JP3676076B2 - Sidelight type surface light source device and liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sidelight type surface light source device and a liquid crystal display device, and can be applied to an in-vehicle liquid crystal display device applied to a car navigation system. In the present invention, the directivity can be switched as necessary by stacking plate members each having a light source and configuring the surface light source device so as to emit illumination light with directivity by each plate member. Like that.
[0002]
[Prior art]
Conventionally, in a liquid crystal display device of a car navigation system, a liquid crystal display panel is illuminated by a sidelight type surface light source device so that visibility is most improved in the front direction of the display screen.
[0003]
This type of side-light type surface light source device receives illumination light of a primary light source from the end face of a transparent plate member (hereinafter referred to as a light guide plate) such as acrylic, and repeatedly reflects this illumination light inside the light guide plate. Propagate. Furthermore, the directivity of the illumination light that leaks during this propagation is corrected by a prism sheet made of a light control member disposed on the exit surface of the light guide plate. Thus, the sidelight type surface light source device corrects the directivity of the illumination light in the normal direction of the emission surface and emits it to the liquid crystal display panel.
[0004]
[Problems to be solved by the invention]
By the way, in-vehicle liquid crystal display devices such as a car navigation system stop displaying while driving for safety. In such a liquid crystal display device, it is considered convenient if only the driver cannot view the display while traveling and the driver can view the display while the vehicle is stopped. That is, if it can be done in this way, it can be considered that this type of liquid crystal display device can be viewed by a passenger who has nothing to do with driving, and this type of system can be used effectively without sacrificing safety.
[0005]
In this case, in the side light type surface light source device that supplies illumination light to the liquid crystal display panel, if the directivity can be switched as necessary, only the passenger can view the display while traveling, and the passenger when stopped. Everyone can view the display.
[0006]
The present invention has been made in consideration of the above points, and includes a sidelight type surface light source device capable of variously switching directivity as necessary, and a liquid crystal display device using the sidelight type surface light source device. It is what we are going to propose.
[0007]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 is applied to the sidelight type surface light source device, and the first illumination light emitted from the first primary light source is incident from the end surface, and the first illumination is performed. A first plate-like member that bends the light and emits it from the exit surface, and the second illumination light emitted from the second primary light source is incident on the end surface, and is superimposed on the first plate-like member. And a second plate-like member that makes the first illumination light emitted from the first plate-like member incident from the back surface facing the emission surface and emits the first and second illumination lights from the emission surface. Prepared, In the first plate-like member, a projection formed by a pair of inclined surfaces is repeatedly formed along the end surface on the emission surface and / or the surface facing the emission surface, and the second plate-like member faces at least the emission surface. The surface is formed by a flat surface, The first emission direction by the first illumination light and the second emission direction by the second illumination light different from the first emission direction are set to have directivity.
[0008]
According to the structure which concerns on Claim 1, By the 1st plate-shaped member, the directional surface light source by the 1st output direction and the directional surface light source by the 2nd plate-shaped member by the 2nd output direction by Illumination light can be emitted, with a uniform emission light quantity distribution, and optionally by stopping the supply of the first or second illumination light, optionally depending on the first or second directivity Illumination light can be emitted.
[0011]
And claims 2 In the invention according to claim 1's In the configuration, a light control member that corrects the directivity of illumination light emitted from the emission surface of the second plate member is disposed on the emission surface of the second plate member.
[0012]
Claim 2 With this configuration, the light control member that corrects the directivity of the illumination light emitted from the emission surface of the second plate member is disposed on the emission surface of the second plate member. The first and second directivities can be corrected to a desired directivity.
[0013]
And claims 3 In the invention according to claim 1, Or claim 2 In the configuration, the first plate-like member has an emission surface formed in a rectangular shape, the first illumination light is incident from the end surface on the short side of the rectangular shape, and the second plate-like member has an emission surface. It is formed in a shape substantially equal to the first plate member, and the second illumination light is incident from the end surface on the short side.
[0014]
Claim 3 According to the above configuration, the present invention is applied to a general liquid crystal display device with a horizontally long display screen so that a viewer who views from a specific position such as a driver seat or a passenger seat can selectively view the display screen. Illumination light can be emitted.
[0015]
And claims 4 The invention according to claim 1 is applied to a liquid crystal display device. Or claim 3 The liquid crystal display panel is illuminated by the sidelight type surface light source device described in 1).
[0016]
Further claims 5 In the invention according to claim 4 In the configuration, the emission of the first or second illumination light from the first or second light source can be selectively stopped.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
[0018]
(1) First embodiment
FIG. 1 is an exploded perspective view showing a sidelight type surface light source device applied to the liquid crystal display device according to the first embodiment of the present invention. FIG. 2 shows the sidelight type surface light source device 1 as a liquid crystal. It is sectional drawing of the liquid crystal display device shown with a display panel, a drive circuit, etc.
[0019]
The liquid crystal display device 2 is applied to a car navigation system and is driven by selectively driving two primary light sources 3A and 3B built in the sidelight type surface light source device 1 by a drive circuit 4 (FIG. 2). , The display screen is formed so that only the passenger 5A in the passenger seat can view, and the display screen is formed so that both the passengers 5A and 5B in the passenger seat and the driver seat can view both during the stop.
[0020]
For this reason, the sidelight type surface light source device 1 arranges the primary light sources 3A and 3B on the sides of the first and second light guide plates 7A and 7B, respectively, and the reflection sheet 8, the first light guide plate 7A, and the second light source plate 7A and 7B. The light guide plate 7B, the prism sheet 9 made of a light control member, and the light diffusion sheet 10 are sequentially laminated.
[0021]
Here, the primary light sources 3A and 3B are formed by surrounding the fluorescent lamps 11A and 11B made of cold cathode tubes with the reflectors 12A and 12B, respectively, and the end faces (hereinafter referred to as the light guide plates 7A and 7B) from the opening side of the reflectors 12A and 12B. The illumination light is incident on 7AI and 7BI. Here, the reflectors 12 </ b> A and 12 </ b> B are reflecting members that regularly or irregularly reflect incident light, and are formed of, for example, a sheet material.
[0022]
The reflection sheet 8 is formed by 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, etc., and reflects the illumination light leaking from the light guide plate 7A and enters the light guide plate 7A. This improves the use efficiency of the illumination light.
[0023]
The first light guide plate 7A is a plate-shaped member having a wedge-shaped cross section. For example, translucent fine particles having a refractive index different from that of a matrix made of polymethyl methacrylate (PMMA) are uniformly dispersed and mixed. Formed. The light guide plate 7A is formed such that a surface 7AO on the light guide plate 7B side (hereinafter referred to as an emission surface) is formed in a rectangular shape, and the plate thickness gradually decreases along the long side of the rectangular shape. The end surface of the light guide plate 7A along the short side on the thick side is set as the incident surface 7AI, and the illumination light LA of the primary light source 3A is incident from the incident surface 7AI. As a result, the light guide plate 7A scatters the illumination light LA incident from the incident surface 7AI with the light-transmitting fine particles, and between the output surface 7AO and the surface (hereinafter referred to as the back surface) 7AR facing the output surface 7AO. The illumination light LA is propagated by being repeatedly reflected. Further, during this propagation, the illumination light LA incident on the emission surface 7AO is emitted from the emission surface 7AO at a subcritical incident angle.
[0024]
Further, the light guide plate 7A is formed with a light scattering pattern for promoting the emission of the illumination light LA propagating through the inside on the emission surface 7AO, thereby making the light quantity distribution of the illumination light LA emitted from the emission surface 7AO uniform. ing. The light scattering pattern is partially roughened on the exit surface 7AO due to a minute size that is difficult to see with the naked eye from the exit surface 7AO side (for example, preferably about 80 [μm] or less). Formed on the surface. Further, the light scattering pattern is formed by an irregular arrangement, so that generation of moire fringes due to interference with the liquid crystal display panel can be effectively avoided.
[0025]
Further, the light guide plate 7A is repeatedly formed with protrusions by a pair of inclined surfaces along the incident surface 7AI on the back surface 7AR, as shown enlarged by the reference symbol A. Here, these protrusions are formed in a triangular cross section by directly connecting the pair of inclined surfaces. As a result, the light guide plate 7A reduces the incident angle of the illumination light LA incident on the exit surface 7AO, efficiently emits the illumination light, and further sees directivity in the in-plane direction along the entrance surface 7AI. The illumination light is emitted with a sharp directivity in the normal direction of the emission surface 7AO. As a result, the illumination light emitted from the emission surface 7AO is emitted with a large amount of light toward the normal direction of the emission surface 7AO in the in-plane direction along the incidence surface 7AI.
[0026]
The second light guide plate 7B is formed in substantially the same shape using the same material as the first light guide plate 7A. The light guide plate 7B is superimposed on the light guide plate 7A and disposed on the output surface side of the light guide plate 7A so that the end surface of the first light guide plate 7A on the wedge-shaped front end side and the incident surface 7BI form substantially the same surface. Is done. As a result, the light guide plate 7B receives the illumination light LB from the primary light source 3B arranged on the incident surface 7BI side, and scatters the illumination light LB with the light-transmitting fine particles, while the light exit plate 7B and the back surface 7BR Propagate repeatedly between them. Further, the illumination light LA emitted from the light guide plate 7A enters from the back surface 7BR, passes through the incident illumination light LA, and exits from the exit surface 7BO.
[0027]
Further, similarly to the light guide plate 7A, the light guide plate 7B has a light scattering pattern formed on the emission surface 7BO, thereby making the light quantity distribution of the illumination light propagating through the inside uniform. Furthermore, the light guide plate 7B has a back surface 7BR formed by a substantially flat mirror surface, as shown by an enlargement by the symbol B, so that illumination light incident on the back surface 7BR from the light guide plate 7A can be incident on the inside without waste. ing.
[0028]
The prism sheet 9 is arranged to correct the directivity between the illumination light propagating through the inside of the light guide plate 7B and the illumination light emitted from the light guide plate 7A and transmitted through the light guide plate 7B. Is done. That is, the prism sheet 9 is formed of a translucent sheet material such as polycarbonate, and a prism surface is formed on the surface opposite to the side facing the light guide plate 7B. The prism surface is formed by repeating a protrusion having a triangular cross-section directly connecting a pair of inclined surfaces in a direction orthogonal to the extending direction of the incident surface of the light guide plate 7B, as shown in an enlarged manner by C.
[0029]
In the prism sheet 9, the apex angle by the pair of slopes is set to an angle of 66 degrees, and the pair of slopes is set to an equal inclination.
[0030]
The light diffusing sheet 10 is made of a sheet material having light diffusibility, and scatters the illumination light weakly so that the brightness of the edge of the light guide plate 7A cannot be perceived through the liquid crystal display panel.
[0031]
In the above configuration, the illumination light LA emitted from the fluorescent lamp 11A on the light guide plate 7A side (FIG. 2) is reflected directly or after being reflected by the reflector 12A, and then enters the light guide plate 7A from the incident surface 7AI. While being scattered by the translucent fine particles inside, it is repeatedly reflected between the back surface 7AR and the exit surface 7AO and propagates inside the light guide plate 7A. At this time, every time the illumination light LA is reflected by the back surface 7AR, the incident angle with respect to the emission surface 7AO decreases, and a component having a critical angle or less with respect to the emission surface 7AO is emitted from the emission surface 7AO.
[0032]
Further, at this time, the illumination light LA is urged to be emitted by the light scattering pattern formed on the emission surface 7AO of the light guide plate 7A. As a result, the illumination light LA is emitted from the emission surface 7AO with a substantially constant light amount distribution and a directivity that is further inclined toward the wedge-shaped tip side.
[0033]
Further, the incident angle of the illumination light LA with respect to the emission surface 7AO is reduced when propagating through the projections formed by the pair of inclined surfaces formed on the back surface 7AR. As a result, the light is emitted from the emission surface 7AO with a smaller number of reflections inside than when the back surface 7AR is formed of a flat surface, and is emitted more efficiently. Further, when the directivity is seen in the in-plane direction along the incident surface 7AI, it is emitted with a sharp directivity in the normal direction of the exit surface 7AO, and as a result, the directivity is emitted with a large amount of light. The
[0034]
Thus, the illumination light LA emitted from the light guide plate 7A with the directivity inclined toward the wedge-shaped tip side enters the light guide plate 7B from the back surface 7BR of the light guide plate 7B and passes through the light guide plate 7B. The light is emitted from the emission surface 7BO of the light guide plate 7B. At this time, the cross-sectional shape of the light guide plate 7B is formed in a wedge shape, so that the illumination light LA1 emitted from the emission surface 7BO of the light guide plate 7B changes almost in the light guide plate 7A although the emission direction changes slightly. The light is emitted from the emission surface 7BO of the light guide plate 7B with the same directivity as that emitted from the emission surface 7AO.
[0035]
Further, the illumination light LA1 is efficiently incident on the light guide plate 7B and emitted from the exit surface 7BO of the light guide plate 7B because the back surface 7BR of the light guide plate 7B is formed by a substantially flat mirror surface. However, the illumination light LA1 is scattered and attenuated by the internal fine particles when passing through the light guide plate 7B, and is efficiently incident from the back surface 7BR of the light guide plate 7B. Spectral quantity is attenuated. In response to such attenuation of the light amount, the illumination light LA1 is incident on the back surface 7BR of the light guide plate 7B with a large amount of light at a directivity peak due to a pair of inclined surfaces formed on the back surface 7AR of the light guide plate 7A. The light quantity is prevented from being reduced by being emitted through the light guide plate 7B.
[0036]
FIG. 3 is a characteristic curve diagram showing the directivity of the illumination light LA1 emitted from the first light guide plate 7A in this way. In this figure, the longitudinal direction of the light guide plate 7A is set to the Y direction and the direction along the incident surface 7AI is set to the X direction with reference to the normal direction of the exit surface 7BO of the light guide plate 7B. According to the measurement result of FIG. 3, it can be seen that the illumination light LA1 is emitted with directivity inclined in the wedge-shaped tip direction. FIG. 3 shows the configuration shown in FIG. 2 in which the prism sheet 9, the light diffusion sheet 10, and the liquid crystal display panel are removed, only the fluorescent lamp 11A is turned on, and the directivity is measured from the exit surface 7BO of the light guide plate 7B. It is.
[0037]
On the other hand, in the second light guide plate 7B, the illumination light LB emitted from the fluorescent lamp 11B enters the light guide plate 7B from the incident surface 7BI and is scattered by the translucent fine particles inside. The reflection is repeated between the back surface 7BR and the exit surface 7BO and propagates through the light guide plate 7B. Further, the propagating illumination light LB is emitted with a directivity inclined from the emission surface 7BO toward the wedge-shaped tip in the same manner as the light guide plate 7A.
[0038]
FIG. 4 is a characteristic curve diagram showing the directivity of the illumination light LB1 emitted from the second light guide plate 7B in this way. In this figure, measurement was performed with the fluorescent lamp 11A of the primary light source 3A turned off and the fluorescent lamp 11B of the primary light source 3B turned on under the same conditions as in FIG. According to the measurement result of FIG. 4, it can be seen that the illumination light LB1 is emitted with the directivity inclined in the direction opposite to that in FIG. 3 and toward the wedge-shaped tip as in the case of the light guide plate 7A.
[0039]
Accordingly, when the two fluorescent lamps 11A and 11B are both turned on and the directivity of the emitted light is measured by comparing with FIG. 3 and FIG. 4, the emission direction by the illumination light LA1 and the illumination light LB1 are measured as shown in FIG. A directivity peak is formed in two directions, i.e., the emission direction due to.
[0040]
Thus, when the illumination lights LA1 and LB1 emitted from the emission surface 7BO of the light guide plate 7A pass through the prism sheet 9 arranged on the emission surface 7BO side, the directivity is given by the slope of the prism sheet 9. It is corrected. That is, as shown in FIG. 6, the illumination light LA1 on the first light guide plate 7A side is incident on the prism sheet 9, and then refracted and emitted by the inclined surface 9A facing the wedge-shaped tip side of the light guide plate 7A. The illumination light LB1 on the second light guide plate 7B side is incident on the prism sheet 9, and then is refracted and emitted by the inclined surface 9B facing the wedge-shaped tip side of the light guide plate 7B.
[0041]
In this embodiment, the light guide plates 7A and 7B are formed in substantially the same shape, the pair of inclined surfaces of the prism sheet 9 are set to have the same inclination, and the apex angle is set to 66 degrees. Accordingly, the illumination lights LA1 and LB1 refracted by the inclined surfaces 9A and 9B are emitted with directivity in a direction inclined by about 23 degrees from the normal direction of the emission surface.
[0042]
FIG. 7 shows the configuration shown in FIG. 2, with the liquid crystal display panel and the light diffusion sheet 10 removed, only the first fluorescent lamp 11A is lit, and the directivity of the illumination light LA2 by the first light guide plate 7A is measured. FIG. FIG. 8 is a characteristic curve diagram in which only the second fluorescent lamp 11B is turned on in the same state as FIG. 7, and the directivity of the illumination light LB2 by the second light guide plate 7B is measured. Further, in FIG. 9, in the same state as FIG. 7, the first and second fluorescent lamps 11A and 11B are turned on, and the directivity of the illumination lights LA2 and LB2 by the first and second light guide plates 7A and 7B is changed. It is the measured characteristic curve figure.
[0043]
In the liquid crystal display device 2, the illumination lights LA2 and LB2 having directivity in the first and second emission directions generated in this way are subjected to weak diffusion in the subsequent light diffusion sheet 10 and then applied to the liquid crystal display panel. As a result, a bright screen can be viewed as viewed from the emission directions of the illumination lights LA2 and LB2, while the brightness of the display screen is observed as viewed from other directions.
[0044]
As a result, both the fluorescent lamps 11A and 11B are turned on, and the images formed by the liquid crystal display panel can be viewed by both passengers 5A and 5B in the passenger seat and driver seat. On the other hand, only the fluorescent lamp 11A or 11B is turned on, and a display image is formed so that only the passenger 5A in the passenger seat or the passenger 5B in the driver seat can view.
[0045]
According to the above configuration, the directivity can be variously switched as necessary by stacking the light guide plates each having the primary light source and emitting the illumination light by the directivity of each light guide plate.
[0046]
Incidentally, even if the primary light source is arranged on both end faces of the flat light guide plate, the directivity can be switched as in this embodiment by switching the primary light source to light. However, in this case, the light quantity distribution of the emitted light changes significantly by switching the primary light source. However, if each of the light guide plates is arranged as in this embodiment, illumination light can be emitted in each direction with a uniform amount of emitted light, and the directivity can be switched as necessary.
[0047]
In the lower first light guide plate, protrusions are repeatedly formed on the back surface, and in the upper second light guide plate, the back surface is formed by a flat surface, so that the illumination emitted from the first light guide plate Light can be emitted efficiently, and as a result, the utilization efficiency of illumination light can be improved as a whole. Further, the display image can be viewed with substantially the same brightness on the driver seat side and the passenger seat side.
[0048]
In addition, in the light guide plate with the output surface formed in a rectangular shape, the primary light source is arranged on the short side, so that when the liquid crystal display device is viewed on-board, it is oriented toward the driver's seat and passenger's seat that are required. Thus, it is possible to selectively turn on the fluorescent lamps and turn them on together so that only the desired passenger can view the display screen.
[0049]
(2) Other embodiments
In the above-described embodiment, the lower first light guide plate has a protrusion on the back surface, and the upper second light guide plate has a case where the back surface is formed with a mirror surface. The invention is not limited to this, and when a practically sufficient characteristic can be obtained, the lower first light guide plate may be formed with projections on either or both of the emission surface, the back surface, and the emission. Both the surface and the back surface may be mirror surfaces. In the upper light guide plate, from the viewpoint of efficiently transmitting and emitting the illumination light emitted from the lower light guide plate, it is desirable not to form protrusions on the emission surface and the back surface, but it is practically sufficient. If this characteristic is obtained, the upper light guide plate can also emit light. On the face A protrusion may be formed.
[0050]
Furthermore, in the above-described embodiment, the light scattering pattern is formed by partially roughening the exit surface of the light guide plate. However, the present invention is not limited to this, and the light diffusing ink is partially applied. Various formation methods can be widely applied, for example, when a light scattering pattern is formed by simple adhesion.
[0051]
In the above-described embodiment, the case where the light scattering pattern is formed on the exit surfaces of the first and second light guide plates has been described. However, the present invention is not limited to this, and the light scattering pattern is formed on the back surface. Alternatively, the light scattering pattern may be formed on both of the light exit surface and the back surface, and the light scattering pattern may be omitted when practically sufficient characteristics are obtained.
[0052]
Further, in the above-described embodiment, the case where the light guide plate is constituted by the transparent member mixed with the light-transmitting fine particles has been described. However, the present invention is not limited to this, and the transparent material mixed with various light scattering fine particles is described. The light guide plate may be constituted by a member, and further, the light guide plate may be constituted simply by a transparent member without mixing these fine particles.
[0053]
Further, in the above-described embodiment, the case where a plurality of light guide plates made of a plate-shaped member having a wedge-shaped cross section is described. However, the present invention is not limited to this, and is inclined by various processes such as an emission surface. Even when a transparent flat plate-like member that emits illumination light with directivity is laminated, directivity can be formed in a plurality of emission directions, and thus the directivity can be switched as necessary.
[0054]
Further, in the above-described embodiment, the case where the primary light source by one fluorescent lamp is arranged on each of the first and second light guide plates has been described. However, the present invention is not limited to this, as shown in FIG. The primary light source with various light sources can be widely applied, for example, when the primary light source with two fluorescent lamps is arranged.
[0055]
Further, in the above-described embodiment, the case where the surface light source device is configured to have directivity in two directions by laminating two light guide plates each having a primary light source has been described. However, the light guide plates each having a primary light source may be laminated in various numbers. In this connection, as shown in FIG. 11, if four light guide plates each having a primary light source are stacked in different directions, illumination light can be emitted with directivity having peaks in four emission directions.
[0056]
Further, in the above-described embodiment, the case where the prism sheet having the apex angle of 66 degrees is described. However, the present invention is not limited to this, and the apex angle is appropriately selected in the range of 40 degrees or more in the prism sheet. The necessary directivity can be secured. In a car navigation system, for example, viewing is performed by attaching it to a dashboard or the like. In this case, a preferable directivity can be obtained with an apex angle of about 66 degrees as in the above-described embodiment.
[0057]
In the above-described embodiment, the case where the directivity is corrected by the prism sheet has been described. However, the present invention is not limited to this, and the prism sheet may be omitted depending on the required directivity.
[0058]
Furthermore, in the above-described embodiment, the case where the prism sheet is arranged so that the surface opposite to the light guide plate side becomes the prism surface has been described. However, the present invention is not limited to this, and the necessary directivity is provided. If obtained, the prism sheet may be arranged so that the light guide plate side becomes the prism surface.
[0059]
Furthermore, in the above-described embodiment, the case where the directivity is corrected in the in-plane direction orthogonal to the incident surface of the light guide plate by one prism sheet has been described, but the present invention is not limited to this, and the above-described prism is used. A prism sheet may be additionally arranged so that the protrusion repeating direction is orthogonal to the sheet, and the directivity may be further corrected in the in-plane direction along the incident surface of the light guide plate.
[0060]
Further, in the above-described embodiment, a case has been described in which a pair of slopes are directly connected to form a triangular cross-sectional protrusion on the light guide plate and prism sheet. However, the present invention is not limited to this, and a pair of slopes. These protrusions may be formed by connecting them with a curved surface, or the inclined surface itself may be formed with a curved surface.
[0061]
Furthermore, in the above-described embodiment, the case where the slopes of the pair of slopes are set equal in the prism sheet has been described. However, the present invention is not limited to this, and the slopes of the slopes may be varied. If it does in this way, in the above-mentioned 1st Embodiment, the directivity of the illumination light which goes to a driver's seat side and the illumination light which goes to a passenger seat side can be set separately.
[0062]
In the above-described embodiment, the case where the prism sheet and the light diffusion sheet are arranged on the light exit surface side of the upper light guide plate has been described. However, the present invention is not limited thereto, and instead of these, or In addition, a so-called polarization separation sheet that selectively transmits only the illumination light having a predetermined polarization plane and reflects the illumination light may be disposed on the polarization plane in a direction orthogonal to the polarization plane.
[0063]
Furthermore, in the above-described embodiment, the case where the present invention is applied to the liquid crystal display device of the car navigation system has been described. However, the present invention is not limited to this, and is limited to various in-vehicle liquid crystal display devices and further to in-vehicle use. For example, the present invention can be widely applied to various liquid crystal display devices used as displays for personal computers, game machines, etc. and their surface light source devices.
[0064]
【The invention's effect】
As described above, according to the present invention, the plate-like members each having a light source are laminated, and the surface light source device is configured to emit illumination light with directivity by each plate-like member, thereby directing as necessary. Can be obtained, and a liquid crystal display device using the sidelight type surface light source device can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a sidelight type surface light source device applied to a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the side light type surface light source device of FIG.
FIG. 3 is a characteristic curve diagram showing directivity of the first illumination light by the first light guide plate with the prism sheet removed.
FIG. 4 is a characteristic curve diagram showing directivity of second illumination light by a second light guide plate with the prism sheet removed.
FIG. 5 is a characteristic curve diagram showing directivity of the first and second illumination lights by the first and second light guide plates with the prism sheet removed.
FIG. 6 is a cross-sectional view for explaining the operation of the prism sheet with respect to the first and second illumination lights.
FIG. 7 is a characteristic curve diagram showing the directivity of the first illumination light by the first light guide plate.
FIG. 8 is a characteristic curve diagram showing directivity of second illumination light by a second light guide plate.
FIG. 9 is a characteristic curve diagram showing directivity of the first and second illumination lights by the first and second light guide plates.
FIG. 10 is a cross-sectional view showing a sidelight type surface light source device when two fluorescent lamps are arranged in each primary light source.
FIG. 11 is an exploded perspective view showing a sidelight type surface light source device having a configuration in which four light guide plates are laminated.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Side light type surface light source device, 2 ... Liquid crystal display device, 3A, 3B ... Primary light source, 7A, 7B ... Light guide plate, 8 ... Reflection sheet, 9 ... Prism sheet, 11A, 11B ... Fluorescent lamp

Claims (5)

A first plate-like member that enters the first illumination light emitted from the first primary light source from an end surface, bends the first illumination light, and emits the light from the emission surface;
The first illuminating light emitted from the first plate-shaped member and incident on the second illumination light emitted from the second primary light source is disposed to overlap the first plate-shaped member. A second plate-like member that enters the illumination light from the back surface facing the exit surface and emits the first and second illumination lights from the exit surface;
The first plate-shaped member is
A projection formed by a pair of inclined surfaces is repeatedly formed along the end surface on the emission surface and / or the surface facing the emission surface,
The second plate-shaped member is
At least the surface facing the emission surface is formed by a flat surface,
A sidelight type surface light source characterized by having directivity in a first emission direction by the first illumination light and a second emission direction by the second illumination light different from the first emission direction. apparatus. The light control member for correcting the directivity of the illumination light emitted from the emission surface of the second plate member is disposed on the emission surface of the second plate member. The sidelight type surface light source device described. The first plate-shaped member is
The emission surface is formed in a rectangular shape, and the first illumination light is incident from an end surface on the short side of the rectangular shape,
The second plate-shaped member is
3. The side according to claim 1, wherein the emission surface is formed in substantially the same shape as the first plate-like member, and the second illumination light is incident from an end surface on a short side. Light type surface light source device. The liquid crystal display panel is illuminated by the sidelight type surface light source device according to claim 1, claim 2 or claim 3.
A liquid crystal display device characterized by the above. 5. The liquid crystal display device according to claim 4, wherein emission of the first or second illumination light from the first or second primary light source can be selectively stopped .

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