JP2011186499A - Lighting device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device which efficiently utilizes light of a light source and can be constituted of a small number of components, and a liquid crystal display device having improved brightness (luminance). <P>SOLUTION: The lighting device is configured to include: a tabular light guide plate; a light source part disposed on a side of the light guide plate; and a polarization separation element which is disposed between the light guide plate and the light source part and transmits linearly polarized light in a first polarization direction and reflects linearly polarized light in a polarization direction orthogonal to the first polarization direction. Furthermore, the lighting device includes a phase modulation element between the light source part and the polarization separation element. The liquid crystal display device includes the lighting device and a liquid crystal panel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an illumination device that irradiates light to a liquid crystal panel and a liquid crystal display device using the illumination device.

  A liquid crystal display device is widely used as a display of a portable information terminal because it is thin and light and has low power consumption. A liquid crystal display device requires a lighting device because a liquid crystal panel which is a constituent element thereof is not a self-luminous element. The lighting device includes a so-called backlight disposed on the back side of the liquid crystal panel (that is, the side opposite to the viewer) and a so-called front light disposed on the front side of the liquid crystal panel (that is, the viewer side). . When the liquid crystal panel is a transmissive type, a backlight is used, and when the liquid crystal panel is a reflective type, a front light is used. A reflective liquid crystal panel is basically an element that does not require a lighting device, but it is difficult to see in a situation where there is little light, and recently, a front panel is often placed on the front. ing.

  In a liquid crystal display device used for a portable information terminal, since the illumination device also needs to be thin, a linear light source such as a cold cathode tube is provided on a side of a flat light guide plate formed of a transparent member as a reflector ( A so-called side light type (also referred to as an edge light type) illumination device that is disposed together with the reflector is used. In such a sidelight type illumination device, the light emitted from the linear light source is incident directly or indirectly from the side surface of the light guide plate after being reflected by the reflector. The light that has entered the light guide plate propagates through the light guide plate and is emitted from the upper surface side (in the case of a backlight) or the lower surface side (in the case of a front light) of the flat light guide plate, and the upper surface of the light guide plate (illumination device). Incident on the liquid crystal panel arranged on the side or the lower surface side.

  Since light emitted from a light source such as a cold cathode tube is usually randomly polarized light (non-polarized light), light emitted from the light guide plate is also randomly polarized light. However, the liquid crystal panel is usually provided with a polarizer on the incident side (and the outgoing side) so that only predetermined linearly polarized light is incident on the liquid crystal panel. Therefore, only about half of the random polarized light that exits the light guide plate and enters the liquid crystal panel is actually incident on the liquid crystal panel and used for display, and the light use efficiency is poor. The display of a portable information terminal is required to have high brightness. In order to achieve high brightness with this conventional configuration, it is sufficient to increase the amount of light emitted from a light source such as a cold-cathode tube. However, this increases power consumption, and in particular, a battery-driven portable information terminal or the like It will no longer be suitable as a display.

  As a means for solving such a problem, there is a technique in which light emitted from the light guide plate and incident on the liquid crystal panel is linearly polarized light, and most of the light emitted from the illumination device is incident on the liquid crystal panel and used. For example, in Japanese Patent Laid-Open No. 9-73083, in a sidelight type illumination device, a polarization separating means comprising a supplementary light guide plate, a cholesteric liquid crystal sheet, and polyvinyl alcohol (PVA) are provided between the light source and the light guide plate from the light source side. The structure which arrange | positions a phase conversion means is disclosed. In this prior art, the first circularly polarized light is transmitted and the second circularly polarized light is reflected by the polarization separating means made of a cholesteric liquid crystal sheet, and the transmitted first circularly polarized light is converted to linearly polarized light by the phase converting means. Incident light. In addition, in order to prevent the influence due to the incident angle dependency of the polarization separating means, an auxiliary light guide plate for arranging the angles of light incident on the polarization separating means is arranged. On the other hand, the reflected second circularly polarized light returns to the light source side, is reflected by the surface of the light source, a reflector or the like, becomes circularly polarized light whose polarity is reversed (that is, the first circularly polarized light), and passes through the polarization separating means. .

  Therefore, in this conventional illumination device, it is possible to introduce and use more than half of the light from the light source into the light guide plate.

  However, in the conventional illumination device described above, an auxiliary member such as an auxiliary light guide plate for controlling the incident angle to the polarization separating means is necessary in order to prevent the influence due to the incident angle dependency of the polarization separating means for separating the circularly polarized light. Become. In the above document, a configuration in which such an auxiliary member (auxiliary light guide plate) is not provided is also disclosed. However, in practice, if an auxiliary member is not provided, a desired effect (increased utilization efficiency of light source light) is disclosed. Cannot be obtained. Therefore, the above-described conventional technology has a problem that the number of parts increases, it is impossible to realize a reduction in size and weight, and it is difficult to manufacture at a low cost.

  In view of the above problems, an object of the present invention is to provide an illuminating device that has high light source light utilization efficiency and can be configured with a small number of components, and a liquid crystal display device with improved brightness (luminance).

  According to the viewpoint of this invention, the said subject is solved by the illuminating device and liquid crystal display device which have the following characteristics.

  That is, a flat light guide plate, a light source unit disposed on the side of the light guide plate, a light guide plate disposed between the light guide plate and the light source unit, transmits linearly polarized light in the first polarization direction, and the first polarization An illumination device including a polarization separation element that reflects linearly polarized light in a polarization direction orthogonal to the direction, and a liquid crystal display device using the illumination device.

  As described above, according to the present invention, the utilization efficiency of the light source light of the illumination device is improved with a configuration having a small number of parts that can be manufactured at low cost, and the brightness (luminance) of the liquid crystal display device is improved. There is an effect that it becomes possible.

It is a figure explaining the principle of this invention. It is a figure which shows the 1st Embodiment of this invention. It is a figure which shows the 2nd Embodiment of this invention. It is a figure which shows the 3rd Embodiment of this invention. It is a figure which shows the 4th Embodiment of this invention. It is a figure which shows the 5th Embodiment of this invention. It is a figure which shows the 6th Embodiment of this invention. It is a figure which shows the 7th Embodiment of this invention. It is a figure which shows the 8th Embodiment of this invention. It is a figure which shows the 9th Embodiment of this invention. It is a figure which shows the 10th Embodiment of this invention. It is a figure which shows a light source part provided with a cold cathode tube. It is a figure which shows a light source part provided with LED. It is a figure explaining the light in a columnar light guide. It is a figure explaining the light in a columnar light guide. It is a figure explaining the reflected light in a polarization separation sheet. It is a figure explaining the reflected light in a polarization separation sheet. It is a figure explaining the light in a light guide. It is a figure explaining the emitted light of a light-guide plate, and the transmission axis of a polarizer. It is a figure which shows the structural example of an optical element. It is a figure which shows the relationship of the angle of the polarization direction of linearly polarized light, and the optical axis of a polarizer. It is a figure which shows the polarization direction of the emitted light of a polarization separation element, and the emitted light of a light-guide plate.

(Principle of the present invention)
FIG. 1 is a principle diagram of the present invention. The light L1 emitted from the light source unit 2 is non-polarized light. The light L1 passes through the phase modulation element 4 to become light L2 (unpolarized similarly to the light L1), transmits light in the first polarization direction, and light in the second polarization direction orthogonal to the first polarization direction. Is incident on the polarization separation element 6 that reflects the light. The polarization separation element 6 transmits the first linearly polarized light L3 and reflects the second linearly polarized light L4 whose polarization direction is orthogonal to the linearly polarized light L3. The linearly polarized light L3 goes to a light guide plate (not shown). The linearly polarized light L4 enters the phase modulation element 4 and is converted into circularly polarized light L5, and the circularly polarized light L5 returns to the light source unit 2.

  The light L5 that has returned to the light source unit 2 is repeatedly reflected inside the light source unit 2 and becomes unpolarized light L1 again and is emitted from the light source unit 2. Then, as described above, half of the light, that is, the first linearly polarized light L3 is transmitted through the polarization separation element 6 toward the light guide plate, and the remaining light, that is, the second linearly polarized light returns to the light source unit 2 again. By repeating this, most of the light emitted from the light source unit 2 enters the light guide plate and can be used.

  In addition, when the circularly polarized light L5 is reflected once by the light source unit 2 and emitted from the light source unit 2, the circularly polarized light L5 is converted into a linearly polarized light (first linearly polarized light) by the phase modulation element 4 because the circularly polarized light is reversed. It passes through the separation element 6 as it is.

  In the above description, the phase modulation element 4 is provided between the light source unit 2 and the polarization separation element 6, but the phase modulation element 4 may be omitted.

(Embodiment of the present invention)
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to what has the same function, and the detailed description is abbreviate | omitted.

  FIG. 2 is a diagram showing the illumination device 110 according to the first embodiment of the present invention. The illumination device 110 is a front light type illumination device, and includes a flat light guide plate 30, a polarization separation sheet 20 serving as a polarization separation element, and a linear light source unit 10 disposed on one side surface of the light guide plate 30. . The polarization separation sheet 20 is disposed between the light source unit 10 and the light guide plate 30. For example, as shown in FIG. 12A, the linear light source unit 10 includes a cold cathode tube 12 that is a linear light source and a reflector 14 that is a reflecting member. The reflector 14 is made of aluminum, for example, and is disposed so as to surround the cold cathode tube 12 except for the light emission side. In FIG. 1 and the subsequent figures, the light source unit 10 is simplified and only the cold cathode tube 12 is shown.

  The light from the cold cathode tube 12 is generally unpolarized light, and the light reflected by the reflector 14 is also unpolarized light. As shown in FIG. 12B, the light emitted from the cold cathode tube 12 exits the light source unit 10 directly or after being reflected by the reflector 14, and enters the polarization separation sheet 20. (Note that FIG. 12B shows a phase modulation element (quarter-wave sheet 40) disclosed in an embodiment to be described later.) The polarization separation sheet 20 is commercially available. A sheet (for example, one sold by 3M under the trade name D-BEF) can be used. The light incident on the polarization separation sheet 20 transmits linearly polarized light having a predetermined polarization direction, and reflects linearly polarized light having a polarization direction orthogonal thereto. The predetermined direction, that is, the polarization direction of transmitted linearly polarized light is determined by the arrangement direction of the optical axis of the polarization separation sheet. The other linearly polarized light reflected by the polarization separation sheet 20 returns to the light source unit 10, partly toward the cold cathode tube 12, and the rest toward the reflector 14. The light incident on the cold cathode tube 12 is secondarily emitted by the phosphor of the cold cathode tube 12, becomes non-polarized light again and enters the polarization separation sheet 20, and only desired linearly polarized light is transmitted. The linearly polarized light orthogonal thereto is reflected and returns to the light source unit 10 again. By repeating this, almost all light passes through the polarization separation sheet 20 and travels toward the light guide plate 30. Here, “almost all” is because there are actually a loss at the interface, a loss at the time of reflection, a loss at the time of secondary light emission, and the like, which are not repeated infinitely.

  The linearly polarized light transmitted through the polarization separation sheet 20 enters the light guide plate 30. The polarizing plate 30 is a light guide plate of a front light type illumination device. For example, as shown in FIG. 18, two types of inclined surfaces 32 having different inclination angles on the upper surface side (viewing side when used with a reflective liquid crystal panel) and 34 is formed, and the lower surface side (the liquid crystal panel side when used with a reflective liquid crystal panel) is a flat surface 36. Of the light incident on the light guide plate 30 (light enters from the left in the figure), the light incident on the inclined surface 32 with a small inclination angle propagates through the light guide plate by total reflection and reaches the inclined surface 34 with a large inclination angle. The incident light is reflected and emitted from the lower surface 36 to the outside of the light guide plate 30. If the light incident on the light guide plate 30 is linearly polarized light, the polarization state is maintained in the light guide plate 30, so that the emitted light from the light guide plate 30 is similarly linearly polarized light.

  Therefore, as in the first embodiment, only the polarization separation element is disposed between the light source unit and the light guide plate, and the reflected light from the polarization separation element is reused to linearly polarize the incident light to the light guide plate. As a result, the light emitted from the light guide plate can be converted into linearly polarized light, so that a lighting device with high light utilization efficiency can be configured with a small number of components.

  FIG. 3 is a diagram showing a lighting device 120 according to the second embodiment of the present invention. The configuration is similar to the illumination device 110 of the first embodiment described above, and the difference is the configuration of the light source unit 50. The detailed configuration of the light source unit 50 is shown in FIG. As shown to Fig.13 (a), the light source part 50 has the columnar light guide 52 which consists of a substantially quadrangular prism-shaped transparent member, and the dotted | punctate light emission part 51 used as the dotted | punctate light emission part arrange | positioned at the both ends. Is provided. The point light emission part 51 is comprised by the light emitting diode (LED: lightingdiode diode) which can be obtained cheaply, for example. In the columnar light guide 52, one of the four side surfaces is a flat emission surface 54, and the other side surface facing the emission surface 54 is a prism surface 53. The remaining two side surfaces are flat surfaces.

  As shown in FIG. 14, the prism surface 53 is provided with a reflective layer 57 made of a metal film or a multilayer film as a reflective member. Therefore, the light that has entered the columnar light guide 52 from the point light emitter 51 is provided on the prism surface 53 regardless of the angle of incidence on the prism surface 53, as shown in FIGS. Since the light is reflected by the reflective layer 57, the light exits from the exit surface 54 without being invalidated and travels toward the polarization separation sheet 20. Since the light emitted from the LED of the point light emitting unit 51 is generally non-polarized light, the light emitted from the columnar light guide 52 is also non-polarized light.

  The non-polarized light emitted from the columnar light guide 52 is transmitted through the polarization separation sheet 20 only with predetermined linearly polarized light, and the orthogonally linearly polarized light returns to the columnar light guide 52 as shown in FIG. . The light that has returned to the columnar light guide 52 is incident on the prism surface 53, and as shown in FIG. 16A, a part of the light is reflected by the reflective layer 57 to be converted to non-polarized light, and is again emitted. The light exits from 54 and enters the polarization separation sheet 20. The polarized light separating sheet 20 transmits only light having predetermined linear polarization and reflects light having orthogonal linear polarization. Repeat this.

  In addition, as shown in FIG. 16B, the other part of the light returning to the columnar light guide 52 is reflected by the reflection layer 57 and further totally reflected by the emission surface 54 to be inside the columnar light guide 52. Is incident on the point light-emitting portion 51 while propagating through the columnar light, becomes non-polarized light by secondary light emission, exits again from the exit surface 54 while propagating through the columnar light guide 52, and enters the polarization separation sheet 20. The polarized light separating sheet 20 transmits only light having predetermined linear polarization and reflects light having orthogonal linear polarization. Repeat this.

  As described above, in the light source unit 50 of the present embodiment, almost all of the light emitted from the point light-emitting unit 51 passes through the columnar light guide 52 and the polarization separation sheet 20 and is converted into linearly polarized light. 30 is incident. The polarizing plate 30 outputs the linearly polarized light while maintaining the polarization state of the incident light. Therefore, the illumination device 120 of the present embodiment has the same operations and effects as those of the first embodiment described above.

  In addition, as the point light emission part 51, another structure is also applicable. For example, as shown in FIG. 13B, a configuration in which a phosphor 55 is applied to the end surface of the columnar light guide 52 and a point light source such as an LED 56 is disposed thereon is further possible. ), A configuration in which point light sources such as a plurality of LEDs 56 are arranged on one end face of the columnar light guide 52 is also possible. In the case of the configuration shown in FIG. 13C, the wavelength of the plurality of point light sources may be the same or different.

  Further, the columnar light guide 52 is not limited to a rectangular column shape, and other polygonal column shapes can be applied. In this case, at least one side surface may be an emission surface, and a reflecting member or a prism surface (or both) may be provided on at least one other side surface.

  FIG. 4 is a diagram showing a liquid crystal display device 140 according to the third embodiment of the present invention. The liquid crystal display device 140 is a reflective liquid crystal display device, which is disposed on the front surface of the reflective liquid crystal panel 70 and includes the light source unit 10, the polarization separation sheet 20, and the light guide plate 30. And a front light type illumination device 110 in the form. The lighting device 110 emits light from the front surface of the liquid crystal panel 70, and the light reflected by the liquid crystal panel 70 passes through the light guide plate 30 of the lighting device 110. Therefore, the display on the liquid crystal panel 70 is viewed through the light guide plate 30.

  Here, a polarizer is provided on the front side (incident side) of the liquid crystal panel 70, and the polarization axis of the polarizer is provided in the longitudinal direction of the liquid crystal panel 70 (longitudinal direction of the linear light source unit 10). It has been. Therefore, it is necessary to match the polarization direction of linearly polarized light that exits the light guide plate 30 and enters the liquid crystal panel 70 with the transmission axis direction of the polarizer. FIG. 21 is a diagram illustrating an angle relationship between the polarization direction of linearly polarized light and the optical axis of the polarizer. The horizontal axis indicates the angle of the polarization direction of linearly polarized light incident on the polarizer, the 90 degree direction corresponds to the light shielding axis direction of the polarizer, and the 180 degree direction (in this embodiment, the longitudinal direction of the liquid crystal panel) That is, the longitudinal direction of the linear light source unit) corresponds to the transmission axis direction of the polarizer. The vertical axis represents the extinction ratio obtained by standardizing the transmitted light amount of the outgoing light (transmitted light or reflected light) from the liquid crystal panel with the maximum transmitted light amount. From the figure, it can be seen that the maximum amount of transmitted light is obtained when the polarization direction of the linearly polarized light substantially coincides with the transmission axis of the polarizer. In other words, if the polarization direction of linearly polarized light is deviated from the transmission axis of the polarizer, a loss due to absorption by the polarizer occurs.

  Therefore, in this embodiment, by adjusting the polarization direction of the linearly polarized light transmitted through the polarization separation sheet 20, the polarization direction of the light emitted from the light guide plate 30 and the transmission axis of the polarizer on the front surface of the liquid crystal panel 70 are substantially coincident. Like to do. That is, when the polarization separation sheet 20 is cut out from a large sheet, for example, the longitudinal direction of the polarization separation sheet 20 and the polarization direction of the transmitted light are substantially parallel (horizontal direction) so that the polarization direction of the transmitted light becomes a predetermined direction. Cut out so that Here, the predetermined direction means that when the linearly polarized light transmitted through the polarization separation sheet 20 enters the polarizer of the liquid crystal panel 70 through the light guide plate 30, the polarization direction of the linearly polarized light substantially coincides with the transmission axis of the polarizer. This is the direction.

  FIG. 22 is a diagram illustrating the polarization directions of the outgoing light from the polarization separation element (polarization separation sheet 20) and the outgoing light from the light guide plate (light guide plate 30). The horizontal axis indicates the angle of each outgoing light, and indicates the angle with respect to the transmission axis of the polarizer. The arrangement direction of the transmission axis of the polarizer is as described above. The vertical axis represents the extinction ratio obtained by normalizing the transmitted light amount of the outgoing light (transmitted light or reflected light) from the liquid crystal panel (liquid crystal panel 70) with the maximum transmitted light amount. From the figure, it can be seen that in the present embodiment, the polarization characteristics of the outgoing light from the polarization separation sheet 20 and the polarization characteristics of the outgoing light from the light guide plate 30 substantially match. That is, it can be seen that the polarization state of the linearly polarized light incident on the light guide plate 30 is maintained.

  As described above, in the liquid crystal display device 140 according to the present embodiment, the illumination device 110 with high light use efficiency is used, and the light from the illumination device 110 is incident on the liquid crystal panel 70 efficiently without loss. Since the light transmission direction of the separation sheet 20 and the transmission axis direction of the polarizer of the liquid crystal panel 70 are set, a bright liquid crystal display device can be realized.

  In the present embodiment, as the lighting device, the lighting device 120 shown in the second embodiment can be used. As the reflective liquid crystal panel 70, various types of reflective liquid crystal panels can be used in addition to a TN (twisted nematic) mode liquid crystal panel, a VA (vertically aligned) mode liquid crystal panel, and the like.

  FIG. 5 is a diagram showing a liquid crystal display device 150 according to the fourth embodiment of the present invention. The liquid crystal display device 150 is a transmissive liquid crystal display device, and includes a transmissive liquid crystal panel 90 and an illuminating device that is disposed on the back surface thereof and uses the illuminating device 120 of the second embodiment described above as a backlight type. . In the backlight type illumination device, the illumination device 120 of the second embodiment, the light source unit 50, and the polarization separation sheet 20 are common, but the light guide plate 80 is different. The light guide plate 80 is formed with a diffusion pattern for diffusing light incident on the rear surface toward the upper surface (front surface), and a reflector is disposed on the rear surface side. The light is emitted from the upper surface of the light guide plate 80 as an emission surface, and the light emitted from the light guide plate 80 enters from the back surface of the transmissive liquid crystal panel 90. Therefore, the display on the liquid crystal panel 90 directly looks at the front surface of the liquid crystal panel 90. The function of the light guide plate 80 is the same as that of the light guide plate 30 of the above-described embodiment, and light linearly polarized by the light source unit 50 and the polarization separation sheet 20 is incident and emitted while maintaining the polarization state.

  Here, as in the above-described embodiment, a polarizer is provided on the incident side (back side) of the liquid crystal panel 90. Therefore, also in this embodiment, when the linearly polarized light transmitted through the polarization separation sheet 20 enters the polarizer of the liquid crystal panel 70 through the light guide plate 30, the polarization direction of the linearly polarized light substantially coincides with the transmission axis of the polarizer. As described above, the arrangement direction of the polarizers on the incident side of the polarization separation sheet 20 and the liquid crystal panel 90 is determined.

  As described above, in the liquid crystal display device 150 of the present embodiment, similarly to the liquid crystal display device 140 described above, an illumination device with high light use efficiency is used, and light from the illumination device is efficiently lost without loss. Since the light transmission direction of the polarization separation sheet 20 and the transmission axis direction of the polarizer of the liquid crystal panel 90 are set so as to enter the panel 90, a bright liquid crystal display device can be realized.

  Also in this embodiment, it is possible to use a lighting device in which the lighting device 110 described in the first embodiment is applied to a backlight type lighting device. As the transmissive liquid crystal panel 90, transmissive liquid crystal panels of various modes can be used as in the above-described embodiment.

  FIG. 6 is a diagram showing a lighting device 160 according to the fifth embodiment of the present invention. The illuminating device 160 is a front light type illuminating device and has a configuration similar to that of the illuminating device 110 of the first embodiment described above, except that phase modulation is performed between the light source unit 10 and the polarization separation sheet 20. A quarter-wave sheet 40 serving as an element is disposed.

  In the present embodiment, as shown in FIG. 12B, the non-polarized light emitted from the cold cathode tube 12 is emitted from the light source unit 10 directly or after being reflected by the reflector 14, for 4 minutes. The light enters and transmits the one-wavelength sheet 40 and enters the polarization separation sheet 20. As the polarized light separating sheet 20, a commercially available sheet (for example, one sold by 3M under the trade name D-BEF) can be used. The light incident on the polarization separation sheet 20 transmits linearly polarized light having a predetermined polarization direction, and reflects linearly polarized light having a polarization direction orthogonal thereto. The predetermined direction, that is, the polarization direction of transmitted linearly polarized light is determined by the arrangement direction of the optical axis of the polarization separation sheet. The linearly polarized light reflected by the polarization separation sheet 20 enters the quarter-wave sheet 40, is converted into circularly polarized light, and returns to the light source unit 10. A part of the circularly polarized light returning to the light source unit 10 goes to the cold cathode tube 12 and the rest goes to the reflector 14. The circularly polarized light that has entered the cold cathode tube 12 is secondarily emitted by the phosphor of the cold cathode tube 12 and then becomes non-polarized light and is emitted from the light source unit 10 again. The emitted non-polarized light passes through the quarter-wave sheet 40 and then enters the polarization separation sheet 20, where only predetermined linearly polarized light is transmitted again, and linearly polarized light orthogonal thereto is reflected. Return to the light source unit 10 again. The circularly polarized light incident on the reflector 14 becomes reverse circularly polarized light when reflected by the reflector 14, and exits the light source unit 10 in this state. The reverse circularly polarized light emitted from the light source unit 10 enters the quarter-wave sheet 40 and is converted into linearly polarized light. The polarization direction of the converted linearly polarized light is a direction orthogonal to the polarization direction of the linearly polarized light reflected and returned by the polarization separation sheet 20. That is, the light is linearly polarized light that passes through the polarization separation sheet 20. Therefore, the linearly polarized light converted by the quarter-wave sheet 40 passes through the polarization separation sheet 20 as it is and travels toward the light guide plate 30.

  By repeating this, almost all of the light emitted from the light source unit 10 passes through the polarization separation sheet 20 and travels toward the light guide plate 30. Here, “almost all” is because there are actually a loss at the interface, a loss at the time of reflection, a loss at the time of secondary light emission, and the like, which are not repeated infinitely. However, in the present embodiment, the phase modulation element (quarter wavelength sheet 40) is disposed between the light source unit and the polarization separation element (polarization separation sheet 20). Therefore, of the linearly polarized light reflected and returned by the polarization separation element, the light that is converted into circularly polarized light by the phase modulation element, reflected by the reflector of the light source unit, and incident on the phase modulation element again is the polarization separation element. Therefore, it is possible to go to the light guide plate only by returning to the light source unit once. Therefore, since reflection, transmission, secondary light emission, and the like at each element are not repeated many times, loss due to them is small, and light reuse efficiency is improved. Therefore, the present embodiment (configuration in which the phase modulation element is disposed between the light source unit and the polarization separation element) further improves the light use efficiency compared to the first to third embodiments described above. When combined with a liquid crystal panel, a brighter liquid crystal display panel can be realized.

  FIG. 7 is a diagram showing a lighting device 170 according to the sixth embodiment of the present invention. The illuminating device 170 is a front light type illuminating device, and has a configuration similar to that of the illuminating device 120 of the second embodiment described above, except that phase modulation is performed between the light source unit 50 and the polarization separation sheet 20. A quarter-wave sheet 40 serving as an element is disposed. Further, it is similar to the illumination device 160 of the fifth embodiment described above, and the difference is the configuration of the light source unit 50. The configuration of the light source unit 50 is as described above.

  In the present embodiment, as shown in FIG. 17, the non-polarized light emitted from the columnar light guide 52 is incident on and transmitted through the quarter-wave sheet 40, and the polarization separation sheet 20 performs predetermined linear polarization. , And the orthogonally polarized light passes through the quarter-wave sheet 40 and returns to the columnar light guide 52. The light that has returned to the columnar light guide 52 passes through the quarter-wave sheet 40 and becomes circularly polarized light. The circularly polarized light returning to the columnar light guide 52 is incident on the prism surface 53, and as shown in FIG. 17A, a part of the light becomes reverse circularly polarized light when reflected by the reflective layer 57. Then, the light is emitted from the emission surface 54 again. The reverse circularly polarized light emitted from the emission surface 54 passes through the quarter-wave sheet 40 and is converted into linearly polarized light. The polarization direction of the converted linearly polarized light is a direction orthogonal to the polarization direction of the linearly polarized light reflected and returned by the polarization separation sheet 20. That is, the light is linearly polarized light that passes through the polarization separation sheet 20. Therefore, the linearly polarized light converted by the quarter-wave sheet 40 passes through the polarization separation sheet 20 as it is and travels toward the light guide plate 30.

  In addition, as shown in FIG. 17B, the other part of the circularly polarized light that has returned to the columnar light guide 52 is reflected by the reflective layer 57 and further totally reflected by the emission surface 54, so that the columnar light guide. The light is incident on the point light emitting part 51 while propagating through the body 52, becomes non-polarized light by the secondary light emission, and is emitted again from the emission surface 54 while propagating through the columnar light guide 52. The light passes through the sheet 40 and enters the polarization separation sheet 20. The polarized light separating sheet 20 transmits only light having predetermined linear polarization and reflects light having orthogonal linear polarization. Repeat this.

  As described above, also in the present embodiment, the phase modulation element (quarter wavelength sheet) is provided between the light source unit and the polarization separation element (polarization separation sheet 20), as in the fifth embodiment. 40) is arranged. Therefore, of the linearly polarized light reflected and returned by the polarization separation element, the light that is converted into circularly polarized light by the phase modulation element, is reflected by the light source unit, and is incident on the phase modulation element again is transmitted through the polarization separation element. Therefore, it is possible to go to the light guide plate only by returning to the light source unit once. Therefore, since reflection, transmission, secondary light emission, and the like at each element are not repeated many times, loss due to them is small, and light reuse efficiency is improved. Therefore, also in this embodiment, compared with the first and second embodiments described above, the light utilization efficiency is further improved, and when combined with a liquid crystal panel, a brighter liquid crystal display panel can be realized. .

  FIG. 8 is a diagram showing a liquid crystal display device 180 according to the seventh embodiment of the present invention. The liquid crystal display device 180 is a reflective liquid crystal display device and has a configuration similar to that of the liquid crystal display device 140 of the third embodiment described above, but the difference is that the front light type illumination device is the fifth embodiment. It is a point using the illumination device 160 of the form.

  In the present embodiment, since illumination device 160 of the fifth embodiment is used as the illumination device, a liquid crystal display device that is brighter than liquid crystal display device 140 of the third embodiment can be realized. it can.

  In this embodiment, as the lighting device, the lighting device 170 shown in the above-described sixth embodiment can be used. As the reflective liquid crystal panel 70, various modes of reflective liquid crystal panels can be used in addition to the TN (twisted nematic) mode liquid crystal panel and VA (vertically aligned) mode liquid crystal panel. It is the same as the form.

  FIG. 9 is a diagram showing a liquid crystal display device 190 according to the eighth embodiment of the present invention. The liquid crystal display device 190 is a transmissive liquid crystal display device and has a configuration similar to that of the liquid crystal display device 150 of the fourth embodiment described above, but the difference is that the backlight type illumination device is the sixth embodiment. The illumination device 170 of the embodiment is a backlight type illumination device.

  In the present embodiment, since the illumination device 170 of the sixth embodiment is used as the illumination device, it is possible to realize a brighter liquid crystal display device than the liquid crystal display device 150 of the fourth embodiment. it can.

  Also in this embodiment, as the lighting device, the lighting device 160 shown in the fifth embodiment described above can be applied to a backlight type lighting device, and a transmission type can be used. As the liquid crystal panel 90, a transmissive liquid crystal panel of various modes can be used as in the above-described embodiment.

  FIG. 10 is a diagram showing a liquid crystal display device 200 according to the ninth embodiment of the present invention. The liquid crystal display device 200 is a transmissive liquid crystal display device and has a configuration similar to that of the liquid crystal display device 190 of the above-described eighth embodiment, but the difference is between the light guide plate 80 and the transmissive liquid crystal panel 90. The half-wave sheet serving as the second phase modulation element is disposed.

  Further, in the liquid crystal display device 200, the direction of the transmission axis of the polarizer provided on the incident side of the liquid crystal panel 90 is different from that of the above-described embodiment. That is, in the liquid crystal panel of the above-described embodiment, the direction of the transmission axis is the longitudinal direction of the liquid crystal panel (the longitudinal direction of the linear light source unit: the direction of the arrow 24 in FIG. 19A). In the liquid crystal panel 90 of the form, the angle between the direction of the transmission axis and the longitudinal direction of the liquid crystal panel (longitudinal direction of the linear light source unit 50) is approximately 45 degrees (the direction of the arrow 92 in FIG. 19A). It is arranged to become. In general, since a liquid crystal panel has a viewing angle dependency, the transmission axis directions of a pair of polarizers are orthogonal to each other (crossed Nicols), and each of them forms an angle of 45 degrees with respect to the longitudinal direction of the liquid crystal panel. Is provided.

  When such a liquid crystal panel 90 is used, it is conceivable that the linearly polarized light passing through the polarization separation sheet 20 is arranged such that the polarization direction is the direction of the arrow 22 as shown in FIG. However, no matter what angle the polarization direction of the linearly polarized light enters the light guide plate 80, as the linearly polarized light propagates through the light guide plate 80, as shown in FIG. The polarization direction of the linearly polarized light emitted from the liquid crystal panel 90 is a direction (arrow 24) parallel to the longitudinal direction of the liquid crystal panel 90 (light source 50). If it does so, a shift | offset | difference will arise between the transmission axis directions (arrow 92) of the polarizer of the incident side of the liquid crystal panel 90. FIG.

  For this reason, in the liquid crystal display device 200 of this Embodiment, the half-wave sheet 100 is arrange | positioned. Further, in the half-wave sheet 100, the direction of the optical axis of the half-wave sheet 100 (arrow 102) is the polarization direction of linearly polarized light emitted from the light guide plate 80, as shown in FIG. (Arrow 24) and the direction of the transmission axis of the polarizer on the incident side of the liquid crystal panel 90 (arrow 92). By arranging in this way, the polarization direction of the linearly polarized light emitted from the light guide plate 80 is rotated and becomes the same direction as the transmission axis direction of the polarizer on the incident side of the liquid crystal panel 90, and the liquid crystal panel 90 (incident Is incident on the side polarizer). Therefore, the linearly polarized light emitted from the light guide plate 80 is incident on the liquid crystal panel without waste.

  Thus, in this embodiment, the polarization direction of linearly polarized light emitted from the illumination device (light guide plate) is rotated by the phase modulation element such as a half-wave sheet, and the polarizer on the incident side of the liquid crystal panel Accordingly, the absorption loss in the polarizer can be reduced, and the light from the illumination device can be used efficiently without waste, so that a bright liquid crystal display device can be realized.

  Also in this embodiment, as the lighting device, it is possible to use the lighting device shown in the above embodiment applied to a backlight type lighting device, and as a transmissive liquid crystal panel, The transmission mode liquid crystal panel in various modes can be used as in the above-described embodiment.

  FIG. 11 is a diagram showing a lighting apparatus 130 according to the tenth embodiment of the present invention. The configuration is similar to that of the illumination device 120 of the second embodiment described above. The difference is that the configuration of the light source unit 50 is partially different, and the half-wave sheet 60 is used instead of the polarization separation sheet 20. It is a point that is arranged. That is, as shown in FIG. 15, the light source unit 50 has a configuration in which the reflecting layer as in the second embodiment is not provided on the prism surface 53 of the columnar light guide 52.

  Therefore, as for the light incident on the columnar light guide 52 from the point light-emitting portion 51, only the light incident on the prism surface 53 under the total reflection condition is emitted from the emission surface 54 as shown in FIG. As shown in FIG. 15 (b), light that enters the prism surface 53 without satisfying the total reflection condition, passes through, and exits from the columnar light guide 52, or FIG. 15 (c). As shown, light that is once emitted from the prism surface 53, enters the columnar light guide 52 again from the other prism surface 53, propagates through the columnar light guide 52, and escapes to the opposite side. The light that is emitted from the emission surface 54 and is not directed to the half-wave sheet 60 is invalidated.

  When light is totally reflected, the S-polarized component may increase under a specific angle condition. Therefore, in the case of the configuration as in the present embodiment, by setting the angle of the prism surface 53 to a specific angle condition, the light in the columnar light guide 52 is reflected while light is repeatedly incident and reflected on the prism surface 53. The light has a large S-polarized component. Therefore, the light emitted from the columnar light guide 52 can be linearly polarized light without using a polarization separation element. (Note that the flat light guide plate 30 and the like shown in the above-described embodiment are configured under the condition that the S polarization component and the P polarization component are totally reflected to the same extent). In order to make light into linearly polarized light in a predetermined direction, only the half-wave sheet 60 is required. The linearly polarized light rotated in the desired polarization direction by the half-wave sheet 60 enters the light guide plate 30 and exits from the light guide plate 30 while maintaining its polarization state.

  Therefore, when the illumination device 130 according to the present embodiment is used as the illumination device of the liquid crystal display device 200 according to the ninth embodiment, the half-wave sheet 60 of the illumination device 130 is reduced to 2 of the liquid crystal display device 200. Since the half-wave sheet 100 can also function, the half-wave sheet 100 can be omitted. Therefore, when the lighting device 130 of this embodiment is used, a bright liquid crystal display device can be realized with a smaller number of components.

  FIG. 20 is a diagram illustrating a configuration example of each optical element of the polarization separation sheet 20, the quarter-wave sheet 40, and the half-wave sheet 100 used in the above-described embodiment. FIG. 20A shows a surface uneven type element, and an element having a function similar to that of a wavelength sheet can be manufactured by reducing the uneven modulation period. FIG. 20B shows a so-called volume element in which the refractive index in the medium changes periodically, and functions similar to the wavelength sheet by making the modulation period of the refractive index inside the medium fine. In addition, as shown in FIG. 20B, an element having a function similar to that of the polarization separation sheet can be manufactured by providing a period of refractive index substantially parallel to the substrate surface as shown in FIG.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made.

2, 10, 50: light source unit 4: phase modulation element 6: polarization separation element 20: polarization separation sheet 30, 80: light guide plate 40: quarter-wave sheet 60: half-wave sheet 70: reflective liquid crystal Panel 90: Transmission type liquid crystal panel 100: Half-wave sheet

Claims (12)

  A flat light guide plate, a light source disposed on a side of the light guide plate, and disposed between the light guide plate and the light source, transmits linearly polarized light in a first polarization direction, and transmits the first light An illuminating device comprising: a polarization separation element that reflects linearly polarized light in a polarization direction orthogonal to the polarization direction.   The illumination device according to claim 1, further comprising a phase modulation element between the light source unit and the polarization separation element.   The lighting device according to claim 1, wherein the light source unit includes a light emitting source and a reflecting member that reflects light from the light emitting source.   The lighting device according to claim 3, wherein the light source is a linear light source, and the reflection member is disposed so as to surround the linear light source.   The light source unit includes a columnar light guide, the light source is a point light source, the point light source is disposed on an end surface of the column light guide, and the columnar light guide. The lighting device according to claim 3, wherein light is emitted from the first side surface of the first light source, and the reflection member is provided on a second side surface opposite to the first side surface.   The lighting device according to claim 5, wherein the second side surface is a prism surface.   An illuminating device comprising: a flat light guide plate; a light source unit disposed on a side of the light guide plate; and a phase modulation element disposed between the light guide plate and the light source unit.   The light source unit includes a point-like light source and a columnar light guide, the point-like light source is disposed on an end surface of the columnar light guide, and the first light source of the columnar light guide The illumination device according to claim 7, wherein light is emitted from a side surface.   The lighting device according to claim 8, wherein the second side surface facing the first side surface is a prism surface.   A liquid crystal panel, a flat light guide plate, a light source unit disposed on a side of the light guide plate, and disposed between the light guide plate and the light source unit, and transmits linearly polarized light in a first polarization direction, A liquid crystal display device comprising: an illumination device having a polarization separation element that reflects linearly polarized light in a polarization direction orthogonal to the first polarization direction.   The liquid crystal display device according to claim 10, further comprising a first phase modulation element between the light source unit and the polarization separation element.   The liquid crystal display device according to claim 10, further comprising a second phase modulation element between the liquid crystal panel and the illumination device.

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