JP2007114276A - Lighting unit, electrooptical device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a desired color reproduction region and to reduce power consumption. <P>SOLUTION: A plurality of light sources which emit light beams of red (R), green (G) and blue (B), e.g. LEDs are used as lighting units of a liquid crystal display device. In a one-frame period, at least a light source which emits a light beam of one color among the plurality of light sources always illuminate and the chromaticity of a display screen of a display panel is adjusted to specified chromaticity by varying illumination periods of the plurality of light sources. Consequently, the plurality of light sources are made less in power consumption than when the plurality of light sources are supplied with constant currents to illuminate, and the display screen is prevented from decreasing in luminance, thereby providing image display natural to human's eyes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination device used in an electro-optical device such as a liquid crystal display device.

  An electro-optical device typified by a liquid crystal display device is a display such as a liquid crystal display panel including an illumination device that emits white light and color filters of three colors of red (R), green (G), and blue (B). Color display is performed by the panel. The illumination device illuminates the display panel by transmitting the emitted white light to the display panel. In such an illumination device, a plurality of light sources that emit light of each color of RGB, such as LEDs (Light Emitting Diodes), are used. The illuminating device can emit white light by combining the light of each color of RGB emitted from these light sources.

  However, when an LED is used as a light source and a constant current is passed through the LED to emit light, heat loss occurs inside the LED, and the life of the LED is shortened due to the heat loss. In the following Patent Document 1, the LEDs of each color of RGB used as the light source of the illumination device are caused to emit light in a time-sharing manner, thereby reducing power consumption and extending the life of the LEDs.

  In the case of an illuminating device that constitutes an electro-optical device in combination with a display panel, even if the illuminating device itself is the same, the color reproduction region on the display screen varies depending on the characteristics of the display panel used together. Therefore, in order to realize a desired color reproduction region on the display screen, it is necessary to adjust the emission color of the lighting device in consideration of the characteristics on the display panel side. In Patent Document 2, when LEDs of RGB colors are emitted in a time-sharing manner, the chromaticity on the display screen is adjusted by changing the pulse width of a current flowing through each LED. Furthermore, in patent document 3, the color reproducibility in a display screen is improved by providing both LED which emits white light, and LED corresponding to the color of low-intensity light.

JP 2004-93761 A JP 2004-93629 A Japanese Patent Laid-Open No. 2005-56842

  The present invention has been made in view of the above points. In an electro-optical device including a display panel and an illumination device, a desired color reproduction region is realized on a display screen and power consumption is reduced. Let it be an issue.

  In one aspect of the present invention, the electro-optical device includes a display panel and a plurality of light sources that emit red (R), green (G), and blue (B) colors, and the display panel includes the plurality of light sources. And an illumination device that illuminates the light emitted from the light source by transmitting the light source that emits light of at least one color among the plurality of light sources during one frame period. The chromaticity of the display screen of the display panel is adjusted to a predetermined chromaticity by changing the lighting period of each of the plurality of light sources.

  The electro-optical device is, for example, a liquid crystal display device, and includes a display panel such as a liquid crystal display panel and a lighting device. The lighting device includes a plurality of light sources that emit light of red (R), green (G), and blue (B). Here, for example, an LED is used as the light source. The illumination device illuminates the display panel by transmitting light emitted from the plurality of light sources. During one frame period, among the plurality of light sources, a light source that emits light of at least one color is always turned on, and the chromaticity of the display screen of the display panel is determined according to each lighting period of the plurality of light sources. By changing it, it is adjusted to a predetermined chromaticity. By doing so, it is possible to reduce the power consumption of the plurality of light sources and to prevent the brightness of the display screen from being lowered, and it is possible to display an image that is natural for human eyes. .

  In another aspect of the electro-optical device, the light source that emits blue light among the plurality of light sources has a lighting time of one light source that emits red light and green light during one frame period. Longer than the lighting time of the light source emitting light. When the display panel transmits white light from the lighting device, the display panel absorbs blue light components more than other color components. According to this aspect, it is possible to increase the luminance of blue light out of the light emitted from the lighting device. By doing so, it is possible to appropriately adjust the white balance of the electro-optical device.

  In another aspect of the electro-optical device, the display panel includes three sub-pixels each having a red (R), green (G), and blue (B) colored layer, and red. (R), green (G), and blue (B) are composed of four sub-pixels including a sub-pixel having a color layer having a color complementary to one of the colors. For example, the display panel is composed of four-color sub-pixels in which a sub-pixel of red (R), green (G), and blue (B) is added with a sub-pixel of cyan (C) that is complementary to red. In this case, the white balance tends to shift to the green side as compared with a display panel composed of RGB sub-pixels. For such a display panel, the illumination device capable of increasing the luminance of blue light is particularly suitable.

  In another aspect of the present invention, an electronic apparatus including the above-described electro-optical device in a display portion can be configured.

  In still another aspect of the present invention, the lighting device includes a plurality of light sources that emit red (R), green (G), and blue (B) colors, and the plurality of light sources are always in one frame period. Among the light sources, a light source that emits light of at least one color is turned on, and the chromaticity of the mixed light emitted from the plurality of light sources is turned on for each of the plurality of light sources during one frame period. By changing the period, it is adjusted to a predetermined chromaticity. This can also reduce the power consumption of the plurality of light sources, and can also prevent the luminance of the mixed light from being emitted from the plurality of light sources from being lowered.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Configuration of liquid crystal display device]
First, the configuration and the like of the liquid crystal display device 100 according to the present embodiment will be described with reference to FIGS.

  FIG. 1 is a plan view schematically showing a schematic configuration of a liquid crystal display device 100 according to the present embodiment. In FIG. 1, a color filter substrate 92 is disposed on the front side (observation side) of the paper, and an element substrate 91 is disposed on the back side of the paper. In FIG. 1, the vertical direction (column direction) on the paper surface is defined as the Y direction, and the horizontal direction (row direction) on the paper surface is defined as the X direction. In FIG. 1, each region corresponding to R (red), G (green), B (blue), and C (cyan) represents one subpixel SG, and R, G, B, and C A corresponding 1 × 4 sub-pixel SG represents one display pixel AG.

  FIG. 2 is an enlarged cross-sectional view of one display pixel AG along the cutting line AA ′ in the liquid crystal display device 100. As shown in FIG. 2, the liquid crystal display device 100 includes a liquid crystal display panel 30 and a lighting device 10. In the liquid crystal display panel 30, an element substrate 91 and a color filter substrate 92 disposed to face the element substrate 91 are bonded together via a frame-shaped sealing material 5, and liquid crystal is enclosed inside the sealing material 5. Thus, the liquid crystal layer 4 is formed. The liquid crystal used for the liquid crystal layer 4 is, for example, a TN (Twisted Nematic) type liquid crystal. The illumination device 10 is provided on the outer surface of the element substrate 91 of the liquid crystal display panel 30.

  The liquid crystal display device 100 according to the present embodiment is a liquid crystal display device for color display configured using four colors of RGBC, and is active using an α-Si TFT (Thin Film Transistor) element as a switching element. This is a matrix driving type liquid crystal display device.

  A planar configuration of the element substrate 91 will be described. On the inner surface of the element substrate 91, a plurality of source lines 32, a plurality of gate lines 33, a plurality of α-Si TFT elements 37, a plurality of pixel electrodes 34, a driver IC 40, an external connection wiring 35, and an FPC ( Flexible Printed Circuit) 41 or the like is formed or mounted.

  As shown in FIG. 1, the element substrate 91 has a protruding region 31 that protrudes outward from one side of the color filter substrate 92, and a driver IC 40 is mounted on the protruding region 31. A terminal (not shown) on the input side of the driver IC 40 is electrically connected to one end side of the plurality of external connection wirings 35, and the other end side of the plurality of external connection wirings 35 is electrically connected to the FPC 41. It is connected. Each source line 32 is formed so as to extend in the Y direction and at an appropriate interval in the X direction, and one end side of each source line 32 is connected to an output side terminal (not shown) of the driver IC 40. Electrically connected.

  Each gate line 33 includes a first wiring 33a formed so as to extend in the Y direction, and a second wiring 33b formed so as to extend in the X direction from the terminal portion of the first wiring 33a. ing. The second wiring 33 b of each gate line 33 is formed to extend in the direction intersecting each source line 32, that is, in the X direction and at an appropriate interval in the Y direction. One end of one wiring 33a is electrically connected to a terminal (not shown) on the output side of the driver IC 40. An α-TFT element 37 is provided at a position corresponding to the intersection of each source line 32 and each gate line 33 with the second wiring 33 b, and each α-TFT element 37 includes each source line 32, each gate line 33, and each gate line 33. It is electrically connected to each pixel electrode 34 and the like. Each α-TFT element 37 and each pixel electrode 34 are provided at positions corresponding to each sub-pixel SG on the substrate 1 such as glass. Each pixel electrode 34 is formed of a transparent conductive material such as ITO (Indium-Tin Oxide).

  A region in which a plurality of display pixels AG are arranged in a matrix in the X and Y directions is an effective display region V (a region surrounded by a two-dot chain line). In the effective display area V, images such as letters, numbers, and figures are displayed. The area outside the effective display area V is a frame area 38 that does not contribute to display. An alignment film (not shown) is formed on the inner surface of each source line 32, each gate line 33, each α-TFT element 37, each pixel electrode 34, and the like.

  Next, the planar configuration of the color filter substrate 92 will be described. As shown in FIG. 2, the color filter substrate 92 is formed on a substrate 2 such as glass on a light shielding layer (generally called “black matrix”, hereinafter simply abbreviated as “BM”), R, G, B , C color layers 6R, 6G, 6B, 6C, the common electrode 8, and the like. The BM is formed at a position that partitions the sub-pixels SG for each color. In the following description or drawings, when a component is indicated without specifying the RGBC color, it is simply written as “colored layer 6”, and when the component is indicated by distinguishing the RGBC color, For example, it is written as “colored layer 6R”. The RGBC color subpixels SG have RGBC colored layers 6R, 6G, 6B, and 6C, respectively. The RGBC colored layers 6R, 6G, 6B, and 6C function as color filters for the respective colors. The common electrode 8 is made of a transparent conductive material such as ITO like the pixel electrode, and is formed over substantially the entire surface of the color filter substrate 92. The common electrode 8 is electrically connected to one end side of the wiring 36 in the corner area E1 of the sealing material 5, and the other end side of the wiring 36 is electrically connected to an output terminal corresponding to the COM of the driver IC 40. It is connected to the.

  Next, the illumination device 10 will be described. The lighting device 10 includes a light guide plate 11 and a light source unit 12. The light source unit 12 emits light L to the end surface 11 c of the light guide plate 11. As will be described in detail later, the light source unit 12 includes a plurality of RGB LEDs 13R, 13G, and 13B serving as point light sources. The light L emitted from the light source unit 12 is a mixture of the lights emitted from the LEDs 13R, 13G, and 13B of RGB colors.

  Light L emitted from the light source unit 12 enters the light guide plate 11 through an end surface (hereinafter referred to as “light incident end surface”) 11 c of the light guide plate 11, and is repeatedly reflected on the light output surface 11 a and the reflection surface 11 b of the light guide plate 11. Thus, when the direction is changed and the angle formed between the light exit surface 11a of the light guide plate 11 and the light L exceeds the critical angle, the light exit surface 11a of the light guide plate 11 passes through the optical sheet (not shown) as illumination light L to the liquid crystal display panel 30. Each emits light. The liquid crystal display device 100 is illuminated by the light L passing through the liquid crystal display panel 30. Thereby, the liquid crystal display device 100 can display images, such as a character, a number, and a figure, and an observer can visually recognize an image.

  In the liquid crystal display device 100, G1, G2,..., Gm−1, Gm (m is a natural number) are generated by the driver IC 40 based on the signal and power from the FPC 41 side connected to the main board or the like of the electronic device. The gate lines 33 are sequentially selected one by one in order, and a gate signal of a selection voltage is supplied to the selected gate lines 33, while the other non-selected gate lines 33 are not selected. A voltage gate signal is provided. Then, the driver IC 40 applies source signals corresponding to display contents to the pixel electrodes 34 located at positions corresponding to the selected gate lines 33, respectively, corresponding S1, S2,..., Sn-1, Sn ( n is a natural number) and is supplied through the α-TFT element 37. As a result, the alignment state of the liquid crystal layer 4 is controlled, and the display state of the liquid crystal display device 100 is switched to the non-display state or the intermediate display state.

  Although the liquid crystal display device 100 according to the present embodiment is shown as a completely transmissive liquid crystal display device, the present invention is not limited to this, and a transflective liquid crystal display device may be used instead. The liquid crystal display panel 30 uses the α-TFT element 37 as a switching element. However, the liquid crystal display panel 30 is not limited to this, and a polysilicon TFT or a TFD (Thin Film Diode) element may be used instead.

  Further, the liquid crystal display panel 30 is not limited to a liquid crystal display panel having a liquid crystal layer made of TN liquid crystal as described above. Instead, a VA (Vertical Alignment) method, an IPS (In Plane Switching) method, an FFS (Fringe) is used. It is also possible to use a liquid crystal display panel such as a field structure.

[Configuration of lighting device]
Next, the illumination device 10 according to the present embodiment will be described in detail. FIG. 3A shows a plan view of the illumination device 10 according to the present embodiment. As described above, the light L emitted from the light source unit 12 is a mixture of the lights emitted from the LEDs 13R, 13G, and 13B of each color of RGB. As shown in FIG. 3A, the light source unit 12 includes a plurality of RGB LEDs 13R, 13G, and 13B of the same number. Each of the RGB LEDs 13R, 13G, and 13B emits light when a current is applied. The luminous intensity of the light emitted from each of the RGB LEDs 13R, 13G, and 13B varies depending on the magnitude of the current that flows. In addition, as the illuminating device 10 which concerns on this embodiment, it is not restricted to what is shown to Fig.3 (a). Instead, as shown in FIG. 3B, a plurality of LEDs 13RGB that can emit light of each color of RGB with one LED may be used. LED13RGB is one LED, and light emitting elements of each color of RGB are incorporated therein. With respect to the light emitting elements of each color of RGB, currents can be separately supplied to emit light.

  FIG. 4 shows a schematic diagram of the light source unit 12 in the case where the illumination device 10 is in the mode shown in FIG. In FIG. 4, as an example, it is assumed that the LEDs 13R, 13G, and 13B for each color of RGB are provided in the light source unit 12 two by two. That is, as shown in FIG. 4, the light source unit 12 includes two red LEDs 13R, red LEDs 13R1 and 13R2, two green LEDs 13G, green LEDs 13G1 and 13G2, and two blue LEDs 13B that are blue. Assume that LEDs 13B1 and 13B2 are provided.

  The red LEDs 13R1 and 13R2 are electrically connected in series. The red LEDs 13R1 and 13R2 connected in series are supplied with a current Ir by the red LED driving circuit 51R. FIG. 4 shows the flow of current flowing through the red LEDs 13R1 and 13R2 with solid arrows. As a result, the current Ir flows through the red LEDs 13R1 and 13R2, and the red LEDs 13R1 and 13R2 can both emit red light having the same luminous intensity.

  FIG. 4 also shows the flow of currents flowing through the green LEDs 13G1 and 13G2 and the blue LEDs 13B1 and 13B2 by broken line arrows.

  The green LEDs 13G1 and 13G2 are electrically connected in series. The green LEDs 13G1 and 13G2 connected in series are supplied with a current Ig by the green LED driving circuit 51G. Thereby, the current Ig flows in both the green LEDs 13G1 and 13G2, and both the green LEDs 13G1 and 13G2 can emit green light having the same luminous intensity.

  The blue LEDs 13B1 and 13B2 are also electrically connected in series. The two blue LEDs 13B1 and 13B2 connected in series are supplied with a current Ib by the blue LED driving circuit 51B. Thereby, the current Ib flows through both the blue LEDs 13B1 and 13B2, and both the blue LEDs 13B1 and 13B2 can emit blue light having the same luminous intensity.

  FIG. 5 shows a circuit diagram of a red LED drive circuit 51R according to the present embodiment as an example. The red LED drive circuit 51R includes a current limiting resistor Rr and a power source Vr. The magnitude of the current limiting resistor Rr is determined by the allowable value of the current Ir that can be passed through the red LEDs 13R1 and 13R2. The power supply Vr supplies a pulse current to the red LEDs 13R1 and 13R2. The width and timing of the pulse current supplied to the red LEDs 13R1 and 13R2 can be changed by controlling the power supply Vr. Each of the green LED drive circuit 51G and the blue LED drive circuit 51B also supplies a pulse current to each of the green LEDs 13G1 and 13G2 and the blue LEDs 13B1 and 13B2 that are electrically connected in the same manner as the red LED drive circuit 51R. Each has a power supply.

  As can be seen from the above, in the light source unit 12 according to the present embodiment, the RGB LEDs 13 each have an LED drive circuit 51 for each color. The LED drive circuit 51 connected to each color LED 13 has a power source that supplies and controls a pulse current to each color LED 13 that is electrically connected. Thus, by providing the LED drive circuit for each LED of each color, it is possible to apply a pulse current separately for each LED of each color.

  Even in the case where the illumination device 10 is in the mode shown in FIG. 3B, an LED drive circuit is provided for each light emitting element of the LED 13RGB, and a pulse current can be applied separately to each.

[Driving method of lighting device]
Next, a method for driving the illumination device 10 will be described. As described above, in the illumination device 10, the light source 12 emits light L by applying a pulse current to each LED 13 of each color.

  In a liquid crystal display device having a general RGB colored layer, the light transmittance of the colored layer in the liquid crystal display panel varies depending on the thickness of the colored layer, etc., so that the light emitted from the LED passes through the colored layer. As a result, the light intensity of each color of RGB changes. Therefore, even if predetermined white light is generated on the lighting device side, the color of the white light after passing through the colored layer is not always the same as the color of the predetermined white light. In other words, when white display is performed on the display screen, the white color visually recognized by the observer is not always the same as the color of the predetermined white light generated on the lighting device side. In this way, since the ratio of the light intensity of each color of RGB constituting the white light changes depending on the transmittance of the colored layer, the observer can select the white color displayed on the display screen and the predetermined light generated on the lighting device side. It looks different from the color of white light. In particular, among light of each color of RGB, blue light is absorbed most by the colored layer. Therefore, in a liquid crystal display device having a general RGB colored layer, the illuminating device needs to generate white light in which the blue light component is increased.

  In addition, when white display is performed on the liquid crystal display panel 30 having the RGBC colored layer 6 as in the liquid crystal display device 100 according to the present embodiment, it is compared with a liquid crystal display device having a general RGB colored layer. Then, since the C colored layer 6C is added, the white balance tends to shift to the green side. Therefore, the illuminating device 10 needs to generate white light having a larger blue light component than the illuminating device in a liquid crystal display device having a general RGB colored layer.

  FIG. 6 is a timing chart showing a driving sequence of each color LED 13 in the illumination device 10 according to the present embodiment. In FIG. 6, “ON” of each color LED 13 indicates a lighting state, and “OFF” indicates a light-off state. For example, referring to FIG. 4, when the red LED 13R is “ON”, both the red LEDs 13R1 and 13R2 are lit, and when the red LED 13R is “OFF”, both the red LEDs 13R1 and 13R2 are turned off. In FIG. 6, when the green LED 13G and the blue LED 13B are turned “ON” and “OFF”, both the green LEDs 13G1 and 13G2 and the blue LEDs 13B1 and 13B2 are both turned on and off.

  In the illuminating device 10 which concerns on this embodiment, LED13 of each color becomes a structure which lights in a time division manner. Specifically, as shown in FIG. 6, among the three colors of RGB LEDs 13, the period in which the blue LED 13 </ b> B is “ON” is the longest in one frame period. Hereinafter, a period in which the LEDs 13 of each color are “ON” is referred to as a lighting period, and a period in which the LEDs 13 of each color are “OFF” is referred to as a non-lighting period. The chromaticity of the light L emitted from the illuminating device 10 and the chromaticity of the display screen of the liquid crystal display panel 30 are adjusted to a predetermined chromaticity by changing the lighting period of the LEDs 13 for each color of RGB during one frame period. The By doing in this way, the lighting time of LED13 of each color of RGB can be shortened rather than supplying constant current to LED13 of each color of RGB and always lighting, and reduction of power consumption can be aimed at.

  Generally, since one frame period is about 1/60 second, even if the LEDs 13 of each color are lit in a time-sharing manner, the color change is not recognized by human eyes due to the afterimage effect. . When the LEDs 13 of each color are lit in a time-division manner, the color of the light L looks different to the human eye depending on the period during which the LEDs 13 of each color are lit. Specifically, in the color of the light L, the color component of the light emitted from the LED 13 having a long lighting period is dark and the color component of the light emitted from the LED 13 having a short lighting period is one frame period. getting thin. For example, in the lighting device 10 according to the present embodiment, the light L is a bluish white since the lighting period of the blue LED 13B is the longest among the three colors of RGB LEDs 13 in one frame period. Looks like light.

  Therefore, since the C colored layer 6C is added to the liquid crystal display panel 30, the lighting device 10 can turn on the blue LED 13B among the RGB three-color LEDs 13 even if the white balance is shifted to the green side. Is made the longest, the luminance of the blue light in the light L can be increased, and the white balance in the liquid crystal display panel 30 can be appropriately adjusted. Even when the illumination device 10 of the present invention is used as the illumination device of a liquid crystal display device having a general RGB colored layer, the illumination device 10 of the present invention can increase the luminance of blue light. Needless to say, it is useful for making appropriate adjustments to the white balance.

  In FIG. 6, it is assumed that the lighting period of the red LED 13R is longer than the lighting period of the green LED 13G. However, the present invention is not limited to this. Instead, the lighting period of the green LED 13G may be longer than the lighting period of the red LED 13R or may be the same as the lighting period of the red LED 13R. In short, since it is necessary to increase the luminance of the blue light in the light L, the lighting period of the blue LED 13B only needs to be longer than the lighting period of the red LED 13R and the lighting period of the green LED 13G. Strictly speaking, it is preferable that the lighting period of the red LED 13R is longer than the lighting period of the green LED 13G. This is because, as described above, in the liquid crystal display device 100 having the RGBC colored layer 6, the white balance tends to shift to the green side. Therefore, in the light L emitted from the illumination device 10, red light is emitted. This is because it is more appropriate to reduce the green light component than the component in order to prevent the white balance from shifting to the green side.

  Further, in FIG. 6, there is no period (hereinafter, simply referred to as “RGB non-lighting period”) in which all the LEDs 13 of RGB are in a non-lighting state in one frame period. If there is an RGB non-lighting period, the display screen becomes dark during the RGB non-lighting period. Therefore, the presence of the RGB non-lighting period causes flickering for human eyes. Therefore, in the drive sequence of FIG. 6, there is no period in which all the RGB LEDs 13 are turned off in one frame period, and at least one of the RGB LEDs 13 is always turned on. . By doing in this way, the illuminating device 10 can prevent the brightness | luminance of the light L and the brightness | luminance of a display screen falling, and can perform a natural image display for human eyes.

  In summary, in the lighting device 10, at least one of the RGB LEDs 13 is always turned on in one frame period, and the chromaticity of the light L emitted from the lighting device 10 and the liquid crystal display panel 30. The chromaticity of the display screen is adjusted to a predetermined chromaticity by changing the lighting period of the LEDs 13 of the respective colors RGB. In this way, not only can the power consumption of the RGB LEDs 13 be reduced, but also the luminance of the light L and the luminance of the display screen can be prevented from decreasing, which is natural for the human eye. Image display can be performed. In addition, the lighting device 10 can increase the luminance of blue light in the light L by making the lighting period of the blue LED 13 </ b> B the longest among the three colors of LEDs 13 of RGB, and the white balance of the liquid crystal display panel 30 can be increased. Appropriate adjustments can be made.

(Modification)
7 and 8 are modified timing charts showing the driving sequence of the LEDs 13 of the respective colors in the illumination device 10 according to the present embodiment. The drive sequences in FIGS. 7 and 8 are configured such that, during one frame period, one of the RGB LEDs 13 is turned on at the timing before one of the LEDs 13 is turned off. In the drive sequence of FIG. 7, first, the red LED 13R is turned on, and the blue LED 13B is turned on before the red LED 13R is turned off. Then, the green LED 13G is turned on before the blue LED 13B is turned off. In the drive sequence of FIG. 8, first, the green LED 13G is turned on, and the red LED 13R is lit before the green LED 13G is turned off. Then, the blue LED 13B is turned on before the red LED 13R is turned off. As described above, even in the case of the drive sequences of FIGS. 7 and 8, there is no period in which all the LEDs of each RGB color are turned off during one frame period. Among them, since at least one light is turned on, the lighting device 10 can prevent the brightness of the display screen from being lowered, and can perform image display that is natural to human eyes.

[Application example]
In the liquid crystal display panel 30 according to the present embodiment, one display pixel is composed of four color sub-pixels each having four color layers of RGBC. However, the present invention is not limited to this. Assume that one display pixel is configured by adding a sub-pixel having a color layer of a color complementary to any one of RGB to three-color sub-pixels each having an RGB color layer. You can also. That is, in the liquid crystal display panel according to the present embodiment, a C colored layer having a complementary color relationship with R is used, but a magenta (M) colored layer having a complementary color relationship with G is used instead of the C colored layer. Alternatively, a yellow (Y) colored layer having a complementary color relationship with B may be used. Even in this case, the illuminating device 10 can appropriately adjust the white balance in the liquid crystal display panel 30 by making the lighting period of the blue LED 13B the longest among the LEDs 13 of the three colors RGB.

  Furthermore, in this embodiment, a liquid crystal display panel is used as the display panel, but the present invention is not limited to this, and another display panel such as an electrophoretic display panel may be used instead. .

[Other embodiments]
In the above description, RGBC has been described as the color (colored region) of the colored layer that functions as a color filter. However, the application of the present invention is not limited to this, and one pixel is formed by other four colored regions. It can also be configured.

  In this case, the four-color colored region is a blue-colored colored region (also referred to as a “first colored region”) or a red-based color region in a visible light region (380 to 780 nm) whose hue changes according to the wavelength. Colored areas (also referred to as “second colored areas”) and two colored areas selected from hues from blue to yellow (“third colored areas”, “fourth colored areas”) "). Here, the term “system” is used. For example, if it is a blue system, the color is not limited to a pure blue hue, and includes a blue-violet color, a blue-green color, and the like. If it is a red hue, it is not limited to red but includes orange. These colored regions may be composed of a single colored layer, or may be composed of a plurality of colored layers having different hues. In addition, although these colored regions are described in terms of hue, the hue can be set by changing the saturation and lightness as appropriate.

The specific hue range is
-The colored region of the blue hue is from violet to blue-green, more preferably from indigo to blue.
-The colored region of red hue is from orange to red.
-One coloring area | region selected by the hue from blue to yellow is blue to green, More preferably, it is blue green to green.
-The other coloring area | region selected by the hue from blue to yellow is green to orange, More preferably, it is green to yellow. Or it is green to yellowish green.

  Here, the same hue is not used for each colored region. For example, when a green hue is used in two colored regions selected from hues of blue to yellow, the other uses a blue or yellowish green hue for one green.

  Thereby, a wider range of color reproducibility than the conventional RGB colored region can be realized.

In the above description, a wide range of color reproducibility by the colored areas of four colors is described in terms of hue, but the following is expressed in terms of the wavelength of light transmitted through the colored areas.
The blue colored region is a colored region having a wavelength peak of light transmitted through the colored region at 415 to 500 nm, preferably at 435 to 485 nm.
The red colored region is a colored region having a wavelength peak of light transmitted through the colored region of 600 nm or more, and preferably a colored region of 605 nm or more.
-One colored region selected by hue from blue to yellow is a colored region having a wavelength peak of 485-535 nm of light transmitted through the colored region, preferably a colored region having a wavelength of 495-520 nm. .
The other colored region selected with a hue from blue to yellow is a colored region having a wavelength peak of light transmitted through the colored region of 500-590 nm, preferably 510-585 nm, or 530- This is a colored region at 565 nm.

Further, when the four colored regions are expressed by an x, y chromaticity diagram, the following is obtained.
The blue colored region is a colored region where x ≦ 0.151 and y ≦ 0.056, and preferably a colored region where 0.134 ≦ x ≦ 0.151 and 0.034 ≦ y ≦ 0.056.
The red colored region is a colored region satisfying 0.643 ≦ x and y ≦ 0.333, and preferably a colored region satisfying 0.643 ≦ x ≦ 0.690 and 0.299 ≦ y ≦ 0.333.
-One colored region selected by hue from blue to yellow is a colored region where x ≦ 0.164 and 0.453 ≦ y, preferably a colored region where 0.098 ≦ x ≦ 0.164 and 0.453 ≦ y ≦ 0.759 is there.
The other colored region selected with a hue from blue to yellow is a colored region in the range of 0.257 ≦ x, 0.606 ≦ y, preferably a colored region in the range of 0.257 ≦ x ≦ 0.357, 0.606 ≦ y ≦ 0.670 is there.

  These four colored areas can be applied within the above-described range when the sub-pixel includes a transmission area and a reflection area.

  In addition, when the colored region of 4 colors in this example is used, you may use a fluorescent tube, organic EL, etc. other than the above-mentioned LED as a RGB light source for a backlight.

However, the following are preferable as the RGB light source.
・ B is the wavelength peak of emitted light at 435 nm to 485 nm ・ G is the wavelength peak of emitted light at 520 nm to 545 nm ・ R is the wavelength peak of emitted light at 610 nm to 650 nm And if a color filter is appropriately selected according to the wavelength of the RGB light source, a wider range of color reproducibility can be obtained.

  Moreover, you may use the light source which has a some peak so that a wavelength may come to a peak at 450 nm and 565 nm, for example.

Specific examples of the configuration of the above four colored regions include the following.
・ Colored areas of red, blue, green, cyan (blue green) ・ Colored areas of red, blue, green, and yellow ・ Colored areas of red, blue, dark green, and yellow ・ Hue Red, blue, emerald, yellow colored areas / hues are red, blue, dark green, yellow green colored areas / hues are red, blue green, dark green, yellow green colored areas
[Electronics]
Next, an embodiment in which the liquid crystal display device according to this embodiment is used as a display device of an electronic apparatus will be described.

  As the image signal input to the liquid crystal display device 100 according to the present embodiment, for example, RGBC color image signals may be directly input from the outside, or RGB image signals may be input from the outside. Then, it may be converted into RGBC color image signals.

  Here, in the liquid crystal display device 100, a case will be described in which image signals of each color of RGB are converted into image signals of each color of RGBC.

  FIG. 9 is a circuit block diagram of a schematic configuration showing the overall configuration of the present embodiment. An electronic apparatus shown here includes the liquid crystal display device 100 and a control unit 610. The control unit 610 includes a display information output source 611, a display image conversion circuit 612, and a timing generator 614.

  In the liquid crystal display device 100, when the input RGB color image signals are converted into RGBC color image signals, the display image conversion circuit 612 is output from an external display image output source 611 such as a personal computer. It has a function of converting RGB image signals into RGBC image signals and outputting them to the liquid crystal display panel 30.

  The display image conversion circuit 612 includes an arithmetic processing unit 612a such as a CPU (Central Processing Unit) and a storage unit 612b such as a RAM (Random Access Memory). The arithmetic processing unit 612a converts the RGB image signals 61R, 61G, 61B of the input image output from the display image output source 611 into RGBC color image signals 62R, 62G, 62B, 62C. The storage unit 612b is provided with an LUT (Look Up Table) in which image signals of RGB colors having a predetermined intensity are associated with image signals of RGBC colors having a corresponding intensity. For example, when RGB image signals for displaying only C color are input to the arithmetic processing unit 612a, for example, R = 0, G = 100, B = 100 intensity RGB image signals are input, The arithmetic processing unit 612a stores the RGBC color image signals (for example, R = 0, G = 10, B = 10, C = 100) having the intensity corresponding to the intensity of the RGB color image signals, and the storage unit 612b. The obtained RGBC color image signals are output to the liquid crystal display panel 30. As a result, not only the RGB colors but also the C color can be displayed on the display screen of the liquid crystal display panel 30. In this way, even when an RGB image signal is input as the image signal of the input image, the color reproduction range of the output image can be expanded to the cyan color reproduction range.

  The timing generator 614 has a hard switch or a soft switch for switching the timing mode, and generates the clock signal CLK from the luminance signal of the image signal. The driving sequence of the LED driving circuit 51 for each color of RGB described above is controlled so as to match the clock signal CLK determined by the timing generator 614.

  Next, a specific example of an electronic apparatus to which the liquid crystal display device 100 according to this embodiment can be applied will be described with reference to FIG.

  First, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a portable personal computer (so-called notebook personal computer) will be described. FIG. 10A is a perspective view showing the configuration of this personal computer. As shown in the figure, a personal computer 710 includes a main body 712 having a keyboard 711 and a display 713 to which the liquid crystal display device 100 according to the present invention is applied.

  Next, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a mobile phone will be described. FIG. 10B is a perspective view showing the configuration of this mobile phone. As shown in the figure, the cellular phone 720 includes a plurality of operation buttons 721, a reception port 722, a transmission port 723, and a display unit 724 to which the liquid crystal display device 100 according to the present invention is applied.

  Note that, as an electronic device to which the liquid crystal display device 100 according to the present invention can be applied, in addition to the personal computer shown in FIG. 10A and the mobile phone shown in FIG. Type / monitor direct-view type video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, videophone, POS terminal, digital still camera, etc.

It is a top view of the liquid crystal display device concerning this embodiment. It is sectional drawing of the liquid crystal display device which concerns on this embodiment. It is a top view of the illuminating device 10 which concerns on this embodiment. It is a schematic diagram of the light source part of the illuminating device which concerns on this embodiment. It is a circuit diagram of the LED drive circuit which concerns on this embodiment. 5 is a timing chart showing an LED driving sequence. 5 is a timing chart showing an LED driving sequence. 5 is a timing chart showing an LED driving sequence. 1 is a circuit block diagram of an electronic apparatus to which a liquid crystal display device according to an embodiment is applied. It is a figure which shows the example of the electronic device to which the liquid crystal display device of this embodiment is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 Light guide plate, 12 Light source part, 13 LED, 10 Illumination device, 30 Liquid crystal display panel, 100 Liquid crystal display device

Claims (5)

A display panel;
An illumination device having a plurality of light sources that emit red (R), green (G), and blue (B) light, and illuminating the display panel by transmitting light emitted from the plurality of light sources; With
During one frame period, among the plurality of light sources, a light source that emits light of at least one color is always turned on, and the chromaticity of the display screen of the display panel is determined according to each lighting period of the plurality of light sources. An electro-optical device that is adjusted to a predetermined chromaticity by changing.   Among the plurality of light sources, a light source that emits blue light has a lighting period longer than a lighting period of a light source that emits red light and a lighting period of a light source that emits green light in one frame period. The electro-optical device according to claim 1.   In the display panel, one display pixel has three sub-pixels each having a red (R), green (G), and blue (B) colored layer, and red (R), green (G), and blue (B The electro-optical device according to claim 2, wherein the electro-optical device includes four sub-pixels including a sub-pixel having a color layer having a complementary color relationship with any one color.   An electronic apparatus comprising the electro-optical device according to claim 1 in a display unit. A plurality of light sources that emit red (R), green (G), and blue (B) colors;
During one frame period, among the plurality of light sources, a light source that emits light of at least one color is always turned on, and the chromaticity of the light that is emitted from the plurality of light sources and mixed is one frame period. A lighting device, wherein the lighting device is adjusted to a predetermined chromaticity by changing a lighting period of each of the plurality of light sources.

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