JP2007066556A - Surface light source and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a liquid crystal display element perform a narrow angle of field display and a wide angle of field display without using a liquid crystal element for angle of field restriction which is difficult to manufacture. <P>SOLUTION: A surface light source 8 is arranged which comprises, on the opposite side to the observation side of the liquid crystal display element 1, a light guide plate 9 in which a first incident end face 10a is formed on one of two end faces, a second incident end face 10b is formed on the other end face, an outgoing face 11 which emits the incident light from the first and the second end faces is formed on one of the two plate faces, and a reflecting face 12 having a mirror-face reflecting part 13a that mirror reflects the light incident from the first incident end face 10a toward the outgoing face 11 and a scattering reflecting part 13b that scattering reflects the light incident from the second incident end face 10b toward the outgoing face 11 is formed on the other plate face, a first light emitting element 14a which emits light toward the first incident end face 10a of the light guide plate 9, and a second light emitting element 14b which emits the light toward the second incident end face 10b of the light guide plate 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface light source and a liquid crystal display device capable of causing a liquid crystal display element to perform a narrow viewing angle display and a wide viewing angle display.

  The liquid crystal display device is composed of a plate-like transparent member on the side opposite to the observation side of the liquid crystal display element having a screen region in which a plurality of pixels for controlling the transmission of light are arranged in a matrix, and light is applied to at least one end face. Is formed on one of the two plate surfaces, and an exit surface for emitting the light incident from the entrance end surface is formed on one of the two plate surfaces. The light incident on the other plate surface from the incident end surface is directed toward the exit surface. The light source plate is formed by arranging a surface light source including a light guide plate having a reflective surface that reflects light and a light emitting element that is disposed to face the incident end surface of the light guide plate and emits light toward the incident end surface. (See Patent Document 1).

  By the way, since the liquid crystal display device is designed so as to obtain a wide viewing angle, the display is viewed by a third party from a direction inclined with respect to the front direction (direction near the normal line of the liquid crystal display element). There is a risk of being seen.

  Therefore, on one surface side of the liquid crystal display element, there is provided a viewing angle limiting liquid crystal element in which liquid crystal molecules are aligned in different alignment states for each of the divided regions divided into a plurality of regions corresponding to the screen of the liquid crystal display element. There has been proposed a liquid crystal display device capable of performing a wide viewing angle display and a high security narrow viewing angle display without fear of being peeped by a third party (see Patent Document 2).

  The viewing angle limiting liquid crystal element is a method of the liquid crystal display element for each divided region obtained by dividing liquid crystal molecules in a liquid crystal layer sealed between a pair of substrates into a plurality of regions corresponding to the screen of the liquid crystal display device. An alignment state having a viewing angle in a direction tilted in one direction with respect to the line direction and an alignment state having a viewing angle in a direction tilted in the opposite direction to the direction, and the pair of substrates are opposed to each other Each of the inner surfaces is provided with electrodes having a predetermined shape corresponding to the respective divided regions.

  This liquid crystal display device limits the viewing angle of the display image of the liquid crystal display element by reducing the visibility from an oblique direction by applying a voltage between the electrodes of the viewing angle limiting liquid crystal element, When no voltage is applied between the electrodes of the viewing angle limiting liquid crystal element, that is, when the viewing angle limiting liquid crystal element is in a non-display state, a display image of the liquid crystal display element can be seen with a wide viewing angle.

On the other hand, when a voltage is applied between the electrodes of the viewing angle limiting liquid crystal element, the liquid crystal display element is viewed from a direction inclined in one direction with respect to the front direction and a direction inclined in the opposite direction. Display image of each segmented region having a viewing angle in a direction tilted in one direction of the viewing angle limiting liquid crystal element, and the predetermined segmented region having a viewing angle in a direction tilted in the opposite direction Since it is hidden by the display corresponding to the shape electrode, the display image of the liquid crystal display element cannot be recognized from the one direction and the direction inclined in the opposite direction, and the viewing angle of the display image is apparently limited. As a result, the viewing angle of the display image is narrowed.
JP 2003-149599 A JP 2000-133334 A

  However, the viewing angle limiting liquid crystal element in which the liquid crystal molecules are aligned in different alignment states for each of the divided regions obtained by dividing the region corresponding to the screen of the liquid crystal display element into each of the inner surfaces of the pair of substrates. Manufacture is difficult because a complicated alignment process (rubbing process of the alignment film) in which the direction is different for each divided region must be performed.

  Therefore, the conventional liquid crystal display device that limits the viewing angle by the viewing angle limiting liquid crystal element has a problem of high cost.

  The present invention provides a surface light source capable of causing a liquid crystal display element to perform a narrow viewing angle display and a wide viewing angle display without using a difficult-to-manufacture viewing angle limiting liquid crystal element, and includes the surface light source. Another object of the present invention is to provide a variable viewing angle liquid crystal display device that can be obtained at low cost.

  The surface light source according to the present invention comprises a transparent plate-like member, a first incident end surface is formed on one of two end surfaces facing each other, and a second incident end surface is formed on the other end surface. An exit surface for emitting light incident from the first and second entrance end surfaces is formed on one of the surfaces, and the light incident from the first entrance end surface is specularly reflected on the other plate surface toward the exit surface. A light guide plate having a reflecting surface having a specular reflection portion and a scattering reflection portion that scatters and reflects light incident from the second incident end surface toward the output surface, and a first incident end surface of the light guide plate And a first light emitting element that emits light toward the first incident end face, and a second light emitting end face of the light guide plate, and is directed toward the second incident end face. And a second light emitting element that emits light.

  In this surface light source, the specular reflection part of the reflection surface of the light guide plate causes the light incident from the first incident end surface to be in a direction within a predetermined spread angle range centering on the normal direction of the light guide plate. It is preferable that the scattering reflection part of the reflection surface reflects the light incident from the second incident end face in a spreading direction larger than a spreading angle of the light reflected by the specular reflection part.

  Further, in this surface light source, a plurality of elongated grooves substantially parallel to the length direction of the first and second incident end faces are formed at a predetermined pitch over the entire reflection surface of the light guide plate. From the inclined surface inclined in the direction opposite to the first incident end surface toward the reflecting surface with respect to the normal direction of the light guide plate by the side surface of the elongated groove on the first incident end surface side. A specular reflection portion is formed, and the side surface of the plurality of elongated grooves on the second incident end face side is inclined in the direction opposite to the second incident end face toward the reflecting face with respect to the normal direction. It is desirable to form the scattering reflection part which consists of an uneven surface provided with minute unevenness on the surface.

  In that case, it is preferable that the scattering reflection portion is formed in a shape bent at at least one location along the depth direction of the elongated groove.

  Furthermore, it is more preferable that the scattering reflection portion is formed in a curved shape along the depth direction of the elongated groove.

The liquid crystal display device of the present invention is
A liquid crystal display element having a screen region in which a plurality of pixels for controlling light transmission are arranged in a matrix, and
The first incident end surface is formed on one of the two end surfaces facing each other, the second incident end surface is formed on the other end surface, and the first and second plate surfaces are formed on one of the two plate surfaces. An exit surface that emits light incident from the second entrance end surface is formed, and a mirror reflection portion that specularly reflects light incident from the first entrance end surface toward the exit surface on the other plate surface and the first surface A light guide plate formed with a reflection surface having a scattering reflection portion that scatters and reflects light incident from the two incident end surfaces toward the emission surface, and is disposed to face the first incident end surface of the light guide plate, A first light emitting element that emits light toward the first incident end face; and a second light emitting element that is disposed to face the second incident end face of the light guide plate and emits light toward the second incident end face. A light emitting element, and the light guide plate on a side opposite to the observation side of the liquid crystal display element And they arranged a surface light source so as to face the liquid crystal display device the emission surface,
The light source driving means for selectively lighting the first light emitting element and the second light emitting element of the surface light source is provided.

  In the surface light source of the present invention, a first incident end surface is formed on one of two end surfaces facing each other, a second incident end surface is formed on the other end surface, and the first and first surfaces are formed on one of two plate surfaces. A light-exiting surface for emitting light incident from the light-incident end surface, and a second reflecting surface for reflecting the light incident from the first light-incident end surface toward the light-exiting surface; A light guide plate having a reflection surface having a scattering reflection portion that scatters and reflects light incident from the incident end surface toward the emission surface, and is disposed to face the first incident end surface of the light guide plate, A first light emitting element that emits light toward the first incident end face, and a second light emitting element that is disposed to face the second incident end face of the light guide plate and emits light toward the second incident end face The first light emitting element and the second light emitting element are selected. The first light having a small divergence angle that is incident on the light guide plate from the first incident end surface and is reflected by the specular reflection portion of the reflection surface of the light guide plate, and the light guide plate on the light guide plate. The second light having a large spread angle incident from the second incident end face and reflected by the scattering reflection portion of the reflection surface of the light guide plate can be selectively emitted from the emission surface of the light guide plate, Therefore, by disposing the surface light source on the side opposite to the viewing side of the liquid crystal display element and the light emission surface of the light guide plate facing the liquid crystal display element, a liquid crystal element for limiting the viewing angle that is difficult to manufacture is not used. Further, the liquid crystal display element can perform narrow viewing angle display and wide viewing angle display.

  In this surface light source, the specular reflection portion of the reflection surface of the light guide plate causes the light incident from the first incident end surface to be in a direction within a predetermined spread angle range centering on the normal direction of the light guide plate. The scattering reflection part of the reflection surface preferably reflects the light incident from the second incident end face in a spreading direction larger than the spreading angle of the light reflected by the specular reflection part. By doing so, a narrow viewing angle display in which the front direction (the direction in the vicinity of the normal line of the liquid crystal display element) is the display viewing direction and display from an oblique direction with respect to the front direction are displayed on the liquid crystal display element. Can be displayed with a wide viewing angle.

  Further, in this surface light source, a plurality of elongated grooves substantially parallel to the length direction of the first and second incident end faces are formed at a predetermined pitch over the entire reflection surface of the light guide plate. From the inclined surface inclined in the direction opposite to the first incident end surface toward the reflecting surface with respect to the normal direction of the light guide plate by the side surface of the elongated groove on the first incident end surface side. A specular reflection portion is formed, and the side surface of the plurality of elongated grooves on the second incident end face side is inclined in the direction opposite to the second incident end face toward the reflecting face with respect to the normal direction. It is desirable to form a scattering reflection portion comprising a concavo-convex surface provided with minute concavo-convex surfaces, and by doing so, the first light having a small divergence angle and the second light having a large divergence angle are formed. Are emitted from the entire exit surface of the light guide plate. , The liquid crystal display device, it is possible to perform display without narrow viewing angle display and the wide viewing angle luminance unevenness.

  In that case, it is preferable that the scattering reflection portion is formed in a shape refracted at least at one location along the depth direction of the elongated groove. By doing so, the second light having a large spread angle is formed. The intensity distribution can be made uniform, and the liquid crystal display element can perform a wide viewing angle display without uneven brightness.

  Furthermore, it is more preferable that the scattering reflection portion is formed in a shape curved along the depth direction of the elongated groove, and in this way, the intensity distribution of the second light having a large spread angle is further increased. It is possible to make the liquid crystal display element perform a wide viewing angle display without luminance unevenness evenly.

  In the liquid crystal display device of the present invention, the surface light source of the present invention is disposed on the opposite side of the liquid crystal display element from the observation side, and the light emitting plate has an emission surface facing the liquid crystal display element. The first light emitting element and the second light emitting element of the surface light source are selectively turned on by the driving means, thereby causing the liquid crystal display element to perform a narrow viewing angle display and a wide viewing angle display. This liquid crystal display device can be obtained at low cost because the viewing angle of the liquid crystal display element can be switched between a narrow viewing angle and a wide viewing angle without providing the viewing angle limiting liquid crystal element. it can.

  1 to 3 show a first embodiment of the present invention. FIG. 1 is a perspective view of a liquid crystal display device, and FIG. 2 is a side view of the liquid crystal display device as viewed from the lower left direction of FIG.

  As shown in FIGS. 1 and 2, the liquid crystal display device includes a liquid crystal display element 1 having a screen region 1a in which a plurality of pixels (not shown) for controlling light transmission are arranged in a matrix, and the liquid crystal display element. 1 is arranged on the side opposite to the observation side (upper side in FIGS. 1 and 2), and is directed toward the liquid crystal display element 1 with the first light A having a small divergence angle as indicated by an arrow in FIG. The surface light source 8 that selectively emits the second light B having a large spread angle as indicated by the broken line in FIG. 2, and the first light A and the second light B from the surface light source 8. And a light source driving means 15 for selectively emitting.

  Although the internal structure of the liquid crystal display element 1 is not shown, a pair of transparent substrates 2 and 3 joined via a frame-shaped sealing material 4 surrounding the screen region 1a and the substrates 2 and 3 are opposed to each other. Liquid crystal sealed in a region surrounded by the sealing material 4 between the pair of substrates 2 and 3 and a transparent electrode which is provided on each inner surface and forms a plurality of pixels arranged in a matrix by regions facing each other. And a pair of polarizing plates 5 and 6 disposed on the outer surfaces of the pair of substrates 2 and 3, respectively.

  The liquid crystal display element 1 includes a plurality of pixel electrodes arranged in a matrix in the row direction and the column direction on the inner surface of one substrate 2, and the arrangement region of the plurality of pixel electrodes on the inner surface of the other substrate 3. An active matrix liquid crystal display element provided with a single film-like counter electrode facing each other, and an inner surface of the one substrate 2 is provided with an active element comprising TFTs respectively connected to the plurality of pixel electrodes, and each row A plurality of gate wirings connected to the TFTs and a plurality of data wirings connected to the TFTs in each column are provided.

  The one substrate 2 has a driver mounting portion 2a extending outward from the other substrate 3, and the plurality of gate wirings and data wirings are led out to the driver mounting portion 2a. The driver is connected to a display driver 7 made of an LSI mounted on the driver mounting unit 2a.

  An alignment film is provided on the inner surfaces of the pair of substrates 2 and 3 so as to cover the electrodes, and the liquid crystal molecules of the liquid crystal layer are defined by the alignment film between the pair of substrates 2 and 3. It is oriented in the orientation state.

  The liquid crystal display element 1 includes a TN or STN type in which liquid crystal molecules are twist-aligned, a vertical alignment type in which liquid crystal molecules are aligned substantially perpendicular to the surfaces of the substrates 2 and 3, and a substrate without twisting the liquid crystal molecules. The liquid crystal display element is either a horizontal alignment type that is aligned substantially parallel to two or three planes or a bend alignment type that bends liquid crystal molecules, or a ferroelectric or antiferroelectric liquid crystal display element. The pair of polarizing plates 5 and 6 are arranged with their transmission axes oriented so as to obtain good contrast characteristics.

  In the liquid crystal display element 1, a vertical electric field (electric field in the thickness direction of the liquid crystal layer) is generated between the electrodes provided on the inner surfaces of the pair of substrates 2 and 3 to change the alignment state of the liquid crystal molecules. For example, a comb-like first and second electrode for forming a plurality of pixels is provided on the inner surface of one of the pair of substrates 2 and 3, and a horizontal electric field ( A lateral electric field control type that changes the alignment state of the liquid crystal molecules by generating an electric field in a direction along the substrate surface may be used.

  Further, the liquid crystal display element 1 may be a normally white mode display element or a normally black mode display element.

  The surface light source 8 is made of a transparent plate member such as an acrylic resin plate, and a first incident end face 10a is formed on one of two end faces facing each other, and a second incident end face 10b is formed on the other end face. An exit surface 11 for emitting light incident from the first and second entrance end surfaces 10a and 10b is formed on one of the two plate surfaces, and incident on the other plate surface from the first entrance end surface 10a. The reflecting surface 12 includes a specular reflecting portion 13 a that specularly reflects the light that is directed toward the emitting surface 11, and a scattering reflecting portion 13 b that scatters and reflects the light incident from the second incident end surface 10 b toward the emitting surface 11. , A first light emitting element 14a that is disposed to face the first incident end surface 10a of the light guide plate 9 and emits light toward the first incident end surface 10a, and the light guide plate Second incident end face 10b of the optical plate 9 It is disposed opposite, and a second light emitting element 14b for emitting light toward the second incident end face 10b.

  The light exit surface 11 of the light guide plate 9 is formed as a flat surface, and the reflection surface 12 has a plurality of elongated grooves substantially parallel to the length direction of the first and second incident end faces over the entire area thereof. 13 is formed at a predetermined pitch.

  1 and 2, the elongated grooves 13 and their pitches are greatly exaggerated, but the elongated grooves 13 have a groove width of about 10 to 30 μm. It is formed at a pitch that is the same as or smaller than the pixel pitch.

  FIG. 3 is an enlarged view of a part of the reflection surface 12 of the light guide plate 9 of the surface light source 8, and the plurality of elongated grooves 13 have a triangular cross-sectional shape in which the groove width increases toward the reflection surface 12. The side surfaces of the elongated grooves 13 on the first incident end surface 10a side, that is, the reflecting surface 12 toward the exit surface 11 are opposite to the first incident end surface 10a (second direction). The mirror-reflecting portion 13a is formed by an inclined surface that is inclined in the direction of the incident end face 10b) and that rises to the right in the figure. The scattering / reflecting portion 13b is formed by an upwardly inclined surface that is inclined in the direction opposite to the second incident end face 10b (in the direction of the first incident end face 10a).

  That is, an inclined surface that is inclined in the direction opposite to the first incident end surface 10a with respect to the normal direction h of the light guide plate 9 of the plurality of elongated grooves 13 and is opposite to the first incident end surface 10a is a mirror surface. An inclined surface that forms a reflecting portion 13a and is inclined in a direction opposite to the second incident end face 10b with respect to the normal direction h of the plurality of elongated grooves 13 and faces the second incident end face 10b. The scattering reflection portion 13b is formed of a concavo-convex surface provided with minute undulations on the surface.

  The specular reflection part 13a and the scattering reflection part 13b formed on the two side surfaces of the reflection surface 12 of the light guide plate 9 and the plurality of elongated grooves 13 are internal reflection surfaces that totally reflect light at the interface with the outside air (air). The specular reflection portion 13a reflects light incident from the first incident end face 10a in a direction within a predetermined spread angle range centering on the normal direction h of the light guide plate 9, and The scattering reflection part 13b reflects the light incident from the second incident end face 10b in a spreading direction larger than the spreading angle of the light reflected by the specular reflection part 13a.

  In this embodiment, the inclination angle θ of the specular reflection part 13a with respect to the normal direction h is set to about 45 °, and the light incident from the first incident end face 10a is transmitted by the specular reflection part 13a by the specular reflection part 13a. The light is reflected in a direction within a spread angle range inclined by about 5 ° to the first incident end face 10a side and the second incident end face 10b side with respect to the line direction h.

  Further, in this embodiment, the scattering reflection portion 13b is an uneven surface formed with a linear concave portion and a convex portion along the length direction of the elongated groove 13, and the normal direction h of the scattering reflection portion 13b. Is set to the same angle as the inclination angle θ of the specular reflection portion 13a, and the light incident from the second incident end face 10b is centered on the normal direction h by the specular reflection portion 13a. The first incident end face 10a and the second incident end face 10b are scattered and reflected in the spreading direction inclined at the same angle, for example, 20 ° to 60 °.

  The scattering reflection portion 13b is formed, for example, by forming a light guide plate 9 in which the two side surfaces of the plurality of elongated grooves 13 are formed as mirror surfaces, and one side surface of each elongated groove 13 of the light guide plate 9 is By rubbing and roughing in a direction parallel to the length direction of the elongated groove 13, or by rubbing and roughing the mold surface corresponding to the scattering reflection portion 13b of the light guide plate molding die in the direction It is the formed uneven surface, and the unevenness has an irregular shape.

  The first and second light-emitting elements 14a and 14b are solid light-emitting elements such as LEDs (light-emitting diodes), and are formed on the first incident end face 10a and the second incident end face 10b of the light guide plate 9, respectively. A plurality of the incident end faces 10a and 10b are arranged to be opposed to each other at intervals in the length direction.

  The surface light source 8 emits light emitted from the first light emitting element 14a and incident on the light guide plate 9 from the first incident end surface 10a with a small spread angle from the surface 11 of the light guide plate 9. The light emitted from the second light emitting element 14b and incident on the light guide plate 9 from the second incident end face 10b is emitted from the exit surface 11 of the light guide plate 9 with a large spread angle. The light incident on the light guide plate 9 from the first incident end face 10a is a plurality of elongated grooves on the exit surface 11 and the reflection surface 12 of the light guide plate 9, as indicated by arrows in FIGS. In the process of being internally reflected by the flat surface portion between 13 and being guided through the light guide plate 9, the light guide plate is formed by the specular reflection portion 13 a formed on the side surface of the plurality of elongated grooves 13 on the first incident end surface 10 a side. Predetermined spread centered on 9 normal direction h Is reflected in the direction of the range, it is emitted at a small spread angle from the exit surface 11 side of the light guide plate 9.

  In addition, the light incident on the light guide plate 9 from the second incident end face 10b is a plurality of light exit surfaces 11 and reflection surfaces 12 of the light guide plate 9 as indicated by broken lines in FIGS. In the process of being internally reflected by the flat surface portion between the elongated grooves 13 and being guided through the light guide plate 9, the scattering reflector 13b formed on the side surface on the second incident end face 10b side of the plurality of elongated grooves 13 The light reflected by the specular reflection portion is reflected in a direction larger than the spread angle of the light, and is emitted from the exit surface 11 of the light guide plate 9 with a large spread angle.

  As described above, the surface light source 8 has the first incident end surface 10a formed on one of the two end surfaces, the second incident end surface 10b formed on the other end surface, and the first surface on one of the two plate surfaces. And an exit surface 11 that emits light incident from the second entrance end surfaces 10a and 10b is formed, and the light incident from the first entrance end surface 10a is mirror-reflected toward the exit surface 11 on the other plate surface. A light guide plate 9 having a reflecting surface 12 having a specular reflection portion 13a and a scattering reflection portion 13b that scatters and reflects light incident from the second incident end surface 10b toward the emission surface 11, and the light guide plate. 9, the first light emitting element 14a that emits light toward the first incident end face 10a, and the second incident end face 10b of the light guide plate 9 are opposed to the first incident end face 10a. And the second incident end face 10 Since the second light emitting element 14b that emits light toward the light source is provided, by selectively lighting the first light emitting element 14a and the second light emitting element 14b, the light guide plate 9 can be A first light A having a small divergence angle, which is incident from one incident end face 10a and reflected by the specular reflecting portion 13a of the reflecting face 12 of the light guide plate 9, and the second incident end face 10b on the light guide plate 9. , And the second light B having a large spread angle reflected by the scattering reflection portion 13b of the reflection surface 12 of the light guide plate 9 can be selectively emitted from the emission surface 11 of the light guide plate 9. .

  Therefore, by disposing the surface light source 8 on the side opposite to the viewing side of the liquid crystal display element 1 and the exit surface 11 of the light guide plate 9 facing the liquid crystal display element 1, it is difficult to manufacture a viewing angle. The liquid crystal display element 1 can perform a narrow viewing angle display and a wide viewing angle display without using the liquid crystal element.

  The surface light source 8 is opposite to the viewing side of the liquid crystal display element, the light exit surface 11 of the light guide plate 9 is opposed to the liquid crystal display element 1, and the second light emitting element 14a is disposed on the second side. The light emitting element 14b is disposed in the left-right direction of the liquid crystal display element 1, that is, in the direction along the horizontal axis of the screen.

  The liquid crystal display device is mounted on a display unit of an electronic device such as a mobile phone. The light source driving means 15 has a narrow viewing angle and a wide viewing angle, for example, by a viewing angle selection key provided on the electronic device. When the narrow viewing angle is selected according to the selection of the viewing angle, the second light emitting element 21 of the surface light source 8 is turned on to display the first light A having a small divergence angle from the surface light source 8 as a liquid crystal display. When the light is emitted toward the element 1 and a wide viewing angle is selected, the second light emitting element 14b of the surface light source 8 is turned on to emit the second light B having a large spread angle from the surface light source 8. It is configured as follows.

  The liquid crystal display device is a color image in which red, green, and blue color filters respectively corresponding to a plurality of pixels are provided on the inner surface of one of the pair of substrates 2 and 3 of the liquid crystal display element 1. The display device may be a field sequential liquid crystal display device that displays a color image without providing a color filter in the liquid crystal display element 1. In the case of a field sequential liquid crystal display device, the first and second light emission of the surface light source 8. The elements 14a and 14b are solid light emitting elements including, for example, a red LED, a green LED, and a blue LED, and light of three colors of red, green, and blue is selectively emitted from the light emitting elements 14a and 14b. do it.

  In this liquid crystal display device, the surface light source 8 is disposed on the opposite side of the liquid crystal display element 1 from the observation side, and the light emission plate 11 is disposed so that the emission surface 11 of the light guide plate 9 faces the liquid crystal display element 1. By means of the means 15, the first light emitting element 14a and the second light emitting element 14b of the surface light source 8 are selectively turned on to perform a narrow viewing angle display and a wide viewing angle display on the liquid crystal display element 1. When the first light emitting element 14a of the surface light source 8 is turned on and the first light A having a small divergence angle is emitted from the emission surface 11 of the light guide plate 9, the liquid crystal When the viewing angle of display of the display element 1 is narrowed, the second light emitting element 14b of the surface light source 8 is turned on, and the second light B having a large spread angle is emitted from the emission surface 11 of the light guide plate 9. Increases the viewing angle of the display of the liquid crystal display element 1

  Further, in the liquid crystal display device, the surface light source 8 is arranged on the arrangement side of the first light emitting element 14a and the arrangement side of the second light emitting element 14b along the horizontal direction of the liquid crystal display element 1 (along the horizontal axis of the screen). The viewing angle of display in the left-right direction of the liquid crystal display element 1 can be switched between a narrow viewing angle and a wide viewing angle.

  In this way, the liquid crystal display device can be obtained at low cost because the viewing angle of the liquid crystal display element 1 can be switched between a narrow viewing angle and a wide viewing angle without providing the viewing angle limiting liquid crystal element. Can do.

  Further, the surface light source 8 causes the light incident on the light guide plate 9 from the first incident end surface 10a to pass through the mirror surface reflecting portion 13a of the reflection surface 12 of the light guide plate 9 in the normal direction h of the light guide plate 9. (In this embodiment, the spread angle is inclined by about 5 ° with respect to the first incident end face 10a side and the second incident end face 10b side with the normal line direction h as the center). The light that is reflected in the direction within (range) and is emitted from the emission surface 11 of the light guide plate 9 and incident on the light guide plate 9 from the second incident end surface 10b is scattered and reflected by the reflection surface 12 of the light guide plate 9. The spread direction larger than the spread angle of the light reflected by the specular reflection section 13a by the section 13b (for example, on the first incident end face 10a side and the second incident end face 10b side with respect to the normal direction h, respectively) Tilt by 20-60 degrees In the liquid crystal display element 1, the front direction (the direction near the normal line of the liquid crystal display element 1) is narrowed with the display viewing direction being reflected from the light exiting surface 11 of the light guide plate 9. A viewing angle display and a wide viewing angle display in which the display can be observed from an oblique direction with respect to the front direction can be performed.

  In addition, the surface light source 8 has a plurality of elongated grooves 13 substantially parallel to the length direction of the first and second incident end faces 10a and 10b over the entire reflection surface 12 of the light guide plate 9. The first incident light is formed at a predetermined pitch and is directed toward the reflecting surface 12 with respect to the normal direction h of the light guide plate 9 by the side surfaces of the elongated grooves 13 on the first incident end surface 10a side. A specular reflection portion 13a having an inclined surface inclined in a direction opposite to the end surface 10a is formed, and the reflection with respect to the normal direction h is performed by a side surface of the plurality of elongated grooves 13 on the second incident end surface 10b side. Since the scattering reflection portion 13b is formed of a concavo-convex surface provided with minute concavo-convex on a surface inclined in the direction opposite to the second incident end surface 10b toward the surface 12, the first light beam having a small divergence angle. 1 light A and a large spread angle Second the light B emitted from the entire emission surface 11 of the light guide plate 9, respectively, in the liquid crystal display device 1, it is possible to perform display without narrow viewing angle display and the wide viewing angle luminance unevenness.

  In the surface light source 8 of the first embodiment, the scattering / reflecting portion 13b of the reflecting surface 12 of the light guide plate 9 is set at a certain angle (with respect to the normal direction h of the light guide plate 9) (of the specular reflecting portion 13a). The scattering reflection portion 13b is formed in a shape bent at least at one location along the depth direction of the elongated groove 13. Alternatively, it is preferable to form the elongated groove 13 in a curved shape along the depth direction.

  FIG. 4 is an enlarged view of a part of the reflecting surface 12 of the light guide plate 9 of the surface light source 8 showing the second embodiment of the present invention.

  The surface light source 8 is formed by bending the scattering reflection portion 13b of the reflection surface 12 of the light guide plate 9 along the depth direction of the elongated groove 13 at the intermediate portion in the depth direction. Yes, in this embodiment, the inclination angle of the portion of the scattering reflection portion 13b from the intermediate portion to the reflection surface 12 side with respect to the normal direction h of the light guide plate 9 is about 60 °, and the portion from the intermediate portion to the groove bottom side Is set to about 30 °.

  In this surface light source 8, the scattering reflection portion 13b is formed in a shape bent along the depth direction of the elongated groove 13, so that the intensity distribution of the second light B having a large spread angle is made uniform. The liquid crystal display element 1 can perform a wide viewing angle display without uneven brightness.

  In this embodiment, the scattering reflection portion 13b is formed in a shape bent at one place in the middle of the elongated groove 13 in the depth direction, but the scattering reflection portion 13b is formed in the elongated groove 13. It may be formed in a shape bent at a plurality of locations in the depth direction.

  FIG. 5 is an enlarged view of a part of the reflecting surface 12 of the light guide plate 9 of the surface light source 8 showing the third embodiment of the present invention.

  The surface light source 8 is formed by forming the scattering reflection portion 13b of the reflection surface 12 of the light guide plate 9 into a curved shape along the depth direction of the elongated groove 13. In this embodiment, the scattering reflection portion is formed. The part 13 b is formed in an arc shape that is convex toward the inner direction of the light guide plate 9.

  In this surface light source 8, since the scattering reflection portion 13 b is formed in a shape curved along the depth direction of the elongated groove 13, the intensity distribution of the second light B having a large spread angle is more even. In addition, the liquid crystal display element 1 can perform a wide viewing angle display without uneven brightness.

  The surface light source 8 can be used not only for the liquid display element device but also for other optical devices that selectively use light having a wide spread angle and light having a narrow spread angle.

1 is a perspective view of a liquid crystal display device showing a first embodiment of the present invention. The side view which looked at the said liquid crystal display device from the lower left direction of FIG. The enlarged view of a part of reflective surface of the light-guide plate of the surface light source of a 1st Example. The enlarged view of a part of reflective surface of the light-guide plate of the surface light source which shows 2nd Example of this invention. The enlarged view of a part of reflective surface of the light-guide plate of the surface light source which shows 3rd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element, 1a ... Screen area | region, 8 ... Surface light source, 9 ... Light guide plate, 10a, 10b ... Incident end surface, 11 ... Outgoing surface, 12 ... Reflecting surface, 13 ... Elongated groove, 13a ... Specular reflection part, 13b ... scattering reflection part, 14a, 14b ... light emitting element, A ... first light, B ... 21st light, 15 ... light source driving means.

Claims (6)

  The first incident end surface is formed on one of the two end surfaces facing each other, the second incident end surface is formed on the other end surface, and the first and second plate surfaces are formed on one of the two plate surfaces. An exit surface that emits light incident from the second entrance end surface is formed, and a mirror reflection portion that specularly reflects light incident from the first entrance end surface toward the exit surface on the other plate surface and the first surface A light guide plate having a reflection surface having a scattering reflection portion that scatters and reflects light incident from the two incident end surfaces toward the emission surface, and is disposed to face the first incident end surface of the light guide plate, A first light emitting element that emits light toward the first incident end face; and a second light emitting element that is disposed to face the second incident end face of the light guide plate and emits light toward the second incident end face. A surface light source comprising a light emitting element.   The specular reflection part of the reflection surface of the light guide plate reflects light incident from the first incident end surface in a direction within a predetermined spread angle range centering on the normal direction of the light guide plate, The surface light source according to claim 1, wherein the scattering reflection unit reflects light incident from the second incident end surface in a spreading direction larger than a spreading angle of the light reflected by the specular reflection unit.   A plurality of elongated grooves that are substantially parallel to the length direction of the first and second incident end faces are formed at a predetermined pitch on the reflective surface of the light guide plate over the entire area. A plurality of the plurality of the specular reflection portions formed by an inclined surface inclined in a direction opposite to the first incident end surface toward the reflection surface with respect to a normal direction of the light guide plate. Due to the side surface on the second incident end face side of the elongated groove, minute irregularities are provided on the surface inclined in the direction opposite to the second incident end face toward the reflecting surface with respect to the normal direction. The surface light source according to claim 1, wherein a scattering reflection portion including an uneven surface is formed.   The surface light source according to claim 3, wherein the scattering reflection part is formed in a shape bent at at least one location along the depth direction of the elongated groove.   The surface light source according to claim 3, wherein the scattering reflection part is formed in a curved shape along the depth direction of the elongated groove. A liquid crystal display element having a screen region in which a plurality of pixels for controlling light transmission are arranged in a matrix, and
The first incident end surface is formed on one of the two end surfaces facing each other, the second incident end surface is formed on the other end surface, and the first and second plate surfaces are formed on one of the two plate surfaces. An exit surface that emits light incident from the second entrance end surface is formed, and a mirror reflection portion that specularly reflects light incident from the first entrance end surface toward the exit surface on the other plate surface and the first surface A light guide plate formed with a reflection surface having a scattering reflection portion that scatters and reflects light incident from the two incident end surfaces toward the emission surface, and is disposed to face the first incident end surface of the light guide plate, A first light emitting element that emits light toward the first incident end face; and a second light emitting element that is disposed to face the second incident end face of the light guide plate and emits light toward the second incident end face. A light emitting element, and the light guide plate on a side opposite to the observation side of the liquid crystal display element And they arranged a surface light source so as to face the liquid crystal display device the emission surface,
A liquid crystal display device comprising light source driving means for selectively lighting the first light emitting element and the second light emitting element of the surface light source.

Images