JP5229041B2 - 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 light guide plate, a prism sheet, and a diffusion plate are laminated in order. 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 a transmission plate and a rear reflection plate arranged with a predetermined interval. A dot pattern for scattering light is formed on the rear reflector. The dot pattern is formed so that the area increases as the distance from the light source increases in order to reduce luminance spots.

  In the illumination device of Patent Document 2, light emitted from the light source is irradiated to the outside while being guided between the transmission plate and the rear reflection plate. As described above, in the technique of Patent Document 2, weight reduction can be realized by omitting the light guide plate.

JP 2005-142078 A JP 11-218754 A

  However, in the technique of Patent Document 2, since the dot pattern is formed on the reflecting plate, there is a problem that a large amount of light is absorbed by the reflecting plate and the light use efficiency is small.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an illumination device and a liquid crystal display device that can improve light utilization efficiency while suppressing luminance 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 a light guide space between the reflection sheet and the optical sheet, and opposed to the optical sheet A plurality of second ridges orthogonal to the first ridges are formed on the surface, and the second ridges are formed with a plurality of recesses whose surface area increases as the distance from the light source increases. With light control sheet For example, characterized in that is.

  According to the second aspect of the present invention, there is provided a reflecting sheet having one surface made of a reflecting member and a position facing the one surface of the reflecting sheet, and a plurality of first protrusions on at least one surface. Between the formed optical sheet, a diffuser plate that is planar and faces the reflective sheet across the optical sheet, and diffuses incident light, and between the reflective 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 a light guide space between the reflection sheet and the optical sheet, and is opposed to the optical sheet. A plurality of second ridges orthogonal to the first ridge are formed on the surface, and the second ridge has a plurality of recesses that are adjacent to each other and become narrower as the distance from the light source increases. Formed light control sheet and Characterized in that it comprises.

  The invention described in claim 3 is the invention described in claim 1 or 2, further comprising a first light source and a second light source facing each other with the light control sheet interposed therebetween.

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

  The invention according to claim 5 is the invention according to claim 4, characterized in that a plurality of the illumination devices are provided.

  According to the present invention, it is possible to improve light utilization efficiency by suppressing light absorption while suppressing luminance spots.

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 sectional drawing to which the light control prism sheet was expanded partially. 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 provided with the light control prism sheet | seat in which the recessed part is not formed, and the distance from a light source. It is sectional drawing of the illuminating device by 2nd Embodiment. It is a top view of a light control prism sheet. It is a top view of the light control prism sheet by a 3rd embodiment. It is a whole liquid crystal display device by a 4th embodiment. It is sectional drawing of the illuminating device by 4th 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. 6).

  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. The illumination device 4 includes three light sources 11R, 11G, and 11B, a reflection sheet 12, a light control prism sheet (light control sheet) 13, and a rearward prism sheet (optical sheet), as shown in FIGS. 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 16 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 reflection sheet 12 is configured to be able to reflect light on substantially the entire surface.

  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 arranged in front of the light source 11 (exit side). The light control prism sheet 13 is disposed so as to face the reflective sheet 12 in parallel with a certain space. As a result, a light guide space 16 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 light control prism sheet 13 is configured in substantially the same shape as the reflection sheet 12.

  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 (light guide 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.

As shown in FIGS. 2 to 5, a plurality of concave portions 13 b _n (n = 1, 2,... 11) are formed in the main surface on the front side of the light control prism sheet 13 by a post process. The recess 13b _n is formed on the + X side of the center line C in the X direction. The recess 13b _n is formed in a hemispherical shape. Wherein the diameter of each recess 13b _n is formed, and increases as the go on the + X side. Accordingly, as shown in FIG. 3, the opening area of the recess 13b _n is larger him to go on the + X side. Further, as shown in FIG. 2, the depth of the recess 13b _n is deeper him to go on the + X side. Accordingly, the surface area of the recess 13b _n is configured to increase as the distance from the light source 11 increases.

  The backward-facing prism sheet 14 bends the traveling direction of light from the XY direction to the front. 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 and in parallel with the light control prism sheet 13.

  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. 6 is a block diagram illustrating a control unit of the liquid crystal display device 1.

  As shown in FIG. 6, 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. The light emitted from the light source 11 is diffuse light, and the light traveling backward is reflected by the reflection sheet 12. Thereby, the light guides the light guide space 16 between the reflection sheet 12 and the light control prism sheet 13.

  Further, the light diffused forward among the light emitted from the light source 11 gradually enters the light control prism sheet 13 as it is guided through the light guide space 16 and is guided through the light control prism sheet 13. Shine. A part of the light guided through the light control prism sheet 13, that is, the light that reaches the protrusion 13 a passes through the protrusion 13 a and enters the backward prism sheet 14. On the other hand, a lot of light guided through the light control prism sheet 13 is guided in the + X direction beyond the center line C.

As shown by the arrows in FIG. 5, the light beyond the center line C is reached in any of the recesses 13b _n, is emitted to the outside is refracted by the concave portion 13b _n. The light emitted to the outside is refracted by the protrusion 14 a and enters the backward prism sheet 14. Here, the surface area of the recess 13b _n is configured to increase as the distance from the light source 11 increases. As a result, the light guided inside the light control prism sheet 13 decreases as the distance from the light source 11 increases, but the light extraction efficiency is improved, so that the extracted light is made uniform in the surface direction.

  Next, when the light incident on the backward prism sheet 14 is refracted by the protrusion 14a, the traveling direction is changed from the surface direction to the front. 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 light control prism sheet 13 is formed with the recesses 13b _n . The recess 13b _n is configured so that the surface area increases as the distance from the light source 11 increases. Thereby, in the area | region far from the light source 11, since the injection | emission of the light from the light control prism sheet 13 can be improved, the brightness | luminance in a distant area | region can be improved. 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. And since the uniformity of brightness is improved by the recess 13b _n of the light control prism sheet 13, the absorption of light can be suppressed and the light utilization efficiency can be improved. As a result, luminance unevenness can be suppressed while improving the overall luminance.

  Specific reduction in luminance spots will be described with reference to FIGS. FIG. 7 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. 8 is a graph showing the relationship between the brightness and the distance from the light source of a conventional illumination device including a light control prism sheet in which no recess is formed. 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. 7, 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. 8, 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.

In the illumination device 4, the light control prism sheet 13 is formed with the recesses 13 b _n to reduce the weight.

(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 FIGS. 9 and 10, the illumination device 4A according to the second embodiment is different from the first embodiment in the configuration of the light control prism sheet 13A. In the light control prism sheet 13 </ b> A of the second embodiment, the interval between the recess 13 b and the adjacent recess 13 b is arranged so as to become narrower as the distance from the light source 11 increases. All the recesses 13b have the same diameter and depth.

  As described above, in the illuminating device 4A according to the second embodiment, the interval between the recesses 13b is narrowed as the distance from the light source 11 is increased. Therefore, as the distance from the light source 11 is increased, the surface area of the recess 13b per unit area is increased. Can be increased. Thereby, since it is possible to improve the light extraction efficiency as the distance from the light source 11 increases, luminance spots can be suppressed.

(Third embodiment)
Next, a lighting device according to a third 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. 11, in the third embodiment, the light sources 11 are arranged at both ends of the light control prism sheet 13B. Further, the recess 13b _n of the light control prism sheet 13B is formed over the entire length in the X direction. The recess 13b _n is configured such that its diameter and depth increase as it approaches the vicinity of the center line C. That is, the concave portion 13b _n is configured so that the surface area increases as it approaches the vicinity of the center line C.

In the third embodiment as described above also, since the surface area of the recess 13b _n of the light control prism sheet 13B is set larger with distance from the light source 11, it is possible to achieve the same effect as the first embodiment.

(Fourth embodiment)
Next, another embodiment of the liquid crystal display device using the illumination device of the first embodiment or the second embodiment described above 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. 12, in the liquid crystal display device 1A according to the fourth embodiment, four illumination devices 4C are arranged in each of the X direction and the Y direction. That is, 16 lighting devices are provided in the liquid crystal display device 1A.

  Furthermore, as shown in FIG. 13, the liquid crystal display device 1A according to the fourth embodiment is a tandem system.

  The reflective sheet 12C of the illuminating device 4C is disposed between the light source 11 and the light source 11 of the adjacent block. The reflection sheet 12 </ b> C 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> C 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> C 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 4C is guided in the + X direction.

  In the illuminating device 4C according to the fourth embodiment, the adjacent light control prism sheet 13 and the light control prism sheet 13 are continuously formed. Further, 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 4C, as in the first embodiment, the light control prism sheet 13 concave portion 13b _n is configured so that the surface area increases as the distance from the light source 11 increases. Therefore, also in the fourth embodiment. The effect similar to 1st Embodiment can be show | played.

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

  Moreover, in the illuminating device 4C, the number of parts can be reduced by making the adjacent light control prism sheets 13 continuous. In addition, the number of parts can be reduced by making adjacent rearward 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 to third embodiments described above, adjacent rearward prism sheets and diffusion plates may be made continuous as in the fourth embodiment.

  Moreover, you may combine each embodiment. For example, as the distance from the light source increases, the size of the recesses may be increased as in the first embodiment, and the interval between the recesses may be decreased as in the second embodiment.

  In the above-described embodiment, the hemispherical concave portion is taken as an example, but the shape of the concave portion such as a triangular prism-shaped concave portion can be appropriately changed.

  In the second embodiment described above, the concave portion is formed on the + X side from the center line C. However, the concave portion may be formed over the entire length from the vicinity of the end portion on the −X side of the light control prism.

  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.

  Further, in the above-described embodiment, the case where the protrusion of the backward prism sheet is formed on the light control prism sheet side is shown as an example. However, the protrusion of the backward prism sheet may be formed on the diffusion plate side. It may be formed on both sides of the control prism sheet side and the diffusion plate side.

DESCRIPTION OF SYMBOLS 1, 1A Liquid crystal display device 2 Case 3 Liquid crystal panel 4, 4A, 4B, 4C Illumination device 5 Control part 11, 11R, 11G, 11B Light source 12, 12C Reflective sheet 13, 13A, 13B Light control prism sheet 13a Projection 13b , 13b _n recess 14 backward prism sheet 14a ridge 15 diffuser plate 16 light guide space 21 power supply circuit 22 each circuit 22 video signal processing circuit 23 video signal processing circuit 23 liquid crystal driving circuit 24 light source driving circuit

Claims (5)

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 ridges perpendicular to the first ridge are formed on the surface facing the optical sheet, and the second ridge has a plurality of surface areas that increase as the distance from the light source increases. A light control sheet in which a recess is formed;
A lighting device comprising: 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 planar and 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 ridges orthogonal to the first ridges are formed on the surface facing the optical sheet, and the second ridges are adjacent to each other as the distance from the light source increases. A light control sheet in which a plurality of recesses to be narrowed are formed;
A lighting device comprising:   The lighting device according to claim 1, wherein the light source includes a first light source and a second light source facing each other with the light control sheet interposed therebetween. The lighting device according to any one of claims 1 to 3,
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 4, comprising a plurality of the illumination devices.