JPH10253960A - Side light type surface light source device, and light control member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization efficiency of illuminating light, and to make it possible to emit a high quality illuminating light, by respectively and repeatedly forming projection parts having a pair of slopes on the outgoing surface and the same kind of projection parts on the planar member side of a light control member. SOLUTION: A light scattering light guiding plate 12 is constituted so that minute projection parts are formed repeatedly on the outgoing surface 12C parallel to an incident surface 12A. A pair of slopes 12E, 12F prolonged in the direction orthogonally intersecting the incident surface 12A are connected directly, and respective projection parts are formed into a sectional triangular shape. A prism sheet 13 is constituted so that the minute projection parts are formed repeatedly on the surface of the outgoing surface 12C side in the direction orthogonally intersecting the incident surface 12A, and a prism surface is formed. These minute projection parts are constituted so that a pair of slopes 13A, 13B prolonging parallel to the incident surface 12A of the light diffusion light transmission plate 12 are connected directly, and respective projection parts are formed into the sectional triangular shape. Thus, the directivity of the outgoing light is corrected in the front direction of the outgoing surface 12C within the surface parallel to the incident surface 12 and within the surface orthogonally intersecting the incident surface 12A.

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 formed such that the thickness of a plate-like member becomes thinner as the distance from the incident surface increases. is there. According to the present invention, the projections are repeatedly formed on the emission surface of the plate member, and the same type of projections are repeatedly formed on the plate member side of the light control member. By improving the efficiency of use of illumination light, high-quality illumination light can be emitted.

[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 transmitted through a light scattering light guide plate. From the end face of the light guide plate. Furthermore, the sidelight type surface light source device bends this illumination light,
Light is emitted from the plane of the light guide plate toward the liquid crystal display panel, whereby the overall shape can be reduced.

[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. 14 is an exploded perspective view showing an example of the latter sidelight type surface light source device 1, and FIG. 15 is a cross-sectional view of FIG. 14 taken along line AA. In this side light type surface light source device 1, a primary light source 3 is arranged on a side of a light scattering light guide plate 2, and a reflection sheet 4, a light scattering light guide plate 2,
It is formed by sequentially laminating prism sheets 5 and 6 which are light control members.

The primary light source 3 is formed by surrounding a fluorescent lamp 7 composed of a cold-cathode tube with a reflector 8, and from the opening side of the reflector 8 to the end surface (hereinafter referred to as an incident surface) 2 A of the light-scattering light guide plate 2. Illumination light enters. Here the reflector 8
Is formed of, for example, a sheet material that specularly or irregularly reflects incident light.

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 light scattering light guide plate 2. The light is incident on the light-scattering light guide plate 2, thereby improving the utilization efficiency of the illumination light.

The light-scattering light-guiding plate 2 is a light-guiding plate having a wedge-shaped cross section. For example, light-transmitting fine particles having a different refractive index from the matrix are dispersed and mixed in a matrix made of, for example, polymethyl methacrylate (PMMA). Formed. Thereby, the light scattering light guide plate 2 receives the illumination light L from the incident surface 2A,
When the illumination sheet L is scattered by the translucent fine particles, and when the reflection sheet 4 made of the irregular reflection member is applied, the reflection sheet 4 partially reflects irregularly, and the reflection sheet 4 side plane (hereinafter referred to as a slope) 2B. The illumination light L propagates while being repeatedly reflected between the prism sheet 5 and the flat surface on the prism sheet 5 side (hereinafter referred to as an emission surface) 2C.

In this propagation, the illumination light L is reflected by the inclined surface 2B, the incidence angle with respect to the exit surface 2C is reduced, and a component that is less than the critical angle with respect to the exit surface 2C is emitted from the exit surface 2C. . The illumination light L1 emitted from the emission surface 2C is
The illumination light L is scattered by the light-transmitting fine particles inside the light-scattering light-guiding plate 2, and is emitted by the scattered light by being diffusely reflected by the reflection sheet 4 and propagated. However, the illumination light L1 is reflected and propagates on an inclined surface 2B formed to be inclined in the propagation direction with respect to the emission surface 2C, and a component having a critical angle or less is emitted, so that the main emission direction has a wedge shape. It is formed to be inclined toward the tip. That is, the outgoing light L1 from the light scattering light guide plate 2 has directivity, whereby the sidelight type surface light source device 1 has directivity.

The prism sheets 6 and 7 are arranged to correct the directivity of the light scattering and light guiding plate 2. That is, the prism sheets 5 and 6 are formed of a translucent sheet material such as polycarbonate, and the prism surface is formed on the surface opposite to the side facing the light scattering light guide plate 2. The prism surface is formed by repeating projections having a triangular cross section extending substantially parallel to one direction, and the prism sheet 5 on the light scattering light guide plate 2 side is configured such that the projections extend substantially parallel to the incident surface 2A. In addition, the prism sheet 6 has the projection
A is arranged to extend in a direction substantially orthogonal to A.

As a result, the prism sheets 5 and 6 correct the main emission direction of the emitted light to the front direction of the emission surface 2C on the slope of the triangular projection. 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, 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 scattering light guide plate is formed with a substantially uniform plate thickness. It has been done.

[0012]

In such a sidelight type surface light source device 1, it is required to efficiently emit the illumination light L incident from the incident surface 2A. In addition, it is required to emit light with high quality while effectively avoiding the occurrence of moire and the like.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and a sidelight type surface light source device capable of improving the use efficiency of illumination light and emitting high-quality illumination light as compared with the related art. It is intended to propose.

[0014]

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 and emitted from the plate-like member. The present invention is applied to a sidelight type surface light source device that emits light from a surface. In the sidelight type surface light source device, a light control member is arranged on an emission surface of the plate-shaped member, and a pair of slopes extending in a direction substantially perpendicular to the end surface are formed on the emission surface of the plate-shaped member. The protruding portions are repeatedly formed in a direction substantially parallel to the end face. Further, a convex portion having a pair of inclined surfaces extending in a direction substantially parallel to the end surface is repeatedly formed on a surface of the light control member facing the plate member in a direction substantially orthogonal to the end surface.

At this time, in the plate-like member and the light control member, convex portions are formed at a repetition pitch of 100 [μm] or less.

[0016] Further, in these cases, in the light control member, the angle formed by the slope closer to the end face of the pair of slopes forming the convex portion and the normal to the emission face is equal to the end face. The slopes of the pair of slopes are made different from each other so as to be smaller than the angle formed by the slope farther from the side and the normal to the emission surface.

[0017] More technically, it is preferable that the main illumination light emitted from the emission surface be directed to the inclined surface relatively far from the end surface forming the pair on the inclined surface closer to the end surface. The angle of this slope is selected to guide. Further, the angle of the pair of slopes is selected so that the illumination light coming from the near slope is totally reflected and emitted almost in the normal direction on the far slope.

Further, in these cases, or in place of these, the direction in which the slope extends in the light control member is set to 10
Within the range of degrees, the inclination direction is inclined from the direction parallel to the end surface. In the plate-like member, the repetition direction of the slope is inclined in the range of 10 degrees from the direction in which the slope of the light control member extends.

In these cases, in the plate-like member,
The angle on the plate-like member side formed by the pair of slopes is 50 to 13
Set to a range of 0 degrees.

In these cases, a regular reflection layer for regularly reflecting the illumination light is provided on the surface of the plate-shaped member opposite to the emission surface.

Further, the present invention is applied to a sheet-like light control member having a prism surface formed on at least one side, which is applied to these side light type surface light source devices and the like, and is inclined with respect to a plane along the light control member. In this prism surface, a pair of inclined surfaces are repeatedly formed to have different inclinations, and the extending direction of the inclined surfaces is set to be inclined with respect to the end surface. I do.

A light control member is arranged on the light emitting surface of the plate member,
If a convex portion having a pair of inclined surfaces extending in a direction substantially parallel to the end surface is repeatedly formed on the light control member in a direction substantially perpendicular to the end surface, the illumination emitted obliquely to the tip end side of the plate-shaped member. Light can be guided in the front direction of the emission surface. Further, if a projection having a pair of slopes is repeatedly formed on the emission surface of the plate-like member in a direction substantially parallel to the end surface, the repetition of the pair of slopes allows emission light in a plane parallel to the entrance surface to be formed. Directivity can be corrected in the front direction of the emission surface. Thus, the illumination light can be guided in almost all directions in the front direction of the emission surface by only the plate-shaped member and one light control member,
One light control member having a conventional configuration can be omitted. At this time, in the light control member, by forming this convex portion on the emission surface side of the plate member, it is possible to make the illumination light incident on the light control member at a large incident angle to the inclined surface at a small incident angle. it can. Therefore, the illumination light that has been totally reflected and returned to the plate-like member in the past can be efficiently emitted, and the utilization efficiency of the illumination light can be improved accordingly.

In order to efficiently emit the illumination light in this manner, 100 [μm] or less, more preferably 50 [μm] or less.
m] If the protrusions are formed with the following repetition pitch, the repetition of the protrusions can be made inconspicuous, and the minute pulsation of the emitted light amount due to the repetition and the moire due to the repetition pitch of the liquid crystal cell can be reduced. it can.

Further, in these cases, the angle formed by the pair of slopes of the light control member, which is closer to the end face, and the normal line of the exit face, makes the relative angle to the end face. By making the angle smaller than the angle formed by the slope farthest from the side and the normal line of the emission surface, the illumination light is emitted from a larger area when viewed from the emission side, and the amount of emitted light Can be reduced, and moire can be reduced.

It is more technically preferable that the main component of the illuminating light emitted from the plate member is closer to the slope farther away than the slope closer to the end face. The angle of the slope on the far side is selected, and the angle of the slope on the far side is selected so that the illuminating light coming from the near slope is totally reflected and emitted almost in the normal direction. For example, the illumination light emitted from the plate member can be guided into the light control member without waste, and the guided illumination light can be emitted in the front direction without waste.

Further, in these cases, or alternatively, in the light control member, the direction of extension of the slope is
In the range of degrees, tilt from the direction parallel to the end surface. In the plate-like member, if the direction of repetition of the slope is tilted in the range of 10 degrees from the direction in which the slope of the light control member extends, the repetition pitch of the projections is When it is large, or when higher-quality outgoing light is required, moire can be reduced.

In these cases, in the plate-like member,
The angle on the plate-like member side formed by the pair of slopes is 50 to 13
If the angle is set to 0 degree, the directivity of the illumination light can be corrected in a practically sufficient range.

In these cases, if a regular reflection layer for regularly reflecting the illumination light is disposed on the surface of the plate-shaped member opposite to the emission surface, the illumination light leaking from the plate-shaped member can be efficiently applied to the plate-shaped member. By returning, it is possible to improve the use efficiency of the illumination light.

Further, in the light control member applied to the side light type surface light source device, the convex portion is formed so that the inclination is different with respect to the pair of inclined surfaces constituting the convex portion, and the extending direction of the inclined surface is defined as follows. If it is set to be inclined with respect to the end face, it is possible to improve the utilization efficiency of the illumination light when incorporated into the sidelight type surface light source device,
Moire can be reduced.

[0030]

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 sidelight type surface light source device according to an embodiment of the present invention in comparison with FIG.
FIG. 2 is a cross-sectional view of the sidelight type surface light source device 10 taken along line BB. The side light type surface light source device 10 includes a primary light source 3
Are arranged, and a reflection sheet 11, a light scattering light guide plate 12, and a prism sheet 13 serving as a light control member are sequentially laminated. In this side light type surface light source device 10,
The same configuration as the side light type surface light source device 1 of FIG.
Corresponding reference numerals are attached and duplicate descriptions are omitted.

Here, the side light type surface light source device 10
In the above, a sheet material made of a regular reflection member on which silver is deposited is applied to the reflection sheet 11 so as to exhibit a high reflectance with respect to the illumination light L.
The illumination light leaking from 2B is efficiently returned to the inside of the light scattering light guide plate 12, and the utilization efficiency of the illumination light is improved.

The light-scattering light guide plate 12 is formed, for example, in a matrix made of polymethyl methacrylate (PMMA).
Transparent fine particles having different refractive indices from this are uniformly dispersed and mixed to form a wedge-shaped cross-sectional shape. As a result, the light scattering light guide plate 12 scatters the illumination light L incident from the incident surface 12A with the light-transmitting fine particles, while the inclined surface 12B and the exit surface 1 are scattered.
2C and is repeatedly reflected and propagated, and at this time, a part is emitted from the emission surface 12C.

Further, in the light-scattering light guide plate 12, fine projections are repeatedly formed on the exit surface 2C in parallel with the incident surface 12A as shown by partially enlarging the incident surface 12A side by an arrow C. . Here, this minute projection has a pair of slopes 12E and 12F extending in a direction orthogonal to the incident surface 12A, and in this embodiment, the pair of slopes 12E and 12F.
Are directly connected so that each convex portion is formed in a triangular cross section. Thereby, the light scattering light guide plate 12
As shown in a cross-sectional view in FIG.
The illumination light is refracted by E and 12F, and the directivity of the emitted light is corrected in the direction parallel to the incident surface 12A in the front direction of the emission surface 12C.

Further, in this embodiment, in the light scattering light guide plate 12, a pair of slopes 12E and 12F are formed to have the same inclination with respect to the emission surface, and the angle α1 formed by the slopes 12E and 12F is selected to be about 60 degrees. It has been made. The apex angle α1 can be appropriately selected in the range of 50 ° to 130 ° to obtain practical characteristics, but is preferably in the range of 60 ° to 110 °.

Further, in the light-scattering light guide plate 12, these minute projections are formed, for example, by the sidelight type surface light source device 1.
0 is 1 / compared to the pixel period of the liquid crystal display panel to which
It is formed with a repetition pitch W1 of 50 [μm] smaller than 4 or more.

The prism sheet 13 includes the light scattering light guide plate 12
A single-sided prism sheet having a prism surface formed on the side is applied. Here, the prism surface is formed by curing an acrylic ultraviolet curable resin or the like in a predetermined shape on the surface thereof based on transparent PET.

In the prism sheet 13, as shown in a partially enlarged side view by an arrow D, minute projections are repeatedly formed on the surface on the exit surface 12 C side in a direction orthogonal to the incident surface 12 A. Forms a prism surface. Here, this minute projection is formed on the incident surface 12 of the light scattering light guide plate 12.
A has a pair of slopes 13A, 13B extending parallel to A,
In this embodiment, the pair of slopes 13A and 13B are directly connected so that each projection is formed in a triangular cross section.

Thus, the prism sheet 13 is formed such that similar projections are repeatedly formed in a direction orthogonal to the direction in which the projections of the light-scattering light-guiding plate 12 are repeated. As shown, the illumination light L emitted from the light scattering light guide plate 12 while being inclined in the wedge-shaped tip direction.
1 is guided inside by the slope 13A on the incident surface 12A side,
The light is reflected by the slope 13B forming a pair with the slope 13A and is emitted in the front direction of the emission surface 12C. This allows the prism sheet 13 to move in a plane orthogonal to the incident surface 12A.
The directivity of the emitted light is corrected in the front direction of the emission surface 12C.

Further, in this embodiment, the prism sheet 13 is formed such that the pair of slopes 13A and 13B are formed to have the same inclination with respect to the exit surface, and the angle α2 formed by the slopes 13A and 13B is selected to be about 66 degrees. Has been made. The apex angle α2 can be appropriately selected in the range of 30 ° to 70 ° to obtain practical characteristics, but is preferably 50 ° to 70 °, more preferably 60 ° to 70 °. .

Further, in the prism sheet 13, these minute projections have, for example, one pixel in comparison with the pixel period of the liquid crystal display panel to which the sidelight type surface light source device 10 is applied.
It is formed with a repetition pitch W2 of 50 [μm] smaller than / 4.

In the above configuration, the illumination light L emitted from the fluorescent lamp 7 (FIGS. 1 and 2) is directly or after being reflected by the reflector 8 and then from the entrance surface 12A to the inside of the light scattering light guide plate 12. While being incident and being scattered by the light-transmitting fine particles, the light is repeatedly reflected between the inclined surface 12B and the emission surface 12C and propagates inside the light scattering light guide plate 12. At this time, each time the illumination light L is reflected by the slope 12B,
The incident angle with respect to C decreases, and a component equal to or smaller than the critical angle with respect to the exit surface 12C is emitted from the exit surface 12C. At this time, the illumination light leaking from the inclined surface 12B of the light scattering light guide plate 12 is
The light is reflected by the reflection sheet 11, which is a regular reflection member disposed on the slope side, and is efficiently returned to the inside of the light-scattering light guide plate 2, whereby the light is efficiently emitted from the emission surface 12C.

When the illumination light L is emitted from the emission surface 12C in this manner, a component having a critical angle or less is emitted from the illumination light propagating from the incidence surface 12A toward the wedge-shaped tip, so that the illumination light L has a flat surface. As shown in FIG. 5, the light is emitted with the directivity inclined toward the wedge-shaped tip, and with the spread directivity in the direction along the incident surface 12A, as shown in FIG. In FIG. 5, the incident surface 12A
The intensity of the illumination light emitted in each direction from the light-scattering light-guiding plate 12 was detected by setting the angle in the plane along the direction X to Xθ and the angle in the plane perpendicular to this plane to Yθ.

On the other hand, in this embodiment, as shown in FIG. 6 in comparison with FIG. 5, the incident light is formed in parallel with the incident surface by the inclined surfaces 12E and 12F of the repeatedly formed convex portions (FIG. 3). In a plane parallel to the plane 12A, the illumination light emitted so as to spread outward is emitted with its directivity corrected so as to face inward. Thus, the directivity of the outgoing light can be corrected in the front direction of the outgoing surface 12C in a plane parallel to the incident surface 12A without using the prism sheet 6 (FIG. 15) having the conventional configuration. Therefore, the prism sheet 6 can be omitted, and the utilization efficiency of the illumination light can be improved accordingly.

Incidentally, in the conventional side light type surface light source device (FIG. 15), the illumination light component reflected on the incident surface of the prism sheet 5 is multiple-reflected between the prism sheet 5 and the light scattering light guide plate 2. Therefore, when the directivity of the emitted light is measured as shown in FIG. 7, a peak of the luminance level may be generated in a direction other than the front direction of the emission surface as shown in FIG. all right.
In this embodiment, such a component can be efficiently guided in the front direction of the emission surface 12C, thereby improving the directivity and the efficiency of using the illumination light.

The illumination light L emitted from the emission surface 12C in this manner passes through the subsequent prism sheet 13 and illuminates a liquid crystal panel and the like disposed on the front surface of the prism sheet 13. At this time, the illumination light L is emitted from the emission surface 12C toward the wedge-shaped tip due to the repeated formation of the projections formed by the slopes 13A and 13B parallel to the incident surface 12A. , 13B, the light enters the prism sheet 13 via the inclined surface 13A facing the incident surface 12A side, and is guided to the other inclined surface 13B. Here, the illumination light L is totally reflected by the inclined surface 13B, and as shown in FIG. 8 in comparison with FIG. 6, in a plane orthogonal to the incident surface 12A, the directivity of the emitted light is in the front direction of the emission surface 12C. Will be corrected.

As described above, the illumination light incident on the prism sheet 13 is incident through the inclined surface 13A, so that the side of the light-scattering light-guiding plate 2 facing the exit surface is made flat. In the mold surface light source device (FIG. 15), the component that has been totally reflected on the incident surface of the prism sheet 6 and returned to the light-scattering light guide plate 2 is also positively guided into the prism sheet 13 and exits. It is emitted in the front direction of 12C. Thereby, the utilization efficiency of the illumination light is improved accordingly.

Further, since a large number of projections are formed on the exit surface 12C of the light scattering light guide plate 12, the light scattering light guide plate 1
Sticking of the prism sheet to 2 is also effectively avoided.

In correcting the directivity in this way,
Emission surface 12C of light scattering light guide plate 12 and prism sheet 1
Since a large number of convex portions are repeatedly formed on the prism surface of No. 3, microscopic pulsations of the luminance level occur in the repetition direction of the convex portions when viewed microscopically. If the pixel pitch of the liquid crystal display panel is close to the pulsation, so-called moiré occurs, and the quality of the displayed image is significantly deteriorated. That is, in this case, the quality of the emitted light is reduced as viewed from the sidelight type surface light source device.

On the other hand, in this embodiment,
More than 1/4 smaller than the pixel period of the liquid crystal display panel,
Since the convex portions are repeated at the repetition pitches W1 and W2 of 50 [μm], the pulsation of the luminance level can be reduced to the repetition pitch sufficiently separated from the pixel pitch, and the occurrence of moiré correspondingly Can be effectively avoided. Also, the repetition of the slope can be made inconspicuous.

Further, in this embodiment, a pair of slopes 12E, 12E forming a projection in the light scattering light guide plate 12 are provided.
F is formed at an equal inclination with respect to the exit surface, and the slope 1
Since the angle α1 formed by 2E and 12F is selected to be about 60 degrees, a sufficiently sharp directivity can be obtained for practical use.

According to the above structure, a triangular-shaped convex portion having a pair of inclined surfaces 12E and 12F is repeatedly formed on the exit surface 12C of the light-scattering light guide plate 12 in parallel with the incident surface. By repeatedly forming the same convex portion on the surface on the side of the light scattering light guide plate 12 in the direction orthogonal to the repeating direction of the convex portion in the light scattering light guide plate 12, the configuration is simpler than in the related art and efficiently. Illumination light can be emitted.

In addition, at this time, these convex portions are 50 μm smaller than the pixel cycle of the liquid crystal display panel by 1/4 or more.
m], it is possible to effectively avoid the occurrence of moire and emit high-quality illumination light by that amount. Further, the repetition of the convex portion can be made inconspicuous.

In the light-scattering light guide plate 12, a pair of slopes 12E and 12F forming a convex portion are formed at an equal inclination with respect to the exit surface, and the angle α1 formed by the slopes 12E and 12F is selected to be about 60 degrees. As a result, practically sufficiently sharp directivity can be obtained.

(2) Second Embodiment In a sidelight type surface light source device according to this embodiment, a prism sheet 14 shown in FIG. 9 is applied instead of the prism sheet 13 described above with reference to FIG. The side light type surface light source device according to the second embodiment has the same configuration as the side light type surface light source device 10 described above with reference to FIG. 1 except for the configuration of the prism sheet 13. Therefore, duplicate description will be omitted.

That is, in this side light type surface light source device, the prism sheet 14 has a minute convex portion on the light exit surface 12C side similarly to the first embodiment,
A is repeatedly formed in a direction orthogonal to A, thereby forming a prism surface. Further, the prism sheet 14 is formed such that the convex portion is formed by a pair of inclined surfaces 14A and 14B extending in parallel with the incident surface 12A of the light scattering light guide plate 12, and the inclined surfaces 14A and 14B are set to have different inclinations. It has been done.

That is, the slope 14A on the incident surface 12A side is
The main illuminating light emitted obliquely to the wedge-shaped tip side from the light scattering light guide plate 12 is incident at a small incident angle, and the incident illuminating light is guided to the inclined surface 14B forming a pair without waste. It is formed with a small inclination β1 with respect to the normal L1 of the surface 12C. On the other hand, another slope 1
4B is such that the illumination light incident from the slope 14A is totally reflected in the front direction of the emission surface 12C.
It is formed by a slope β2 larger than that of 4A.

That is, as shown by the characteristic curve in FIG. 6, the illumination light emitted from the light-scattering light guide plate 12 has a direction inclined approximately 70 degrees toward the wedge-shaped tip from the vertical direction, and is substantially emitted. The light is emitted within a range of 20 degrees to 85 degrees from the vertical direction. Therefore, after the illumination light in the main emission direction enters from the slope 14A on the incident surface 12A side, the other slope 1
The relationship between the inclinations β1 and β2 is set based on the refractive index n of the prism sheet 14 so that the light is reflected in the front direction of the emission surface 12C at 4A.

Further, on the premise of this relationship, the inclinations β1 and β2 are set so that the illumination light emitted in the range of 20 to 85 degrees from the vertical direction is emitted along the same path as the illumination light in the main emission direction. Is set. In this embodiment, the angles β1 and β2 are set to 5.5 degrees and 35 degrees, respectively.

That is, as shown in FIG. 10, when the slopes 13A and 13B are set to have the same inclination as in the configuration according to the first embodiment, the light is scattered by total reflection on the slope 13A on the incident surface 12A side. An illumination light component LA returned to the light guide plate 12 is generated. Also, the slope 13 on the incident surface 12A side
Even with the illumination light incident from A, a component LB directly emitted without being totally reflected by other slopes also occurs. A component that is reflected and emitted a plurality of times by the repeatedly formed projections also occurs.

From these facts, in FIG.
And H, in the sidelight type surface light source device, a peak such as a so-called side lobe occurs in the main emission direction.

However, if the angles β1 and β2 are set to 5.5 degrees and 35 degrees, respectively, as in this embodiment, the slopes 13A and 13B are thus compared with FIG. 8 as shown in FIG. And the illumination light component LB, etc., which is directly emitted, is incident on the inclined surface 14A and enters the other inclined surface 1A.
4B, or can pass through the slope 14A and exit directly in the frontal direction. Also, the illumination light component LA returning to the inside of the light scattering light guide plate 12 can be reduced.

FIG. 12 shows the result of observing the state of correction by the prism sheet 14 using a light-scattering light guide plate having an emission surface formed by a flat surface, in comparison with FIG.

Further, in this manner, the area of the corresponding slope 14B can be increased as compared with the slope on the incident surface 12A side when viewed from the liquid crystal panel side. Thereby, minute pulsation of the emitted light amount due to repetition of the minute projections is reduced, and moire is reduced accordingly. That is, the moire may be detected by the configuration according to the first embodiment by being visually perceived. It is also detected when the repetition pitch of the projections is increased. However, if the minute pulsation of the emitted light amount is reduced, it is possible to make it difficult to detect moire even in such a case.

According to the configuration shown in FIG. 9, in addition to the first configuration, the slope forming the projection of the prism sheet is
By setting the incident surface side to a small inclination and the corresponding inclined surface to a large inclination with respect to the normal line of the emission surface, the utilization efficiency of the illumination light is improved accordingly, and high-quality illumination light is emitted. be able to.

(3) Third Embodiment FIG. 13 is a plan view showing a sidelight type surface light source device 30 according to a third embodiment. In the sidelight type surface light source device 30, the configuration of the reflector 8 and the like is the same as that of the sidelight type surface light source device described above with reference to FIG. 9 except that the configurations of the light scattering light guide plate 31 and the prism sheet 32 are different. , And redundant description of these configurations will be omitted.

In this side-light type surface light source device 30, the light scattering / light guide plate 31 has a projecting portion having a triangular cross section repeatedly formed on the exit surface, and a pair of slopes forming the projecting portion is orthogonal to the incident surface 31A. In such a manner as to be inclined by a predetermined angle θA from the direction in which the image is formed.

Further, the side light type surface light source device 30
In the prism sheet 32, the same protrusions as the protrusions according to the second embodiment are repeatedly formed on the surface on the side of the light-scattering light guide plate 31, and a pair of slopes forming the protrusions is The scattered light guide plate 31 extends in a direction orthogonal to the direction in which the slope extends. In FIG. 13, the direction in which these slopes extend is indicated by a straight line.

In this embodiment, the light scattering light guide plate 3
1 and the prism sheet 32, the convex portions are repeatedly formed at a repetition pitch of 50 [μm], and the inclination angle θA
Is set in a range of 10 degrees or less, more preferably in a range of 5 degrees or less.

That is, in the side light type surface light source device, if the extending directions of the slopes are arranged perpendicularly and parallel to the incident surface 12A, the illumination light whose luminance level slightly pulsates has the same pulsation direction. Each pixel of the liquid crystal panel forms an opening regularly so as to overlap with each other, thereby easily causing moiré. On the other hand, when the repetition direction of the convex portions (the direction in which the slope of each convex portion extends) is inclined with respect to the pixel arrangement direction of the liquid crystal display panel, the degree of occurrence of moire can be reduced.

However, if the inclination is increased, the directivity of the illumination light emitted from the sidelight type surface light source device is disturbed.

As a result, in this embodiment, the repetition direction of the convex portion is inclined within a range of 10 degrees or less, thereby effectively avoiding deterioration of directivity and making it difficult to detect moire sufficiently.

According to the configuration shown in FIG. 13, in addition to the configuration according to the second embodiment, in the light-scattering light guide plate 31 and the prism sheet 32, while maintaining the repetition direction of the projections orthogonal to each other, By inclining these repetition directions within a range of 10 degrees or less, the same effect as that according to the second embodiment can be obtained, and in addition, deterioration of directivity of emitted light can be effectively avoided. Thus, moiré can be made even more difficult to perceive.

(4) Other Embodiments In the first to third embodiments described above, 50
Although the case where a large number of convex portions are formed on the light scattering light guide plate and the prism sheet with the repetition pitch of [μm] has been described, the present invention is not limited to this. Thus, the moire can be made difficult to perceive to a practically sufficient degree.

Further, in the third embodiment described above, the light scattering light guide plate and the prism sheet hold the repetition direction of the projections orthogonal to each other and tilt the repetition direction of the projection by the angle θA. However, the present invention is not limited to this, and the orthogonal relationship may be disturbed by a small angle. That is, the prism sheet is tilted in a range of 10 degrees or less with respect to a direction parallel to the incident surface of the light scattering light guide plate, and the light scattering light guide plate is tilted in a range of 10 degrees or less with respect to the repetition direction of the convex portion in the prism sheet. By inclining the repetition direction of the convex portions, it is possible to obtain practically sufficient directivity and to reduce the occurrence of moire.

In the above-described first to third embodiments, the case where the slopes are directly connected to form the projections in a triangular cross section has been described. However, the present invention is not limited to this, and the present invention is not limited to this. A pair of slopes may be connected by a simple curve or the like, or adjacent convex portions may be connected.

Further, in the third embodiment described above, a case is described in which a pair of slopes are set to have different inclinations in the prism sheet, and the light scattering light guide plate and the prism sheet are inclined in the repetition direction of the projections. However, the present invention is not limited to this, and if sufficient characteristics for practical use can be obtained, the slope may be set to the same inclination and only the repetition direction of the convex portion may be inclined.

Further, in the above-described embodiment, a case has been described in which a prism sheet is formed by curing an acrylic ultraviolet curable resin or the like in a predetermined shape on the surface thereof based on transparent PET. Not limited to this,
The prism sheet may be formed using a light-transmitting material such as polycarbonate (PC) and polymethyl methacrylate (PMMA). Further, the present invention can be widely applied to a case where a so-called prism body composed of a sheet-shaped or plate-shaped light control member having no flexibility is used instead of a prism sheet made of a resin material having flexibility.

Further, in the above-described first to third embodiments, the case where the reflection sheet, the light scattering light guide plate, and the prism sheet are laminated has been described. However, the present invention is not limited to this, and the illumination light is diffused. When the light diffusion sheet is disposed between the prism sheet and the light scattering light guide plate or on the upper surface of the prism sheet, the illumination light is directly diffused to the other surface of the prism sheet (the surface from which the illumination light is emitted). The present invention can be widely applied to forming a light diffusion surface. With this configuration, the directivity can be corrected by the light diffusion sheet and the light diffusion surface.

In the above-described first to third embodiments, the case where the reflection sheet is formed by the regular reflection member made of the sheet material on which silver is vapor-deposited has been described. However, the present invention is not limited to this. And a diffuse reflection member such as white PET or the like.

Further, in the above-described first to third embodiments, the case where the light-scattering light-guiding plate is formed by mixing light-transmitting fine particles has been described. However, the present invention is not limited to this, and the present invention is not limited thereto. The present invention can be widely applied to a case where light scattering guide plates are formed by mixing fine particles.

In the first to third embodiments, the case where the present invention is applied to the side light type surface light source device using the light scattering light guide plate which scatters the illumination light inside has been described. The present invention is not limited to this, and can be widely applied to a sidelight type surface light source device in which a light guide plate is formed by a transparent member having a wedge-shaped cross section. In the case of using such a transparent member, a diffusion pattern is formed by matting, printing, or the like on the surface facing the emission surface. However, it can be widely applied to any case.

Further, in the above-described first to third embodiments, the case where the present invention is applied to a side light type surface light source device using a light scattering light guide plate made of a plate-like member having a wedge-shaped cross section will be described. However, the present invention is not limited to this, and can be widely applied to a sidelight type surface light source device in which a light guide plate is formed by a flat plate-shaped member.

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.

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 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.

[0087]

As described above, according to the present invention, a projecting portion having a pair of inclined surfaces is repeatedly formed on the exit surface of the plate-like member, and the same kind of projecting portion is formed on the plate-like member side of the light control member. Is formed repeatedly, and the shape of the convex portion is selected as necessary, so that the illumination light is efficiently emitted, the utilization efficiency of the illumination light is improved, and the quality of the emitted light due to moire or the like is further improved. Can be reduced.

[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 cross-sectional view of FIG. 1 taken along line BB.

FIG. 3 is a cross-sectional view showing in detail an emission surface of a light-scattering light guide plate in the sidelight type surface light source device of FIG.

FIG. 4 is a sectional view showing a prism sheet in the side light type surface light source device of FIG. 1 in detail.

FIG. 5 is a characteristic curve diagram showing a distribution of illumination light emitted from a conventional light scattering light guide plate for comparison with the side light type surface light source device of FIG.

6 is a characteristic curve diagram showing a distribution of illumination light emitted from a light scattering light guide plate of the side light type surface light source device of FIG.

7 is a characteristic curve diagram showing distribution of illumination light emitted from a light scattering light guide plate of a conventional side light type surface light source device in comparison with FIG.

8 is a characteristic curve diagram showing a distribution of illumination light emitted from a prism sheet in the sidelight type surface light source device of FIG.

FIG. 9 is a sectional view showing a prism sheet applied to a side light type surface light source device according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing an optical path of illumination light in a prism sheet having a conventional configuration in comparison with FIG.

FIG. 11 is a characteristic curve diagram showing directivity in the sidelight type surface light source device of FIG. 9;

12 is a characteristic curve diagram showing directivity in a case where the prism sheet of FIG. 9 is applied to a light-scattering light guide plate of a conventional configuration in comparison with FIG.

FIG. 13 is a sectional view showing a prism sheet applied to a sidelight type surface light source device according to a third embodiment of the present invention.

FIG. 14 is an exploded perspective view showing a conventional sidelight type surface light source device.

FIG. 15 is a cross-sectional view of FIG. 14 cut along line AA.

[Explanation of symbols]

1, 10, 30 Side light type surface light source device 2, 12, 31 Light scattering light guide plate 2A, 12A, 31A Incident surface 5, 6, 13, 14, 32 Prism sheet 12E, 12F, 13AA to 14B Slope

Claims (9)

[Claims] 1. A sidelight type surface light source device for irradiating illumination light emitted from a predetermined light source from an end face of a plate-like member, bending the illumination light and emitting the illumination light from an emission surface of the plate-like member, A light control member is arranged on an emission surface of the plate-like member, and the plate-like member extends on the emission surface in a direction substantially orthogonal to the end surface.
A convex portion having a pair of inclined surfaces is repeatedly formed in a direction substantially parallel to the end surface, and the light control member is a pair of a pair extending on a surface facing the plate-like member in a direction substantially parallel to the end surface. A sidelight type surface light source device, wherein a convex portion having a slope is repeatedly formed in a direction substantially perpendicular to the end surface. 2. The sidelight type surface light source device according to claim 1, wherein the plate-shaped member and the light control member have the protrusions formed at a repetition pitch of 100 [μm] or less. . 3. The projection of the light control member is formed by a slope closer to the end face among a pair of slopes forming the projection, and a normal line of the emission surface. The pair of slopes are formed to have different inclinations so that the formed angle is smaller than the angle formed by the slope relatively far from the end face and the normal to the emission surface. The side light type surface light source device according to claim 1 or 2, wherein the surface light source device is provided. 4. The inclined surface on the side relatively closer to the end surface is provided with the angle so as to guide the main illumination light emitted from the emission surface to the inclined surface relatively far from the end surface. The angle is selected such that the far slope is totally reflected by the illumination light arriving from the near slope and emitted almost in the normal direction. Item 4. A sidelight type surface light source device according to item 3. 5. The light control member is set such that an extending direction of the slope is inclined from a direction parallel to the end surface within a range of 10 degrees or less, and the plate member is configured to repeat the slope. 5. The sidelight according to claim 1, wherein the direction is set within a range of 10 degrees or less with respect to a direction in which a slope of the light control member extends. 6. Mold surface light source device. 6. The light control member, wherein a direction in which the slope extends is set to a range of 10 degrees or less from a direction parallel to the end face, and the plate-like member has a direction in which the slope extends, 5. The sidelight type surface light source device according to claim 1, wherein the light control member is set so as to be orthogonal to a direction in which a slope of the light control member extends. 7. The plate-like member, wherein an angle formed by the pair of slopes is set in a range of 50 to 130 degrees.
The sidelight type surface light source device according to claim 3, 4, 5, or 6. 8. The plate-like member, wherein a regular reflection layer for regularly reflecting the illumination light is disposed on a surface facing the emission surface. The sidelight type surface light source device according to claim 4, claim 5, claim 6, claim 6 or claim 7. 9. A sheet-like light control member having a prism surface formed on at least one surface, wherein the prism surface is inclined at an angle with respect to a plane along the light control member.
A convex portion having a pair of slopes is repeatedly formed, the slopes of the pair of slopes are formed to be different from each other, and a direction in which the slopes extend is set to be inclined with respect to an end face. Light control member.