JP2012209034A - Light source module and liquid crystal display having this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source module in which expansion of light in a straight advancing direction (longitudinal direction) and in a perpendicular direction (short-length direction) is suppressed.SOLUTION: The light source module is provided with a light guide plate 20, an LED 12 from which light is entered at least from one end face in longitudinal direction of the light guide plate 20, and a light diffusion structure group 20b which is located at the lower face 20c on the opposite side to the light emitting surface 20d of the light guide plate 20 and takes out light guided inside the light guide plate 20. Then, the light source module has a plurality of curved structure parts 20a which are constituted of curved surfaces having a ridgeline in longitudinal direction on the light-emitting surface 20d of the light guide plate 20.

Description

  The present invention relates to a light source module and an electronic apparatus including the same, and more specifically, for example, in a liquid crystal display device, a side edge that emits light from a light source in a planar shape by a light guide plate in order to reduce the thickness. The present invention relates to a light source module used for a backlight including a type light guide plate (also referred to as a side light), and an electronic apparatus including the light source module.

  In recent years, in order to reduce the thickness of a liquid crystal display device, a backlight including a side edge type light guide plate that emits light from a light source in a planar shape by the light guide plate is frequently used.

  As such a side edge type light guide plate, for example, there is a planar illumination device disclosed in Patent Document 1. FIG. 7 is a diagram showing the planar illumination device of Patent Document 1. As shown in FIG. As shown in FIG. 7, in the planar illumination device 100 of Patent Document 1, a prismatic structure is formed on the main surface of the light guide plate 101. A plurality of LED light sources 102 are provided in the vicinity of the end surface 111 orthogonal to the main surface. Here, when only one light source 102 a of the plurality of LED light sources 102 is turned on by the selective lighting means, the light incident from the end surface 111 of the light guide plate 101 is a prism-like structure provided on the main surface of the light guide plate 101. Due to the action of the body, the light propagates in the left direction in FIG. 7 while hardly spreading in the vertical direction in FIG. 7, and a strip-shaped illumination region 103 is formed.

  FIG. 8 is a cross-sectional view showing the configuration of the prismatic structure 110 in the planar illumination device of Patent Document 1. As shown in FIG. As shown in FIG. 8, in the cross section of the light guide plate 101, light incident at an angle θ with respect to one surface of the prism surface with respect to the flat surface is totally reflected and incident on the opposing prism surface. reflect. And it injects into a flat surface with cross-sectional angle (phi). At this time, φ = θ. In the planar illumination device of Patent Document 1, in order to obtain planar illumination, a dot-like white reflecting surface or the like is formed on a flat surface and illuminated uniformly.

  Further, for example, Patent Document 2 discloses a configuration in which a V-groove is formed on the surface opposite to the exit surface of the light guide plate.

JP 2009-283383 A (released on December 3, 2009) JP 2009-31445 A (published February 12, 2009)

  However, the planar illumination device of Patent Document 1 has the following problems.

  That is, the prismatic structure 110 in the planar illumination device of Patent Document 1 has an extremely high confinement effect for confining light in the light guide plate for light having an angle θ of a specific angle. However, the confinement effect is not exerted on the light C incident at a shallow angle (the angle θ with the flat surface is small). The light C incident at a shallow angle has a large spread in the straight direction (longitudinal direction of the light guide plate) and the vertical direction (short direction of the light guide plate). For this reason, as shown in FIG. 8, the component of light C that is reflected in the direction directly below the prism surface outside the illumination region 103 increases. Then, the component reflected in the direction directly below the prism surface is scattered on the flat surface and emitted from the prismatic structure 110. As a result, the light C incident at a shallow angle (the angle θ with the flat surface is small) may be emitted from a position shifted from the illumination region 103.

  As described above, in the light guide plate having the conventional configuration, light incident at a shallow angle is emitted from an area outside the irradiation area 103 where light should be emitted. As a result, there is a problem that the illumination area 103 extends in a direction (short direction) perpendicular to the straight light traveling direction (longitudinal direction).

  The present invention has been made in view of the above-described conventional problems, and an object thereof is a light source module capable of suppressing the spread of light in a direction (longitudinal direction) perpendicular to a straight traveling direction (longitudinal direction). And providing an electronic apparatus including the same.

  In order to solve the above-described problems, the light source module of the present invention includes a light guide plate, a plurality of light sources that allow light to enter from at least one end face in the longitudinal direction of the light guide plate, and a light emission surface of the light guide plate. A light source module including a plurality of light path conversion units having light diffusibility for extracting light guided inside the light guide plate on a surface opposite to the light guide plate, the light emission surface of the light guide plate It has a plurality of curved surface structure parts composed of curved surfaces having ridge lines in the longitudinal direction.

  According to said structure, it has multiple curved surface structure parts comprised by the curved surface which has a ridgeline in a longitudinal direction in the light emission surface in the said light-guide plate. That is, the plurality of curved surface structure portions are formed along the longitudinal direction. On the other hand, on the surface opposite to the light exit surface of the light guide plate, a plurality of light path conversion portions having light diffusibility for taking out light guided inside the light guide plate is formed. In the optical path conversion unit, it is possible to convert the angle component of the light beam guided in the light guide and to emit the light beam that breaks the total reflection condition in the longitudinal direction and the short direction from the light guide. The curved surface structure portion has a curved surface whose surface shape is continuously changed with respect to the short side direction. Therefore, light whose optical path has been converted by the optical path converter can be extracted efficiently from light with various angular components in the short direction when the total reflection condition is broken in the longitudinal direction. It is. Further, when the total reflection condition is not broken in the longitudinal direction, there is no emission from the light guide, and it is possible to suppress the spread of light in the short direction.

  In the light source module of the present invention, it is preferable that the interval between the optical path conversion portions is larger than the interval between the ridge lines.

  According to said structure, since the space | interval of the said optical path conversion part is larger than the space | interval of the said ridgeline, formation of an optical path conversion part becomes easy, and the positional accuracy of the optical path conversion part with respect to the curved surface structure is eased. effective.

  In the light source module of the present invention, it is preferable that the optical path changing portion is formed of ink containing a light diffusing member by screen printing.

  According to said structure, the directivity of the longitudinal direction component of a light ray can be eased, and the effect which suppresses the spreading of light can be improved with respect to a short direction component.

  In order to solve the above problems, an electronic apparatus according to the present invention includes the above-described light source module.

  According to said structure, the electronic device which can suppress the spreading to the perpendicular | vertical direction (longitudinal direction) of light to a perpendicular | vertical direction is realizable.

  In the present invention, the curved surface structure portion has a height H and the interval between the curved surface structures is P, and the curved surface structure is formed to satisfy a relationship of 0.2 <H / P <0.5. It is preferable.

  According to the above configuration, the curved surface structure portion has the tangent slope continuously changing. Therefore, it works effectively in terms of the effect of extracting light incident on the exit surface at various angles and the effect of suppressing the spread of light in the short direction. In addition, by setting H / P within the above range, there are effects that it is possible to improve the production efficiency during mass production of the curved surface structure and to suppress fluctuations in characteristics with respect to shape deviation.

  The light source module of the present invention preferably includes a light source control unit that selectively turns on the plurality of light sources.

  According to said structure, the light source control part which selectively lights up the said several light source is provided. Therefore, for example, when applied to a liquid crystal display device as an electronic device, the light source control unit selectively fixes the light source so that an area corresponding to the video signal is illuminated in synchronization with vertical scanning within one frame in the video signal. When the light is turned on for a long time, only a specific part of the light guide plate can be appropriately blinked to improve the moving image characteristics.

  As described above, the light source module of the present invention is characterized in that it has a plurality of curved surface structure parts constituted by curved surfaces having ridge lines in the longitudinal direction on the light emission surface of the light guide plate. Moreover, the electronic device of this invention is the structure provided with the said light source module as mentioned above.

  Therefore, it is possible to suppress the spread of light in the direction (longitudinal direction) perpendicular to the straight traveling direction (longitudinal direction) and to obtain the effect of not impairing the extraction efficiency.

The schematic structure of the light source module of this invention is shown, (a) is a top view, (b) is a side view. It is a disassembled perspective view which shows the structure of the liquid crystal display device provided with the said light source module. It is sectional drawing which shows a part of structure in a liquid crystal display device provided with the said light source module. The diffusion image of a light diffusing material (scattering body) is shown, the left side is a schematic diagram showing scattering characteristics on the xz plane, and the right side is a schematic diagram showing scattering characteristics on the yz plane. The relationship between the presence or absence of a semi-cylindrical curved surface structure on the light guide plate and the illuminance distribution on the exit surface is shown. (A) is a two-dimensional illumination on the exit surface when the light guide plate has a curved structure. (B) shows a two-dimensional illuminance distribution on the exit surface when the light guide plate has no curved structure, and (c) shows the light guide plate for the configurations of (a) and (b). It is the graph which showed the illumination intensity distribution of the Y direction in the center part. It is sectional drawing which shows the relationship between the path | route of the light which guides the inside of a light-guide plate, and the presence or absence of a curved-surface structure, (a) is a case where a curved-surface structure is formed in the output surface of a light-guide plate (Example). (B) shows a case in which a prism with an apex angle of 90 ° is formed on the exit surface of the light guide plate (conventional example 1), and (c) shows a prism with an apex angle of 5 ° on the exit surface of the light guide plate. Is shown (conventional example 2), and (d) shows a case where the shape of (a) is a concave cylinder. It is a side view which shows the side shape of the X direction in a light-guide plate, (a) shows the case where the height of a curved-surface structure is small, (b) shows the case where the height of a curved-surface structure is large. When the height H of the curved surface structure 20a as the configuration A is small as shown in FIG. 7A and when the height H of the curved structure 20a as the configuration B as shown in FIG. 7B is small. It is a figure which shows the illumination intensity distribution of the Y direction in the center part of a light-guide plate, respectively. It is a figure explaining backlight blinking. In this invention, it is a figure which shows the confinement effect of the light ray by the curved-surface structure in case the total reflection conditions are not destroyed with respect to the light guide direction. It is a top view which shows the other modification of the light-guide plate in the said light source module. It is a top view which shows local lighting with the light-guide plate in the said light source module.

  One embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is an exploded perspective view of a liquid crystal display device (electronic device) including the light source module of the present embodiment.

  For example, a liquid crystal display device 1 as an electronic apparatus including the light source module 10 according to the present embodiment includes a chassis 2, a light source module 10, a liquid crystal panel 3, and a bezel 4 in order from the bottom as shown in FIG. The light source module 10 includes a reflection sheet 11 as a reflection plate, an LED (Light Emitting Diode) 12 and a LED substrate 13 as a light source, a reflector 14, a light guide plate 20, a diffusion plate 15, and an optical sheet group 16. It is composed of The diffusion plate 15 and the optical sheet group 16 can be omitted depending on the application.

  FIG. 3 is a cross-sectional view illustrating a partial configuration of the liquid crystal display device 1 including the light source module 10. As shown in FIG. 3, the LED 12, the LED substrate 13, and the reflector 14 are provided at the end portion of the light guide plate 20, so that light from the LED 12 is incident on one end surface 21 a of the light guide plate 20 and guided. The liquid crystal panel 3 is irradiated with light from the exit surface 20 d of the light plate 20 through the diffusion plate 15 and the optical sheet group 16. Therefore, the light source module 10 of the present embodiment employs a side edge (also referred to as side light) method. The light guide plate 20 also partially emits light from surfaces other than the exit surface 20d, but the reflective sheet 11 is disposed on a surface other than the exit surface 20d of the light guide plate 20 and the surface on which the LEDs 12 are disposed. Since the light enters the light guide plate 20 again, most of the light is emitted from the emission surface 20d.

  Here, the longitudinal direction of the light guide plate 20 is the X direction, the normal direction of the light guide plate 20 is the Z direction, and the direction perpendicular to the X direction and the Z direction is the Y direction. The Y direction may be described as a short direction with respect to the longitudinal direction (X direction) of the light guide plate 20.

  FIG. 1 shows a schematic configuration of a light source module 10 according to the present embodiment, FIG. 1 (a) is a top view, and FIG. 1 (b) is a side view. As shown in FIGS. 1A and 1B, LEDs L <b> 1 to L <b> 5 and LEDs R <b> 1 to R <b> 5 are arranged as LEDs 12 that allow light to enter from both ends in the longitudinal direction of the light guide plate 20. The LEDs L1 to L5 are disposed so as to face the LEDs R1 to R5 in the longitudinal direction, respectively.

  Although not shown in FIGS. 1A and 1B, the light source module 10 includes a light source control unit that selectively lights the LEDs L1 to L5 and LEDs R1 to R5. This light source control part can also be controlled to turn on all the light sources of LEDs L1 to L5 and LEDs R1 to R5.

  In addition, a curved surface structure 20 a formed of a curved surface is formed on the exit surface (upper surface) 20 d of the light guide plate 20. The curved surface structure 20 a is formed as a streak pattern along the longitudinal direction (X direction) of the light guide plate 20. In other words, the light guide plate 20 has a plurality of curved surface structure parts formed of curved surfaces having ridge lines in the longitudinal direction on the light emission surface 20d. The curved structure 20a is a structure formed on the light exit surface 20d itself of the light guide plate 20 (a structure formed on the light guide plate 20 itself), and the light guide plate 20 is a member different from the light guide plate 20. A curved structure member is not provided.

  In the present embodiment, the curved surface structure 20a formed on the light guide plate 20 is formed with a height H and a distance between the curved surface structure portions P, and the curved surface structure is 0.2 <H / P <. It is formed with a structure satisfying 0.5.

  On the other hand, as shown in FIG. 1B, a light diffusing structure group 20b is formed on the lower surface 20c of the light guide plate 20 opposite to the curved structure 20a as an optical path changing unit.

  The light diffusion structure group 20 b is a lens group that extracts light guided by the light guide plate 20. That is, the light diffusion structure group 20b converts the optical path of the light guided inside the light guide plate 20 and extracts it to the emission surface 20d side. The light diffusion structure group 20b is formed so that the light emitted from the emission surface 20d of the light guide plate 20 is uniform. The light diffusion structures constituting the light diffusion structure group 20b are arranged at the same interval. The interval between the light diffusing structures is larger than the interval P between the curved surface structures 20a, and is specifically 2.0 mm.

  In the present embodiment, the optical path conversion unit is the light diffusion structure group 20b, but is not limited to this configuration, as long as it converts the optical path of the light guided inside the light guide plate 20. Good. For example, the optical path conversion unit may change the light reflection angle by forming a microlens on the lower surface 20 c of the light guided inside the light guide plate 20. Further, the shape of the scatterer is not limited to a point shape, and may be formed from a linear white pattern, a prism, or the like. The scatterer of the white pattern can be formed by, for example, screen printing, and the shape of the prism or the like can be formed by extrusion molding, injection molding, pressing, or the like.

  Here, reference is made to the light diffusion structure in the present embodiment. Here, the light diffusing structure is formed by printing with a light-diffusing diffusing resin contained in ink on the light guide plate. In the light diffusing structure shown in this embodiment, screen printing is performed. To form a light guide plate. By forming by screen printing, a uniform pattern can be easily printed on the light guide plate. In this embodiment, the diameter of a single light diffusing structure is controlled in the range of about 0.2 to 1.5 mm, and the interval is set to 2 mm.

  FIG. 4 shows a diffusion image of a diffusing material (scatterer), the left side is a schematic diagram showing scattering characteristics on the xz plane, and the right side is a schematic diagram showing scattering characteristics on the yz plane. .

  Since the light diffusion structure 20b1 as the optical path changing unit contains a scatterer, the optical path is changed by scattering reflection and transmission. Therefore, as shown in FIG. 4, the light whose path has been changed by the light diffusing structure 20b1 is changed in the path of light by irregular reflection of the light beam by the diffusing material. The probability of being scattered increases.

  FIG. 9 shows an optical path diagram of the light scattered by the light diffusion structure without breaking the total reflection condition in the longitudinal direction. The light scattered by the light diffusing structure group 20b is scattered and reflected at a wide angle by the scatterers contained in the light diffusing structure. The scattered and reflected light rays are directed to the curved surface structure portion 20a. However, in the curved surface structure portion 20a, the light rays having a shallow angle are close to perpendicular to the tangent to the curved surface structure body. Since the probability of returning to the scattered position is increased, the light confinement effect is high.

  FIG. 5 is a graph showing the relationship between the presence or absence of the curved structure 20a in the light guide plate 20 and the illuminance distribution on the exit surface. 5A shows a two-dimensional illuminance distribution on the exit surface 20d (XY plane) when the light guide plate 20 has the curved structure 20a, and FIG. FIG. 5C shows a two-dimensional illuminance distribution on the exit surface 20d (XY plane) in the absence of the body 20a, and FIG. 5C shows the center of the light guide plate with respect to the configurations of FIGS. 5A and 5B. The illumination distribution of the Y direction in a part is shown. 5A to 5C, the LEDs L3 and LEDR3 in FIGS. 1A and 1B are selectively lit.

  As shown in FIGS. 5A and 5C, when the curved surface structure 20a is formed on the exit surface 20d of the light guide plate 20, the light emitted from the LEDs L3 and LEDR3 is caused by the effect of the curved surface structure 20a. It can be seen that the light guide plate 20 is guided without spreading in the short direction (Y direction). And the light which has guided the inside of the light-guide plate 20 is taken out to the output surface 20d side by the light-diffusion structure group 20b. That is, light is emitted from a specific irradiation region (region corresponding to LEDL3 and LEDR3) on the emission surface 20d of the light guide plate 20 by selectively lighting the LEDs L3 and LEDR3.

  On the other hand, as shown in FIGS. 5B and 5C, when the curved surface structure 20a is not formed on the light exit surface 20d of the light guide plate 20, the light emitted from the LEDs L3 and LEDR3 is transmitted in the short direction (Y It can be seen that light is emitted from the entire emission surface 20 d of the light guide plate 20. That is, even if the LEDs L3 and LEDR3 are selectively turned on, light is not emitted from a specific region of the emission surface 20d.

  As described above, according to the light source module of the present embodiment, by selecting the LED to be lit among the LEDs L1 to L5 and the LEDs R1 to R5, accuracy can be obtained from the region corresponding to the selected LED on the exit surface 20d of the light guide plate 20. Light can be emitted (extracted) well. That is, by selecting the LED to be lit, the light irradiation area on the light exit surface 20d of the light guide plate 20 can be controlled.

  By the way, the liquid crystal display device 1 has a problem of blurring of moving images as compared with a CRT (Cathode-Ray Tube) display device. That is, in the CRT display device, since there is a non-light emission period in which this pixel does not emit light between the light emission period of the pixel in a certain frame and the light emission period of this pixel in the next frame, there is little afterimage feeling. On the other hand, since the display method of the liquid crystal display device 1 is a “hold type” that does not have such a non-light emitting period, an afterimage feeling is generated, and this afterimage feeling is recognized by the user as blurring of a moving image.

  Therefore, in the backlight type liquid crystal display device 1, the light source module 10 that is a backlight is divided and sequentially turned off in synchronization with the timing of applying the video signal to the liquid crystal panel 3. Backlight blinking, which is a technique for inserting a black display between them, has been proposed. Thereby, pseudo-impulse type display can be realized, the afterimage feeling can be suppressed, and the power consumption can be reduced.

  The backlight blinking will be described with reference to FIG. In the liquid crystal display device 1 including the light source module 10, the LED is selectively turned on for a predetermined time by the light source control unit so that an area corresponding to the video signal is illuminated in synchronization with vertical scanning within one frame of the video signal. Can be lit. Therefore, only a specific portion of the light guide plate 20 can be appropriately blinked to improve moving image characteristics.

  Specifically, as shown in FIG. 8, when the screen is divided into five frames 22a, 22b, 22c, 22d, and 22e, the LEDs 12 that are arranged at both longitudinal ends corresponding to each frame are also L1-L5, R1- For example, when the frame 22c is selectively turned on as shown in FIG. 8, the LEDs L3 and LEDR3 are turned on through the light source controller 23. Thereby, in the liquid crystal display device 1, the moving image characteristics can be improved by selectively lighting each frame in synchronization with the vertical scanning within one frame of the video signal.

  Next, the effect of the semi-cylindrical shape in the curved structure 20a will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing a short direction path of light guided inside the light guide plate. FIG. 6A shows a ratio H / P between the height H and the spacing P on the exit surface of the light guide plate 20. FIG. 6B shows a case where a curved surface structure 20a having a value of 0.4 is formed (Example), and FIG. 6B shows a case where a prism with an apex angle of 90 ° is formed on the exit surface of the light guide plate 20 (Conventional Example 1). 6 (c) shows a case where a prism with an apex angle of 5 ° is formed on the exit surface of the light guide plate 20 (conventional example 2), and FIG. 6 (d) shows the concave portion of FIG. 7 (a). It has a shape.

  In order to efficiently emit light guided through the light guide plate at various angles on the exit surface, it is important whether or not the light is totally reflected on the exit surface. In the light guide plate, the more light is totally reflected with respect to the light incident on the exit surface, the lower the light output efficiency from the exit surface. On the other hand, if the amount of light totally reflected with respect to the light incident on the emission surface is small, the light emission efficiency from the emission surface increases. That is, in order to efficiently emit the light inside the light guide plate on the exit surface, it is important to break the conditions for total reflection with respect to light incident on the exit surface at various angles. Originally, it is necessary to consider the two-component total reflection condition in the X direction (longitudinal direction) and the Y direction (short direction) for the light in the light guide plate, but in FIGS. Considering only the Y direction component, the X direction component is an angle at which the total reflection condition is broken.

  Since the surface shape of the curved structure 20a in FIG. 6A continuously changes (relative to the short direction), it effectively acts to extract light incident on the exit surface at various angles. Yes. Therefore, as shown in FIG. 5A, the light is efficiently extracted for various incident angles from the vertical light A rising perpendicular to the short direction to the light C guided at a shallow angle. The light can be emitted from the emission surface. In addition, the light C guided at a shallow angle is likely to be totally reflected when it is incident on a surface near horizontal (it is difficult to break the total reflection condition). However, in the shape of the curved surface structure 20a in FIG. 6A, a surface that is nearly horizontal is formed in the upper part of the semi-cylinder, and is located in a portion where the light C is not easily irradiated. Therefore, the light C guided at a shallow angle is irradiated onto a surface inclined with respect to the short-side direction, so that the total reflection condition is easily broken.

  On the other hand, when a prism having an apex angle of 90 ° is formed on the exit surface of the light guide plate 20, the vertical light A becomes return light without breaking the total reflection condition as shown in FIG. 6B. Further, the light C guided at a shallow angle is once emitted from the emission surface because the total reflection condition is broken. However, it enters the adjacent prism again and returns to the light guide plate. Further, when a prism having an apex angle of 5 ° is formed on the exit surface of the light guide plate 20, as shown in FIG. 6C, all of the light A in the vertical direction and the light C guided at a shallow angle are all. The reflection condition is broken and the light is emitted from the emission surface. However, the probability that these lights will re-enter the adjacent prism increases. Therefore, when a prism is formed on the exit surface of the light guide plate 20 as shown in FIGS. 5B and 5C, light is confined in the light guide plate, so that the efficiency of emitting light from the light guide plate is reduced. .

  Moreover, in the light source module 10 of this Embodiment, the micro lens group 20a as an optical path conversion part converts the optical path of the light guide | induced inside the light-guide plate 20, and takes out to the output surface 20d side. Since the microlens group 20a efficiently induces the light A in the vertical direction shown in FIG. 6A, the effect of the curved structure 20a is further improved. On the other hand, when a prism is formed on the exit surface of the light guide plate 20 as shown in FIGS. 6B and 6C, the reverse effect is obtained, and light cannot be efficiently emitted from the light guide plate. In FIG. 6 (d), all vertical light does not become return light due to total reflection, and can be emitted more efficiently than the prism structures of FIGS. 6 (b) and 6 (c).

  Further, when the thickness of the light guide plate is the same, the shape of the curved structure in FIG. 6A is easier to ensure the cross-sectional area than the prism shape. Therefore, in the configuration in which the curved structure 20a is formed on the exit surface of the light guide plate 20, the light coupling efficiency at the light incident surface from the LED is high, and light leakage hardly occurs.

  Moreover, when the light source module 10 of this Embodiment is used as planar illumination, such as a backlight, it is common that various optical sheets are arrange | positioned just above the light-guide plate 20. FIG. Therefore, if the exit surface of the light guide plate 20 has a sharp shape like a prism, the optical sheet may be damaged by rubbing or the like. On the other hand, when the curved structure 20a is formed on the exit surface of the light guide plate 20, there is no possibility that the optical sheet is damaged by rubbing or the like.

  Next, the shape of the curved structure 20a will be described in more detail. So far, the case where the shape of the curved structure 20a is a convex cylinder shape has been described. However, the shape of the curved structure 20a only needs to include a circular arc in a cross-sectional shape perpendicular to the longitudinal direction (X direction). A part of the shape may be a straight line. Such a shape can be formed by pressing the light guide plate 20.

  Next, the relationship between the height H of the curved structure 20a and the optical coupling efficiency at the light incident surface of the light guide plate 20 will be described. FIG. 7 is a side view showing a side shape of the light guide plate 20 in the X direction. FIG. 7A shows a case where the height H of the curved structure 20a is small, and FIG. 7B shows a curved structure. The case where the height H of the body 20a is large is shown. 7A and 7B, the interval P between the curved surface structures 20a and the thickness T of the light guide plate 20 are the same.

  In the present embodiment, light from the LED is incident on the side surface of the light guide plate 20 in the longitudinal direction. As shown in FIG. 7B, when the height H of the curved structure 20a is large in the light incident surface shape (side surface shape in the X direction of the light guide plate 20), the incident area becomes small, so that the gap (FIG. In FIG. 7B, light leaks from the shaded area, and the optical coupling efficiency is lowered. On the other hand, as shown in FIG. 7A, when the height H of the curved structure 20a is small in the light incident surface shape (side surface shape in the X direction of the light guide plate 20), the incident area becomes large and the gap Light leakage can be reduced, and the optical coupling efficiency can be improved.

  Therefore, the optical coupling efficiency and light leakage at the light incident surface decrease as the height H of the curved structure 20a increases. Approximately, when the height H of the curved structure 20a is doubled, the amount of light leakage is doubled and the loss of optical coupling efficiency is also doubled.

  Considering the optical coupling efficiency and light leakage at the light incident surface, the height H of the curved structure 20 a is preferably 5% or less of the thickness T of the light guide plate 20. As specific dimensions, for example, the thickness T of the light guide plate 20 is 4.2 mm, and the height H of the surface structure 20a is 0.16 mm. However, the confinement effect of confining light in the light guide plate 20 is reduced when the interval P is made constant and the height H is reduced in the curved structure 20a.

  Further, by reducing the interval P without changing the shape of the curved structure, it is possible to secure the cross-sectional area of the light guide plate while maintaining the straight light traveling property. For example, as a configuration A, a cross-section having a shape with a spacing P = 0.4 mm, a height H = 0.16 mm, and a thickness T = 4.2 mm, as a configuration B, a spacing P = 0.2 mm and a height H = 0. By halving the semi-cylindrical shape with a thickness of 08 mm and a thickness of T = 4.2 mm, the amount of light leakage is reduced by half with respect to the configuration A without any change in light straightness, and the optical coupling loss. Can also be halved. Further, by making the pitch P fine, there is also an effect of making it difficult to visually recognize the curved surface structure extending in the longitudinal direction.

  FIG. 7C shows the case where the height H of the curved structure 20a having the configuration A is small as shown in FIG. 7A and the height of the curved structure 20a having the configuration B as shown in FIG. 7B. The illuminance distribution in the Y direction at the center of the light guide plate when the height H is small is shown. As shown in FIG. 7C, it can be seen that there is no change in the light straightness between the shape of the configuration A and the shape of the configuration B. Therefore, by reducing the interval P with respect to the configuration A to the configuration B, it is possible to halve the amount of light leakage and halve the optical coupling loss. Further, by making the interval P fine, there is also an effect of making it difficult to visually recognize the curved surface structure extending in the longitudinal direction.

  In the above description, the configuration including one light guide plate 20 has been described. However, the light source module 10 of the present embodiment is not limited to this configuration.

  In order to perform the backlight blinking shown in FIG. 11, the light guide plate 20 is divided into a plurality of light guides 21 as shown in FIG. 10, and these light guides 21 are arranged in the longitudinal direction. Alternatively, a configuration in which the gaps 22 are provided in parallel may be employed. In this case, the LED 12 allows light to enter from one end face 21 a in the longitudinal direction of each light guide 21. In addition, it is not necessarily limited to one end surface 21a, but may be incident from the other end surface in the longitudinal direction, and light may be incident from both one end surface 21a and the other end surface. That is, in the present invention, it is sufficient that light is incident from at least one end face 21a.

  Although not shown, a light source control unit that selectively turns on the LEDs 102 as a plurality of light sources is provided for performing backlight blinking. Therefore, as shown in FIG. 11, only the LED 102a can be turned on locally according to a predetermined timing.

  When the present invention is applied to a liquid crystal display device as an electronic device, for example, the light source control unit is synchronized with vertical scanning within one frame in the video signal because the present invention is highly effective in suppressing the light guide plate from spreading in the short direction. Thus, when the light source is selectively turned on for a certain period of time so that the area corresponding to the video signal is illuminated, only a specific part of the light guide plate can be appropriately blinked to improve moving image characteristics.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention relates to a light source module including a side edge (also referred to as sidelight) type light guide plate that emits light from a light source in a planar shape by a light guide plate, and an electronic device including the same, for example, a backlight. It can be applied to electronic devices such as light source modules and liquid crystal display devices.

1 Liquid crystal display device (electronic equipment)
10 Light source module 12 LED (light source)
20 Light guide plate 20a Curved surface structure portion 20b Light diffusion structure group 20c Lower surface 20d Output surface 21a End surfaces 22a to 22e Scan frame 23 Light source control unit

  The present invention relates to a light source module and an electronic apparatus including the same, and more specifically, for example, in a liquid crystal display device, a side edge that emits light from a light source in a planar shape by a light guide plate in order to reduce the thickness. The present invention relates to a light source module used for a backlight including a type light guide plate (also referred to as a side light), and an electronic apparatus including the light source module.

  In recent years, in order to reduce the thickness of a liquid crystal display device, a backlight including a side edge type light guide plate that emits light from a light source in a planar shape by the light guide plate is frequently used.

As such a side edge type light guide plate, for example, there is a planar illumination device disclosed in Patent Document 1. FIG. 11 is a diagram showing the planar illumination device of Patent Document 1. As shown in FIG. As shown in FIG. 11 , in the planar illumination device 100 of Patent Document 1, a prismatic structure is formed on the main surface of the light guide plate 101. A plurality of LED light sources 102 are provided in the vicinity of the end surface 111 orthogonal to the main surface. Here, when only one light source 102 a of the plurality of LED light sources 102 is turned on by the selective lighting means, the light incident from the end surface 111 of the light guide plate 101 is a prism-like structure provided on the main surface of the light guide plate 101. by the action of the body, with little spread in the vertical direction in FIG. 11, and propagates in the left direction in FIG. 11, strip-like illumination area 103 is formed.

  In the cross section of the light guide plate 101, light incident on one surface of the prism surface at an angle θ with the flat surface is totally reflected and incident on the opposing prism surface and totally reflected. And it injects into a flat surface with cross-sectional angle (phi). At this time, φ = θ. In the planar illumination device of Patent Document 1, in order to obtain planar illumination, a dot-like white reflecting surface or the like is formed on a flat surface and illuminated uniformly.

  Further, for example, Patent Document 2 discloses a configuration in which a V-groove is formed on the surface opposite to the exit surface of the light guide plate.

JP 2009-283383 A (released on December 3, 2009) JP 2009-31445 A (published February 12, 2009)

  However, the planar illumination device of Patent Document 1 has the following problems.

  That is, the prismatic structure 110 in the planar illumination device of Patent Document 1 has an extremely high confinement effect for confining light in the light guide plate for light having an angle θ of a specific angle. However, the confinement effect is not exerted on the light C incident at a shallow angle (the angle θ with the flat surface is small). The light C incident at a shallow angle has a large spread in the straight direction (longitudinal direction of the light guide plate) and the vertical direction (short direction of the light guide plate). For this reason, the component which reflects light C in the direction right under the prism surface which remove | deviated from the illumination area | region 103 increases. Then, the component reflected in the direction directly below the prism surface is scattered on the flat surface and emitted from the prismatic structure 110. As a result, the light C incident at a shallow angle (the angle θ with the flat surface is small) may be emitted from a position shifted from the illumination region 103.

  As described above, in the light guide plate having the conventional configuration, light incident at a shallow angle is emitted from an area outside the irradiation area 103 where light should be emitted. As a result, there is a problem that the illumination area 103 extends in a direction (short direction) perpendicular to the straight light traveling direction (longitudinal direction).

  The present invention has been made in view of the above-described conventional problems, and an object thereof is a light source module capable of suppressing the spread of light in a direction (longitudinal direction) perpendicular to a straight traveling direction (longitudinal direction). And providing an electronic apparatus including the same.

  In order to solve the above-described problems, the light source module of the present invention includes a light guide plate, a plurality of light sources that allow light to enter from at least one end face in the longitudinal direction of the light guide plate, and a light emission surface of the light guide plate. A light source module including a plurality of light path conversion units having light diffusibility for extracting light guided inside the light guide plate on a surface opposite to the light guide plate, the light emission surface of the light guide plate It has a plurality of curved surface structure parts composed of curved surfaces having ridge lines in the longitudinal direction.

  According to said structure, it has multiple curved surface structure parts comprised by the curved surface which has a ridgeline in a longitudinal direction in the light emission surface in the said light-guide plate. That is, the plurality of curved surface structure portions are formed along the longitudinal direction. On the other hand, on the surface opposite to the light exit surface of the light guide plate, a plurality of light path conversion portions having light diffusibility for taking out light guided inside the light guide plate is formed. In the optical path conversion unit, it is possible to convert the angle component of the light beam guided in the light guide and to emit the light beam that breaks the total reflection condition in the longitudinal direction and the short direction from the light guide. The curved surface structure portion has a curved surface whose surface shape is continuously changed with respect to the short side direction. Therefore, light whose optical path has been converted by the optical path converter can be extracted efficiently from light with various angular components in the short direction when the total reflection condition is broken in the longitudinal direction. It is. Further, when the total reflection condition is not broken in the longitudinal direction, there is no emission from the light guide, and it is possible to suppress the spread of light in the short direction.

  In the light source module of the present invention, it is preferable that the interval between the optical path conversion portions is larger than the interval between the ridge lines.

  According to said structure, since the space | interval of the said optical path conversion part is larger than the space | interval of the said ridgeline, formation of an optical path conversion part becomes easy, and the positional accuracy of the optical path conversion part with respect to the curved surface structure is eased. effective.

  In the light source module of the present invention, it is preferable that the optical path changing portion is formed of ink containing a light diffusing member by screen printing.

  According to said structure, the directivity of the longitudinal direction component of a light ray can be eased, and the effect which suppresses the spreading of light can be improved with respect to a short direction component.

  In order to solve the above problems, an electronic apparatus according to the present invention includes the above-described light source module.

  According to said structure, the electronic device which can suppress the spreading to the perpendicular | vertical direction (longitudinal direction) of light to a perpendicular | vertical direction is realizable.

  In the present invention, the curved surface structure portion has a height H and the interval between the curved surface structures is P, and the curved surface structure is formed to satisfy a relationship of 0.2 <H / P <0.5. It is preferable.

  According to the above configuration, the curved surface structure portion has the tangent slope continuously changing. Therefore, it works effectively in terms of the effect of extracting light incident on the exit surface at various angles and the effect of suppressing the spread of light in the short direction. In addition, by setting H / P within the above range, there are effects that it is possible to improve the production efficiency during mass production of the curved surface structure and to suppress fluctuations in characteristics with respect to shape deviation.

  The light source module of the present invention preferably includes a light source control unit that selectively turns on the plurality of light sources.

  According to said structure, the light source control part which selectively lights up the said several light source is provided. Therefore, for example, when applied to a liquid crystal display device as an electronic device, the light source control unit selectively fixes the light source so that an area corresponding to the video signal is illuminated in synchronization with vertical scanning within one frame in the video signal. When the light is turned on for a long time, only a specific part of the light guide plate can be appropriately blinked to improve the moving image characteristics.

  As described above, the light source module of the present invention is characterized in that it has a plurality of curved surface structure parts constituted by curved surfaces having ridge lines in the longitudinal direction on the light emission surface of the light guide plate. Moreover, the electronic device of this invention is the structure provided with the said light source module as mentioned above.

  Therefore, it is possible to suppress the spread of light in the direction (longitudinal direction) perpendicular to the straight traveling direction (longitudinal direction) and to obtain the effect of not impairing the extraction efficiency.

The schematic structure of the light source module of this invention is shown, (a) is a top view, (b) is a side view. It is a disassembled perspective view which shows the structure of the liquid crystal display device provided with the said light source module. It is sectional drawing which shows a part of structure in a liquid crystal display device provided with the said light source module. The diffusion image of a light diffusing material (scattering body) is shown, the left side is a schematic diagram showing scattering characteristics on the xz plane, and the right side is a schematic diagram showing scattering characteristics on the yz plane. The relationship between the presence or absence of a semi-cylindrical curved surface structure on the light guide plate and the illuminance distribution on the exit surface is shown. (A) is a two-dimensional illumination on the exit surface when the light guide plate has a curved structure. (B) shows a two-dimensional illuminance distribution on the exit surface when the light guide plate has no curved structure, and (c) shows the light guide plate for the configurations of (a) and (b). It is the graph which showed the illumination intensity distribution of the Y direction in the center part. It is sectional drawing which shows the relationship between the path | route of the light which guides the inside of a light-guide plate, and the presence or absence of a curved-surface structure, (a) is a case where a curved-surface structure is formed in the output surface of a light-guide plate (Example). (B) shows a case in which a prism with an apex angle of 90 ° is formed on the exit surface of the light guide plate (conventional example 1), and (c) shows a prism with an apex angle of 5 ° on the exit surface of the light guide plate. Is shown (conventional example 2), and (d) shows a case where the shape of (a) is a concave cylinder. It is a side view which shows the side shape of the X direction in a light-guide plate, (a) shows the case where the height of a curved-surface structure is small, (b) shows the case where the height of a curved-surface structure is large. When the height H of the curved surface structure 20a as the configuration A is small as shown in FIG. 7A and when the height H of the curved structure 20a as the configuration B as shown in FIG. 7B is small. It is a figure which shows the illumination intensity distribution of the Y direction in the center part of a light-guide plate, respectively. It is a figure explaining backlight blinking. In this invention, it is a figure which shows the confinement effect of the light ray by the curved-surface structure in case the total reflection conditions are not destroyed with respect to the light guide direction. It is a top view which shows the other modification of the light-guide plate in the said light source module. It is a figure which shows the planar illuminating device of patent document 1.

  One embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is an exploded perspective view of a liquid crystal display device (electronic device) including the light source module of the present embodiment.

  For example, a liquid crystal display device 1 as an electronic apparatus including the light source module 10 according to the present embodiment includes a chassis 2, a light source module 10, a liquid crystal panel 3, and a bezel 4 in order from the bottom as shown in FIG. The light source module 10 includes a reflection sheet 11 as a reflection plate, an LED (Light Emitting Diode) 12 and a LED substrate 13 as a light source, a reflector 14, a light guide plate 20, a diffusion plate 15, and an optical sheet group 16. It is composed of The diffusion plate 15 and the optical sheet group 16 can be omitted depending on the application.

  FIG. 3 is a cross-sectional view illustrating a partial configuration of the liquid crystal display device 1 including the light source module 10. As shown in FIG. 3, the LED 12, the LED substrate 13, and the reflector 14 are provided at the end portion of the light guide plate 20, so that light from the LED 12 is incident on one end surface 21 a of the light guide plate 20 and guided. The liquid crystal panel 3 is irradiated with light from the exit surface 20 d of the light plate 20 through the diffusion plate 15 and the optical sheet group 16. Therefore, the light source module 10 of the present embodiment employs a side edge (also referred to as side light) method. The light guide plate 20 also partially emits light from surfaces other than the exit surface 20d, but the reflective sheet 11 is disposed on a surface other than the exit surface 20d of the light guide plate 20 and the surface on which the LEDs 12 are disposed. Since the light enters the light guide plate 20 again, most of the light is emitted from the emission surface 20d.

  Here, the longitudinal direction of the light guide plate 20 is the X direction, the normal direction of the light guide plate 20 is the Z direction, and the direction perpendicular to the X direction and the Z direction is the Y direction. The Y direction may be described as a short direction with respect to the longitudinal direction (X direction) of the light guide plate 20.

  FIG. 1 shows a schematic configuration of a light source module 10 according to the present embodiment, FIG. 1 (a) is a top view, and FIG. 1 (b) is a side view. As shown in FIGS. 1A and 1B, LEDs L <b> 1 to L <b> 5 and LEDs R <b> 1 to R <b> 5 are arranged as LEDs 12 that allow light to enter from both ends in the longitudinal direction of the light guide plate 20. The LEDs L1 to L5 are disposed so as to face the LEDs R1 to R5 in the longitudinal direction, respectively.

  Although not shown in FIGS. 1A and 1B, the light source module 10 includes a light source control unit that selectively lights the LEDs L1 to L5 and LEDs R1 to R5. This light source control part can also be controlled to turn on all the light sources of LEDs L1 to L5 and LEDs R1 to R5.

In addition, a curved surface structure 20 a formed of a curved surface is formed on the exit surface (upper surface) 20 d of the light guide plate 20. The curved surface structure 20 a is formed as a streak pattern along the longitudinal direction (X direction) of the light guide plate 20. In other words, the light guide plate 20 has a plurality of curved surface structure parts formed of curved surfaces having ridge lines 20e in the longitudinal direction on the light emission surface 20d. The curved structure 20a is a structure formed on the light exit surface 20d itself of the light guide plate 20 (a structure formed on the light guide plate 20 itself), and the light guide plate 20 is a member different from the light guide plate 20. A curved structure member is not provided.

  In the present embodiment, the curved surface structure 20a formed on the light guide plate 20 is formed with a height H and a distance between the curved surface structure portions P, and the curved surface structure is 0.2 <H / P <. It is formed with a structure satisfying 0.5.

  On the other hand, as shown in FIG. 1B, a light diffusing structure group 20b is formed on the lower surface 20c of the light guide plate 20 opposite to the curved structure 20a as an optical path changing unit.

  The light diffusion structure group 20 b is a lens group that extracts light guided by the light guide plate 20. That is, the light diffusion structure group 20b converts the optical path of the light guided inside the light guide plate 20 and extracts it to the emission surface 20d side. The light diffusion structure group 20b is formed so that the light emitted from the emission surface 20d of the light guide plate 20 is uniform. The light diffusion structures constituting the light diffusion structure group 20b are arranged at the same interval. The interval between the light diffusing structures is larger than the interval P between the curved surface structures 20a, and is specifically 2.0 mm.

  In the present embodiment, the optical path conversion unit is the light diffusion structure group 20b, but is not limited to this configuration, as long as it converts the optical path of the light guided inside the light guide plate 20. Good. For example, the optical path conversion unit may change the light reflection angle by forming a microlens on the lower surface 20 c of the light guided inside the light guide plate 20. Further, the shape of the scatterer is not limited to a point shape, and may be formed from a linear white pattern, a prism, or the like. The scatterer of the white pattern can be formed by, for example, screen printing, and the shape of the prism or the like can be formed by extrusion molding, injection molding, pressing, or the like.

  Here, reference is made to the light diffusion structure in the present embodiment. Here, the light diffusing structure is formed by printing with a light-diffusing diffusing resin contained in ink on the light guide plate. In the light diffusing structure shown in this embodiment, screen printing is performed. To form a light guide plate. By forming by screen printing, a uniform pattern can be easily printed on the light guide plate. In this embodiment, the diameter of a single light diffusing structure is controlled in the range of about 0.2 to 1.5 mm, and the interval is set to 2 mm.

  FIG. 4 shows a diffusion image of a diffusing material (scatterer), the left side is a schematic diagram showing scattering characteristics on the xz plane, and the right side is a schematic diagram showing scattering characteristics on the yz plane. .

  Since the light diffusion structure 20b1 as the optical path changing unit contains a scatterer, the optical path is changed by scattering reflection and transmission. Therefore, as shown in FIG. 4, the light whose path has been changed by the light diffusing structure 20b1 is changed in the path of light by irregular reflection of the light beam by the diffusing material. The probability of being scattered increases.

  FIG. 9 shows an optical path diagram of the light scattered by the light diffusion structure without breaking the total reflection condition in the longitudinal direction. The light scattered by the light diffusing structure group 20b is scattered and reflected at a wide angle by the scatterers contained in the light diffusing structure. The scattered and reflected light rays are directed to the curved surface structure portion 20a. However, in the curved surface structure portion 20a, the light rays having a shallow angle are close to perpendicular to the tangent to the curved surface structure body. Since the probability of returning to the scattered position is increased, the light confinement effect is high.

  FIG. 5 is a graph showing the relationship between the presence or absence of the curved structure 20a in the light guide plate 20 and the illuminance distribution on the exit surface. 5A shows a two-dimensional illuminance distribution on the exit surface 20d (XY plane) when the light guide plate 20 has the curved structure 20a, and FIG. FIG. 5C shows a two-dimensional illuminance distribution on the exit surface 20d (XY plane) in the absence of the body 20a, and FIG. 5C shows the center of the light guide plate with respect to the configurations of FIGS. 5A and 5B. The illumination distribution of the Y direction in a part is shown. 5A to 5C, the LEDs L3 and LEDR3 in FIGS. 1A and 1B are selectively lit.

  As shown in FIGS. 5A and 5C, when the curved surface structure 20a is formed on the exit surface 20d of the light guide plate 20, the light emitted from the LEDs L3 and LEDR3 is caused by the effect of the curved surface structure 20a. It can be seen that the light guide plate 20 is guided without spreading in the short direction (Y direction). And the light which has guided the inside of the light-guide plate 20 is taken out to the output surface 20d side by the light-diffusion structure group 20b. That is, light is emitted from a specific irradiation region (region corresponding to LEDL3 and LEDR3) on the emission surface 20d of the light guide plate 20 by selectively lighting the LEDs L3 and LEDR3.

  On the other hand, as shown in FIGS. 5B and 5C, when the curved surface structure 20a is not formed on the light exit surface 20d of the light guide plate 20, the light emitted from the LEDs L3 and LEDR3 is transmitted in the short direction (Y It can be seen that light is emitted from the entire emission surface 20 d of the light guide plate 20. That is, even if the LEDs L3 and LEDR3 are selectively turned on, light is not emitted from a specific region of the emission surface 20d.

  As described above, according to the light source module of the present embodiment, by selecting the LED to be lit among the LEDs L1 to L5 and the LEDs R1 to R5, accuracy can be obtained from the region corresponding to the selected LED on the exit surface 20d of the light guide plate 20. Light can be emitted (extracted) well. That is, by selecting the LED to be lit, the light irradiation area on the light exit surface 20d of the light guide plate 20 can be controlled.

  By the way, the liquid crystal display device 1 has a problem of blurring of moving images as compared with a CRT (Cathode-Ray Tube) display device. That is, in the CRT display device, since there is a non-light emission period in which this pixel does not emit light between the light emission period of the pixel in a certain frame and the light emission period of this pixel in the next frame, there is little afterimage feeling. On the other hand, since the display method of the liquid crystal display device 1 is a “hold type” that does not have such a non-light emitting period, an afterimage feeling is generated, and this afterimage feeling is recognized by the user as blurring of a moving image.

  Therefore, in the backlight type liquid crystal display device 1, the light source module 10 that is a backlight is divided and sequentially turned off in synchronization with the timing of applying the video signal to the liquid crystal panel 3. Backlight blinking, which is a technique for inserting a black display between them, has been proposed. Thereby, pseudo-impulse type display can be realized, the afterimage feeling can be suppressed, and the power consumption can be reduced.

  The backlight blinking will be described with reference to FIG. In the liquid crystal display device 1 including the light source module 10, the LED is selectively turned on for a predetermined time by the light source control unit so that an area corresponding to the video signal is illuminated in synchronization with vertical scanning within one frame of the video signal. Can be lit. Therefore, only a specific portion of the light guide plate 20 can be appropriately blinked to improve moving image characteristics.

  Specifically, as shown in FIG. 8, when the screen is divided into five frames 22a, 22b, 22c, 22d, and 22e, the LEDs 12 that are arranged at both longitudinal ends corresponding to each frame are also L1-L5, R1- For example, when the frame 22c is selectively turned on as shown in FIG. 8, the LEDs L3 and LEDR3 are turned on through the light source controller 23. Thereby, in the liquid crystal display device 1, the moving image characteristics can be improved by selectively lighting each frame in synchronization with the vertical scanning within one frame of the video signal.

Next, the effect of the semi-cylindrical shape in the curved structure 20a will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing a short direction path of light guided inside the light guide plate. FIG. 6A shows a ratio H / P between the height H and the spacing P on the exit surface of the light guide plate 20. FIG. 6B shows a case where a curved surface structure 20a having a value of 0.4 is formed (Example), and FIG. 6B shows a case where a prism with an apex angle of 90 ° is formed on the exit surface of the light guide plate 20 (Conventional Example 1). 6 (c) shows a case where a prism having an apex angle of 5 ° is formed on the exit surface of the light guide plate 20 (conventional example 2), and FIG. 6 (d) shows the concave portion of FIG. 6 (a). It has a shape.

  In order to efficiently emit light guided through the light guide plate at various angles on the exit surface, it is important whether or not the light is totally reflected on the exit surface. In the light guide plate, the more light is totally reflected with respect to the light incident on the exit surface, the lower the light output efficiency from the exit surface. On the other hand, if the amount of light totally reflected with respect to the light incident on the emission surface is small, the light emission efficiency from the emission surface increases. That is, in order to efficiently emit the light inside the light guide plate on the exit surface, it is important to break the conditions for total reflection with respect to light incident on the exit surface at various angles. Originally, it is necessary to consider the two-component total reflection condition in the X direction (longitudinal direction) and the Y direction (short direction) for the light in the light guide plate, but in FIGS. Considering only the Y direction component, the X direction component is an angle at which the total reflection condition is broken.

Since the surface shape of the curved structure 20a in FIG. 6A continuously changes (relative to the short direction), it effectively acts to extract light incident on the exit surface at various angles. Yes. Therefore, as shown in FIG. 6 (a), the vertical light A that rises perpendicularly to the lateral direction to the light C to the light guide at a shallow angle, effectively taking out the light for various angles of incidence The light can be emitted from the emission surface. In addition, the light C guided at a shallow angle is likely to be totally reflected when it is incident on a surface near horizontal (it is difficult to break the total reflection condition). However, in the shape of the curved surface structure 20a in FIG. 6A, a surface that is nearly horizontal is formed in the upper part of the semi-cylinder, and is located in a portion where the light C is not easily irradiated. Therefore, the light C guided at a shallow angle is irradiated onto a surface inclined with respect to the short-side direction, so that the total reflection condition is easily broken.

On the other hand, when a prism having an apex angle of 90 ° is formed on the exit surface of the light guide plate 20, the vertical light A becomes return light without breaking the total reflection condition as shown in FIG. 6B. Further, the light C guided at a shallow angle is once emitted from the emission surface because the total reflection condition is broken. However, it enters the adjacent prism again and returns to the light guide plate. Further, when a prism having an apex angle of 5 ° is formed on the exit surface of the light guide plate 20, as shown in FIG. 6C, all of the light A in the vertical direction and the light C guided at a shallow angle are all. The reflection condition is broken and the light is emitted from the emission surface. However, the probability that these lights will re-enter the adjacent prism increases. Therefore, if the prism is formed on the exit surface of the light guide plate 20 as shown in FIG. 6 (b) and (c), to confine the light in the light guide plate, the efficiency of emitting light from the light guide plate is reduced .

Further, in the light source module 10 of the present embodiment, the curved surface structure ( microlens group ) 20a as the optical path conversion unit converts the optical path of the light guided inside the light guide plate 20, and the emission surface 20d. Take out to the side. Since the curved structure group 20a efficiently induces the light A in the vertical direction shown in FIG. 6A, the effect of the curved structure 20a is further improved. On the other hand, when a prism is formed on the exit surface of the light guide plate 20 as shown in FIGS. 6B and 6C, the reverse effect is obtained, and light cannot be efficiently emitted from the light guide plate. In FIG. 6 (d), all vertical light does not become return light due to total reflection, and can be emitted more efficiently than the prism structures of FIGS. 6 (b) and 6 (c).

  Further, when the thickness of the light guide plate is the same, the shape of the curved structure in FIG. 6A is easier to ensure the cross-sectional area than the prism shape. Therefore, in the configuration in which the curved structure 20a is formed on the exit surface of the light guide plate 20, the light coupling efficiency at the light incident surface from the LED is high, and light leakage hardly occurs.

  Moreover, when the light source module 10 of this Embodiment is used as planar illumination, such as a backlight, it is common that various optical sheets are arrange | positioned just above the light-guide plate 20. FIG. Therefore, if the exit surface of the light guide plate 20 has a sharp shape like a prism, the optical sheet may be damaged by rubbing or the like. On the other hand, when the curved structure 20a is formed on the exit surface of the light guide plate 20, there is no possibility that the optical sheet is damaged by rubbing or the like.

  Next, the shape of the curved structure 20a will be described in more detail. So far, the case where the shape of the curved structure 20a is a convex cylinder shape has been described. However, the shape of the curved structure 20a only needs to include a circular arc in a cross-sectional shape perpendicular to the longitudinal direction (X direction). A part of the shape may be a straight line. Such a shape can be formed by pressing the light guide plate 20.

  Next, the relationship between the height H of the curved structure 20a and the optical coupling efficiency at the light incident surface of the light guide plate 20 will be described. FIG. 7 is a side view showing a side shape of the light guide plate 20 in the X direction. FIG. 7A shows a case where the height H of the curved structure 20a is small, and FIG. 7B shows a curved structure. The case where the height H of the body 20a is large is shown. 7A and 7B, the interval P between the curved surface structures 20a and the thickness T of the light guide plate 20 are the same.

  In the present embodiment, light from the LED is incident on the side surface of the light guide plate 20 in the longitudinal direction. As shown in FIG. 7B, when the height H of the curved structure 20a is large in the light incident surface shape (side surface shape in the X direction of the light guide plate 20), the incident area becomes small, so that the gap (FIG. In FIG. 7B, light leaks from the shaded area, and the optical coupling efficiency is lowered. On the other hand, as shown in FIG. 7A, when the height H of the curved structure 20a is small in the light incident surface shape (side surface shape in the X direction of the light guide plate 20), the incident area becomes large and the gap Light leakage can be reduced, and the optical coupling efficiency can be improved.

  Therefore, the optical coupling efficiency and light leakage at the light incident surface decrease as the height H of the curved structure 20a increases. Approximately, when the height H of the curved structure 20a is doubled, the amount of light leakage is doubled and the loss of optical coupling efficiency is also doubled.

  Considering the optical coupling efficiency and light leakage at the light incident surface, the height H of the curved structure 20 a is preferably 5% or less of the thickness T of the light guide plate 20. As specific dimensions, for example, the thickness T of the light guide plate 20 is 4.2 mm, and the height H of the surface structure 20a is 0.16 mm. However, the confinement effect of confining light in the light guide plate 20 is reduced when the interval P is made constant and the height H is reduced in the curved structure 20a.

  Further, by reducing the interval P without changing the shape of the curved structure, it is possible to secure the cross-sectional area of the light guide plate while maintaining the straight light traveling property. For example, as a configuration A, a cross-section having a shape with a spacing P = 0.4 mm, a height H = 0.16 mm, and a thickness T = 4.2 mm, as a configuration B, a spacing P = 0.2 mm and a height H = 0. By halving the semi-cylindrical shape with a thickness of 08 mm and a thickness of T = 4.2 mm, the amount of light leakage is reduced by half with respect to the configuration A without any change in light straightness, and the optical coupling loss. Can also be halved. Further, by making the pitch P fine, there is also an effect of making it difficult to visually recognize the curved surface structure extending in the longitudinal direction.

  FIG. 7C shows the case where the height H of the curved structure 20a having the configuration A is small as shown in FIG. 7A and the height of the curved structure 20a having the configuration B as shown in FIG. 7B. The illuminance distribution in the Y direction at the center of the light guide plate when the height H is small is shown. As shown in FIG. 7C, it can be seen that there is no change in the light straightness between the shape of the configuration A and the shape of the configuration B. Therefore, by reducing the interval P with respect to the configuration A to the configuration B, it is possible to halve the amount of light leakage and halve the optical coupling loss. Further, by making the interval P fine, there is also an effect of making it difficult to visually recognize the curved surface structure extending in the longitudinal direction.

  In the above description, the configuration including one light guide plate 20 has been described. However, the light source module 10 of the present embodiment is not limited to this configuration.

  In order to perform the backlight blinking shown in FIG. 11, the light guide plate 20 is divided into a plurality of light guides 21 as shown in FIG. 10, and these light guides 21 are arranged in the longitudinal direction. Alternatively, a configuration in which the gaps 22 are provided in parallel may be employed. In this case, the LED 12 allows light to enter from one end face 21 a in the longitudinal direction of each light guide 21. In addition, it is not necessarily limited to one end surface 21a, but may be incident from the other end surface in the longitudinal direction, and light may be incident from both one end surface 21a and the other end surface. That is, in the present invention, it is sufficient that light is incident from at least one end face 21a.

As shown in FIG. 8, the liquid crystal display device 1 of the present embodiment includes a light source control unit that selectively turns on the LEDs LEDL1 to L5 and LEDs R1 to R5 that are a plurality of light sources in order to perform backlight blinking. ing. Therefore, as shown in FIG. 8 , only the LEDs L3 and LEDR3 can be turned on locally according to a predetermined timing.

  When the present invention is applied to a liquid crystal display device as an electronic device, for example, the light source control unit is synchronized with vertical scanning within one frame in the video signal because the present invention is highly effective in suppressing the light guide plate from spreading in the short direction. Thus, when the light source is selectively turned on for a certain period of time so that the area corresponding to the video signal is illuminated, only a specific part of the light guide plate can be appropriately blinked to improve moving image characteristics.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention relates to a light source module including a side edge (also referred to as sidelight) type light guide plate that emits light from a light source in a planar shape by a light guide plate, and an electronic device including the same, for example, a backlight. It can be applied to electronic devices such as light source modules and liquid crystal display devices.

1 Liquid crystal display device (electronic equipment)
10 Light source module 12 LED (light source)
20 Light guide plate 20a Curved surface structure portion 20b Light diffusion structure group 20c Lower surface 20d Output surface 21a End surfaces 22a to 22e Scan frame 23 Light source control unit

Claims (6)

A light guide plate;
A plurality of light sources that respectively enter light from at least one end face in the longitudinal direction of the light guide plate;
A light source module comprising a light path conversion unit having a plurality of light diffusion structures for extracting light guided inside the light guide plate on a surface opposite to the light exit surface of the light guide plate,
A light source module, comprising: a plurality of curved surface structure parts each having a curved surface having a ridge line in a longitudinal direction on a light emission surface of the light guide plate.   The light source module according to claim 1, wherein an interval between the optical path conversion units is larger than an interval between the ridge lines.   The curved surface structure is formed so as to satisfy a relationship of 0.2 <H / P <0.5, where the height of the curved surface structure is H and the interval between the curved surface structures is P. The light source module according to 2.   The light source module according to claim 1, further comprising a light source control unit that locally lights the plurality of light sources.   The light source module according to any one of claims 1 to 4, wherein the optical path conversion unit has a light diffusing structure by screen printing.   An electronic apparatus comprising the light source module according to claim 1.