JP5229040B2 - Illumination device and liquid crystal display device - Google Patents

Description

  The present invention relates to an illumination device and a liquid crystal display device provided in a display device.

  A transmissive liquid crystal display device using a liquid crystal panel is rapidly spreading as a thin display. The liquid crystal display device displays an image by blocking or transmitting light from the illumination device irradiated on the liquid crystal panel surface by the liquid crystal panel.

  With the recent demand for thinner display devices, sidelight type lighting devices have come to be used.

  Patent Literature 1 discloses a sidelight type illumination device including a light source, a light guide plate, a downward prism sheet, and a diffusion plate. In this illuminating device, a rectangular light guide plate, a prism sheet, and a diffusion plate are sequentially stacked in a plan view. And the light source is arrange | positioned at the one end part side of the light-guide plate. In this illuminating device, light from the light source is irradiated to the liquid crystal panel side while being guided through the light guide plate. However, since light is guided by a light guide plate made of a transparent resin such as an acrylic material, there is a problem that it is difficult to reduce the weight.

  Therefore, Patent Document 2 discloses an illuminating device including an optical sheet provided on substantially the entire surface and a reflection sheet arranged with a predetermined gap. In the technique of Patent Document 2, light from the light source is emitted to the outside while guiding the space between the reflection sheet and the optical sheet. As described above, in the technique of Patent Document 2, weight reduction can be realized by omitting the light guide plate.

JP-A-2005-142078 JP-A-10-170723

  However, in the illumination device of Patent Document 2, since light is attenuated by the optical sheet, there is a problem that luminance unevenness of light is generated in a region near and a distant region of the light source.

  The present invention has been made in order to solve the above-described problems, and an object thereof is to provide an illumination device and a liquid crystal display device capable of suppressing light brightness unevenness.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a reflection sheet having one surface made of a reflection member and a position facing the one surface of the reflection sheet. An optical sheet on which a plurality of protrusions are formed, a diffusion plate that is disposed at a position facing the reflection sheet with the optical sheet interposed therebetween, and that diffuses incident light; and between the reflection sheet and the optical sheet A light source that is disposed on one end side of the reflection sheet and the optical sheet and emits light to the light guide space between the reflection sheet and the optical sheet, and in the light guide space A plurality of second ridges that are disposed on the light source side and that are orthogonal to the first ridges are formed on a surface facing the optical sheet, and an end portion on the side far from the light source side is formed on the optical sheet. At the end of the side far from the light source side Compare to, characterized in that it comprises a light control sheet that is located on the light source side.

  The invention according to claim 2 is the invention according to claim 1, wherein the end of the optical control sheet on the side farther from the light source side is the center position of the optical sheet in the light emission direction of the light source. It is more on the light source side.

  According to a third aspect of the present invention, there is provided a lighting device according to the first or second aspect, a liquid crystal panel disposed at a position facing the diffusion plate of the lighting device, and an external video signal. And a driving circuit for driving the liquid crystal panel.

  The invention according to claim 4 is the invention according to claim 1 or 2, wherein a plurality of the illumination devices are provided.

  In the present invention, since the attenuation of light far from the end of the light control member can be reduced, luminance spots can be suppressed.

1 is an overall view of a liquid crystal display device according to a first embodiment. It is sectional drawing of the illuminating device by 1st Embodiment. It is a top view of a light control prism sheet. It is an end view on the + X side of the light control prism sheet. It is a block diagram explaining the control part of a liquid crystal display device. It is a graph which shows the relationship between the brightness | luminance of the illuminating device by 1st Embodiment, and the distance from a light source. It is a graph which shows the relationship between the brightness | luminance of the conventional illuminating device with which the light control prism sheet was formed in the whole surface, and the distance from a light source. It is a general view of the liquid crystal display device by 2nd Embodiment. It is sectional drawing of the illuminating device by 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the following description, XYZ indicated by arrows in FIG. Note that the + Z direction is the front, which is the light emission direction, and the −Z direction is the rear. The + X direction is the light guiding direction.

  As shown in FIG. 1, the liquid crystal display device 1 according to the first embodiment includes a housing 2, a liquid crystal panel 3, a lighting device 4, and a control unit 5 (see FIG. 5).

  The housing 2 accommodates the liquid crystal panel 3, the lighting device 4, and the control unit 5.

  The liquid crystal panel 3 forms an image based on an image signal from the control unit 5. The liquid crystal panel 3 has a polarizing plate, a liquid crystal part, and the like. The liquid crystal panel 3 is disposed in front of the illumination device 4.

  The illumination device 4 supplies light for forming an image to the liquid crystal panel 3. 2 to 4, the illumination device 4 includes three light sources 11R, 11G, and 11B, a reflection sheet 12, a light control prism sheet (light control unit sheet) 13, and a rearward prism sheet (optical sheet). ) 14 and a diffusion plate 15.

  The light sources 11R, 11G, and 11B supply red, green, and blue light, respectively. The light sources 11 </ b> R, 11 </ b> G, and 11 </ b> B are arranged on the one end (−X side end) side of the illumination device 4 with a space therebetween. The light sources 11R, 11G, and 11B are disposed on an extension line in the −X direction of the light guide space 16A formed between the reflection sheet 12 and the light control prism sheet 13. As the light sources 11R, 11G, and 11B, LEDs (light emitting diodes) capable of emitting red, green, and blue light can be applied. In the following description, the reference numerals of the light sources 11R, 11G, and 11B are “11” unless particularly necessary.

  The reflection sheet 12 reflects light traveling backward from the light from the light source 11 forward (in the emission direction). The reflection sheet 12 is formed in a square surface shape in plan view. The reflection sheet 12 is arranged behind the light source 11 (on the opposite side in the emission direction).

  The light control prism sheet 13 guides light from the light source 11 to a distant place. The light control prism sheet 13 is made of a material such as acrylic (PMMA), polycarbonate (PC), or polystyrene (PS) that can transmit light. The light control prism sheet 13 is disposed in front of the light source 11. The light control prism sheet 13 is disposed so as to face the reflective sheet 12 in parallel with a certain space. Thereby, a light guide space 16 </ b> A for guiding light from the light source 11 is formed between the light control prism sheet 13 and the reflection sheet 12.

  As shown in FIG. 3, the light control prism sheet 13 is formed in a rectangular surface shape in plan view. The length of the light control prism sheet 13 in the Y direction is substantially the same as the length of the reflection sheet 12 in the Y direction. On the other hand, the length of the light control prism sheet 13 in the X direction is configured to be about 1/2 to about 1/3 of the length of the reflection sheet 12 in the X direction. Here, the −X side end of the light control prism sheet 13 is disposed so as to substantially coincide with the −X side ends of the reflection sheet 12, the backward prism sheet 14, and the diffusion plate 15. Thereby, the + X side end of the light control prism sheet 13 is arranged closer to the light source 11 than the + X side end of the reflection sheet 12. The end on the + X side is the end on the side opposite to the light source 11.

  On the main surface on the front side of the light control prism sheet 13, a prism pattern including a plurality of protrusions 13a is formed. The protrusion 13a is formed to extend over the entire length of the light control prism sheet 13 in the X direction. The ridge 13a is formed in a triangular prism shape (mountain shape). The plurality of ridges 13a are arranged at equal intervals. In addition, the dotted line shown in FIG. 3 shows the ridgeline of the protrusion 13a.

  The backward-facing prism sheet 14 bends the traveling direction of light from the XY direction to the Z direction. The backward prism sheet 14 is made of a material such as acrylic (PMMA), polycarbonate (PC), or polystyrene (PS) that can transmit light. The rearward prism sheet 14 is formed in the substantially same quadrangular shape as the reflection sheet 12 in plan view. The backward prism sheet 14 is disposed in front of the light control prism sheet 13. The backward prism sheet 14 is disposed in parallel with the reflection sheet 12 and the light control prism sheet 13. As a result, in a region where the light control prism sheet 13 is not disposed, a light guide space 16 </ b> B that guides light from the light source 11 is formed between the rearward prism sheet 14 and the reflection sheet 12.

  On the rear surface of the rearwardly facing prism sheet 14, a ridge 14a having the same shape as the ridge 13a of the light control prism sheet 13 is formed. The ridge 14a is formed to extend in the Y direction. That is, the ridge 14 a of the rearward-facing prism sheet 14 is configured to be orthogonal to the ridge 13 a of the light control prism sheet 13.

  The diffusion plate 15 diffuses the light traveling from the rearward prism sheet 14. The diffusion plate 15 is made of a milky white material such as acrylic (PMMA), polycarbonate (PC), or polystyrene (PS) containing a diffusion material. The diffuser plate 15 is formed in substantially the same quadrangular shape as the reflective sheet 12 and the backward prism sheet 14 in plan view. The diffusion plate 15 is disposed in front of and in parallel with the rearward-facing prism sheet 14.

  Next, the control unit 5 of the liquid crystal display device 1 will be described with reference to FIG. FIG. 5 is a block diagram illustrating a control unit of the liquid crystal display device 1.

  As shown in FIG. 5, the control unit 5 of the liquid crystal display device 1 includes a power supply circuit 21, a video signal processing circuit 22, a liquid crystal driving circuit 23, and a light source driving circuit 24.

  The power supply circuit 21 supplies power to the video signal processing circuit 22, the liquid crystal drive circuit 23, the light source drive circuit 24, and the like.

  The video signal processing circuit 22 receives a video signal from a tuner or the outside. The video signal processing circuit 22 performs signal processing for generating an R signal, a G signal, and a B signal as image data suitable for image display.

  The liquid crystal drive circuit 23 includes a source driver, a gate driver, and a timing controller (not shown). The source driver applies a predetermined voltage to the liquid crystal of the pixel based on the R signal, the G signal, and the B signal output from the video signal processing circuit 23 at the timing of driving the predetermined pixel of the liquid crystal under the control of the timing controller. To do. The gate driver sequentially applies a scanning signal voltage to each gate line to drive one line at a time.

  The light source drive circuit 24 controls the light source 11 of the illumination device 4. The light source driving circuit 24 converts the power supplied from the power supply circuit 21 into a voltage suitable for the light source 11 and outputs the converted voltage.

  Next, the operation of the liquid crystal display device 1 according to the first embodiment will be described.

  First, power is supplied from the power supply circuit 21 to the circuits 22 to 24. When power is supplied, the light source driving circuit 24 converts the power into a predetermined voltage and supplies the voltage to the light source 11 of the lighting device 4.

  In the illumination device 4, when power is supplied, the light source 11 emits light of each color. Of the light emitted from the light source 11, the light traveling backward is reflected by the reflection sheet 12. Thereby, the light guides the light guide space 16 </ b> A between the reflection sheet 12 and the light control prism sheet 13.

  A part of the light is incident on the light control prism sheet 13 and guided inside. A part of the light guided through the light control prism sheet 13, that is, the light reaching the protrusion 13 a is refracted by the protrusion 13 a, exits from the light control prism sheet 13, and enters the backward prism sheet 14. On the other hand, much light that guides the light control prism sheet 13 reaches the end surface of the light control prism sheet 13 on the + X side. Then, the light reaching the end surface is transmitted through the end surface and guided through the light guide space 16B between the reflective sheet 12 and the backward prism sheet 14. The light guided through the light guide space 16B reaches the backward prism sheet 14.

  The light that has reached the rearward prism sheet 14 is refracted by the protrusions 14 a, changes its traveling direction from the surface direction (+ X direction) to the front side (+ Z direction), and enters the rearward prism sheet 14. The light traveling forward is emitted from the front surface of the backward-facing prism sheet 14 and enters the diffusion plate 15. Thereafter, the light is diffused by the diffusing plate 15, and the in-plane luminance is made uniform. Next, the light is emitted from the diffusion plate 15 and then enters the liquid crystal panel 3.

  In the liquid crystal panel 3, the liquid crystal of each pixel is controlled by the liquid crystal driving circuit 23 based on the video signal from the outside. Thereby, the light incident on the liquid crystal panel 3 from the illumination device 4 is optically modulated, and a part of the light is transmitted to form an image.

  As described above, in the illumination device 4 of the liquid crystal display device 1 according to the first embodiment, the + X side end of the light control prism sheet 13 is disposed closer to the light source 11 than the + X side end of the reflection sheet 12. ing. That is, the light control prism sheet 13 is provided only in a part on the light source 11 side. Thereby, in the area | region far from the light source 11, since attenuation | damping of the light by the light control prism sheet 13 can be suppressed, the brightness | luminance in a distant area | region can be improved. That is, light reaching the rear prism sheet 14 is suppressed by the light control prism sheet 13 in the region with high light intensity close to the light source 11, and light is guided by the light control prism sheet 13 in the region 16 B having low light intensity far from the light source 11. The light intensity is increased. As a result, luminance unevenness in the surface direction of the lighting device 4 can be reduced, and the uniformity of luminance can be improved.

  Specific reduction in luminance spots will be described with reference to FIGS. FIG. 6 is a graph showing the relationship between the luminance of the lighting apparatus according to the first embodiment and the distance from the light source. FIG. 7 is a graph showing the relationship between the luminance and the distance from the light source of a conventional illumination device in which the light control prism sheet is formed on the entire surface. The horizontal axis shown in FIGS. 6 and 7 indicates the distance to the light source, and the end portion on the −X side of the reflection sheet 12 is disposed at the position −L / 2, and at the position + L / 2. It is assumed that the + X side end of the reflection sheet 12 is disposed. In addition, the brightness is assumed to have no diffuser.

  As shown in FIG. 6, in the illuminating device 4 by 1st Embodiment, it turns out that the peak of a brightness | luminance is located in the approximate center. Thereby, in the illuminating device 4 by 1st Embodiment, it turns out that a brightness | luminance spot can be reduced by the synthesis | combination with the diffusion plate 15 and the leakage light from the adjacent illuminating device 4. FIG. On the other hand, as shown in FIG. 7, in the conventional lighting device, it can be seen that the luminance peak is biased toward the light source. As a result, it can be seen that even if light is diffused by the diffusion plate, the luminance on the light source side is strong and luminance spots are generated.

  Moreover, in the illuminating device 4, weight reduction can be implement | achieved by shortening the light control prism sheet 13. FIG.

(Second Embodiment)
Next, a lighting device according to a second embodiment in which the lighting device of the first embodiment described above is partially changed will be described. In addition, the same code | symbol is attached | subjected to the structure same as embodiment mentioned above, and description is abbreviate | omitted.

  As shown in FIG. 8, in the liquid crystal display device 1A according to the second embodiment, four illumination devices 4A are arranged in the X direction and the Y direction, respectively. That is, 16 lighting devices 4A are provided in the liquid crystal display device 1A.

  As shown in FIG. 9, the illumination device 4A according to the second embodiment is a tandem system.

  The reflection sheet 12A of the illuminating device 4A is disposed between the light source 11 and the light source 11 of the adjacent block. The reflection sheet 12 </ b> A is disposed so as to be inclined with respect to the light control prism sheet 13. Specifically, the end of the reflection sheet 12 </ b> A opposite to the light source 11 is inclined so as to be closer to the rearward prism sheet 14 than the end on the light source 11 side. Further, the end of the reflection sheet 12 </ b> A opposite to the light source 11 is disposed so as to cover the front of the adjacent light source 11. Thereby, the light emitted from the light source 11 of each illumination device 4A is guided in the + X direction.

  In the illumination device 4A according to the second embodiment, the adjacent backward prism sheet 14 and the backward prism sheet 14 are continuous. Similarly, the adjacent diffusion plate 15 and the diffusion plate 15 are continuous.

  Also in the illumination device 4 </ b> A, the length of the light control prism sheet 13 in the X direction is shorter than the distance between the light source 11 and the light source 11. As a result, the end of the light control prism sheet 13 on the + X direction side is located on the near side of the adjacent light source 11. Here, the position of the end portion on the + X direction side of the light control prism sheet 13 is not particularly limited, but a position of 1/3 from the center between the light source 11 and the adjacent light source 11 is preferable.

  As described above, also in the illuminating device 4A according to the second embodiment, the same effect as that of the first embodiment can be obtained by making the light control prism sheet 13 shorter than the reflection sheet 12A.

  In addition, since the liquid crystal display device 1A includes a plurality of illumination devices 4A, the individual illumination devices 4A can be controlled separately, so that power saving can be realized.

  Further, in the lighting device 4A, the number of parts can be reduced by making the adjacent backward prism sheets 14 continuous. Similarly, the number of parts can be reduced by making adjacent diffusion plates 15 continuous.

  As mentioned above, although this invention was demonstrated in detail using embodiment, this invention is not limited to embodiment described in this specification. The scope of the present invention is determined by the description of the claims and the scope equivalent to the description of the claims. Hereinafter, modified embodiments in which the above-described embodiment is partially modified will be described.

  For example, in the above-described embodiment, the lighting device of the present invention is applied to the liquid crystal display device, but the lighting device according to the present invention may be applied to other transmissive display devices.

  In addition, the numerical values, shapes, materials, and the like applied in each embodiment can be changed as appropriate.

  Also in the first embodiment described above, adjacent rearward prism sheets and diffusion plates may be made continuous as in the second embodiment.

  In the above-described embodiment, the light source 11 has been described as an LED capable of emitting red, green, and blue light. However, an LED capable of emitting white light may be used.

  Further, a cold cathode tube (CCFL) may be used as the light source 11.

  In the above-described embodiment, the light source is installed in the −X direction and the + X direction is set as the light guide direction. However, the light source may be installed in the + X direction and the −X direction may be set as the light guide direction.

  In the above-described embodiment, the case where the light source is installed in the −X direction and the + X direction is the light guide direction is shown as an example. However, the light source is installed in the −Y direction or + Y direction and the + Y direction or − The Y direction may be the light guiding direction.

DESCRIPTION OF SYMBOLS 1, 1A Liquid crystal display device 2 Housing | casing 3 Liquid crystal panel 4, 4A Illuminating device 5 Control part 11, 11R, 11G, 11B Light source 12, 12A Reflection sheet 13 Light control prism sheet 13a Projection 14 Prism sheet 14a Projection 15 Diffusion plate 16A, 16B Light guide space 21 Power supply circuit 22 Video signal processing circuit 23 Video signal processing circuit 23 Liquid crystal drive circuit 24 Light source drive circuit

Claims (4)

A reflective sheet having one surface made of a reflective member;
An optical sheet that is disposed at a position facing the one surface of the reflective sheet and has a plurality of first protrusions formed on at least one surface;
A diffusing plate that is disposed at a position facing the reflective sheet across the optical sheet, and diffuses incident light;
It is a position between the reflection sheet and the optical sheet, and is disposed on one end side of the reflection sheet and the optical sheet, and transmits light to a light guide space between the reflection sheet and the optical sheet. A light source to emit;
A plurality of second protrusions that are disposed on the light source side in the light guide space and that are orthogonal to the first protrusions are formed on a surface facing the optical sheet, and an end portion on the side far from the light source side is formed. A light control sheet positioned on the light source side compared to the end of the optical sheet far from the light source side;
A lighting device comprising:   2. The illumination device according to claim 1, wherein an end of the optical control sheet that is farther from the light source side is closer to the light source than a center position of the optical sheet in a light emission direction of the light source. The lighting device according to claim 1 or 2,
A liquid crystal panel disposed at a position facing the diffusion plate of the lighting device;
A drive circuit for driving a liquid crystal panel based on an external video signal;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 3, comprising a plurality of illumination devices according to claim 1.