JPH045623A - Liquid crystal display device, information processor, and liquid crystal television - Google Patents

Abstract

PURPOSE:To improve the easiness of use by providing a voltage control means which controls a liquid crystal screen driving voltage according to detected brightness so that a liquid crystal screen is held at set brightness. CONSTITUTION:When the brightness adjusting knob of a brightness setter 80 is set in automatic setting mode, a CPU 11 selects a curve C1 among ambient temperature-driving voltage curves C1, C2... in a program memory 19 and sends information for a driving voltage corresponding to ambient temperature to a driving voltage control circuit 16 according to the curve. For example, when the ambient temperature is T1, T2, or T3, an instruction for a driving voltage V1, V2, or V3 is sent. When the driving voltage of the liquid crystal display panel 70 is V1 - V3 while the ambient temperature is T1 - T3, the screen is placed in a maximum contrast state. Therefore, when the know is set in the automatic setting mode, the brightness of the white part and the brightness of the black part on the screen are maintained so that the maximum contrast state is obtained at all times. When the adjusting knob of the brightness setter 80 is set in manual setting mode, the CPU 11 performs operation in the manual setting mode.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display device.

[Conventional technology]

Generally, in a liquid crystal display device, the brightness of the screen changes due to changes in ambient temperature.

In recent years, with the advancement of liquid crystal cells, the problem of changes in screen brightness is gradually being solved, but in the past, such improvements in liquid crystal cells alone have not been able to completely suppress changes in screen brightness.

Therefore, as a method to suppress changes in screen brightness, for example,
There is a liquid crystal display device described in Japanese Unexamined Patent Publication No. 60-209789.

This LCD device uses a temperature detector that detects the temperature around the screen, and controls the LCD screen drive voltage to a predetermined voltage according to the detected temperature to maintain the screen brightness at a specific value. A voltage control circuit is provided.

[Problem to be solved by the invention]

However, in such conventional liquid crystal display devices, even if the operator adjusts the brightness to the desired brightness using the brightness adjustment knob, when the ambient temperature of the screen changes, the brightness is adjusted to a specific brightness corresponding to a predetermined voltage. Therefore, the operator has to adjust the brightness again using the brightness adjustment knob, and there is a problem in that the desired brightness cannot be maintained.

The present invention has been made in view of these conventional problems, and provides a liquid crystal display device that can maintain the screen brightness desired by an operator, an information processing device equipped with the same, and a liquid crystal television. The purpose is to

[Means to solve the problem]

The above object includes: a brightness detection means for directly or indirectly detecting the brightness of an LCD screen; a brightness setting means for allowing an operator to set the brightness of the LCD screen; This can be achieved by a liquid crystal display device characterized in that it is equipped with two voltage control means for controlling a liquid crystal screen sleep voltage so that the brightness of the screen is maintained at a set brightness.

Here, it is preferable that the brightness setting means has a manual setting mode in which an operator sets the brightness of the liquid crystal screen, and an automatic setting mode in which the brightness is set to a predetermined brightness.

Note that the above liquid crystal display device may be applied to an information processing device equipped with a liquid crystal screen, a liquid crystal television, a liquid crystal watch, and the like.

[The operation operator sets the brightness of the screen to a desired brightness using the brightness setting means.

The brightness of the screen changes in response to changes in ambient temperature, etc., and this change in brightness is detected directly or indirectly by the brightness detection means.

The voltage control means controls the liquid crystal screen drive voltage based on the detected brightness so that the brightness of one screen is maintained at the set brightness.

Therefore, the brightness desired by the operator can always be maintained.

〔Example〕

Various embodiments according to the present invention will be described based on FIGS. 1 to 14. In addition, when explaining various examples,
Identical parts are given the same reference numerals and redundant explanations will be omitted.

A first embodiment of the information processing device will be described based on FIGS. 1 to 9.

FIG. 1 is an overall block diagram of the information processing apparatus, where ]O is the main body of the information processing apparatus. Reference numeral 20 denotes an external storage device for storing various data, such as a 5-inch or 3.5-inch floppy disk device (FDD). 30 is a printing device, 40 is a keyboard, and 60 is a power supply device. 7
0 is a reflective liquid crystal display panel for displaying various information.

Each of the above devices 20, 30, 40, 60, and 70 is connected to the information processing device main body 10 via a cable.

Reference numeral 50 denotes a temperature sensing element whose resistance value changes according to temperature changes in the R range. In FIG. 1, the temperature sensing element 50 and the display panel 7
Although drawn apart from the temperature sensor 50, the temperature sensing element 50 detects the ambient temperature of the display panel 70, and is actually provided on the back surface of the display panel 70.

Reference numeral 80 denotes a brightness setting device that adjusts the screen brightness of the display panel 70, and is provided in the information processing device main body 10. The brightness setting device 8o is composed of a resistor 81, a variable resistor 82, and a brightness adjustment knob 83 attached to the variable resistor 82, as shown in FIGS. 6 and 7. In the brightness setting device 80.

A manual setting mode in which an operator can arbitrarily adjust the brightness of the screen and an automatic setting mode in which the brightness of the screen is adjusted to a predetermined brightness are provided.

The information processing device main body 1o includes a floppy disk controller (FDC) 12 for controlling the FDD 20, a printing device controller 13 for controlling the printing device 3, a keyboard controller 14 for controlling the keyboard 40, and a display panel. a display panel controller 17 for controlling the display panel 7o, an A/D converter 15 for converting the analog value output signals of the temperature sensing element 50 and the brightness setting device 80 into digital signals, and a drive voltage for controlling the drive voltage of the display panel 70. A control circuit 16, a program memory 19 in which various programs are stored, a work memory 18 used when executing 5 programs, and a CPU II that controls program execution and various circuits 12 to 19.
and a bus B that connects these.

As shown in FIG. 5, the drive voltage control circuit 16 includes a voltage stabilizing circuit 16a and a D/A converter 16b for stabilizing and extracting an output voltage Vo from an input voltage Vi.

The voltage stabilizing circuit 16 currently exists as a general-purpose linear IC, and its output voltage Vo is the value obtained by subtracting the sum of the voltage Vcom applied to the common terminal and the constant voltage Vat from the input voltage Vin, that is, the following: Formula % Formula %) Therefore, by changing Vcom, an arbitrary output voltage can be obtained.

As shown in FIGS. 2 and 3, the liquid crystal display panel 70 includes a first deflection plate 71 that allows only the light component in the xx' force direction to pass through, and a first deflector plate 71 that allows only the light component in the Y-Y' force direction to pass through. Second
a deflection plate 77, a first glass plate 72 in contact with the first deflection plate 71, a second glass plate 76 in contact with the second deflection plate 77, a first glass plate 72 and a second glass plate. 76 and a reflecting plate 78.

Transparent electrodes 73 and 74 are printed on the first glass plate 72 and the second glass plate 76, respectively. Transparent electrode 7
3.74 is applied with a voltage from the drive voltage control circuit 16.

Next, the operation of the first embodiment will be explained.

First, the operating principle of the reflective liquid crystal display panel 70 will be explained.

When no voltage is applied between the transparent electrodes 73, 75, the long axes of the liquid crystal molecules 74 are parallel to the glass plates 72, 76 and twisted by 90 degrees, as shown in FIG.

Therefore, the first polarizing plate 71 and the first glass plate 7
2, the incident light passes through the second glass plate 76 and the second glass plate 76.
The light passes through the deflecting plate 77 and is reflected by the first reflecting plate 78, so that the screen is displayed white as shown in the figure.

When a voltage is applied between the transparent electrodes 73 and 75, the third
As shown in the figure, the long axis of the liquid crystal molecules 74 is aligned with the glass plate 72.
76. Therefore, the first polarizing plate 7
The incident light that has passed through 1 reaches the second polarizing plate 77 without being polarized by the liquid crystal molecules 74, so it cannot pass through the second polarizing plate 77, and as a result, the screen becomes black as shown in the figure. It will be displayed.

According to the above operating principle, the reflective liquid crystal display panel 70
Various display data will be displayed.

FIG. 8 shows the recording voltage-luminance characteristics of the reflective liquid crystal display panel 70. When the ambient temperature is T1, the brightness curve of the non-selected segment that is white is N1, and the brightness curve of the selected segment that is black is 81. From the figure, the voltage at which the distinction between the non-selected segment and the selected segment becomes clearest, that is, the voltage at which the maximum contrast is achieved, is when the drive voltage of one display panel 70 is Vl. At this time, the brightness of the non-selected segment is Ba, and the brightness of the selected segment is B.

Here, the contrast is defined as the ratio of the brightness of the white part and the brightness of the black part, as shown in the following equation.

The ambient temperature of the liquid crystal display panel 70 is from T1 to T2 (Tl<
Consider the case where the change to T2) occurs.

- For boat fishing, when the ambient temperature changes, the brightness characteristics of the liquid crystal display panel also change accordingly. In the liquid crystal display panel 70 of this embodiment, when the ambient temperature changes from T1 to T2, the non-selected segment The brightness curve becomes N2, and the brightness curve of one selected segment becomes N2. From the same figure, the driving voltage that provides the maximum contrast is v2, but the instantaneous voltage v1
If it remains as it is, the brightness of the selected segment is Bb, and the selected segment (black) becomes brighter, making the entire screen somewhat brighter.

Next, consider a case where the ambient temperature changes from T1 to T3 (Tl>T3).

In this case, the brightness curve of the non-selected segment becomes N3 and 1
The brightness curve of the selected segment is N3.

From the same figure, the driving voltage that provides the maximum contrast is v3, but if the driving voltage remains at 1, the brightness of the non-selected segments will be Bc and the non-selected segments (white) will become darker, making the entire screen somewhat darker. Get dark.

As described above, it can be seen that when the driving voltage is constant and the ambient temperature of the liquid crystal display panel 70 changes, the brightness of the screen changes.

Next, the operation of the information processing apparatus for maintaining screen brightness will be described.

The temperature sensing element 5o provided in the liquid crystal display panel 70 is
When the ambient temperature of the liquid crystal display panel 70 changes, the resistance value changes, and as shown in FIG.
It takes. The CPU 11 sets the voltage Vth of the temperature sensing element 5o to A.
/D converter 15, and the ambient temperature is determined from the measured value. The program memory 19 contains the ninth
A plurality of ambient temperature-driving voltage curves CI as shown in the figure.

C2, . . . are stored, and the CPU 11 instructs the drive voltage control circuit 16 to determine the drive voltage of the liquid crystal display panel 70 based on this curve. Drive voltage control circuit 16
Now, in response to this instruction, the common terminal Vcom of the voltage stabilizing circuit 16a changes, and the output voltage (drive voltage) Vo
The changes in the two drive voltages differ depending on changes in ambient temperature and in the automatic setting mode and manual setting mode of the brightness setting device 80.

When the brightness adjustment knob 83 of the brightness setting device 8o is set to the automatic setting mode, the CPU II recognizes the automatic setting mode and adjusts the plurality of ambient temperatures in the program memory 19.
One of the driving voltage curves C1, C2°, . . . selects one ambient temperature-driving voltage curve C1.

Based on this curve, a drive voltage corresponding to the ambient temperature is instructed to the drive voltage control circuit 16. Here, for example, when the ambient temperatures are T1, T2, and T3, instructions are given to set the drive voltages to vl, ■2, and ■3, respectively. When the ambient temperature is T1, T2, and T3, the liquid crystal display panel 70
When the driving voltages are respectively vl, v2, and v3, the screen is in the maximum contrast state, as described above.

Therefore, when the automatic setting mode is set, the brightness of the white portion and the brightness of the black portion of the screen are always maintained at a value that maximizes the contrast.

When the brightness adjustment knob 83 of the brightness setter 80 is set to manual setting mode, the CPU II recognizes the manual setting mode.

If the operator turns the brightness rA adjustment knob 83 at a certain point, for example, to the position R2 in FIG. It's a little darker than that. C.P.
U11 is a plurality of ambient temperatures in the program memory 19.
Among the driving voltage curves C1, C2, ..., select the ambient temperature-driving voltage curve C2, which has a higher driving voltage than the ambient temperature-driving voltage curve C1, and based on this curve, calculate the driving voltage corresponding to the ambient temperature. is instructed to the drive voltage control circuit 16. Here, for example, the ambient temperature is T1, T2, . T3
When , the driving voltage is Vl'(>Vl),
Instruct to set V2'(>V2) and V3'(>v3). The drive voltage changes depending on the ambient temperature, and the screen brightness is the brightness when the operator sets the brightness adjustment knob 83 to R2 (slightly darker than in automatic setting mode).
will be maintained.

Furthermore, if the operator turns the brightness adjustment knob 83 to the position R3 in FIG. It also becomes a little brighter. CPU
II selects an ambient temperature-drive voltage curve C3 having a lower drive voltage than the ambient temperature-drive voltage curve C1 from among the plurality of ambient temperature-drive voltage curves C1, C2, . . . in the program memory 19; Based on this curve, a drive voltage corresponding to the ambient temperature is instructed to the drive voltage control circuit 16. For example, when the ambient temperatures are T1, T2, and T3, the driving voltages are set to vl''(<Vl) and Vl, respectively.
2” (<V2), V3” (<v3). The drive voltage changes depending on the ambient temperature, and the brightness of the screen is maintained at the brightness at the time when the operator sets the brightness adjustment knob 83 to R3 (slightly brighter than in the automatic setting mode).

In this embodiment, the brightness of the screen can always be maintained even when the ambient temperature changes, and even after the operator adjusts the brightness of the screen to the desired brightness.

This desired brightness can be maintained.

In this embodiment, the brightness setting means is constituted by a brightness setting device 80. Further, the voltage control means includes a drive voltage control circuit 16 and a program memory 1 storing a plurality of ambient temperature-drive voltage curves C1, C2, .
9, and a CP that instructs the drive voltage control circuit 16 to set the drive voltage based on the curve stored in the program memory 19.
It consists of UI 1.

In the embodiments described above, the brightness setting means is configured with a brightness setting device 80 equipped with a variable resistor 82. As an example, the following description will be made based on FIGS. 10 and 11.

As shown in FIG. 10, a brightness setting key 41 is provided on the keyboard 40a. The program memory 19 stores a program that displays a brightness setting screen 79 as shown in FIG. 11 when the brightness setting key 41 is pressed.

When the operator presses the brightness setting key 41, the CPU
I calls the program from the program memory 19 and instructs the display controller panel 17 to display the brightness setting screen 79. The operator moves the position of u M n on the displayed brightness setting screen 79 by key operation and instructs the desired brightness. In this modification, when the position of tz M pt is moved to the position of Xl, the brightness obtained in the automatic setting mode in the above embodiment is set. 11 The position of M j+ is moved to the position of X2, 17
When the position of M Tl is moved from the position of 'M'' to the position of X3, the brightness is set when the brightness adjustment knob 83 of the above embodiment is set to R2 and R3, respectively.

When the ambient temperature changes, the set values Xi, X2 . For X3, the drive voltage is controlled based on the ambient temperature-drive voltage curves CI, C2, and C3, and the brightness of the screen is always maintained constant even if the ambient temperature changes.

Next, regarding the second embodiment of the information processing device, FIGS.
This will be explained based on FIG. 14.

While the above embodiment indirectly detects the brightness of the screen using the temperature sensing element 5o, this example directly detects the brightness of the screen using the brightness detectors 90 and 95. It is something to do.

As shown in FIG. 13, the reflective liquid crystal display panel 70a is provided with a black display area AB to which a voltage is always applied and a white display area AW to which a voltage is not always applied. Luminance detectors 90.95 for detecting the luminance of each of the black display area AB and the white display area AW are provided corresponding to each area.

The brightness detectors 90.95 are composed of phototransistors as shown in FIG. 14, and are connected to the liquid crystal display panel 70a.
The input voltages Vab and Vaw of the A/D converter 15 are provided to change depending on the amount of light that has passed through the A/D converter 15.

CPU II via the A/D converter 15.

The output of the brightness detector 90.95 is constantly monitored, and the brightness is not recognized indirectly from the ambient temperature of the liquid crystal display panel 70a, but directly from the output of the brightness detector 90.95. .

When the brightness adjustment knob 83 of the brightness adjuster 80 is set to the automatic setting mode, the driving voltage of the liquid crystal display panel 70a is controlled so that maximum contrast is always achieved.

That is, when the ambient temperature is T1, the drive voltage is set to vl so that the brightness of the black display area AB is B and the brightness of the white display area AW is Ba. When the ambient temperature changes from T1 to T2, the brightness of the black display area AB becomes Bb, so the CPU 11 recognizes the increase in brightness using the brightness detector 90 and changes the drive voltage from vl to v2. , the brightness of AB is set to B, and the brightness of AW is set to Ba. Also, the ambient temperature is T
When the brightness changes from 1 to T3, the brightness of the white display area AW becomes Be, so the CPU II recognizes the decrease in brightness by the brightness detector 95, changes the immediate voltage from Vl to v3, and changes the brightness of the white display area AW to Be. The brightness of AW is set to B, and the brightness of AW is set to Ba.

When the brightness adjustment knob 83 of the brightness adjuster 80 is set to the position R2, the brightness of the black display area AB is maintained at B, but the drive voltage is controlled so that the brightness of the white display area AW changes from Ba to Be. Ru. And the brightness B of each area,
Be is set so that it remains constant even if the ambient temperature changes.
The driving voltage is controlled.

When the brightness adjustment knob 83 of the brightness adjuster 80 is set to the position R2, the drive voltage is controlled so that the brightness of the white display area AW becomes Ba and the brightness of the black display area AB changes from B to Bb. The brightness Bb and Ba of each area are
The drive voltage is controlled to remain constant even if the ambient temperature changes.

In this embodiment, since the brightness is directly detected, the brightness of the screen can always be maintained constant even if a factor other than the change in brightness, such as a change in ambient temperature, occurs.

Note that in this embodiment as well, the brightness setting may be performed using the keyboard 4o, as in the modification of the first embodiment.

Further, in the above embodiments, the present invention is applied to reflective type liquid crystal display panels, but the present invention is not limited to this and can also be applied to transmissive type liquid crystal display panels. Needless to say. It can also be applied to color liquid crystal display panels.

Further, the present invention can be applied to any device including a liquid crystal display panel, such as a liquid crystal television or a liquid crystal watch.

〔Effect of the invention〕

In the present invention, for the screen brightness set by the operator,
Since a voltage control means is provided to control the drive voltage of the liquid crystal display screen so as to maintain this brightness, the brightness of the screen desired by the operator can be maintained and usability can be improved.

[Brief explanation of drawings]

1 to 9 show a first embodiment, in which FIG. 1 is an overall block diagram of an information processing device, and FIGS. 2 and 3 are detailed configurations of a reflective liquid crystal display panel. Figure 4 is a circuit diagram between the temperature sensing element and A/D converter, Figure 5 is a circuit diagram of the instant voltage control circuit, Figure 6 is a front view of the brightness adjustment knob, and Figure 7 is the brightness. Circuit diagram of setting device, No. 8
The figure is a graph showing drive voltage vs. brightness characteristics, and Figure 9 is a graph showing the driving voltage vs. brightness characteristics.
Graphs showing Jm degree vs. inductive voltage characteristics, FIGS. 10 and 11 show modifications of the first embodiment, FIG. 10 is a front view of the keyboard, and FIG. 11 is a brightness setting screen. Explanatory diagrams, FIGS. 12 to 14 show the second embodiment, and FIG. 12 is an overall block diagram of the information processing device, and FIG.
The figure is an explanatory diagram showing the positional relationship between the liquid crystal display panel and the brightness detector, and FIG. 14 is a circuit diagram around the brightness detector. 10... Information processing device main body, 11... CPU, 15
... A/D converter, 16... Drive voltage control circuit, 19... Program memory, 20... Floppy disk device, 30... Printing device, 40.40a...
・Keyboard, 50... Temperature sensing element, 60... Power supply device, 70° 70a... Reflective liquid crystal display panel, 80.
...Brightness setting device, 90.95...Brightness detector.

Claims (1)

[Claims] 1. Brightness detection means for directly or indirectly detecting the brightness of the liquid crystal screen; Brightness setting means for allowing an operator to set the brightness of the liquid crystal screen; Based on the detected brightness; A liquid crystal display device comprising: voltage control means for controlling a liquid crystal screen driving voltage so that the brightness of the liquid crystal screen is maintained at a set brightness. 2. A brightness detection means that directly or indirectly detects the brightness of the liquid crystal screen; a manual setting mode in which an operator sets the brightness of the liquid crystal screen; and an automatic setting mode in which the brightness is set to a predetermined brightness. and voltage control means for controlling the LCD screen drive voltage so that the brightness of the LCD screen is maintained at the set brightness based on the detected brightness. LCD display device. 3. The liquid crystal display device according to claim 1 or 2, wherein the brightness detection means is a temperature detection means for measuring the ambient temperature of the liquid crystal screen. 4. Temperature detection means for detecting the ambient temperature of the liquid crystal screen; Brightness setting means that allows an operator to set the brightness of the liquid crystal screen; Brightness of the liquid crystal screen, ambient temperature of the liquid crystal screen, and driving of the bright liquid crystal screen Correlation storage means for storing a plurality of correlations with voltage; Selecting a correlation for a set brightness from among the plurality of correlations, and selecting the correlation with the set brightness based on the correlation and the detected ambient temperature. 1. A liquid crystal display device comprising voltage control means for controlling drive voltage. 5. A liquid crystal display device according to claim 1, 2, 3 or 4;
An information processing device comprising: a CPU that performs predetermined calculations. 6. A liquid crystal display device according to claim 1, 2 or 3, and a video signal detection and amplification circuit that extracts and amplifies a video signal from an audio and video signal and outputs it to the liquid crystal display device. LCD TV.