JP2002055235A - Light transmission plate, surface light source device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a protrusion and a reflection sheet from being scuffed in a light transmissions plate, a surface light source and a display device by applying the surface light source constructed in such a way that illumination light is emitted in a frontal direction of a light-emitting surface without especially arranging a sheet member to correct directivity of outgoing light. SOLUTION: A plurality of protrusions 1, respectively having at least a pair of intersecting slopes with edge lines formed so as to get closer to a surface 15B opposite to the light-emitting surface as the pair of the slopes get away from the light source 14A, and a plurality of projecting parts 20 having a nearly flat part formed on at least an end of each part are formed on the surface 15B opposite to the light-emitting surface.

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 surface light source device, and a display device. For example, the present invention relates to a light guide plate, a surface light source device, and a display device. The present invention can be applied to a surface light source device and the like configured so as to be able to be used. The present invention provides a projection having at least one pair of slopes that form a ridge line and intersect with a surface facing an emission surface as the distance from the light source increases, and a projection having a substantially flat portion formed at least at the tip. By forming a plurality of sheets on the surface opposite to the emission surface, the illumination light can be emitted in the front direction of the emission surface without particularly arranging a sheet material for correcting the directivity of the emission light, and protrusions and reflections are formed. The sheet can be prevented from being damaged.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, a bright screen is displayed by illuminating a liquid crystal display panel using a surface light source device.

In such a surface light source device, the illumination light of the primary light source, which enters from the side surface of the light guide plate, which is a flat transparent member, is repeatedly reflected by the light exit surface and the rear surface of the light guide plate to cause the inside of the light guide plate to pass through. While propagating, the illuminating light incident on the emission surface of the light guide plate at an angle equal to or less than the critical angle is emitted from the emission surface, whereby the entire emission surface functions as a light emitting surface to constitute a surface light source. .

A surface light source device according to such a basic principle is
Although various measures are taken to promote the emission of illumination light on the emission surface, back surface, etc. of the light guide plate, of the illumination light propagating inside the light guide plate, the illumination light incident on the emission surface at an angle equal to or less than the critical angle is emitted. Since the light is emitted from the surface, the directivity of the illumination light emitted from the light guide plate is inclined in the propagation direction of the illumination light inside the light guide plate from the front direction of the emission surface.

[0005] Therefore, in the surface light source device according to this type of structure, a predetermined sheet material is arranged on the exit surface of the light guide plate,
The directivity of the illumination light is corrected by the sheet material.

[0006]

The use of a sheet material for correcting the directivity of the illumination light emitted from the light guide plate not only increases the number of parts but also complicates the entire apparatus.
It is not preferable in that it hinders the reduction in the thickness of the device, and it is disadvantageous in terms of cost. Therefore, a surface light source device capable of reducing the number of sheets to be used has been desired.

The inventor of the present invention has conducted intensive studies to solve this problem. As a result, even if various sheet materials for correcting the directivity of the illumination light are not arranged on the light exit surface of the light guide plate, the light emission is not required. A structure of a light guide plate capable of emitting illumination light in the front direction of the surface was found, and this was proposed earlier (Japanese Patent Application No. 11-3897).
No. 7).

Here, the light guide plate according to the previous proposal has a first reflection surface and a second reflection surface as shown in FIG. 11, and a valley is formed inside by the pair of reflection surfaces. A plurality of projections to be formed on the surface facing the emission surface of the light guide plate,
The internal propagating light that reaches the projection while propagating in the light guide plate is reflected on one of the first and second reflecting surfaces and then continuously reflected on the other reflecting surface. The internal propagation light is emitted from the light guide plate by each reflection.

In the light guide plate having such a structure, the illumination emitted from the light guide plate is adjusted by adjusting the degree of inclination of the first and second reflection surfaces of the individual projections and the arrangement of the plurality of projection groups. The light emission direction can be controlled, and this direction can be easily set to the front direction of the light emission surface of the light guide plate. Regardless of whether a linear light source such as a cold-cathode tube is used as a primary light source or a point light source such as a light-emitting diode, a surface light source with sufficient luminance compared to the related art is used. It was possible to configure.

However, in this type of surface light source device, the illumination light leaking from the light guide plate is re-entered into the light guide plate by the reflection member disposed on the back surface side of the light guide plate, and the illumination light is effectively used. If a large number of such projections are arranged on the back surface of the light guide plate, the reflection member may be damaged by the projections. Conversely, the projection may be damaged by such a reflection member, and furthermore, the reflection member may be locally adhered to the rear surface due to the progress of the damage of the projection. Such a phenomenon deteriorates the directivity and the like of the emitted light, and further degrades the quality of the light emitting surface.

The present invention has been made in view of the above points, and is configured so that illumination light can be emitted in the front direction of the emission surface without particularly arranging a sheet material for correcting the directivity of emitted light. Therefore, it is an object of the invention to propose a light guide plate, a surface light source device, and a display device that can prevent projections, a reflection sheet from being damaged, and the like.

[0012]

According to the first aspect of the present invention, there is provided a light guide plate for emitting illumination light from a predetermined light source from an emission surface while propagating inside the light source. In the surface facing the emission surface, a projection having at least one pair of inclined surfaces forming a ridge line so as to approach the surface facing the emission surface as the distance from the light source increases, and a substantially flat portion is formed at least at the tip And a plurality of convex portions formed by the process.

[0013] According to the second aspect of the present invention, the first aspect is provided.
In the configuration described above, the projection is formed in a quadrangular pyramid shape.

According to the third aspect of the present invention, the first aspect is provided.
Alternatively, in the configuration of the second aspect, the protrusion is a ridge extending in a predetermined direction.

[0015] In the invention of claim 4, claim 1 is provided.
Alternatively, in the configuration of claim 2, the convex portion is a trapezoidal projection that is elongated in the propagation direction of the illumination light.

In the invention of claim 5, claim 1 is
Alternatively, in the configuration according to claim 2, the projection has at least one pair of slopes that form a ridge line and intersect so as to approach a surface facing the emission surface as the distance from the light source increases.

According to a sixth aspect of the present invention, a surface light source device is constituted by using the light guide plate according to the first, second, third, fourth or fifth aspect.

According to the invention of claim 7, in claim 6,
A liquid crystal display panel is illuminated by the surface light source device described in (1) to constitute a display device.

According to the configuration of the first aspect, in the light guide plate configured to emit the illumination light incident from the predetermined light source from the emission surface while propagating through the inside, the surface facing the emission surface has: At least one ridge is formed so as to approach the surface facing the emission surface as the distance from the light source increases.
Since a plurality of protrusions having a pair of slopes are formed, the illumination light propagating inside the light guide plate can be emitted in the direction of the emission surface by two reflections on the pair of slopes. Also, by forming a plurality of projections formed by forming at least a substantially flat portion at the front end together with the projection, it is possible to weaken the contact of the member arranged on this surface with the projection, or The projections can be prevented from hitting the projections, so that the illumination light can be emitted in the front direction of the emission surface without particularly arranging a sheet material for correcting the directivity of the emission light. The sheet can be prevented from being damaged.

According to a fifth aspect of the present invention, in the configuration of the first or second aspect, at least one of the protruding portions forms a ridge line so as to approach a surface facing the emission surface as the distance from the light source increases. By having the pair of slopes, it is possible to emit the illumination light propagating inside the light guide plate in the front direction of the emission surface also by this convex portion.

According to the structure of claim 6, a surface light source device having desired characteristics can be obtained by preventing the reflection sheet or the like from being damaged. According to the structure of claim 7, this surface light source device can be obtained. A liquid crystal display device using the light source device can be obtained.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that some parts of the drawings are exaggerated for ease of understanding.

(1) First Embodiment (1-1) Configuration of First Embodiment FIG. 2 is an exploded perspective view showing a liquid crystal display device according to a first embodiment of the present invention. . The liquid crystal display device 11 is applied to, for example, a personal computer, and includes a surface light source device 1.
3, the liquid crystal display panel 12 is illuminated from the back to display an image.

Here, the surface light source device 13 has a reflection sheet 16 disposed on a back surface of a light guide plate 15 on which a primary light source 14 of a linear light source is disposed on a side surface.
The light diffusion sheet 17 is disposed on the A side. In this embodiment, the primary light source 14 is the fluorescent lamp 1
4A is formed by surrounding it with a reflector 14B.

The reflection sheet 16 is a white sheet material, and reflects the illumination light leaking from the back surface 15B of the light guide plate 15 and re-enters the light guide plate 15, thereby improving the utilization efficiency of the illumination light.

The light diffusion sheet 17 is a sheet material that weakly scatters and transmits the illuminating light emitted from the emission surface 15A of the light guide plate 15. The scattering of the illuminating light makes a micro-reflector and the like described later inconspicuous. Furthermore, when abnormal light emission occurs due to a scratch or the like of the light guide plate 15, the abnormal light emission is made inconspicuous. Further, even in the case where the luminance of the light emitting surface is not sufficiently uniform, the uneven brightness of the illumination light emitted from the light exit surface 15A of the light guide plate 15 is reduced, and the light exit surface 15A of the light guide plate 15 is further reduced. By disposing the light diffusion sheet 17 on the side, the light exit surface 15 of the light guide plate 15
A is prevented from being damaged.

The light guide plate 15 is made of, for example, acrylic (PMMA).
Resin), a flat transparent member formed by injection molding a transparent resin such as a cycloolefin-based polymer. The light guide plate 15 receives illumination light emitted from the primary light source 14 from an incident surface 15C assigned to one side surface, and propagates the illumination light inside. The light guide plate 15 has an emission surface 15A formed by a flat surface, while
Many projections having the same shape (hereinafter, referred to as micro-reflectors) are arranged on 5B, and illumination light propagating inside is emitted toward the liquid crystal display panel 12 by the micro-reflectors. Thereby, the surface light source device 13 is configured to constitute a surface light source having the emission surface 15A of the light guide plate 15 as a light emitting surface. The light guide plate 15 has a rear surface 15B.
And the emission surface 15A are formed in parallel.

FIG. 3 is a side view of the micro-reflector (FIG. 3A) and a plan view of the micro-reflector viewed from the back side of the light guide plate 15 (FIG. 3B).
The micro-reflector 19 reflects the illumination light L propagating inside the light guide plate 15 mainly through two reflections to the emission surface 15A.
A pair of slopes 19A and 19B emitting in the front direction of
The pair of slopes 19C and 19D formed so as not to block the illumination light L directed to these slopes 19A and 19B are directly connected to each other, and are formed by quadrangular pyramid-shaped protrusions protruding toward the back surface 15B of the light guide plate 15. Is done.

That is, in the micro reflector 19, the slopes 19A and 19B are formed such that the apex angle at which the slopes 19A and 19B intersect forms a predetermined angle. Further, the slopes 19A and 19B are each formed by a flat surface and directly connected so as to form a V-shaped valley whose depth gradually decreases. Slope 19A and 19
B is formed such that it passes through the ridge line 19E which is such a connection portion and is plane-symmetric with respect to a plane perpendicular to the emission surface 15A. Thereby, the micro-reflector 19 forms the ridge line 19E so as to approach the back surface 15B facing the emission surface 15A as the distance from the light source increases, and the slopes 19A, 1
9B.

The micro-reflector 19 has a back surface 15B
As viewed from the side, the illumination light L arriving toward the valley within a predetermined angle range around the direction of the ridgeline 19E is reflected by the slope 19A (or 19B), and then the other slope 19B remaining. (Or 19A) and exit surface 1
The light is emitted in the front direction of 5A.

On the other hand, the slopes 19C and 19D are formed in a plane-symmetrical manner by the flat surfaces similarly to the slopes 19A and 19B, and the ridge line 19E formed by the slopes 19A and 19B and the slopes 19C and 19D. Is formed so as to be substantially straight in the plan view seen from the back surface 15B side. The slopes 19C and 19D are reflected by the slopes 19A and 19B,
The illumination light L directed to the front direction of 5A is applied to the slopes 19A and 19A.
9B so that it does not block at the stage before entering, or slope 1
The illumination light L reflected by the slope 9C or the slope 19D is formed with a predetermined inclination so as to enter the slope 19A or 19B at a suitable angle.

The light guide plate 15 is, as shown in FIG.
In the plan view seen from the 5B side, the back surface 15B is set such that the extension of the ridge line 19E is substantially orthogonal to the incident surface 15C, and the shallow side of the valley is the side away from the light source.
The direction of the micro-reflector 19 is set in accordance with each of the parts.

The light guide plate 15 has a micro-reflector 19 formed so small that it is difficult for the light guide plate 15 to be perceived by the naked eye when viewed from the exit surface 15A side. Further, in the light guide plate 15, each micro reflector 19 is formed in the same size,
The micro-reflectors 19 are arranged such that the number of the micro-reflectors 19 in a unit area increases as the distance from the vicinity of the incident surface 15C increases. As a result, the light guide plate 15 increases the function of emitting the illumination light by the micro-reflector 19 by increasing the number of the micro-reflectors 19 in a portion where the amount of the illumination light propagating inside is reduced, thereby increasing the emission surface 15A. The illumination light is emitted with a substantially uniform light amount over the entire surface of the device.

Further, the light guide plate 15 is provided with micro reflectors 19 arranged irregularly, whereby illumination light is supplied to the liquid crystal display panel 12 so that moire fringes do not occur on the display screen.

Further, in the light guide plate 15, on the back surface 15B, in addition to these micro-reflectors 19, a convex portion 20 having a substantially flat portion formed at the tip is formed. Here, the projection 20 is a narrow ridge having a rectangular cross-section, as shown in a partial cross-section by the symbol A, together with the peripheral members, and is formed from the entrance surface 15C in a direction substantially orthogonal to the entrance surface 15C. It extends to the opposite end surface and is formed repeatedly at a predetermined pitch along the incident surface 15C. Thus, even when the projections 20 are arranged on the light guide plate 15 in this manner, they hardly affect the directivity and the like of the illumination light emitted from the light guide plate 15.

Further, the projection 20 is formed so that the height thereof is higher than the height of the micro-reflector 19, so that even when the light guide plate 15 is directly mounted on the reflection sheet 16, the reflection sheet to the micro-reflector 19 is formed. 16
Has been made to prevent contact. From the viewpoint of preventing the reflection sheet 16 from contacting the projections 19, the pitch of the projections 20 is selected.

(1-2) Operation of First Embodiment In the above configuration, in the liquid crystal display device 11 (FIG. 2), the liquid crystal display panel 12 is illuminated by the illumination light supplied from the surface light source device 13. Thus, the image formed on the liquid crystal display panel 12 can be viewed by the user.

As described above, the illumination light for illuminating the liquid crystal display panel 12 is supplied to the surface light source device 13 by the primary light source 14.
Is emitted from the incident surface 15C to the light guide plate 15, and is repeatedly reflected between the output surface 15A and the back surface 15B and propagates inside the light guide plate 15. In the course of this propagation,
The light path is bent by being partially reflected by the micro-reflector 19 formed on the back surface 15B, and the light exit surface 15A
Is emitted from.

That is, the illumination light propagating inside the light guide plate 15 enters the micro-reflector 19 in the process,
In FIG. 3 (FIG. 3), the illumination light incident on the pair of slopes 19A and 19B within a predetermined angle range centered on the ridgeline 19E formed by the slopes 19A and 19B when viewed from the emission surface 15A is continuous on the slopes 19A and 19B. Reflected on the slopes 19A so as to be directed toward the front of the emission surface 15A.
And the optical path is bent at 19B. Thereby, in the surface light source device 13, a surface light source having the emission surface 15 </ b> A as a light-emitting surface is configured, the degree of inclination of the first and second reflection surfaces 19 </ b> A and 19 </ b> B in each microreflector 19, and the plurality of formed microreflectors 19. By adjusting the arrangement or the like, the direction in which the emitted light leaves the office, the directivity, and the like can be controlled.

In the surface light source device 13 (FIG. 1), the slopes 19A and 19B of the micro-reflector 19 are thus adjusted.
The valley formed by the slopes 19A and 19B so that the illumination light is reflected to bend the optical path of the illumination light so that the extension of the ridge line 19E formed by the slopes 19A and 19B is substantially orthogonal to the incident surface 15C. The micro-reflector 19 is set so that the shallow side of the
Is set, the illumination light arriving from the incident surface 15C side can be efficiently incident on each micro-reflector 19 within the range in which the optical path can be bent in this way, and thereby the illumination light can be efficiently emitted. It is possible to configure a surface light source that emits light and has sufficient luminance.

In a portion where the amount of illumination light propagating away from the entrance surface 15C is small, the number of micro-reflectors 19 is increased by that amount, so that approximately equal light intensity distribution is obtained in each portion of the exit surface 15A. Illumination light can be emitted, and thereby illumination light can be emitted with a uniform light amount distribution.

In the light guide plate 15, together with the micro reflector 19, the micro reflector 19
Since the higher projections 20 are repeatedly formed, even if the projections 20 are directly mounted on the reflection sheet 16, the projections 20 prevent the micro reflector 19 from coming into contact with the reflection sheet 16. Thereby, the surface light source device 13
Thus, it is possible to prevent the micro-reflector 19 from being scratched, the reflecting sheet 16 from being scratched, and the reflective sheet 16 from being partially adhered.

In the light guide plate 15, the illumination light incident from the incident surface 15C is emitted from the emission surface 15A by the micro-reflector 19 while being propagated inside.
The projections 20 arranged on the light guide plate 15 are formed by ridges having a narrow width as viewed from the incident surface 15C so as to extend in the internal propagation direction of the illumination light. In the light source device 13, even if the protrusions 20 are arranged on the light guide plate 15, the characteristics of the emitted light can be hardly affected.

(1-3) Effects of the First Embodiment According to the above configuration, the micro-reflector 19 which is a projection having a pair of slopes 19A and 19B, and a substantially flat portion is formed at least at the tip. By forming a plurality of convex portions 20 on the back surface, the illumination light can be emitted in the front direction of the emission surface without particularly arranging a sheet material for correcting the directivity of the emission light. In addition, the reflection sheet can be prevented from being damaged.

Further, since the convex portion 20 is formed by a ridge extending in a direction substantially perpendicular to the incident surface 15C, even if the convex portion 20 is arranged, the characteristics of the emitted light are hardly affected. be able to.

(2) Second Embodiment FIG. 4 shows a surface light source device applied to a liquid crystal display device according to a second embodiment of the present invention in comparison with FIG.
It is a top view which shows a light guide plate with a light source. In the liquid crystal display device according to this embodiment, a light source is constituted by a light emitting diode 24 which is a point light source.
The light guide plate 25 is configured to correspond to the light source of No. 4. This liquid crystal display device has such a light source and the light guide plate 2.
The liquid crystal display device 11 according to the first embodiment, except that the liquid crystal display panel 12 or the like is applied to the configuration of No. 5 and is made small as a whole and applied to, for example, a mobile phone or the like. Is configured the same as

Similarly to the light guide plate 15 according to the first embodiment, the light guide plate 25 is formed with a flat surface on the exit surface 25A side, and the micro reflector 19 is disposed on the back surface 25B. Here, the light guide plate 25 is formed in a shape in which one corner is obliquely cut off by a plane perpendicular to the emission surface 25A, and the obliquely cut surface is formed by the incident surface 25A.
Set to C. Thus, in the light guide plate 25, the light emitting diode 24 is arranged on the incident surface 25C, and the illumination light propagates inside so as to spread from the corner.

The light guide plate 25 is arranged so that each micro-reflector 19 faces the incident surface 25C so as to correspond to such propagation of illumination light. Further, the micro-reflectors 19 are arranged according to the amount of the internally propagated light, so that even when the point light sources are arranged at the corners as described above, the emission surface 25A can emit light with uniform brightness as a whole. ing.

Further, in the light guide plate 25, in addition to the micro-reflector 19, a convex portion 30 is disposed on the back surface 25B.
Here, the protrusions 30 are protrusions having a flat surface formed at the tip, and are arranged irregularly on the back surface 25B and at a substantially uniform density on the entire back surface. The convex portion 30 has a trapezoidal shape elongated in the propagation direction of the illumination light, as shown in a partially cross-sectional view by the reference numeral B and shown in an enlarged manner together with peripheral members,
The height is formed by a protrusion higher than the micro reflector 19. Thus, the light guide plate 25 prevents the tip of the micro-reflector 19 from directly contacting the reflection sheet 16 and prevents the reflection sheet 16 from being damaged.

More specifically, the projection 30 is a projection having a rectangular shape whose cross section as viewed from the reflection sheet 16 side is elongated. The extending direction of the long side surface 30 A is on the light emitting diode 24 side. They are arranged with a predetermined tendency according to each part of the back surface 25B. As a result, the convex portion 30 is
When viewed from 5B, the short side surface 30B and the side surface opposite to the short side surface are arranged so as to cross the optical path of the internal propagation light from the light emitting diode 24 almost vertically.

Thus, even if the light guide plate 25 increases the flat portion of the convex portion 30 to some extent so that the end of the micro-reflector 19 does not come into contact with the reflection sheet 16 even after long-term use, the light guide plate 25 can maintain the characteristics of the emitted light. It is designed to have little effect.

Thus, in this embodiment,
When the primary light source is constituted by a point light source, the convex portion is formed in an elongated trapezoidal shape so as to prevent projections, damage to the reflection sheet, and the like.

(3) Third Embodiment FIG. 5 shows a surface light source device applied to a liquid crystal display device according to a third embodiment of the present invention in comparison with FIG.
It is a top view showing a light guide plate. The liquid crystal display device according to the present embodiment has the same configuration as the liquid crystal display device according to the second embodiment except that a light guide plate 35 shown in FIG. You.

Here, in the light guide plate 35, similarly to the light guide plate 25, the exit surface 35A and the back surface 35B are formed in a parallel plate shape, and the entrance surface 35C is formed at one corner.
Is formed, and the light emitting diode 24 is arranged on the incident surface 35C. Also, the micro reflector 1 is provided on the back surface 35B.
9 are arranged, and a projection 40 is arranged instead of the projection 30.

Here, the convex portion 40 is a projection having a flat surface formed at the tip as shown partially enlarged by a reference character C and shown with the peripheral members, and irregularly formed on the rear surface 35B. , And are arranged with substantially uniform density on the entire back surface. Thus, the light guide plate 25 prevents the tip of the micro-reflector 19 from directly contacting the reflection sheet 16 and prevents the reflection sheet 16 from being damaged.

The projections 40 are provided on the reflection sheet 1.
6 In addition to preventing scratches, etc., the micro-reflector 1
As in the case of No. 9, a function of emitting the internal propagation light in the front direction of the emission surface 35A is added. That is, the convex portion 40 is formed as shown in FIG.
6A shows a bottom view, FIG. 6B shows a side view corresponding to FIG. 6A, and FIG. 6C shows a side view corresponding to FIG. 6B. Similarly, as the distance from the light source increases, the ridge line 40 approaches the back surface 35B.
And a pair of slopes 40A and 40B intersecting each other to form the light emitting diode 2
4 direction. Further, the protrusion 40
The inclination of the pair of slopes 40A and 40B with respect to the back surface 35B is the corresponding slope 19 of the micro-reflector 19.
A and 19B are set so as to have substantially the same inclination. As shown in FIG. 7, as shown in FIG.
The light is emitted from the emission surface 35A with substantially the same directivity as that of No. 9.

The convex portion 40 is formed to have a certain area of a flat portion 40F at the tip so that the tip of the micro-reflector 19 does not contact the reflection sheet 16 even after long-term use. The slopes 40A and 40B are formed by surfaces larger than the pair of slopes 19A and 19B of the micro reflector 19.

Even if the convex portion 40 has a larger shape than the micro-reflector 19, it does not greatly affect the propagation of the illumination light inside the light guide plate.
In addition, a pair of slopes 40C and 40C that are inclined with respect to the optical path of the internally propagated light as viewed from the back surface 35B and rise vertically from the back surface 35B are light sources so as not to block the incidence of the internally propagated light on the slopes 40A and 40B. Formed on the side.

Thus, in this embodiment,
By arranging the convex portion having the function of emitting the illumination light similarly to the projection formed on the back surface, the illumination light can be emitted in the front direction of the emission surface without particularly arranging a sheet material for correcting the directivity of the emitted light. The projections and the reflection sheet are prevented from being damaged.

(4) Other Embodiments In the above-described first embodiment, the case where the protruding portions are formed by the ridges having a rectangular cross section has been described. However, the present invention is not limited to this. May be formed so that a substantially flat portion is formed at the tip. For example, as shown in FIG. 8, when a convex portion is formed by a ridge having an arc-shaped cross section, various convex shapes may be used. By forming the protrusions by the ridges, the same effect as in the above-described first embodiment can be obtained.

In the first embodiment described above,
Although the case where the convex portion by the ridge is formed so as to extend from the incident surface to the side of the opposing surface has been described, the present invention is not limited to this, so that it is interrupted halfway from the incident surface to the opposing surface. Alternatively, a ridge may be formed so as to form a projection so as to start from the middle, or to start in the middle and to be interrupted in the middle.

In the above-described first embodiment,
Although the case where the projection is formed by the ridge when the primary light source is constituted by the linear light source has been described, the present invention is not limited to this, and can be widely applied to the case where the primary light source is constituted by a point light source. For example, when a point light source using a light emitting diode is arranged at a corner as shown in FIG. 4, the micro-reflector 19 is omitted, and as shown in FIG. It is conceivable to arrange the parts.

On the contrary, in the above-described second and third embodiments, when the light emitting diode which is a point light source is applied to the primary light source, and when the point light source is arranged at the corner, Although the case where the projection is formed by the projection has been described, the present invention is not limited to this, and when the primary light source is configured by the linear light source, and further when the point light source is arranged at a portion other than the corner, the projection is formed. Thus, the same effects as in the above-described embodiment can be obtained.

In the above-described embodiment, the case where the convex portion is higher than the height of the micro-reflector 19 has been described. However, the present invention is not limited to this, and even when the convex portion is lower than the height of the micro-reflector 19, By arranging the convex portions, it is possible to reduce the contact of the reflection sheet with the tip of the micro-reflector 19. Accordingly, in the present invention, a convex portion lower than the micro reflector 19 may be arranged. Even in this case, the micro reflector 19 and the reflection sheet can be less damaged. In the selection of the height of such a convex portion, a thin surface light source device is required, and an appropriate value is selected according to a method of holding the light guide plate and the reflection sheet, a use environment of the display device, and the like. It is required that the height of the micro-reflector 19 be at least １ ／ of the height of the micro-reflector 19 to reduce the damage to the reflection sheet, and more preferably 以上 or more. By forming a convex portion by the height of the reflective sheet, the reflective sheet can be prevented from being damaged to a practically sufficient degree when applied to a portable device.

In the above embodiment, the case where the illumination light of the primary light source is incident on the light guide plate from the side surface of the light guide plate is described. However, the present invention is not limited to this, and a cross section is shown in FIG. As described above, the present invention can be widely applied to a case where a light source is formed on a back surface side or an emission surface side, or the like, in which a light source is formed on a back surface side or an emission surface side.

Further, in the above-described embodiment, the case where the projection is formed in the shape of a quadrangular pyramid has been described. However, the present invention is not limited to this, and the point is that the illumination light is mainly reflected by the pair of slopes mainly twice. An effect similar to that of the above-described embodiment can be obtained by correcting the emission direction and forming projections so as to guide illumination light propagating inside the light guide plate to these slopes without blocking.

Further, in the above-described embodiment, the case where a pair of slopes are directly connected to form a projection has been described. However, the present invention is not limited to this. A pair of slopes may be connected by a curved surface to form a projection. In this case, the projections are arranged such that the direction in which the ridge line is extended by the curved surface is the direction of the incident surface at each part of the light guide plate when viewed from the emission surface side.

Further, in the above-described embodiment, the case where the pair of slopes are formed by flat surfaces has been described. However, the present invention is not limited to this. The slope may be formed by a curved surface in consideration of the above.

In the above-described embodiment, the case where the amount of emitted light is made uniform by adjusting the number of micro-reflectors has been described. However, the present invention is not limited to this, and instead of adjusting the number, or adjusting the number. In addition, the light amount distribution may be made uniform by adjusting the size and shape of the micro reflector.

In the above embodiment, the case where the light guide plate is formed with a constant thickness has been described. However, the present invention is not limited to this, and can be widely applied to the case where the light guide plate is formed with a wedge-shaped cross section. it can.

Further, in the above-described embodiment, in addition to the large number of projections which reflect the internally propagated light toward the emission surface mainly by twice reflection, the projections for reducing the contact of the reflection member with the projections are provided. Although the specific light guide plate, the surface light source device, and the configuration of the display device are described in accordance with the gist of the present invention in which the light guide plate is disposed on the back surface, the present invention relates to the configuration according to the above-described embodiment. The present invention is not limited to this, and various techniques related to the surface light source device can be applied in a range that does not impair the effects of the present invention, or in order to further enhance the effects of the present invention.

[0072]

As described above, according to the present invention, a projection having at least one pair of slopes which forms a ridge line so as to approach a surface facing the emission surface as the distance from the incidence surface increases, and at least a tip end substantially. By forming a plurality of convex portions having flat portions on the surface facing the emission surface, the illumination light can be directed in the front direction of the emission surface without particularly disposing a sheet material for correcting the directivity of the emission light. The projections and the reflection sheet can be prevented from being damaged.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a light guide plate of a surface light source device applied to a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a liquid crystal display device to which the surface light source device according to the light guide plate of FIG. 1 is applied.

FIG. 3 is a side view and a plan view illustrating a micro reflector of the light guide plate of FIG. 1;

FIG. 4 is a sectional view showing a light guide plate of a surface light source device applied to a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a light guide plate of a surface light source device applied to a liquid crystal display device according to a third embodiment of the present invention.

FIG. 6 is a bottom view showing a projection applied to the light guide plate of FIG. 5;
It is a side view.

FIG. 7 is a perspective view for explaining a convex portion applied to the light guide plate of FIG. 5;

FIG. 8 is a cross-sectional view showing a projection formed by a ridge of a light guide plate according to another embodiment.

FIG. 9 is a plan view showing a projection formed by a ridge applied to a light guide plate according to another embodiment.

FIG. 10 is a cross-sectional view showing a configuration in which a primary light source is arranged on the back surface side.

FIG. 11 is a perspective view for explaining a projection of an example according to Japanese Patent Application No. 11-38977.

[Explanation of symbols]

11 ... liquid crystal display device, 12 ... liquid crystal display panel, 13
... surface light source device, 14A ... fluorescent lamp, 15, 25,
35 ... light guide plate, 19 ... micro reflector, 19
A to 19D, 40A, 40B ... slope, 20, 30, 4
0: convex portion, 24: light emitting diode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F21Y 103: 00 G02F 1/1335 530

Claims (7)

[Claims] 1. A light guide plate configured to emit illumination light from a predetermined light source from an emission surface while propagating through the inside of the light guide plate. A plurality of projections having at least one pair of inclined surfaces forming a ridge line so as to approach a surface facing the surface and a plurality of convex portions having at least a substantially flat portion formed at the end are formed. Light guide plate. 2. The light guide plate according to claim 1, wherein the projection has a quadrangular pyramid shape. 3. The light guide plate according to claim 1, wherein the projection is a ridge extending in a predetermined direction. 4. The light guide plate according to claim 1, wherein the projection is a trapezoidal projection elongated in the propagation direction of the illumination light. 5. The projection according to claim 1, wherein the projection has at least one pair of slopes that form a ridge line and intersect so as to approach a surface facing the emission surface as the distance from the light source increases. 3. The light guide plate according to claim 1. 6. The first, second, third and fourth aspects of the present invention.
A surface light source device using the light guide plate according to claim 5. 7. A display device for illuminating a liquid crystal display panel with the surface light source device according to claim 6.