JP2004029571A - Liquid crystal display device and device and method for adjusting vcom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device wherein the efficiency of the operation for adjusting a Vcom (common electrode voltage) can be increased and to provide a device and a method for adjusting the Vcom. <P>SOLUTION: A circuit 303 for adjusting the Vcom is provided outside a driving circuit 103 and all signal lines except the second signal line from the right end are disconnected in this figure. A panel ID is memorized by adding a circuit element onto each signal line and disconnecting each signal line. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device used for a mobile communication terminal or the like, and a Vcom adjustment device and method thereof.
[0002]
[Prior art]
FIG. 4 is a diagram showing a pixel configuration of a conventional liquid crystal panel. 4, reference numerals 407a and 407b denote scanning signal wirings connected to the scanning side driving circuit (103 in FIG. 1), 408a to 408c display signal wirings connected to the signal side driving circuit (102 in FIG. 1), 409a and Reference numeral 409b denotes a switching element such as a TFT disposed at the intersection of the scanning signal wirings 407a and 407b and the display signal wirings 408a to 408c, and 410a and 410b denote pixel electrodes connected to the switching elements 409a and 409b.
[0003]
FIG. 5 is a sectional structural view showing a pixel of a conventional liquid crystal panel. In FIG. 5, reference numeral 507 denotes a glass substrate on which pixel electrodes 410a and 410b are formed for each pixel (hereinafter, referred to as an array substrate). Scanning signal lines 407a and 407b and display signal lines 408a to c, switching elements 409a and 409b are also formed. Reference numeral 501 denotes a glass substrate (hereinafter, referred to as a common electrode substrate) disposed to face the array substrate 507, reference numeral 503 denotes a counter electrode formed on the entire surface of the common electrode substrate 501, and reference numeral 505 denotes an array substrate 507 and the common electrode substrate 501. The liquid crystal is sandwiched and sealed.
The waveform diagram of FIG. 6 shows the relationship between the drive waveform 601 and the common electrode potential 607. In FIG. 6, reference numeral 601 denotes a part of the driving waveform of the TFT liquid crystal panel, and VCOMH and VCOML indicate the upper and lower limits of the common electrode potential 607, respectively.
[0004]
In the liquid crystal display configured as described above, the polarity of the display signal is generally inverted every frame period in order to prevent screen burn-in or the like. Therefore, in the case of FIG. 6, the voltage applied to the liquid crystal is 603 for a positive polarity and 605 for a negative polarity. However, when this voltage value is different between the positive polarity (603) and the negative polarity (605), flicker called flicker occurs.
[0005]
In order to reduce this flicker, it is necessary to adjust the level of the common electrode potential (hereinafter, referred to as Vcom) so that the voltage applied to the liquid crystal during the positive polarity and the voltage applied to the liquid crystal during the negative polarity become equal. Specifically, an image in which flicker is easily recognized is displayed on the screen, the level of the Vcom provided on the liquid crystal display is adjusted, and setting is made so that the degree of flicker is minimized visually.
[0006]
In this case, since the outputs of the liquid crystal display and the driving IC have individual differences, it is necessary to adjust Vcom for each individual module. Since the Vcom adjustment value obtained as described above was stored in the memory of the main body when the liquid crystal display was incorporated into the main body, it could not be adjusted as a single liquid crystal display module.
[0007]
Further, in order to adjust Vcom at the time of assembling as described above, work equipment and human resources are required, so that a burden is imposed on a mobile phone manufacturer.
As a countermeasure, there is a method of incorporating a variable resistor and a fuse in the liquid crystal display module to adjust Vcom, and a method of installing a memory in the liquid crystal display module to store an appropriate value of Vcom, but the production cost is high. There was a disadvantage of becoming.
[0008]
[Problems to be solved by the invention]
The present invention has been made in consideration of the above points, and has as its object to provide a liquid crystal display device capable of improving the efficiency of Vcom adjustment.
Another object of the present invention is to provide a liquid crystal display device capable of reducing Vcom adjustment cost.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, the liquid crystal display device of the present invention includes an adjustment circuit for adjusting a common electrode potential applied to a common electrode of a liquid crystal panel, and optimizing an alternating current balance of a liquid crystal driving voltage, and adjusting the adjustment circuit. The circuit is provided with storage means for storing the adjustment value.
It is preferable that the adjustment circuit includes a predetermined number of signal lines and circuit elements.
[0010]
The Vcom adjustment device of the present invention is a device for adjusting a common electrode potential applied to a common electrode of a liquid crystal panel and optimizing an alternating current balance of a liquid crystal driving voltage. It is characterized by comprising means for reading an ID and means for obtaining VCOMH and VCOML from the panel ID.
The Vcom adjustment method of the present invention is a method of adjusting a common electrode potential applied to a common electrode of a liquid crystal panel and optimizing an alternating balance of a liquid crystal drive voltage, and measuring VCOMH and VCOML; And a step of determining a difference between VCOML and each reference value, a step of determining a panel ID from the difference, a step of providing an adjustment circuit created based on the panel ID in the liquid crystal display device, and a step of providing the liquid crystal display device with The method includes a step of reading a panel ID from the adjustment circuit and a step of obtaining VCOMH and VCOML from the panel ID.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described in detail with reference to FIGS. Here, FIG. 1 is a block diagram for explaining an embodiment of the present invention, FIGS. 2 and 3 are enlarged views of a Vcom adjustment circuit for explaining the embodiment of the present invention, and FIG. 7 shows a Vcom lookup table. FIG. 8 is an operation flowchart of the Vcom adjustment software, and FIG. 9 is a circuit diagram of the liquid crystal display according to the embodiment of the present invention.
[0012]
(1) Description of Overall Configuration of Liquid Crystal Display FIG. 1 is a block diagram showing a liquid crystal display according to an embodiment of the present invention. In the figure, reference numeral 101 denotes a liquid crystal panel in which liquid crystal is sandwiched between two glass substrates; 102, a signal side driving IC for driving the liquid crystal panel 101; 103, a scanning side driving IC for driving the liquid crystal panel 101; The control circuit supplies a control signal to the driving IC 102 and the scanning-side driving IC 103. Reference numeral 105 denotes a scanning signal supplied by the control circuit 104, and reference numeral 106 denotes a display signal supplied by the control circuit 104.
FIG. 9 is a circuit diagram of a liquid crystal display according to an embodiment of the present invention. The liquid crystal panel 101 is connected to a drive circuit 103 (here, the scan side drive IC 103 in FIG. 1 but may be a signal side drive IC 102) by a signal line, and a Vcom adjustment circuit 903 is provided outside the drive circuit 103. Is provided.
[0013]
(2) Description of Vcom Adjustment Circuit FIGS. 2 and 3 are enlarged views of the Vcom adjustment circuit according to the embodiment of the present invention. Referring to FIG. 2, the Vcom adjustment circuit 203 including four signal lines is provided outside the driving circuit 103 (here, the scanning side driving IC 103 in FIG. 1 is used, but the signal side driving IC 102 may be used). A resistor 201 is added on the second signal line from the right end. On the other hand, referring to FIG. 3, the Vcom adjustment circuit 303 is provided outside the drive circuit 103 similarly to FIG. 2, but in the case of FIG. 3, all the signal lines except the second signal line from the right end are disconnected. Have been. As a cutting method, there is a method using a laser or the like.
[0014]
In the embodiment of the present invention, a liquid crystal display manufacturer measures VCOMH and VCOML on a production line, and obtains a panel ID based on a difference between the measurement result and each reference value. Then, as shown in FIGS. 2 and 3, the panel ID is stored by adding a circuit element to each signal line or cutting each signal line.
For example, each digit of the panel ID is associated with each signal line, the digit of the panel ID corresponding to the disconnected signal line is 0, and the digit of the panel ID corresponding to the signal line to which the circuit element is added is 1 and the like. Define it.
[0015]
(3) Description of Vcom Reference Table FIG. 7 is a diagram showing an example of the Vcom reference table according to the embodiment of the present invention. The first column of the table is a panel ID field, the second column is a ΔVCOMH field, and the third column is a ΔVCOML field.
The panel ID field stores a panel ID that can be read from the Vcom adjustment circuit (203 in FIG. 2 and 303 in FIG. 3).
The difference between the upper limit value of Vcom of the liquid crystal display to be adjusted and the reference upper limit value of Vcom is stored in the ΔVCOMH field.
[0016]
Therefore, the following two equations can be considered as a calculation equation for obtaining VCOMH.
In this embodiment, Equation 1 is adopted.
Formula 1) VCOMH = reference upper limit value + ΔVCOMH
Equation 2) VCOMH = reference upper limit value-ΔVCOMH
Similarly, the difference between the lower limit of Vcom of the liquid crystal display to be adjusted and the reference lower limit of Vcom is stored in the ΔVCOML field.
Therefore, the following two equations can be considered as a calculation equation for obtaining VCOML.
In this embodiment, Equation 3 is adopted.
Equation 3) VCOML = reference lower limit value-ΔVCOML
Equation 4) VCOML = reference lower limit + ΔVCOML
[0017]
(4) Description of Vcom adjustment software 4-1. Description of Operation Flowchart FIG. 8 is an operation flowchart of the Vcom adjustment software according to the embodiment of the present invention. The Vcom adjustment device according to the embodiment of the present invention incorporates the Vcom adjustment software, obtains a panel ID from a Vcom adjustment circuit (FIGS. 2 and 3) installed in the liquid crystal display by a liquid crystal display manufacturer, and based on the panel ID. Vcom adjustment is performed. Hereinafter, this flowchart will be described with reference to FIG.
[0018]
After the processing is started, first, the panel ID is read from the Vcom adjustment circuit (S801). Next, with reference to the Vcom reference table (S803), ΔVCOMH and ΔVCOML corresponding to the panel ID read in S801 are searched.
After the search, VCOMH is set based on ΔVCOMH and Equation 1 (VCOMH = reference upper limit value + ΔVCOMH) (S805). Subsequently, VCOML is set based on ΔVCOML and Expression 3 (VCOML = reference lower limit−ΔVCOML) (S807).
[0019]
4-2. Description Using Specific Numerical Values The processing in S805 to S807 in FIG. 8 will be described using numerical values in the Vcom reference table shown in FIG. Here, the unit of the ΔVCOMH field and the ΔVCOML field is [mV].
For example, when the panel ID is 0002, ΔVCOMH and ΔVCOML are each “0050”. Therefore, ΔVCOMH and ΔVCOML become 50 mV. Further, assuming that the reference upper limit of Vcom = 4500 mV and the reference lower limit = 1500 mV,
Formula 1) VCOMH = 4500 mV + ΔVCOMH
Formula 3) VCOML = 1500 mV−ΔVCOML
VCOMH = 4550 mV and VCOML = 1450 mV.
[0020]
【The invention's effect】
As described above, according to the liquid crystal display device, the Vcom adjustment device, and the method of the present invention, it is possible to increase the work efficiency of Vcom adjustment.
Further, according to the liquid crystal display device, the Vcom adjustment device and the method of the present invention, the cost of Vcom adjustment can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a liquid crystal display according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a Vcom adjustment circuit according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a Vcom adjustment circuit according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a pixel configuration of a conventional liquid crystal panel.
FIG. 5 is a sectional structural view showing a pixel of a conventional liquid crystal panel.
FIG. 6 is a waveform chart showing a relationship between a driving waveform and a common electrode potential.
FIG. 7 is a diagram showing a panel ID reference table.
FIG. 8 is an operation flowchart according to the embodiment of the invention.
FIG. 9 is a circuit diagram of a liquid crystal display which is an embodiment of the present invention.
[Explanation of symbols]
101 liquid crystal panel 102 signal side drive IC
103 Scanning drive IC
104 control circuit

Claims (4)

A liquid crystal display device comprising an adjustment circuit for adjusting a common electrode potential applied to a common electrode of a liquid crystal panel and optimizing an alternating current balance of a liquid crystal drive voltage, wherein an adjustment value is stored in the adjustment circuit. A liquid crystal display device comprising the storage means of (1). The liquid crystal display device according to claim 1,
2. A liquid crystal display device according to claim 1, wherein said storage means comprises a predetermined number of signal lines and circuit elements. A Vcom adjustment device for adjusting a common electrode potential applied to a common electrode of a liquid crystal panel and optimizing an alternating current balance of a liquid crystal driving voltage,
Means for reading a panel ID from an adjustment circuit provided in the liquid crystal display device;
A means for obtaining VCOMH and VCOML from the panel ID. A Vcom adjustment method for adjusting a common electrode potential applied to a common electrode of a liquid crystal panel and optimizing an alternating current balance of a liquid crystal driving voltage,
Measuring VCOMH and VCOML;
Determining a difference between the VCOMH and the VCOML and each reference value;
Determining a panel ID from the difference;
Providing a liquid crystal display device with an adjustment circuit created based on the panel ID;
Reading a panel ID from an adjustment circuit provided in the liquid crystal display device;
Obtaining a VCOMH and a VCOML from the panel ID.

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