JP2005208108A - Double-sided image display device and surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce difference between screen luminance of a main liquid crystal panel in a region corresponding to a sub liquid crystal panel and screen luminance of the main liquid crystal panel in a region corresponding to a frame member, in a double-sided image display device wherein sizes of image display regions of the main liquid crystal panel and the sub liquid crystal panel are different from each other. <P>SOLUTION: The large-sized main liquid crystal panel 22 and the small-sized sub liquid crystal panel 24 are opposed to each other on both surfaces of a surface light source device 23. The frame member 28 having low reflectance is disposed on the outer side of the sub liquid crystal panel 24 between the surface light source device 23 and the sub liquid crystal panel 24. A polarization adjusting plate 27 is interposed between the surface light source device 23, and the sub liquid crystal panel 24 and the frame member 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a double-sided image display device and a surface light source device including image display panels having different sizes.

  Recently, double-sided image display devices have been used in foldable mobile phones and the like. In a double-sided image display device used for a folding portable phone or the like, one surface is a relatively large display surface, and the other surface is a smaller display surface.

  FIG. 1 is a schematic cross-sectional view showing the structure of a conventional double-sided image display apparatus. This double-sided image display device includes a single-sided display type liquid crystal display device 3 composed of a large-sized liquid crystal panel 1 and a backlight 2, and a single-sided display type liquid crystal display device 6 composed of a small-sized liquid crystal panel 4 and a backlight 5. Are arranged back to back via a double-sided reflector 7. Each of the backlights 2 and 5 includes a light source 8 and a light guide plate 9. Light emitted from the light source 8 enters the light guide plate 9 and spreads in the light guide plate 9, and light is emitted from almost the entire surface of the light guide plate 9. The light is emitted. In this way, images are displayed by the front and back liquid crystal display devices 3 and 6, respectively.

  However, the double-sided image display device having such a structure has a disadvantage that the thickness of the double-sided image display device is increased because the two liquid crystal display devices 3 and 6 are used in an overlapping manner. Further, since the two backlights 2 and 5 are used, there are disadvantages that the cost is high and the loss of light increases.

  Therefore, it has been proposed to reduce the thickness and cost of a double-sided image display device by illuminating two liquid crystal panels with one light guide plate. FIG. 2 is a schematic sectional view showing the structure of such a double-sided image display device (for example, disclosed in Patent Document 1), and shows a state in which a liquid crystal panel is illuminated by a backlight. In this double-sided image display device, as shown in FIG. 2, a large liquid crystal panel 14 (hereinafter referred to as a main liquid crystal panel) is opposed to one surface of a backlight 13 comprising a light source 11 and a light guide plate 12. ), A small liquid crystal panel 15 (hereinafter referred to as a sub liquid crystal panel) is disposed so as to face the other surface of the backlight 13, and a polarization matching sheet 16 is attached to the upper surface of the sub liquid crystal panel 15. A frame member 17 covers the periphery of the upper surface of the sub liquid crystal panel 15. The frame member 17 is made of a material having high reflectivity.

  Therefore, as shown in FIG. 2, when the backlight 13 is turned on, light is emitted from the entire lower surface of the backlight 13. Of the light emitted from the lower surface of the central portion of the backlight 13 toward the sub liquid crystal panel 15, one polarization state component (this is P-polarized light) is reflected by the polarization matching sheet 16 and the other. Of the polarization state (this is S-polarized light) passes through the polarization matching sheet 16. The P-polarized light reflected by the polarization matching sheet 16 passes through the light guide plate 12 and illuminates the central portion of the main liquid crystal panel 14 from below. The S-polarized light transmitted through the polarization matching sheet 16 reaches the sub liquid crystal panel 15 from the upper surface side. On the other hand, the light emitted from the lower surface of the outer peripheral portion of the backlight 13 toward the frame member 17 is reflected upward by the frame member 17 and illuminates the outer peripheral portion of the main liquid crystal panel 14 from the lower surface side.

  Therefore, if the reflectance of the polarization matching sheet 16 is 50% and the transmittance is 50%, and the reflectance of the frame member 17 is 100%, the opening (or the frame member 17 of the main liquid crystal panel 14 (or The area facing the sub liquid crystal panel 15) is illuminated with 50% of the light emitted from the backlight 13 (P-polarized light), whereas the area facing the frame member 17 is 100%. Illuminated with light (P-polarized light and S-polarized light). As a result, the luminance of the screen of the main liquid crystal panel 14 is as shown in FIG. 3, and is dark at the center and bright at the periphery. Therefore, in the conventional double-sided image display device, the luminance of the main liquid crystal panel 14 cannot be made uniform between the region facing the frame member 17 and the region facing the sub liquid crystal panel 15.

  FIG. 4 shows the relationship between the viewing direction of the main liquid crystal panel 14 and the screen brightness when the backlight 13 is lit. 4 represents the screen luminance of the main liquid crystal panel 14 in the region facing the sub liquid crystal panel 15, and the curved line illustrated in broken lines in FIG. 4 represents the main liquid crystal panel 14 in the region facing the frame member 17. The screen brightness is represented, and the horizontal axis of FIG. 4 represents the inclination from the direction perpendicular to the main liquid crystal panel 14. As shown in FIG. 4, the luminance is high in front of the main liquid crystal panel 14, but the luminance gradually decreases as the inclination from the direction perpendicular to the main liquid crystal panel 14 increases. Therefore, even if the luminance difference between the region facing the sub liquid crystal panel 15 and the region facing the frame member 17 is the same, the luminance difference is recognized because the luminance of the entire screen is high in the front direction of the main liquid crystal panel 14. Although it is difficult, the luminance difference is easily recognized because the luminance of the entire screen is low in the oblique direction. Therefore, there is a problem that the edge of the opening of the frame member 17 appears as a luminance difference on the main liquid crystal panel 14 when viewed carefully from an oblique direction (particularly, a direction inclined by 30 to 60 ° from the vertical direction). In particular, when the number of sheets such as a diffusion sheet between the light guide plate 12 and the main liquid crystal panel 14 is reduced, the edge of the opening of the frame member 17 is easily seen.

JP 2003-177406 A

  The present invention has been made in view of the technical problems as described above, and an object of the present invention is to provide a screen in a double-sided image display device in which the size of the image display area is different between the main liquid crystal panel and the sub liquid crystal panel. The purpose is to make the screen luminance of a large main liquid crystal panel uniform.

  A first double-sided image display device according to the present invention has a light source, a light guide plate that guides light from the light source, spreads the light in a plane, and emits the light, and has a size arranged to face both surfaces of the light guide plate. In a double-sided image display device comprising different image display panels, a frame member surrounding the periphery of the small image display panel when viewed from the direction perpendicular to the light guide plate is provided in the vicinity of the small image display panel, and The surface of the frame member facing at least the light guide plate is a surface having a small reflectance, and a transflective plate is disposed between the frame member and the small image display panel and the large image display panel. It is a feature. Here, the semi-transmissive and semi-reflective plate transmits a part of the incident light and reflects a part of the light, and includes, for example, a polarization matching plate and a half mirror. The polarizing plate theoretically transmits a part of the incident light and absorbs the remaining light, but the actual polarizing plate does not have a reflectance of 0%, and a part of the light. Therefore, the transflective plate in the present invention includes a polarizing plate. The transflective plate is larger than the size of the opening of the frame member. The reflectance of the surface of the frame member facing the light guide plate may be 30% or less, but is desirably as small as possible.

  The transflective plate is disposed between the frame member and the small image display panel (hereinafter referred to as sub-panel) and the large image display panel (hereinafter referred to as main panel). The transflective plate may be disposed between the frame member and the sub panel and the light guide plate, or may be disposed between the main panel and the light guide plate.

  According to the first double-sided image display device, light emitted from the light guide plate and reflected by the transflective plate (or light transmitted through the transflective plate) is incident on the main panel and Illuminate almost uniformly. On the other hand, the light emitted from the light guide plate and transmitted through the semi-transmissive semi-reflective plate (or the light reflected by the semi-transmissive semi-reflective plate) enters the sub panel and the frame member, and illuminates the sub panel substantially uniformly. In addition, since the light incident on the frame member at this time is less reflected by the frame member, the light reflected by the frame member is reflected by the semi-transmissive semi-reflective plate (or light transmitted through the semi-transmissive semi-reflective plate). It is possible to prevent overlapping and brightening in a region corresponding to the frame member in the main panel. Therefore, according to this double-sided image display device, the difference in screen brightness between the area corresponding to the frame member and the area corresponding to the sub-panel can be reduced on the main panel.

  A first surface light source device according to the present invention is disposed so as to face a light source, a light guide plate that guides light from the light source, spreads it in a planar shape, and emits the light, and faces one surface of the light guide plate. At least one of a frame member whose surface facing the optical plate is a surface having a small reflectance, and one surface of the light guide plate and the middle of the frame member, or a position facing the other surface of the light guide plate. And a semi-transparent semi-reflective plate.

  The first surface light source device of the present invention can constitute the first double-sided image display device according to the present invention in combination with two kinds of large and small image display panels (that is, a main panel and a sub panel).

  In an embodiment of the first surface light source device, it is desirable to use a polarization matching plate that transmits light of a certain polarization direction and reflects light of a different polarization direction as the transflective plate. A desirable effect can be obtained by using a polarization matching plate as the semi-transmissive / semi-reflective plate. The light with a certain polarization direction is not limited to linearly polarized light with a certain polarization direction, and may refer to elliptically polarized light or circularly polarized light rotating in one direction.

  Further, in the case where a polarization matching plate that transmits linearly polarized light in a certain polarization direction and reflects linearly polarized light in a polarization direction orthogonal thereto is disposed on both surfaces of the light guide plate, It is desirable to arrange the directions of the polarization transmission axes to be orthogonal to each other. By arranging the directions of the polarization transmission axes of the polarization matching plate to be orthogonal, the utilization efficiency of the light emitted from the light guide plate can be optimized. The polarization transmission axis of the polarization matching plate refers to a direction parallel to the vibration surface of the electric field direction component of the light transmitted through the polarization matching plate.

  In the first surface light source device of the present invention, it is preferable that the light guide plate emits light from a surface facing the transflective plate. When the transflective plate is disposed only on one side of the light guide plate, the light may be emitted from the light guide plate toward the transflective plate. When the transflective plates are arranged on both sides of the light guide plate, light may be emitted from both sides of the light guide plate, or light may be emitted from either one of them.

  The light guide plate is preferably transparent. If the light guide plate is transparent, the light reflected by the semi-transmissive and semi-reflective plate is not absorbed or shielded when passing through the light guide plate, and the light use efficiency can be improved. it can. On the other hand, if the light guide plate is opaque, it is difficult for the reflected light to reach the main panel even if a little light is reflected by the frame member, and the difference in screen brightness between the area corresponding to the frame member and the area corresponding to the sub panel in the main panel. If the light guide plate is transparent or the light guide plate is transparent, the light reflected by the frame member can easily reach the main panel. However, according to the present invention, even when the light guide plate is transparent, the difference in screen luminance between the region corresponding to the frame member and the region corresponding to the sub panel in the main panel can be suppressed.

  In the first surface light source device of the present invention, the light guide plate has a pattern formed on one surface, and a transflective plate is disposed on both sides of the light guide plate so as to face each other. Also good. According to such a configuration, even if there is a reflection whose polarization state changes on the surface of the frame member or the surface of the sub-panel, the reflected light is prevented from reaching the main panel and corresponds to the frame member on the main panel. The difference in screen brightness between the area to be displayed and the area corresponding to the sub-panel can be reduced.

  A second double-sided image display device according to the present invention has a light source, a light guide plate that guides light from the light source, spreads the light in a plane, and emits the light, and has a size arranged to face both surfaces of the light guide plate. In a double-sided image display device comprising different image display panels, a semi-transmissive semi-reflective plate is disposed on the back surface of the small-side image display panel, and the small-side image display panel is viewed from a direction perpendicular to the light guide plate. A frame member surrounding the periphery is provided in the vicinity of the image display panel on the small side, and the reflectance of the surface of the frame member facing the light guide plate is equal to the reflectance of the transflective plate. It is a feature.

  In the second double-sided image display device, the reflectance of the surface of the frame member facing the light guide plate is equal to the reflectance of the semi-transmissive / semi-reflective plate, so that it is reflected to the main panel side. The amount of light becomes uniform, and the difference in screen brightness between the area corresponding to the frame member and the area corresponding to the sub panel in the main panel can be reduced.

  A second surface light source device according to the present invention includes a light source, a light guide plate that guides light from the light source, spreads the light in a planar shape, and emits the light, and a frame member disposed to face one surface of the light guide plate. And a transflective plate disposed in the opening of the frame member when viewed from the direction perpendicular to the light guide plate, the reflectance of the surface of the frame member facing the light guide plate and the semi-transmissive The reflectance of the semi-reflecting plate is equal.

  The second surface light source device of the present invention can constitute the second double-sided image display device according to the present invention in combination with two kinds of large and small image display panels (that is, a main panel and a sub panel).

  The above-described constituent elements of the present invention can be arbitrarily combined as much as possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the Example described below is an example, Comprising: This invention is not limited to a following example.

  FIG. 5 is an exploded perspective view showing the configuration of the double-sided image display device 91 according to the first embodiment of the present invention, and FIG. 6 is a schematic sectional view of the device. The double-sided image display device 91 includes a relatively large liquid crystal panel (hereinafter referred to as a main liquid crystal panel) 22, a surface light source device 23, and a relatively small liquid crystal panel (hereinafter referred to as a sub liquid crystal panel). The main liquid crystal panel 22 is disposed so as to face one surface of the surface light source device 23 (hereinafter, this surface is referred to as an upper surface according to the drawing), and the sub liquid crystal panel 24 is a surface light source. It arrange | positions so that the other surface (Hereafter, this surface is made into a lower surface according to a figure.) Of the apparatus 23 may be opposed. The surface light source device 23 includes a small light source 25 (hereinafter referred to as a point light source), a light guide plate 26, a polarization matching plate 27 (a kind of transflective plate), and a frame member 28. The light source 25 is a light guide plate 26. Are accommodated in holes 29 provided at the corners of the

  The light guide plate 26 is formed in a substantially rectangular flat plate shape using a transparent resin or glass having a high refractive index such as polycarbonate resin, acrylic resin, or methacrylic resin. FIG. 7 is a plan view of the light guide plate 26. On the surface of the light guide plate 26, a non-light emitting region 31 is formed around a rectangular surface light emitting region 30 that is a substantial surface light source, and at the end of the short side of the rectangular light guide plate 26, A hole 29 for fitting the point light source 25 is opened in the light emitting region 31. The point light source 25 is a resin-molded light emitting diode (LED) chip, mounted on a film wiring board (FPC) 32 for supplying power to the point light source 25, and inserted into the hole 29 of the light guide plate 26. ing.

  FIG. 8 is a sectional view showing the structure of the point light source 25. The point light source 25 is obtained by sealing a light emitting diode chip 33 in a transparent resin 34 and covering a surface other than the front surface with a white transparent resin 35. The point light source 25 is mounted on the film wiring board 32 and fixed by solder 36. Furthermore, the film wiring board 32 is fixed to a reinforcing plate 37 made of glass epoxy resin. As described above, the hole 29 for accommodating the point light source 25 passes vertically in the corner of the light guide plate 26, and the positioning pin 38 projects from the lower surface of the light guide plate 26 in the vicinity thereof. On the other hand, the film wiring board 32 and the reinforcing plate 37 are provided with through holes 39 and 40 for passing the positioning pins 38.

  Then, an ultraviolet curable adhesive (or a thermosetting adhesive) 41 is applied to the lower surface of the light guide plate 26 around the base portion of the positioning pin 38, and the positioning pin 38 is connected to the film wiring board 32 and the reinforcing plate. The UV curable adhesive 41 is cured by irradiating ultraviolet rays after positioning the center of the light guide plate 26 in the thickness direction and the light emission center of the point light source 25 with a CCD camera or the like. Then, the light guide plate 26 and the point light source 25 are bonded to each other, and the positioning pins 38 are heat caulked to the reinforcing plate 37.

  At this time, as shown in FIG. 8, the projection 42 provided on the inner surface of the hole 29 of the light guide plate 26 (the back side, the front side, or both of the point light source 25) may be used. Positioning in the vertical direction of the center may be performed. Although not shown, the light guide plate 26 is used with a stepped jig for positioning the upper surface of the light guide plate 26 and the upper surface of the point light source 25 with the light guide plate 26 and the point light source 25 turned upside down. And the center of the point light source 25 may be positioned.

  In place of the film wiring board 32, a glass epoxy wiring board or a lead frame may be used. When two or more light emitting diode chips are used, a point light source may be formed by collecting a plurality of light emitting diode chips in one place. The point light source 25 may be formed by insert-molding a light-emitting diode chip directly into the light guide plate 26, and is disposed outside the light guide plate 26 (position facing the outer peripheral surface of the light guide plate 26). Also good.

  As shown in FIG. 9, a large number of triangular prism-shaped deflection patterns 43 are recessed in the surface light emitting region 30 on the surface of the light guide plate 26, and are arranged concentrically around the point light source 25. The distance between the deflection patterns 43 is relatively wide on the side close to the point light source 25, and the distance gradually decreases as the distance from the point light source 25 increases. As a result, the lower surface of the light guide plate 26 (hereinafter referred to as the light emitting surface 44). And the brightness | luminance in the surface (henceforth pattern surface 45) is made uniform. Hereinafter, the deflection pattern 43 will be described in detail.

FIG. 10A is a plan view showing the shape of the deflection pattern 43, and FIG. 10B is an enlarged sectional view thereof. The deflection pattern 43 has a substantially uniform cross section in the length direction, and is arranged so that the length direction is substantially perpendicular to the direction connected to the point light source 25. The deflection pattern 43 used in this embodiment is slightly wavy as shown in FIG. As shown in FIG. 10B, each deflection pattern 43 includes a deflection inclined surface 46 located on the point light source side and a re-incident surface 47 located on the side far from the point light source 25. The incident surface 47 is substantially triangular in cross section. The inclination angle γ of the deflection inclined surface 46 and the inclination angle δ of the re-incident surface 47 are:
γ <δ,
γ = 45 ° to 65 °
δ = 80 ° -90 °
Is desirable. In particular, the inclination angle γ of the deflection inclined surface 46 is preferably about 50 °.

  As shown in FIG. 6, when the light 48 emitted from the point light source 25 passes through the inner wall surface (light incident surface) of the hole 29 and enters the light guide plate 26, the light 48 incident on the light guide plate 26. Is propagated through the light guide plate 26 by repeating total reflection on the lower surface (light emitting surface 44) and the upper surface (pattern surface 45) of the light guide plate 26, and spreads in a planar shape over the entire surface light emitting region 30 of the light guide plate 26. . During the propagation, the light incident on the deflection inclined surface 46 of the deflection pattern 43 from below is totally reflected by the deflection inclined surface 46 toward the light emitting surface 44 as shown in FIG. The light exits from the light exit surface 44 such that the direction is substantially perpendicular to the light exit surface 44. In addition, the light incident on the deflection inclined surface 46 of the deflection pattern 43 from below during transmission is transmitted through the deflection inclined surface 46 and re-entered into the light guide plate 26 from the re-incident surface 47 as shown in FIG. Incident. Therefore, the direction of the light beam propagating through the light guide plate 26 and the direction of the light emitted from the light emitting surface 44 and the pattern surface 45 are lateral (point light sources) when viewed from the direction perpendicular to the pattern surface 45. (A direction along the circumference centered at 25) is not scattered so much and proceeds almost radially around the point light source 25.

  12A, 12B, 12C, and 12D show how the entire deflection pattern 43 is arranged, FIG. 13 shows the change in the pattern density (area ratio) of the deflection pattern 43 in the radial direction, and FIG. FIG. 15 shows a change in the number of patterns per unit area. Here, r represents the distance from the point light source 25. The deflection pattern 43 increases in density as the distance r from the point light source 25 increases as shown in FIG. This is to make the luminance of the light emitting surface 44 and the pattern surface 45 uniform. As a method of gradually increasing the deflection pattern density, it is possible to gradually increase the number of deflection patterns per unit area. However, in this embodiment, a plurality of light guide plates 26 are provided according to the distance from the point light source 25. In each zone, as shown in FIG. 15, the number of deflection patterns per unit area is fixed and the number of deflection patterns per unit area is increased stepwise for each zone. As shown in FIG. 14, the length of the deflection pattern is gradually changed in each zone. In addition, the pattern length once becomes shorter at the zone boundary.

  FIGS. 12B, 12C, and 12D specifically show the deflection patterns 43 at the points a, b, and c in FIG. 12A, respectively. FIG. 12B shows the region a closest to the point light source 25, and the pitch in the radial direction and the circumferential direction of the deflection pattern 43 are both 140 μm, and the inner deflection pattern 43 and the outer deflection pattern 43 Are not overlapped in the radial direction. FIG. 12C shows an intermediate region B, in which both the pitch in the radial direction and the pitch in the circumferential direction of the deflection pattern 43 are 70 μm, and there are two rows of the inner deflection pattern 43 and the outer deflection pattern 43. It overlaps one by one. FIG. 12D shows a region C far from the point light source 25, where the pitch in the radial direction is 35 μm and the pitch in the circumferential direction is 140 μm. 12B, 12C, and 12D show the linearly extending deflection pattern, the wavy deflection pattern 43 as shown in FIG. 10A is shown in FIGS. 12B and 12C. You may arrange | position like (d).

  Further, the long side of the light guide plate 26 on the side opposite to the end where the point light source 25 is disposed is formed straight, whereas the long side of the light guide plate 26 on the side close to the point light source 25 has one or more steps. It is cut diagonally. Similarly, in the vicinity of the point light source 25, the short side is also partially formed obliquely. If slope portions 49 and 50 are provided on the long side and the short side respectively close to the point light source 25, as shown in FIG. 16, a part of the light 48 emitted from the point light source 25 is converted into the long side slope portion 49. Thus, the light 48 can be sent to the corners of the light guide plate 26 (the hatched area in FIG. 16). When the point light source 25 is placed at the corner of the light guide plate 26, the other corner portions tend to be dark, but according to such a structure, the light totally reflected by the slope portions 49 and 50 is reflected on the light guide plate 26. By sending to the corner of the surface light emitting region 30, the luminance distribution of the light emitting surface 44 and the pattern surface 45 can be made more uniform, and the efficiency of the surface light source device 41 can be increased.

  A polarization matching plate 27 is disposed at a position facing the light exit surface 44 of the light guide plate 26. The polarization matching plate 27 has a larger area than the pixel formation region of the main liquid crystal panel 22. The polarization matching plate 27 transmits linearly polarized light in one polarization direction of incident light and reflects linearly polarized light in a polarization direction orthogonal to the polarized light. In the first embodiment, the polarization direction of light reflected by the polarization matching plate 27 is P-polarized light, and the polarization direction of light transmitted through the polarization matching plate 27 is S-polarized light. An example of such a polarization matching plate 27 is D-BEF (trade name) manufactured by Sumitomo 3M Limited. The polarization matching plate may be one that transmits circularly polarized light or elliptically polarized light in one rotational direction and reflects circularly polarized light or elliptically polarized light in the other rotational direction. As a polarization matching plate that divides the transmission side and the reflection side, for example, there is NIPOCS-PCF (trade name) manufactured by Nitto Denko Corporation.

  The frame member 28 located between the polarization matching plate 27 and the sub liquid crystal panel 24 includes an opening 51. The outer shape of the frame member 28 is larger than at least the pixel formation region of the main liquid crystal panel 22, and the size of the opening 51 is slightly smaller than the outer shape of the sub liquid crystal panel 24. Therefore, when the sub liquid crystal panel 24 and the frame member 28 are overlapped, they can be overlapped so that there is no gap between the opening 51 of the frame member 28 and the outer periphery of the sub liquid crystal panel 24 when viewed from above. Further, at least the upper surface of the frame member 28 has a low light reflectance. For example, in order to make the upper surface of the frame member 28 have a low reflectance, the frame member 28 is manufactured with a black light shielding plate (for example, Lumirror, X-30 manufactured by Toray Industries, Inc.), or Cr is formed on the surface of a stainless steel plate. What is necessary is just to use what gave plating, or what gave antireflection coating on the surface. In addition, in the method of using a stainless plate plated with Cr as the frame member 28, the strength of the frame member 28 can be increased. Further, the frame member 28 does not have to be a dedicated component, and may be a part of a casing or the like of a device in which the double-sided image display device 91 is incorporated.

  The main liquid crystal panel 22 and the sub liquid crystal panel 24 are a transmission type or a semi-transmission type in which a liquid crystal is sealed between a glass substrate on which a switching element such as a TFT or an opening electrode is formed and a glass substrate on which a transparent electrode is formed. A liquid crystal panel that is normally black or has a low transmittance is used. When using a liquid crystal panel that is attached with a polarizing film or the like and transmits only linearly polarized light in one direction, the main liquid crystal panel 22 is arranged in a direction to transmit P-polarized light, and the sub-liquid crystal panel 24 is S-polarized. It arrange | positions in the direction which light permeate | transmits.

  Next, the operation and effect when the surface light source device 23 is turned on in the double-sided image display device 91 according to the present invention will be described with reference to FIGS. When the surface light source device 23 is turned on, the light 48 emitted from the point light source 25 enters the light guide plate 26 from the light incident surface of the light guide plate 26 as shown in FIG. It propagates while repeating total reflection between the lower surface (light emitting surface 44) and the upper surface (pattern surface 45), and spreads over the entire light guide plate 26. When the light 48 propagating in the light guide plate 26 enters the deflection pattern 43, the light 48 is totally reflected by the deflection inclined surface 46 of the deflection pattern 43 in a direction substantially perpendicular to the light emitting surface 44, The light exits from the light exit surface 44 substantially vertically downward.

  FIG. 17 illustrates a state where the surface light source device 23 is lit, the main liquid crystal panel 22 is on, and the sub liquid crystal panel 24 is off. The light 48 emitted from the lower surface of the surface light source device 23 toward the sub liquid crystal panel 24 is incident on the polarization matching plate 27, the P-polarized light is reflected by the polarization matching plate 27, and the S-polarized light is reflected by the polarization matching plate. 27 is transmitted. The P-polarized light reflected by the polarization matching plate 27 passes through the light guide plate 26 and illuminates the entire main liquid crystal panel 22 from the lower surface. Therefore, if the main liquid crystal panel 22 is turned on, an image of the main liquid crystal panel 22 is generated. Of the S-polarized light transmitted through the polarization matching plate 27, the light incident on the upper surface of the frame member 28 is absorbed by the frame member 28. The S-polarized light incident on the opening 51 of the frame member 28 illuminates the entire sub liquid crystal panel 24. Since the sub liquid crystal panel 24 is a normally black or low transmittance panel, if the sub liquid crystal panel 24 is turned off, the S-polarized light is absorbed by the sub liquid crystal panel 24. The screen is kept black.

  FIG. 18 illustrates a state where the surface light source device 23 is lit, the main liquid crystal panel 22 is off, and the sub liquid crystal panel 24 is on. In this case, the P-polarized light reflected by the polarization matching plate 27 is absorbed by the main liquid crystal panel 22, and the main liquid crystal panel 22 is normally black or a low-transmittance panel, so it is turned off. The screen of the main liquid crystal panel 22 is kept black. On the other hand, since the S-polarized light transmitted through the polarization matching plate 27 reaches the sub liquid crystal panel 24 that is turned on, an image of the sub liquid crystal panel 24 is generated.

  FIG. 19 illustrates a case where the main liquid crystal panel 22 is turned on and the light 22 is illuminated by external light incident from the main liquid crystal panel 22 side. As for the outside light incident on the main liquid crystal panel 22 that is turned on, only the P-polarized light is transmitted through the main liquid crystal panel 22, and the P-polarized light transmitted through the main liquid crystal panel 22 is transmitted through the light guide plate 26 and is polarized. The light is reflected by the alignment plate 27 and returns to the main liquid crystal panel 22 again to illuminate the main liquid crystal panel 22. Thus, an image is generated on the main liquid crystal panel 22. On the other hand, since the light does not reach the sub liquid crystal panel 24, the screen of the sub liquid crystal panel 24 is kept black.

  Next, the screen luminance of the surface light source device 23 that illuminates the main liquid crystal panel 22 and the sub liquid crystal panel 24 will be considered based on these actions. 20A to 20E are diagrams showing the light amount of each part, and the horizontal axis represents the distance from the end of the main liquid crystal panel 22. Now, when the amount of light emitted from the surface light source device 23 and incident on the polarization matching plate 27 (light including P-polarized light and S-polarized light) is expressed as 100% (FIG. 20A), the polarization matching plate 27 The reflected P-polarized light has a light quantity of 50% (FIG. 20B), and the S-polarized light transmitted through the polarization matching plate 27 also has a light quantity of 50% (FIG. 20C). The S-polarized light transmitted through the polarization matching plate 27 is absorbed by the frame member 28 and transmitted through the sub liquid crystal panel 24. Therefore, there is no light returning to the main liquid crystal panel 22 side. % Is illuminated (FIG. 20 (d)). The sub liquid crystal panel 24 is also illuminated uniformly with 50% light (FIG. 20E).

  As a result, as shown in FIG. 21, the luminance on the upper surface side of the surface light source device 23 is 50% over the entire main liquid crystal panel 22, and the luminance on the lower surface side of the surface light source device 23 is also 50% in the region of the sub liquid crystal panel 24. The entire main liquid crystal panel 22 and the entire sub liquid crystal panel 24 are illuminated with equal brightness. Therefore, an image with uniform brightness is generated on the main liquid crystal panel 22 and the sub liquid crystal panel 24 which is turned on, and the image on the main liquid crystal panel 22 side is also the image on the sub liquid crystal panel 24 side. Are equal in brightness, and optimum characteristics can be obtained. In particular, the screen brightness of the main liquid crystal panel 22 in the region facing the frame member 28 and the screen brightness of the main liquid crystal panel 22 in the region facing the sub liquid crystal panel 24 are equal, and the overall brightness of the main liquid crystal panel 22 is uniform. Become. When the reflectance of light at the frame member 28 is slightly larger than 0% or when there is reflection by the surface of the sub liquid crystal panel 24, it corresponds to the sub liquid crystal panel 24 as shown by a two-dot chain line in FIG. Although an error in luminance on the main liquid crystal panel 22 side is generated between the region corresponding to the frame member 28 and the region corresponding to the frame member 28, the difference in screen luminance in the main liquid crystal panel 22 is smaller than that in the past. In particular, even when the screen of the main liquid crystal panel 22 is viewed from an oblique direction, the edge of the opening 51 of the frame member 28 is not seen.

  22 and 23 show a comparative example with the embodiment of the present invention. In Comparative Example 1 shown in FIG. 22B, the surface of the frame member 28 is made highly reflective. For example, the frame member 28 is manufactured by a white reflector (for example, Toray Industries, Inc. Lumirror, E-20). For example, if the reflectance of the frame member of Comparative Example 1 is 100%, all the S-polarized light transmitted through the polarization matching plate 27 is reflected by the frame member 28, so that the polarization matching plate 27 of the main liquid crystal panel 22 In the facing region, the amount of light is 100% when combined with the P-polarized light reflected by the polarization matching plate 27. Since only the P-polarized light returns in the region facing the opening 51 of the frame member 28, the region facing the opening 51 of the frame member 28 and the region facing the sub liquid crystal panel 24 as shown in FIG. The difference in screen brightness between

  Further, Comparative Example 2 shown in FIG. 23 (b) has the same structure as the conventional example shown in FIGS. 2 (a) and 2 (b), and has a low reflectivity frame member 17 (for example, Lumirror made by Toray Industries, Inc.). , X-30, etc.). For example, if the reflectance of the frame member 17 is 0%, light incident on the frame member 17 out of the light emitted downward from the backlight 13 is not reflected at all, so that the frame member 17 on the main liquid crystal panel 14 side In the facing area, the luminance of the backlight 13 is 0%. In the area facing the sub liquid crystal panel 15, the P-polarized light returns and the light intensity becomes 50%. Therefore, as shown in FIG. 23A, the area facing the sub liquid crystal panel 15 and the area facing the frame member 28. The difference in screen brightness increases between

  FIG. 24 shows the result of measuring the intensity of light emitted to the main liquid crystal panel side for each of the double-sided image display devices of the first example of the present invention, the conventional example shown in FIG. 2 and the comparative example 1 shown in FIG. Represents. In addition, as the frame member 17 of the conventional example, Lumirror, E-20 manufactured by Toray Industries, Inc. was used. The double-sided image display device used here includes a main liquid crystal panel having a width of 40 mm and a sub liquid crystal panel having a width of 26 mm. The horizontal axis in FIG. 24 represents the distance from the end of the main liquid crystal panel, and the vertical axis Represents the screen brightness in the main liquid crystal panel. As can be seen from FIG. 24, in the conventional example and the comparative example 1, the difference in screen luminance between the frame member and the sub liquid crystal panel is very large. On the other hand, in Example 1, the light intensity is almost uniform.

The data shown in FIG. 24 is obtained as follows. A digital camera is arranged in a direction inclined by 30 ° from the normal direction of the main liquid crystal panel, and an image of the main liquid crystal panel is taken by the digital camera. Next, the photographed color image is separated into three primary color images of red, green and blue. Since each monochrome image is represented by an intensity of 256 gradations (0 to 255 gradations), the gradation degree for a red image of a certain pixel is R, the gradation degree for a green image is G, and the gradation degree for a blue image. Is B, the intensity (gradation) of the pixel is
α × R + β × G + γ × B
It becomes. here,
α = 0.299
β = 0.587
γ = 0.114
(Α + β + γ = 1).

  Further, when the main liquid crystal panel 22 is viewed from an oblique direction, the edge of the opening 51 appears to appear as a shadow on the main liquid crystal panel 22 when viewed carefully in the conventional example and the first and second comparative examples. Then, the edge of the opening 51 of the frame member 28 was not visible.

  In the configuration as in this embodiment, when an ideal polarization matching plate 27 is used, when light is displayed on the main liquid crystal panel 22 side, external light is transmitted from the sub liquid crystal panel 24 on the back surface. Even if it enters, it should not be reflected on the main liquid crystal panel 22 side, but in reality, when external light enters from the sub liquid crystal panel 24, the shadow of the edge of the opening 51 of the frame member 28 on the main liquid crystal panel 22 side. There is a risk of reflection. For this reason, in this embodiment, the sub liquid crystal panel 24 is a normally black or low transmittance panel so that external light does not enter from the sub liquid crystal panel 24 when the sub liquid crystal panel 24 is off.

  FIG. 25 is a sectional view showing a double-sided image display device 92 according to the second embodiment of the present invention. In the second embodiment, the polarization matching plate 27 is disposed not between the light guide plate 26 and the sub liquid crystal panel 24 but between the light guide plate 26 and the main liquid crystal panel 22. The polarization matching plate 27 is arranged to transmit P-polarized light and reflect S-polarized light. The frame member 28 disposed between the light guide plate 26 and the sub liquid crystal panel 24 has a low reflectance at least on the upper surface, as in the first embodiment. The light guide plate 26 has a deflection pattern 43 formed on the lower surface so that light 48 can be emitted to the upper surface side where the polarization matching plate 27 is provided.

  Even with such a configuration, the same incident light intensity can be obtained in both the main liquid crystal panel 22 and the sub liquid crystal panel 24 in the same manner as shown in FIG. 21 of the first embodiment. Therefore, in the main liquid crystal panel 22, the luminance difference between the screen luminance in the region facing the sub liquid crystal panel 24 and the screen luminance in the region facing the frame member 28 can be reduced. However, in the actual measurement value, as shown in FIG. 24, the luminance difference between the screen luminance of the main liquid crystal panel 22 in the region facing the sub liquid crystal panel 24 and the screen luminance of the main liquid crystal panel 22 in the region facing the frame member 28 is Compared to Example 1, the brightness difference is smaller than that of the conventional example or Comparative Example 1.

  FIG. 26 is a cross-sectional view showing a double-sided image display device 93 according to Embodiment 3 of the present invention. In the third embodiment, the polarization matching plate 27 is disposed between the light guide plate 26 and the sub liquid crystal panel 24, and the polarization matching plate 27 is also disposed between the light guide plate 26 and the main liquid crystal panel 22. Both polarization matching plates 27 are arranged so that the directions of polarization transmission axes are orthogonal to each other, and the polarization matching plate 27 between the light guide plate 26 and the main liquid crystal panel 22 transmits P-polarized light and S-polarized light. The polarization matching plate 27 between the light guide plate 26 and the sub liquid crystal panel 24 is arranged to reflect P-polarized light and transmit S-polarized light. . Further, the frame member 28 disposed between the light guide plate 26 and the sub liquid crystal panel 24 has a low reflectance at least on the upper surface, as in the first embodiment. In FIG. 26, the deflection patterns 43 are formed on the upper and lower surfaces of the light guide plate 26 so that the light 48 can be emitted to both the upper and lower surfaces of the polarization matching plates 27.

  Even with such a configuration, the same incident light intensity can be obtained in both the main liquid crystal panel 22 and the sub liquid crystal panel 24 in the same manner as shown in FIG. 21 of the first embodiment. Therefore, in the main liquid crystal panel 22, the luminance difference between the screen luminance in the region facing the sub liquid crystal panel 24 and the screen luminance in the region facing the frame member 28 can be reduced.

  When the deflection patterns 43 are formed on both surfaces of the light guide plate 26, the pattern density of the sum of the deflection patterns 43 on both surfaces may be gradually increased as the distance from the point light source 25 increases. For example, the combination of the front and back deflection patterns 43 may satisfy the conditions described with reference to FIGS. Therefore, the deflection pattern 43 may be formed only on part of the front and back surfaces of the light guide plate 26 as long as these conditions are satisfied. For example, in the modification shown in FIG. 27, the deflection pattern 43 is formed only in the region facing the sub liquid crystal panel 24 on the upper surface of the light guide plate 26.

  In the above-described embodiment, the case where a polarization matching plate that reflects light in one polarization direction and transmits light in the other polarization direction is used as the semi-transmission semi-reflection plate. For example, a half mirror or a polarizing plate may be used in place of the polarization matching plate. The half mirror preferably has a transmittance of 50% and a reflectance of 50%, but any mirror having a reflectance of 30 to 70% can be used. Further, if the transmissivity of the transflective plate is changed, the ratio between the brightness on the main liquid crystal panel 22 side and the brightness on the sub liquid crystal panel 24 side while keeping the brightness of the main liquid crystal panel 22 uniform as a whole. Can be changed. The polarizing plate theoretically transmits half of the light and absorbs the remaining light and does not reflect it, so it cannot be said to be a semi-transmissive semi-reflective plate. Since light is reflected, a polarizing plate can be used as a semi-transmissive / semi-reflective plate if the ratio of reflecting light is large to some extent.

  As a modification of the third embodiment, as shown in FIG. 28, the deflection pattern 43 is formed on both surfaces of the light guide plate 26, and the polarization matching plate 27 is disposed so as to face either one of the light guide plates 26. You may let them.

  FIG. 29 is a cross-sectional view showing a double-sided image display device 94 according to Embodiment 4 of the present invention. The double-sided image display device 94 according to the fourth embodiment is a double-sided image display device in which a deflection pattern 43 is provided only on the upper surface side of the light guide plate 26 and light is emitted from the lower surface side of the light guide plate 26. A polarization matching plate 27 is disposed between the members 28, and a polarization matching plate 27 is also disposed between the light guide plate 26 and the main liquid crystal panel 22. The polarization matching plate 27 on the upper surface side is arranged in a direction that allows the P-polarized light reflected by the polarization matching plate 27 on the lower surface side to pass therethrough.

  When the S-polarized light that has passed through the polarization matching plate 27 on the lower surface side is reflected by the upper surface of the sub liquid crystal panel 24 or the surface of the frame member 28 as indicated by the broken line in FIG. Without the plate 27, the reflected S-polarized light reaches the main liquid crystal panel 22. Therefore, a difference in screen luminance may occur in the main liquid crystal panel 22 due to a difference in reflectance between the frame member 28 and the reflectance of the sub liquid crystal panel 24.

  On the other hand, in the case of Example 4, even if the S-polarized light transmitted through the polarization matching plate 27 on the lower surface side is partially reflected by the frame member 28 or the sub liquid crystal panel 24, the reflected S-polarized light is reflected. Cannot pass through the polarization matching plate 27 on the upper surface side and does not reach the main liquid crystal panel 22. Therefore, the light reflected by the frame member 28 and the sub liquid crystal panel 24 does not reach the main liquid crystal panel 22, so that the sub liquid crystal panel 24 faces the sub liquid crystal panel 24 due to the difference in reflectance between the sub liquid crystal panel 24 and the frame member 28. The brightness difference between the screen brightness of the main liquid crystal panel 22 in the area to be screened and the screen brightness of the main liquid crystal panel 22 in the area facing the frame member 28 can be reduced.

  In the double-sided image display device 94 according to the fourth embodiment, the polarization matching plate 27 on the upper surface side only needs to transmit P-polarized light. Therefore, a polarizing plate is used instead of the polarization matching plate 27 on the upper surface side of the light guide plate 26. (It may be one that hardly reflects light.).

  FIG. 30 is a sectional view showing a double-sided image display device 95 according to the fifth embodiment of the present invention. The double-sided image display device 95 according to the fifth embodiment is the double-sided image display device in which the deflection pattern 43 is provided only on the lower surface side of the light guide plate 26 and light is emitted from the upper surface side of the light guide plate 26. A polarization matching plate 27 is disposed between the liquid crystal panels 22, and a polarization matching plate 27 is also disposed between the light guide plate 26 and the frame member 28. The polarization matching plate 27 on the lower surface side is arranged in a direction that allows the S-polarized light reflected by the polarization matching plate 27 on the upper surface side to pass therethrough.

  After the S-polarized light reflected by the polarization matching plate 27 on the upper surface side passes through the light guide plate 26, the light 52 is shown on the upper surface of the sub liquid crystal panel 24 and the surface of the frame member 28 as shown by the broken line in FIG. 30. When reflected, the polarization direction of the reflected light turns or becomes random. Therefore, if there is no polarization matching plate 27 on the lower surface side, part of the reflected light (P-polarized light) passes through the polarization matching plate 27 on the upper surface side and reaches the main liquid crystal panel 22. Therefore, a difference in screen brightness may appear between the region facing the frame member 28 and the region facing the sub liquid crystal panel 24 due to the difference in reflectance between the frame member 28 and the reflectance of the sub liquid crystal panel 24.

  In the case of the fifth embodiment, since the polarization matching plate 27 is also disposed on the lower surface side, only the S-polarized light is transmitted through the polarization matching plate 27 on the lower surface side of the light reflected by the frame member 28 and the sub liquid crystal panel 24. Then, it is blocked by the polarization matching plate 27 on the upper surface side. Therefore, the light reflected by the frame member 28 and the sub liquid crystal panel 24 does not reach the sub liquid crystal panel 24, and the screen luminance between the region facing the frame member 28 and the region facing the sub liquid crystal panel 24 is reduced. The difference can be reduced.

  In the fifth embodiment, since the polarization matching plate 27 on the lower surface side only needs to transmit S-polarized light, the polarizing plate (almost no light is reflected on the upper surface side of the light guide plate 26 instead of the polarization matching plate 27). Can also be used).

  Note that when Example 1, Example 2, Example 3, Example 4, and Example 5 are compared, the luminance of the main liquid crystal panel 22 in the region corresponding to the sub liquid crystal panel 24 and the region corresponding to the frame member 28 are compared. The difference in luminance of the main liquid crystal panel 22 is the smallest, and the shadow of the edge of the opening 51 of the frame member 28 is the least visible. The polarization matching plate 27 (in the fourth and fifth embodiments, one polarization matching plate is a polarizing plate). In the third, fourth, and fifth embodiments, the light guide plate 26 is disposed on both surfaces. Next, the difference between the luminance of the main liquid crystal panel 22 in the region corresponding to the sub liquid crystal panel 24 and the luminance of the main liquid crystal panel 22 in the region corresponding to the frame member 28 is small, and the shadow of the edge of the opening 51 of the frame member 28 is difficult to see. This is Example 1. In comparison, Example 2 was the least effective.

  When the polarization matching plates 27 are arranged on both surfaces of the light guide plate 26 as in the third to fifth embodiments, the sub liquid crystal panel 24 can also use external light as illumination light as shown in FIG. It becomes possible.

  FIG. 32 is a schematic sectional view of a double-sided image display device 96 according to Embodiment 6 of the present invention. In the sixth embodiment, the polarization matching plate 27 is disposed on the upper surface side of the light guide plate 26 having the deflection pattern 43 formed on the lower surface so as to transmit, for example, P-polarized light. The polarization matching plate 27 is disposed so as to transmit light having the same polarization direction as that of the side polarization matching plate 27. That is, the polarization transmission axis of the polarization matching plate 27 on the upper surface side is parallel to the polarization transmission axis of the polarization matching plate 27 on the lower surface side. Further, between the upper surface of the light guide plate 26 and the polarization matching plate 27 on the upper surface side, a retardation plate 53 such as a half-wave plate that rotates the polarization direction of linearly polarized light by 90 ° with incident light and outgoing light. Is arranged.

  Thus, in this double-sided image display device 96, when the light 48 emitted from the upper surface of the light guide plate 26 enters the polarization matching plate 27 on the upper surface side, the P-polarized light is transmitted through the polarization matching plate 27 on the upper surface side. The main liquid crystal panel 22 is illuminated. Further, the S-polarized light reflected by the polarization matching plate 27 on the upper surface side is converted to P-polarized light by passing through the phase difference plate 53 and passes through the polarization matching plate 27 on the lower surface side to reach the sub liquid crystal panel 24. To do.

  According to such an embodiment, since light having the same polarization direction is incident on both the main liquid crystal panel 22 and the sub liquid crystal panel 24, characteristics with respect to the polarization directions of the main liquid crystal panel 22 and the sub liquid crystal panel 24, that is, the main liquid crystal panel. The viewing area in the vertical direction and the horizontal direction when viewing 22 (viewing characteristics) is the same as the viewing area in the vertical direction and horizontal direction when viewing the sub liquid crystal panel 24, and the visibility is good. It becomes easier to use.

  In FIG. 32, the phase difference plate 53 is disposed between the upper surface of the light guide plate 26 and the polarization matching plate 27 on the upper surface side. However, the phase difference plate 53 is disposed between the main liquid crystal panel 22 and the sub liquid crystal panel 24. If so, it may be placed anywhere. However, if it is outside between the upper and lower polarization matching plates 27, the directions of the polarization transmission axes of the upper and lower polarization matching plates 27 need to be orthogonal. Further, in the sixth embodiment, in the same member arrangement as in the fifth embodiment, the direction of the polarization transmission axis of the upper and lower polarization matching plates 27 is aligned by using a phase difference plate, but as in the first to fourth embodiments. In such a structure, the retardation plate 53 may be used.

  FIG. 33 is an exploded perspective view showing a double-sided image display device 97 according to Embodiment 7 of the present invention. Since parts other than the surface light source device 23 are the same as those in the first embodiment, the structure of the surface light source device 23 will be described. The surface light source device 23 includes a transparent light guide plate 26, a light emitting unit 54 disposed opposite to the light incident surface of the light guide plate 26, a polarization matching plate 27, and a frame member 28. The light guide plate 26 is formed in a rectangular flat plate shape using a transparent resin having a high refractive index (for example, polycarbonate resin or methacrylic resin), and a plurality of deflections extending in the width direction of the light guide plate 26 on the upper surface thereof. Patterns 43 are formed in parallel to each other. The deflection pattern 43 is formed by recessing the upper surface of the light guide plate 26 and has a substantially right-angled cross section. The polarization patterns 43 are arranged in parallel with the light incident surface with a space between each other, and the distance between the polarization patterns 43 becomes shorter as the distance from the light incident surface increases.

  The light emitting unit 54 is disposed so as to face a wedge-shaped light guide (hereinafter referred to as a wedge-shaped light guide) 55 formed of a transparent resin having a high refractive index and a side end surface of the wedge-shaped light guide 55. It comprises a point light source 25, a regular reflection plate 56 disposed on the back surface of the wedge-shaped light guide 55, and a prism sheet 57 disposed on the front surface of the wedge-shaped light guide 55. Here, the point light source 25 is one or a plurality of LEDs sealed in a transparent resin, the transparent resin is covered with a white resin except for the front surface, and the light emitted from the light emitting diode is directly or After being reflected by the inner surface of the white resin, it is efficiently emitted forward.

  Light (Lambertian light) emitted from the point light source 25 enters the wedge-shaped light guide 55 from the side end face of the wedge-shaped light guide 55. As shown in FIG. 34, the light incident on the wedge-shaped light guide 55 is repeatedly reflected on the front surface (light emitting surface) 55a and the back surface of the wedge-shaped light guide 55, whereby the inside of the wedge-shaped light guide 55 is obtained. , The angle of incidence on the front surface 55a decreases each time it is reflected by the back surface of the wedge-shaped light guide 55, and the angle of incidence on the front surface 55a of the wedge-shaped light guide 55 becomes smaller than the critical angle of total reflection. The light is emitted from the front surface 55a of the wedge-shaped light guide 55 to the outside. Further, as indicated by a broken line in FIG. 34, the light emitted to the outside from the back surface of the wedge-shaped light guide 55 is reflected by the specular reflection plate 56 and returns to the wedge-shaped light guide 55 again, and the wedge-shaped light guide. The light is emitted from the front surface 55a of the body 55. In this way, the light emitted from the front surface 55a of the wedge-shaped light guide 55 is aligned in a direction substantially parallel to the front surface 55a of the wedge-shaped light guide 55.

  The prism sheet 57 disposed on the front surface 55a of the wedge-shaped light guide 55 is also formed of a transparent resin having a high refractive index (for example, a transparent resin having a refractive index of 1.59). A prism 57a is arranged. Each prism 57a has a triangular cross section with an apex angle of 40 °, and extends uniformly in the vertical direction (thickness direction of the light guide plate 26). Thus, the light emitted from the front surface 55a of the wedge-shaped light guide 55 as described above is refracted through the prism 57a, and is deflected in a direction substantially perpendicular to the prism sheet 57. The light is incident almost vertically into the light guide plate 26 from the light incident surface. Therefore, according to the light emitting unit 54, the light emitted from the point light source 25 can be emitted while being spread over almost the entire length of the prism sheet 57, and the point light source 25 can be converted into a so-called linear light source.

  Note that part of the light transmitted through the prism sheet 57 may become stray light due to molding errors such as roundness of the apex of the prism cross section of the prism sheet 57 and Fresnel reflection. Therefore, at least half or more of the light emitted from the point light source 25 is deflected by the prism sheet 57 and is incident on the light guide plate 26 at a desired angle (in this embodiment, a direction perpendicular to the light incident surface 52a). Then, the ratio of the light emitted from the front surface 55a of the wedge-shaped light guide 55 almost in parallel with the front surface 55a is preferably 2/3 or more with respect to the total emitted light from the point light source 25.

  FIG. 35 is an exploded perspective view showing a double-sided image display device 98 according to an eighth embodiment of the present invention, and FIG. 36 is a schematic sectional view thereof. Since this double-sided image display device 98 is also the same as that of the first embodiment except for the surface light source device 23, the structure of the surface light source device 23 will be described. The surface light source device 23 mainly includes a light guide plate 26, a point light source 25, a diffusion prism sheet 59, a polarization matching plate 27, and a frame member 28. The light guide plate 26 is formed in a square flat plate shape using a transparent resin such as polycarbonate resin or methacrylic resin, and a polarization pattern 43 is provided on the upper surface. A light incident surface is formed at one corner portion of the light guide plate 26 by cutting the corner portion obliquely in plan view. A point light source 25 is disposed at a position facing the light incident surface of the light guide plate 26.

  An arrangement of the polarization patterns 43 formed on the light guide plate 26 is shown in FIG. In the description of the eighth embodiment, the z axis is defined in a direction perpendicular to the surface of the light guide plate 26, and the x axis and the y axis are defined in directions parallel to two sides adjacent to the light incident surface. Further, when considering light propagating in an arbitrary direction or considering reflection at an arbitrary polarization pattern 43, the light is propagated in a direction parallel to the surface of the light guide plate 26 within a plane perpendicular to the light guide plate 26. The r-axis is determined, or the r-axis is determined in a direction parallel to the surface of the light guide plate 26 in a plane perpendicular to the light guide plate 26 including the direction connecting the point light source 25 and the polarization pattern 43. Further, an angle formed by the x axis and the r axis is θ.

  The polarization pattern 43 formed on the upper surface of the light guide plate 26 is arranged on a concentric arc centered on the point light source 25 (particularly, the internal LED), and each polarization pattern 43 is arranged on the light guide plate 26. Is formed in a straight line by recessing the upper surface of the asymmetrical triangular section. In the polarization pattern 43 having a triangular cross section, the slope closer to the point light source 25, that is, the tilt angle of the deflection tilt surface 46 is preferably within 20 °. Each polarization pattern 43 extends linearly along the circumferential direction of the arc centered on the point light source 25, and the direction of the normal line standing on the deflection inclined surface 46 of each polarization pattern 43 is in plan view. (Viewed from the z-axis direction) is parallel to the direction connecting the point light source 25 and the polarization pattern 43 (r-axis direction). The polarization pattern 43 is formed so that the pattern density gradually increases as the distance from the point light source 25 increases. However, in the vicinity of the point light source 25, the pattern density of the polarization pattern 43 may be substantially uniform. Note that an optical element (diffuser) 60 made of a lens, a prism, or the like is formed on the light incident surface of the light guide plate 26 in order to control the alignment pattern of light entering the light guide plate 26 from the point light source 25. Good.

  FIG. 38 is a perspective view showing the outline of the polarization pattern 43. The slope of the polarization pattern 43 facing the point light source 25 side, that is, the front edge (edge on the point light source 25 side) of the deflection inclined surface 46 is longer than the rear edge (edge far from the point light source 25). . In the illustrated example, the deflection inclined surface 46 of the polarization pattern 43 has a trapezoidal shape, and the re-incident surface 47 on the back surface has a rectangular shape. Therefore, when the polarization pattern 43 is viewed from the point light source 25 side, the left and right side surfaces of the polarization pattern 43 are hidden behind the deflection inclined surface 46 and are not visible from the point light source 25 side.

  A diffusion prism sheet 59 shown in FIG. 36 is obtained by forming a transparent uneven diffusion plate 62 on the lower surface of a transparent plastic sheet 61 and forming a transparent prism sheet 63 on the upper surface of the plastic sheet 61. The uneven diffusion plate 62 and the prism sheet 63 are prepared by dropping an ultraviolet curable resin on the surface of the plastic sheet 61 and pressing the ultraviolet curable resin with a stamper to spread the ultraviolet curable resin between the stamper and the plastic sheet 61. It is formed by irradiating an ultraviolet curable resin with ultraviolet rays and curing it (Photo Polymerization method).

  39A, 39B and 39C are explanatory views for explaining the structure of the uneven diffusion plate 62. FIG. As shown in FIG. 39 (a), the uneven diffusion plate 62 is a pattern in which repeated patterns 64 are periodically arranged in the horizontal direction with almost no gap. As shown in FIG. 39 (b), the repetitive pattern 64 is formed by randomly arranging conical convex portions 65 having blunt apexes as shown in FIG. 39 (c) with almost no gap. The vertical and horizontal widths H and W of one repeating pattern 64 are larger than the pixel size of the sub liquid crystal panel 24 in order to prevent moire fringes, and both are preferably 100 μm or more and 1 mm or less. . Further, it is desirable that the convex portions 65 constituting the repetitive pattern 64 have irregular dimensions and have an outer diameter D of 5 μm or more and 30 μm or less (particularly, about 10 μm is preferable).

  Since the uneven diffusion plate 62 has special diffusion characteristics, the uneven shape of the pattern must be accurately controlled. In that case, if one uneven pattern is arranged periodically, all the uneven patterns have the same shape, so that all the uneven patterns can be produced in the same way and an accurate uneven shape can be formed. However, in such a method, moire fringes are generated on the screen of the liquid crystal display device, and pixels are easily noticeable. On the other hand, if the concave / convex pattern is to be arranged at random, the shape and size of the concave / convex pattern must be changed one by one, making it difficult to produce an accurate shape. In addition, the characteristics of the uneven diffusion plate may change depending on the location. Therefore, in the uneven diffusion plate 62 of the present invention, a convex pattern 65 having a random shape and size is randomly arranged to form a repetitive pattern 64, and the repetitive pattern 64 is periodically arranged, so that moire fringes and the like are arranged. The production of the pattern of the uneven diffusion plate 62 is facilitated while suppressing the generation.

  FIG. 40 is a perspective view showing the structure of the prism sheet 63. The prism sheet 63 is formed by concentrically arranging arc-shaped prisms 66 (in FIG. 40, the arc-shaped prism 66 is exaggerated and greatly drawn) having a triangular shape with an asymmetrical cross section. 66 is formed in an arc shape around the position where the LED of the point light source 25 is disposed.

  Note that the uneven diffusion plate 62 and the prism sheet 63 do not have to be formed integrally as in the eighth embodiment, and may be formed separately and arranged with a gap therebetween. However, as in this embodiment, the plastic sheet 61 formed integrally has the advantages of reducing the overall thickness and reducing the cost.

  Next, the behavior of the light 48 in the double-sided image display device 98 will be described with reference to FIGS. 41, 42 (a) and 42 (b). 41 is a diagram illustrating the behavior of light when viewed from obliquely above the light guide plate 26, FIG. 42A is a diagram illustrating the behavior of light in the cross section (zr plane) of the light guide plate 26, and FIG. ) Is an enlarged view of a portion X in FIG. The light 48 emitted from the point light source 25 enters the light guide plate 26 from the light incident surface. The light 48 incident on the light guide plate 26 from the light incident surface spreads radially in the light guide plate 26. At this time, the light amount of each direction of the light 48 spreading in the light guide plate 26 is a sector shape of the light guide plate 26 in each direction. It is desirable to design the optical element 60 provided on the light incident surface so as to be proportional to the area. Specifically, as shown in FIG. 43, the amount of light emitted from the side of the light guide plate 26 (side in the x-axis direction) within the range of the spread Δθ located in any direction of θ is within this range. It is desirable to be proportional to the area of the light guide plate included in Δθ (the area of the hatched area in FIG. 43), thereby making the luminance distribution of the double-sided image display device 98 uniform in each direction. Can do.

  The light 48 incident on the light guide plate 26 travels in the direction away from the point light source 25 (r-axis direction) while repeating total reflection on the upper and lower surfaces of the light guide plate 26. Each time the light 48 incident on the upper surface of the light guide plate 26 is reflected by the deflection inclined surface 46 of the polarization pattern 43 having a triangular cross section, the incident angle β to the lower surface (light emitting surface 44) of the light guide plate 26 becomes smaller. The light 48 incident on the light emitting surface 44 with an incident angle β smaller than the critical angle of total reflection is transmitted through the light emitting surface 44 and emitted to the outside of the light guide plate 26 along the light emitting surface 44. Since any polarization pattern 43 is arranged so as to be orthogonal to the direction connecting the point light source 25 and each polarization pattern 43, even if the light 48 propagating in the light guide plate 26 is diffused by the polarization pattern 43, The light 48 is diffused in a plane (zr plane) perpendicular to the light exit surface 44 including the direction connecting the point light source 25 and the polarization pattern 43, but in a plane (xy plane) parallel to the light exit surface 44. Then go straight without spreading.

  As a result, the range of light emitted from the light exit surface 44 of the light guide plate 26 is considerably limited. If the inclination angle γ of the polarization pattern 43 having a triangular cross section is 12 °, for example, the light exit surface The light emission direction φ in the zr plane perpendicular to 44 is about 45 ° to 90 °.

  As described above, the light emitted from the light emitting surface 44 of the light guide plate 26 does not spread in the θ direction, and the directivity angle Δφ in the φ direction is limited, so that the light has a fairly narrow directivity. Light having a small spread and strong directivity emitted along the light exit surface 44 is reflected by the inclined surface of the prism sheet 63 of the diffusion prism sheet 59 as shown in FIG. The light is bent in a direction perpendicular to the surface 44 and then diffused by the uneven diffusion plate 62 of the diffusion prism sheet 59, and the directivity in both directions is adjusted by expanding the directivity in the θ direction.

  FIG. 44 is a diagram showing the definition of parameters representing the directivity characteristics of light emitted from the light exit surface 44 of the light guide plate 26. As shown in FIG. 44, the emission angle in a plane that includes the direction connecting the point light source 25 and the deflection pattern 43 (r-axis direction) and is perpendicular to the light emission surface 44 is φ, and is perpendicular to the plane and the light emission surface 44. Let the outgoing angle in the plane be ω.

  When light is emitted in the vertical direction from the light emitting surface 44 by being reflected by the deflection pattern 43 as in the first embodiment, the light spread in the φ direction is larger than the light spread in the ω direction, and If the position is different in the θ direction, the direction in which the light spreads is different. For this reason, when the surface light source device 23 is viewed obliquely from above, a radial luminance unevenness R as shown in FIG.

  The prism sheet 57 formed on the diffusion prism sheet 59 is bent by refracting or totally reflecting the light 48 emitted in a direction substantially along the light emitting surface 44 of the light guide plate 26 by the arc-shaped prism 66. The light 48 is emitted substantially vertically downward. The light 48 emitted from the light exit surface 44 has a directivity angle Δφ in the φ direction that is considerably larger than the spread (directivity angle) in the ω direction. The directivity angle Δφ at can be reduced. For example, after passing through the prism sheet 57, the angle (half width) at which the light intensity becomes half of the peak value is about 5 ° in the ω direction, and is about 15 ° in the φ direction. By reducing the difference in directivity angle between the φ direction and the ω direction in this way, an effect of reducing radial luminance unevenness generated in the surface light source device 23 can be obtained.

  However, in practice, the prism sheet 57 alone cannot sufficiently reduce the difference between the directivity in the ω direction and the directivity in the φ direction (the full width at half maximum in the ω direction is 10 °, and the full width at half maximum in the φ direction). Is 30 °, so there is a difference of 20 ° in the full width at half maximum.) Even though the radial luminance unevenness is reduced, the luminance unevenness still appears strong. Therefore, it is necessary to reduce the difference between the directivity angle in the ω direction and the directivity angle in the φ direction. For this purpose, it is necessary to further spread light in the ω direction.

  Next, the function and effect of the uneven diffusion plate 62 used in the surface light source device 23 of the present invention will be described. FIG. 46 shows the directivity when parallel light is vertically incident on the uneven diffusion plate 62 as shown in FIG. When this uneven diffusion plate 62 is placed on the prism sheet 63, the directivities in the θ direction and the φ direction are as shown in FIG. That is, the full width at half maximum Δθ and Δφ in the θ direction and the φ direction are respectively Δθ = 20 ° Δφ = 29 °, and the difference is Δφ−Δθ = 9 °, which is the full width at half maximum as compared with the case of the prism sheet 63 alone. The difference is reduced by 58%. For this reason, radial luminance unevenness can be considerably reduced. Further, the amount of light included in the full width at half maximum Δθ = 20 ° in the narrowest direction is about 30% of the total amount of light, and the useless light is reduced to 70%. For this reason, the luminance in the vertical direction is improved by about 20% as compared with a general diffusion plate, and the luminance reduction rate at a position θ = 5 ° away from the vertical direction is less than 10%. The difficulty of seeing due to unevenness has been almost eliminated.

  FIG. 48 is a schematic sectional view showing a double-sided image display device 99 according to the ninth embodiment of the present invention. In this embodiment, a polarization matching plate 27 is bonded to the upper surface of the sub liquid crystal panel 24, and the reflected light on the upper surface of the frame member 28 is reflected by the polarization matching plate 27 (P-polarized light in the figure). It is equal to the reflectance.

  As a method of making the reflectance of the surface of the frame member 28 equal to the reflectance of the polarization matching plate 27, the polarization matching plate 27 is bonded to the surface of the frame member 28 (this method is a single polarization matching plate 27). In addition to the above method, a reflective plate or a diffuser plate whose reflectance is controlled is applied to the surface of the frame member 28. There are a method of attaching, a method of controlling the surface reflectance of the frame member 28 by surface processing or surface treatment, and the like.

  Also by such a method, the intensity of light reflected from the main liquid crystal panel 22 side and illuminating the main liquid crystal panel 22 from the back side can be made uniform, so that the screen brightness of the main liquid crystal panel 22 is uniform. Thus, the shadow of the frame member 28 can be prevented from being reflected on the screen of the main liquid crystal panel 22.

  A curve indicated by a broken line in FIG. 24 represents a screen luminance distribution of the main liquid crystal panel 22 in the ninth embodiment. This shows a case where the frame member 28 has a reflectance that is not sufficiently small. In this case as well, the main liquid crystal panel 22 in the region facing the frame member 28 and the region facing the sub liquid crystal panel 24 is used. The screen brightness difference is sufficiently small.

(Portable phone)
49 and 50 are perspective views showing the foldable portable telephone 101. FIG. 49 shows a perspective view in a folded and closed state, and FIG. 50 shows a perspective view in an opened state. The portable telephone 101 includes a main body 104 having a circuit board, a battery, and the like and provided with switches, a numeric keypad 103, and the like on the surface, and a cover portion in which the double-sided image display device 102 and the antenna 107 according to the present invention are incorporated. 105 is rotatably connected by a hinge part 106. As shown in FIG. 50, the main liquid crystal panel 22 of the double-sided image display device 102 is disposed on the inner surface of the cover unit 105 as a liquid crystal display. The sub liquid crystal panel 24 of the double-sided image display device 102 is exposed on the outer surface of the cover unit 105 as shown in FIG.

  According to such a portable telephone 104, when the main liquid crystal panel 22 is observed with the cover portion 105 and the main body portion 104 opened, the brightness of the main liquid crystal panel 22 becomes uniform and the inner frame member 28 can be seen through. It is difficult to do.

It is a schematic sectional drawing which shows the structure of the double-sided image display apparatus by a prior art example. It is a schematic sectional drawing which shows the structure of the double-sided image display apparatus by another prior art example, and the behavior of light. It is a figure showing the screen luminance distribution in the main liquid crystal panel in the double-sided image display apparatus same as the above. It is a figure which shows the relationship between the direction which looks at a main liquid crystal panel, and the brightness | luminance of a screen. It is a disassembled perspective view which shows the structure of the double-sided image display apparatus by Example 1 of this invention. It is a schematic sectional drawing of the double-sided image display apparatus same as the above. 2 is a plan view of a light guide plate used in Example 1. FIG. 2 is a cross-sectional view showing the structure of a point light source used in Example 1. FIG. It is a figure which shows arrangement | positioning of the deflection pattern currently formed in the surface light emission area | region of the light-guide plate surface. (A) and (b) are the top view and enlarged sectional drawing which show the shape of a deflection pattern same as the above. (A) (b) is a figure which shows the behavior of the light which injected into the deflection pattern. (A) is a plan view of a light guide plate provided with a deflection pattern, (b) is an enlarged view of a portion of (a), (c) is an enlarged view of a portion of (a), and (d) is an enlarged view of (a). FIG. It is a figure which shows the relationship between the distance from a point light source, and the pattern density of a deflection pattern in the light guide plate same as the above. It is a figure which shows the relationship between the distance from a point light source, and the pattern length of a deflection pattern in the light-guide plate same as the above. It is a figure which shows the relationship between the distance from a point light source, and the pattern number density (pattern number / area) of a deflection pattern in a light-guide plate same as the above. It is the schematic which shows the structure and its effect | action for sending more light to the corner part of a light-projection surface in the surface light source device of this invention. It is a figure explaining the effect of the double-sided image display apparatus of Example 1. FIG. It is a figure explaining the effect of the double-sided image display apparatus of Example 1. FIG. It is a figure explaining the effect of the double-sided image display apparatus of Example 1. FIG. (A)-(e) is a figure showing the light intensity of each part of a double-sided image display apparatus. It is a figure which shows the luminance distribution of the surface light source device in the main liquid crystal panel side and the sub liquid crystal panel side. (B) is a schematic diagram showing the structure of a double-sided image display device according to Comparative Example 1, and (a) is a diagram showing the luminance distribution on the main liquid crystal panel side. (B) is a schematic diagram showing the structure of a double-sided image display device according to Comparative Example 2, and (a) is a diagram showing the luminance distribution on the main liquid crystal panel side. It is a figure showing the result of having measured the intensity | strength of the light which goes out to the main liquid crystal panel side in each double-sided image display apparatus of Example 1, a prior art example, the comparative example 1, Example 2, and Example 9. FIG. It is sectional drawing which shows the double-sided image display apparatus by Example 2 of this invention. It is sectional drawing which shows the double-sided image display apparatus by Example 3 of this invention. FIG. 10 is a cross-sectional view illustrating a modification of Example 3. 10 is a cross-sectional view showing another modification of Example 3. FIG. It is sectional drawing which shows the double-sided image display apparatus by Example 4 of this invention. It is sectional drawing which shows the double-sided image display apparatus by Example 5 of this invention. FIG. 10 is a cross-sectional view showing a modification of Example 5. It is sectional drawing which shows the double-sided image display apparatus by Example 6 of this invention. It is a disassembled perspective view which shows the double-sided image display apparatus concerning Example 7 of this invention. FIG. 11 is an explanatory diagram of the operation of a light emitting unit in Example 7. It is a disassembled perspective view which shows the double-sided image display apparatus concerning Example 8 of this invention. It is a schematic sectional drawing of the double-sided image display apparatus same as the above. FIG. 10 is a plan view showing the arrangement of polarization patterns formed on the light guide plate of Example 8. It is a perspective view which shows the outline of a polarization pattern. (A) is a partially broken plan view showing the uneven diffusion plate on the back surface of the diffusion prism sheet used in the surface light source device of Example 8, (b) is a plan view of a repetitive pattern constituting the uneven diffusion plate, (C) is an expanded perspective view of the convex part which comprises a repeating pattern. It is a perspective view which shows the prism sheet of the diffusion prism sheet used for the surface light source device of Example 8. It is a schematic perspective view explaining the behavior of the light in the surface light source device of Example 8. (A) is a schematic sectional drawing explaining the behavior of the light in a surface light source device same as the above, (b) is the X section enlarged view of (a). It is a figure explaining the relationship between the light quantity radiate | emitted in the range of (DELTA) (theta) from a light emission part, and the light-guide plate area in the range (DELTA) (theta). It is a figure which shows the definition of the output direction of the light radiate | emitted from a light-guide plate. It is a figure which shows the radial brightness nonuniformity (bright line) which arises in a surface light source device. It is a figure which shows the directivity when parallel light makes perpendicular incidence on the uneven | corrugated diffuser plate like FIG. It is a figure which shows the directivity of (omega) direction and (phi) direction when the uneven | corrugated diffusion plate same as the above is placed under the prism sheet of FIG. It is sectional drawing which shows the double-sided image display apparatus by Example 9 of this invention. It is a perspective view which shows the mobile phone of the closed state. It is a perspective view which shows the mobile phone of the open state.

Explanation of symbols

22 main liquid crystal panel 23 surface light source device 24 sub liquid crystal panel 25 point light source 26 light guide plate 27 polarization matching plate 28 frame member 43 deflection pattern 44 light emitting surface 45 pattern surface 51 opening 54 light emitting portion 57 prism sheet

Claims (9)

Double-sided display type image display comprising a light source, a light guide plate that guides light from the light source, spreads it in a plane, and emits it, and image display panels of different sizes arranged opposite to both sides of the light guide plate In the device
A frame member that surrounds the periphery of the image display panel on the small side when viewed from the direction perpendicular to the light guide plate is provided in the vicinity of the image display panel on the small side, and the surface of the frame member that faces the light guide plate has a reflectivity. A small surface,
A double-sided image display device, wherein a transflective plate is disposed between the frame member and a small image display panel and a large image display panel. A light source;
A light guide plate that guides the light from the light source, spreads it in a plane, and emits it;
A frame member disposed to face one surface of the light guide plate, and a surface facing the light guide plate having a low reflectance;
A transflective plate disposed on at least one of positions between one surface of the light guide plate and the middle of the frame member or the other surface of the light guide plate;
A surface light source device. The surface light source device according to claim 2, wherein the transflective plate is formed of a polarization matching plate that transmits light having a certain polarization direction and reflects light having a different polarization direction. In the case where a polarization matching plate that transmits linearly polarized light in a certain polarization direction and reflects linearly polarized light in a polarization direction orthogonal thereto is disposed on both surfaces of the light guide plate, the polarization transmission of both polarization matching plates 3. The surface light source device according to claim 2, wherein the directions of the axes are arranged so as to be orthogonal to each other. The surface light source device according to claim 2, wherein the light guide plate emits light from a surface facing the transflective plate. The surface light source device according to claim 2, wherein the light guide plate is transparent. 3. The surface light source device according to claim 2, wherein the light guide plate has a pattern formed on one surface thereof, and a transflective plate is disposed opposite to both surfaces of the light guide plate. 4. In a double-sided image display device comprising: a light source; a light guide plate that guides light from the light source, spreads the light in a plane, and emits the light; and an image display panel having a different size arranged to face both surfaces of the light guide plate ,
A transflective plate is disposed on the back surface of the small-side image display panel, and a frame member surrounding the small-side image display panel is in the vicinity of the small-side image display panel when viewed from a direction perpendicular to the light guide plate. The double-sided image display device according to claim 1, wherein a reflectance of a surface of the frame member facing the light guide plate is equal to a reflectance of the transflective plate. A light source;
A light guide plate that guides the light from the light source, spreads it in a plane, and emits it;
A frame member disposed to face one surface of the light guide plate;
A transflective plate disposed in the opening of the frame member when viewed from a direction perpendicular to the light guide plate,
A surface light source device, wherein a reflectance of a surface of the frame member facing the light guide plate is equal to a reflectance of the transflective plate.

Images