C can also be emitted from the inclined surface 13B.

In the above configuration, the illumination light L emitted from the fluorescent lamp 8 is directly (see FIG. 1) and (see FIG. 8)
Alternatively, after being reflected by the reflector 9, the light enters the light guide plate 11 from the incident surface 11A, and the illumination light propagates inside the light guide plate 11 while being repeatedly reflected between the inclined surface and the emission surface. At this time, each time the illumination light is reflected by the inclined surface, the incident angle with respect to the emission surface 11C decreases, and a component equal to or smaller than the critical angle with respect to the emission surface 11C is emitted from the emission surface 11C. Further, at this time, the illumination light is diffused by the light scattering surface of the light guide plate 11 to be emitted from the emission surface, and the amount of emitted light is made uniform in the direction from the incident surface 11A toward the wedge-shaped tip.

The illumination light that enters the light guide plate 11 and exits from the exit surface 11C in this manner is incident on the entrance surface 11A.
Focusing on the incidence from one point (FIG. 2), the incidence surface 11A
The illumination light that has arrived at is subjected to refraction according to the refractive index of the light guide plate 11 according to Snell's law, enters the inside of the light guide plate 11, and from the incident point is included in a range AR1 included at the critical angle α.
It is distributed to.

In the area corresponding to the effective light emitting area AR of the fluorescent lamp 8 on the incident surface 11A, the illuminating light is incident with a sufficient amount of light. Since the AR1 continuously overlaps along the longitudinal direction of the fluorescent lamp 8, the illumination light propagates inside with a sufficient amount of light.

On the other hand, the electrodes 8A and 8A of the fluorescent lamp 8
At the portion corresponding to the B side, the illumination light comes from the direction inclined toward the center of the fluorescent lamp 8, and the amount of the illumination light that reaches the incident surface 11A decreases.
In addition, the overlapping of the area AR1 covered by the critical angle is reduced as approaching the side surface side, so that the amount of illumination light propagating inside the light guide plate 11 is reduced.

However, in this embodiment, the projections 12 formed by the pair of slopes 12A and 12B are formed in this area, so that the slope facing the effective light emitting area AR side of the pair of slopes 12A and 12B. 12A, the range AR2 included in the critical angle α of the slope 12A is set so as to face the side surface of the light guide plate 11, whereby the amount of illumination light incident on these regions is reduced. It is distributed to the side that is doing. Thus, the amount of emitted light at the incident surface side corner of the emission surface 11C is increased as compared with the case where the incidence surface 11A is formed of a flat surface.

Further, as described above, the illumination light that propagates through the inside of the light guide plate 11 and is emitted from the emission surface 11C emits a component having a critical angle or less with respect to the emission surface 11C. At the corner on the incident surface side, the illumination light arrives from the direction inclined toward the center of the fluorescent lamp 8, so that the component having a large incident angle with respect to the emission surface 11C occupies most of the small illumination light. Become.

In this embodiment (FIG. 3), the projection 13 formed by the pair of slopes 13A and 13B is formed at this corner, so that the corner is flattened as shown by a broken line. When the emission surface 11C is formed, the component that has been totally reflected on the emission surface 11C at an incident angle equal to or greater than the critical angle is actively emitted by the slope 13B. Further, since the extending direction of the projection 13 extends from the corner toward the center of the emission surface 11C, the projection surface 13 is inclined obliquely.
The illumination light at the center of the main distribution is incident on the inclined surface 13B at a small incident angle and is positively emitted.

Incidentally, in the illumination light component which enters from the entrance surface 11A and directly reaches the exit surface 11C, the incident surface 1
The component incident from 1A at the critical angle α is the smallest incident angle 9
The light enters the output surface 11C by 0-α. Here, the angle α is about 42.1 degrees in the acrylic material, and thus the illumination light enters the output surface 11C at a maximum incident angle of 47.9 degrees (90-α). Thus, when the emission surface 11C is formed flat, there is no light that can be directly emitted from the emission surface 11C among the light that can be incident from the incident surface 11A.

However, in this embodiment, it is possible to emit light even in the range of 47.9 degrees to 42.1 degrees of the incident angle with respect to the flat exit surface 11C, thereby increasing the amount of emitted light at the corners.

It is also conceivable to emit the component at such a large incident angle by making the exit surface 11C partially rough. In this case, as shown by a symbol L2 in FIG. 4, the component exits from the exit surface 11C. The directivity of the illumination light is dull. As a result, the illumination light is emitted with a different directivity from the other portions, and the overall illumination light amount is observed, although the emitted light amount is increased, but the luminance level of the emission surface is reduced as compared with the other portions. Will be.

However, if protrusions are formed at the corners as in this embodiment, emitted light can be emitted with sharp directivity, as indicated by the symbol L1. At this time, as in this embodiment, if the inclination of the slope 13B facing the wedge-shaped tip direction (that is, a slope mainly emitting illumination light) is set to 25 degrees with respect to the emission surface 11C, the other Can be emitted with almost the same directivity as the region of (1).
Thus, even in the subsequent correction of the directivity by the prism sheets 6, 7 and the like, the directivity of the emitted light can be corrected to be substantially the same as the directivity characteristics of the other areas, thereby efficiently increasing the luminance level of the emitted light. Can be.

As shown in FIG. 5, the same symbols are attached for comparison with FIG. 4, and the luminance level is measured in the direction along the incident surface, as shown in FIG. 5. It has been found that the luminance level at the corner of the incident surface can be improved as compared with the related art.

In this embodiment, the depth of the projection formed by the pair of slopes 13A and 13B is gradually increased as the distance from the corner increases, corresponding to the amount of emitted light when the emission surface 11C is formed by a flat surface. Due to the reduction, the boundary with the other area where the protrusion is not formed is maintained in a hardly perceptible state, thereby preventing the emission surface from being uncomfortable.

According to the above configuration, a pair of inclined projections extending in a direction inclined obliquely to the incident surface are repeatedly formed at the incident surface side corner of the exit surface. In addition, even when the emission surface is formed by a flat surface, the component that has been totally reflected can also be efficiently emitted, whereby the luminance level at the corner can be increased.

Further, since a pair of sloped projections extending in the direction perpendicular to the emission face are repeatedly formed at the end of the incidence face, the side face side is illuminated by the slope facing inward of the pair of slopes. The light can be distributed, and thus, the amount of emitted light at the corner can be increased.

Also, the protrusion 13 at the corner of the exit surface is formed so that the depth gradually decreases as the distance from the entrance surface increases, so that the boundary between the corner where the protrusion is formed and another region can be perceived. By making it difficult, it is possible to prevent a sense of incongruity on the emission surface.

The slopes 12A, 12B, 13
By forming A and 13B with the same inclination, these projections can be easily formed.

At this time, the angle between the inclined surface 13B, which is mainly used for emitting the illumination light, and the normal line of the emission surface 11C is approximately 25 degrees on the emission surface 11C. The illumination light can be emitted with almost the same directivity as the directivity of the illumination light to be emitted, whereby the luminance level can be efficiently increased.

Further, of the pair of slopes formed on the incident surface, the angle between the slope 12A facing the center of the light source and the normal line of the incident surface 11A is in the range of 40 to 45 degrees. Thereby, the illumination light component obliquely incident on the incident surface 11A can be efficiently distributed to the corner side to increase the light quantity at the corner.

(2) Second Embodiment FIG. 6 is an exploded perspective view showing a sidelight type surface light source device according to a second embodiment. In this side light type surface light source device 20, instead of the light guide plate 11, a light guide plate 21 is used.
The configuration is the same as that of the sidelight type surface light source device 10 described above with reference to FIG.

Here, the light guide plate 21 is formed into a wedge-shaped cross section by injection molding, for example, acrylic made of a transparent member, and receives the illumination light of the primary light source 3 from an incident surface 21A which is an end surface. In the light guide plate 21, the incident surface 21A is formed by a flat mirror surface.

Further, in the light guide plate 21, as shown in an enlarged manner by an arrow D, a minute rough surface 21E is formed at a corner portion on the incident surface 21A side on the exit surface 21C. Here, the rough surface 21E is formed by selectively adhering a light-scattering ink using, for example, magnesium carbonate, titanium oxide or the like as a pigment. Note that the rough surface 21E may be formed by partially forming the emission surface 21C on a matte surface (textured surface) instead of the light scattering ink. Thereby, the light guide plate 21 is configured to promote the emission of the illumination light propagating through the inside by the rough surface 21E.

Further, the rough surface 21E is formed on the emission surface 21C such that the ratio of the rough surface 21E to the unit area gradually decreases as the distance from the corner increases. Furthermore, individual rough surfaces 21
E is formed with a small diameter that is difficult to perceive when viewed from the exit surface 21C side, and in this embodiment, is formed in a circular shape (dot shape) having a diameter of 50 [μm]. Thereby, the light guide plate 21
By avoiding the above-mentioned problem that the directivity of the illumination light becomes dull by partially roughening the exit surface, degradation of the directivity of the exit light is kept within a practically sufficient range, The amount of emitted light that is insufficient at the corner of 21C can be increased, and the deterioration of the quality that the rough surface 21E is perceived when viewed from the exit surface 21C side is avoided.

Further, the rough surface 21E is formed on the light emitting surface 21C by random arrangement, so that interference with the liquid crystal display panel due to the regular arrangement can be prevented.

According to the configuration shown in FIG. 6, a fine rough surface 21E is formed at the corner of the exit surface 21C on the incident surface 21A side so that the proportion of the unit area per unit area gradually decreases as the distance from the corner increases. Even when a primary light source having an effective light emitting area shorter than the length of the incident surface is used, it is possible to reduce the decrease in the amount of emitted light at the corner on the incident surface side.

(3) Other Embodiments In the first embodiment described above, a case has been described in which an inclined surface is formed with an equal inclination on the exit surface.
The present invention is not limited to this, but the point is that the slope facing the center of the emission surface of the pair of slopes can be made a desired slope to increase the amount of emitted light at the corners, so that the slopes of the pair of slopes are different. You may let it.

Similarly, in the above-described first embodiment, the case where the slope is formed on the incident surface with the same inclination has been described. However, the present invention is not limited to this. By making the inclined surface facing the center of the light source a desired inclination, the amount of emitted light at the corners can be increased.
The slopes of the paired slopes may be different.

In the first embodiment described above,
Although the case where the pair of slopes formed on the exit surface and the entrance surface are directly connected has been described, the present invention is not limited to this. For example, the connection is made by a curved surface, and the case where the slope itself is formed by a curved surface is also widely used. Can be applied.

Further, in the above-described first embodiment, the case where the projections are formed at a constant pitch on the emission surface has been described. However, the present invention is not limited to this, and the pitch may be changed.

In the first embodiment described above,
On the exit surface, the case where the apex angle due to the inclined surface is kept constant and the depth of the projection is made shallower as going away from the entrance surface has been described, but the present invention is not limited to this, The depth of the protrusion may be reduced as the distance from the surface increases.

In the above-described first embodiment,
On the incident surface, the case where the protrusions with a constant shape are repeated has been described. However, the present invention is not limited to this.For example, when gradually reducing the depth of the protrusions toward the center,
The cross-sectional shape may be variously changed.

In the above-described first embodiment,
On the emission surface, the case where the depth of the protrusions is gradually reduced has been described. However, the present invention is not limited to this.For example, when a light diffusion sheet having a large degree of light scattering is used,
In such a case, the change in the light amount distribution of the illumination light emitted from the light guide plate is reduced by the light diffusion sheet. In such a case, the depth of the protrusion may be reduced stepwise. Alternatively, in addition to this, the amount of emitted light may be made uniform by changing the length of the protrusion.

Further, in the above-described first embodiment, the case where the projections are formed partially on the entrance surface and the exit surface has been described. However, the present invention is not limited to this. If a sufficient amount of light can be obtained, the projection on the incident surface may be omitted. Conversely, in the configuration according to the second embodiment, a projection may be formed on the incident surface.

Further, in the above-described embodiment, the case where the light guide plate having the light scattering surface formed by printing is applied. However, the present invention is not limited to this, and a partially rough surface is formed by matte surface treatment. The present invention can be widely applied to the case where a light guide plate having a light scattering surface is formed.

In the above-described embodiment, the case where the reflector 9 and the reflection sheet 4 are constituted by the irregular reflection member has been described.
The present invention can be widely applied to a case where a regular reflection member made of a sheet material on which silver is deposited is used as the reflection sheet.

Further, in the above-described embodiment, a case has been described in which two single-sided prism sheets are laminated on the exit surface of the light guide plate. However, the present invention is not limited to this, and for example, two prism sheets may be used instead of two prism sheets. When a so-called double-sided prism sheet is used, one prism sheet is used instead of two prism sheets.
The present invention can be widely applied to a case where a sheet material is arranged on the exit surface by various structures, for example, when two prism sheets are used.

In the above embodiment, the case where the light scattering surface is formed on the back surface 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 emission surface of the light guide plate is described. Alternatively, the present invention can be widely applied to a case where a light scattering surface is formed on the emission surface and the back 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 embodiment, the case where the present invention is applied to the sidelight type surface light source device using the light guide plate formed of a plate-like member having a wedge-shaped cross section has been described, but the present invention is not limited to this. Instead, the present invention can be widely applied to a sidelight type surface light source device using a flat light guide plate having a substantially uniform plate thickness.

Further, in the above-described embodiment, the case where the primary light source is constituted by the fluorescent lamp which is a rod-shaped light source has been described. However, the present invention is not limited to this. Can also be widely applied to the formation of

Further, in the above-described embodiments, 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.

[0093]

As described above, according to the present invention, a pair of sloped projections extending obliquely with respect to the incident surface are provided.
By forming it at the corner of the exit surface on the incident surface side, it is possible to efficiently emit the illumination light from the plate-like member at the corner, and to reduce the decrease in the amount of emitted light at this corner. Also, by forming a fine rough surface at the corner of the exit surface on the incident surface side so that the proportion of the unit area gradually decreases as the distance from the corner increases, the effective light emitting area is reduced compared to the length of the incident surface. Even when a primary light source having a short length is used, it is possible to reduce the decrease in the amount of emitted light at the corner on the incident surface side.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a sidelight type surface light source device according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged plan view showing an incident surface side of the sidelight type surface light source device of FIG. 1;

FIG. 3 is an enlarged plan view showing a corner of an exit surface of FIG. 1;

FIG. 4 is a characteristic curve diagram showing directivity at a corner.

FIG. 5 is a characteristic curve diagram showing a luminance level of emitted light.

FIG. 6 is an exploded perspective view showing a sidelight type surface light source device according to a second embodiment of the present invention.

FIG. 7 is an exploded perspective view showing a conventional sidelight type surface light source device.

FIG. 8 is a cross-sectional view of FIG. 7 cut along line AA.

FIG. 9 is a plan view showing the back surface of the light guide plate.

[Explanation of symbols]

1, 10, 20 ... side light type surface light source device, 2, 1
1, 21... Light guide plate, 2A, 11A, 21A... Incident surface, 2C, 11C, 21C... Outgoing surface, 3... Primary light source, 8... Fluorescent lamp, 8A, 8B.
3. Projection, 12A, 12B, 13A, 13B ... Slope

Claims (14)

[Claims] 1. A sidelight type surface light source device which irradiates illumination light emitted from a predetermined light source from an end face of a plate-like member, bends the illumination light and emits the illumination light from an emission surface of the plate-like member. The emission surface is formed at a corner on the end surface side with a projection repeatedly extending in a direction oblique to the end surface with a predetermined cross-sectional shape, and the projection has a predetermined inclination with respect to the emission surface. A side light type surface light source device formed by connecting a pair of slopes having: 2. The side light type surface light source device according to claim 1, wherein the protrusion is formed so as to have a smaller depth as the protrusion is separated from the end face. 3. The sidelight type surface light source device according to claim 1, wherein the protrusions are set to have the same inclination of the pair of slopes with respect to the emission surface. 4. An angle between a slope mainly used for emitting the illumination light and a normal line of the emission surface of the pair of slopes is approximately 25 degrees. The side light type surface light source device according to claim 2 or 3. 5. A projection formed by a pair of inclined surfaces extending in a direction perpendicular to the emission surface at least at an end of the end surface. The side light type surface light source device according to claim 4. 6. A pair of slopes formed on said end face,
The angle formed by a slope facing the center side of the light source and a normal line of the end face is in a range of 40 to 45 degrees. 6. The sidelight type surface light source device according to 5. 7. A liquid crystal display device having a liquid crystal display panel and a sidelight type surface light source device for supplying illumination light to the liquid crystal display panel, wherein the sidelight type surface light source device emits light from a predetermined light source. In a side light type surface light source device in which illumination light is incident from an end surface of a plate-shaped member, and the illumination light is bent and emitted from an emission surface of the plate-shaped member, the emission surface is provided at a corner on the end surface side, A protrusion extending in a predetermined cross-sectional shape is repeatedly formed in a direction obliquely inclined with respect to the end surface, and the protrusion is formed by connecting a pair of slopes having a predetermined inclination to the emission surface. A liquid crystal display device characterized by the above-mentioned. 8. The liquid crystal display device according to claim 7, wherein the projection is formed so that the depth becomes smaller as the projection becomes more distant from the end face. 9. The liquid crystal display device according to claim 7, wherein the projections are set to have the same inclination of the pair of slopes with respect to the emission surface. 10. An angle formed between a slope mainly used for emitting the illumination light and a normal line of the emission face, of the pair of slopes,
9. The method according to claim 7, wherein the angle is approximately 25 degrees.
Or the liquid crystal display device according to claim 9. 11. A projection formed by a pair of inclined surfaces extending in a direction perpendicular to the emission surface at least at an end of the end surface. The liquid crystal display device according to claim 10. 12. An angle between a slope facing the center of the light source and a normal line of the end face of the pair of slopes formed on the end face is in a range of 40 to 45 degrees. Claim 7, Claim 8, Claim 9, Claim 10, or Claim 11
3. The liquid crystal display device according to 1. 13. A sidelight-type surface light source device which irradiates illumination light emitted from a predetermined light source from an end surface of a plate member, bends the illumination light and emits the illumination light from an exit surface of the plate member. A side light type surface light source device, wherein a fine rough surface is formed at a corner on the side of the end surface so that a ratio of the light emitting surface to a unit area gradually decreases as the distance from the corner increases. 14. A liquid crystal display device, wherein the side light type surface light source device according to claim 13 illuminates a liquid crystal display panel.