JP2007122971A - Surface light source device and image display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device and an image display device capable of clarifying a boundary between a region irradiated with light and a region other than that in a light emitting surface when part of a plurality of light sources is turned on. provide.
[Solution]
The surface light source device emits a plurality of light sources 31, 32, a light source control unit that controls turning on and off of each of the light sources 31, 32, and light emitted from the plurality of light sources 31, 32 as planar light. A light guide plate 7 having a light emitting surface. The light guide plate 7 is divided into a plurality of regions 71 and 72 corresponding to the irradiation regions of the plurality of light sources 31 and 32, and the plurality of regions 71 and 72. At least a part of the boundary surface is provided with a light shielding surface or a reflection surface, and at least one light source is arranged corresponding to each of the plurality of regions.
[Selection] Figure 1

Description

    The present invention relates to a surface light source device having a light guide plate that emits light from a light source as planar light, and an image display device having the surface light source device.

  A general liquid crystal display device includes a liquid crystal panel and a backlight unit. That is, the liquid crystal display device is configured to display an image by transmitting light generated by the backlight unit to the liquid crystal panel and modulating the amount of the light. For example, a light emitting diode or a cold cathode tube is used as a light source of the backlight unit. The power consumed by the backlight unit having such a light source accounts for a large proportion of the power consumed by the entire liquid crystal display device. Therefore, a method for reducing the power consumed by the backlight unit in a liquid crystal display device has been proposed (for example, see Patent Document 1).

The liquid crystal display device described in Patent Document 1 includes a plurality of light emitting diodes as light sources. In the power saving mode, some of the plurality of light emitting diodes are turned on and others are turned off. Thereby, a part of the entire display area is irradiated with light to become a lighting area. By making a part of the display area a lighting area, the power consumption of the backlight is reduced. As described above, other methods for realizing the power saving mode by controlling the light source in the backlight unit have been proposed (see, for example, Patent Documents 2 and 3).
Japanese Patent Laid-Open No. 2001-21863 JP 2002-6316 A JP 2000-275605 A

  However, when a part of the light sources is turned on as in the liquid crystal display device in Patent Document 1, there is a problem that the boundary between the lighting region and the non-lighting region is blurred in the entire display region. That is, there is a problem that light leaks to the non-lighting area, and the lighting area is blurred on the display and appears uneven.

  Therefore, the present invention provides a surface light source device and an image that can clarify the boundary between a region irradiated with light and other regions on the light emitting surface when some of the plurality of light sources are turned on. An object is to provide a display device.

  A surface light source device according to the present invention includes a plurality of light sources, a light source control unit that controls turning on and off of each of the plurality of light sources, and a light emitting surface that emits light emitted from the plurality of light sources as planar light. The light guide plate is divided into a plurality of regions, and a light shielding surface or a reflective surface is provided on at least a part of a boundary surface of the plurality of regions, each of the plurality of regions. And at least one of the light sources is arranged correspondingly.

  An image display device according to the present invention includes an image display unit, a plurality of light sources, a light source control unit that controls turning on and off of each of the plurality of light sources, and light emitted from the plurality of light sources as planar light. A light guide plate having a light emitting surface for irradiating the image display unit, the light guide plate is divided into a plurality of regions, and at least a part of a boundary surface of the plurality of regions has a light shielding surface or a reflective surface. And at least one of the light sources is arranged corresponding to each of the plurality of regions.

  According to the present invention, when a part of a plurality of light sources is turned on, a surface light source device and an image that can clarify the boundary between a region irradiated with light and other regions on the light emitting surface. A display device can be provided.

  A surface light source device according to the present invention includes a plurality of light sources, a light source control unit that controls turning on and off of each of the plurality of light sources, and a light emitting surface that emits light emitted from the plurality of light sources as planar light. The light guide plate is divided into a plurality of regions, and a light shielding surface or a reflective surface is provided on at least a part of a boundary surface of the plurality of regions, each of the plurality of regions. And at least one of the light sources is arranged correspondingly.

  The light guide plate is divided into a plurality of regions corresponding to the irradiation regions of the plurality of light sources, and at least a part of a boundary surface of the plurality of regions is provided with a light shielding surface or a reflection surface. Therefore, in each of the divided areas, the light emitted from the corresponding light source to the area is less likely to leak to other areas. That is, in the light guide plate, light that enters one of the divided areas is less likely to go to another area. Therefore, for example, when the light source controller turns on some of the plurality of light sources, the boundary between the light emitting area and the non-light emitting area can be clarified on the light emitting surface of the light guide plate. .

  The surface light source device has a structure in which light is emitted from at least one light source to each of the plurality of regions. Therefore, the light source control unit can control which of the plurality of regions is a lighting region by controlling the turning on and off of each of the plurality of light sources.

  In the surface light source device according to the present invention, it is preferable that a slit is formed at a boundary between the plurality of regions in the light guide plate, and a light shielding unit or a reflection unit is provided in the slit.

  Light irradiated to one of the plurality of regions is prevented from leaking to the adjacent region by a light shielding unit or a reflecting unit provided in a slit formed at the boundary with the adjacent region. For this reason, the light guide plate has a configuration in which light does not easily enter and exit between the divided regions.

  In the surface light source device according to the present invention, the plurality of light sources are arranged in a recess provided in at least one surface of the light guide plate in each of the plurality of regions, and the light guide plate is arranged in the recess. It is preferable to provide a light shielding means for preventing light from leaking to the outside of the light guide plate or a reflection means for reflecting light from the light source arranged in the recess to the inside of the light guide plate.

  Thereby, the light guide plate is configured such that light does not enter and exit between the divided regions. Moreover, since the light from the light source is prevented from leaking out of the light guide plate, the light from the light source is efficiently applied to the liquid crystal panel.

  An image display device according to the present invention includes an image display unit, a plurality of light sources, a light source control unit that controls turning on and off of each of the plurality of light sources, and light emitted from the plurality of light sources as planar light. A light guide plate having a light emitting surface for irradiating the image display unit, the light guide plate is divided into a plurality of regions, and at least a part of a boundary surface of the plurality of regions has a light shielding surface or a reflective surface. And at least one of the light sources is arranged corresponding to each of the plurality of regions.

  An example of an embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1)
FIG. 1A is a perspective view showing a schematic structure of the liquid crystal display device according to the present embodiment. FIG. 1B is a side view of the liquid crystal display device shown in FIG. As shown in FIGS. 1A and 1B, the liquid crystal display device 20 includes a liquid crystal panel 6, a backlight 4 that irradiates the liquid crystal panel 6 with planar light, and a substrate 8.

  The backlight 4 includes light sources 31 and 32, a light guide plate 7, and a light source control unit (not shown). The light sources 31 and 32 irradiate the light guide plate 7 with light. In the present embodiment, a light emitting diode is used as the light sources 31 and 32. As the light sources 31 and 32, other light emitting elements such as a cold cathode tube and an EL (electroluminescence) element can be used.

The light guide plate 7 is disposed so as to irradiate the liquid crystal panel 6 with light from the light sources 31 and 32 as planar light. The light guide plate 7 includes two light guides 71 and 72. The respective light guides 71 and 72 receive the light emitted from the light sources 31 and 32 by the light receiving surfaces 71b ₁ and 72b ₁ and irradiate the liquid crystal panel 6 as planar light from the light emitting surfaces 71a and 72a. To do. Here, in each light guide 71 and 72, the surface on the liquid crystal panel 6 side is set as the light emitting surfaces 71a and 72a, and the surface opposite to the liquid crystal panel 6 is set as the bottom surfaces 71c and 72c. Hereinafter, of the side surfaces of the light guides 71 and 72, the surfaces that receive the light from the light sources 31 and 32 are the light receiving surfaces 71b ₁ and 72b ₁ , and the surfaces that face the light receiving surfaces 71b ₁ and 72b ₁ are the side surfaces 71b ₂ and 72b. ₂ is called.

  The liquid crystal panel 6 includes, for example, an active matrix substrate, a counter substrate, and a liquid crystal layer provided between these substrates. Although not shown, the liquid crystal display device 20 includes a drive circuit (not shown) that inputs an image signal and outputs a drive signal to the liquid crystal panel 6. The liquid crystal panel 6 is driven by the drive circuit.

  In this embodiment, the two light sources 31 and 32 are arrange | positioned corresponding to the two light guides 71 and 72, respectively. FIG. 2 is a diagram schematically showing a structure when the backlight 4 is viewed from the light emitting surfaces 71a and 72a. The light emitted from the light source 31 enters the light guide 71 and is emitted as planar light from the light emitting surface 71a of the light guide 71. The light emitted from the light source 32 enters the light guide 72 and guides the light. The light is emitted from the light emitting surface 72a of the body 72 as planar light. That is, the light guide plate 7 has light emitting surfaces 71a and 72a divided into two.

  Next, the light guide plate 7 will be described in detail. FIG. 3A is a diagram showing a state where two light guides 71 and 72 constituting the backlight 4 are separated. FIG. 3B is a side view of the light guide 72 and the light source 32 shown in FIG.

The light guides 71 and 72 are plate-like bodies having a rectangular cross section. The light guides 71 and 72 include light receiving surfaces 71b ₁ and 72b ₁ that receive light from the light sources 31 and 32, and light emitting surfaces 71a and 72a that are formed perpendicular to the light receiving surfaces 71b ₁ and 72b ₁ . The light source 31 is disposed on the light receiving surface 71b ₁ of the light guide 71, and the light source 32 is disposed on the light receiving surface 72b ₂ of the light guide 72. Side 71b ₃ of the light guide 71 is mirror-finished. The side surface 71b ₃ of the light guide 71 subjected to the mirror finish and the side surface 72b _{4 of the} light guide 72 are bonded together to form the light guide plate 7. That is, the side surface 71b ₃ of the light guide 71 that has been mirror-finished serves as a boundary surface between the light guide 71 and the light guide 72.

Since the surface serving as the boundary between the light guide 71 and the light guide 72 is mirror-finished, the light that has entered the light guide 71 from the light source 31 is reflected inside the side surface 71 b ₃ of the light guide 71. Therefore, the light guide 72 does not leak. Similarly, the light that has entered the light guide 72 from the light source 32 is reflected inside the side surface 72 b ₄ of the light guide 72, and therefore does not leak into the light guide 71.

The surfaces other than the light emitting surfaces 71a and 72a and the light receiving surfaces 71b ₁ and 72b ₂ of the light guides 71 and 72, that is, the side surfaces 71b ₄ , 71b ₂ , 72b ₃ and 72b ₂ and the bottom surfaces 71c and 72c are also mirror-finished. It is preferable.

  The mirror surface treatment can be performed, for example, by directly depositing a material having a high light reflectance such as aluminum on the surface of the light guide. In addition, a film that has been mirror-finished by depositing a material such as aluminum is attached to the surface of the light guide with an adhesive, or it is pressure-bonded to the surface of the light guide through a material that is cured by heat or pressure. May be. Thus, a mirror surface can be provided in the boundary of light guides by carrying out the mirror surface process of the side surface of an adjacent light guide.

  Moreover, a mirror surface can also be provided in the boundary of light guides by inserting the film which carried out the mirror surface process between the adjacent light guides. For example, a mirror-treated film is sandwiched and fixed between two light guides to obtain a light guide plate having two regions with a mirror surface at the boundary. FIG. 4 is a diagram illustrating an example of a case where a mirror-finished film is sandwiched between two light guides.

  As shown in FIG. 4A, the two light guides 71 and 72 are fitted and fixed to the mold 14 as shown in FIG. As shown in c), the light guide plate 7 having the light emitting surfaces 71a and 72a divided into two can be formed. The inner surface of the mold 14 may be mirror-finished. However, the portion of the inner surface of the mold 14 where the light source irradiates the light guides 71 and 72 is preferably transparent so that the light from the light source reaches the light guides 71 and 72. Further, the whole including the light guides 71 and 72 and the light sources 31 and 32 may be fitted into the mold 14 and fixed.

In addition, when the light guide 71 having a mirror-treated side surface 71b ₃ as shown in FIG. 3A is bonded to another light guide 72, the light guide 71 is fitted into the mold 14 as shown in FIG. 4B. It can be fixed with.

  Although not shown in FIGS. 3 and 4, a planar shape irradiated from the light guide plate 7 by providing, for example, a prism sheet or a diffusion sheet on the light emitting surfaces 71 a and 72 a side of the light guides 71 and 72. It is preferable to guide light to the liquid crystal layer efficiently and uniformly.

  The bottom surfaces 71c and 72c of the light guides 71 and 72 shown in FIGS. 3 and 4 may be mirror-finished. For example, a prism sheet or the like is provided on the bottom surfaces 71c and 72c of the light guides 71 and 72. Thus, the light emitted from the light emitting surfaces 71a and 71b may be uniform. Further, at least part of the bottom surfaces 71c and 72c of the light guides 71 and 72 is inclined with respect to the light emitting surfaces 71a and 72a, and the light reflected by the bottom surfaces 71c and 72c is uniformly emitted from the light emitting surfaces 71a and 72a. Such a structure may be used.

  In the present embodiment, the case where the surface serving as the boundary between the light guide 71 and the light guide 72 is a mirror surface is described. However, the surface is not necessarily a mirror surface as long as it reflects light.

Moreover, although the light guides 71 and 72 shown in FIGS. 3 and 4 have a flat plate shape with a constant thickness, the shape of the light guide is not limited thereto. For example, the shape of the light guide can be a so-called wedge shape in which the thickness decreases as the distance from the light receiving surface of the light from the light source increases. Fig.5 (a) is a figure which shows the example of the backlight using a wedge-shaped light guide, FIG.5 (b) is a side view of the backlight shown to Fig.5 (a). The light guides 731 and 732 shown in FIG. 5A include light receiving surfaces 731b ₁ and 732b ₂ that receive light from the light sources 31 and 32, and light emitting surfaces 731a and 732a that are perpendicular to the light receiving surfaces 731b ₁ and 732b _2. And bottom surfaces 731c and 732c that are inclined with respect to the light emitting surfaces 731a and 732a. That is, the cross sections of the light guides 731 and 732 are wedge-shaped.

  Next, the operation of the backlight 4 will be described. FIG. 6 is a diagram illustrating an example of a mechanism for the light source control unit 5 to control the light sources 31 and 32. The light source controller 5 sends a control signal to each of the switch 91 and the switch 92, and independently controls ON / OFF. The light source 31 and the light source 32 are connected to the GND via the power supply 10, the switch 91, and the switch 92. Therefore, the light source 31 is turned on when the switch 91 is turned on, and the light source 31 is turned off when the switch 91 is turned off. Similarly, the light source 32 is turned on when 92 is ON, and the light source 32 is turned off when the switch 92 is OFF.

  For example, the light source control unit 5 turns on both the light sources 31 and 32, turns on the light source 31 and turns off the light source 32, turns off the light source 31 and turns on the light source 32, and turns off both the light sources 31 and 32. The four states can be switched. For example, the light source control unit 5 controls these four states in accordance with an externally input signal.

  The light source control unit 5 may adjust the voltage supplied from the power supply 10 to the light sources 31 and 32 by turning on the switch 91 and the switch 92 and sending a control signal to the power supply 10. Thereby, the brightness of the light sources 31 and 32 is adjusted according to the voltage level supplied to the light sources 31 and 32.

FIG. 7A is a diagram showing an example of a detailed circuit configuration of the configuration shown in FIG. With the configuration shown in FIG. 7A, a function of adjusting the voltage applied to the light sources 31 and 32 is realized. In the circuit shown in FIG. 7A, the variable resistor 21 is connected to the terminals 10a, GND, and the terminal 3a. A reference voltage V _{ref from} the power source 10 is input to the terminal 10a. The terminal 3 a is connected to the light source 31 and the light source 32. The light source controller 5 can adjust the voltage of the terminal 3 a, that is, the voltage supplied to the light source 31 and the light source 32 by controlling the resistance value of the variable resistor 21.

  FIG. 7B is a diagram showing a modification of the circuit configuration shown in FIG. In the circuit shown in FIG. 7B, resistors 22, 23, 24, 25 and a switch 51 are provided instead of the variable resistor 21. A terminal 22 a is provided between the resistors 22 and 23, a terminal 23 a is provided between the resistors 22 and 23, and a terminal 24 a is provided between the resistors 23 and 24. The switch 51 selectively switches whether the terminal 3a is connected to the terminal 22a, the terminal 23a, or the terminal 24a. Although not shown, the terminal 3a is connected to the light source 31 and the light source 32 as in FIG. The light source control unit 5 can adjust the voltage applied to the light source 31 and the light source 32 by controlling the switching of the switch 51.

  With the configuration illustrated in FIG. 7B, the light source control unit 5 can switch the voltage applied to the light source 31 and the light source 32 in a stepwise manner. On the other hand, in the configuration shown in FIG. 7A, the light source control unit 5 can continuously change the voltage applied to the light source 31 and the light source 32 in a stepless manner.

FIG. 8A is a diagram showing another example of the detailed circuit configuration of the configuration shown in FIG. The circuit shown in FIG. 8A includes a power supply 10, a switch 52, a resistor 26 (resistance value R), an operational amplifier 61, and a capacitor 62 (capacitance C). The switch 52 switches the connection destination of the terminal 52a between a terminal 10a connected to the power supply 10 that provides the reference voltage _Vref and a terminal 56 connected to GND. The terminal 52 a is connected to one terminal of the resistor 26, and the other terminal of the resistor 26 is connected to the − terminal of the operational amplifier 61. The operational amplifier 61 has a + terminal connected to GND and an output terminal connected to the terminal 3a. The capacitor 62 is connected to the negative terminal and the output terminal of the operational amplifier 61. Although not shown, the terminal 3a is connected to the light source 31 and the light source 32 as in FIG.

The switching of the switch 52 is controlled by, for example, a PWM signal (pulse width modulation signal) from the light source control unit 5. FIG. 8B is a diagram illustrating an example of time transition of voltage at the terminal 52a of the switch 52 controlled by PWM input. t _pwm represents the period of the pulse, and t _on represents the time during which the switch 52 is ON, that is, the time during which the voltage at the terminal 52a is at the reference voltage V _ref . In the circuit shown in FIG. 8A, when t _pwm << CR, the voltage V of the terminal 3a is expressed as, for example, (Equation 1) below.

(Formula 1)
V = (t _on / t _pwm ) · V _ref

That _is, the longer the length of _{t on,} the voltage V of the terminal 3a is high. The light source controller 5 can adjust the voltage V of the terminal 3a by changing the length of t _on by the PWM signal for controlling the switch 52.

FIG. 9 is a diagram showing still another example of the detailed circuit configuration of the configuration shown in FIG. The circuit shown in FIG. 9 includes a current source 57, a switch 54, a resistor 27, a capacitor 63, and a one-shot multivibrator 55. Current source 57 is supplied to the switch 54 side while maintaining a current from terminal 10a to be connected to the power supply 10 to a constant current value i _s. A resistor 27 (resistance value R _L ) and a capacitor 63 are connected in parallel between the switch 54 and GND. Further, a terminal 3a is provided on the opposite side of the switch 54 from the current source 57, and the terminal 3a is connected to the light source 31 and the light source 32 (not shown) as in FIG. 7A. That is, the switch 54 switches ON / OFF of the connection between the terminal 3a, the resistor 27, the capacitor 63, and the current source 57.

Switching of the switch 54 is controlled by a signal input from the light source control unit 5 via the one-shot multivibrator 55. The light source control section 5, for example, inputting a pulse signal of a frequency f _in the one-shot multivibrator 55. One-shot multivibrator 55, every time the light source control unit 5 pulse is input, and outputs one shot pulse of a predetermined time width t _w the switch 54. As a result, the switch 54, the pulse of a predetermined time width _{t w} of frequency _{f in} is input. Switch 54, repeated the ON / OFF at a frequency _{f in,} time that is ON at one time is a _{t w.} In this case, the voltage V output to the terminal 3a is expressed by, for example, the following (Formula 2).

(Formula 2)
_{V = f in · i s ·} t w · R L

As the frequency _{f in} is high, the voltage V becomes higher. Therefore, the light source control section 5 is capable of adjusting the voltage V of the terminal 3a by adjusting the frequency f _in of the pulse signal inputted to the switch 54.

  The example in which the light source control unit 5 adjusts the brightness of the light source 31 and the light source 32 has been described above, but the method of adjusting the brightness of the light source 31 and the light source 32 is not limited to the above example. For example, the brightness of the light source 31 and the light source 32 can be adjusted by a resistor DA converter other than the above example. Further, the light source control unit 5 can independently perform an operation for adjusting the brightness of the light source 31 and the light source 32 and an operation for controlling turning on and off of the light source 31 and the light source 32.

  The light source control unit 5 controls the turning on and off of the light source 31 and the light source 32, so that planar light can be emitted from only one of the light guide 71 and the light guide 72 or both. It is also possible to emit light or not emit light from both. Further, light guides 71 and 72 are provided corresponding to the light sources 31 and 32, respectively, and the boundary between the light guides 71 and 72 is mirror-finished. Exits from the light emitting surface 71 a without leaking to the light guide 72. Similarly, light entering the light guide 72 from the light source 32 is emitted from the light emitting surface 72 a without leaking to the light guide 72. Therefore, when only one of the light guides emits light, the boundary with the light guide that does not emit light becomes clear.

  FIG. 10 is a diagram illustrating an example of the state of the light guides 71 and 72 when the light source 31 is turned off and the light source 32 is turned on as an example. Only the light emitting surface 71a of the light guide 71 irradiated with light from the light source 31 is lit. In this way, the light source control unit 5 controls the turning on and off of the light source 31 and the light source 32, thereby clearly dividing the light emitting surface 71a of the light guide 71 that emits light and the light emitting surface 72a of the light guide 72 that does not emit light. can do. Note that the light source control unit 5 preferably controls turning on and off of the light source 31 and the light source 32 in accordance with an image displayed on the liquid crystal panel 6. For example, if it is not necessary to display an image on the entire screen of the liquid crystal panel and it is sufficient to display an image on half of the screen, the light source of the light guide that emits planar light to the half of the screen of the liquid crystal panel is turned off. Thus, power consumption can be saved.

  FIG. 11 is a diagram illustrating a modification of the backlight. The backlight 41 shown in FIG. 11 is used for a display of a mobile phone, for example. The backlight 41 includes four light sources 31, 32, 33, and 34 arranged in the vertical direction of the display, and four light guides 71, 72, 73, and 74 corresponding to the respective light sources are arranged. Has been. That is, the light emitting surface of the backlight 41 has the light emitting surfaces 71a, 72a, 73a, 74a of the four light guides 71, 72, 73, 74 arranged in the vertical direction. Thus, since a plurality of lines are formed by the plurality of light guides 71, 72, 73, 74, for example, only an arbitrary line can be displayed on the display.

  In the display of a mobile phone, for example, when all light sources are turned off during standby, the display becomes invisible. However, even when waiting, there is a case where it is desired to display a minimum display such as a clock display / mail incoming display, for example. In that case, it is possible to display necessary information by turning on only the light source corresponding to the portion (line) to be displayed. Thus, power consumption is saved by turning off the light sources in unnecessary areas.

  FIG. 12 is a diagram showing another modification of the backlight. The backlight 42 shown in FIG. 12 includes four light guides 71, 72, 73, and 74. Each light guide 71, 72, 73, 74 is adjacent to the other on two sides. Four light sources 31, 32, 33, 34 are provided corresponding to the four light guides 71, 72, 73, 74. The light source 31 and the light source 32 are disposed on the side surfaces of the light guides 71 and 72. The light sources 33 and 34 are disposed on the side surfaces of the light guides 73 and 74 facing the surface on which the light source 31 and the light source 32 are provided. The backlight 42 has four light emitting surfaces 71a, 72a, 73a, 74a.

  In the example shown in FIG. 12, one light source is provided for each light guide 71, 72, 73, 74, but two or more light sources are provided for each light guide 71, 72, 73, 74. It may be provided. In addition, the type and number of light sources can be changed for each light guide. Alternatively, the voltage applied to each light source can be changed for each light guide. Thereby, a plurality of light guides having different luminances can be formed. Further, the number of light guides is not limited to the above two and four.

(Embodiment 2)
FIG. 13 is a diagram showing a structure of a backlight in the second embodiment. The backlight 43 shown in FIG. 13 is different from the backlight 4 in the first embodiment in that the boundary surface 19 between the two light guides 71 and 72 is subjected to a light shielding process.

  The light shielding treatment can be performed, for example, by applying a light-shielding paint such as a black paint on the surface of the light guide. In addition, a film coated with a paint having a light shielding function can be attached to the surface of the light guide with an adhesive, or can be pressure-bonded to the surface of the light guide through a substance that can be cured by heat or pressure. Also good. In addition, for example, a light guide plate having two regions having a light shielding surface at the boundary is obtained by sandwiching and fixing a black film between two light guides.

  Such a light shielding process may be easier to process and may require fewer manufacturing steps than a mirror finish process. In other words, since the number of members used in the light shielding process and the process of the light shielding process are reduced as compared with the mirror surface treatment, the manufacturing cost may be reduced.

  Further, by performing the light shielding process on the boundary surface 19, irregular reflection of light at the boundary surface 19 can be suppressed. As a result, the boundary between the light guide 71 and the light guide 72 becomes clear. When the surface on the light guide 71 side and the surface on the light guide 72 side of the boundary surface 19 are reflection surfaces, the periphery of the boundary between the light guide 71 and the light guide 72 becomes brighter than other portions. The light emitted from the light emitting surface 71a of the light guide 71 and the light emitting surface 72a of the light guide 72 may be uneven. When the boundary surface 19 is subjected to a light shielding process, the periphery of the boundary between the light guide 71 and the light guide 72 does not become brighter than the other portions. Therefore, unevenness of the emitted light on the light emitting surface 71a and the light emitting surface 72a. Is less likely to occur.

(Embodiment 3)
FIG. 14A is a diagram illustrating a structure in which the light guide plate 70 according to the third embodiment is viewed from the light emitting surface side. FIG.14 (b) is sectional drawing which shows the cross section which follows the BB line in Fig.14 (a).

  A slit 15 is provided substantially at the center of the light guide plate 70 shown in FIGS. That is, the light guide plate 70 is divided into two regions 701 and 702 with the slit 15 as a boundary. Thus, the light guide plate 70 has two light emitting surfaces 701a and 701b.

  By inserting a member that reflects light or a member that blocks light into the slit 15, light can be prevented from leaking from the region 701 to the region 702 or from the region 702 to the region 701. For example, highly reflective aluminum or the like may be directly deposited in the slit 15, or a film or the like in which aluminum is deposited on both the front and back surfaces may be inserted into the slit 15. Thereby, light can be reflected at the boundary between the region 701 and the region 702.

  In addition, for example, a paint having a function of blocking light, such as a black paint, may be applied directly into the slit 15, or a film or the like having a paint applied on both sides may be inserted into the slit 15. Thereby, for example, light in the region 701 can be prevented from entering the region 702. In addition, light in the region 702 can be prevented from entering the region 701.

  In FIG. 14A, one slit 15 is provided. However, the light guide plate 7 may be provided with two or more slits 15 and the lighting region may be divided into three or more.

  As shown in the first and second embodiments, the light guide plate 70 according to the present embodiment is not configured to bond a plurality of light guides, and thus a process for bonding a plurality of light guides is not necessary in the manufacturing process. become. As a result, the manufacturing process is simplified, the manufacturing time is shortened, and the manufacturing cost is reduced. In addition, the size of the light guide plate handled in the manufacturing process is larger than in the first and second embodiments. This eliminates the need for fine operations in the manufacturing process and facilitates the handling of the light guide plate. As a result, the yield of the manufactured light guide plate is improved. Moreover, the process of crimping the film to the light guide can be omitted by inserting the film into the slit 15. Thereby, the manufacturing cost is reduced.

(Embodiment 4)
FIG. 15A is a diagram showing a structure viewed from the light emitting surface side of the backlight 44 in the fourth embodiment.

In the backlight 44 shown in FIG. 15A, the light guide plate 700 includes two light guides 711 and 712. Recesses 711 d and 712 d are provided in the respective light guides 711 and 712. Light sources 31 and 32 are installed in the recesses 711d and 712d. The side surfaces 712b ₃ , 712b ₂ , 711b ₂ , and 711b ₄ of the light guides 711 and 712 are mirror-finished. The boundary surface 19 of the light guides 711 and 712 is also subjected to mirror surface processing. Further, for example, a film 13a having aluminum or the like deposited on the surface is provided on the rear side where the light sources 31 and 32 do not emit light, that is, on the side surfaces 711b ₁ and 712b ₁ .

With such a configuration, light from the light source 31 can be prevented from leaking to the light guide 712. That is, the light emitted from the light source 31 into the light guide 711 is reflected on the boundary between the light guide 711 and the light guide 712 and on the inside of the side surfaces 711b ₁ , 711b ₂ , 711b ₄ , It is difficult to leak outside the light body 712 and the side surfaces 711b ₂ , 711b ₂ , and 711b ₄ . Similarly, the light emitted from the light source 32 to the light guide 712 has a structure that hardly leaks to the outside of the light guide 711 and the side surfaces 712b ₁ , 712b ₂ , and 712b ₃ .

  Thus, since the light from the light sources 31 and 32 is reflected inside the light guides 711 and 712, the luminance of the light emitted from the light emitting surfaces of the light guides 711 and 712 can be improved. As described above, the light sources 31 and 32 are provided in the concave portions of the light guides 711 and 712, and the side surfaces of the light guides 711 and 712 are covered with the reflecting member, so that the light emitted around the light sources 31 and 32 is guided to 711 and 712 can be reflected.

Further, as shown in FIG. 15 (b), the backlight 45 having the same structure as the backlight 44, can be disposed on the side surface 711b _1, 712b ₁ of the light guide 711 and 712. In this case, for example, a film 13b in which aluminum or the like is vapor-deposited on both front and back surfaces can be provided between the backlight 44 and the backlight 45.

As described above, in Embodiments 1 to 4, an example in which a point light source such as a light emitting diode is used as the light source has been described. However, the light source is not limited to a point light source. For example, the same effect can be obtained even when a linear light source such as a cold cathode tube is used as the light source. FIG. 16 is a diagram illustrating an example of the backlight 45 when the light source of the backlight 44 illustrated in FIG. 15A is replaced by the cold cathode tubes 301 and 302. Concave portions 721d and 722d are provided on the side surfaces 721b ₁ and 722b ₁ of the two light guides 721 and 722 constituting the backlight 45, respectively. Cold cathode fluorescent lamps 301 and 302 are disposed in the recesses 721d and 722d.

  As described above, the display device described in Embodiments 1 to 4 provides the following effects. In an image display device including a plurality of light sources, the light guide plate has a boundary, and a light shielding member or a reflection member is provided at the boundary. Therefore, the light in the light guide plate does not exceed the boundary. As a result, the boundary between the lighting region and the non-lighting region becomes clear. As a result, it is possible to achieve power saving by controlling the number of lighting of the light sources while maintaining high display quality. In addition, since light that has been leaked in the past is reflected at the boundary surface, light leakage to the non-lighting area is reduced, and an improvement in luminance can be realized as compared with the prior art.

  In the above embodiment, the sidelight (edge light) type backlight in which the light source is provided on the side surface of the light guide plate has been described. However, the surface light source device of the present invention is not limited to the sidelight type. The present invention can also be applied to, for example, a direct type backlight in which a light source is provided on the side opposite to the side where the liquid crystal panel is provided in the light guide plate. For example, when a direct-type surface light source device is used for a liquid crystal television, current consumption can be reduced by turning off the light sources of blocks displaying black on a screen with many black displays. Further, the surface light source device of the present invention can be used not only as a backlight but also as a front light.

  In the above-described embodiment, the liquid crystal display device using the liquid crystal panel as the image display unit has been described. However, the surface light source device according to the present invention is used in addition to the liquid crystal display device. The present invention is, for example, a light box for illuminating X-ray photographs, a light box for illuminating photographic negatives, etc., for easy viewing, and a light-emitting device for illuminating advertisements and the like installed on signboards and wall surfaces in station buildings. It can use suitably as an illuminating device (backlight).

  The surface light source device and the image display device according to the present invention are useful as a surface light source device and an image display device that save power consumption while maintaining high display quality.

1A is a perspective view illustrating a schematic structure of a liquid crystal display device according to Embodiment 1. FIG. (B) is a side view of the liquid crystal display device shown to (a). It is a figure which shows typically the structure at the time of seeing the backlight 4 from the light emission surface 71a, 72a side. (A) is a figure which shows the state which the two light guides 71 and 72 which comprise the backlight 4 isolate | separated. (B) is a side view of the light guide 72 and the light source 32 shown in (a). (A) is a figure which shows a mode that the film 13 is pinched | interposed with two light guides. (B) is a view showing a mold 14. (C) is a figure which shows the light-guide plate 7 which has the two light guides 71 and 72. FIG. (A) is a figure which shows the example of the backlight using a wedge-shaped light-guide plate, (b) is a side view of the backlight shown to (a). It is a figure which shows an example of the mechanism for the light source control part 5 to control the light sources 31 and 32. FIG. (A) is a figure which shows an example of the detailed circuit structure of the structure shown in FIG. (B) is a figure which shows the modification of the circuit structure shown to Fig.7 (a). (A) is a figure which shows the other example of the detailed circuit structure of the structure shown in FIG. (B) is a figure which shows the example of the time transition of the voltage in the terminal 52a of the switch 52 controlled by PWM input. FIG. 7 is a diagram showing still another example of a detailed circuit configuration of the configuration shown in FIG. 6. It is a figure which shows the example of the state of the light guides 71 and 72 when the light source 32 is light-extinguished and the light source 31 is lighted. It is a figure which shows the other modification of a backlight. It is a figure which shows the other modification of a backlight. 6 is a diagram showing a structure of a backlight 43 in Embodiment 2. FIG. (A) is a figure which shows the structure which looked at the light-guide plate 7 concerning Embodiment 3 from the light emission surface side. (B) is sectional drawing which shows the cross section which follows the BB line in (a). (A) is a figure which shows the structure seen from the light emission surface side of the backlight in Embodiment 4. FIG. (B) is a diagram showing an example of installing the backlight 45 having the same structure as the backlight 44, the side surface 711b _1, 712b ₁ of the light guide 711 and 712. It is a figure which shows the structure of the modification of a backlight.

Explanation of symbols

31, 32, 33, 34 Light source 4, 41, 42, 43, 44, 45 Backlight 5 Light source control unit 6 Liquid crystal display unit 7, 70, 700 Light guide plate 8 Substrate 91, 92 Control switch 10 Power supply 13 Film 14 Type 15 Slit 16 Cold cathode tube 19 Interface 20 Liquid crystal display device 21 Variable resistor 22, 23, 24, 25, 26, 27 Resistor 61 Operational amplifier 62, 63 Capacitor 51, 52, 54 Switch 71, 72, 73, 74 Light guide 711 , 712, 721, 722, 731, 732

Claims (4)

Multiple light sources;
A light source control unit for controlling turning on and off of each of the plurality of light sources;
A light guide plate having a light emitting surface that emits light emitted from the plurality of light sources as planar light,
The light guide plate is divided into a plurality of regions, and a light shielding surface or a reflection surface is provided on at least a part of a boundary surface of the plurality of regions,
A surface light source device in which at least one light source is arranged corresponding to each of the plurality of regions.   The surface light source device according to claim 1, wherein a slit is formed at a boundary between the plurality of regions in the light guide plate, and a light shielding unit or a reflection unit is provided in the slit. The plurality of light sources are disposed in recesses provided on at least one surface of the light guide plate in each of the plurality of regions.
The light guide plate reflects light from the light source disposed in the recess to prevent light from the light source disposed in the recess from leaking to the outside of the light guide plate, or reflects light from the light source disposed in the recess to the inside of the light guide plate. The surface light source device according to claim 1, further comprising reflecting means for causing the surface light source device to. An image display unit;
Multiple light sources;
A light source control unit for controlling turning on and off of each of the plurality of light sources;
A light guide plate having a light emitting surface for irradiating the image display unit with light emitted from the plurality of light sources as planar light,
The light guide plate is divided into a plurality of regions, and a light shielding surface or a reflection surface is provided on at least a part of a boundary surface of the plurality of regions,
An image display device in which at least one of the light sources is arranged corresponding to each of the plurality of regions.

Images