JP2008084870A - Lighting panel and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light use efficiency of a lighting panel as a backlight arranged on the back side of a liquid crystal display panel and increase the luminance.
A light guide plate 32 of the illumination panel has a light emitting surface 33 on the front surface and an optical surface 35 on the back surface. The optical surface 35 is provided with a large number of a set of optical elements continuously provided in the order of a curved surface 35a, a flat surface 35b, and an inclined surface 35c from the incident surface side (left side in FIG. 3) to the opposite side. It has a structured. The flat surface 35 b is a surface parallel to the emission surface 13. The height H of the inclined surface 35c with respect to the same set of flat surfaces 35b gradually increases from the incident surface 34 side toward the opposite side. The light indicated by the arrows A, B, and C as a representative is finally reflected by one of the inclined surfaces 35c and emitted from the emission surface 33 in the substantially vertical direction.
[Selection] Figure 3

Description

  The present invention relates to a lighting panel and a display device using the same.

  For example, in a liquid crystal display device, since the liquid crystal display panel itself does not have a self-luminous ability, an illumination panel is disposed as a backlight on the back side of the liquid crystal display panel. FIG. 13 shows a partial side view of an example of such a conventional liquid crystal display device. The liquid crystal display device includes a liquid crystal display panel 1 and an illumination panel 11 arranged on the back surface opposite to the surface on the observation side.

  In the liquid crystal display panel 1, the front glass substrate 2 and the back glass substrate 3 are bonded together through a substantially rectangular frame-shaped sealing material (not shown), and are surrounded by the glass substrates 2 and 3 and the sealing material. A structure in which liquid crystal (not shown) is sealed in the open space, the front-side polarizing plate 4 is attached to the surface of the front-side glass substrate 2, and the back-side polarizing plate 5 is attached to the back side of the back-side glass substrate 3. It has become.

  The illumination panel 11 includes a light guide plate 12 provided on the back side of the liquid crystal display panel 1. The light guide plate 12 has a planar rectangular shape, and is a light exit surface 13 through which light exits from the surface facing the liquid crystal display panel 1, and an incident surface 14 through which light enters a predetermined one end surface (left end surface in FIG. 13). The rear surface of the light guide plate 12 is inclined with respect to the light exit surface 13 so that the thickness of the light guide plate 12 gradually decreases from the light incident surface 14 side toward the opposite side. .

  A reflective plate 16 is attached to the inclined surface 15 of the light guide plate 12. A cold cathode tube (light source) 17 is provided at a position facing the incident surface 14 of the light guide plate 12. One end portion of the reflection sheet 18 covering the cold cathode tube 17 is attached to the surface on the incident surface 14 side of the light guide plate 12, and the other end portion is attached to the back surface of the reflection plate 16 on the incident surface 14 side.

  Then, the light emitted from the cold cathode tube 17 and the light reflected by the reflection sheet 18 are incident on the incident surface 14 of the light guide plate 12. The incident light travels (guides light) in the light guide plate 12 from the incident surface 14 side toward the opposite side, is reflected by the reflecting plate 16, and is emitted from the output surface 13 of the light guide plate 12 to be liquid crystal display panel. The liquid crystal display panel 1 is irradiated from the back side. Then, image light corresponding to display driving of the liquid crystal display panel 1 is emitted from the surface of the liquid crystal display panel 1.

  By the way, in the conventional liquid crystal display device, the amount of light emitted from the emission surface 13 of the light guide plate 12 can be made uniform, and the luminance distribution emitted from the surface of the liquid crystal display panel 1 can be made uniform. Next, this will be described. The inclined surface 15 of the light guide plate 12 is provided with a large number of dot-shaped dimming patterns made of black ink so that the density of the dot-shaped black patterns gradually decreases from the incident surface 14 side toward the opposite side. It has been.

  Thereby, the light traveling in the light guide plate 12 is reflected by the reflection plate 16 from the inclined surface 15 side of the light guide plate 12 toward the emission surface 13 side, and the light amount decreases as the distance from the cold cathode tube 17 decreases. By reducing the dot-like black pattern density, the amount of light emitted from the exit surface 13 of the light guide plate 12 is made uniform.

However, in the conventional liquid crystal display device, since a large number of dot-like light control patterns with black ink are provided on the inclined surface 15 of the light guide plate 12, light is absorbed by the light control pattern, and the light use efficiency is improved. There was a problem that the luminance was lowered.
An object of the present invention is to improve light utilization efficiency.

An illumination panel according to a first aspect of the present invention is an optical that includes an incident surface, an exit surface, and a plurality of optical elements including an inclined surface that reflects light incident from the entrance surface toward the exit surface. A light guide plate having a surface and a light source disposed opposite to the incident surface of the light guide plate, wherein each inclined surface of the light guide plate has a corrugated shape in its longitudinal direction. is there.
A lighting panel according to a second aspect of the present invention is the lighting panel according to the first aspect, wherein each of the optical elements further transmits a part of the light incident on the incident surface opposite to the incident surface side. And a curved surface that reflects at a low angle along the parallel plane with respect to a plane parallel to the exit surface.
A lighting panel according to a third aspect of the present invention is the lighting panel according to the second aspect, wherein the curved surface of each optical element is a curved surface that gradually descends in a direction opposite to the exit surface side. Is.
A lighting panel according to a fourth aspect of the present invention is the lighting panel according to the fourth aspect, wherein the curved surface of each optical element has a circular arc shape in cross section.
The lighting panel according to a fifth aspect of the present invention is the lighting panel according to the second aspect, wherein each optical element is provided with a flat surface between the curved surface and the inclined surface. It is.
The display device according to claim 6 is a display device in which an illumination panel is disposed on a back surface side of the display panel. The illumination panel includes an incident surface, an output surface, and light incident from the incident surface. A light guide plate having an optical surface composed of a plurality of optical elements including an inclined surface that reflects toward the emission surface side, and a light source disposed to face the incident surface of the light guide plate, Each inclined surface has a waveform shape in the longitudinal direction.
A display device according to a seventh aspect of the present invention is the display device according to the sixth aspect, wherein a reflective layer is provided on the back surface of the light guide plate.
The display device according to an eighth aspect of the present invention is the display device according to the seventh aspect, wherein the reflective layer is made of a metal film provided on the back surface of the light guide plate.
The display device according to the invention of claim 9 is a liquid crystal display device in which an illumination panel is disposed on the front surface side of the display panel, and reflection means is provided in the display panel or on the back surface side thereof. A light guide plate having an optical surface including an incident surface, an output surface, and a plurality of optical elements including an inclined surface that reflects light incident from the incident surface toward the output surface, and the incident surface of the light guide plate And a light source disposed opposite to each other, and each inclined surface of the light guide plate has a corrugated shape in the longitudinal direction thereof.
The display device according to a tenth aspect of the present invention is the display device according to the ninth aspect, wherein each of the optical elements further transmits a part of the light incident on the incident surface opposite to the incident surface side. And a curved surface that reflects at a low angle along the parallel plane with respect to a plane parallel to the exit surface.
According to an eleventh aspect of the present invention, in the display device according to any one of the sixth to tenth aspects, the curved surface of each optical element is a curved surface that gradually descends in a direction opposite to the exit surface side. It is characterized by this.
A display device according to a twelfth aspect of the present invention is the display device according to the eleventh aspect, wherein the curved surface of each optical element has a circular arc shape in cross section.
A display device according to a thirteenth aspect of the present invention is the display device according to any one of the sixth to tenth aspects, wherein each of the optical elements is provided with a flat surface between the curved surface and the inclined surface. It is characterized by.
According to a fourteenth aspect of the present invention, in the display device according to the thirteenth aspect, the height of the inclined surface of the optical element is located on the opposite side of the height on the incident surface side. The feature is that it is larger.
According to a fifteenth aspect of the present invention, in the display device according to the fourteenth aspect, the height of the inclined surface of the optical element is gradually increased from the incident surface side toward the opposite side. It is characterized by.
The display device according to a sixteenth aspect is the display device according to the fifteenth aspect, wherein the height of the inclined surface of the nth optical element from the incident surface side with respect to the plane is an (n + 1) / 2 ( However, a is an arbitrary number).
The display device according to claim 17 is the display device according to any one of claims 6 to 10, wherein the thickness of the light guide plate gradually increases from the incident surface side toward the opposite side. It is characterized by being gradually thinner later.
The display device according to an invention of claim 18 is the display device according to any one of claims 6 to 10, wherein an inclination angle of the inclined surface of each light guide element with respect to a plane parallel to the emission surface is 40 to 40. It is about 50 °.
A display device according to an invention of claim 19 is the display device according to any of claims 6 to 10, wherein an inclination angle of the inclined surface of each light guide element with respect to a plane parallel to the emission surface is 40 to 40. In the range of about 50 °, it gradually increases from the incident surface side toward the opposite side.
A display device according to a twentieth aspect of the present invention is the display device according to any one of the sixth to tenth aspects, wherein the lengths of the optical elements are the same.
The display device according to a twenty-first aspect is the display device according to any one of the sixth to tenth aspects, wherein at least a part of each of the optical elements is different in length. is there.
A display device according to a twenty-second aspect of the present invention is the display device according to any one of the sixth to tenth aspects, wherein the length of each optical element is about 20 to 500 μm.
A display device according to a twenty-third aspect of the present invention is the display device according to any one of the sixth to tenth aspects, wherein the curvature radius of the curved surface is about 0.1 to 2.0 mm. is there.
A display device according to a twenty-fourth aspect of the present invention is the display device according to any one of the sixth to twenty-third aspects, wherein the light source is a point light source.
A display device according to a twenty-fifth aspect of the present invention is the display device according to the twenty-fourth aspect of the present invention, wherein a plurality of the point light sources are provided.
A display device according to a twenty-sixth aspect is the display device according to the twenty-fifth aspect, wherein the point light source includes three point light sources of red light emission, green light emission, and blue light emission.
According to a twenty-seventh aspect of the present invention, there is provided a display device according to the twenty-sixth aspect of the present invention, wherein color display is performed in combination with field sequential display means.

  According to this invention, the light source is a point light source such as a light-emitting diode by making each inclined surface of the light guide plate have a corrugated shape in the longitudinal direction, and the incident surface of the light guide plate cannot be uniformly irradiated. However, as a result, the light can be emitted in the vertical direction from the light emission surface of the light guide plate, and thus the light use efficiency can be improved.

  FIG. 1 is a side view of a main part of a liquid crystal display device as a first embodiment of the present invention. The liquid crystal display device includes a liquid crystal display panel 21, an illumination panel 31 disposed on the back surface opposite to the surface on the observation side, and a diffusion plate 41 disposed between the panels 21 and 31. Yes.

  In the liquid crystal display panel 21, the front glass substrate 22 and the back glass substrate 23 are bonded together through a substantially rectangular frame-shaped sealing material (not shown), and are surrounded by the glass substrates 22 and 23 and the sealing material. A structure in which liquid crystal (not shown) is sealed in the open space, the front side polarizing plate 24 is attached to the surface of the front side glass substrate 22, and the back side polarizing plate 25 is attached to the back side of the back side glass substrate 23. It has become.

  The liquid crystal display panel 21 may be any one of an active matrix type, a simple matrix type, a segment type, and the display method is also a TN (twisted nematic) method, STN (super twisted nematic) method, ECB. Any method may be used as long as it controls the light transmittance, such as a (birefringence effect) method, a dynamic scattering effect method, or a method using a ferroelectric liquid crystal.

  The illumination panel 31 includes a light guide plate 32 provided on the back side of the liquid crystal display panel 21. The light guide plate 32 has a planar rectangular shape, and is a light exit surface 33 through which light exits from the surface facing the liquid crystal display panel 21, and an incident surface 34 through which light enters a predetermined one end surface (left end surface in FIG. 1). The surface facing the emission surface 33 is an optical surface 35. As shown in FIG. 1, the optical surface 35 generally has a thickness of the light guide plate 32 as the back surface on the back side with respect to the output surface 33 is basically from the incident surface 34 side toward the opposite side. Although it has a so-called ship bottom type profile that is curved so as to become gradually thinner after being gradually thickened, the shape of the optical surface 35 is the greatest feature of the present invention. Will be described later.

  A reflective plate 36 is attached to the optical surface 35 of the light guide plate 32. A cold cathode tube (light source) 37 is provided at a position facing the incident surface 34 of the light guide plate 32. One end portion of the reflection sheet 38 covering the cold cathode tube 37 is attached to the surface on the incident surface 34 side of the light guide plate 32, and the other end portion is attached to the back surface of the reflection plate 36 on the incident surface 34 side.

  Next, the optical surface 35 of the light guide plate 32 will be described with reference to FIG. The optical surface 35 includes a large number of a set of optical elements continuously provided in the order of the curved surface 35a, the flat surface 35b, and the inclined surface 35c from the incident surface 34 side (left side in FIG. 2) to the opposite side. It is a provided surface. The flat surface 35 b is a surface parallel to the emission surface 33.

  The length of a set of optical elements composed of the curved surface 35a, the flat surface 35b, and the inclined surface 35c is about 20 to 500 μm, and the transmission efficiency is improved by gradually increasing the distance from the incident surface 34. From the viewpoint of productivity, Even if the same dimensions are set, there is almost no problem in practical use. The inclination angle of the inclined surface 35c with respect to the flat surface 35b is the same, and is set to an appropriate range of about 40 to 50 °. The height H of the inclined surface 35c with respect to the flat surface 35b gradually increases from the incident surface 34 side toward the opposite side. The height H of the inclined surface 35 c is typically about 20 to 50 μm at the maximum, but is set to an appropriate value depending on the planar size of the light guide plate 32, and is not limited to this value. .

  The length of the curved surface 35a is the same. The length of the flat surface 35b is gradually shortened from the incident surface 34 side toward the opposite side. That is, the length of the flat surface 35b becomes shorter as the height H of the inclined surface 35c increases.

  Each optical element is arranged in the order of the curved surface 35a, the flat surface 35b, and the inclined surface 35c from the incident surface 34 side of the light guide plate 32, and the curved surface 35a is the optical next to the incident surface 34 side (left side in FIG. 2). It is continuously provided on the inclined surface 35c of the element. Although the curved surface 35a is not limited, typically, the cross section thereof has an arc shape, and the curvature radius thereof is, for example, about 0.1 to 2.0 mm. Thus, the curved surface 35a is downwardly inclined in FIG.

  Here, as an example, the height H of the nth inclined surface 35c from the incident surface 34 side with respect to the flat surface 35b is an (n + 1) / 2 (where a is an arbitrary number, n is a natural number, and the incident surface 34 side) The first inclined surface 35c is 1). As described above, by gradually increasing the height H of the inclined surface 35c with respect to the flat surface 35b from the incident surface 34 side toward the opposite side, it is possible to achieve uniformity in brightness on the emission surface 33. Furthermore, as described above, as shown in FIG. 1, the optical surface 35 is curved so that the thickness of the light guide plate 32 gradually increases from the incident surface 34 side toward the opposite side and then gradually decreases. The reason for the bottom shape is that the uniformity of brightness on the exit surface 33 is further improved.

  Further, in FIG. 1, the angle of the incident surface 34 with respect to the output surface 33 is usually 90 °. However, this angle may be slightly smaller than 90 ° in order to improve the light capture efficiency. That is, if the light incident on the light guide plate 32 from the incident surface 34 goes straight and is directly reflected by the inclined surface 35c of the optical surface 35 opposite to the incident surface 34, only that region becomes brighter, When the incident surface 34 is slightly inclined with respect to the output surface 33 so that the incident light travels while being repeatedly reflected by the curved surface 35a and the flat surface 35b of the output surface 33 and the optical surface 35. Light capture efficiency is improved. Normally, this angle is 80 ° or more and less than 90 °, but conversely, it may be 100 ° or less and less than 90 °. In short, the light incident on the light guide plate 32 from the cold cathode tube 37 is the light guide plate 32. The probability of being directly reflected by the inclined surface 35c may be reduced.

  The light guide plate 32 having the above-described structure can be manufactured by injection (compression) molding using a transparent resin having a high light transmittance such as an acrylic resin. Further, the reflecting plate (reflecting layer) 36 shown in FIG. 1 is affixed by bending a metal plate made of Al, Ag, Cr or the like to the optical surface 35 of the light guide plate 32 in a shape along the basic side surface shape. However, the optical surface 35 of the light guide plate 32 may be formed of a metal film formed by vapor-depositing Al, Ag, Cr or the like.

  Here, since the liquid crystal display device of this embodiment is a transmissive / reflective type, the operation of the light guide plate 32 mainly when used as a transmissive type and when used as a reflective type will be described with reference to FIGS. explain. However, in FIGS. 3 and 4, the thickness of the light guide plate 32 is appropriate, and the reflection plate 36 shown in FIG. 1 is omitted.

  First, when the liquid crystal display device of this embodiment is used as a transmission type, as shown by arrows A, B, and C as representative in FIG. 3, light incident on the incident surface 34 shown in FIG. Proceed through 32. Of these, the light indicated by the arrow A is reflected by the inclined surface 35c, converted into an angle substantially perpendicular to the exit surface 33, and emitted from the exit surface 33 in the substantially perpendicular direction.

  The light indicated by the arrow B is reflected by the emission surface 33 and is incident on the curved surface 35a. In this case, since the curved surface 35a is not parallel to the exit surface 33 and is downwardly inclined in FIG. 3, the light incident on the curved surface 35a is reflected at an angle shallower than the incident direction, in other words. Then, it travels in a direction parallel to the exit surface 33 or the plane 35b. For this reason, the light indicated by the arrow B hits the inclined surface 35c of each optical element.

  Thus, each optical element is provided with the curved surface 35a that descends toward the opposite side of the incident surface 34 because the light of the arrow B incident on the incident surface 34 of each optical element is parallel to the traveling direction. It is for making it inject into the inclined surface 35c reliably. Then, the light incident on the inclined surface 35 c is reflected by the inclined surface 35 c, undergoes angle conversion in a direction substantially perpendicular to the emission surface 33, and is emitted from the emission surface 33 in the substantially perpendicular direction.

  The light indicated by the arrow C travels in the light guide plate 32 on the side opposite to the incident surface 34 side, that is, in the right direction in FIG. 3 due to repetition of reflection on the flat surface 35b and reflection on the emission surface 33. Then, this traveling light is finally reflected by the inclined surface 35c and emitted from the emission surface 33 in the substantially vertical direction as in the case of the light indicated by the arrow A, or the arrow B In the same manner as in the case of the light shown by (2), after being reflected by the curved surface 35a, it is reflected by the same set of inclined surfaces 35c and is emitted from the emission surface 33 in the substantially vertical direction.

  As described above, the light indicated by the arrows A, B, and C is finally reflected by any one of the inclined surfaces 35c and is emitted from the emission surface 33 in the substantially vertical direction. Accordingly, almost all of the light incident on the incident surface 34 shown in FIG. 1 is finally reflected by one of the inclined surfaces 35c and is emitted from the emission surface 33 in the substantially vertical direction.

  In addition, in this case, the height H of the inclined surface 35c of each optical element with respect to the flat surface 35b gradually increases toward the opposite side of the incident surface 34 shown in FIG. Therefore, the area of the inclined surface 35c gradually increases from the incident surface 34 side toward the opposite side.

  As a result, even if the amount of light decreases as the distance from the incident surface 34 increases, the amount of light emitted from the exit surface 33 is made uniform by increasing the area of the inclined surface 35c. In addition, in this case, almost all of the light incident on the incident surface 34 is reflected by one of the inclined surfaces 35c and emitted from the emission surface 33 in the substantially vertical direction, thereby improving the light utilization efficiency. Brightness can be increased.

  On the other hand, when the liquid crystal display device of this embodiment is used as a reflection type, as shown by arrows D, E, and F as representative in FIG. 4, external light such as natural light and room light is incident on the emission surface 33. The In this case, however, refraction at the exit surface 33 is ignored. The external light indicated by the arrows D, E, and F is light that is parallel to each other, and is incident on the light exit surface 33 at an incident angle d from the upper right to the lower left in FIG.

  Now, the external light indicated by the arrow D is reflected by the flat surface 35 b and emitted from the emission surface 33. In this case, the reflection on the plane 35b is regular reflection. Therefore, the external light indicated by the arrow D is incident on the plane 35b at the incident angle d, reflected at the reflection angle d, and the reflection angle is 2d.

  External light indicated by an arrow E is reflected on the right side in FIG. 4 of the curved surface 35 a and is emitted from the emission surface 33. In this case, since the curved surface 35a is downwardly inclined in FIG. 4, the reflection angle e on the curved surface 35a is smaller than the reflection angle 2d on the flat surface 35b.

  The light indicated by the arrow F is reflected on the left side in FIG. 4 of the curved surface 35 a and is emitted from the emission surface 33. Also in this case, the curved surface 35a is downwardly inclined in FIG. 4, but the angle of the tangent line at each point of the curved surface 35a with respect to the plane 35b gradually increases toward the left side in FIG. The angle f is smaller than the reflection angle e on the right side of the curved surface 35a.

  As described above, the external light indicated by the arrows D, E, and F entering the emission surface 33 in parallel with each other from the upper right to the lower left in FIG. 4 is regularly reflected or more than the reflection angle at the time of this regular reflection. The light is reflected at a small reflection angle and emitted from the emission surface 33. In this case, since the reflection angle at the curved surface 35a gradually decreases toward the left side in FIG. 4, the angle of the external light reflected from the curved surface 35a and emitted from the emission surface 33 with respect to the normal line of the emission surface 33 in FIG. It becomes smaller gradually toward the left side.

  Therefore, even if the external light indicated by the arrows D, E, and F incident on the emission surface 33 is parallel to each other, the external light indicated by the arrows D, E, and F emitted from the emission surface 33 is incident on the emission surface 33. The light is collected on the left side of FIG. 2 with respect to the vertical direction.

  Next, the case where the liquid crystal display device shown in FIG. 1 is used as a transmission type will be described. When the cold cathode tube 37 is turned on, the light emitted from the cold cathode tube 37 and the light reflected by the reflection sheet 38 are incident on the incident surface 34 of the light guide plate 32. This incident light travels in the light guide plate 32 as shown by arrows A, B, and C as representative in FIG.

  As described above, the light indicated by the arrows A, B, and C is finally reflected by any one of the inclined surfaces 35c and is emitted from the emission surface 33 in the substantially vertical direction. Therefore, almost all of the light incident on the incident surface 34 is finally reflected by any one of the inclined surfaces 35c and is emitted from the emission surface 33 in the substantially vertical direction.

  In addition, in this case, as shown in FIG. 2, the height H of the inclined surface 35c with respect to the same set of planes 35b gradually increases from the incident surface 34 side toward the opposite side. Therefore, the area of the inclined surface 35c gradually increases from the incident surface 34 side toward the opposite side.

  Thereby, even if the amount of light decreases as the distance from the cold cathode tube 37 increases, the amount of light emitted from the emission surface 33 is made uniform by increasing the area of the inclined surface 35c. In addition, in this case, almost all of the light incident on the incident surface 34 is reflected by one of the inclined surfaces 35c and emitted from the emission surface 33 in the substantially vertical direction, thereby improving the light utilization efficiency. Brightness can be increased.

  The light emitted from the emission surface 33 of the light guide plate 32 in the substantially vertical direction is diffused while being transmitted through the diffusion plate 41 and then incident on the back surface of the liquid crystal display panel 21. Irradiate. Then, image light corresponding to display driving of the liquid crystal display panel 21 is emitted from the surface of the liquid crystal display panel 21.

  As described above, when the liquid crystal display device shown in FIG. 1 is used as a transmission type, the light utilization efficiency by the lighting panel 31 can be improved, the luminance can be increased, and the luminance can be made uniform. Quality can be improved.

  On the other hand, when this liquid crystal display device is used as a reflection type, the cold cathode tube 37 is not lit but external light is used. That is, external light incident on the surface of the liquid crystal display panel 21 from the surface side is transmitted through the liquid crystal display panel 21, diffused while passing through the diffusion plate 41, is incident on the output surface 33 of the light guide plate 32, and is reflected. Reflected by the plate 36.

  Contrary to the above, the reflected light is emitted from the emission surface 33 of the light guide plate 32, diffused while passing through the diffusion plate 41, is incident on the back surface of the liquid crystal display panel 21, and the liquid crystal display panel 21 is returned to the back surface side. Irradiate from. Then, image light corresponding to display driving of the liquid crystal display panel 21 is emitted from the surface of the liquid crystal display panel 21.

  Here, the case where this liquid crystal display device is actually used as a reflection type will be described. In an actual use state, when the upper end side of the screen of the liquid crystal display panel 21 is the right end side of FIG. 1, generally, the liquid crystal display panel 21 is tilted so as to mainly capture external light coming from the upper right to the lower left of FIG. In many cases, the screen is visually observed from the front direction of the screen of the liquid crystal display panel 21, that is, the direction perpendicular to the screen or a slightly lower side (left side in FIG. 1).

  Therefore, when the liquid crystal display panel 21 is tilted so as to mainly capture the external light coming from the upper right to the lower left in FIG. 1, the external light transmitted through the liquid crystal display panel 21 and the diffusion plate 41 as it is is represented by an arrow in FIG. As indicated by D, E, and F, the light enters the light exit surface 33 of the light guide plate 32. However, also in this case, refraction at the exit surface 33 is ignored. Moreover, the external light shown by the arrows D, E, and F is light parallel to each other.

  As described above, the external light indicated by the arrows D, E, and F that are incident on the emission surface 33 of the light guide plate 32 is reflected regularly or reflected at a reflection angle smaller than the reflection angle at the time of regular reflection and emitted. The light is emitted from the surface 33. In this case, since the reflection angle at the curved surface 35a gradually decreases toward the left side in FIG. 4, the angle of the external light reflected from the curved surface 35a and emitted from the emission surface 33 with respect to the normal line of the emission surface 33 in FIG. It becomes smaller gradually toward the left side.

  Therefore, even if the external light indicated by the arrows D, E, and F incident on the emission surface 33 is parallel to each other, the external light indicated by the arrows D, E, and F emitted from the emission surface 33 is incident on the emission surface 33. The light is collected on the left side of FIG. 4 with respect to the vertical direction. Then, when these external lights are transmitted through the diffusion plate 41 and the liquid crystal display panel 21 as they are, the image is displayed in a slightly lower side (left side in FIG. 1) than the front direction of the screen of the liquid crystal display panel 21, that is, the direction perpendicular to the screen. Light is collected and emitted.

  Thus, when this liquid crystal display device is actually used as a reflection type, the front direction of the screen of the liquid crystal display panel 21, that is, the direction perpendicular to the screen, is based on the external light coming from the upper right to the lower left in FIG. The image light can be condensed and emitted in a slightly lower direction (left side in FIG. 1). In this case, the emission direction of the image light is a viewing direction, and thus a bright image is obtained.

  By the way, the diffuser plate 41 improves the in-plane uniformity of transmitted light and reflected light when used as a transmissive type or a reflective type, thereby adjusting the viewing angle and also being used as a reflective type. Sometimes it is for reducing double shots.

  When the surface of the diffusing plate 41 is made uneven by using a filler material or the like, the uneven shape makes the incident angle and the incident range for taking in the outside light spread in all directions, and the double reflection is further enhanced due to high diffusibility. Can be reduced.

  Further, without using the diffusion plate 41, a filler having a refractive index different from that of the adhesive is mixed in the adhesive for attaching the back-side polarizing plate 25 of the liquid crystal display panel 21 to the back-side glass substrate 23. You may make it have a spreading | diffusion function. Further, an adhesive having such a diffusion function may be used, and the diffusion plate 41 may be used.

  Further, instead of the general diffusion plate 41, a transmission / diffusion plate 42 as shown in FIG. 5 may be used. The transmission / diffusion plate 42 is formed by alternately arranging a transmission layer 43 made of a colorless transparent resin or the like and a diffusion layer 44 made of a white transparent resin or the like.

  In this case, the thickness of the transmission / diffusion plate 42 is constant, but both the transmission layer 43 and the diffusion layer 44 are in the same direction with respect to the plate surface of the transmission / diffusion plate 42 (in this case, from the upper right side in FIG. 5). It is tilted appropriately (towards the lower left). In FIG. 5, the upper right portion of the diffusion layer 44 and the lower left portion of the right diffusion layer 44 are in contact with or overlap in the left-right direction.

  As shown in FIG. 3, when used as a transmission type, the light emitted from the emission surface 33 of the light guide plate 32 in the substantially vertical direction is indicated by an arrow in FIG. The refraction at the surface of the plate 42 is ignored.) The light is diffused by the diffusion layer 44 of the transmission / diffusion plate 42 and emitted from the surface of the transmission / diffusion plate 42.

  In this case, since the upper right part of the diffusion layer 44 and the lower left part of the right diffusion layer 44 in FIG. 5 are in contact with or overlap in the left-right direction, the light is emitted from the light emission surface 33 of the light guide plate 32 in the substantially vertical direction. All of the emitted light is reliably diffused by any diffusion layer 44 of the transmission / diffusion plate 42.

  On the other hand, when used as a reflection type, as indicated by solid line arrows in FIG. 6 (however, refraction on the front and back surfaces of the transmission / diffusion plate 42 is ignored), the outside that has progressed from the upper right to the lower left. The light passes through the transmission layer 43 of the transmission / diffusion plate 42.

  This transmitted light is reflected by the optical surface 35 of the light guide plate 32 as indicated by an arrow in FIG. This reflected light is diffused and transmitted by the diffusion layer 44 of the transmission / diffusion plate 42 as indicated by the dotted arrows in FIG. 6 (however, refraction on the back and front surfaces of the transmission / diffusion plate 42 is ignored). The light is emitted from the surface of the cum diffusion plate 42.

  Also in this case, since the upper right portion of the diffusion layer 44 and the lower left portion of the diffusion layer 44 on the right side in FIG. 6 are in contact with or overlap with each other in the left-right direction, all of the light emitted from the emission surface 33 of the light guide plate 32 is obtained. Is reliably diffused by any diffusion layer 44 of the transmission / diffusion plate 42.

  Here, the optical surface 35 of the light guide plate 32 is not limited to that shown in FIG. For example, referring to FIG. 2, the inclination angle of the inclined surface 35c of each optical element with respect to the flat surface 35b gradually increases from the incident surface 34 side toward the opposite side within a range of about 40 to 50 °. You may do it.

  Further, the lengths of the optical elements composed of the curved surface 35a, the flat surface 35b, and the inclined surface 35c may be different. For example, by making the lengths of the curved surface 35a and the flat surface 35b constant and the height H of the inclined surface 35c different, the length of a set of optical elements composed of the curved surface 35a, the flat surface 35b and the inclined surface 35c is made different. Also good. However, in this case as well, the length of a set of optical elements composed of the curved surface 35a, the flat surface 35b, and the inclined surface 35c is in the range of about 20 to 500 μm.

  In the first embodiment, as shown in FIG. 1, the illumination panel 31 is disposed on the back side of the liquid crystal display panel 21, and the diffusion plate 41 is disposed between the panels 21, 31. Not only this but the illumination panel 31 is arrange | positioned at the surface side of the liquid crystal display panel 21, and the diffusing plate 41 is arrange | positioned between both panels 21 and 31 like 2nd Embodiment of this invention shown in FIG. May be.

  However, in this case, the emission surface 33 of the light guide plate 32 of the illumination panel 31 is the back surface side, and the optical surface 35 is the front surface side. Further, no reflecting plate is provided on the optical surface 35 of the light guide plate 32. Further, a flat reflector 45 is provided on the back side of the liquid crystal display panel 21.

  Next, the case where the liquid crystal display device shown in FIG. 7 is used as a transmission type will be described. When the cold cathode tube 37 is turned on, the light emitted from the cold cathode tube 37 and the light reflected by the reflection sheet 38 are incident on the incident surface 34 of the light guide plate 32. Almost all of the incident light is emitted from the emission surface 33 of the light guide plate 32 in the substantially vertical direction, as in the case of the first embodiment.

  The emitted light is diffused while being transmitted through the diffusion plate 41, transmitted through the liquid crystal display panel 21, and reflected by the reflection plate 45. The reflected light is incident on the back surface of the liquid crystal display panel 21 and irradiates the liquid crystal display panel 21 from the back surface side. Then, image light corresponding to display driving of the liquid crystal display panel 21 is emitted from the surface of the liquid crystal display panel 21. The image light is diffused while passing through the diffusion plate 41, and then passes through the light guide plate 32. And this transmitted image light is visually observed.

  On the other hand, when the liquid crystal display device shown in FIG. 7 is used as a reflection type, the cold-cathode tube 37 is not turned on and external light is used. That is, external light incident on the optical surface 35 of the light guide plate 32 from the surface side is transmitted through the light guide plate 32, diffused through the diffuser plate 41, transmitted through the liquid crystal display panel 21, and reflected by the reflector 45. Reflected.

  The reflected light is incident on the back surface of the liquid crystal display panel 21 and irradiates the liquid crystal display panel 21 from the back surface side. Then, image light corresponding to display driving of the liquid crystal display panel 21 is emitted from the surface of the liquid crystal display panel 21. The image light is diffused while passing through the diffusion plate 41, and then passes through the light guide plate 32. And this transmitted image light is visually observed.

  By the way, in the liquid crystal display device shown in FIG. 7, light is transmitted twice through the liquid crystal display panel 21 when used as a transmission type or a reflection type, so that the polarizing plate is either on the front side or the back side. It is good as one piece. Moreover, you may make it form the electrode provided in the inner surface of the back surface side glass substrate 23 with a reflective metal, without using the reflecting plate 45. FIG.

  Moreover, although the said embodiment demonstrated the case where a cold cathode tube (line light source) was used as a light source, you may make it use not only this but a light emitting diode (point light source). For example, as shown in FIG. 8, one light emitting diode 51 may be arranged at a position facing the central portion in the longitudinal direction of the incident surface 34 of the light guide plate 32 of the liquid crystal display device shown in FIG. 1 or 7. .

  By the way, in the case of the cold cathode tube 37 which is a line light source, the incident surface 34 of the light guide plate 32 can be uniformly irradiated by the light emitted from the cold cathode tube 37. On the other hand, in the case of the light emitting diode 51 which is a point light source, the incident surface 34 of the light guide plate 32 cannot be uniformly irradiated by the light emitted from the light emitting diode 51.

  For this reason, when the light emitting diode 51 is used, as indicated by a one-dot chain line in FIG. 9, the virtual surface G is perpendicular to the emission surface 33 of the light guide plate 32 and parallel to the incident surface 34. Out of the emitted light, as indicated by the solid arrow, the light incident perpendicularly to the flat incident surface 34 is emitted in a direction perpendicular to the emitting surface 33, but the other light is a dotted line. As indicated by the arrow, the light is emitted in an oblique direction.

  Therefore, as shown in FIG. 8, the luminance of the region indicated by the symbol N on both sides of the region indicated by the symbol M that is substantially opposite to the light-emitting diode 51 on the emission surface 34 of the light guide plate 32 is greatly reduced, and the light utilization efficiency is increased. In addition to this, luminance unevenness occurs. As a result, display unevenness occurs in the liquid crystal display panel.

  Therefore, a third embodiment of the present invention capable of preventing such luminance unevenness from occurring will now be described. FIG. 10 is a partial schematic plan view for explaining a liquid crystal display device as a third embodiment of the present invention.

  In the liquid crystal display device of this embodiment, basically, one light emitting diode 51 is arranged at a position facing the central portion in the longitudinal direction of the incident surface 34 of the light guide plate 32, as in the case shown in FIG. ing. However, in this case, the inclined surface 35c of each optical element forming the optical surface of the light guide plate 32 is a surface that is uneven in a sine curve shape (wave shape) in the longitudinal direction.

  As an example of the waveform shape of the inclined surface 35c of each optical element, when the amplitude is A, it is appropriate that the wavelength λ is a sine curve of 2Aπ. However, the wavelength λ is not limited to this. It can be about 1 to 10 times.

  As a result, as indicated by a one-dot chain line in FIG. 11, the light emitted from the light emitting diode 51 is not only the light incident perpendicularly to the incident surface 34 but also other light as indicated by the solid line arrow. The inclined surfaces 35c of the optical elements are reflected in a direction parallel to the virtual plane G perpendicular to the emission surface 33 of the light guide plate 32.

  Therefore, even if the incident surface 34 of the light guide plate 32 cannot be uniformly irradiated by the light emitted from the light emitting diode 51, the light is emitted uniformly from the output surface 34 of the light guide plate 32, the light use efficiency is high, and the luminance is also high. It is made uniform. As a result, display unevenness can be prevented from occurring in the liquid crystal display panel. In the above, the incident surface 34 of the light guide plate 32 can also have a waveform shape similar to that of the inclined surface 35c, but care must be taken so that the amount of light incident on the light guide plate 32 is not dense. .

  Moreover, although the said 3rd Embodiment demonstrated the case where the one light emitting diode 51 was arrange | positioned, you may make it arrange not only this but two or more. In this case, even if there is a color variation in the light emitting diode itself, the waveform shape of the inclined surface 35c of the light guide plate 32 can be made difficult to recognize.

  Further, as in the fourth embodiment of the present invention shown in FIG. 12, a plurality of light emitting diodes of different light emission colors, for example, three light emitting diodes 51R, 51G, 51B of red light emission, green light emission and blue light emission are arranged. May be. In this case, by appropriately blinking the three light emitting diodes 51R, 51G, and 51B, it is possible to obtain a color other than the light emission color of the single light emitting diode by color mixing.

  In the case of the configuration shown in FIG. 12, color display can be performed without using a color filter by combining with a field sequential display means.

  That is, one pixel is composed of an R pixel, a G pixel, and a B pixel. When, for example, the R pixel and the G pixel are in a bright state, first, the light emitting diode 51R is turned on for a certain period of time with only the R pixel being transmissive. Then, when the light emitting diode 51G is turned on for a certain period of time with only the G pixel being transmissive, the R pixel and the G pixel are visually observed at the same time due to the afterimage phenomenon. In this case, since color display can be performed without a color filter, high transmittance can be achieved and low power consumption can be achieved.

The side view of the principal part of the liquid crystal display device as 1st Embodiment of this invention. The figure shown in order to demonstrate the optical surface of the light-guide plate shown in FIG. The figure shown in order to demonstrate the effect | action in the case of using as a transmission type of the light-guide plate which has an optical surface shown in FIG. The figure shown in order to demonstrate the effect | action in the case of using as a reflection type of the light-guide plate which has an optical surface shown in FIG. The figure shown in order to demonstrate the effect | action in the case of using as a permeation | transmission type | mold of the permeation | transmission and diffusion plate used instead of a general diffuser plate. The figure shown in order to demonstrate the effect | action in the case of using as a reflection type of a permeation | transmission and diffuser plate. The side view of the principal part of the liquid crystal display device as 2nd Embodiment of this invention. The top view shown in order to demonstrate the problem in the case of using a light emitting diode as a light source in the case shown in FIG. 1 or FIG. The figure shown in order to demonstrate the advancing state of the light in the case shown in FIG. FIG. 9 is a schematic plan view of a part of the liquid crystal display device as a third embodiment of the present invention. The figure shown in order to demonstrate the advancing state of the light in the case shown in FIG. The one part typical perspective view shown in order to demonstrate the liquid crystal display device as 4th Embodiment of this invention. FIG. 10 is a side view of a part of an example of a conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Liquid crystal display panel 31 Illumination panel 32 Light guide plate 33 Output surface 34 Incident surface 35 Optical surface 35a Curved surface 35b Plane 35c Inclined surface 36 Reflector plate 37 Cold cathode tube 38 Reflective sheet 41 Diffusion plate 42 Transmission / diffusion plate 51 Light emitting diode

Claims (27)

  A light guide plate having an optical surface including an incident surface, an output surface, and a plurality of optical elements including an inclined surface that reflects light incident from the incident surface toward the output surface, and the incident surface of the light guide plate And a light source disposed opposite to each other, and each inclined surface of the light guide plate has a waveform shape in the longitudinal direction thereof.   2. The optical element according to claim 1, wherein each of the optical elements further has a part of the light incident on the incident surface directed toward a side opposite to the incident surface and parallel to the exit surface. An illumination panel comprising a curved surface that reflects at a low angle along the parallel plane.   3. The lighting panel according to claim 2, wherein the curved surface of each optical element is a curved surface that gradually falls in a direction opposite to the exit surface side.   4. The lighting panel according to claim 3, wherein the curved surface of each optical element has a circular arc shape in cross section.   The lighting panel according to claim 2, wherein each optical element is provided with a flat surface between the curved surface and the inclined surface.   In the display device in which the illumination panel is disposed on the back surface side of the display panel, the illumination panel includes an incident surface, an exit surface, and an inclined surface that reflects light incident from the entrance surface toward the exit surface side. A light guide plate having an optical surface composed of a plurality of optical elements, and a light source disposed to face the incident surface of the light guide plate, and each inclined surface of the light guide plate has a waveform shape in its longitudinal direction. A display device.   The display device according to claim 6, wherein a reflective layer is provided on a back surface of the light guide plate.   8. The display device according to claim 7, wherein the reflective layer is made of a metal film provided on a back surface of the light guide plate.   In a liquid crystal display device in which an illumination panel is disposed on the front surface side of the display panel, and reflection means is provided in the display panel or on the rear surface side thereof, the illumination panel is incident on an incident surface, an output surface, and the incident surface. A light guide plate having an optical surface composed of a plurality of optical elements including an inclined surface that reflects the emitted light toward the exit surface side, and a light source disposed facing the incident surface of the light guide plate, A display device, wherein each inclined surface of the light guide plate has a waveform shape in a longitudinal direction thereof.   The invention according to claim 9, wherein each of the optical elements further has a part of the light incident on the incident surface directed toward a side opposite to the incident surface side with respect to a surface parallel to the emission surface. A display device comprising a curved surface that reflects at a low angle along the parallel plane.   11. The display device according to claim 6, wherein the curved surface of each optical element is a curved surface that gradually descends in a direction opposite to the exit surface side.   12. The display device according to claim 11, wherein the curved surface of each optical element has a circular arc shape in cross section.   11. The display device according to claim 6, wherein each of the optical elements is provided with a flat surface between the curved surface and the inclined surface.   14. The display device according to claim 13, wherein the height of the inclined surface of the optical element is larger at the opposite side than at the incident surface side. .   15. The display device according to claim 14, wherein the height of the inclined surface of the optical element is gradually increased from the incident surface side toward the opposite side.   The height of the inclined surface of the nth optical element from the incident surface side with respect to the plane is an (n + 1) / 2 (where a is an arbitrary number). Display device.   11. The display device according to claim 6, wherein the thickness of the light guide plate is gradually decreased after being gradually increased from the incident surface side toward the opposite side. .   11. The display device according to claim 6, wherein an inclination angle of the inclined surface of each light guide element with respect to a plane parallel to the emission surface is about 40 to 50 °.   The invention according to any one of claims 6 to 10, wherein an inclination angle of the inclined surface of each light guide element with respect to a plane parallel to the emission surface is within a range of about 40 to 50 ° from the incident surface side. A display device characterized by gradually increasing toward the opposite side.   11. The display device according to claim 6, wherein the optical elements have the same length.   11. The display device according to claim 6, wherein at least a part of each optical element is different in length.   11. The display device according to claim 6, wherein each optical element has a length of about 20 to 500 [mu] m.   11. The display device according to claim 6, wherein a radius of curvature of the curved surface is about 0.1 to 2.0 mm.   24. The display device according to claim 6, wherein the light source is a point light source.   25. The display device according to claim 24, wherein there are a plurality of point light sources.   26. The display device according to claim 25, wherein the point light source comprises three point light sources of red light emission, green light emission, and blue light emission.   27. The display device according to claim 26, wherein color display is performed in combination with field sequential display means.

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