JP2008153039A - Lighting device and liquid crystal display equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device capable of irradiating white light of a desired chromaticity even without the use of a white LED of the desired chromaticity. <P>SOLUTION: A light source part 33 equipped with LEDs 40 is arranged on a side face of a plate-like light guide body 36. The LEDs 40 consist of white LEDs 40a irradiating white light, and blue LEDs 40b irradiating blue light. In case light irradiated by the white LEDs 40a is somewhat yellowish in comparison with a targeted chromaticity of light to be irradiated from a light-irradiating face 36a of the light guide body 36, emission light of the blue LEDs 40b is controlled to be reinforced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illumination device used as a backlight in a liquid crystal display device and a liquid crystal display device including the same.

  In recent years, a liquid crystal display device using a liquid crystal panel that is thinner than a CRT (Cathode Ray Tube) has been widely used as a display device. Since the liquid crystal panel itself does not emit light, an image is displayed by irradiating light from outside light or an illumination device (backlight unit) disposed on the back of the liquid crystal panel.

  Conventionally, a cold cathode tube is used as a light source of a backlight unit used in a liquid crystal display device, but recently an LED (Light Emitting Diode) has also begun to be used. A white LED is used in an illumination device using an LED lamp as a light source.

Since it is difficult to suppress the variation in emission color of each individual when producing white LEDs, the white LEDs are used after being classified according to the actual emission color. Therefore, the variation in the emission color of each individual white LED can be suppressed by using white LEDs of the same rank in a small number of backlight units. However, since it is difficult to obtain a large amount of white LEDs of the same rank, it has been difficult to suppress variations in emission color for each backlight unit produced in large quantities. Therefore, Patent Document 1 proposes a color tone adjustment circuit that adjusts the light emission color tone by controlling the forward current of the white LED. Patent Document 2 proposes a color correction filter that corrects the white chromaticity of the white LED.
Japanese Patent Laid-Open No. 2001-272938 (page 2 to page 3, FIG. 1) JP 2004-117542 A (page 3 to page 6, FIG. 2)

  However, in the method proposed in Patent Document 1, in order to change the chromaticity, the current must be changed greatly, and the desired luminance may not be obtained even if the desired chromaticity is obtained. Further, in the method proposed in Patent Document 2, it is difficult to accurately correct a large number of backlight units because a color correction filter matched to the chromaticity of the white LED must be individually prepared. Even if several types of filters are prepared according to the chromaticity, the correction by the filters is stepwise.

  Therefore, an object of the present invention is to provide an illuminating device that can easily obtain white light emission having a desired chromaticity and luminance even if a white LED having a desired chromaticity cannot be obtained.

  In order to achieve the above object, the present invention includes an LED and a control device that controls light emission of the LED, and in an illumination device in which the emitted light is white, the LED includes a white LED and a blue LED, The control device is capable of independently controlling light emission of the white LED and the blue LED.

  In the illumination device having the above-described configuration, the present invention is characterized in that the white LED and the blue LED are arranged adjacent to each other.

  The present invention further includes a control device that controls light emission of the LED, wherein the LED includes a white LED chip and a blue LED chip, and the control device includes the white LED chip. The light emission of the blue LED chip can be controlled independently.

  Further, the present invention is characterized in that the LED includes a frame body that surrounds the white LED chip and the blue LED chip, and the frame body includes a partition that separates the white LED chip and the blue LED chip. .

  According to the present invention, in the lighting device having the above-described configuration, a plate-shaped light guide that emits light incident from the side surface is emitted from the output surface, and the LEDs are arranged in a row on the side surface of the light guide. Features.

  According to the present invention, in the illumination device having the above configuration, the LEDs are arranged in a planar shape.

  According to the present invention, in the illumination device configured as described above, the illumination device includes a color measurement device that measures chromaticity of the emitted light, and the control device controls light emission of the LED based on an output of the color measurement device. And

  According to another aspect of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal panel; and the illumination device having the above-described configuration disposed on a back surface of the liquid crystal panel.

  According to the present invention, even if the white LED does not emit light at a desired chromaticity, a blue LED is provided in addition to the white LED, and each light emission is controlled, so that the white light emission of the lighting device can be easily performed. Desired chromaticity and chromaticity can be obtained.

  Further, according to the present invention, by arranging the white LED and the blue LED adjacent to each other, the light emitted from each LED can be mixed uniformly, and the light emitted from the lighting device has less color unevenness. can do.

  Moreover, according to this invention, an illuminating device can be made into the direct lower type by which the sidelight type | mold provided with the plate-shaped light guide or white LED was arrange | positioned planarly.

  According to the present invention, a liquid crystal display device with high display quality can be obtained by adjusting the light emitted from the illumination device to a chromaticity suitable for display.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a plan view of a backlight according to the first embodiment of the present invention, and FIG. 3 is a first embodiment of the present invention. It is a side view of the backlight concerning a form.

  As shown in FIG. 1, the liquid crystal display device 10 includes a liquid crystal panel 20, a backlight 30 as an illumination device, and a control device 50. The liquid crystal panel 20 includes a TFT substrate, a counter substrate, and liquid crystal sealed therebetween, and controls the orientation of the liquid crystal by applying a voltage to both the substrates based on a signal from the control device 50 to display an image. . The backlight 30 is disposed on the back surface of the liquid crystal panel 20 and irradiates an image displayed on the liquid crystal panel 20 with white light emitted from the emission surface. Between the backlight 30 and the liquid crystal panel 20, a color measuring device 39 that measures the chromaticity of light emitted from the LED 40 and emitted from the emission surface 36 a of the light guide 36 is provided. The color measuring device 39 is made of, for example, a photodiode. Further, the control device 50 controls not only the liquid crystal panel 20 but also the current that flows through the backlight 30. When controlling the current flowing through the backlight 30, the control device 50 can receive not only the predetermined predetermined control but also the output of the color measurement device 39 and perform control based on it.

  As shown in FIGS. 2 and 3, the backlight 30 of the present embodiment is of a sidelight type including a light source unit 33, a plate-shaped light guide 36, a reflection sheet 37, and a diffusion sheet 38. The light source unit 33 includes an FPC (Flexible Printed Circuit Board) 34 and an LED 40 disposed on the FPC 34, and is disposed so that light emitted from the LED 40 is incident on a side surface of the light guide 36. Has been. The reflection sheet 37 is provided on the surface of the light guide 36 opposite to the surface facing the liquid crystal panel 20, and the diffusion sheet 38 is the surface of the light guide 36 that faces the liquid crystal panel 20. Is provided. The light source unit 33, the light guide 36, the reflection sheet 37, and the diffusion sheet 38 are covered with a frame 31 including a lower frame 31a and an upper frame 31b. The lower frame 31a is fitted inside the upper frame 31b, and the FPC 34 and the reflection sheet 37 are fixed to the inner surface thereof. The upper frame 31b has an opening so that the emission surface 36a of the light guide 36 is exposed. However, in FIG. 2, the upper frame 31 b and the diffusion sheet 38 are omitted for easy understanding of the structure of the backlight 30. In addition, mounting of LED40 is not limited on FPC34, You may implement on a hard board | substrate.

  The light emitted from the LED 40 of the light source unit 33 enters the side surface of the light guide 36, propagates through the light guide 36, and is emitted as white light from the emission surface 36a. White light emitted from the emission surface 36a is diffused by the diffusion sheet 38 and becomes uniform. The light emitted from the light guide 36 toward the reflection sheet 37 is also reflected by the reflection sheet 37, and is incident on the light guide 36 again, propagates through the light guide 36, and is emitted from the emission surface 36a. On the surface of the light guide 36 on the side of the reflection sheet 37, unevenness and a pattern by printing are formed so that the brightness of light emitted from the emission surface 36a is constant.

  Here, white light will be described with reference to the chromaticity diagram of FIG. In FIG. 4, a broken line ellipse at the center is a white region 60. Even within the white region 60, the color tone of white varies depending on the location. The white region 60 is white with yellow in the upper right chromaticity and blue in the lower left. The light that irradiates the liquid crystal panel 20 is preferably chromaticity indicated by a solid-line ellipse near the lower left of the white region 60 that is white with blue. In the present embodiment, this chromaticity is set as the target chromaticity 65. The target chromaticity 65 is not limited to that shown in FIG. 4 and may be changed as appropriate according to the location where the liquid crystal display device 10 is used, the user's preference, and the like.

  In the present embodiment, the LED 40 includes a white LED 40a in which emitted light belongs to the white region 60, and a blue LED 40b in which emitted light belongs to the blue region 62 shown in FIG. The white LED 40a and the blue LED 40b are independently controlled by the control device 50 to adjust the luminance. This is possible by connecting the white LED 40a and the blue LED 40b to the control device 50 electrically independently.

  As such a connection method, for example, as shown in FIG. 5, a white LED group in which only white LEDs 40 a are connected in series and a blue LED group in which only blue LEDs 40 b are connected in series are independently connected to the control device 50. There is a way. In addition, as shown in FIG. 5, all the blue LEDs 40b may be connected in series so that only one blue LED group is provided, or a plurality of blue LED groups are provided by dividing the blue LEDs 40b into a plurality as shown in FIG. , Each may be connected to the control device 50 independently. In FIG. 6, one or two blue LEDs 40b are included in each blue LED group, but the number of blue LEDs 40b included in the blue LED group is not limited to this.

  It is preferable that the white LED 40a and the blue LED 40b are arranged as dispersed as possible in order to uniformly mix the light emitted from each of the white LEDs 40a and the color unevenness of the light emitted from the emission surface 36a. For example, if the number of white LEDs 40a and the number of blue LEDs 40b is substantially the same, it is preferable to arrange the white LEDs 40a and the blue LEDs 40b alternately as shown in FIG. Moreover, when the number of white LED 40a and blue LED 40b differs, it is preferable to arrange | position the smaller LED40 at equal intervals as much as possible. In any case, in order to more uniformly mix the light emitted from the white LED 40a and the blue LED 40b, it is preferable to arrange the white LED 40a and the blue LED 40b adjacent to each other as much as possible.

  In the present embodiment, when the liquid crystal display device 10 is turned on, only the white LED 40 a is lit at a predetermined current value under the control of the control device 50, and light emitted from the light exit surface 36 a of the light guide 36 by the color measuring device 39. The control device 50 receives the output. Subsequently, with the white LED 40a lit, the blue LED 40b is turned on by gradually increasing the current, the chromaticity of the light is similarly measured by the color measuring device 39, and the output is received by the control device 50. . Next, on the basis of these measurement results, the control device 50 determines the current flowing through the white LED 40a and the current flowing through the blue LED 40b so that the chromaticity of the light emitted from the emission surface 36a of the light guide 36 approaches the target chromaticity 65. Determined by When the chromaticity of the light emitted from the white LED 40a is yellow, the current of the blue LED 40b is larger than that when the chromaticity of the light emitted from the white LED 40a is blue. Further, by controlling so as to decrease the current flowing through the white LED 40a according to the increased amount of current flowing through the blue LED 40b, the luminance of the light emitted from the emission surface 36a can be made constant.

  By configuring in this way, the chromaticity of the purchased white LED varies, and when the white LED having a different chromaticity must be used for each backlight 30, or when the chromaticity of the single backlight 30 is different. Even when a white LED must be used, the chromaticity of light emitted from the emission surface 36a of the light guide 36 of each backlight 30 can be set to the target chromaticity 65 or close thereto. Furthermore, since it is not necessary to reduce the current flowing through the white LED 40a, the luminance of the light emitted from the emission surface 36a is not reduced.

  In the present embodiment, the light source unit 33 may be disposed on only one of the side surfaces of the light guide 36 as shown in FIG. 3 or on both opposing side surfaces as shown in FIG. It may be. When arranged on both side surfaces, the arrangement and mixing ratio of the white LED 40a and the blue LED 40b in each light source unit 33 may be within a range that can be adjusted to the target chromaticity 65, and one light source unit 33 is white. Only the LED 40a and the other light source unit 33 may include only the blue LED 40b.

  The side surface on which the light source unit 33 is disposed is not limited to the short side surface of the light guide 36, and may be a long side surface as shown in FIG. It may be. By providing a plurality of light source sections 33, the luminance of light emitted from the emission surface 36 a of the light guide 36 can be improved. In particular, by arranging the LED 40 on the long side surface of the light guide 36, more LEDs 40 can be arranged than when arranged on the short side surface. Similarly, the light emitted from the output surface 36 a of the light guide 36. The brightness can be improved. Thus, the display quality of the liquid crystal display device 10 can be improved by improving the luminance of the light emitted from the emission surface 36a of the light guide 36.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a plan view of a backlight according to the second embodiment. The second embodiment is the same as the first embodiment except that the configuration of the backlight is different, and substantially the same parts are denoted by the same reference numerals.

  As shown in FIG. 9, the backlight 30 according to the second embodiment is a direct type including a substrate 32 on which the LEDs 40 are mounted, and is disposed on the back surface of the liquid crystal panel 20 as shown in FIG. The substrate 32 is approximately the same size as the liquid crystal panel 20. The LEDs 40 are arranged on the substrate 32 in a plane shape in the vertical and horizontal directions.

  Also in this embodiment, as in the first embodiment, the LED 40 is composed of a white LED 40a whose emitted light belongs to the white region 60 in the chromaticity diagram shown in FIG. 4 and a blue LED 40b that belongs to the blue region 62, and the white LED 40a. And the blue LED 40b are independently controlled by the control device 50 to adjust the luminance.

  The mixing ratio of the white LED 40a and the blue LED 40b may be any as long as the light emitted from the emission surface 36a can be adjusted to the target chromaticity 65 having a predetermined luminance. Here, it is preferable that the white LED 40a and the blue LED 40b are arranged as uniformly distributed as possible as shown in FIG. 9 in order to uniformly mix the light emitted from each.

  As in the first embodiment, the liquid crystal display device 10 includes a color measuring device 39 that measures the chromaticity of the light emitted from the LED 40 between the backlight 30 and the liquid crystal panel 20.

  In the present embodiment, the liquid crystal display device 10 first turns on only the white LED 40a with a predetermined current value under the control of the control device 50 when the power is turned on, as in the first embodiment, and the light measuring body is guided by the color measuring device 39. The chromaticity of the light emitted from the emission surface 36 a of 36 is measured, and the output is received by the control device 50. Subsequently, with the white LED 40a lit, the blue LED 40b is turned on by gradually increasing the current, the chromaticity of the light is similarly measured by the color measuring device 39, and the output is received by the control device 50. . Next, on the basis of these measurement results, the control device 50 determines the current flowing through the white LED 40a and the current flowing through the blue LED 40b so that the chromaticity of the light emitted from the emission surface 36a of the light guide 36 approaches the target chromaticity 65. Determined by

  By configuring in this way, the chromaticity of the purchased white LED varies as in the first embodiment, and when the white LED having a different chromaticity must be used for each backlight 30, one Even if it is necessary to use white LEDs having different chromaticities in the backlights 30, the chromaticity of light emitted from the emission surface 36 a of the light guide 36 of each backlight 30 may be close to the target chromaticity 65. It becomes possible. Furthermore, since many LEDs 40 can be arranged as compared with the sidelight system of the first embodiment, the luminance of the backlight 30 can be improved, and the display quality of the liquid crystal display device 10 can be further improved. Can do.

  In the present embodiment, FIG. 9 shows the case where the LEDs 40 are arranged in a rectangular lattice shape, but the arrangement method of the LEDs 40 is not limited to the rectangular lattice shape, and may be a square lattice shape, as shown in FIG. Thus, it may be a triangular lattice shape. When arranged in a triangular lattice shape, six LEDs 40 are adjacent to one LED 40. Therefore, when there are approximately the same number of white LEDs 40a and blue LEDs 40b, the white LEDs 40a or the blue LEDs 40b are adjacent to each other. I can't avoid it. In this case, in order to uniformly mix the light emitted from the white LED 40a and the blue LED 40b, the white LED 40a and the blue LED 40b are alternately arranged in at least one direction such as the horizontal direction in FIG. 10 (A direction in the figure). preferable. Further, when the number of white LEDs 40a and blue LEDs 40b is different, it is preferable to arrange the smaller LEDs 40 as equally as possible in the direction A and the direction perpendicular to the direction A in FIG. In any case, in order to more uniformly mix the light emitted from the white LED 40a and the blue LED 40b, it is preferable to arrange the white LED 40a and the blue LED 40b adjacent to each other as much as possible.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a schematic configuration diagram of an LED according to the third embodiment. The third embodiment is the same as the first embodiment or the second embodiment except that the configuration of the LEDs is different.

  As shown in FIG. 11, the LED 40 according to the present embodiment includes a frame body 42 made of a transparent resin, two sets of lead frames 43, terminals 44 connected to the respective lead frames 43, and white LED chips 41 a. And a blue LED chip 41b. The white LED chip 41a and the blue LED chip 41b are collectively referred to as the LED chip 41. Inside the frame body 42, the white LED chip 41a and the blue LED chip 41b are respectively connected to the lead frames 43 arranged on the left and right in the drawing by wirings 45. The wiring 45 is a bonding wire, and for example, a wire made of gold can be used. The terminal 44 is exposed to the outside of the frame body 42 and used to connect to the control device 50 and the adjacent LED 40. In FIG. 11, the frame body 42 shows a cross section. Note that the backlight 30 according to the present embodiment may be a sidelight type or a direct type.

  In the present embodiment, the light emitted from the white LED chip 41 a belongs to the white region 60 in the chromaticity diagram shown in FIG. 4, and the light emitted from the blue LED chip 41 b belongs to the blue region 62. The white LED chip 41a is, for example, an LED element that emits blue light when energized, and is sealed with a resin mixed with a phosphor that emits yellow light that is a complementary color of blue when irradiated with light. Are mixed and emits white light. The blue LED chip 41b is obtained by sealing, for example, an LED element that emits blue light when energized with a transparent resin.

  The white LED chip 41a and the blue LED chip 41b are independently controlled by the control device 50 to adjust the luminance. This is possible by connecting the white LED chip 41a and the blue LED chip 41b electrically independently to the control device 50. Since the white LED chip 41a and the blue LED chip 41b are connected to different terminals 44, for example, a white LED chip group in which only the white LED chip 41a is connected in series and a blue LED chip in which only the blue LED chip 41b is connected in series. LED chip groups can be provided, and each LED chip group can be directly connected to the control device 50. Note that a plurality of LED chip groups may be provided, or each LED chip group may be composed of one LED chip, that is, each LED chip may be independently controlled by the control device 50.

  In the present embodiment, the liquid crystal display device 10 first turns on only the white LED chip 41 a of the LED 40 under the control of the control device 50 when the power is turned on, and a color measuring device 39 provided between the backlight 30 and the liquid crystal panel 20. Thus, the chromaticity of the light emitted from the backlight 30 is measured, and the output is received by the control device 50. The color measuring device 39 is arranged at a position that does not interfere with the display of the liquid crystal panel 20. Subsequently, while the white LED chip 41a is lit, the blue LED chip 41b is turned on by gradually increasing the current, and the chromaticity of light is similarly measured by the color measuring device 39, and the output is controlled by the control device. Receive at 50. Next, based on these measurement results, the current that flows through the white LED chip 41a and the current that flows through the blue LED chip 41b so that the chromaticity of the light emitted from the emission surface 36a of the light guide 36 is close to the target chromaticity 65. Is determined by the control device 50.

  By configuring in this manner, the chromaticity of the purchased white LED chip varies, and when the white LED chip having a different chromaticity must be used for each backlight 30, or in a single backlight 30, a different color Even if a white LED chip of a certain degree is used, the chromaticity of light emitted from the emission surface 36a of the light guide 36 of each backlight 30 can be set to the target chromaticity 65 or a chromaticity close thereto.

  In the present embodiment, all the LEDs 40 may include white LED chips 41a and blue LED chips 41b, and some of the LEDs 40 include one or more of either white LED chips 41a or blue LED chips 41b. It may be a thing. Moreover, in LED40 provided with the white LED chip 41a and the blue LED chip 41b, as shown in the schematic block diagram of LED concerning another aspect of this embodiment of FIG. 12, the frame 42 is white LED chip 41a and blue You may have the partition 42a which divides LED chip 41b.

  In the first to third embodiments, the chromaticity of light emitted from the emission surface 36a of the light guide 36 is measured by the color measuring device 39 at any time during energization or operation of the liquid crystal display device 10, and the The control device 50 may adjust the current that flows through the white LED 40a and the blue LED 40b or the current that flows through the white LED chip 41a and the blue LED chip 41b based on the output. In this case, the current of the white LED 40a or the white LED chip 41a can be increased or the current of the blue LED 40b or the blue LED chip 41b can be decreased if the chromaticity of the light emitted from the emission surface 36a of the light guide 36 is biased to blue. If it is biased to yellow, the current of the blue LED 40b or the blue LED chip 41b may be increased or the current of the white LED 40a or the white LED chip 41a may be decreased.

  In the first to third embodiments, the color measurement device 39 is not provided, and the white LED 40a and the blue LED 40b are installed by a chromaticity measuring device installed so as to receive light emitted from the emission surface 36a when the backlight is manufactured. May be adjusted in advance, and the adjusted current value may be stored in the control device 50. As an adjustment method, for example, the current of the white LED 40a is turned on at a fixed value, and then the current of the blue LED 40b is adjusted while the chromaticity of the emission surface 36a is monitored by a chromaticity measuring device to emit light from the emission surface 36a. There is a method of adjusting the chromaticity so that the chromaticity is equal to or close to the target chromaticity 65.

1 is a schematic configuration diagram of a liquid crystal display device according to a first embodiment. The top view of the backlight concerning a 1st embodiment Front view of the backlight according to the first embodiment Chromaticity diagram showing white and blue areas The block diagram which shows the connection form of LED of 1st Embodiment, and a control apparatus. The block diagram which shows another connection form of LED of 1st Embodiment, and a control apparatus. The top view of the backlight concerning another mode of a 1st embodiment. The top view of the backlight concerning another mode of a 1st embodiment. The top view of the backlight concerning 2nd Embodiment The top view of the backlight concerning another mode of a 2nd embodiment. The schematic block diagram of LED concerning 3rd Embodiment Schematic configuration diagram of an LED according to another aspect of the third embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 20 Liquid crystal panel 30 Backlight 31 Frame 31a Lower frame 31b Upper frame 32 Board | substrate 33 Light source part 34 FPC
36 Light guide 36a Emission surface 37 Reflective sheet 38 Diffusion sheet 39 Color measuring device 40 LED
40a White LED
40b Blue LED
41 LED chip 41a White LED chip 41b Blue LED chip 42 Frame 42a Partition 43 Lead frame 44 Terminal 45 Wiring 50 Control device 60 White area 62 Blue area 65 Target chromaticity

Claims (8)

In an illumination device that includes an LED and a control device that controls light emission of the LED, and the emitted light is white,
The LED comprises a white LED and a blue LED, and the control device can independently control light emission of the white LED and the blue LED.   The lighting device according to claim 1, wherein the white LED and the blue LED are arranged adjacent to each other. In an illumination device that includes an LED and a control device that controls light emission of the LED, and the emitted light is white,
The LED includes a white LED chip and a blue LED chip, and the control device can independently control light emission of the white LED chip and the blue LED chip.   The said LED is provided with the frame surrounding the said white LED chip and the said blue LED chip, and the said frame has a partition which divides the said white LED chip and the said blue LED chip. Lighting equipment.   5. A plate-like light guide that emits light incident from a side surface from an output surface is provided, and the LEDs are arranged in a row on the side surface of the light guide. The lighting device described.   The lighting device according to claim 1, wherein the LEDs are arranged in a planar shape.   The color measurement device for measuring the chromaticity of the emitted light is provided, and the control device controls the light emission of the LED based on the output of the color measurement device. Lighting equipment.   A liquid crystal display device comprising: a liquid crystal panel; and the illumination device according to claim 1 disposed on a back surface of the liquid crystal panel.

Images