JPH1074062A - Bidirectional shift register and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To symmetrically invert a screen and to improve the versatility using a simply constituted bidirectional shift register in the driving circuit incorporated type liquid crystal display(LCD) employing polysilicon thin film trnasisotrs (p-SiTFTs). SOLUTION: Clock signals CLK and inverse clock signals *CLK, which are supplied to every stage of a bidirectional shift register, are supplied to one of the inputs of EXOR gates 4 and shift direction switching signals CHN are supplied to the other inputs. By controlling the Hi/Lo of the signals CHN, the inversion/non-inversion of the signals CLK and *CLK are controlled. Note that the shifting directions of the signals CHN are switched to either to the left or to the right by integrally conducting the controls of the start pulse supply terminals and left and right direction switchings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit integrated type in which thin film transistors (TFTs) are arranged in a matrix in a display pixel portion and a driving circuit constituted by using the same TFT is integrally built. BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display (LCD), and more particularly to a liquid crystal display (LCD) that can switch the operation direction of a drive circuit unit to increase the degree of display freedom.

[0002]

2. Description of the Related Art LCDs have advantages such as small size, thin shape, and low power consumption, and are being put to practical use in fields such as OA equipment and AV equipment. In particular, an active matrix type using a TFT as a switching element can perform static driving with a duty ratio of 100% in principle in a multiplex manner, and is used for a large-screen, high-definition moving image display.

An active matrix LCD has a substrate in which TFTs are connected to display electrodes arranged in a matrix (TFF substrate) and a substrate having a common electrode (counter substrate).
Are bonded together with a liquid crystal interposed therebetween. The opposing portion between the display electrode and the common electrode is a pixel capacitance using a liquid crystal as a dielectric layer, and is sequentially selected by a TFT and a voltage is applied. The voltage applied to the pixel capacitor is the OF of the TFT.
It is held for one field period by the F resistor. The liquid crystal has electro-optical anisotropy, and the amount of transmitted light is adjusted according to the intensity of the electric field formed by the pixel capacitance. In this way, the distribution of light and dark whose transmittance is controlled for each pixel is visually recognized as a desired display image.

In recent years, by using polycrystalline (poly) silicon (p-Si) as a channel layer of a TFT,
An LCD integrated with a driving circuit in which a matrix display section and a peripheral driving circuit section are formed on the same substrate has been developed. Generally, p-Si has a higher mobility than amorphous silicon (a-Si). Therefore, the size of the TFT is reduced, and high definition is realized. Further, since high-speed operation can be achieved by miniaturization and reduction of parasitic capacitance by the gate self-alignment structure, a high-speed driving circuit can be formed by forming an n-ch TFT and a p-ch CMOS transistor. As described above, by integrally forming the drive circuit portion and the matrix display portion on the same substrate, reduction in manufacturing cost and downsizing of the LCD module can be realized.

FIG. 7 is a block diagram of the LCD. The central matrix section is a display section. A gate line (GL) serving as a scanning line and a drain line (DL) serving as a signal line are arranged and formed horizontally and vertically, and a TFT (SE) is formed at an intersection thereof. A pixel capacitance (LC) for driving a liquid crystal and an auxiliary capacitance (SC) for holding a charge are connected to the TFT (SE). TFT (SE) and its line (GL, DL)
The display electrode forming one of the pixel capacitances (LC) is formed on the same substrate, and the common electrode forming the other of the pixel capacitances (LC) is entirely formed on another substrate opposed to the liquid crystal layer. Is formed. That is, the liquid crystal and the common electrode are divided by the display electrode in the pixel capacitance (LC), and T
FT (SE) is connected to form a display pixel.

A drain driver (DD) mainly composed of a horizontal shift register and a sampling circuit and, in some cases, a hold capacitor are provided around the display section.
And a gate driver (GD) mainly composed of a vertical shift register. These gate driver (GD) and drain driver (DD) are TF
T CMOS array, and the T
Like FT (SE), they are integrally formed on the same substrate using p-Si.

[0007]

In recent years, in applications such as a three-panel projector, the displayed images are inverted depending on the installation positions of the three LCDs, and inconsistencies in the projected images occur. In some cases, in order to prevent this, the method of arranging the LCD is limited. Also, in order to reduce the manufacturing cost by small-type and mass-production by using the same LCD for the three LCDs, the write position of the display data must be vertically and symmetrically reversible. No.

When the shift direction of the shift register is switchable between left and right, if the shift clocks at the left end and the right end of the shift register are different between the clock signal and the inverted clock signal, either the left or right shift is performed. There has been a problem that the operation start timing is different or the shift operation is not started. FIG. 8 shows an example of a specific configuration of the gate driver (GD).
(1) A shift register in which each stage (SR) is composed of a first clocked inverter and an inverter connected in series, and a second clocked inverter connected in anti-parallel to the inverter. , And an AND gate which supplies the output of each adjacent stage (SR) of the shift register (1) as a scanning signal to each row of the display unit (3) by taking a logical product.

In the shift register (1), as a shift clock, a clock signal CLK and an inverted clock signal * are alternately provided to the first clocked inverter of each stage (SR).
CLK is supplied, and the inverted clock signal * CKL and the clock signal CLK are supplied to the second clocked inverter of each stage (SR) as an inverted signal of the shift clock, thereby achieving charge stabilization. The shift register (1) is a bidirectional shift register, and the start pulse ST
The data is supplied to the upper or lower stage of the shift register (1). The display section (3) has a delta arrangement in which R, G, and B display pixels are arranged in a triangular shape. In FIG. 8, for convenience of explanation, the number of rows of the display unit (3) is five, and the number of stages of the shift register (1) is six correspondingly. In the figure, scanning is performed from top to bottom, and R, R
This shows a state in which G and B pixel data are given. R, arranged in a triangular shape as surrounded by the dotted line in the figure,
Color display is performed by additive color mixture of G and B colors.

FIG. 9 shows a state when the shift register (1) in FIG. 8 is shifted in the reverse direction, that is, when scanning is performed from the bottom to the top. Since the number of stages of the shift register (1) is even, at the upper end and the lower end where the start pulse ST is supplied,
The shift clocks are different, and the start timing is shifted by one clock, that is, by one row between the top and the bottom and the bottom and the top. Therefore, when the pixel data is written from the fifth row in FIG. 9, for example, the pixel data (R1, G1, B1,...) Of the first row in FIG. Will be written from. However, since the drain line at the left end of the fifth row is common to the drain line of the second column from the left of the second row,
In the fifth row, pixel data (R2, G2, B2,...) From the second column in the second row in FIG. 8 is written. For this reason, in R2, G2, and B3 that display a predetermined color as surrounded by a dotted line in FIG. 8, the display quality is poor because the triangle is distorted in FIG.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and is based on a first clock signal and a second clock signal having opposite polarities supplied to even and odd stages, respectively. In a bidirectional shift register in which a start pulse is supplied to the right end or the left end to start shifting data in a left direction or a right direction, the first clock signal and the second clock signal are respectively supplied to the first and second clock signals. A shift direction switching signal is supplied to one of the inputs of the exclusive OR gate and the second exclusive OR gate, and the other of the inputs of the first and second exclusive OR gates is supplied to the first exclusive OR gate and the second exclusive OR gate. 2 exclusive OR gate outputs the high level / low level of the shift direction switching signal. Rikae by, as an inversion / non-inversion signal of the first clock signal and the second clock signal, a configuration in which each is supplied to the even-numbered stages and the odd-numbered stages.

Thus, by switching the shift direction switching signal between the high level and the low level, the inversion / non-inversion of the polarity of the shift clock is controlled, and the phase of the start pulse can be matched. The direction can be freely switched between left and right. Particularly, the shift direction can be switched to either the left direction or the right direction by switching the right end / left end to which the start pulse is supplied and the high level / low level of the shift direction switching signal. is there.

Thus, the shift direction of the bidirectional shift register can be freely switched to the left / right direction by integrally switching the right / left supply end of the start pulse and the high level / low level of the shift direction switching signal. Can be. In addition, a display portion including one electrode of a pixel capacitor having a liquid crystal as a dielectric layer and a switching element connected thereto is provided on a display portion on one of the opposing surfaces of a pair of electrode substrates opposed to each other with the liquid crystal interposed therebetween. Pixels are arranged in a matrix, and a driving circuit for supplying a signal to the display pixel is arranged at a peripheral portion. The driving circuit includes first clock signals of opposite polarities supplied to even and odd stages, respectively. And the second
A liquid crystal display device comprising a bidirectional shift register in which a start pulse is supplied to the right end or the left end and a start shift is performed in the leftward or rightward direction based on the clock signal of the bidirectional shift register. The first clock signal and the second clock signal are supplied to one of inputs of a first exclusive OR gate and a second exclusive OR gate, respectively, and are applied to the other of the inputs of the first and second exclusive OR gates, respectively. A shift direction switching signal is supplied, and the outputs of the first exclusive OR gate and the second exclusive OR gate switch the first clock signal and the second exclusive OR gate by switching the high / low level of the shift direction switching signal. As an inverted / non-inverted signal of the clock signal, an even number And it is configured to be supplied to the odd-numbered stages.

By switching between the high level and the low level of the shift direction switching signal, the inversion / non-inversion of the polarity of the shift clock is controlled, and the phase of the start pulse can be matched with the phase of the start pulse. The operation direction of the drive circuit can be freely switched between left and right. In particular, the bidirectional shift register switches the shift direction to left / right by switching the right end / left end to which the start pulse is supplied and the high level / low level of the shift direction switching signal. This is a possible configuration.

By this, the right / left supply end of the start pulse and the high level / low level of the shift direction switching signal are integrally switched, so that the operation direction of the drive circuit including the bidirectional shift register is shifted left / right. It can be switched freely. In particular, the switching element, the bidirectional shift register, and the exclusive OR gate are configured by thin film transistors using a polycrystalline semiconductor formed on the same substrate.

Thus, in the liquid crystal display device in which the display pixel portion and the peripheral drive circuit portion are integrally formed on the same substrate,
The polarity of the shift clock supplied from the outside can be converted inside the liquid crystal display device, and the screen can be symmetrically reversed without changing the peripheral integrated circuit elements.

[0017]

FIG. 1 is a block diagram of a bidirectional shift register to which the present invention is applied. (1) is a shift register, which outputs / inputs (ou) of each stage (S / R).
transfer connection (TRR, TR)
By switching in L), it is possible to shift in either right or left direction. In the case of a gate driver, the output (out) of each stage (S / R) of the shift register (1)
In a pair of adjacent two stages, AND operation is performed by an AND gate (2) to extract a shift output (OUT). Each stage (S / R) of the shift register (1) includes a first clocked inverter connected in series, an inverter, and a second clocked inverter connected in antiparallel to the inverter. The clock signal CLK and the inverted clock signal * CLK of the two clocked inverters forming one stage have opposite polarities, and the adjacent stages also have opposite polarities. That is, the clock signal CLK and the inverted clock signal * CLK are supplied to the first clocked inverter, and the inverted clock signal * CLK and the clock signal CLK are supplied to the second clocked inverter for each interval. I have. In the shift register (1) shown here, the transfer gate (TRR)
Is turned on and the transfer gate (TRL) is turned off, thereby setting the shift to the right. At this time, a rightward shift pulse is started by applying a rightward start pulse (STR). On the other hand, in the case of a leftward shift, the transfer gate (TRR) is turned off, the transfer gate (TRL) is turned on, and a leftward start pulse (STL) is applied to start a leftward shift operation.

In the shift register (1) shown in FIG. 1, the output (out) of each adjacent stage becomes Hi at the same time for 1/2 clock period. Therefore, when the number of stages of the shift output (OUT) is odd, the number of stages of the shift register is even. For example, when the left end is controlled by the clock signal CLK, the right end is controlled by the inverted clock signal * CLK. Therefore, when the same clock signal CLK and the inverted clock signal * CLK are supplied, there is a problem that the start timing at the time of left shift and the start timing at the time of right shift are shifted by 1/2 clock period.

The present invention particularly provides a simple bidirectional shift register by appropriately switching the polarity of the shift clock in accordance with the left / right switching. FIG. 2 is an equivalent circuit diagram of the polarity conversion circuit according to the embodiment of the present invention. The clock signal CLK and the inverted clock signal * CLK supplied from the outside are 2
One of the exclusive OR (EXOR) gates (4) is inputted to one input terminal, and the other input terminal is supplied with a DC shift direction switching signal CHN. These E
The output of the XOR gate (4) is a clock signal CLK 'and an inverted clock signal * CLK' whose inversion / non-inversion is controlled by the shift direction switching signal CHN, as shown in FIG.
Is supplied to each stage of the shift register. That is, by switching Hi / Lo of the DC shift direction switching signal CHN, the clock signal CL is changed according to the operation table shown in FIG.
The inversion / non-inversion of K and the inverted clock signal * CLK is switched, and the polarities of the clock signals CLK ′ and * CLK ′ are controlled. Thereby, the shift direction switching signal C
When HN is set to Lo, the clock signal C is not inverted.
LK 'and the inverted clock signal * CLK' have the same polarity as the clock signal CLK and the inverted clock signal * CLK ', respectively. As shown in FIG. 4A, the rightward start pulse STR matches the clock signal CLK. , The shift operation is started. Further, the shift direction switching signal CHN is set to H level.
When i is set, the clock signal CLK 'and the inverted clock signal * CLK' have polarities opposite to those of the clock signal CLK and the inverted clock signal * CLK, and as shown in FIG. Coincides with the inverted clock signal * CLK to start the shift operation.

Therefore, the bidirectional shift register has exactly the same timing regardless of whether the shift operation is started from the leftmost stage controlled by the clock signal CLK or the rightmost stage controlled by the inverted clock signal * CLK. Start with. Therefore, the left end / right end of the supply stage of the start pulse and the shift direction switching signal CH
N Hi / Lo and transfer gate (TRR,
By performing ON / OFF switching of TRL) integrally, the shift direction can be set to either left or right, and a bidirectional shift register having a simple configuration can be obtained. That is, even if the polarity of the clock signal matching the start pulse is different in the left and right shift directions, the polarity of the shift clock is appropriately switched by the polarity conversion circuit of the present invention.
A bidirectional shift register capable of shifting in either the left or right direction is provided.

[0021]

FIG. 5 is a circuit diagram showing a bidirectional shift register according to the present invention.
FIG. 9 is a configuration diagram when a -Si TFT is applied to a drive circuit integrated LCD. The central matrix part is a display part, where a gate line (GL) as a scanning line and a drain line (DL) as a signal line intersect with each other, and a TFT (SE) as a switching element is provided at the intersection. The pixel capacitance (LC) and the auxiliary capacitance (SC) are connected via the power supply.

A gate line (GL) is provided around the display section.
And a drain driver (DD) for driving the drain line (DL). The gate driver (GD) mainly includes a shift register, and the drain driver (DD) mainly includes a shift register and a sampling gate controlled by the shift register. These drivers (GD, D
D) is the same p-Si as the TFT (SE) in the display section.
And a CMOS inverter of a TFT using the same. The vertical and horizontal shift clocks VCLK, * VCL for causing the shift register to perform the shift operation from the external integrated circuit to each driver (GD, DD).
K, HCLK, * HCLK and vertical and horizontal start pulses VST, HST are supplied. The drain driver (DD) is supplied with the LCD original image signal VDSG created in the external integrated circuit, and the sampling gate samples the pixel signal voltage.
The data is sent to each drain line (DL) in accordance with the scanning of the gate driver (GD), and is written to a display pixel including a pixel capacitance (LC) and an auxiliary capacitance (SC).

In the present invention, the gate driver (GD)
Is composed of the bidirectional shift register shown in FIG. 1, and the vertical shift clocks VCLK,
* Characteristic is that VCLK is supplied via the polarity conversion circuit (SW) shown in FIG. This polarity conversion circuit (S
The EXOR gates (3, 4) constituting the W) include a switching TFT (SE) and a driver (GD,
DD) The same p-Si as the CMOS transistor constituting
Are integrally formed on the same substrate by using a CMOSTFT. Further, a shift direction switching signal CHN is supplied to the polarity conversion circuit (SW).

Thus, the shift direction switching signal CH
N is supplied to the supply terminal of the vertical start pulse VST of the bidirectional shift register, which is a gate driver (GD), and O of the transfer gates (TRR, TRL).
By performing the operation integrally with the switching of N / OFF, the vertical scanning direction of the screen can be reversed upside down, and the image can be reversed symmetrically up and down.

FIG. 6 shows a specific configuration of the gate driver (GD). (1) and (2) are the shift register and the AND gate shown in FIG. The output of each stage of the shift register (1) is ANDed and supplied to each row of the display section (3) as a scanning signal voltage. The shift direction of the shift register (1) is from the bottom of the figure to the top, and is scanned in the opposite direction to that of FIG. The display unit (3) has odd rows, for example, five rows for simplification of description, and the number of stages of the shift register (1) is six corresponding to this. In the upper stage and the lower stage of the shift register (1), the shift clock includes a clock signal CLK and an inverted clock signal * CL.
K, but the polarity of the clock signal CLK and the inverted clock signal is also controlled integrally with the switching of the shift direction as described in FIGS. 2, 3, 4, and 5, so Without changing the phase of the pulse ST,
The operation is started at the same timing when shifting upward from the top and when shifting upward from the bottom. Therefore, in FIG.
When the pixel data is written from the row, 5 in FIG.
Writing is performed from the line, and upside down display is performed while maintaining symmetry. For example, R2, G2, and B3 that display a predetermined color as indicated by a dotted line are shown in FIGS. 6 and 7 only in which the arrangement of the triangles is reversed up and down. There is no such thing as distortion. This means that
This is because the number of rows in the display unit (3) is odd, and the polarities of the clock signal CLK and the inverted clock signal * CLK of the corresponding even-numbered stage shift register (1) are integrally controlled with the switching of the shift direction. .

These shift direction switching signals Hi / L
o, ON / OFF of the transfer gate is fixed by cutting and welding predetermined wiring by laser irradiation after completion of LCD, or by external operation by integrated development of software and logic circuit element There is a method of fixing at the time of initial setting. Therefore, even in a case where three LCDs are installed in different directions in an application such as a three-panel projector, the inconsistency of images can be eliminated by switching the scanning directions.
The degree of freedom in the arrangement of CDs can be increased.

[0027]

According to the present invention, a bidirectional shift register having a simple structure is obtained. Thus, in the liquid crystal display device in which the peripheral driving circuit is integrally formed on the same substrate together with the display pixel portion, the bidirectional switching mechanism can be integrally formed, and there is no need to change the peripheral driving circuit element. Therefore, the manufacturing cost is low, and the screen can be set upside down or left and right symmetrically in accordance with the application, and the versatility is extremely high.

[Brief description of the drawings]

FIG. 1 is a block diagram of a bidirectional shift register according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the polarity conversion circuit according to the embodiment of the present invention.

FIG. 3 is an operation table of the polarity conversion circuit according to the embodiment of the present invention.

FIG. 4 is a timing chart of the bidirectional shift register according to the embodiment of the present invention;

FIG. 5 is a configuration diagram of an LCD according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of a gate driver according to an embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional LCD.

FIG. 8 is a configuration diagram of a gate driver.

FIG. 9 is a configuration diagram of a gate driver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shift register 2 AND gate 3 Display part 4 EXOR gate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 5/66 102 H04N 5/66 102B

Claims (5)

[Claims] 1. A start pulse is supplied to a right end or a left end based on a first clock signal and a second clock signal having opposite polarities supplied to an even-numbered stage and an odd-numbered stage, respectively. A first or second clock signal is supplied to one of inputs of a first exclusive OR gate and a second exclusive OR gate, respectively. The first
And a shift direction switching signal is supplied to the other of the inputs of the second exclusive OR gate, and the output of the first exclusive OR gate and the output of the second exclusive OR gate are switched between high level / low level of the shift direction switching signal. Wherein the first clock signal and the second clock signal are supplied to an even-numbered stage and an odd-numbered stage, respectively, as inverted / non-inverted signals of the second clock signal. 2. The right end to which the start pulse is supplied.
2. The bidirectional shift according to claim 1, wherein the shift direction can be switched to either a left direction or a right direction by switching a left end and a high level / low level of the shift direction switching signal. register. 3. A display section on one of the opposing surfaces of a pair of electrode substrates opposed to each other with a liquid crystal interposed therebetween, and one electrode of a pixel capacitor using a liquid crystal as a dielectric layer and a switching element connected thereto. Display pixels are arranged in a matrix,
A driving circuit for supplying a signal voltage to the display pixel is disposed at a peripheral portion, and the driving circuit includes a first clock signal and a second clock signal having opposite polarities respectively supplied to even-numbered stages and odd-numbered stages.
A liquid crystal display device comprising a bidirectional shift register in which a start pulse is supplied to a right end or a left end and a start shift is performed in a leftward or rightward direction based on a clock signal of the bidirectional shift register. The first clock signal and the second clock signal are supplied to one of inputs of a first exclusive OR gate and a second exclusive OR gate, respectively, and are applied to the other of the inputs of the first and second exclusive OR gates, respectively. A shift direction switching signal is supplied, and the outputs of the first exclusive OR gate and the second exclusive OR gate switch the first clock signal and the second exclusive OR gate by switching the high / low level of the shift direction switching signal. As an inverted / non-inverted signal of the clock signal, an even number A liquid crystal display device characterized in that the liquid crystal display device is supplied to stages and odd stages. 4. The bidirectional shift register switches a shift direction between a left direction and a right direction by switching a right end / left end to which the start pulse is supplied and a high level / low level of the shift direction switching signal. 4. The method according to claim 3, wherein the switching is also possible.
The liquid crystal display device as described in the above. 5. The switching element, the bidirectional shift register, and the exclusive OR gate are formed of a thin film transistor using a polycrystalline semiconductor formed on the same substrate. Liquid crystal display device.