JP4701987B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, in particular, a transmissive type equipped with a backlight, and a medium to large size used for a television or a display for a PC.

  In recent years, the liquid crystal display device has been expanding its market while increasing the screen size while changing the use from a personal computer monitor to a television. Liquid crystal display devices can be broadly classified into a transmissive type with a backlight, a reflective type without a backlight, and a transflective type utilizing both features. Most medium-to-large liquid crystal display devices used for televisions and PC displays are transmissive.

  In addition, the backlights of liquid crystal display devices are divided into two types: a direct type with a cold cathode tube placed on the back of the liquid crystal panel, and an edge light type with a cold cathode tube placed around the periphery and guiding light with an acrylic light guide plate. Can be separated. The direct type is bright and lightweight, but is disadvantageous in terms of thickness. The edge light type, on the contrary, is advantageous for thinning, but is disadvantageous in terms of weight reduction because of its brightness and weight of the light guide plate.

  There was a time when the liquid crystal display device was once said to be dark, but recently, the direct type has increased mainly in large liquid crystal display devices, and the problem of display luminance has been solved.

  The display brightness of a transmissive liquid crystal display device can theoretically be increased depending on the brightness of the backlight. However, since there is a trade-off relationship with power consumption and life, the manufacturer (hereinafter referred to as the manufacturer) of the liquid crystal display device has characteristics. Determine the operating point. An example of an organic EL or the like is shown for the relationship between display brightness, power consumption, and life (see Japanese Patent Application Laid-Open No. 2002-117986), but CCFL (cold cathode) widely used as a backlight light source for liquid crystal display devices. There is a similar tendency for pipes. In short, trying to obtain display brightness increases power consumption and shortens the service life. Currently, the power consumption of a 32-inch class liquid crystal display device incorporating a digital tuner is about 150 to 200 watts, of which the backlight device accounts for 60 to 70%. For this reason, the brightness of the backlight, that is, the display luminance has a great influence on the power consumption.

  Here, an appropriate display luminance is considered. As disclosed in Japanese Patent Laid-Open No. 6-308991, from the characteristics of the human eye, the brighter the ambient light of the liquid crystal display device, the brighter the display luminance should be. Further, Japanese Patent Application Laid-Open No. 6-308991 discloses a display device that automatically controls display brightness in response to ambient light. This control method is referred to as adaptive luminance control in this specification. Although the adaptive luminance control has already been put into practical use and is mounted on a liquid crystal display device, in that case, the control is turned off at the factory setting of the liquid crystal display device.

  The reason is that the brighter the display brightness, the better the first impression. In trade fairs and stores selling liquid crystal display devices, the same kind of products (liquid crystal display devices) are often displayed in parallel. In such a place, it is preferable that the display luminance is bright. This is because if the adaptive brightness control is turned on at the factory setting, unless the person who knows the situation changes the setting, the impression of the liquid crystal display device may be deteriorated when the ambient light is dark.

  As another reason, when comparing the performance of products, it is often done at the factory setting from the viewpoint of fairness, and the manufacturer has an intention to always maximize the display brightness in such a situation.

  The above discussion is only a first impression when comparing and comparing liquid crystal display devices of the same type, and it is different when looking at the screen for a long time in a scene of actual use such as at home. First, the brightness of ambient light is different between homes and stores. According to one theory, the illuminance of ambient light incident on the liquid crystal display device is about 1000 to 1500 lux, and it is about 250 to 300 lux in the living room at home. According to Japanese Patent Laid-Open No. 6-308991, the display brightness is too bright to use at home with the factory setting (adaptive brightness control off), and the eyes are tired. Secondly, there is usually no parallel comparison at home. Japanese Patent Application Laid-Open No. 2002-117986 shows an example of a small portable terminal, but it is shown that even if the display luminance is reduced to about 70%, the human eye does not feel a change in brightness. In other words, even if the display luminance becomes dark, the change is gradual in time, and it is impossible to understand unless there is a relative comparison.

In order to avoid such a situation that it is too bright and difficult to see during use and avoids an increase in power consumption, the liquid crystal display device is provided with mode switching (dynamic, standard, etc.) and display luminance adjustment means.
JP 2002-117986 A Japanese Patent Application Laid-Open No. 6-308991

  However, when the above-described mode switching or display brightness adjustment is performed, it is uncomfortable because the user who performed the operation recognizes that the display brightness, which is one of the performance indicators of the liquid crystal display device, is being used. is there. In addition, as functions of liquid crystal display devices are increasing, there is a concern that a user who is not good at a machine may use it as it is because the method of mode switching and display brightness adjustment is complicated.

  In order to solve this problem, the liquid crystal display device of the present invention is provided with a time measuring means for measuring the cumulative operation time, and the display luminance is changed based on the output of the time measuring means.

  A power consumption can be reduced and the life can be extended without requiring the user to perform any consciousness or special operation, and a liquid crystal display device with an easy-to-read display brightness can be obtained.

  The present invention will be described below with reference to the drawings.

  A block diagram of the first liquid crystal display device of the present invention is shown in FIG.

  The time measuring means 105 measures the accumulated operation time by dividing and counting the synchronization signal input to the liquid crystal display device. Note that the time measuring means 105 may be simply substituted by the number of times the liquid crystal display device is energized. The determination and control means 104 compares the output of the control map 106, which will be described later, with the output of the time measuring means 105, and performs dimming control of the backlight 101 of the liquid crystal panel module 103.

  In the description of the control map 106, for the sake of simplification, the display brightness refers to the case where the transmittance of the liquid crystal panel 102 is maximized, and the dimming control of the backlight 101 and the display brightness have a linear relationship. To do.

  The control map is as shown in FIG. t0 is the start of operation, and the maximum dimming control C1 is maintained until t1. As a result, the maximum brightness can be obtained for a certain period of time, so there is no disadvantage in parallel comparison with other liquid crystal display devices. The horizontal axis in FIG. 2 and the accumulated operation time are arbitrary units, but the order of the year is assumed for the purpose of the present invention. For example, t2 is a point where the accumulated operation time is 1000 hours, which is about one year after operation of 3 hours per day. The light control is gradually darkened from C1 to C2 from t1 to t2. After t2, the dimming control is fixed at C2, and a certain level of display brightness is maintained, but such a lower control limit is not particularly required. The t1, t2, and C2 points may be determined by the manufacturer in view of the assumed usage situation, and so on. Compared with the case where the shaded portion in FIG. 2 continues to have the maximum brightness, it is shown that the effect of reducing power consumption and extending the life can be obtained.

  In addition, a comparison with a conventional liquid crystal display device will be made. Assume that the cumulative operation time and the result of the actual dimming control are as shown in FIG. As shown by the solid line in FIG. 3, the conventional liquid crystal display device dims the dimming control to C3 at the user's intention at t0 immediately after the start of operation, and continues thereafter. The value of C3 and the switching method may be recommended by the manufacturer. The shaded portion in FIG. 3 shows that the effect of reducing power consumption and extending the life can be obtained as compared with the conventional liquid crystal display device. In FIG. 3, it can be read that the conventional liquid crystal display device is more effective during the period from t0 to t3, but in general, the liquid crystal display device has a longer life than other devices, and the longer the operation is, the longer it is in FIG. Since the area of the shaded portion is relatively increased, the effect of the present invention can be obtained more.

  As described above, the liquid crystal display device of the present invention uses the familiarity of the eyes by gradually decreasing the display luminance over time, and reduces power consumption and extends the life without the user being conscious. Can do.

  Points common to the first embodiment are given the same reference numerals, and only different points will be described.

  FIG. 4 shows the cumulative operation time when the function-off selection 108 in FIG. 1 is input and the result of the dimming control actually performed. The function off selection is input at t4 when the dimming control becomes C4, and the function off is released at t4 ', that is, the function is turned back on. During the function off period, the time counting means 105 stops counting up, and the dimming control in the state of t4 from the time when the function on is returned to t4 'continues from C4 to perform the dimming control. Such a function off selection is provided for a case where the liquid crystal display device is temporarily used in a bright place. The life of the liquid crystal display device is often defined by the fact that the display luminance is halved from the initial operation state. However, the liquid crystal display device of the present invention is in a state where the display luminance is bright by having such a function off. Therefore, even if the dimming control is positively performed, it is not determined that the service life is reached.

  By the way, inputting a control value related to dimming such as function off seems to be contrary to the gist of the present invention that the user does not have to be aware of it, but there are a plurality of users and some of them are determined. It is assumed that the same effect can be obtained for other people if the operation is performed. This also applies to Example 3 described later.

  Points common to the first embodiment are given the same reference numerals, and only different points will be described.

  This embodiment relates to an example in which the manual reset 109 in FIG. 1 is input, and the accumulated operation time and the result of the actually performed dimming control are as shown in FIG. When the cumulative operation time is t5 and the dimming control becomes C5, a manual reset is input, and the count value of the time measuring means is returned to the operation start state t0, and accordingly the dimming control is also returned to the operation start state. Has been. The manual reset is effective for a new user who uses the liquid crystal display device for the first time from the time t5 when the user determines that the display brightness is low or by transfer or the like.

  Further, an example in which the manual reset 109 is input after the return amount 110 in FIG. 1 is input will be described. As shown in FIG. 6, when the cumulative operation time is t6 and the dimming control becomes C5, there is a manual reset input, and the return amount can be arbitrarily input. In this example, however, t6-t6 ′ when converted in terms of time. It corresponds to C6-C5 converted by dimming control. By doing so, it is possible to continue to obtain an effect at a level acceptable to the user, and since the dimming control is gradually darkened, further effects can be expected in the future.

  Points common to the first embodiment are given the same reference numerals, and only different points will be described.

  This embodiment is an example in which the ambient light sensor 107 in FIG. 1 is provided and combined with adaptive luminance control. FIG. 7 shows the cumulative operation time and the result of the dimming control actually performed as shown in FIG. After t1, the ambient light sensor 107 reflects the result of detecting ambient light. When the surroundings are bright, the dimming control is bright. When the surroundings are dark, the dimming control is also dark. The display brightness is easy to see. FIG. 8 shows an enlarged view of the minute interval t7 to t7 ′ in FIG. The dimming control in FIG. 8 shows that the ambient light gently changes from t7 to t8, changes rapidly due to the lighting fixture being turned on at t8, and remains constant thereafter. Yes. In FIG. 8, C7 is the maximum value of the dimming control at this time (t7 to t7 ′), C8 is the minimum value of the dimming control at this time, and between C8 and C7 according to the ambient light. Dimming control is performed. In FIG. 7, by gradually reducing the maximum value of the display brightness according to the accumulated operation time, it is possible to obtain an easy-to-see display brightness according to the ambient light while obtaining the same effect as in the first embodiment.

  The liquid crystal display device of the present invention has the effects of reducing power consumption, extending the service life, and providing easy-to-read display brightness without forcing the user to be aware or perform special operations, and is useful for improving the performance of the liquid crystal display device.

Block diagram of the present invention The figure which shows the control map of this invention Relationship diagram between cumulative operating time and dimming control Relationship diagram between cumulative operating time and dimming control Relationship diagram between cumulative operating time and dimming control Relationship diagram between cumulative operating time and dimming control Relationship diagram between cumulative operating time and dimming control Relationship diagram between cumulative operating time and dimming control

Explanation of symbols

101 Backlight 102 Liquid Crystal Panel 103 Liquid Crystal Panel Module 104 Judgment and Control Means 105 Timekeeping Means 106 Control Map 107 Ambient Light Sensor 108 Manual Reset Input 109 Return Amount Input 110 Function OFF Selection Input

Claims (5)

Time counting means for counting the cumulative operation time by dividing the synchronization signal input to the liquid crystal display device and counting up the count value;
The first display brightness is maintained from the start of operation to the first cumulative operation time, and the display brightness is adjusted to the cumulative operation time from the first cumulative operation time to the second cumulative operation time according to the familiarity of the eyes. And a control map for maintaining a second display luminance lower than the first display luminance after the second cumulative operating time, and a reduction in brightness so that the eyes do not feel a change in brightness.
Determination and control means for performing dimming control of display luminance on the backlight of the liquid crystal panel module based on the output of the control map and the output of the time measuring means;
A liquid crystal display device. The time measuring means stops counting up during a period when the function off signal is input,
The liquid crystal display device according to claim 1, wherein the determination and control unit performs dimming control of the first display luminance during a period in which the function off signal is input. 2. The liquid crystal display device according to claim 1, wherein the time measuring means sets a count value that goes back to the operation start state when a manual reset signal is input. 4. The liquid crystal display device according to claim 3, wherein when the return amount signal is further input, the time measuring means sets a period obtained by converting the return amount signal into a time count. In addition, it has an ambient light sensor,
The liquid crystal display device according to claim 1, wherein the determination and control unit performs adaptive luminance control based on an output of the ambient light sensor.

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