JP3360796B2 - Light guide plate, side light type surface light source device and liquid crystal display 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 light guide plate, a side light type surface light source device, and a liquid crystal display device, for example, a side light type surface formed such that the plate-like member becomes thinner as the distance from the incident surface increases. It is applied to a light source device. The present invention has a pair of slopes substantially perpendicular to the emission surface, and one of the slopes facing the center of the light source is formed with a protrusion formed smaller than the other slope, at both ends in the longitudinal direction of the incidence surface. By repeatedly forming the light-emitting area, even when a light source having a small light-emitting area is used, it is possible to reduce a partial decrease in the amount of emitted light near the incident surface.

[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 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.

[0004] Such a side light type surface light source device is
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 side light type surface light source device 1, and FIG. 8 is a cross-sectional view of FIG. 7 taken along the 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.

[0006] The primary light source 3 is formed by surrounding a fluorescent lamp 8 composed of a cold cathode tube with a reflector 9, and illuminates the end face 2 A of the light guide plate 2 from the opening side of the reflector 9. Here, the reflector 9 is formed of, for example, a sheet material that specularly or irregularly reflects incident light.

The light guide plate 2 is formed into 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. As a result, the light guide plate 2 repeatedly reflects between the reflection sheet 4 side plane (hereinafter referred to as a slope) 2B and the light diffusion sheet 5 side plane (hereinafter referred to as an exit plane) 2C, and propagates the illumination light. At the time of reflection at 2B and the exit surface 2C, components smaller than the critical angle exit from the inclined surface 2B and the exit surface 2C.

Further, the light guide plate 2 has a light scattering surface 2D formed on an inclined 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 slope 2B is partially formed on the 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 matte surface area in a rectangular shape, and the area of each rectangular shape area increases from the incident surface 2A side toward the wedge-shaped tip. It is formed to increase. Thereby, the light guide plate 2
Corrects the amount of outgoing light that decreases on the wedge-shaped tip side, and makes the light amount distribution of the outgoing light uniform.

Although the illumination light is scattered in this manner, the light guide plate 2 basically includes the inclined surface 2B and the 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, and the light diffusion sheet 5 prevents the light scattering surface 2D of the inclined surface 2B from being recognized from the exit surface 2C side. Light guide plate 2 illuminated by illumination light
Are arranged so as to make the shine, shadow, etc. of each part 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 the surface opposite to the side 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. Thus, in the sidelight type surface light source device 1, the emitted light can be efficiently emitted in the front direction as compared with the sidelight type surface light source device in which the light guide plate is formed with a substantially uniform plate thickness. I have.

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 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 inclined surface 2B, is reflected and incident on the light guide plate 2, thereby improving the utilization efficiency of the illumination light.

[0014]

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 side light type surface light source device, when the length of the fluorescent lamp 8 is reduced, as shown by reference numeral B (FIG. 7), the amount of emitted light at the end of the incident surface 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 proposes a light guide plate, a sidelight type surface light source device, and a liquid crystal display device capable of reducing a partial decrease in the amount of emitted light near the entrance surface. What you want to do.

[0017]

According to the first aspect of the present invention, an illumination light emitted from a predetermined light source is made incident on an incident surface, and the illumination light is emitted from an emission surface. A light guide plate formed by connecting a pair of slopes substantially perpendicular to the emission surface;
Of the pair of slopes, one slope whose vertical direction faces the center side of the light source, and protrusions formed to be smaller than the other slope are provided along both ends of the incidence surface in the longitudinal direction along the incidence surface. To be formed repeatedly.

In the invention of claim 2, claim 1
In the configuration, a pair of slopes substantially perpendicular to the emission surface are connected, and one of the pair of slopes whose vertical direction faces the center of the light source is connected to the other slope. Protrusions that are formed relatively large are repeatedly formed along the incident surface at portions closer to the center in the longitudinal direction than both ends in the longitudinal direction of the incident surface.

In the invention of claim 3, claim 1 is
Alternatively, in the configuration according to claim 2, a pair of slopes substantially perpendicular to the emission surface are connected to each other, and the pair of slopes are formed to have substantially the same size. It is formed so as to be repeatedly formed along the incident surface at a central portion in the longitudinal direction.

Further, in the invention according to claim 4, illumination light emitted from a predetermined light source enters from an end face of the plate member,
In a side light type surface light source device that emits the illumination light from an emission surface of the plate-shaped member, the light source emits the illumination light from a predetermined light-emitting region, and the plate-shaped member A pair of substantially vertical slopes are connected, and one of the pair of slopes, the vertical direction of which is directed toward the center of the light source, is formed with a projection formed smaller than the other slope, The end face is formed repeatedly at both ends in the longitudinal direction along the end face.

According to a fifth aspect of the present invention, the liquid crystal display panel is illuminated by the side light type surface light source device according to the fourth aspect of the present invention.

At both ends in the longitudinal direction of the incident surface of the light guide plate, main illumination light arrives at a large angle from the center of the light source to the incident surface. 2. A pair of slopes substantially perpendicular to the light exit surface, wherein one of the pair of slopes whose vertical direction faces the center of the light source is the other slope. In the projection formed smaller than the above, the illumination light incident at such a large angle can be bent and guided inside. Thus, according to the configuration of the first aspect, since such projections are repeatedly formed along the incident surface at both ends in the longitudinal direction of the incident surface, the insufficient incident light amount at the corresponding portion is compensated, and the incident surface is improved. Partial decrease in the amount of emitted light in the vicinity can be reduced.

A pair of slopes substantially perpendicular to the emission surface are connected, and one of the pair of slopes whose vertical direction faces the center side of the light source,
For protrusions that are larger than the other slope,
The illumination light can be preferentially distributed to the other slope side. According to the second aspect of the present invention, if such projections are repeatedly formed along the incident surface at portions closer to the center in the longitudinal direction than both ends in the longitudinal direction of the incident surface, these projections can be formed. Illumination light incident on a portion closer to the center in the longitudinal direction than both end portions in the longitudinal direction of the surface can be distributed to the side surface side, and the unevenness of the illumination light propagating inside can be improved.

According to a third aspect of the present invention, the projection is formed by connecting a pair of slopes that are substantially perpendicular to the emission surface, and the pair of slopes is formed to have substantially the same size. The incident illumination light can be distributed to both sides. According to the third aspect of the present invention, if such projections are repeatedly formed along the incident surface at the central portion in the longitudinal direction of the incident surface, the illumination light incident on the central portion in the longitudinal direction can be irradiated on both sides. It is possible to improve the non-uniformity of the illumination light that is distributed to the surface side and propagates inside.

According to the fourth and fifth aspects of the present invention, it is possible to provide a sidelight type surface light source device and a liquid crystal display device capable of reducing a partial decrease in the amount of emitted light near the incident surface. it can.

[0026]

[0027]

[0028]

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

FIG. 2 is an exploded perspective view showing a sidelight 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.

Here, as shown in FIG. 1 on an enlarged scale on the side of the incident surface 11A, the light guide plate 11 has triangular projections 12A, 12B and 12C repeatedly formed on the incident surface 11A. These projections 12A, 12B, and 12C are formed in a triangular cross-section by directly connecting a pair of slopes that are substantially perpendicular to the emission surface and that are maintained at a predetermined angle with respect to the incidence surface 11A. Further, these projections 12A, 12B,
12C is approximately 50 [μm] at the center of the entrance surface 11A.
Is formed at a repetition pitch of

In the light guide plate 11, a portion from the side surface of the light guide plate 11 to a position corresponding to the end of the effective light emitting region AR of the fluorescent lamp 8 is allocated to the illumination light introduction region AR1, and formed in the illumination light introduction region AR1. By the projection 12C, the incident surface 1
Illumination light incident on the light guide plate 1 at a large incident angle with respect to 1A
Lead inside 1.

Further, in the light guide plate 11, a predetermined inner area that follows is allocated to the first illumination light distribution area AR2, and the light enters the light guide plate 11 by the projections 12B formed in the first illumination light distribution area AR2. Distribute the illumination light to the adjacent side. Further, in the light guide plate 11, the remaining central area is allocated to the second illumination light distribution area AR3.
From the projections 12A formed in the illumination light distribution area AR3 of FIG.
The illumination light incident on the light guide plate 11 is distributed to both side surfaces.

As shown in FIG. 3, in the central second illumination light distribution area AR3, the projection 12A formed on the incident surface 11A is formed in an isosceles triangular shape. That is, the protrusion 12A is viewed from the vertical direction of the incident surface 11A.
The lengths D1 and D2 of the slopes S1 and S2 forming the protrusion 12A are formed to be equal. Thereby, each projection 12A of this area AR3 is set so that the amount of incident light on each of the slopes S1 and S2 is equal, and each of the slopes S1 and S2.
Are bent and distributed to both side surfaces.

As shown in FIG. 4, in the illumination light distribution area AR3, the distribution of the quantity of incident light is greatest in the front direction with respect to the incident surface 11A. The illumination light is incident on the inside of the light guide plate 11 due to the characteristics further emphasizing the characteristics. On the other hand, when the protrusions 12A having a vertical angle of 90 degrees were repeatedly formed, it was confirmed that the illumination light in the front direction could be distributed to both sides and incident on the inside of the light guide plate 11.

On the other hand, as shown in FIG.
In the illumination light distribution area AR2, the length D1 of the slope S1 facing the center of the fluorescent lamp 8 when viewed from the vertical direction of the incident surface 11A is the length of the slope S2 facing the electrode side of the fluorescent lamp 8. It is formed longer than the length D2. Thus, each projection 12B of this area AR2 receives almost all of the illumination light incident on the incident surface 11A on the inclined surface S1 facing the center of the fluorescent lamp 8, and distributes the illumination light in a direction refracted by the inclined surface S1. It has been made like that. In this way, the direction in which the illumination light is distributed is closer to the side because the slope S1 faces the center of the fluorescent lamp 8. As a result, the projections 12B are
Is distributed to the adjacent side surface.

On the other hand, as shown in FIG. 6, the projection 12C of the illumination light introduction area AR1 is different from the other projections 12A and 12B.
The length D2 of the slope S2 facing the side surface is longer than that of the slope S2. That is, the projection 12C has a slope facing the center of the fluorescent lamp 8 such that illumination light arriving at a larger angle of incidence with respect to the incident surface 11A than the center of the fluorescent lamp 8 enters the light guide plate 11 at a smaller angle of incidence. S <b> 1 is formed, thereby reducing the rate at which the illumination light incident on the slope S <b> 1 is totally reflected by the slope S <b> 1. That is, the illumination light introduction area AR1 outside the effective light emission area AR as described above.
In (2), the arrival direction of the main illumination light L1 is in the center direction of the fluorescent lamp 8, whereby the projection 12C makes the illumination light L1 incident on the slope S1 efficiently enter the inside of the light guide plate 11.

Further, the inclined surface S1 is arranged such that the emission direction of the illumination light L1 incident from the main arrival direction is equal to that of the light guide plate 11.
The inclination α is set so as to be in the side direction. As a result, the projection 12C efficiently receives the illumination light and distributes the incident illumination light to regions on the incident surface side and the side surface side where the amount of light is insufficient.

On the other hand, the remaining inclined surface S2 can be guided into the light guide plate 11 without being reflected by the inclined surface S2 even when the illumination light L1 is incident on the inclined surface S1 at an angle substantially parallel to the incident surface 11A. The angle β is set so as to be possible. Here, the incident angle θ1 and the output angle θ2 in this case are the angles α and (α + β−90), respectively.
, The slope S2 becomes sin (α + β−9).
0) / sin α> n. Here, n is the refractive index of the light guide plate 11. Thus, in the illumination light introduction area AR1, the illumination light that has entered the light guide plate 11 in the direction of arrival of the main illumination light L1 in the area AR1 is prevented from leaking out of the slope S2.

In the above configuration, the illumination light L emitted from the fluorescent lamp 8 (FIG. 2) is directly or after being reflected by the reflector 9 and then enters the inside of the light guide plate 11 from the entrance surface 11A. The light propagates inside the light guide plate 11 while repeatedly reflecting between the inclined surface and the emission surface. At this time, every time the illumination light is reflected by the inclined surface, the incident angle with respect to the emission surface 11C decreases, and a component having a critical angle or less with respect to the emission surface is emitted from the emission surface. 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.

On the other hand, in the direction along the incident surface (FIG. 1), the illumination light is emitted from the effective light emitting area AR of the fluorescent lamp 8.
The illumination light is transmitted through the incident surface 11 </ b> A and guided into the light guide plate 11. At this time, the amount of illumination light is greatest in the area corresponding to the effective light emitting area AR on the fluorescent lamp 8 side of the incident surface 11A, and is decreased on both sides near the electrodes. In the area corresponding to the effective light emitting area AR, the illumination light mainly arrives from the vertical direction of the incident surface 11A, so that the illumination light is incident on the incident surface 11A at a small incident angle. On the other hand, on both sides near the electrodes, the illumination light emitted from the effective light emitting area AR arrives, so that the illumination light is
A is incident on A at a large incident angle.

In the case where the incident surface 11A is not processed, the illumination light having a small amount of light near the both side surfaces of the incident surface 11A is further totally reflected by the incident surface 11A and guided into the light guide plate 11. Is further reduced as compared with the other areas, and this causes a local decrease in the amount of emitted light.

On the other hand, in this embodiment, the area AR1 inside both sides of the entrance surface 11A corresponding to the electrode.
In FIGS. 1 and 6, the illumination light emitted from the effective light emitting area AR and incident on the incident surface 11A at a large incident angle is incident on the inclined surface S1 of the projection 12C at a small incident angle. When the incident surface is not treated at all, the main component of the illumination light totally reflected is the light guide plate 1.
1 inside. Further, since the slope S2 forming a pair with the slope S1 is formed to be larger than the vertical direction of the incident surface 11A, the illumination light incident on the light guide plate 11 from the slope S1 is transmitted to the other slope S2. The light enters and is guided into the light guide plate 11 without any leakage. Thereby, in the light guide plate 11, in the region corresponding to the electrode,
The amount of illumination light increases as compared with the related art, and accordingly, the amount of emitted light increases at a portion corresponding to this electrode.

On the other hand, in the inner area AR2 following the area AR1, the illumination light is emitted from the slopes S1 and S1 of the protrusion.
2 (FIG. 5), is refracted by the slopes S1 and S2, and is guided into the light guide plate 11 in two directions according to the directions of the slopes S1 and S2.

At this time, since these inclined surfaces S1 and S2 are formed substantially perpendicular to the exit surface, the illumination light incident on the light guide plate 11 can be transmitted from the entrance surface 11A only in a direction parallel to the exit surface. Thus, the directivity toward the inside of the light guide plate 11 changes. At this time, the size of the slope S1 facing the center of the effective light emitting area AR is formed to be larger than the size of the remaining slope S2 when viewed from the vertical direction of the incident surface 11A which is the main direction of arrival of the illumination light. Many components of the illumination light propagate inside the light guide plate 11 toward the side surface closer to the slope S1. As a result, in the light guide plate 11, the light quantity of the illumination light on both sides, which is inherently insufficient, is compensated for, so that the light quantity emitted at the portion corresponding to the electrode also increases.

On the other hand, in the central portion of the effective light emitting area AR, the illuminating light (FIGS. 3 and 4)
The projection 12A is bent by the slopes S1 and S2 of the projection 12A, and is guided into the light guide plate 11 in two directions according to the directions of the slopes S1 and S2.

Also at this time, since these slopes S1 and S2 are formed substantially perpendicular to the exit surface, the illumination light incident on the light guide plate 11 is incident on the entrance surface 11A only in the direction parallel to the exit surface. Therefore, the directivity toward the inside of the light guide plate 11 changes. Further, when the slopes S1 and S2 are equal in size when viewed from the vertical direction of the incident surface 11A, the light is distributed to both side surfaces of the light guide plate 11 with the same amount of light. As a result, the light amount in the area AR2 reduced by being distributed to the side surface side is compensated for, and the illumination light is emitted with a uniform light amount as the entire light guide plate 11.

As one of the methods for distributing the illuminating light in the effective light emitting area to both sides and thus efficiently irradiating the illuminating light on both sides, a method of roughening the entire incident surface can be considered. However, according to this method, even in a direction perpendicular to the emission surface, the directivity of the illumination light incident from the incidence surface changes, so that in the effective light emitting region,
The amount of illumination light emitted from the emission surface is increased by the amount of the illumination light distributed to both side surfaces. However, in this embodiment, since the directivity of the illumination light can be changed only in a direction parallel to the emission surface, it is possible to effectively avoid such an increase in the amount of emitted light in the effective light emitting region. It is possible to effectively reduce a local decrease in light quantity.

According to the above configuration, the projections 12A, 12B, having the pair of slopes S1 and S2 substantially perpendicular to the exit surface,
12C is repeatedly formed on the incident surface 11A, and in the central region AR3 of the effective light emitting region AR, both slopes S1 and S2
Is formed in the same size, and in the area AR2 adjacent to the vicinity of the electrode, the slope S1 facing inward is formed large, and in the area AR1 near the electrode, the other slope S2 is formed large, so that the area AR1 near the electrode is formed. Thus, less illumination light can be efficiently guided into the inside of the light guide plate 11, and in the subsequent area AR2, the illumination light can be distributed to the area AR1 near the electrode. In the central area AR3, the areas AR2 on both sides of the central area AR3.
Illumination light can be distributed to the This makes up for the insufficient light quantity of the illumination light near the incident surface side and both side faces of the light guide plate 11 and can reduce a local decrease in the light output light quantity.

In the above embodiment, the case where the incident surface is divided into three regions has been described. However, the present invention is not limited to this, and may be divided into two regions as necessary. That is, for example, the central area AR3 and the side area A
A combination of two types of regions with R1, and furthermore, a projection of the central region AR3 is formed in the same shape as the projections 12B of both side regions AR2, and a combination of two types of this and the side region AR1 is adopted. Even so, the effect of reducing a local decrease in the amount of emitted light can be obtained.

However, in order to obtain the effect of further reducing the local decrease in the amount of emitted light, it is desirable to divide the incident surface into three types of regions as in the above-described embodiment.

Further, in the above-described embodiment, the slope of the slope S2 is set so that the illumination light incident on the slope S1 substantially parallel to the incident surface is not reflected by the slope S2 in the side surface area AR1. I mentioned the case,
The present invention is not limited to this.
The inclination of the slope S2 may be set so that the light is totally reflected at the position 2.

In the above-described embodiment, in the inner area AR2 following the side area AR1, the inclination of the slope S2 is adjusted so that the illumination light arriving from the vertical direction also enters the slope S2 facing the side. Although the case of setting is described, the present invention is not limited to this, and the inclined surface S2 is further inclined with respect to the incident surface 11A so that the illumination light from the vertical direction is inclined.
The same effect can be obtained even if the light is hardly incident on the light source 2.

Further, in the above-described embodiment, the case where the slopes S1 and S2 are directly connected to form a projection having a triangular cross section has been described, but the present invention is not limited to this.
The slopes S1 and S2 may be connected by a curved surface. Similarly, adjacent protrusions may be connected by a curved surface.

In the above embodiment, the case where the light scattering surface is formed on the light guide plate by printing has been described. However, the present invention is not limited to this, and the light is formed by partially forming the light scattering surface on the textured surface (textured surface). A scattering surface may be 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. However, the present invention is not limited to this, and the reflector and the reflection sheet may be, for example, a sheet material on which silver is deposited. The present invention can be widely applied to a case where a regular reflection member made of a material such as the above is used.

Further, in the above embodiment, the light guide plate 11
A case has been described in which a so-called single-sided prism sheet is laminated on the exit surface of the present invention, but the present invention is not limited to this, and a so-called double-sided prism sheet may be used.

In the above embodiment, the light guide plate 11
Although the case where the light scattering surface is selectively formed on the slope side of the light guide plate is described, the present invention is not limited to this, and the case where the light scattering surface is selectively or entirely formed on the output surface of the light guide plate, or The present invention can be widely applied to a configuration in which a light scattering surface is selectively or entirely formed on both a surface and an inclined surface.

Further, in the above-described embodiment, the case where the illumination light is incident from one end surface 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 surface. It can be widely applied to light source devices.

Further, in the above-described embodiment, the case where the present invention is applied to a side light type surface light source device using a 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 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.

[0062]

As described above, according to the present invention, one slope having a pair of slopes substantially perpendicular to the emission surface and facing the center of the light source is formed smaller than the other slope. By repeatedly forming the formed projections at both ends in the longitudinal direction of the incident surface, it is possible to reduce a partial decrease in the amount of emitted light near the incident surface formed corresponding to a region separated from the light emitting region of the light source. it can.

[Brief description of the drawings]

FIG. 1 is a plan view showing an incident surface side of a light guide plate in 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 an enlarged plan view showing a central area AR3 of FIG. 1;

FIG. 4 is a characteristic curve diagram for describing a protrusion formed in a central area AR3 of FIG. 3;

FIG. 5 is an enlarged plan view showing an outer area AR2 of a central area AR3 in FIG. 3;

FIG. 6 is an enlarged plan view showing an outer region AR1 of FIG. 5;

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 a slope of the light guide plate 2. FIG.

[Explanation of symbols]

1, 10 Sidelight type surface light source device 2, 11 Light guide plate 2A, 11A Incident surface 3 Primary light source 8 Fluorescent lamp 8A, 8B Electrode 12A, 12B, 12C Projection S1, S2 Slope

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-254618 (JP, A) JP-A-63-33702 (JP, A) JP-A-6-250024 (JP, A) JP-A 9-205 113907 (JP, A) Japanese Utility Model 62-74282 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13357 F21V 8/00 G02B 6/00

Claims (5)

(57) [Claims] 1. A light guide plate configured to receive illumination light emitted from a predetermined light source from an incident surface and emit the illumination light from the emission surface, comprising: a pair of light guide plates substantially perpendicular to the emission surface. A projection formed by connecting the slopes, wherein one of the pair of slopes whose vertical direction faces the center side of the light source is formed to be smaller than the other slope, A light guide plate, which is repeatedly formed at both end portions along the incident surface. 2. A pair of slopes that are substantially perpendicular to the emission surface are connected, and one of the pair of slopes whose vertical direction faces the center of the light source is the other slope. 2. The projections, which are formed larger than the projections, are repeatedly formed along the incident surface at portions closer to the center in the longitudinal direction than both end portions in the longitudinal direction of the incident surface. 3. Light guide plate. 3. A projection formed by connecting a pair of slopes substantially perpendicular to the emission surface, and having a pair of slopes formed to have substantially the same size, a protrusion in the longitudinal center of the incidence surface. The light guide plate according to claim 1, wherein the light guide plate is repeatedly formed on the portion along the incident surface. 4. A sidelight-type surface light source device that irradiates illumination light emitted from a predetermined light source from an end face of a plate-like member and emits the illumination light from an emission surface of the plate-like member. The illumination light is emitted from a predetermined light emitting area, and the plate-shaped member is formed by connecting a pair of slopes substantially perpendicular to the emission surface, and a vertical direction of the pair of slopes is the light source. A sidelight type wherein one of the slopes facing the center side of the projection is formed so as to be smaller than the other slope, and is repeatedly formed along the end face at both ends in the longitudinal direction of the end face. Surface light source device. 5. A liquid crystal display device, wherein a liquid crystal display panel is illuminated by the side light type surface light source device according to claim 4.