JPH11337909A - Liquid crystal display device and computer system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a gradation characteristic of a liquid crystal display device changeable and to switch a display image and the gradation characteristic according to a use. SOLUTION: Plural gradation characteristics are beforehand set in a gradation voltage generation circuit 13, and the used gradation characteristic is selected according to e.g. a user operable switch 18 and a selection signal from a computer using the liquid crystal display device as a display monitor. A gradation corrective reference voltage corresponding to the selected gradation characteristic is formed in a gradation voltage generation circuit 13 to be outputted to a source driver IC 16. In the source driver IC 16, a gradation voltage corresponding to a gradation level of the display data sent from a control IC 14 in every pixel is decided from the gradation corrective reference voltage from the gradation voltage generation circuit 13 to be supplied to a TFT liquid crystal panel 17 as a source line drive voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a computer system using the same, and more particularly to an active matrix type liquid crystal device such as a TFT for driving each image of a liquid crystal panel using a gradation voltage corresponding to an input signal. The present invention relates to a display device and a computer system using the same as a display monitor.

[0002]

2. Description of the Related Art Generally, gradation characteristics in a TFT liquid crystal display device are determined by a gamma correction power supply voltage (gradation correction reference voltage) input to a source driver. This gradation correction reference voltage is generated by a gradation voltage circuit in the TFT liquid crystal display device, and the source driver responds to the input signal using the gradation correction reference voltage generated from the gradation voltage circuit. Each image on the TFT liquid crystal panel is driven by determining the gray scale voltage and supplying the gray scale voltage as a drive voltage to the source line. As a result, multi-tone display such as color display is realized.

However, since the gradation voltage circuit usually has only one gradation characteristic, the relation between the gradation level and the gradation correction reference voltage value is always constant. For this reason, TFT
It is not possible to realize two or more gradation characteristics such as easy-to-view gradation characteristics and the same gradation characteristics as a CRT monitor in consideration of the optical characteristics inherent to the liquid crystal display device. There is a problem that the gradation of the image is different when viewed on a TFT liquid crystal display device and when viewed on a CRT monitor.

Further, when a still image or a moving image is displayed, in an image having many dark gradation portions, it is difficult to recognize the image with human eyes because the gradation difference in the dark portion is small. There was a problem.

[0005]

As described above, in the prior art, only one predetermined gradation characteristic can be used, and the gradation characteristic cannot be changed in accordance with a display image or application. Was. The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a liquid crystal display device capable of performing a screen display by selectively using a plurality of gradation characteristics and a computer system using the same. Aim.

[0006]

In order to solve the above-mentioned problems, the present invention provides a liquid crystal display device for driving each image of a liquid crystal panel using a gradation voltage corresponding to an input signal. A plurality of gray-scale characteristics different from each other in relation to the gray-scale correction reference voltage, and a gray-scale voltage generation means for generating a gray-scale correction reference voltage based on the selected gray-scale characteristic; A driving unit for driving each image of the liquid crystal panel based on the generated gradation correction reference voltage and the input signal, wherein a plurality of gradation characteristics can be selectively used. And

In this liquid crystal display device, a plurality of gradation characteristics are set in advance in the gradation voltage generating means. For example, a switch operable by a user or a selection from a computer using the liquid crystal display device as a display monitor is made. A gradation characteristic to be used is selected according to a signal or the like. As a result, a screen display can be performed by selectively using a plurality of gradation characteristics, and the gradation characteristics can be switched according to a display image or a use.

Further, it is also possible to automatically switch the gradation characteristics in conjunction with the switching of the display mode of the computer system. Thus, when a screen is displayed on a liquid crystal display device, easy-to-see gradation characteristics are used in consideration of the optical characteristics inherent to the liquid crystal display device, and when a CRT monitor and a liquid crystal display device are simultaneously displayed, It is possible to perform control such as using a gradation characteristic that can obtain the same gradation as seen on a CRT monitor.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a TFT liquid crystal display device according to one embodiment of the present invention. This TF
The T liquid crystal display device is an active matrix type display device that drives and controls each image of a liquid crystal panel using a gradation voltage corresponding to an input signal. Reference numeral 11 denotes an input terminal, which includes a display controller built in an information terminal such as a personal computer and a display signal such as characters, graphics, and moving images generated by a power supply circuit, a control signal, a power supply, and GND. Is entered.

Reference numeral 12 denotes a voltage circuit which converts a voltage input from the input terminal 11 into various power supply voltages such as a circuit voltage in a TFT liquid crystal display device, a driver IC voltage, a gate voltage, a counter voltage, and a liquid crystal application voltage. I do.

A gradation 13 has a plurality of gradation characteristics in which the relation between the gradation level and the gradation correction reference voltage value is different from each other, and generates a gradation correction reference voltage value based on the selected gradation characteristic. It is a voltage generation circuit. The gradation characteristic to be used is selected by a gradation selection signal, and a gradation correction reference voltage corresponding to the selected gradation characteristic is output from the gradation voltage generation circuit 13. Each gradation characteristic is set within a gradation voltage range determined by the relationship between the transmittance [%] and the applied voltage [V] according to various conditions such as a liquid crystal material and temperature.

A timing control IC 14 receives a control signal and display data and receives a source driver I.
Supply display data to C16 and source driver IC
16 and the gate driver IC 15.

Reference numeral 15 denotes a gate driver IC, which includes a shift register circuit, a level shift circuit, an output buffer circuit, and the like, and drives a gate of a TFT arranged for each pixel of the TFT liquid crystal panel 17.

Reference numeral 16 denotes a source driver IC, which includes a shift register circuit, a latch circuit, a D / A converter circuit, an output buffer circuit, etc., and controls a gradation correction reference voltage output from the gradation voltage generation circuit 13. By using this, a gradation voltage corresponding to a display signal having a gradation sent from the timing control IC 14 for each pixel is determined and supplied as a drive voltage to a corresponding source line of the liquid crystal display panel 17. .

Reference numeral 17 denotes a TFT liquid crystal panel, which is driven by a gate driver IC 15 and a source driver IC to perform screen display. Reference numeral 18 denotes a switch, which selects one gradation characteristic from a plurality of gradation characteristic parameters and supplies the selected gradation characteristic to the gradation voltage generation circuit 13 as a gradation selection signal. In this example, the switch 18 is not built in the panel, but is provided outside for easy operation. Also, here, it is assumed that one of the three gradation characteristics of the gradation voltage generation circuit 13 is selected by the 3-bit gradation selection signal, and the 3-bit gradation selection signal is directly used as the gradation. It is sent to the voltage generation circuit 13. Alternatively, a gradation selection signal may be input as one of the control signals, and the gradation characteristics used by the gradation voltage generation circuit 13 may be selectively controlled via the timing control IC 14.

FIG. 2 shows three types of gradation characteristics of the gradation voltage generation circuit 13. For example, the gradation characteristics of a CRT monitor, the gradation characteristics of a general TFT liquid crystal display device, and the gradation characteristics for increasing the gradation difference in a dark portion and improving the image recognizability are gradation characteristics 1 and 2, respectively. , Is defined as 3. A plurality of these different gradation characteristics are prepared in the gradation voltage generation circuit 13.

In FIG. 2, the ratio becomes brighter as the ratio becomes 100% and becomes darker as the ratio becomes 0%. The gradation level is 64
When the case of gradation is considered as an example, the 0th gradation is the leftmost end of the gradation and the 63rd gradation is the rightmost end of the gradation. Therefore, the gradation characteristics represent the ratio of left to right (dark → bright) or right to left (bright → dark). A plurality of gradation characteristics means that two curves having different ratios (curve shapes) as shown in the three types in the figure.
There is more than one. The voltage value of 100 [%] is always constant, and corresponds to the maximum voltage width determined by the relationship between the transmittance [%] and the applied voltage [V] due to various conditions such as the liquid crystal material and temperature. The maximum voltage width is the same for all gradation characteristics, and within the range of the voltage width, a gradation correction reference voltage value to be output for each gradation level is individually determined for each characteristic.

FIG. 3 shows a configuration example of the gradation voltage generation circuit 13. The grayscale voltage generating circuit 13 is provided with only X number of grayscale characteristics required. A first gradation characteristic 131 generates a gradation correction reference voltage value corresponding to each gradation level based on the first gradation characteristic. 132
Is a second gradation characteristic, and generates a gradation correction reference voltage value corresponding to each gradation level based on the second gradation characteristic. Reference numeral 133 denotes a third gradation characteristic, and a gradation correction reference voltage value corresponding to each gradation level is generated based on the third gradation characteristic. An X-th gradation characteristic 134 generates a gradation correction reference voltage value corresponding to each gradation level based on the X-th gradation characteristic.

Reference numeral 135 denotes a gradation selection circuit which selects and outputs one gradation characteristic to be used from a plurality of gradation characteristics. FIG. 4 shows an example of a gradation characteristic selection processing operation of the gradation voltage generation circuit 13.

First, in step S101, a gradation selection signal is generated by the above-described switch 18 connected to the panel, and a notification of which gradation characteristic is selected is made. Next, in step S102, a gradation characteristic to be used is selected in the gradation voltage generation circuit 13 based on the gradation selection signal, and a gradation correction reference voltage is generated according to the selected gradation characteristic. Thereafter, in step S103, the gradation correction reference voltage generated by the gradation voltage generation circuit 13 is supplied to the source driver 16.

FIG. 5 shows an example of a specific circuit configuration of the gradation voltage generating circuit 13. This gradation voltage generation circuit 13 has three voltage generation circuits 51, 52, and 53 corresponding to three gradation characteristics, respectively, and one of these three voltage generation circuits 51, 52, and 53 is a switch. The operation is selected by the selection signal from. The voltages A, B, and C are supplied from the voltage circuit 12 shown in FIG. 1, and the relationship between the transmittance [%] and the applied voltage [V] depending on various conditions such as the liquid crystal material and the temperature depends on the value of the voltage A. Determines the maximum gradation voltage width.

The voltage generation circuit 51 corresponds to the first gradation characteristic, and when selected by the switch 18, the gate of the transistor T1 is grounded, whereby the gate of the transistor T1 goes low, and The gate of T2 goes low, and a plurality of resistors R
3. A series circuit of Ry and the transistor T2 is activated, and a gradation correction reference voltage a to x corresponding to a resistance division value of the maximum gradation voltage width is output from a contact between each resistor and the transistor T2. Input to the driver. Then, the source driver divides and uses each gradation correction reference voltage.

The voltage generation circuits 52 and 53 respectively
And a third gradation characteristic, and the resistance division ratio forming the series circuit of the output stage is different from that of the voltage generation circuit 51, but the circuit configuration is the same as that of the voltage generation circuit 51.

As described above, the plurality of voltage generation circuits 51, 5
2 and 53 are each configured to generate a predetermined gradation correction reference voltage value for each gradation level within the same voltage range, so that which gradation characteristic among a plurality of gradation characteristics Even when the selection is made, the effective voltage supplied to each pixel via the source line is kept constant, so that the contrast can be kept constant even when the gradation characteristic is switched.

Next, the control operation of the TFT liquid crystal display of FIG. 1 will be described. Here, the gradation selection signal is TF
An example in which the information is output from an information terminal such as a personal computer using the T liquid crystal display device as a display monitor will be described. A display controller and a power supply circuit incorporated in an information terminal such as a personal computer provide display data, control signals, power supply, GND to the input terminal 11.
When the gradation selection signal is input, various power supplies created by the voltage circuit 12 and the timing controller 14
Are output to the gate driver IC 15 and the source driver IC 16, and the gate driver IC
15 and the source driver IC 16 drive control,
An image is displayed on the TFT liquid crystal panel 17.

At this time, the gradation characteristic is selected by a gradation selection signal, and a gradation correction reference voltage corresponding to the selected gradation characteristic is created by the gradation voltage generation circuit 13, which is used as the source driver IC 16. Output to Control IC 14
The grayscale voltage corresponding to the grayscale level of the display data sent for each pixel is determined by the source driver IC 16 based on the grayscale correction reference voltage, and is determined as the source line drive voltage of the TFT liquid crystal panel 17. Used.

As described above, a plurality of gradation characteristics are prepared in advance, and these gradation characteristics are selected by an external input such as a switch or a signal from an information terminal such as a personal computer. Image display can be performed by selecting the optimum gradation characteristic for the display purpose.

FIG. 6 shows a configuration example of a personal computer having a gradation characteristic selecting function. 61 is C
It is a PU and controls the operation of the entire personal computer by executing a program. A RAM 62 is used as a main memory, and is used for storing application programs and various data. 63 is BIOS
A ROM, in which a BIOS program for controlling various hardware of a personal computer is built;

Reference numeral 64 denotes a control IC composed of a gate array (GA), which functions as an interface for transmitting and receiving data between the BIOS and the power supply microcomputer 71. A display controller 65 controls the display of the TFT liquid crystal display device. The display controller 65 is a TFT
LCD display mode for screen display only on the liquid crystal display device,
It has a CRT display mode for displaying a screen only on an external CRT monitor that can be connected to a personal computer, and a simultaneous display mode for simultaneously displaying the same screen on a TFT liquid crystal display device and an external CRT monitor. It can be set / changed by key input such as a key, BIOS environment setting, and the like.

Reference numeral 66 denotes a keyboard controller (KBC)
Controls the data transmission / reception interface between the keyboard and the BIOS. Reference numeral 67 denotes a power supply circuit unit for supplying power to the system. The power supply section has a power supply microcomputer 71.

Reference numeral 100 denotes the TFT liquid crystal display device described with reference to FIG. 1, which has a gradation control terminal for inputting a gradation selection signal, and whose gradation characteristics change in accordance with the inputted gradation selection signal. Is configured.

A keyboard 69 transmits a key input from the user to the KBC 66. Reference numeral 70 denotes a C-MOS, which holds a hardware setup state. 71
A power supply microcomputer receives a gradation selection instruction through the BIOS and the control IC 64 or through the KBC 66 and the control IC 64, and generates a gradation selection signal in accordance with the instruction.

FIG. 7 shows a procedure of a display mode switching process using a hot key. Here, the hot key is a key for directly requesting the CPU 61 to switch various operation modes for setting / changing the system environment, etc. Assigned as that hot key. When this hot key is operated, a display mode change processing routine of the BIOS is called and executed by an interrupt signal to the CPU 61. In this hot key processing, unlike the normal key data transmission, the CPU 6
An interrupt signal such as an SMI is issued to the CPU 1 to notify the CPU 61 that the hot key has been pressed.

That is, as shown in FIG. 7A, when a hot key for switching the display mode prepared on the keyboard 69 is pressed, an interrupt signal is first sent to the CPU 61.
And the display mode change processing routine of the BIOS is called (step S201). Then the BI
The OS controls the display controller 65 to perform a display mode change process (step S202). As shown in FIG. 7B, the display mode is toggled every time a hot key for switching the display mode is pressed, and
D display mode, simultaneous display mode, CRT display mode, L
Change to CD display mode.

The BIOS executes the processing shown in FIG. 8 in response to such a display mode switching processing instruction. That is, first, a new display mode designated by the hot key is checked, and it is determined whether the new display mode is the simultaneous display mode or the LCD display mode (steps S401 and S4).
04). In the case of the simultaneous display mode, the power supply microcomputer 71
, A gradation selection command for the simultaneous display mode for realizing the same gradation characteristics as the CRT on the TFT liquid crystal display device is transmitted (step S402), and then the display controller 65 is set to the simultaneous display mode (step S402). Step S40
3). In response to the gradation selection command, the power supply microcomputer 71 outputs a gradation selection signal for selecting the gradation characteristics for the simultaneous display mode.

On the other hand, in the case of the LCD display mode, a gradation selection command for the LCD display mode for realizing, on the TFT liquid crystal display device, a dedicated gradation characteristic optimal for the characteristics of the LCD to the power supply microcomputer 71. Is transmitted (step S40).
5) Then, the display controller 65 is set to the LCD display mode (step S406). In response to the gradation selection command, the power supply microcomputer 71 outputs a gradation selection signal for selecting gradation characteristics for the LCD display mode.

If the display mode is the CRT display mode, the display controller 65 is set to the CRT display mode (step S407). As described above, by switching the gradation characteristics in conjunction with the display mode, the gradation characteristics characteristic of a TFT can be automatically set in the LCD display mode, and the gradation characteristics of the CRT can be automatically set in the simultaneous display mode. By automatically setting the TFT LCD display,
The image displayed on the LCD and the image displayed on the CRT can have the same characteristics.

[0038]

As described above, according to the present invention,
A plurality of gradation characteristics are prepared in advance in the gradation voltage generation circuit of the liquid crystal display device. For example, a switch that can be operated by a user or a gradation that is used in accordance with a selection signal from a computer that uses the liquid crystal display device as a display monitor. The key characteristic is selected. As a result, a screen display can be performed by selectively using a plurality of gradation characteristics, and the gradation characteristics can be switched according to a display image or a use. Also,
In particular, the gradation characteristics can be automatically switched in conjunction with the switching of the display mode of the computer. In the case of using the characteristics and performing simultaneous display on the CRT monitor and the liquid crystal display device, control is automatically performed such as using a gradation characteristic that can obtain the same gradation as seen on the CRT monitor. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is an exemplary view for explaining a plurality of gradation characteristics prepared in the liquid crystal display device of the embodiment.

FIG. 3 is an exemplary view showing a basic configuration of a gradation voltage generation circuit provided in the liquid crystal display device of the embodiment.

FIG. 4 is an exemplary view showing a gradation characteristic selecting operation in the liquid crystal display device of the embodiment.

FIG. 5 is a circuit diagram showing an example of a specific configuration of a gradation voltage generation circuit provided in the liquid crystal display device of the embodiment.

FIG. 6 is an exemplary view showing a configuration of a personal computer using the liquid crystal display device of the embodiment as a display panel.

FIG. 7 is an exemplary view for explaining a display mode switching operation by a hot key in the personal computer of FIG. 6;

FIG. 8 is a view for explaining a gradation characteristic selecting operation automatically executed in conjunction with the display mode switching operation in the personal computer of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Input terminal 12 ... Voltage circuit 13 ... Grayscale voltage generation circuit 14 ... Timing control IC 15 ... Gate driver IC 16 ... Source driver IC 17 ... Liquid crystal panel 18 ... Switch

Claims (6)

[Claims] 1. A liquid crystal display device for driving each image of a liquid crystal panel using a gray scale voltage corresponding to an input signal, wherein a plurality of gray scale characteristics differing in a relationship between a gray scale level and a gray scale correction reference voltage value. A grayscale voltage generation means for generating a grayscale correction reference voltage value based on the selected grayscale characteristic; and a grayscale correction reference voltage value generated by the grayscale voltage generation means and an input signal. And a driving means for driving each image of the liquid crystal panel on the basis of the plurality of gradation characteristics, so that a plurality of gradation characteristics can be selectively used. 2. The liquid crystal display according to claim 1, wherein said gray scale voltage generation means selects a gray scale characteristic to be used based on a gray scale characteristic selection signal inputted from outside the liquid crystal display device. apparatus. 3. The gray-scale voltage generating means is provided corresponding to each of the plurality of gray-scale characteristics, and is configured to generate a plurality of gray-scale correction reference voltages according to the corresponding gray-scale characteristics. A plurality of gradation voltage generation circuits; and means for selecting a gradation voltage generation circuit corresponding to a gradation characteristic selected from among the plurality of gradation characteristics, wherein the selected gradation voltage generation circuit is provided. 2. The liquid crystal display device according to claim 1, wherein a gradation correction reference voltage value output from the control unit is supplied to the driving unit. 4. The plurality of gradation voltage generating circuits are configured to generate a predetermined gradation correction reference voltage value for each gradation level within a range of the same voltage width. 4. The liquid crystal display device according to claim 3, wherein the effective voltage for driving each pixel is kept constant regardless of which of the plurality of gradation characteristics is used. 5. A computer system using a liquid crystal display device for driving each image of a liquid crystal panel using a gradation voltage corresponding to an input signal as a display monitor, wherein the liquid crystal display device has a gradation level and a gradation correction. It has a plurality of gradation characteristics different from each other with respect to a reference voltage value, and is configured to generate a gradation voltage value for driving each image of the liquid crystal panel using the selected gradation characteristics. A first display mode for displaying a screen on the liquid crystal display device, and a second display mode for simultaneously displaying a screen on the liquid crystal display device and an external CRT display connectable to the computer system.
A display control means for controlling a screen display in any one of these display modes; and a liquid crystal display comprising a gradation selection signal for switching a gradation characteristic to be selected in response to the switching of the display mode. A computer system, comprising: means for supplying to a display device. 6. A display mode of said display control means is configured to be switched in response to a predetermined key input, and a gradation characteristic of said liquid crystal display device is switched in response to said key input. The computer system according to claim 5, wherein