CN104678621B - Liquid crystal display device - Google Patents

Abstract

The present invention provides a kind of liquid crystal display device, the chip on film, circuit board, and polytype terminal is equipped with liquid crystal display panel, terminal one end terminal corresponding with circuit board of chip on film, other end terminal connection corresponding with liquid crystal display panel, distance s between terminals of adjacent are identical, one of which terminal is high voltage terminal, the transverse width D of the high voltage terminal is more than the transverse width d of other terminals, and the transverse width d all sames of other terminals, the transverse width D of the high voltage terminal is equal to the transverse width sum of other n (n >=2) individual terminals of adjacent plus the spacing sum between several terminals, i.e.：D=nd+ (n 1) s.The present invention is not reducing high voltage shutdown electric current, in the case of not changing other positions wiring, is reducing the heat that electric current is produced by using the mode of reduction junction impedance, and heat is discharged as early as possible, so as to reduce the probability of the damage of chip on film.

Description

Liquid crystal display device

technical field

The invention relates to a liquid crystal display device which can completely open TFTs when the liquid crystal display panel is closed to solve the afterimage phenomenon after shutdown.

Background technique

When the TFT-LCD liquid crystal display device is turned off, if the residual charge in the pixel cannot be released in time, a "tide" phenomenon will occur, that is, the display cannot be turned from the on state to the off state immediately after a few seconds or even longer after the power is turned off. State, but gradually change, this phenomenon is called the phenomenon of afterimage after shutdown. The reason for this phenomenon is that the scanning lines of the liquid crystal display are turned on one by one, and the time of each turn is very short, so when the power is turned off, the charge remaining in the pixel cannot be released in time through the data line in time. As shown in Figure 1, it is a schematic diagram of the phenomenon of afterimage after power off. The state of the normally black (normally black) panel changes from the white state to the black state when the power off, and the afterimage phenomenon after power off occurs.

In order to improve this phenomenon, a TFT All-Output-on circuit will be added to the scan drive circuit, as shown in Figure 2, when the power is turned off, a high voltage VGH is applied to the TFT gate Gate (n) 10, All the TFT switches 30 are turned on at the same time, and the remaining charge on the pixel is released through the data line Source(m) 20 in time, so that the overall picture has the same voltage and gray scale, thereby eliminating the afterimage after power off.

However, turning on the TFT switch at the same time requires a large high-voltage VGH surge current, which generates a lot of heat and burns the chip-on-film (COF: Chip On Flex, or, Chip On Film, which fixes the IC on the flexible circuit board). This method will cause a large VGH surge current at the moment of shutdown, as shown in Figure 3, the waveform diagram of the voltage during normal display and shutdown. At the same time, the scanning lines in the LCD panel are turned on one by one, so that the VGH required to turn on the TFT each time only needs to act on one scanning line, and this action time is very short. For example, for a liquid crystal display with a resolution of 1366*768 and a refresh rate of 60 Hz, the time to turn on the TFT does not exceed 1/768*60=21.7 microseconds (us); The number is 768, and the opening time will be millisecond (ms) level.

The chip-on-film in the source direction is called source chip-on-film 1 , and the chip-on-film in the gate direction is called gate chip-on-film 2 .

The large current during shutdown will generate a lot of heat on the path through which it flows. In the direction of the source, the position where the source chip-on-chip film 1 contacts the circuit board 3 is the first contact 4, the source chip-on-chip film 1 The contact position with the wiring 4 on the panel side is the second contact point 5, and the formula for the heat generated by the shutdown current is:

Q = I2RT

Among them, Q refers to the heat generated by the shutdown current, I refers to the VGH current I-VGH during shutdown, R refers to the impedance on the current path, and T refers to the action time.

At the first contact 4 where the source chip-on-chip film 1 is in contact with the circuit board 3, and the second contact 5 where the source chip-on-chip film 1 contacts the wiring 4 at the panel end, because it passes through the ACF (anisotropic conductive glue) , Anisotropic Conductive Film, referred to as: ACF) for connection, as shown in Figure 4 and Figure 5, because the impedance is relatively large, a lot of heat will be accumulated through a large current at the moment of shutdown, and the source chip-on-chip film 1 is easily damaged.

The position where the circuit board is connected to the COF is the connecting finger on the circuit board, which is called the circuit board gold finger.

The connection between the gold finger of the circuit board and the chip-on-chip film, and the connection between the chip-on-chip film and the terminals on the side of the LCD panel are all connected through the terminals on the pins. As shown in Figure 6, the pin position of the gold finger 3 of the circuit board, the chip-on-chip film 1 There are several pin terminals on the pins of the LCD panel side and the pins of the side 2 of the LCD panel, including: low voltage VGL terminal 4, power supply voltage VCC terminal 5, high voltage VGH terminal 6, ground voltage GND terminal 7, each terminal There are several. In this embodiment, there are three terminals of each type, and all terminals have the same width and spacing. FIG. 6 only shows a schematic diagram of several terminals.

Both ends of the low-voltage pin terminal 4 of the source chip-on-chip film 1 are respectively connected to the low-voltage pin terminal 4 of the gold finger 3 of the circuit board and the low-voltage pin terminal 4 of the liquid crystal display panel 2, and the source chip-on-chip film 1 The two ends of the power supply voltage pin terminal 5 are respectively connected to the power supply voltage pin terminal 5 of the gold finger 3 of the circuit board and the power supply voltage pin terminal 5 of the liquid crystal panel side 2, and the high voltage pin terminal of the source chip-on-chip film 1 The two ends of 6 are respectively connected to the high voltage pin terminal 6 of the golden finger 3 of the circuit board and the high voltage pin terminal 6 of the crystal display panel 2, and the two ends of the ground voltage pin terminal 7 of the source chip-on-chip film 1 are respectively connected to the The ground voltage pin terminal 7 of the golden finger 3 of the circuit board is connected to the high ground voltage pin terminal 7 of the liquid crystal panel side 2 .

In order to reduce the accumulation of heat, there are two ways, one is to reduce the VGH surge current value, and the other is to reduce the impedance value on the current path. If the VGH surge current value is limited during shutdown, VGH will not be able to fully act on the gate of the TFT in fact, that is, the TFT cannot be fully opened at the moment of shutdown, and the residual charge in the pixel cannot be released quickly. Shadow resolution will be reduced.

Contents of the invention

The invention provides a liquid crystal display device which solves the residual image after shutdown.

The invention provides a liquid crystal display device, which includes a liquid crystal display panel, a chip-on-chip connected to the liquid crystal display panel, and a circuit board connected to the chip-on-film, and the chip-on-film, the circuit board, and the liquid crystal display panel are all equipped with Various types of terminals, one end of the terminal of the chip-on-chip film is connected to the corresponding terminal on the circuit board, and the other end is connected to the corresponding terminal on the liquid crystal display panel, the distance s between adjacent terminals is the same, and each type of terminal includes One, two, three or more terminals, one of which is a high-voltage terminal, the lateral width D of the high-voltage terminal is greater than the lateral width d of the other terminals, and the lateral width d of the other terminals is the same, said The lateral width D of the high-voltage terminal is equal to the sum of the lateral widths of the other n adjacent terminals plus the sum of the spacing between the other n adjacent terminals, that is: D=nd+(n-1)s, where n≥ 2.

Wherein, when the liquid crystal display panel is turned off, the TFT switch in the panel is turned on at the same time.

Among them, n is equal to 3.

Wherein, other terminals include: DUMMY terminal, NC terminal, VCOM terminal, VCOMTFT terminal, VGL terminal.

Wherein, the chip-on-film includes a gate chip-on-film and a source chip-on-film, one terminal of the liquid crystal display panel is connected to the gate chip-on-film, and the other end is connected to the source chip-on-film.

Wherein, the high voltage terminal is on the source COF.

Wherein, the high-voltage terminal is on the gate-on-chip film.

Wherein, the high voltage terminal is on the source COF and the gate COF.

The invention is applied to the connection between the circuit board terminal and the chip-on-chip film of TFT-LCD, and the connection between the chip-on-chip film and the liquid crystal display panel, to deal with the reliability problem caused by excessive surge current; by reducing the contact impedance and facilitating heat dissipation, the The terminals with large surge current are merged into a whole without changing the distribution of other electrical signal terminals.

The invention reduces the heat generated by the current and releases the heat as soon as possible without reducing the high-voltage shutdown current and changing the wiring at other positions by reducing the impedance of the connection, thereby reducing the damage of the chip-on-chip film The probability.

Description of drawings

FIG. 1 is a schematic diagram of the phenomenon of afterimage after shutdown;

Fig. 2 shows the circuit diagram in which all TFTs are turned on when the existing power is turned off;

Figure 3 shows the waveform diagram of the existing normal display and voltage during shutdown;

Figure 4 shows the comparison test diagram of the VGH current when the current shutdown and normal display;

Figure 5 is a schematic diagram of the wiring of the existing panel;

Figure 6 is a schematic diagram of terminal connections in the existing panel;

Fig. 7 is a schematic structural diagram of the high voltage terminal of the present invention;

Fig. 8 is a schematic diagram of terminal connection in the panel of the present invention;

FIG. 9 is a schematic diagram of terminal distribution of gold fingers of an existing circuit board;

FIG. 10 is a schematic diagram showing the terminal distribution of the gold finger of the circuit board according to the present invention.

detailed description

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention Modifications in equivalent forms all fall within the scope defined by the appended claims of this application.

Fig. 7 shows the schematic structural diagram of the high-voltage VGH terminal of the liquid crystal display panel of the present invention. In order to reduce the crimping impedance, the method of enlarging the contact area is adopted, and the design of the high-voltage VGH terminal 60 is different from that of other signal terminals. The high-voltage VGH terminal corresponding to the high-voltage VGH signal is no longer the same as other terminals, but all the corresponding high-voltage VGH terminals are connected together, there is no gap in the middle, and the horizontal width of the high-voltage VGH terminal is equal to other terminals of the same type. Therefore, without changing other terminals, the contact area is increased and the contact resistance is reduced. At the same time, due to the increase of the contact area, the speed of heat dissipation is accelerated, and the probability of COF damage is also reduced.

As shown in Figure 8, when the liquid crystal display device of the present invention is turned off, in order to eliminate the afterimage phenomenon after shutdown, it is necessary to use a high voltage VGH to turn on all the TFTs so that the charge in the pixel capacitor can be released as soon as possible. At this time, the required VGH The larger the current, the greater the heat generated in the path it flows through, especially at the connection between the chip-on-chip film and the circuit board and the liquid crystal display panel. The resistance is higher, and it is easier to accumulate heat and cause damage.

The liquid crystal display device comprises a liquid crystal display panel 2, a chip-on-film 1 connected to the liquid crystal display panel 2, and a circuit board 3 connected to the chip-on-film 1, and only the pin position of the chip-on film 1 and the pin position of the golden finger 3 of the circuit board are changed. 1. The high-voltage VGH terminals 60 at the pins of the liquid crystal display panel 2 do not change the terminal data and arrangement at other pins. By enlarging the contact area and reducing the contact impedance, the probability of burning the chip-on-chip film is reduced.

Figure 9 is a schematic diagram of the distribution of pins 1-114 at the gold finger of the existing circuit board, where DUMMY and NC represent empty terminals, VCOM, VCOMTFT, VGH, and VGL are power signal terminals, and DUMMY terminals and NC terminals , VCOM terminal, VCOMTFT terminal, VGL terminal, each terminal includes one, two, three or more terminals, these signal terminals are generated from the circuit board, and are transmitted to the source driver chip and gate through the chip-on-chip film Driver chips, and liquid crystal display panels. When the circuit board and the liquid crystal display panel are crimped through the chip-on-chip film, in order that various electrical signals can be correctly connected to the source driver chip and the gate driver chip, and finally the required voltage signal is added to the inside of the liquid crystal panel, the chip-on-chip film, The gold finger of the circuit board and the terminal assignment of the LCD panel are the same. The width and indirection of each existing terminal are the same. In this embodiment, the lateral width d of each terminal is 8mil (1mil=0.0254mm), and the distance between the centers of two terminals is 14mil, that is, the distance between adjacent terminals The pitch s is 6mil, and the width of all 114 terminals is exactly the same as the gap design.

Fig. 10 is a schematic diagram of the pin position distribution of the gold finger of the circuit board of the present application. By combining the original high-voltage VGH terminals 60 of Nos. 22, 23, and 24 from the original separated state, they are combined into the same terminal pin, and the combined terminals must have the same electrical signal , and there are no other electrical signal terminals between them, so that the width of the original three terminals is 8*3=24mil, and merged into one place, the lateral width D of the new high-voltage terminal is equal to the lateral width of the other three adjacent terminals The sum of the width d plus the sum of the spacing s between the three terminals, that is: D=3d+2s, 3*8+2*6=36mil, so that the contact will be made without changing the distribution of other pins The larger the area, the lower the crimping resistance. At the same time, due to the larger contact area, the heat dissipation will be relatively improved.

The high-voltage terminals in the above embodiments are 3 terminals combined, and in other embodiments, there may be 2 or 4 or more terminals.

The aforementioned chip-on-film is finally the source chip-on-film, and of course other conditions can also be that the gate chip-on film, or the source chip-on-film and the source chip-on-film are designed with such a high-voltage terminal.

Claims (8)

1. a kind of liquid crystal display device, it include liquid crystal display panel, the chip on film being connected with liquid crystal display panel and with The circuit board of chip on film connection, it is characterised in that：It is equipped with the chip on film, circuit board and liquid crystal display panel many On type terminal, terminal one end terminal connection corresponding with circuit board of chip on film, the other end and liquid crystal display panel Distance s between the connection of corresponding terminal, terminals of adjacent are identical, each type of terminal include one, two, three or More terminals, one of which terminal is high voltage terminal, and the transverse width D of the high voltage terminal is more than the transverse direction of other terminals Width d, and the transverse width d all sames of other terminals, the transverse width D of the high voltage terminal are equal to other n abutting end The transverse width sum of son adds the spacing sum between other n terminals of adjacent, i.e.,：D=nd+ (n-1) s, wherein n >=2.

2. liquid crystal display device according to claim 1, it is characterised in that：Liquid crystal display panel is opened simultaneously in shutdown TFT switch in panel.

3. liquid crystal display device according to claim 1, it is characterised in that：N is equal to 3.

4. liquid crystal display device according to claim 1, it is characterised in that：Other terminals include：DUMMY terminals, NC ends Son, VCOM terminals, VCOMTFT terminals, VGL terminals.

5. liquid crystal display device according to claim 1, it is characterised in that：The chip on film includes grid chip on film With source electrode chip on film, terminal one end of liquid crystal display panel is connected with grid chip on film, the other end and source electrode chip on film Connection.

6. liquid crystal display device according to claim 5, it is characterised in that：High voltage terminal is in source electrode chip on film.

7. liquid crystal display device according to claim 5, it is characterised in that：High voltage terminal is in grid chip on film.

8. liquid crystal display device according to claim 5, it is characterised in that：High voltage terminal is in source electrode chip on film and grid In the chip on film of pole.