JP5002854B2 - Backlight system for liquid crystal display - Google Patents

Description

  The present invention relates to a backlight system for a liquid crystal display device, and more particularly to a backlight system for a liquid crystal display device capable of controlling a viewing angle of the liquid crystal display device.

  Recently, mobile phones have become very popular, and the penetration rate in Japan is said to be over 75%. In addition to the telephone call function, the mobile phone has an e-mail transmission / reception function, an image shooting display function, a game function, and the like. A liquid crystal display device that displays characters, images, and videos is indispensable for creating and viewing e-mails using these functions, taking and displaying images, playing games, and the like. Mobile phones have been used in every scene of daily life, and in order to create an e-mail to be sent, a user sees a liquid crystal display device alone, and images displayed on the liquid crystal display device can be viewed by multiple people. There are scenes to watch at the same time. In addition, there are scenes where users can browse the contents and images of e-mails without worrying about people's eyes, and scenes where users can view the contents and images of e-mails that they do not want to be seen by people while watching them in the crowd. is there.

  Therefore, the viewing angle of the liquid crystal display device can be changed according to the usage situation of the mobile phone, and the viewing angle is limited only in the front direction of the liquid crystal display device, so that a person other than the user can see the display of the liquid crystal display device from the side. It is desirable that it is possible to prevent a person other than the user from seeing the display of the liquid crystal display device from the side by including a wider range including the front direction in the viewing angle.

As a liquid crystal display device capable of controlling the viewing angle, a liquid crystal display device described in Patent Document 1 has been invented. The liquid crystal display device described in Patent Document 1 is a liquid crystal display device using a transmissive liquid crystal that uses a so-called backlight, which is used in a mobile phone. As shown in FIG. 12, the liquid crystal display device includes an electric field control panel 200 including a liquid crystal element between the liquid crystal display panel 100 and the backlight unit 300. In this liquid crystal display device, the electric field control panel 200 emits light without being refracted by controlling the electric field to change the orientation of the liquid crystal contained in the electric field control panel 200. Or refracted and emitted. When the light emitted from the backlight unit 300 is emitted without being refracted, the viewing angle of the liquid crystal display device is a narrow range in the front direction. When the light is refracted and emitted, the viewing angle is the front. Wide range including direction.
JP 2006-119291 A

  In the liquid crystal display device configured as described in Patent Document 1, the electric field control panel 200 that switches the presence / absence of light refraction is provided between the liquid crystal display panel 100 and the backlight unit 300. The area of the emission surface needs to be approximately the same size as the liquid crystal display panel 100. Due to the electric field control panel 200, there are problems that the liquid crystal display device is thick and heavy, and that the cost is high. In addition, there is a problem that it is impossible to continuously change the viewing angle.

  The present invention has been made in view of the above problems, and provides a backlight system for a liquid crystal display device that can realize a liquid crystal display device that is light, thin, and capable of controlling the viewing angle at low cost. For the purpose.

In order to achieve the above object, a backlight system for a liquid crystal display device according to claim 1, a light source, a light guide that propagates light emitted from the light source, and the inside of the light guide are propagated. A light extraction member that irradiates light to the outside of the light guide, and a light incident member that is provided between the light source and the light guide and that emits light incident from the light source on the light guide. Electro-optical means for controlling the distribution of the propagation angle of the light inside the light guide by controlling the light, and the electro-optical means includes light in the liquid crystal layer. It is a polymer-dispersed liquid crystal element utilizing the scattering phenomenon of .

  According to this configuration, light is emitted from the light source, light emitted from the light source is propagated by the light guide, and light from the light source propagating inside the light guide is emitted to the outside by the light extraction member. Then, the distribution of the incident angle of the light emitted from the light source to the light guide is electrically controlled by the electro-optical means provided between the light source and the light guide, and the light guide from the light source The distribution of the propagation angle inside is controlled.

  Thus, since the distribution of the propagation angle inside the light guide is controlled by the electro-optical means, the angle distribution of the light irradiated to the outside of the light guide can be controlled by the light extraction member. Can control the viewing angle of the liquid crystal display device. In addition, since the electro-optical means is provided between the light source and the light guide, the electro-optical means only needs to have a size that expands only the range of light that is irradiated from the light source and incident on the light guide. As described above, since the electro-optical means is smaller than a light guide or the like, it is possible to realize a liquid crystal display device that is thin, light and inexpensive and capable of controlling the viewing angle. Further, it is possible to perform control for continuously changing the angular distribution of the output light of the backlight system by changing the driving condition of the electro-optical means.

Further, according to this configuration, as the electro-optical means, using existing technology called polymer-dispersed liquid crystal device utilizing scattering phenomenon of light in the liquid crystal layer, low cost backlight system for a liquid crystal display device can do.

The backlight system for a liquid crystal display device according to claim 2 , wherein a light source, a light guide that propagates light emitted from the light source, and light that propagates inside the light guide are external to the light guide. The light extraction member that irradiates the light, and is provided between the light source and the light guide, and electrically controls the distribution of the incident angle of the light emitted from the light source to the light guide. A backlight system for a liquid crystal display device comprising: an electro-optic means for controlling a distribution of propagation angles inside the light guide, wherein the electro-optic means uses a liquid crystal phase utilizing a light diffraction phenomenon in a liquid crystal layer. It is a diffractive element.

According to this configuration, as the electro-optical means, with existing technology referred to as a liquid crystal phase diffraction element using a diffraction phenomenon of light at the liquid crystal layer, it is possible to inexpensively realize a backlight system for a liquid crystal display device .

The backlight system for a liquid crystal display device according to claim 3 , wherein a light source, a light guide that propagates light emitted from the light source, and light that propagates inside the light guide are external to the light guide. The light extraction member that irradiates the light, and is provided between the light source and the light guide, and electrically controls the distribution of the incident angle of the light emitted from the light source to the light guide. A backlight system for a liquid crystal display device, comprising: an electro-optic means for controlling a distribution of propagation angles inside the light guide of the liquid crystal, wherein the electro-optic means uses a light refraction phenomenon in a liquid crystal layer. It is an element.

According to this configuration, as the electro-optical means, with existing technology referred to as a liquid crystal refractive element utilizing refraction phenomenon of light at the liquid crystal layer, it is possible to inexpensively realize a backlight system for a liquid crystal display device.

The backlight system for a liquid crystal display device according to claim 4 is the backlight system for a liquid crystal display device according to any one of claims 1 to 3 , wherein the light source emitted from the light source and the electro-optical means. And a directivity imparting member that imparts directivity in the light guide direction of the light guide to the light.

  According to this configuration, the light emitted from the light source is given the directivity in the light guide direction of the light guide by the directivity imparting member and is incident on the electro-optical means. Increase the difference between the distribution of the incident angle of light on the light guide when scattered, diffracted, or refracted and the distribution of the incident angle of light on the light guide when not scattered, diffracted, or refracted can do. Therefore, the change in the viewing angle of the liquid crystal display device can be made remarkable.

According to the backlight system for a liquid crystal display device according to any one of claims 1 to 3 , since the distribution of the propagation angle inside the light guide is controlled by the electro-optical means, the light extraction member irradiates the outside of the light guide. The angle distribution of the emitted light can be controlled, so that the viewing angle of the liquid crystal display device can be controlled. In addition, since the electro-optical means is provided between the light source and the light guide, the electro-optical means only needs to have a size that expands only the range of light that is irradiated from the light source and incident on the light guide. As described above, since the electro-optical means is smaller than the light guide or the like, there is an effect that it is possible to realize a liquid crystal display device which is thin, light and inexpensive and capable of controlling the viewing angle. In addition, by changing the driving condition of the electro-optical means, it is possible to perform the control of continuously changing the angular distribution of the output light of the backlight system.

In addition, according to the backlight system for a liquid crystal display device according to claim 1 , the electro-optical means is inexpensive by using an existing technology called a polymer dispersion type liquid crystal element that utilizes a light scattering phenomenon in a liquid crystal layer. there is an advantage that it is possible to realize a backlight system for a liquid crystal display device.

According to the backlight system for a liquid crystal display device according to claim 2, as an electro-optical means, with existing technology referred to as a liquid crystal phase diffraction element using a diffraction phenomenon of light at the liquid crystal layer, low cost liquid crystal display The effect that the backlight system for apparatuses can be realized is obtained.

According to the backlight system for a liquid crystal display device according to claim 3, as an electro-optical means, with existing technology referred to as a liquid crystal refractive element utilizing refraction phenomenon of light at the liquid crystal layer, low cost liquid crystal display device The effect that a backlight system for a vehicle can be realized is obtained.

According to the backlight system for a liquid crystal display device according to claim 4 , the light emitted from the light source is given directivity in the light guide direction of the light guide by the directivity imparting member and is incident on the electro-optical means. Therefore, when the light from the light source is scattered, diffracted or refracted by the electro-optical means, the distribution of the incident angle of the light to the light guide and the light guide when the light is not scattered, diffracted or refracted It is possible to increase the difference from the distribution of the incident angle to. Therefore, the effect that the change in the viewing angle of the liquid crystal display device can be made remarkable is obtained.

  Hereinafter, an example of an embodiment of a backlight system for a liquid crystal display device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an overall configuration of a backlight system 1 for a liquid crystal display device according to the present invention. As shown in FIG. 1, the backlight system 1 for a liquid crystal display device is used as a backlight of a transmissive liquid crystal display panel 60. In FIG. 1, for convenience of explanation, the interval between the backlight system 1 for the liquid crystal display device and the liquid crystal display panel 60 is shown larger than the actual distance. Also in the following drawings, the relationship between the sizes of the members shown is for convenience of explanation, and does not faithfully indicate the relationship between the actual sizes. A backlight system 1 for a liquid crystal display device includes a light source unit 2, a light guide 3 that propagates while irradiating light emitted from the light source unit 2, and light that propagates inside the light guide 3. A light extraction member 4 for irradiating the outside of the body 3 is provided. For example, the light extraction member 4 reflects light propagating in the light guide 3 and emits the light to the outside of the light guide 3 at an angle corresponding to the propagation angle of the light. 2 is a schematic diagram showing a cross section in the horizontal direction in FIG. 1 of the backlight system 1 for the liquid crystal display device, and FIG. 3 is surrounded by a broken-line circle A in FIG. 1 of the backlight system 1 for the liquid crystal display device. FIG. As shown in FIGS. 2 and 3, the light extraction member 4 includes an air layer 4a and a light guide 4b having a cylindrical protrusion structure.

  As shown in FIG. 2, the light source unit 2 includes a light source 5 composed of an LED (Light Emitting Diode), and a light guide direction of the light guide 3 to light emitted from the light source 5, that is, horizontal directivity in FIG. 2. By directly controlling the distribution of the incident angle of the light emitted from the light source 5 to the light guide 3 provided between the light source 5 and the light guide 3. Electro-optical means 7 for controlling the distribution of the propagation angle of light from the light source 5 inside the light guide 3 is provided.

  The directivity imparting member 6 has a bowl-shaped curved surface 6a formed on one surface of a cube. The curved surface 6a is formed of a material that reflects light, or is covered with a thin film made of a material that reflects light. The light source 5 is disposed so that the light emitting surface of the LED faces the curved surface 6a of the directivity imparting member 6 and the light emitting surface of the LED is located at the focal point of the curved surface 6a. The light from the light source (LED) 5 is reflected by the curved surface 6a and travels uniformly in the direction parallel to the axis passing through the focal point of the curved surface 6a, that is, the horizontal direction in FIG. The above description is simplified, and actually light travels in the horizontal direction with a certain angular distribution.

The electro-optical means 7 is realized using a liquid crystal element including a liquid crystal layer 10 sandwiched between a transparent substrate 8 and a transparent substrate 9. The liquid crystal element is arranged so that the liquid crystal layer 10 intersects the optical path of the light from the light source 5 reflected by the curved surface 6a of the directivity imparting member 6 perpendicularly. As can be seen from FIG. 2, the electro-optical means 7 is provided between the light source 5 and the light guide 3. Accordingly, the electro-optical means 7 only needs to have a size that expands only in the range of light that is irradiated from the light source 5 and incident on the light guide 3. As the liquid crystal element, for example, a polymer dispersed liquid crystal element (PDLC: Polymer Dispersed Liquid Crystal or PNLC: Polymer-Network Liquid Crystal) using a light scattering phenomenon in the liquid crystal layer 10 can be used. 4A and 4B are schematic views showing the liquid crystal layer 10 of the polymer dispersion type liquid crystal element. As shown in FIG. 4A, the liquid crystal layer 10 of the polymer dispersion type liquid crystal element has a configuration in which the liquid crystal 14 is dispersed in the polymer 13 sandwiched between the transparent electrode 11 and the transparent electrode 12. ing. In FIGS. 4A and 4B, liquid crystal molecules are schematically represented by ellipsoids, as is generally done in the description of liquid crystal operation. The liquid crystal molecules as is known there is anisotropy of refractive index, the refractive index n _e for extraordinary light of the ellipse long axis represents the refractive index n ₀ at the minor axis of the ellipse with respect to ordinary light (less It is the same in the drawings.)

  In a state where no voltage is applied between the transparent electrode 11 and the transparent electrode 12, the liquid crystal molecules in the liquid crystal 14 are oriented in an arbitrary direction as shown in FIG. Therefore, the light irradiated from the light source 5 and given directivity is scattered in an arbitrary direction by the liquid crystal molecules in the liquid crystal 14 of the liquid crystal layer 10. Therefore, the light scattered and emitted from the liquid crystal layer 10 enters the light guide 3 in a wide incident angle range.

  On the other hand, when a voltage is applied between the transparent electrode 11 and the transparent electrode 12, the liquid crystal molecules in the liquid crystal are arranged such that the long axis of the ellipsoid is parallel to the direction of the electric field, as shown in FIG. Oriented. Therefore, the light irradiated from the light source 5 and given directivity travels straight without being scattered by the liquid crystal molecules in the liquid crystal 14 of the liquid crystal layer 10. Therefore, the light emitted from the liquid crystal layer 10 enters the light guide 3 in a narrow incident angle range.

  The effect of such a polymer dispersion type liquid crystal element is confirmed by the following experiment. 5 and 6 are schematic views showing the experimental method. In this experiment, as shown in FIG. 5, a polymer-dispersed liquid crystal element as the electro-optical means 7 is arranged on a turntable 50 whose rotation is controlled by a personal computer (not shown). As shown in FIG. 6, an LED as the light source 5 is disposed on the back surface of the polymer dispersed liquid crystal element (electro-optical means 7), and the light source 5 is interposed between the polymer dispersed liquid crystal element and the light source 5. An optical film 15 is provided for giving directivity to the light emitted from the light source. A table stand 51 is arranged at a predetermined distance from the turntable 50, and a photodiode 52 as a sensor for measuring light emitted from the polymer dispersion type liquid crystal element is disposed on the upper surface of the table stand 51. Is installed. The output of the photo diode 52 is input to a personal computer (not shown). The polymer dispersed liquid crystal element emits light emitted from the light source 5 through the liquid crystal layer 10, and the photodiode 52 senses the light emitted from the polymer dispersed liquid crystal element. The amount of light sensed by the photodiode 52 is calculated by the personal computer for each rotation angle of the polymer dispersed liquid crystal element.

  FIG. 7 is a graph showing the relationship between the rotation angle of the polymer dispersed liquid crystal element and the output of the photodiode 52 as a result of the above experiment. In this graph, the angle at which the polymer-dispersed liquid crystal element faces the front of the photodiode 52 is “0” degrees. Further, a graph when no voltage is applied to the polymer dispersed liquid crystal element (voltage off) is indicated by a dotted line, and a graph when a voltage is applied (voltage on) is indicated by a solid line. As can be seen from FIG. 7, when the voltage is not applied (voltage off), the rotation angle of the polymer-dispersed liquid crystal element is 30 to 60 degrees, compared to when the voltage is applied (voltage on), and The output of the photodiode 52 increases from -30 degrees to -60 degrees. Therefore, when no voltage is applied to the polymer dispersed liquid crystal element, the liquid crystal layer 10 scatters light from the light source by liquid crystal molecules, and when a voltage is applied, the liquid crystal layer 10 transmits the light from the light source without scattering. I understand that.

  According to such a polymer-dispersed liquid crystal element, the emission angle distribution of light from the light source 5 emitted from the polymer-dispersed liquid crystal element is continuously adjusted by adjusting the voltage to be applied on or off. Can be changed. Further, although not shown here, when the applied voltage is changed, the angular distribution of the output light intensity continuously changes. Therefore, if this polymer dispersion type liquid crystal element is used as the electro-optical means 7, the distribution of the incident angle of the light irradiated from the light source 5 to the light guide 3 is electrically controlled, and the light guide 3 It is possible to control the distribution of the light propagation angle inside.

  When the voltage applied to the polymer dispersed liquid crystal element is turned on and the incident angle distribution of the light incident on the light guide 3 is limited to a narrow range, the propagation angle inside the light guide 3 is also limited. The emission angle of light extracted by the extraction member 4 is also limited to an angle near the front of the liquid crystal display panel 100. Therefore, the viewing angle of the liquid crystal display device can be narrowed. On the other hand, when the voltage applied to the polymer dispersed liquid crystal element is turned off and the incident angle distribution of the light incident on the light guide 3 is widened, the propagation angle of the light propagating through the light guide 3 is increased. Therefore, the emission angle of the light extracted by the light extraction member 4 also has a width. Therefore, the viewing angle of the liquid crystal display device can be widened.

  The polymer-dispersed liquid crystal element is not limited to the above-described configuration, and the light applied from the light source 5 can be scattered by or not scattering light in the liquid crystal layer 10 by adjusting the applied voltage. Any configuration that can control the distribution of the incident angles on the light guide 3 may be used.

  As the electro-optical means 7 for controlling the incident angle distribution of light to the light guide 3, in addition to the polymer dispersed liquid crystal element described above, a liquid crystal phase diffractive element using a light diffraction phenomenon in the liquid crystal layer 10 ( LCPG (Liquid Crystal Phase Grating) can be used. This liquid crystal phase diffraction element forms a diffraction grating by liquid crystal molecules by applying a voltage to the liquid crystal layer 10, and diffracts and emits light incident on the liquid crystal layer 10 by this diffraction grating.

  8A and 8B are schematic views showing the liquid crystal layer 10 of the liquid crystal phase diffraction element. As shown in FIGS. 8A and 8B, the liquid crystal layer 10 includes an alignment film 16, an alignment film 17, a liquid crystal 18 held between the alignment film 16 and the alignment film 17, and the liquid crystal layer 10. A transparent electrode 19 and a transparent electrode 20 are provided periodically on one alignment film side (for example, the alignment film 16 side that emits light). As shown in FIG. 8A, the alignment film 16 and the alignment film 17 are arranged such that when no voltage is applied between the transparent electrode 19 and the transparent electrode 20, the liquid crystal molecules are aligned with their major axes. The material is selected so as to be aligned in a direction perpendicular to the film 16 and the alignment film 17. Therefore, when no voltage is applied between the transparent electrode 19 and the transparent electrode 20, the light irradiated from the light source 5 and given directivity travels straight through the liquid crystal 18 of the liquid crystal layer 10 and is guided. Incident on the light body 3.

  On the other hand, when a voltage is applied between the transparent electrode 19 and the transparent electrode 20, the liquid crystal molecules existing between the transparent electrode 19 and the transparent electrode 20 are applied to the electric field as shown in FIG. Orient along. FIG. 9 is a schematic diagram illustrating a configuration example of the transparent electrode 19 and the transparent electrode 20. As shown in FIG. 9, the transparent electrode 19 and the transparent electrode 20 are each formed in a comb shape, and are arranged so that the tooth portions of the comb are periodically positioned at a predetermined interval. Therefore, as shown in FIG. 8B, liquid crystal molecules aligned along the electric field generated between the transparent electrode 19 and the transparent electrode 20 also exist periodically. As a result, the liquid crystal molecules aligned along the electric field and the liquid crystal molecules aligned perpendicular to the transparent electrode 19 and the transparent electrode 20 form a diffraction grating. Therefore, when a voltage is applied between the transparent electrode 19 and the transparent electrode 20, the light irradiated from the light source 5 and given directivity is applied to the alignment film 16 and the alignment film 17 in the liquid crystal layer 10. On the other hand, it is diffracted by the diffraction grating formed by the liquid crystal molecules aligned vertically and the liquid crystal molecules aligned along the electric field, and is emitted with various diffraction angles in the direction in which the transparent electrode 19 and the transparent electrode 20 are periodically arranged. , Enters the light guide 3.

  The effect of such a liquid crystal phase diffraction element is confirmed by an experiment similar to the experiment described above. In the experiment described above with reference to FIGS. 5 and 6, a liquid crystal phase diffraction element is used as the electro-optical means 7. The other points are the same as the previous experiment. In the liquid crystal phase diffraction element, the direction of the periodic structure formed by the liquid crystal molecules aligned perpendicular to the alignment film 16 and the alignment film 17 and the liquid crystal molecules aligned along the electric field is relative to the table of the turntable 50. The transparent electrode 19 and the transparent electrode 20 shown in FIG. 9 are arranged on the turntable 50 in the horizontal direction, that is, the direction rotated in the horizontal direction by 90 degrees in FIG. FIG. 10 is a graph showing the relationship between the rotation angle of the liquid crystal phase diffraction element and the output of the photodiode 52 obtained as a result of this experiment. In this graph, a graph when a voltage is not applied to the liquid crystal phase diffraction element (voltage off) is indicated by a dotted line, and a graph when a voltage is applied (voltage on) is indicated by a solid line. As can be seen from FIG. 10, when the voltage is applied (voltage on), the rotation angle of the liquid crystal phase diffractive element is 30 to 60 degrees, compared to when the voltage is not applied (voltage off), and − The output of the photodiode 52 increases from 30 degrees to -60 degrees. Therefore, when no voltage is applied to the liquid crystal phase diffractive element, the liquid crystal layer 10 transmits the light from the light source without diffracting it, and when a voltage is applied, the liquid crystal layer 10 diffracts the light from the light source formed by liquid crystal molecules. It can be seen that it is diffracted by the grating.

  According to such a liquid crystal phase diffractive element, the emission angle distribution of light from the light source 5 emitted from the liquid crystal phase diffractive element can be continuously changed by adjusting the applied voltage to be on or off. Can do. Therefore, if this liquid crystal phase diffractive element is used as the electro-optical means 7, the distribution of the incident angle of the light emitted from the light source 5 to the light guide 3 is electrically controlled, so that the inside of the light guide 3 is controlled. The distribution of the propagation angle of light can be controlled.

  The liquid crystal phase diffractive element is not limited to the above-described configuration, and the light guided from the light source 5 can be guided by diffracting or not diffracting light in the liquid crystal layer 10 by adjusting the applied voltage. Any configuration that can control the distribution of the incident angles on the body 3 may be used.

  Further, as the electro-optical means 7 for controlling the incident angle distribution of light to the light guide 3, a liquid crystal refraction element using a light refraction phenomenon in the liquid crystal layer 10 can be used. In this liquid crystal refractive element, for example, a polymer member formed of a polymer material is encapsulated in the liquid crystal layer 10, and the refractive index of the polymer member and the refractive index of the liquid crystal when voltage is applied. The light incident on the liquid crystal layer 10 is refracted or emitted without being refracted using the difference between the refractive index of the liquid crystal when no voltage is applied.

11A and 11B are schematic views showing the liquid crystal layer 10 of the liquid crystal refractive element. As shown in FIGS. 11A and 11B, the liquid crystal layer 10 is disposed outside the alignment film 21, the alignment film 22, the liquid crystal 23 held between the alignment film 21 and the alignment film 22, and the alignment film 21. A transparent electrode 24 arranged, a transparent electrode 25 arranged outside the alignment film 22, and a cylindrical shape provided on one alignment film side of the liquid crystal layer 10 (for example, the alignment film 21 side emitting light). A lens-shaped polymer member 26 is provided. As shown in FIG. 11A, the alignment film 21 and the alignment film 22 have liquid crystal molecules aligned in the major axis when no voltage is applied between the transparent electrode 24 and the transparent electrode 25. The material is selected so as to be aligned in a direction parallel to the film 21 and the alignment film 22. Refractive index of the polymer member 26 is _{n e.} Here, of the light given irradiated directional light source 5, the liquid crystal layer 10 without being refracted because the vertical polarization component oscillating in the direction feel uniform refractive index n _e of FIG. 11 (a) Transparent. However, the polarization component oscillating in the direction perpendicular to the paper surface in FIG. 11 (a) is refracted at the boundary of the polymer member 26 having a refractive index n _e of the liquid crystal 23 of refractive index n _0. Therefore, when no voltage is applied between the transparent electrode 24 and the transparent electrode 25, one polarized component of the light irradiated from the light source 5 and given directivity travels straight in the liquid crystal layer 10. The other polarization component is refracted. Then, the light emitted from the liquid crystal layer 10 enters the light guide 3.

On the other hand, when a voltage is applied between the transparent electrode 24 and the transparent electrode 25, the liquid crystal molecules are aligned so that the major axis direction is parallel to the electric field direction, as shown in FIG. . At this time, the refractive index of the liquid crystal 23 where the light of the polarization components in both directions given the irradiated directional light source 5 feel is n _0. Refractive index of the polymer member 26 is _{n e,} the relation between the refractive index _{n e} and the refractive index _{n 0,} a n e> _{n 0.} Therefore, when a voltage is applied between the transparent electrode 24 and the transparent electrode 25, the polarization components in both directions in the light irradiated from the light source 5 and given directivity and incident on the liquid crystal layer 10 are: When entering the polymer member 26 from the liquid crystal 23, the liquid crystal layer 10 is bent and refracted from the liquid crystal layer 10 because it bends toward the polymer member 26 having a higher refractive index. Then, the light emitted from the liquid crystal layer 10 enters the light guide 3.

  According to such a liquid crystal refracting element, the emission angle distribution of light from the light source 5 emitted from the liquid crystal refracting element can be continuously changed by adjusting the voltage to be applied on or off. . Therefore, if this liquid crystal refracting element is used as the electro-optical means 7, the distribution of the incident angle of the light irradiated from the light source 5 to the light guide 3 is electrically controlled, so that the light inside the light guide 3 can be controlled. It is possible to control the distribution of the propagation angle.

  The liquid crystal refracting element is not limited to the above-described configuration, and a light guide body for light emitted from the light source 5 by refracting or not refracting light in the liquid crystal layer 10 by adjusting an applied voltage. Any configuration can be used as long as the distribution of the incident angles on the light source 3 can be controlled. Therefore, the alignment of the liquid crystal in the liquid crystal layer 10 is not limited to the alignment shown in FIGS. 11A and 11B, and may be a hybrid alignment in which homogeneous alignment and vertical alignment coexist.

  In the above-described example, as shown in FIGS. 11A and 11B, the polymer member 26 encapsulated in the liquid crystal layer 10 of the liquid crystal refractive element has a cylindrical lens shape. The shape of the member 26 is not limited to a cylindrical lens shape, and functions to refract or not refract the light transmitted through the liquid crystal of the liquid crystal layer 10 when a voltage is applied to the liquid crystal layer 10 or not. Any shape can be used.

  As described above, according to the backlight system 1 for a liquid crystal display device according to the present invention, the polymer-dispersed liquid crystal element using the light scattering phenomenon in the liquid crystal layer, and the light diffraction phenomenon in the liquid crystal layer. An electro-optical means 7, which is either a liquid crystal phase diffraction element used or a liquid crystal refraction element using a light refraction phenomenon in a liquid crystal layer, is disposed between the light source 5 and the light guide 3. Then, the electro-optical means 7 scatters, diffracts, or refracts the light emitted from the light source 5 or does not scatter, diffract, and refract the light to the light guide 3 of the light emitted from the light source. The distribution of the incident angle of the light is electrically controlled, and the distribution of the propagation angle of the light within the light guide 3 is controlled. As a result, the angular distribution of the light that is extracted from the light guide 3 by the light extraction member 4 and irradiated to the outside is controlled, and the viewing angle of the liquid crystal display device is controlled.

  The electro-optical means 7 provided for controlling the viewing angle of the liquid crystal display device is disposed between the light source 5 and the light guide 3. For this reason, the electro-optical means 7 only needs to have a size that expands only in the range of light irradiated from the light source 5 and incident on the light guide 3, and the size is the conventional liquid crystal display shown in FIG. It is much smaller than the electric field control panel 200 used in the apparatus. Therefore, according to the backlight system 1 for a liquid crystal display device of the present invention, the liquid crystal display device capable of controlling the viewing angle can be made thin and light and can be realized at low cost.

  The embodiment of the present invention is not limited to the above-described embodiment, and can be implemented with various modifications within the scope of the technical idea of the present invention.

  The present invention is applicable to a backlight system for a liquid crystal display device that can control the viewing angle of the liquid crystal display device.

It is a schematic diagram which shows the whole structure of the backlight system 1 which concerns on this invention. It is a schematic diagram which shows the cross section of the paper surface horizontal direction in FIG. FIG. 2 is an enlarged view of a portion A in FIG. 1 of the backlight system 1. It is a schematic diagram which shows the liquid crystal layer 10 of a polymer dispersion type liquid crystal element. It is a schematic diagram which shows the method of the experiment of the effect of a polymer dispersion type liquid crystal element and a liquid crystal phase diffraction element. It is a schematic diagram which shows the method of the experiment of the effect of a polymer dispersion type liquid crystal element and a liquid crystal phase diffraction element. It is a graph which shows the result of the experiment about a polymer dispersion type liquid crystal element. It is a schematic diagram which shows the liquid crystal layer 10 of a liquid crystal phase diffraction element. It is a schematic diagram which shows the structure of the transparent electrode 19 and the transparent electrode 20 of a liquid crystal phase diffraction element. It is a graph which shows the result of the experiment about a liquid crystal phase diffraction element. It is a schematic diagram which shows the liquid crystal layer 10 of a liquid crystal refractive element. It is a schematic diagram which shows the structure of the conventional liquid crystal display device which can control a viewing angle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight system 5 Light source 6 Directionality provision member 7 Electro-optical means (polymer dispersion type liquid crystal element, liquid crystal phase diffraction element, liquid crystal refraction element)
10 Liquid crystal layer

Claims (4)

A light source;
A light guide that propagates light emitted from the light source;
A light extraction member for irradiating the outside of the light guide with light propagating inside the light guide;
Propagation of the light inside the light guide by electrically controlling the distribution of the incident angle of the light radiated from the light source to the light guide provided between the light source and the light guide A backlight system for a liquid crystal display device comprising electro-optic means for controlling the distribution of angles ,
The backlight system for a liquid crystal display device , wherein the electro-optical means is a polymer dispersion type liquid crystal element utilizing a light scattering phenomenon in a liquid crystal layer . A light source;
A light guide that propagates light emitted from the light source;
A light extraction member for irradiating the outside of the light guide with light propagating inside the light guide;
Propagation of the light inside the light guide by electrically controlling the distribution of the incident angle of the light radiated from the light source to the light guide provided between the light source and the light guide A backlight system for a liquid crystal display device comprising electro-optic means for controlling the distribution of angles,
The electro-optical device includes a backlight system for a liquid crystal display device you being a liquid crystal phase diffraction element utilizing a diffraction phenomenon of light at the liquid crystal layer. A light source;
A light guide that propagates light emitted from the light source;
A light extraction member for irradiating the outside of the light guide with light propagating inside the light guide;
Propagation of the light inside the light guide by electrically controlling the distribution of the incident angle of the light radiated from the light source to the light guide provided between the light source and the light guide A backlight system for a liquid crystal display device comprising electro-optic means for controlling the distribution of angles,
The electro-optical device includes a backlight system for a liquid crystal display device you being a liquid crystal refractive element utilizing refraction phenomenon of light at the liquid crystal layer. Provided on an optical path, further comprising a directional applying member to provide the directivity of the light guiding direction of the light guide to the light Rukoto between the light source and the electro-optical means of the light emitted from the light source The backlight system for a liquid crystal display device according to any one of claims 1 to 3 .

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