JP2009198754A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which does not cause a user to feel the light from a backlight dazzling when an electric source is turned on in a pitch-dark room and is preferable for the protection of eyes. <P>SOLUTION: The liquid crystal display device provided with a liquid crystal display panel and a backlight disposed on the back surface of the liquid crystal display panel, further has a detection means for detecting an ambient illuminance and, when it is detected that the surrounding of the liquid crystal display device is dark, the luminance of the backlight is gradually raised to a set luminance upon the lighting of backlight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, for example, a liquid crystal display device incorporated in a television or the like.

  The liquid crystal display device is usually configured to include a liquid crystal display panel and a backlight disposed on the back surface of the liquid crystal display panel. Since the liquid crystal display panel is driven so that the light transmittance changes in each pixel and does not emit light, the backlight is required.

  For this reason, in the liquid crystal display device, the image displayed on the liquid crystal display panel can be recognized by the lighting of the backlight.

When a power switch is turned on for a television set or the like that incorporates such a liquid crystal display device, the lighting of the backlight is generally controlled so as to suddenly rise to a preset brightness, for example. Is. The following Patent Document 1 discloses an example of such control.
Japanese Patent Laid-Open No. 7-13128

  The above-described brightness setting for a sudden rise immediately after the backlight is turned on assumes that the liquid crystal display device is used in a bright environment.

  However, in the liquid crystal display device having such a sharp rising brightness setting, when the power switch is turned on (turned on) in a dark room, that is, in an environment with low ambient illumination, the difference between the ambient illumination and the backlight brightness is reduced. Becomes very intense, and viewers feel the light from the backlight dazzling, which is not preferable for eye protection.

  An object of the present invention is to provide a liquid crystal display device that is easy for viewers to see when the power is turned on in a situation where ambient illumination is low.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

(1) A liquid crystal display device comprising a liquid crystal display panel and a backlight on the back of the liquid crystal display panel, wherein a detection means for detecting ambient illuminance, and the surrounding of the liquid crystal display device being dark by the detection means When detected, when the backlight is turned on, the luminance signal to the backlight is input so as to rise up to a set luminance with a gradient.

(2) In (1), the backlight performs a preliminary lighting operation in which the brightness of the backlight is once increased and then lowered before the brightness of the backlight is increased with a gradient.

(3) In (2), when the detection means detects that the periphery of the liquid crystal display device is bright, the backlight emits light with a set luminance after the preliminary lighting operation.

(4) In (2), input of a display signal to the liquid crystal display panel is started after the preliminary lighting operation.

(5) In (2), input of a display signal to the liquid crystal display panel starts after the power is turned on.

(6) In (1), the time for raising the luminance of the backlight with a gradient is set to 10 seconds or more.

  In addition, this invention is not limited to the above structure, A various change is possible in the range which does not deviate from the technical idea of this invention. Further, examples of the configuration of the present invention other than the above-described configuration will be clarified from the entire description of the present specification or the drawings.

(7) A liquid crystal display device comprising a liquid crystal display panel and a backlight on the back of the liquid crystal display panel, wherein the backlight is turned on at a set luminance when power is turned on, and a display signal is input to the liquid crystal display panel The signal is input so as to rise with a gradient to the set signal value.

  According to the present invention, it is possible to provide a liquid crystal display device having a preferable configuration in terms of eye protection, even when used in a completely dark room, light from the backlight is not felt dazzling.

  Other effects of the present invention will become apparent from the description of the entire specification.

  Embodiments of a liquid crystal display device according to the present invention will be described below with reference to the drawings.

<Example 1>
FIG. 2 shows a liquid crystal display panel PNL configured as a module (liquid crystal display module LDM), an optical sheet OS, and a backlight BL in the liquid crystal display device according to the present invention, which are sequentially arranged from the viewer side.

  Note that the liquid crystal display panel PNL, the optical sheet OS, and the backlight BL are modularized by a plurality of frames (not shown).

  The liquid crystal display panel PNL includes a pair of parallel substrates SUB1 and SUB2 made of glass, for example, as an envelope, and a liquid crystal is sandwiched between the substrates SUB1 and SUB2.

  Pixels (not shown) arranged in a matrix are formed on the surface of the substrates SUB1 and SUB2 on the liquid crystal side as a constituent element, and the light transmittance can be controlled for each of these pixels.

  The area in which these pixels are formed is defined as a display area AR (area surrounded by a one-dot chain line in the figure), and light from a backlight BL, which will be described later, is irradiated over the entire display area AR and transmitted through each pixel. Make the viewer recognize the image through light.

  The substrate SUB1 disposed behind the observer as viewed from the observer has, for example, portions exposed from the substrate SUB2 on the left side and upper side in the drawing, and one side of the plurality of semiconductor devices SCD is connected to these portions. It has become so.

  These semiconductor devices SCD are composed of circuits for independently driving the respective pixels. Among the semiconductor devices SCD, a semiconductor device SCD (video signal driving circuit) arranged in parallel in the x direction in the drawing has printed circuit boards PCB1 and PCB2 connected to the other side facing the one side connected to the substrate SUB1. Then, an external input signal is input from a circuit (not shown) (display control unit 100 shown in FIG. 3) via the printed circuit boards PCB1 and PCB2. In the liquid crystal display device of this embodiment, for example, two printed circuit boards PCB1 and PCB2 are arranged in parallel.

  Further, in the semiconductor layer SCD, the semiconductor device SCD (scanning signal driving circuit) arranged in parallel in the y direction in the drawing has its external input signal via a wiring (not shown) formed on the surface of the substrate SUB1. Since the input is made, the boards corresponding to the printed circuit boards PCB1 and PCB2 are not connected.

  On the back surface of the liquid crystal display panel PNL, for example, a backlight BL is disposed via an optical sheet OS made of a diffusion sheet, a prism sheet, or a laminate thereof. The optical sheet OS guides the light from the backlight BL to the liquid crystal display panel PNL side by diffusing or condensing it.

  The backlight BL is referred to as a so-called direct type, and a plurality of, for example, external electrode fluorescent lamps whose longitudinal directions coincide with each other in the x direction in the figure and are arranged in parallel in the y direction in the figure in a plane parallel to the liquid crystal display panel PNL. With tube EFL. Each of these external electrode fluorescent tubes EFL is supported by a metal box-like frame DFR, for example. The frame DFR constitutes one frame (sometimes referred to as a lower frame) when the liquid crystal display panel PNL, the optical sheet OS, and the backlight BL are modularized. In the frame DFR, a reflection sheet RS is placed on the surface of the external electrode fluorescent tube EFL side. In this reflection sheet RS, a side wall surface BW having a slope whose periphery is raised by bending is formed at each of the upper and lower sides extending in the x direction in the drawing.

  It should be noted that the right and left sides of the frame DFR extending in the y direction are covered with the electrodes at both ends of the external electrode fluorescent tube EFL, respectively, and a side wall plate BWh made of a resin material, for example, The outer side is arranged with a slope that is raised. The side wall plate BWh is formed with a cutout CC on the lower side to avoid interference with each external electrode fluorescent tube EFL. The side wall plate BWh has a light reflecting function on the surface on the liquid crystal display panel PNL side, and constitutes a substantial side wall portion of the frame DFR together with the side wall surface BW of the reflective sheet RS.

  In the application of the present invention, the liquid crystal display panel PNL, the optical sheet OS, and the backlight BL are not necessarily limited to those having the above-described configuration.

  FIG. 3 is a block diagram showing an embodiment of a circuit provided in the above-described liquid crystal display module LDM. As described above, the liquid crystal display module LDM includes the liquid crystal display panel PNL, the optical sheet OS, and the backlight BL. Also, the circuit shown in FIG. 3 is arranged such that its circuit board is attached to the back surface of the frame DFR of the backlight BL, for example.

  First, there is a display control unit 100. The display control unit 100 includes a CPU, an input / output port, a memory, and the like (not shown). In the memory of the display control unit 100, a program for controlling the liquid crystal display module LDM, a display program for displaying display data on the display screen of the liquid crystal display panel PNL, and a luminance of the backlight BL are changed. Programs are stored.

  The display control unit 100 reads display data from the display memory 110, converts the display data into RGB signals, and converts the display drive signal SS including the RGB signals into the semiconductor device SCD (scanning signal drive circuit, liquid crystal display panel PNL). Video signal driving circuit). As a result, an image is displayed in the display area AR of the liquid crystal display panel PNL.

  Further, the display control unit 100 causes the luminance adjustment circuit 120 to input a signal for turning on the backlight BL and setting the luminance. In the following description, the luminance of the backlight BL is the luminance of the external electrode fluorescent tube EFL. The luminance adjustment circuit 120 inputs a digital signal having a frequency corresponding to the luminance of the backlight BL to the inverter circuit 130. The inverter circuit 130 generates an alternating drive signal corresponding to the frequency of the digital signal, and applies the alternating drive signal to each of the external electrode fluorescent tubes EFL in the backlight. Each external electrode fluorescent tube EFL emits light with a luminance corresponding to the alternating drive signal.

  Further, the liquid crystal display module LDM is provided with an optical sensor 140. The optical sensor 140 detects the illuminance around the liquid crystal display device. For this reason, the optical sensor 140 is disposed at a location where the irradiation light from the backlight BL does not enter. A detection signal indicating ambient illuminance is input to the A / D converter 150. The A / D converter 150 converts the detection signal into a digital signal, and this digital signal is input to the display control unit 100.

  In this embodiment, the optical sensor 140 functions as at least a sensor that detects whether the periphery of the liquid crystal display device is bright or dark. The distinction between bright and dark can be arbitrarily set in the display control unit 100 by the output from the optical sensor 140. When the display control unit 100 determines that the output from the optical sensor 140 corresponds to “dark”, the luminance of the backlight BL is controlled via the luminance adjustment circuit 120 as described later.

  FIG. 1A shows the brightness of the backlight BL and the timing of supplying the display drive signal SS to the liquid crystal display panel PNL when the liquid crystal display module LDM is driven when the power is turned on (lights on the TV). It is the shown graph. In the graph, the horizontal axis represents time (T), and the vertical axis represents backlight luminance (B / L).

  The graph shown in FIG. 1A assumes that a television is in a dark room and the television is turned on. Whether the room is dark is determined by the display control unit 100 based on the output from the light sensor 140, and the brightness adjustment circuit 120 adjusts the brightness of the backlight BL by the display control unit 100.

  In FIG. 1A, the backlight BL is turned on from the time (T1) when the power is turned on, and the brightness of the backlight BL suddenly becomes, for example, the maximum brightness. Then, it lasts until a time (T2) after a relatively short time, and at this time (T2), the brightness rapidly returns to a state before the power supply switch is turned on (light-off). During this period (T1 to T2), the liquid crystal display panel PNL has not yet been inputted with the display drive signal SS (scanning drive signal, video drive signal), and no image is displayed (black display). It has become. Here, although the liquid crystal display panel PNL is not displaying an image, the backlight BL is turned on during the period from T1 to T2 in order to warm the external electrode fluorescent tube EFL and extend its life. Preliminary lighting.

  A display drive signal SS (scanning drive signal, video drive signal) is sent from the display control unit 100 to the liquid crystal display panel PNL at a time (T3) after a very short time from the time when the backlight BL is turned off (T2). Supply. At this time, as shown by the characteristic A in the figure, the backlight BL is turned on so that the luminance increases with a gradient, and reaches the maximum luminance (time T4). For example, about 10 seconds are required from time T3 to time T4.

  As a result, the viewer of the television can perceive the image display on the surface of the liquid crystal display panel PNL as its luminance gradually increases. Therefore, the viewer can avoid suddenly recognizing a bright image when the television is turned on in a dark room, and can protect the eyes from glare.

  In general, a television is divided into three modes, such as a dynamic mode, a natural mode, and a cinema mode, from the highest to the lowest brightness of the backlight BL, and can be set to any mode by selection. It has become. In the graph shown in FIG. 1A, the luminance characteristic A of the backlight BL after the time point T3 is assumed to be set to the dynamic mode.

  For this reason, when used in a mode other than the dynamic mode, the overall luminance is lowered, for example, as shown in the characteristic B in the figure. Also in this case, it takes about 10 seconds until the brightness of the backlight BL rises with a gradient and reaches the maximum brightness of the set mode (time point T4).

  FIG. 1B is a graph showing the luminance control of the backlight BL when the display control unit 100 determines that the surroundings of the liquid crystal display device are bright based on the output from the optical sensor 140. In order to facilitate the comparison, it is drawn corresponding to FIG. In FIG. 1B, the characteristic A ′ is the luminance characteristic of the backlight BL in the dynamic mode with the maximum luminance. However, the characteristic A ′ has a constant luminance without decreasing the luminance even at the time point T2. It keeps lighting at. This is because the brightness from the backlight BL does not feel dazzling due to the ambient brightness. In FIG. 1B, the change in luminance of the backlight BL set to a lower luminance is shown in the characteristic B ′. The luminance of the backlight BL becomes maximum during the period (T1 to T2) during which the backlight BL is warmed, but the luminance is suddenly decreased at the time T2 to maintain the set luminance.

<Example 2>
FIG. 4 is an explanatory view showing another embodiment of the display device according to the present invention and corresponds to FIG.

  In FIG. 4, the configuration different from that in FIG. 1A adopts a preliminary lighting operation for warming the backlight BL from the time point (T1) when the switch is turned on to the next time point (T2). There is not to be.

  That is, when the switch is turned on (T1), the display drive signal SS is supplied to the liquid crystal display panel PNL to start image display, and the backlight BL is also lit so that its luminance increases with a gradient. is doing.

  Time points T1, T2, T3, and T4 on the horizontal axis in FIG. 4 are the same as the time points T1, T2, T3, and T4 in FIG.

  Such control is effective when a backlight light source such as an LED that does not require a preliminary lighting operation is used.

<Example 3>
FIG. 5 is an explanatory view showing another embodiment of the display device according to the present invention and corresponds to FIG.

  In FIG. 5, the configuration different from that in FIG. 4 is that the gradient is not set to the luminance of the backlight, but the display drive signal SS is subjected to the gradient control.

  That is, when the switch is turned on (T1), the backlight BL is turned on to the original luminance. Thereafter, the display drive signal SS is supplied to the liquid crystal display panel PNL so as to rise with a gradient, and image display is performed.

  The time points T1 and T4 on the horizontal axis in FIG. 5 are the same as the time points T1 and T4 in FIG.

  Such control can be performed even with a light source that requires preliminary lighting such as the external electrode fluorescent tube EFL.

<Example 4>
Although the above-described liquid crystal display device has been described as a liquid crystal display device provided in a television, it is needless to say that the liquid crystal display device is not necessarily limited to a television and may be a liquid crystal display device used in a personal computer or the like.

  As mentioned above, although this invention was demonstrated using the Example, the structure demonstrated by each previous Example is an example to the last, and this invention can be suitably changed within the range which does not deviate from a technical thought. Further, the configurations described in the embodiments may be used in combination as long as they do not contradict each other.

4 is a graph illustrating an example of a change in luminance of a backlight of a liquid crystal display device according to the present invention. It is a block diagram which shows one Example of the liquid crystal display device by this invention. It is a block diagram which shows one Example of the circuit with which the liquid crystal display device by this invention is equipped. 6 is a graph showing another embodiment of the luminance change of the backlight of the liquid crystal display device according to the present invention. 6 is a graph showing another embodiment of the luminance change of the backlight of the liquid crystal display device according to the present invention.

Explanation of symbols

LDM: Liquid crystal display module, OS: Optical sheet, BL: Backlight, SCD: Semiconductor device, SS: Display drive signal, 100: Display control unit, 110: Display memory, 120: Brightness adjustment Circuit 130... Inverter circuit 140... Optical sensor 150... A / D converter.

Claims (7)

A liquid crystal display device comprising a liquid crystal display panel and a backlight on the back of the liquid crystal display panel,
Detection means for detecting ambient illuminance;
When detecting that the surrounding of the liquid crystal display device is dark by the detecting means, the luminance signal to the backlight is input so as to increase with a gradient up to the set luminance when the backlight is turned on. A characteristic liquid crystal display device. The backlight is increased before the brightness of the backlight is increased with a gradient.
The liquid crystal display device according to claim 1, wherein a preliminary lighting operation is performed after the luminance of the backlight is once increased and then decreased.   3. The liquid crystal display device according to claim 2, wherein, when the detection unit detects that the surroundings of the liquid crystal display device are bright, the backlight emits light at a set luminance after the preliminary lighting operation.   3. The liquid crystal display device according to claim 2, wherein the display signal input to the liquid crystal display panel starts after the preliminary lighting operation.   3. The liquid crystal display device according to claim 2, wherein the display signal input to the liquid crystal display panel starts after the power is turned on.   2. The liquid crystal display device according to claim 1, wherein a time for increasing the brightness of the backlight with a gradient is set to 10 seconds or more. A liquid crystal display device comprising a liquid crystal display panel and a backlight on the back of the liquid crystal display panel,
When the power is turned on, the backlight is lit at the set brightness.
The liquid crystal display device according to claim 1, wherein a display signal is input to the liquid crystal display panel so as to rise up to a set signal value with a gradient.

Images