JP3739067B2 - Sidelight type surface light source device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a sidelight type surface light source device.In placeFor example, the present invention is applied to a side light type surface light source device formed so that the plate thickness of the plate member becomes thinner as the distance from the incident surface increases. The present invention repeatedly forms convex portions on the surface facing the emission surface of the plate-shaped member, and repeatedly forms the same type of convex portions on the plate-shaped member side of the light control member. By selecting the shape of the convex portion, etc., the use efficiency of illumination light is improved, and high-quality illumination light is emitted.
[0002]
[Prior art]
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.
[0003]
That is, in the sidelight type surface light source device, a primary light source composed of a rod-shaped light source is disposed on the side of a plate-like member (that is, composed of a light guide plate), and illumination light emitted from the primary light source is guided from the end face of the light guide plate Is incident on. Further, the sidelight type surface light source device bends the illumination light and emits the light from the plane of the light guide plate toward the liquid crystal display panel, whereby the overall shape can be reduced.
[0004]
Such a sidelight type surface light source device has a type in which a light guide plate is formed with a substantially uniform plate thickness and a type in which the thickness of the light guide plate is gradually reduced as the distance from the primary light source increases. The latter can emit illumination light more efficiently than the former.
[0005]
FIG. 12 is an exploded perspective view showing an example of the latter sidelight type surface light source device 1, and FIG. 13 is a cross-sectional view taken along line AA of FIG. In this sidelight type surface light source device 1, a primary light source 3 is arranged on the side of a light guide plate 2, and a reflection sheet 4, a light guide plate 2, a light diffusion sheet H, and prism sheets 5 and 6 made of a light control member are sequentially stacked. Formed.
[0006]
The primary light source 3 is formed by surrounding a fluorescent lamp 7 made of a cold cathode tube with a reflector 8, and makes illumination light incident on an end surface (hereinafter referred to as an incident surface) 2 </ b> A of the light guide plate 2 from the opening side of the reflector 8. . Here, the reflector 8 is formed of, for example, a sheet material that regularly or irregularly reflects incident light.
[0007]
The reflection sheet 4 is formed of a sheet-like regular reflection member made of metal foil or the like, or a sheet-like irregular reflection member made of white PET film or the like, and reflects the illumination light leaking from the light guide plate 2 and enters the light guide plate 2. This improves the use efficiency of the illumination light.
[0008]
The light guide plate 2 is a plate-like member formed of a transparent member, for example, acrylic (PMMA resin) by injection molding to have a wedge-shaped cross section, and the entire surface of the reflective sheet 4 side plane (hereinafter referred to as the back surface) 2B is matte. A uniform rough surface is formed by the surface treatment. As a result, the light guide plate 2 forms a light diffusion surface on the back surface 2B, and repeatedly reflects between the back surface 2B and the light diffusion sheet 5 side plane (hereinafter referred to as an emission surface) 2C to propagate the illumination light. The illumination light is scattered by the light diffusion surface.
[0009]
During this propagation, every time the illumination light L is reflected by the back surface 2B, the incident angle with respect to the exit surface 2C decreases, and a component having a critical angle or less 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 scattered by the rough surface formed on the back surface 2B, and when an irregular reflection member is applied to the reflection sheet 4, it is diffusely reflected by the reflection sheet 4 and propagated. Thus, the light is emitted by scattered light. However, the illumination light L1 is reflected and propagated on the back 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 inclined to the tip direction. That is, the emitted light L1 from the light guide plate 2 has directivity, and thus the sidelight type surface light source device 1 has directivity.
[0010]
The prism sheets 5 and 6 are arranged to correct the directivity of the light guide plate 2. That is, the prism sheets 5 and 6 are formed of a light-transmitting sheet material such as polycarbonate, and a prism surface is formed on the surface opposite to the side facing the light guide plate 2. This prism surface is formed by repeating a protrusion having a triangular cross section extending substantially in parallel in one direction, and the prism sheet 5 on the light guide plate 2 side has a protrusion extending substantially parallel to the incident surface 2A. The prism sheet 6 is disposed so that the protrusion extends in a direction substantially orthogonal to the incident surface 2A.
[0011]
Thereby, the prism sheets 5 and 6 correct the main emission direction of the emitted light to the front direction of the emission surface 2 </ b> C at the slope of the triangular projection. In addition, as a prism sheet, what is called a double-sided prism sheet of the structure which formed the prism surface on both surfaces may be used. As a result, the side light type surface light source device 1 can emit outgoing light more efficiently in the front direction than a side light type surface light source device of a type in which a light guide plate is formed with a substantially uniform plate thickness. Yes.
[0012]
[Problems to be solved by the invention]
By the way, 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. It is also required to emit high-quality illumination light while effectively avoiding the occurrence of moire or the like.
[0013]
  The present invention has been made in consideration of the above points. A sidelight type surface light source device that can use illumination light more efficiently than the prior art and can emit high-quality illumination light.PlaceIt is what we are going to propose.
[0014]
[Means for Solving the Problems]
  In order to solve this problem, in the first aspect of the present invention, the sidelight which enters the illumination light emitted from the predetermined light source from the end surface of the plate-like member, bends the illumination light and emits it from the emission surface of the plate-like member. Applying to a mold surface light source device, a light control member is disposed on the exit surface of the plate-like member, and the plate-like member extends in a direction substantially orthogonal to the end surface on a surface facing the exit surface side. A pair of convex portions having a pair of slopes are repeatedly formed in a direction substantially parallel to the end surface, and the light control member extends to a surface facing the plate-like member in a direction substantially parallel to the end surface. The convex portions having the inclined surface are repeatedly formed in a direction substantially perpendicular to the end surface, and the plate-like member and the light control member are formed such that the convex portions are formed at a repeating pitch of 100 [μm] or less. InThe light control member transmits the illumination light emitted from the plate-like member through the inclined surface relatively close to the end surface of the pair of inclined surfaces, and guides the illumination light into the end surface. The plate member is reflected by a relatively far slope and emitted, and the angle formed by the pair of slopes is set to an angle greater than 90 degrees and 110 degrees or less..
[0015]
  In the invention of claim 2, on the premise of the configuration of claim 1, in the light control member, of the pair of slopes constituting the convex portion, the slopes on the side relatively close to the end face and the exit surface The slopes of the pair of slopes are made different so that the angle formed by the normal is smaller than the angle formed by the slope far from the end face and the normal of the exit face.
[0016]
  According to a third aspect of the present invention, in the configuration of the second aspect, the main illumination light emitted from the emission surface on the inclined surface relatively close to the end surface is transmitted on the side relatively far from the end surface. Select the angle of this slope so that it leads to the slope, and in this far slope, totally reflect the illumination light coming from the near slope and reflect it in the normal direction. Select the slope angle.
[0017]
  According to a fourth aspect of the present invention, in the configuration of the first, second, or third aspect, in the light control member, the extending direction of the inclined surface is tilted from a direction parallel to the end face within a range of 10 degrees or less. In the plate-like member, the direction in which the slope repeats is tilted within a range of 10 degrees or less from the direction in which the slope of the light control member extends.
[0018]
  According to a fifth aspect of the present invention, in the configuration of the first, second, or third aspect, in the light control member, the direction in which the inclined surface extends is tilted from a direction parallel to the end face within a range of 10 degrees or less. In the plate member, set the direction in which the slope extends to be orthogonal to the direction in which the slope of the light control member extends.The
[0020]
  According to the configuration of the first aspect, the light control member is disposed on the exit surface of the plate-like member, and a convex portion having a pair of inclined surfaces extending in a direction substantially parallel to the end surface is provided on the light control member. If it is repeatedly formed in such a direction, it is possible to guide the illumination light emitted while being inclined toward the front end side of the plate-like member in the front direction of the emission surface. Further, if a convex portion having a pair of inclined surfaces is repeatedly formed in a direction substantially parallel to the end surface on the surface facing the emission surface of the plate-like member, an in-plane parallel to the incident surface is obtained by repeating the pair of inclined surfaces. The directivity of the emitted light at can be corrected in the front direction of the exit surface. Thereby, illumination light can be guide | induced to the front direction of an output surface over almost all directions only with a plate-shaped member and one light control member, and one sheet of conventional light control members can be omitted. At this time, in the light control member, by forming this convex portion on the exit surface side of the plate-like member, the illumination light incident at a large incident angle on the light control member is incident on the inclined surface at a small incident angle. can do. Therefore, it is possible to efficiently emit the illumination light that has been totally reflected and returned to the plate-like member, and the use efficiency of the illumination light can be improved. In addition, when the projections are formed at a repetition pitch of 100 [μm] or less, more preferably 50 [μm] or less for efficiently emitting illumination light in this way, the repetition of the projections can be made inconspicuous. In addition, minute pulsations of the emitted light amount due to this repetition and moire due to the repetition pitch of the liquid crystal cell can be reduced.The light control member transmits the illumination light emitted from the plate-like member through the inclined surface relatively close to the end surface of the pair of inclined surfaces, and guides the illumination light into the inner surface. If the angle formed by the pair of inclined surfaces is set to be greater than 90 degrees and 110 degrees or less, the plate-like member is practically sufficient. The directivity of the illumination light can be corrected within the range.
[0021]
  According to the configuration of claim 2, on the premise of the configuration of claim 1, in the light control member, of the pair of inclined surfaces constituting the convex portion, the inclined surface relatively closer to the end surface, and the exit surface If the slopes of the pair of slopes are different so that the angle formed by the normal is smaller than the angle formed by the slope far from the end surface and the normal of the exit surface When viewed from the emission side, the illumination light is emitted from a larger area, so that the minute pulsation of the emitted light quantity can be reduced and the moire can be reduced.
[0022]
  Further, according to the configuration of claim 3, in the configuration of claim 2, the main illumination light emitted from the exit surface is inclined on the side relatively far from the end surface. The angle of this slope is selected so as to lead to the above, and in this far slope, the illumination light coming from the near slope is totally reflected and reflected in the normal direction. If the angle of the slope is selected, the illumination light emitted from the plate member can be introduced into the light control member without waste, and the introduced illumination light can be emitted without waste in the front direction.
[0023]
  According to the configuration of claim 4, in the configuration of claim 1, claim 2 or claim 3, the light control member is inclined with respect to the direction in which the inclined surface extends from the direction parallel to the end face within a range of 10 degrees or less. In the shape member, if the repeated direction of the inclined surface is tilted within a range of 10 degrees or less from the extending direction of the inclined surface of the light control member, when the repeated pitch of the convex portion is large, the emitted light with higher quality is further generated. Moire can be reduced when required.
[0024]
  Further, according to the configuration of claim 5, in the configuration of claim 1, claim 2 or claim 3, in the light control member, the direction in which the slope extends is tilted from a direction parallel to the end face within a range of 10 degrees or less, In the plate-like member, if the direction in which the slope extends is set to be orthogonal to the direction in which the slope of the light control member extends, even when the convex pitch is large, higher-quality emitted light is required. In some cases, moire can be reduced.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
[0028]
(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. 11, and FIG. 2 shows this sidelight type surface light source device 10 along the line BB. It is sectional drawing cut out and shown. In the sidelight type surface light source device 10, the primary light source 3 is arranged on the side of the light guide plate 12, and the reflection sheet 11, the light guide plate 12, and the prism sheet 13 made up of a light control member are sequentially stacked on a frame (not shown). It is formed by holding. In this side light type surface light source device 10, the same configuration as that of the side light type surface light source device 1 of FIG. 11 is denoted by the corresponding reference numerals, and redundant description is omitted.
[0029]
Here, in the sidelight type surface light source device 10, 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. Thereby, the reflective sheet 11 efficiently returns the illumination light leaking from the back surface 12B of the light guide plate 12 to the inside of the light guide plate 12 and improves the use efficiency of the illumination light.
[0030]
The light guide plate 12 is made of a transparent member made of, for example, a plate-like member injection-molded with acrylic (PMMA resin), and has a wedge-shaped cross section. In the light guide plate 12, the entire exit surface 12C is uniformly formed into a rough surface by mat surface treatment, and a light diffusion surface is formed on the output surface 12C by the rough surface. As a result, the light guide plate 12 propagates the illumination light by repeatedly reflecting between the back surface 12B and the exit surface 12C while scattering the illumination light on the exit surface 12C, and at the time of reflection on the back surface 12B and the exit surface 12C. , A component having a critical angle or less is emitted from the back surface 12B and the emission surface 12C.
[0031]
Further, the light guide plate 12 is repeatedly formed with minute convex portions on the back surface 12B in parallel with the incident surface, as shown partially enlarged by the arrow C on the incident surface 12A side. Here, the minute convex portion has a pair of inclined surfaces 12E and 12F extending in a direction orthogonal to the incident surface 12A. In this embodiment, the pair of inclined surfaces 12E and 12F are directly connected to each other, It is designed to have a triangular shape. Thereby, the light guide plate 12 corrects the directivity of the outgoing light in the front direction of the outgoing surface 12C in a plane parallel to the incident surface 12A.
[0032]
That is, among the illumination light incident on the light guide plate 12, illumination light directed toward the back surface 12B is reflected by the inclined surfaces 12E and 12F formed on the back surface 12B, and thus the front surface in a plane parallel to the incident surface 12A. The component toward the direction increases. Further, as shown in FIG. 3, a part of the illumination light directed toward the back surface 12B is once emitted from the inclined surface 12F to the outside of the light guide plate 12, and then incident again into the light guide plate 12 by the inclined surface 12E. Reflected by the adjacent inclined surface 12F, this becomes a component toward the front direction in a plane parallel to the incident surface 12A, and in the front direction compared to the case where the back surface 12B is configured as a plane (shown by a broken line in FIG. 3). The amount of light going toward increases. As a result, the illumination light emitted from the light guide plate 12 is enhanced in directivity in the illumination direction.
[0033]
Furthermore, in this embodiment, the light guide plate 12 has a pair of inclined surfaces 12E and 12F formed with an equal inclination with respect to the exit surface, and an angle α1 formed by the inclined surfaces 12E and 12F is selected to be about 60 degrees. Yes. The apex angle α1 can be appropriately selected within the range of 50 degrees to 130 degrees to obtain practical characteristics, but is preferably within the range of 60 degrees to 110 degrees.
[0034]
Further, in the light guide plate 12, these minute convex portions are, for example, a repetition pitch W1 of 50 [μm] which is smaller than 1/4 of the pixel period of the liquid crystal display panel to which the sidelight type surface light source device 10 is applied. It is formed by.
[0035]
The prism sheet 13 is a single-sided prism sheet having a prism surface formed on the light guide plate 12 side. Here, the prism surface is formed by transparent acrylic PET as a base, and an acrylic ultraviolet curable resin or the like is cured in a predetermined shape on the surface.
[0036]
As shown in FIG. 1, the prism sheet 13 is repeatedly formed with small convex portions in the direction orthogonal to the incident surface 12A on the side surface of the exit surface 12C. A prism surface is formed. Here, the minute convex portions have a pair of inclined surfaces 13A and 13B extending in parallel with the incident surface 12A of the light guide plate 12. In this embodiment, the pair of inclined surfaces 13A and 13B are directly connected. The cross section is formed in a triangular shape.
[0037]
Thereby, the prism sheet 13 is formed such that the same convex portion is repeatedly formed in a direction orthogonal to the repeating direction of the convex portion in the light guide plate 12, and as shown in FIG. Illumination light L emitted from the light guide plate 12 while being inclined toward the front end of the wedge shape is guided to the inside by the inclined surface 13A on the incident surface 12A side, reflected by the inclined surface 13B forming a pair with the inclined surface 13A, and the front direction of the emitting surface 12C To exit. Accordingly, the prism sheet 13 is configured to correct the directivity of the emitted light in the front direction of the emission surface 12C in a plane orthogonal to the incidence surface 12A.
[0038]
Further, in this embodiment, the prism sheet 13 has a pair of inclined surfaces 13A and 13B formed with an equal inclination with respect to the exit surface, and an angle α2 formed by the inclined surfaces 13A and 13B is selected to be about 66 degrees. Yes. The apex angle α2 can be appropriately selected within the range of 30 ° to 70 ° to obtain practical characteristics, but is preferably within the range of 50 ° to 70 °, more preferably 60 ° to 70 °. .
[0039]
Further, in the prism sheet 13, these minute convex portions are, for example, a repetition pitch W2 of 50 [μm] which is smaller than ¼ of the pixel period of the liquid crystal display panel to which the sidelight type surface light source device 10 is applied. It is formed by.
[0040]
In the above configuration, the illumination light L emitted from the fluorescent lamp 7 (FIGS. 1 and 2) is reflected directly or after being reflected by the reflector 8 and then enters the light guide plate 12 from the incident surface 12A, and is emitted. While being scattered by 12 </ b> C, reflection is repeated between the back surface 12 </ b> B and the exit surface 12 </ b> C and propagates inside the light guide plate 12. At this time, every time the illumination light L is reflected by the back surface 12B, the incident angle with respect to the emission surface 12C decreases, and a component having a critical angle or less with respect to the emission surface 12C is emitted from the emission surface 12C.
[0041]
Further, at this time, the illumination light is diffused by the rough surface formed on the emission surface 12C of the light guide plate 12, and the emission from the emission surface 12C is promoted. Further, the illumination light leaking from the back surface 12B of the light guide plate 12 is reflected by the reflection sheet 11 made of a regular reflection member arranged on the back surface 12B side, and is efficiently returned to the inside of the light guide plate 2, thereby efficiently emitting the light exit surface. The light is emitted from 12C.
[0042]
The illumination light L propagating through the interior in this way has a back surface constituted by a flat surface by emitting a component less than the critical angle from the illumination light propagating from the incident surface 12A toward the wedge-shaped tip. In this case, as shown in FIG. 5, the light is emitted with directivity inclined toward the wedge-shaped tip, and with the spread directivity in the direction along the incident surface 12A. In FIG. 5, the angle of the illumination light emitted from the light guide plate 12 in each direction is defined as Xθ being the angle in the direction along the incident surface 12A and Yθ being the angle in the direction perpendicular to the surface. The intensity was detected.
[0043]
On the other hand, in this embodiment, as shown in FIG. 6 in comparison with FIG. 5, the inclined surfaces 12E and 12F of the convex portions repeatedly formed in parallel with the incident surface (FIG. 3) In a parallel plane, the directivity is corrected so that the illumination light emitted so as to spread outward is directed inward, and then emitted. Accordingly, the directivity of the emitted light can be corrected in the front direction of the exit surface 12C in a plane parallel to the entrance surface 12A without using the prism sheet 6 (FIG. 12) having the conventional configuration. Therefore, the prism sheet 6 can be omitted and the use efficiency of the illumination light can be improved accordingly.
[0044]
The illumination light L emitted from the emission surface 12C in this way is transmitted through the subsequent prism sheet 13 and illuminates a liquid crystal panel or 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 by repeatedly forming convex portions by the inclined surfaces 13A and 13B parallel to the incident surface 12A, and then the pair of inclined surfaces 13A and 13A. The light enters the prism sheet 13 through the inclined surface 13A facing the incident surface 12A side of 13B 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. 7 in comparison with FIG. 6, the directivity of the emitted light is in the front direction of the exit surface 12C in a plane orthogonal to the entrance surface 12A. It is corrected.
[0045]
The illumination light incident on the prism sheet 13 in this way is directly incident from the light guide plate 12 through the inclined surface 13A, so that the side light type surface light source device of the conventional configuration in which the side surface of the light guide plate 12 is flat (FIG. 13). ), The component reflected by the incident surface of the prism sheet 6 and returned to the light guide plate 2 is also actively guided into the prism sheet 13 and emitted in the front direction of the emission surface 12C. Thereby, the utilization efficiency of illumination light is improved accordingly.
[0046]
By the way, in the side light type surface light source device of the conventional configuration, the illumination light component reflected by the incident surface of the prism sheet 5 is multiply reflected between the prism sheet 5 and the light guide plate. When the directivity of the emitted light was measured, it was found that a peak with a small luminance level was generated in the vicinity of the front surface of the emission surface. In this embodiment, such a component can also be efficiently guided in the front direction of the emission surface 12C, the directivity can be improved correspondingly, and the utilization efficiency of illumination light can be improved.
[0047]
In correcting the directivity in this way, on the back surface 12B of the light guide plate 12 and the prism surface of the prism sheet 13, a large number of convex portions are repeatedly formed. In the repeating direction, a minute pulsation of the luminance level occurs. If the pixel pitch of the liquid crystal display panel is close to this pulsation, so-called moire occurs, and the quality of the display image is significantly degraded. That is, in this case, when viewed from the sidelight type surface light source device, the quality of the emitted light is lowered.
[0048]
On the other hand, in this embodiment, the convex portions are repeated at the repetition pitches W1 and W2 of 50 [μm], which is 1/4 or more smaller than the pixel period of the liquid crystal display panel. It is possible to reduce the pulsation of the luminance level in the repetitive pitch sufficiently separated from the pitch, and to effectively avoid the generation of moire. Further, the repetition of these convex portions can be made inconspicuous.
[0049]
Furthermore, in this embodiment, in the light guide plate 12, the pair of inclined surfaces 12E and 12F forming the convex portions are formed with the same inclination with respect to the back surface 12B, and the angle α1 formed by the inclined surfaces 12E and 12F is about 60 degrees. By being selected, a practically sharp directivity can be obtained.
[0050]
In this way, when the illumination light is emitted, the light guide plate 12 has a convex portion formed on the back surface of the light guide plate 12 so that the convex portion of the light guide plate 12 is protected by the frame. Since the convex portion is formed on the light guide plate 12 side, the convex portion is protected by the light guide plate 12. Thereby, in the sidelight type surface light source device 10, the appearance defect is remarkably reduced as compared with the conventional case.
[0051]
According to the above configuration, convex portions having a triangular cross section formed by a pair of inclined surfaces 12E and 12F are repeatedly formed in parallel to the incident surface on the back surface 12B of the light guide plate 12, and similar convex portions are formed on the prism sheet 13. By repeatedly forming the light guide plate 12 on the light guide plate 12 side in a direction orthogonal to the direction in which the convex portions of the light guide plate 12 are repeated, illumination light can be efficiently emitted with a simpler configuration than in the past.
[0052]
Further, at this time, these convex portions are repeatedly formed at a repetition pitch W1 and W2 of 50 [μm], which is smaller than 1/4 of the pixel period of the liquid crystal display panel, thereby effectively avoiding the generation of moire. Accordingly, high-quality illumination light can be emitted. Further, the repetition of these convex portions can be made inconspicuous.
[0053]
In the light guide plate 12, the pair of inclined surfaces 12E and 12F forming the convex portions are set to have the same inclination with respect to the emission surface, and the angle α1 formed by the inclined surfaces 12E and 12F is selected to be about 60 degrees. A sufficiently sharp directivity can be obtained.
[0054]
(2) Second embodiment
In the side light type surface light source device according to this embodiment, a prism sheet 14 shown in FIG. 8 is applied instead of the prism sheet 13 described above with reference to FIG. In the side light type surface light source device according to the second embodiment, the other structure is the same as that of the side light type surface light source device 10 described above with reference to FIG. Therefore, a duplicate description is omitted.
[0055]
In other words, in this side light type surface light source device, the prism sheet 14 is repeatedly formed with minute convex portions parallel to the incident surface 12A on the surface on the exit surface 12C side, as in the first embodiment. As a result, a prism surface is formed. Further, the prism sheet 14 is formed by a pair of inclined surfaces 14A and 14B extending in parallel with the incident surface 12A of the light guide plate 12, and the inclined surfaces 14A and 14B are set to have different inclinations. Yes.
[0056]
That is, the inclined surface 14A on the incident surface 12A side guides the incident illumination light to the inclined surface 14B without waste so that the main illumination light that is inclined and emitted from the light guide plate 12 toward the wedge-shaped tip side is incident at a small incident angle. Thus, it is formed with a small inclination β1 with respect to the normal L1 of the exit surface 12C. On the other hand, the other inclined surface 14B is formed with a larger inclination β2 than the inclined surface 14A so that the illumination light incident from the inclined surface 14A is totally reflected in the front direction of the exit surface 12C.
[0057]
That is, as shown by the characteristic curve in FIG. 6, the illumination light emitted from the light guide plate 12 is approximately 20 degrees from the vertical direction, with the main emission direction being a direction inclined by about 70 degrees from the vertical direction toward the wedge tip. It is emitted in the range of ˜85 degrees. Therefore, after the illumination light in the main emission direction is incident from the inclined surface 14A on the incident surface 12A side, the inclination β1 from the refractive index n of the prism sheet 14 is reflected on the other inclined surface 14A in the front direction of the output surface 12C. The relation of β2 is set.
[0058]
Further, assuming this relationship, the inclination β1, so that the illumination light emitted from the light guide plate 12 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. β2 is set. In this embodiment, the angles β1 and β2 are set to 5.5 degrees and 35 degrees, respectively.
[0059]
That is, as shown in FIG. 9, when the inclined surfaces 13A and 13B are set to have the same inclination as in the configuration according to the first embodiment, the inclined surface 13A on the incident surface 12A side is totally reflected and returned to the light guide plate 12. The illumination light component LA to be generated is generated. Even if the illumination light is incident from the inclined surface 13A on the incident surface 12A side, it is not totally reflected by the other inclined surfaces, and the component LB directly emitted is also generated. In addition, a component that is repeatedly reflected and emitted by the repeatedly formed convex portion is also generated.
[0060]
For these reasons, as shown by arrows G and H in FIG. 7, in the sidelight type surface light source device, a peak like a so-called side lobe occurs in the main emission direction.
[0061]
However, if the angles β1 and β2 are set to 5.5 degrees and 35 degrees, respectively, as in this embodiment, as shown in FIG. 10 in comparison with FIG. 7, they pass through the inclined surfaces 13A and 13B in this way. Thus, the directly emitted illumination light component LB or the like can be incident from the inclined surface 14A and guided to the other inclined surface 14B, or can be transmitted through the inclined surface 14A and directly emitted in the front direction. Further, the illumination light component LA returning to the inside of the light guide plate 12 can also be reduced.
[0062]
Furthermore, if it does in this way, the area of the corresponding slope 14B can be increased compared with the slope of the incident surface 12A side seeing from the liquid crystal panel side. Thereby, the minute pulsation of the emitted light amount due to the repetition of the minute convex portions is reduced, and the moire is reduced accordingly. That is, moire may be detected by the configuration according to the first embodiment by being perceived through vision. It is also detected when the repetition pitch of the convex portion is increased. However, if the minute pulsation of the amount of emitted light is reduced in this way, it is possible to make it difficult to detect moire even in such a case.
[0063]
According to the configuration shown in FIG. 8, in addition to the first configuration, the inclined surface forming the convex portion of the prism sheet has a small inclination on the incident surface side with respect to the normal of the exit surface, and the corresponding inclined surface Is set to a large inclination, the use efficiency of the illumination light can be improved correspondingly, and high-quality illumination light can be emitted.
[0064]
(3) Third embodiment
FIG. 11 is a plan view showing a sidelight type surface light source device 30 according to the 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. 8 except that the configurations of the light guide plate 31 and the prism sheet 32 are different. Therefore, a duplicate description of these configurations is omitted.
[0065]
In the side light type surface light source device 30, the light guide plate 31 has a convex portion having a triangular cross section formed repeatedly on the back surface, and a pair of inclined surfaces forming the convex portion has a predetermined angle from a direction perpendicular to the incident surface 31A. It is formed so as to be inclined by θA.
[0066]
Further, in this sidelight type surface light source device 30, the prism sheet 32 has a pair of protrusions that are the same as the protrusions according to the second embodiment, formed repeatedly on the light guide plate 31 side, and forms a pair. Is extended in a direction orthogonal to the extending direction of the inclined surface of the light guide plate 31. In FIG. 11, the extending direction of these slopes is indicated by a straight line.
[0067]
In this embodiment, the light guide plate 31 and the prism sheet 32 have convex portions formed repeatedly at a repetition pitch of 50 [μm], and the inclination angle θA is set to a range of 10 degrees or less, more preferably 5 degrees or less. The
[0068]
That is, in the sidelight type surface light source device 30, if the extending direction of each inclined surface is arranged perpendicularly and parallel to the incident surface 12A, the illumination level overlaps with this pulsation direction for illumination light with a slight pulsation. In addition, each pixel of the liquid crystal panel regularly forms an opening, which makes it easy to generate moire. On the other hand, the occurrence of moiré can be reduced if the repeating 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.
[0069]
However, if this inclination is increased, the directivity of the illumination light emitted from the sidelight type surface light source device is disturbed.
[0070]
Accordingly, in this embodiment, the repeating direction of the convex portion is tilted within a range of 10 degrees or less, effectively avoiding the deterioration of directivity and making it difficult to detect moire.
[0071]
According to the configuration shown in FIG. 11, in addition to the configuration according to the second embodiment, the repetition directions of the convex portions in the light guide plate 31 and the prism sheet 32 are set to 10 while being held so as to be orthogonal to each other. By tilting within a range of less than or equal to degrees, it is possible to obtain the same effect as that of the second embodiment, and in addition to this, effectively avoiding the deterioration of the directivity of the emitted light, Furthermore, it can be made more difficult to perceive.
[0072]
(4) Other embodiments
In the first to third embodiments described above, the case where a large number of convex portions are formed on the light guide plate and the prism sheet with a repetition pitch of 50 [μm] has been described, but the present invention is not limited thereto, Depending on the liquid crystal panel, convex portions can be formed with a repetitive pitch of approximately 100 [μm] or less, making it difficult to perceive moiré.
[0073]
Furthermore, in the above-described third embodiment, the case where the light guide plate and the prism sheet are held so that the repeating direction of the convex portions is orthogonal to each other and the repeating direction of the convex portions is inclined by the angle θA has been described. The present invention is not limited to this, and this orthogonal relationship may be disturbed by a minute angle. That is, the prism sheet is tilted within a range of 10 degrees or less with respect to the direction parallel to the incident surface of the light guide plate, and the convex portions of the light guide plate are repeated within a range of 10 degrees or less with respect to the repeating direction of the convex portions of the prism sheet. By tilting the direction, practically sufficient directivity can be obtained, and generation of moire can be reduced.
[0074]
In the first to third embodiments described above, the case in which the slopes are directly connected and the convex portions are formed in a triangular cross section has been described. However, the present invention is not limited thereto, and a flat surface, a smooth curve, etc. A pair of slopes may be connected to each other, or adjacent convex portions may be connected.
[0075]
Furthermore, in the above-described third embodiment, a case has been described in which the pair of inclined surfaces in the prism sheet are set to different inclinations, and the convex portions are inclined repeatedly in the light guide plate and the convex portions of the prism sheet. The invention is not limited to this, and when a practically sufficient characteristic can be obtained, the inclined surface may be set to an equal inclination and only the repeating direction of the convex portion may be inclined.
[0076]
In the above-described embodiment, the case of using a prism sheet formed by curing an ultraviolet curable resin based on transparent PET has been described. However, the present invention is not limited to this, and polycarbonate, PC, PMMA, and the like are used. The present invention can also be applied to a case where a prism sheet formed using a light-transmitting material is used. Further, the present invention can be widely applied to the case where a plate-like member having a predetermined thickness without flexibility is formed by these light-transmitting materials, and such a so-called prism body is used in place of the prism sheet.
[0077]
Furthermore, in the above-described first to third embodiments, the case where the reflection sheet, the light guide plate, and the prism sheet are stacked has been described, but the present invention is not limited thereto, and a light diffusion sheet that diffuses illumination light is used. The present invention can be widely applied also when it is arranged between the prism sheet and the light guide plate or on the upper surface of the prism sheet. In this way, directivity can be corrected by the light diffusion sheet.
[0078]
In the first to third embodiments described above, the case where the reflection sheet is formed by the regular reflection member made of the silver-deposited sheet material has been described. However, the present invention is not limited to this, and various regular reflections are made. The present invention can also be widely applied to the case where a reflection sheet is formed by a member, or a diffuse reflection member such as white PET.
[0079]
Furthermore, in the above-described first to third embodiments, the case where the light diffusing surface is formed by forming the entire light emitting surface of the light guide plate into a uniform rough surface by the mat surface treatment has been described. The present invention is not limited to this, and the present invention can be widely applied to the case where the light diffusing surface is formed by blasting using sandpaper or chemical etching, and the case where the light diffusing surface is formed by printing with white ink or the like.
[0080]
In the first to third embodiments described above, the case where the light diffusing surface is formed by forming a uniform rough surface on the entire exit surface of the light guide plate has been described. However, the present invention is not limited to this. For example, when the degree of the rough surface is changed so that the degree of comparative diffusion gradually increases from the incident surface side toward the wedge-shaped tip, or when printing is performed, the printing amount per unit area is sequentially changed. It can be widely applied to cases.
[0081]
Furthermore, in the first to third embodiments described above, the case where the light guide plate is formed by the transparent member has been described. However, the present invention is not limited to this, and the transparent member is mixed with fine particles that scatter light. The present invention can also be widely applied when forming an optical plate.
[0082]
Further, in the first to third embodiments described above, the case where the present invention is applied to a sidelight type surface light source device using a light guide plate made of a plate-shaped member having a wedge-shaped cross section has been 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 configured by a flat plate-shaped member.
[0083]
Furthermore, 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 side light type surface light source device configured to receive the illumination light from another end face is also provided. Can also be widely applied.
[0084]
Further, in the above-described embodiment, the case where the primary light source is configured by the fluorescent lamp made of a rod-shaped light source has been described. However, the present invention is not limited thereto, and a plurality of point light sources such as light emitting diodes are arranged to form the primary light source. It can be widely applied to cases.
[0085]
Further, in the above-described embodiment, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described. However, the present invention is not limited to this, and the sidelight type surface light source device such as various illumination devices and display devices. Can be widely applied to.
[0086]
【The invention's effect】
As described above, according to the present invention, by repeatedly forming a convex portion having a pair of slopes on the back surface of the plate-like member and repeatedly forming the same type of convex portion on the plate-like member side of the light control member, Furthermore, by selecting the shape of this convex portion as necessary, the illumination light can be efficiently emitted to improve the use efficiency of the illumination light, and further the deterioration of the quality of the emitted light due to moire etc. can be reduced. Can do.
[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 taken along line BB in FIG.
3 is a cross-sectional view showing in detail a back surface of a light guide plate in the sidelight type surface light source device of FIG. 1. FIG.
4 is a cross-sectional view showing in detail a prism sheet in the sidelight type surface light source device of FIG. 1. FIG.
FIG. 5 is a characteristic curve diagram showing a distribution of illumination light emitted from a conventional light guide plate for comparison with the side light type surface light source device of FIG. 1;
6 is a characteristic curve diagram showing a distribution of illumination light emitted from the light guide plate of the sidelight type surface light source device of FIG. 1. FIG.
7 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. 1. FIG.
FIG. 8 is a cross-sectional view showing a prism sheet applied to a sidelight type surface light source device according to a second embodiment of the present invention.
FIG. 9 is a cross-sectional view showing an optical path of illumination light in a prism sheet having a conventional configuration in comparison with FIG.
10 is a characteristic curve diagram showing directivity in the sidelight type surface light source device of FIG. 8. FIG.
FIG. 11 is a cross-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. 12 is an exploded perspective view showing a conventional sidelight type surface light source device.
FIG. 13 is a sectional view taken along line AA in FIG.
[Explanation of symbols]
1, 10, 30 Sidelight type surface light source device
2, 12, 31 Light guide plate
2A, 12A, 31A Incident surface
2B, 12B back
5, 6, 13, 14, 32 Prism sheet
12E, 12F, 13AA-14B Slope

Claims (5)

In the sidelight type surface light source device that makes the illumination light emitted from the predetermined light source incident from the end face of the plate member, bends the illumination light and emits it from the emission surface of the plate member,
A light control member is disposed on the exit surface of the plate-shaped member,
The plate-like member is
A convex portion having a pair of inclined surfaces extending in a direction substantially orthogonal to the end surface is repeatedly formed in a direction substantially parallel to the end surface on the surface facing the emission surface side,
The light control member is
A convex portion having a pair of inclined surfaces extending in a direction substantially parallel to the end surface is repeatedly formed in a direction substantially orthogonal to the end surface on the surface facing the plate-like member,
The plate-like member and the light control member are
The convex portion is formed with a repeating pitch of 100 [μm] or less ,
The light control member is
Of the pair of inclined surfaces, the illumination light emitted from the plate-like member is transmitted through the inclined surface relatively close to the end surface and guided to the inside, and the inclined surface relatively far from the end surface is used. Reflected and emitted,
The plate-like member is
An angle formed by the pair of inclined surfaces is set to an angle greater than 90 degrees and 110 degrees or less . The convex portion of the light control member is
Of the pair of slopes constituting the convex portion, the angle formed by the slope that is relatively close to the end face and the normal line of the exit face is relatively far from the end face 2. The sidelight type surface according to claim 1, wherein the pair of inclined surfaces are formed to have different inclinations so as to be smaller than an angle formed by the inclined surface and a normal line of the emission surface. Light source device. The slope on the side relatively close to the end face is
The angle is selected so as to guide the main illumination light emitted from the exit surface to a slope on a side far from the end surface,
The far slope is
The side light type surface light source device according to claim 2, wherein the angle is selected so that the illumination light coming from the near slope is totally reflected and substantially reflected in the normal direction. . The light control member is
In a range of 10 degrees or less, it is arranged such that the extending direction of the slope is inclined from the direction parallel to the end face,
The plate-like member is
The repeating direction of the inclined surface is arranged so as to be inclined within a range of 10 degrees or less with respect to the extending direction of the inclined surface of the light control member. The sidelight type surface light source device described. The light control member is
The direction in which the slope extends in a range of 10 degrees or less is arranged to be inclined from the direction parallel to the end face,
The plate-like member is
The side light type surface light source according to claim 1, 2 or 3, wherein a direction in which the inclined surface extends is set to be orthogonal to a direction in which the inclined surface of the light control member extends. apparatus.

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