JP6128761B2 - Surface light source device and liquid crystal display device - Google Patents

Description

  The present invention relates to a surface light source device including a light guide plate and a liquid crystal display device including the surface light source device.

  In a non-light emitting display device typified by a liquid crystal display device, a backlight unit (surface light source device) for illuminating the display device is provided on the back surface.

  As the surface light source device provided in the non-light emitting display device, for example, a light source disposed opposite to a side surface (incident surface), a light guide plate that emits incident light from the light source to the surface (exit surface), and a back surface of the light guide plate In order to return the light emitted to the (anti-emission surface) again into the light guide plate, there is known one provided with a reflection plate provided on the side opposite to the emission surface of the light guide plate.

  Also, a backlight unit is provided on the exit surface side of the light guide plate, where necessary, a lens sheet that collects light emitted from the exit surface within a viewing angle to improve brightness, and a diffuser plate that uniformizes brightness. Is also known.

  In recent years, LEDs (Light Emitting Diodes) are increasingly being used as light sources in place of fluorescent lamps in order to achieve further reduction in thickness and life. At present, an edge light type surface light source device in which LED light sources are arranged in a line along the side surface of the light guide plate is mainly used.

  For example, Patent Document 1 proposes a backlight device in which light is reflected by a V-groove formed on a light-exiting surface of a light guide plate and light from an LED light source arranged on a side surface is propagated.

JP 2002-8423 A

  In a surface light source device using an LED as a light source, a hot spot (Hot) that is locally brightened due to the discrete arrangement of light sources and the radiated light of a general LED light source having directional characteristics. (Spot) or the like, luminance unevenness in which the brightness of the display screen becomes uneven is likely to occur.

  Since the luminous efficiency of LED light sources is improving year by year, the number of LED light sources used in one surface light source device tends to decrease. For this reason, the space | interval between the arranged LED light sources spreads, and the dark part formed between LED light sources has become more remarkable. Therefore, the luminance unevenness is more likely to occur.

  In the configuration disclosed in Patent Document 1, a groove having a substantially V-shaped cross section formed in an oblique direction with respect to the traveling direction of light incident from the light source is provided on the light-exiting surface of the light guide plate. Part of the light incident from the light source is reflected and diffused by this substantially V-shaped groove, reaches the dark part between the LED light sources, or directly reaches the light exit surface of the light guide plate, making it difficult to cause uneven brightness. .

  Further, in the vicinity of the side surface where the LED light source is disposed, the substantially V-shaped groove on the non-emission surface is formed to meander. Furthermore, the substantially V-shaped groove on the light-exiting surface is formed deeper as the distance from the side surface on which the LED light source is disposed increases. The amplitude of the meandering of the groove is formed so as to be gradually (narrower) as the distance from the side surface on which the LED light source is disposed.

  By forming in this way, it is possible to adjust the spatial distribution of light emitted from the exit surface of the light guide plate (an index of luminance uniformity within the exit surface).

  In the configuration shown in Patent Document 1, the light emitted from the light exit surface of the light guide plate is totally reflected by the substantially V-shaped groove and directly reaches the light exit surface of the light guide plate. Light that has passed through the groove and reaches the exit surface of the light guide plate through reflection by the reflector disposed on the side opposite to the exit surface.

  Here, the direction of the light reflected by the substantially V-shaped groove formed on the non-light-emitting surface and directly reaching the light-emitting surface of the light guide plate depends on the direction in which the groove is formed. As a result, the direction of light emitted from the exit surface of the light guide plate also depends on the direction in which the substantially V-shaped groove is formed. In the vicinity of the side surface where the LED light source is disposed, the substantially V-shaped groove is meandering, so the direction of light emitted from the exit surface of the light guide plate also meanders.

  The luminance distribution of the light emitted from the exit surface of the light guide plate is adjusted by a substantially V-shaped groove formed on the opposite exit surface of the light guide plate. However, depending on the direction in which the exit surface of the light guide plate is viewed, luminance unevenness occurs.

  Further, if attention is paid to a substantially V-shaped groove formed on the anti-light-emitting surface near the side surface on which the LED light source is disposed, the groove is formed in a meandering manner. The distance from the light source is different. The depth of the groove is formed shallow at a position located in the central axis direction of the main light beam of the LED light source, and the depth of the groove is formed deep at a position away from the central axis direction of the main light beam of the LED light source. Therefore, the processing difficulty at the time of forming a groove | channel also becomes high.

  The present invention has been made to solve the above-described problems, and is a surface light source device having a light guide plate that suppresses uneven luminance of light emitted from the light emission surface of the light guide plate and is easy to form. And a liquid crystal display device having the surface light source device.

A surface light source device according to an aspect of the present invention includes a light guide plate that emits light from an exit surface, a point light source that causes light to enter the light guide plate, and a counter-exit surface side facing the exit surface of the light guide plate. A cross-section viewed from the side of the light guide plate, the light guide plate having grooves formed in a predetermined arrangement corresponding to the point light source on the anti-light-emitting surface. The angle formed between the side surface of the groove and the anti-light-emitting surface of the light guide plate is substantially vertical, and the cross section of the groove viewed from the side surface direction of the light guide plate is orthogonal to the direction in which the groove extends. And adjusting the ratio of the width b of the side surface of the groove and the width a of the bottom surface of the groove in the direction orthogonal to the direction in which the groove extends, thereby reducing the amount of light emitted from the emission surface. wherein the adjustable der Rukoto.
In addition, a surface light source device according to another aspect of the present invention includes a light guide plate that emits light from an emission surface, a point light source that causes light to enter the light guide plate, and a counter-emission that faces the emission surface of the light guide plate. A reflection plate arranged on the surface side, and the light guide plate has grooves formed in a predetermined arrangement corresponding to the point light sources on the anti-light-emitting surface, and viewed from a side surface direction of the light guide plate. In the cross section, the angle formed between the side surface of the groove and the anti-light-emitting surface of the light guide plate is substantially vertical, and the point light source is disposed along with the anti-light-emitting surface of the light guide plate. A principal ray axis from the point light source that has a line-symmetrical arcuate curved surface shape at the position of the exit surface of the light guide plate corresponding to the light source, and the groove is orthogonal to the line-symmetrical symmetry axis In a direction inclined with respect to the principal ray axis. The features.

  A liquid crystal display device according to an aspect of the present invention includes the surface light source device described above and a liquid crystal panel disposed on the emission surface side of the surface light source device.

  According to the above aspect of the present invention, the angle formed between the side surface of the groove and the anti-emission surface of the light guide plate in the cross section when the groove formed on the anti-emission surface is viewed from the side surface direction of the light guide plate. By being substantially vertical, it is possible to suppress luminance unevenness of light emitted from the emission surface by a light guide plate that is easy to form.

It is a perspective view which shows the structure of the surface light source device regarding embodiment of this invention. It is a figure which shows the shape of the groove | channel formed in the anti-light-emitting surface of a light-guide plate. It is a figure which shows the behavior of the light in the groove | channel formed in the opposite light emission surface of a light-guide plate. It is sectional drawing which shows the shape of the groove | channel formed in the reverse emission surface of a light-guide plate. It is sectional drawing which shows the shape of the groove | channel formed in the reverse emission surface of a light-guide plate. It is a figure which shows the general radiation angle distribution of a LED light source. It is a top view which shows angle distribution of the incident light. It is a figure which shows the shape of the groove | channel formed in the anti-light-emitting surface of a light-guide plate. It is a perspective view which shows the structure of the surface light source device regarding embodiment of this invention. It is sectional drawing which shows the shape of the light-guide plate of a surface light source device. It is a figure which shows the behavior of the light in the groove | channel formed in the opposite light emission surface of a light-guide plate.

<First Embodiment>
<Configuration>
FIG. 1 is a perspective view showing a configuration of a surface light source device according to this embodiment of the present invention. The surface light source device is configured as a part of a liquid crystal display device.

  As shown in FIG. 1, the surface light source device includes, for example, a plurality of point light sources 1 such as LED light sources, a light guide plate 2 for propagating light from the point light source 1, and a back surface (reverse side) of the light guide plate 2. In order to evenly diffuse the light from the point light source 1 arranged on the surface (outgoing surface) side of the light guide plate 2 and the reflection plate 3 that reflects the light from the point light source 1 arranged on the (outgoing surface) side. , A vertical prism sheet 5 that changes the direction of collecting light from the point light source 1 disposed on the diffusion plate 4 on the exit surface side of the light guide plate 2, and a vertical prism sheet 5 on the exit surface side of the light guide plate 2. And a horizontal prism sheet 6 that collects light from the point light source 1 and is arranged so as to overlap the prism sheet 5 and changes the direction.

  In FIG. 1, the point light source 1 is embedded in the side surface continuous with the reflection plate 3, but the configuration is not limited to this, and the point light source 1 and the reflection plate 3 are independent of each other. The light guide plate 2 may be disposed.

  The diffusion plate 4 uniformly diffuses the light emitted from the exit surface of the light guide plate 2, but is not provided when the light emitted from the exit surface of the light guide plate 2 is sufficiently evenly diffused. Also good.

  The longitudinal prism sheet 5 has a triangular prism groove formed in a direction orthogonal to the direction in which the point light sources 1 are arranged. The horizontal prism sheet 6 has triangular prism grooves formed in a direction parallel to the direction in which the point light sources 1 are arranged (that is, a direction orthogonal to the direction in which the grooves of the vertical prism sheet 5 are formed).

  Although not shown in FIG. 1, generally, the light emitting plate 2 has a light emitting surface or a light emitting surface formed with a reflector by screen printing or a hemispherical concave (or convex) shape called grain. In other words, the light distribution angle of the light emitted from the light guide plate 2 can be set to an optimum angle. The light emitted from the light guide plate 2 is transmitted through the diffusion plate 4, the vertical prism sheet 5, and the horizontal prism sheet 6 to illuminate a display panel or the like made of a liquid crystal panel (not shown).

  FIG. 2 is a view showing the shape of the groove formed on the opposite light exit surface of the light guide plate 2. Although not shown in FIG. 1, a groove as shown in FIG. 2 is formed on the light exit surface of the light guide plate 2.

  The groove 7a formed on the light-exiting surface of the light guide plate 2 is centered on an axis (principal ray axis 100) indicating the traveling direction of the principal ray of each point light source 1 disposed along the side surface of the light guide plate 2. It is formed symmetrically. Here, the principal ray axis 100 is an axis indicating a main traveling direction of light incident from the respective point light sources 1 in the depth direction of the light guide plate 2. However, the principal ray axis 100 is a convenient axis for defining the arrangement of the light guide plate 2 on the opposite light exit surface where the groove 7a is formed, and the traveling direction of the isotropic light emitted from the point light source 1 is It is not limited to the axis.

  The formation direction of the groove 7 a is inclined with respect to the principal ray axis 100 of each point light source 1 and is curved in a direction away from each point light source 1 as it is away from the principal ray axis 100 of each point light source 1. Is formed.

  Moreover, the groove | channel 7a is formed so that the space | interval of each groove | channel 7a along the advancing direction of the chief ray of the point light source 1 may become narrow as it leaves | separates from the side surface in which the point light source 1 is arrange | positioned.

  The grooves 7a shown in FIG. 2 are shown separately, but each curve may be formed by being smoothly connected. Further, the grooves 7a are formed symmetrically about the principal ray axis 100, but are not necessarily formed as such, and a predetermined arrangement corresponding to the point light source 1 is provided on the anti-light-emitting surface of the light guide plate 2. What is necessary is just to be formed.

  Further, the groove 7 b (groove near the side surface) formed on the opposite light emitting surface of the light guide plate 2 is formed on the opposite light emitting surface near the side surface where the point light source 1 is disposed. The grooves 7b are respectively arranged so as to correspond between the point light sources 1 arranged at a predetermined interval. The groove 7b is formed corresponding to a dark portion between the respective point light sources 1.

<Operation>
Next, the operation of the surface light source device according to this embodiment will be described below with reference to the drawings.

  FIG. 3 is a diagram illustrating the behavior of light in the grooves 7 a and 7 b formed on the light-exiting surface of the light guide plate 2. In FIG. 3, the locus of the light L1 incident from the point light source 1 is indicated by an arrow.

  The groove 7a and the groove 7b have smooth curved surfaces at the end portions in the length direction of the respective groove shapes.

  A part of the light L1 incident on the light guide plate 2 from the point light source 1 is reflected on the side surface of the groove 7a and reaches the groove 7b. Further, a part of the light reaching the groove 7b passes through the side surface of the groove 7b, is reflected by the reflection plate 3 (not shown), and then is emitted from the emission surface of the light guide plate 2.

  FIG. 4 is a cross-sectional view showing the shape of the groove 7 (corresponding to the groove 7 a and the groove 7 b) formed on the light-exiting surface of the light guide plate 2. FIG. 4 is a view seen from the side surface direction of the light guide plate 2.

  In FIG. 4, the light L2 incident on the upper portion (the deep portion of the groove 7; the upper side surface) of the side surface 7y of the groove 7 and the light incident on the lower portion (the shallow portion of the groove 7; the lower side surface) of the side surface 7y of the groove 7. Each behavior will be described in detail by dividing it into L3.

  Both the light L2 incident on the upper side surface of the side surface 7y and the light L3 incident on the lower side surface of the side surface 7y are separated into reflected light and transmitted light in accordance with Fresnel law.

  The light L2 and the light L3 reflected by the side surface 7y are further reflected by the anti-light-emitting surface of the light guide plate 2 and propagate again toward the side surface of the light guide plate 2 on which the point light source 1 is disposed.

  On the other hand, the light L2 transmitted through the upper side surface of the side surface 7y is once emitted into the atmosphere (inside the groove 7) and then incident again into the light guide plate 2 from the other side surface 7y. It is reflected by the surface and propagates to the side surface side of the light guide plate 2 opposite to the side surface on which the point light source 1 is disposed.

  In addition, the light L3 transmitted through the lower side surface of the side surface 7y is emitted into the atmosphere (from the inside of the groove 7 to the outside of the light-exiting surface of the light guide plate 2), and is diffusely reflected by the reflecting plate 3. Of the diffusely reflected light L3, only the light that enters the light guide plate 2 again from the bottom surface 7x of the groove 7 formed on the opposite exit surface of the light guide plate 2 becomes light emitted from the output surface of the light guide plate 2. .

  The light that is diffusely reflected by the reflecting plate 3 and enters the light guide plate 2 again from the side surface 7 y is propagated to the side surface side of the light guide plate 2.

  Here, the light transmitted through the side surface 7y of the groove 7 and diffusely reflected by the reflecting plate 3 is incident on the bottom surface 7x or the side surface 7y of the groove 7 when returning to the light guide plate 2 again. The subsequent propagation direction of the light returning into the light guide plate 2 is affected by the occupation ratio between the light and the side surface 7y.

  If the width of the groove 7, that is, the width of the bottom surface 7x is a width a, and the depth of the groove, that is, the vertical width of the side surface 7y is a width b, the ratio of the light reflected by the side surface 7y is increased. When it is desired to increase the ratio of propagating the transmitted light to the side surface side of the light guide plate 2, the b / a ratio is increased, and when the ratio of returning the light returned into the light guide plate 2 to the output surface of the light guide plate 2 is increased. It can be seen that the b / a ratio should be reduced.

  That is, by adjusting the b / a ratio in each groove, the amount of light emitted from the light exit surface of the light guide plate 2 can be adjusted. For example, the b / a ratio can be increased in the groove 7a shown in FIG. 3, and the b / a ratio can be decreased in the groove 7b. Further, the b / a ratio can be reduced as the distance from the point light source 1 increases. In addition, when increasing the ratio of light emitted from the exit surface of the light guide plate 2 in the groove 7b, it is desirable to reduce the interval between the grooves 7b.

  In FIG. 4, the cross section of the groove 7 is shown as a rectangular shape, but the side surface 7 y is on the opposite side of the light guide plate 2 so that the light reflected by the side surface 7 y does not directly come out from the output surface of the light guide plate 2. It may be inclined with respect to it. That is, the angle between the side surface 7y and the light exit surface of the light guide plate 2 may be substantially vertical. More specifically, if the angle between the side surface 7y and the light exit surface of the light guide plate 2 is α, a material having a refractive index of about 1.5 such as PMMA (Polymethyl methacrylate) may be used for the light guide plate 2. For example, α can be adjusted in the range of 80 to 90 °.

  Specifically, it can be explained as follows.

  FIG. 5 is a cross-sectional view showing the shape of the groove 7 (corresponding to the groove 7 a and the groove 7 b) formed on the light-exiting surface of the light guide plate 2. FIG. 5 is a view as seen from the side of the light guide plate 2.

The contact angle of the angle α side 7y of the groove 7 with respect to anti-emitting surface of the light guide plate 2, consider the case where light is incident at the maximum incident angle theta _c from the side surface of the light guide plate 2. This maximum incident angle θ _c is an angle corresponding to the refractive index of the light guide plate 2 of light incident at an incident angle of approximately 90 ° with respect to the side surface of the light guide plate 2. When the refractive index of the light guide plate 2 is 1.5, the maximum incident angle θ _c is about 42 °. If the material has a high refractive index such as polycarbonate (refractive index 1.59), the maximum incident angle θ _c is about 40 °.

The incident light is totally reflected by the light exit surface of the light guide plate 2 and then enters the side surface 7y at an angle β. In this case, the _{β = 90-α + θ c} . The light incident on the side surface 7y is, the maximum incident angle in the case of transmitting the side 7y is beta = theta _c, i.e., an alpha = 90.

  In order to eliminate the light totally reflected by the groove 7, the side surface 7 y of the groove 7 must be perpendicular to the anti-light-emitting surface of the light guide plate 2.

  However, considering the case where the light guide plate 2 is actually processed, the angle α is generally set to an angle smaller than 90 ° (in order to facilitate die cutting after injection molding). The angle range of the angle α may be 85 to 90 °.

  Thus, in order to estimate the total amount of reflected light when the side surface 7y of the groove 7 is tapered, the radiation angle distribution of the original point light source must be considered. In general, the radiation angle distribution of an LED light source as a point light source has a Gaussian distribution as shown in FIG. Here, FIG. 6 is a diagram showing a general radiation angle distribution of the LED light source, where the horizontal axis represents the radiation angle (°) and the vertical axis represents the relative light quantity.

  As shown in FIG. 6, the amount of light included in the radiation angle of 80 to 90 ° is about 1.3% of the total amount of light. Of the 1.3% light, the proportion of light incident on the groove 7 is considered to be approximately proportional to the ratio of the thickness of the light guide plate 2 to the height of the groove 7. In the embodiment, the height of the groove 7 is 0.2 mm and the width of the groove 7 is 0.1 mm with respect to the thickness 2 mm of the light guide plate 2. That is, the light is incident on the side surface 7y of the groove 7 with a probability of 1/10, and 0.13% is emitted from the exit surface of the light guide plate 2 in 1/10 of 1.3%. . Since the amount of light extracted in this process does not exceed 0.6%, it seems that there is no practical problem.

  In the embodiment, in the light guide plate 2 having a thickness of 2 mm, a region having a high light density is generated downstream from the side surface of the light guide plate 2 along the principal ray axis by 5 mm to 10 mm. It is preferable to form a pattern of grooves 7 on the emission surface.

When the grooves 7 are formed in this way, the angle of light incident on the grooves 7 is distributed in the range of 3 to 36 ° in the vertical direction and in the range of 30 to 18 ° in the horizontal direction (see FIG. 7). When the minimum incident angle θ _c is 19 °, 5% of light is reflected by the groove 7 in PMMA, and when the maximum incident angle θ _c is 45 °, 100% of light is grooved in PMMA. 7 is reflected.

  Thereafter, the width, length, and width b / width a of the groove 7 are adjusted as appropriate so that the light emitted from the exit surface of the light guide plate 2 becomes uniform by statistical ray tracing processing. However, if the width of the groove 7 exceeds 0.4 mm, it is not preferable because it becomes visible as a bright line.

  In this manner, by forming the groove 7 on the opposite light exit surface of the light guide plate 2, it is possible to improve the probability that light emitted from the light exit surface of the light guide plate 2 passes through the reflection plate 3. Since the light diffusely reflected by the reflecting plate 3 has no directivity in the light distribution angle, the luminance distribution of the light emitted from the emitting surface of the light guide plate 2 can be made uniform.

<Effect>
According to the embodiment of the present invention, the surface light source device includes a light guide plate 2 that emits light from the emission surface, a point light source 1 that causes light to enter the light guide plate 2, and a surface that is opposite to the emission surface of the light guide plate 2. And a reflector 3 disposed on the exit surface side.

  The light guide plate 2 has grooves 7 formed in a predetermined arrangement corresponding to the point light source 1 on the light-exiting surface, and the side surface 7 y of the groove 7 and the light guide plate in a cross section viewed from the side surface direction of the light guide plate 2. The angle formed by the counter-exiting surface 2 is substantially vertical, more preferably 80 to 90 °.

  According to such a surface light source device, the light guide plate 2 that can be easily formed can suppress uneven brightness of the light emitted from the emission surface.

  Specifically, a part of the light reaching the groove 7 is reflected in the side surface direction of the light guide plate 2, so that the light exit surface of the light guide plate 2 is disposed through the reflector 3 disposed on the back side of the light guide plate 2. The light is emitted from.

  Therefore, it can suppress that the light radiate | emitted from the output surface of the light-guide plate 2 has the light distribution angle depending on the formation direction of a groove | channel, and can suppress the brightness nonuniformity of light.

  In the case where a reflector or wrinkle by screen printing is formed on the light-exiting surface of the light guide plate 2, light is emitted from the light emission surface of the light guide plate 2 using reflection of light from the reflector or wrinkle. Can do.

  Further, according to the embodiment of the present invention, the point light source 1 is disposed along the side surface of the light guide plate 2, and the groove 7 a is on the principal ray axis that extends from the point light source 1 to the depth direction of the light guide plate 2. It forms a symmetrical pair and is tilted with respect to the principal ray axis.

  According to such a configuration, the light reflected by the groove 7a is efficiently propagated to the dark part formed in the region deviated from the principal ray axis of the point light source 1, so that the luminance unevenness of the light is suppressed. The

  Further, according to the embodiment of the present invention, the cross section of the groove 7 viewed from the side surface direction of the light guide plate 2 is rectangular, and the ratio between the width a of the bottom surface 7x of the groove 7 and the width b of the side surface 7y of the groove 7 is. Is adjustable.

  According to such a configuration, the amount of light emitted to the exit surface of the light guide plate 2 via the reflector 3 in each groove 7 can be adjusted, so that, for example, depending on the location where the groove 7 is formed The amount of light emitted can be adjusted. Therefore, uneven brightness of light can be suppressed.

  Further, according to the embodiment relating to the present invention, the plurality of grooves 7 are formed in the direction away from the point light source 1, and the value of width b / width a decreases as the distance from the point light source 1 increases.

  The amount of light that enters from the point light source 1 reaches each groove 7 decreases as the distance from the point light source 1 increases. In view of this, the above configuration increases the proportion of light emitted from the exit surface of the light guide plate 2 via the reflector 3 in each groove 7 as the distance from the point light source 1 increases. it can.

  Therefore, even if the distance from the point light source 1 is increased, it is possible to suppress the amount of light emitted from the groove 7 from being reduced, and it is possible to suppress uneven luminance of light.

  Further, according to the embodiment of the present invention, a plurality of grooves 7 are formed in the direction away from the point light source 1, and the interval between the grooves 7 becomes narrower as the distance from the point light source 1 increases.

  According to such a configuration, in consideration of the fact that the amount of light reaching each groove decreases as the distance from the point light source 1 increases, the groove 7 that emits light from the exit surface of the light guide plate 2 is formed. By narrowing the interval to be formed, the luminance unevenness of light can be suppressed.

  In addition, according to the embodiment of the present invention, the groove 7b is further provided as a side surface vicinity groove formed in the vicinity of the side surface of the light guide plate 2 between the plurality of point light sources 1 on the opposite emission surface of the light guide plate 2. .

  According to such a configuration, the light guide plate 2 having an easy structure including only the grooves 7a and the grooves 7b can suppress luminance unevenness of light emitted from the emission surface. Even if other reflectors are not formed, luminance unevenness can be sufficiently suppressed, and a separate processing step for forming other reflectors is not required.

Second Embodiment
<Configuration>
FIG. 8 is a diagram showing a groove shape formed on the light-exiting surface of the light guide plate 2a of the surface light source device according to this embodiment of the present invention. In addition to the groove 7a, a dark portion 9 near the side surface of the light guide plate 2 on which the point light source 1 is arranged is shown. The same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Similar to the first embodiment, the grooves 7 a formed on the light-exiting surface of the light guide plate 2 a are formed symmetrically about the principal ray axis 100 of the point light source 1. The formation direction of the groove 7 a is inclined with respect to the principal ray axis 100 of each point light source 1 and is curved in a direction away from each point light source 1 as it is away from the principal ray axis 100 of each point light source 1. Is formed.

  In the present embodiment, the light from each point light source 1 reflected on the side surface of the groove 7 a is propagated to the dark part 9 adjacent to each point light source 1. The propagated light is emitted from the exit surface of the light guide plate 2a through the bottom surface 7x of the groove 7a, and is formed on the opposite exit surface of the light guide plate 2a, a reflector by screen printing or the like (not shown). And is emitted from the exit surface of the light guide plate 2a. In the groove 7a, the propagation of light to the side surface side of the light guide plate 2a is promoted, and emission from the exit surface of the light guide plate 2a can be performed by a textured body or a reflector by screen printing.

  In the case of forming the structure of the anti-light-emitting surface with only the groove, it is necessary to adjust the groove width and aspect ratio (value of width b / width a) depending on the position of the groove, and the groove forming process becomes complicated. . In the present embodiment, the groove processing step can be simplified by limiting the role of the groove 7 only to reflect light to the dark part between the point light sources. The process of adjusting the emitted brightness by embossing or screen printing is a conventional technique, and the process itself can be easily performed.

<Third Embodiment>
<Configuration>
FIG. 9 is a perspective view showing the configuration of the surface light source device according to this embodiment of the present invention. The surface light source device is configured as a part of a liquid crystal display device. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 9, the surface light source device includes, for example, a light guide plate 2b for propagating light, a plurality of point light sources 1b disposed along the opposite light emitting surface of the light guide plate 2b, and the light guide plate 2b. Reflector 3 for reflecting the light from the point light source 1b arranged on the side opposite to the light emitting surface, and diffusion for uniformly diffusing the light from the point light source 1b arranged on the light emitting surface side of the light guide plate 2b A plate 4, a vertical prism sheet 5 that changes the direction of collecting light from the point light source 1b disposed on the diffusion plate 4 on the exit surface side of the light guide plate 2b, and a vertical prism sheet on the exit surface side of the light guide plate 2b And a horizontal prism sheet 6 that collects the light from the point light source 1b that is arranged so as to overlap the direction 5 and changes the direction.

  A curved surface shape 22 is formed on the exit surface of the light guide plate 2b. Details will be described later.

<Operation>
The operation of the surface light source device according to this embodiment will be described below with reference to the drawings.

  FIG. 10 is a cross-sectional view showing a curved surface shape 22 formed on the exit surface of the light guide plate 2b. In addition, FIG. 10 is the figure seen from the side surface direction of the light-guide plate 2b. In FIG. 10, the trajectory of the light emitted from the point light source 1b is indicated by an arrow.

  In FIG. 10, a part of the point light source 1 b is arranged in the recessed shape 21 formed on the opposite light emitting surface of the light guide plate 2 b. The concave shape 21 is formed so as to extend in the depth direction of the paper surface in FIG. 10, and is formed so as to cover the plurality of point light sources 1b arranged in the depth direction of the paper surface in FIG.

  The curved surface shape 22 formed on the exit surface of the light guide plate 2b is an arc-shaped curved surface that is axisymmetric with respect to an axis extending in the depth direction of the paper surface.

  The light emitted from the point light source 1b is incident on the light guide plate 2b from the concave shape 21 on the light exit surface of the light guide plate 2b, and all of the light is totally reflected on the curved surface shape 22 formed on the output surface of the light guide plate 2b. Is propagated in the light guide plate 2b.

  The light isotropically emitted from the point light source 1b is distributed in the left-right direction in FIG. In FIG. 10, the light L4 is distributed to the left in FIG. 10, and the light L5 is distributed to the right in FIG.

  Here, for example, the light emitted from the point light source 1b while being inclined in the depth direction of the paper in FIG. 10 is also distributed to either the left or right direction in FIG. Therefore, an area where the light from the point light source 1b cannot reach occurs in the depth direction in FIG.

  FIG. 11 is a diagram illustrating the behavior of light in the groove 7c formed on the light-exiting surface of the light guide plate 2b. FIG. 11 is a view of the light guide plate 2b as viewed from the side opposite to the light exit surface. In FIG. 11, the shape of the groove 7c formed on the light-exiting surface of the light guide plate 2b and the dark part 9b, which is an area where the light from the point light source 1b cannot reach, are shown. The dark portion 9b shown in FIG. 11 exists between the arranged point light sources 1b.

  In order to allow the light from the point light source 1b to reach the dark portion 9b, a groove 7c is formed on the light-exiting surface of the light guide plate 2b. The grooves 7 c are formed symmetrically about an axis (principal ray axis 101) indicating the traveling direction of the principal ray of each point light source 1 b arranged on the opposite light exit surface of the light guide plate 2 b. The groove 7 c is formed in a direction inclined with respect to the principal ray axis 101. Here, the principal ray axis 101 is an axis that passes through each point light source 1 b on the light-exiting surface of the light guide plate 2 b, and is an axis that is orthogonal to the symmetry axis of the curved surface shape 22. The axis indicates the main traveling direction of light when the light emitted from each point light source 1b is reflected on the curved surface shape 22 (see FIG. 10) and reaches the opposite light emitting surface of the light guide plate 2b again. It is.

  The grooves 7c are formed symmetrically about the principal ray axis 101, but are not necessarily formed as such, and are formed corresponding to the point light sources 1b on the anti-light-emitting surface of the light guide plate 2b. It only has to be.

  In FIG. 11, a groove 7 c is formed in the direction in which the light L <b> 6 that has entered from the concave shape 21 and reached the opposite exit surface of the light guide plate 2 b through the curved shape 22 travels (the direction of the principal ray axis 101). Yes. The groove 7c has such a curved shape that the light L6 reflected by the side surface of the groove 7c is condensed on the dark portion 9b.

  In FIG. 11, the groove 7c formed on the light-exiting surface of the light guide plate 2b reflects the light from the point light source 1b and propagates it to the dark part 9b. When light propagating through the light guide plate 2b is emitted to the exit surface of the light guide plate 2b, a texture formed on the opposite exit surface, a reflector by screen printing, or the like (not shown) is used. However, it may be the case where only the groove 7c is formed without forming the above-described reflector or the like on the opposite light emitting surface of the light guide plate 2b.

<Effect>
According to the embodiment of the present invention, the point light source 1b is arranged along with the opposite light exit surface of the light guide plate 2b, and a line-symmetric circle is provided at the position of the light exit surface of the light guide plate 2b corresponding to the point light source 1b. An arcuate curved surface shape 22 is provided, and the groove 7c forms a symmetric pair with the principal ray axis from the point light source 1b perpendicular to the line-symmetric symmetry axis and is inclined with respect to the principal ray axis. Is formed.

  According to such a configuration, the light reflected by the groove 7c is efficiently propagated to the dark portion 9b formed in the area deviated from the principal ray axis of the point light source 1b. Is done.

  Moreover, according to embodiment regarding this invention, the point light source 1b is partially stored in the recessed shape 21 formed in the opposite radiation | emission surface of the light-guide plate 2b.

  According to such a configuration, the light from the point light source 1b can be efficiently guided into the light guide plate 2b, and the amount of light emitted from the exit surface of the light guide plate 2b can be increased.

  In addition, within the scope of the present invention, the present invention can be freely combined with each embodiment, modified with any component in each embodiment, or omitted with any component in each embodiment.

  1, 1b Point light source, 2, 2a, 2b Light guide plate, 3 Reflector plate, 4 Diffuser plate, 5 Vertical prism sheet, 6 Horizontal prism sheet, 7, 7a, 7b, 7c Groove, 7x Bottom surface, 7y Side surface, 9, 9b Dark portion, 21 dent shape, 22 curved surface shape, 100, 101 principal ray axis.

Claims (10)

A light guide plate for emitting light from the emission surface;
A point light source for making light incident on the light guide plate;
A reflection plate disposed on the side opposite to the emission surface of the light guide plate facing the emission surface;
The light guide plate has grooves formed in a predetermined arrangement corresponding to the point light sources on the anti-light-emitting surface;
In the cross section viewed from the side surface direction of the light guide plate, the angle formed by the side surface of the groove and the anti-light-emitting surface of the light guide plate is substantially vertical,
The cross section of the groove viewed from the side surface direction of the light guide plate and orthogonal to the direction in which the groove extends is rectangular,
By adjusting the ratio between the width b of the side surface of the groove and the width a of the bottom surface of the groove in the direction perpendicular to the direction in which the groove extends, the amount of light emitted from the emission surface can be adjusted. and wherein the Rukoto Oh,
Surface light source device. The point light source is disposed along the side surface of the light guide plate;
The groove is formed in a direction symmetrical to the principal ray axis from the point light source toward the depth direction of the light guide plate and inclined with respect to the principal ray axis. ,
The surface light source device according to claim 1. A plurality of the point light sources are arranged in association with the side surface of the light guide plate,
In the vicinity of the side surface of the light guide plate between a plurality of the point light sources, further comprising a side surface vicinity groove on the anti-emission surface,
The surface light source device according to claim 2. A light guide plate for emitting light from the emission surface;
A point light source for making light incident on the light guide plate;
A reflection plate disposed on the side opposite to the emission surface of the light guide plate facing the emission surface;
The light guide plate has grooves formed in a predetermined arrangement corresponding to the point light sources on the anti-light-emitting surface;
In the cross section viewed from the side surface direction of the light guide plate, the angle formed by the side surface of the groove and the anti-light-emitting surface of the light guide plate is substantially vertical,
The point light source is disposed along the anti-light-emitting surface of the light guide plate;
At the position of the exit surface of the light guide plate corresponding to the point light source, has a line-symmetric arc-shaped curved surface shape,
The grooves are formed in a direction symmetrical to the principal ray axis from the point light source orthogonal to the line symmetry symmetry axis and inclined with respect to the principal ray axis. And
Surface light source device. The point light source is partially stored in a recessed shape formed on the anti-light-emitting surface of the light guide plate,
The surface light source device according to claim 4. A plurality of the grooves are formed in a direction away from the point light source;
The value of the width b / the width a decreases as the distance from the point light source decreases.
The surface light source device according to claim 1. A plurality of the grooves are formed in a direction away from the point light source;
An interval between the grooves is narrowed as the distance from the point light source is increased.
The surface light source device according to claim 1. In at least one of the light exit surface and the light exit surface of the light guide plate, the light guide plate further comprises a plurality of hemispherical concave or convex shapes,
The surface light source device according to claim 1. A reflector is printed on at least one of the light exit surface and the light exit surface of the light guide plate,
The surface light source device according to claim 1. A surface light source device according to any one of claims 1 to 9,
A liquid crystal panel disposed on the emission surface side of the surface light source device,
Liquid crystal display device.

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