JP4061701B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device. Specifically, the switching means for the horizontal driving circuit formed on the insulating substrate for the liquid crystal display device is constituted by a pair of switching elements connected in series, and the switching means is reduced by reducing the number of gate lines driven in time division. The area occupied by can be reduced.
[0002]
[Prior art]
A liquid crystal display device (LCD) having features such as thinness, light weight, and low power consumption is often used as a display device for OA equipment such as a personal computer and home appliance AV equipment such as a video camera. An active matrix type liquid crystal display device using a thin film transistor (TFT) that is superior in terms of the spot is attracting attention.
[0003]
The active matrix method is one of the driving methods of a dot matrix type liquid crystal display device suitable for handling a large amount of information, and there is a simple matrix method as another driving method. The active matrix method has a more complex panel structure and a higher manufacturing cost than the simple matrix method with a simple structure and low manufacturing cost, but has an excellent response speed and visual recognition characteristics and is excellent in terms of image quality.
[0004]
FIG. 5 is a configuration diagram of a drive circuit of an active matrix liquid crystal display device. As shown in FIG. 5, the active matrix type liquid crystal display device has source lines (signal lines) X ₁ , X ₂ ,. . . , _Xm and Y direction (horizontal direction in the drawing), and gate lines Y ₁ , Y ₂ ,. . . , Y _n . A horizontal drive circuit driver IC1 is connected to the source line, and a vertical drive circuit 10 is connected to the gate line.
[0005]
The driver IC 1 includes a decoder and an output circuit (not shown), and applies a predetermined analog voltage corresponding to the image data from the output circuit to the source line. Pixels are arranged at intersections between the source lines and the gate lines, and a TFT 30 as a pixel driving element (switching element), a liquid crystal capacitor 32, and an additional capacitor 31 are connected to each pixel.
[0006]
The operation principle of the active matrix type liquid crystal display device is that gate lines Y ₁ , Y ₂ ,. . . , Y _n are scanned sequentially from the top in a line sequential manner, and the TFTs 30 of all the pixels on one gate line are turned on (conducting state) all at once. In synchronization with this scanning, the source lines X ₁ , X ₂ ,. . . Supplies a signal charge through X _m, respectively to all of the capacitance 32 attached to TFT30 in the ON state by applying a predetermined analog voltage. As a result, the light transmittance of each liquid crystal changes according to the analog voltage value. Here, since each additional capacitor 31 is charged, even after the TFT 30 is turned off (insulated), the light transmission state of the liquid crystal is maintained until the TFT 30 is turned on next time.
[0007]
However, such an active matrix type liquid crystal display device has a problem that the number of drivers (driver ICs) increases because one driver is required for each source line. Further, in the case of color display with gradation, there are problems that the scale of the driver IC is increased by the setting of the intermediate level voltage and the manufacturing cost is increased.
[0008]
In order to solve this problem, a liquid crystal display panel driving method (Japanese Patent Laid-Open No. 4-52684) in which a second switching means including a single switching element is provided on the input side of each source line of the liquid crystal display panel is disclosed in the prior art. Are known.
[0009]
FIG. 6 is a partial circuit diagram of a driving circuit of an active matrix liquid crystal display device according to the prior art. The drive circuit shown in FIG. 6 has substantially the same configuration as that of the drive circuit shown in FIG. 5, and the same portions are denoted by the same reference numerals and redundant description thereof is omitted.
[0010]
The driver IC 1 includes, for example, R, G, and B data line bundles 20R to 20B each including three data lines. That is, in this case, since each of the data line bundles 20R to 20B transmits 3-bit digital image data (source data), 512-color display with 8 gradations is possible.
[0011]
Each data line has a memory means 18 constituted by connecting one shift register 13, level shifter 14, and latch 15. The shift register 13 stores and sends 1-bit image data, the level shifter 14 adjusts the logical value level of the 1-bit image data, and the latch 15 holds the 1-bit image data for a predetermined time.
[0012]
On the output side of each latch 15, first switching means 22 and 23 having an N-channel TFT structure are provided. The first switching means 22 and 23 are connected to a decoder built in the output circuit, and are connected to a digital-analog conversion circuit. Is converted to an analog voltage. In the output circuit 12, one output terminal 12a, 12b,... Is provided for the four data line bundles 20R-20B. For example, an N-channel TFT as the second switching means 24a-24d is provided on the output terminal 12a. To the four source lines X _{1 to} X ₄ . Similarly commonly connecting output terminal 12b to the source line X ₅ to X _8.
[0013]
Here, for example, the first switching means 22 and 23 are sequentially turned on by the time division switch selection signals SA1 to SA4. As a result, the output circuit 12 sequentially outputs image signals of a predetermined voltage corresponding to the input image data from the output terminals 12a, 12b,. In the liquid crystal display panel 2, the second switching means 24a to 24d (25a to 25d) are sequentially turned on in synchronization with the first switching means 22 and 23 by the time division switch selection signals S1 to S4, so that the second Output signals (input image signals) from the respective switching means are supplied to predetermined source lines X _{1 to} X ₈ , respectively.
[0014]
[Problems to be solved by the invention]
As described above, according to the prior art, the first switching means 22 and 23 are provided for each data line of the driver IC 1 and the second switching is made of a single switching element on the input side of each source line of the liquid crystal display panel 2. Means 24a to 24d, 25a to 25d are newly provided, and the output terminals 12a, 12b,... Of the driver IC 1 are connected to the data lines and the plurality of source lines X _{1 to} X ₄ or X ₅ to connect to X _8, the first of each of the second switching means of the liquid crystal display panel 2 to the switching means 22, 23 24 a to 24 d of the driver IC1, by sequentially turned on and off to synchronize 25 a to 25 d, from the data line , And the source line X corresponding to the data line from the output terminals 12a, 12b,. It is to be supplied to ₁ to X _8. Therefore, according to the prior art, the driver IC connected to all the source lines of the liquid crystal display device can be made compact or the number thereof can be reduced.
[0015]
However, according to the prior art, the number of time-division gate lines increases as the number of time divisions increases. That is, the same number of gate lines as the number of source lines to be time-divided is required. As a result, the area occupied by the switching means increases. That is, as shown in FIG. 7, the liquid crystal display panel 2 is composed of an effective display area 17 and its peripheral area, the horizontal upper part 16 is a formation area for a time-division switch, and the left end is the formation of the vertical drive circuit 10. It is made an area.
[0016]
If the area of the portion other than the liquid crystal display region 17, particularly the vertical frame portion (time-division switch region) increases, there is a problem that the liquid crystal display panel 2 itself becomes large. Therefore, according to the prior art, since the liquid crystal display panel 2 becomes large, the portability of the liquid crystal display device is hindered, and the number of panels obtained from one transparent insulating substrate is reduced, thereby reducing the manufacturing yield.
[0017]
Accordingly, an object of the present invention is to provide a liquid crystal display device using TFTs that can reduce the size of the panel of the liquid crystal display device by reducing the number of time-division gate lines.
[0018]
[Means for Solving the Problems]
For the present invention to solve the above problems, according to the invention described in claim 1, when an image signal into a plurality of source lines constituting the display unit through the analog primary color signal gas switching means divided is supplied to, the upper kiss switching means p number of switching elements at least in series connection are provided corresponding to the analog primary color signal, the gate lines of p present for switching the p number of the switching elements, respectively The m-th (1 ≦ m ≦ p) switching elements among the p switching elements provided on the source line are switched by the m-th gate signal, and 2 ^{p elements} in units of 2 ^{p elements.} the source line is time-division-driven in, this to the switching element of the switching means comprises a n-channel and p-channel transistor It is solved by a liquid crystal display device according to claim.
[0019]
The present invention pays attention to a combination of different switching elements, and a second switching means comprising a plurality of switching elements is provided for each source line of the liquid crystal display panel.
[0020]
According to the present invention, the number of time-division gate lines can be reduced by providing the second switching means including a plurality of switching elements for each source line and combining the on / off states. The driver IC can be made compact or the number thereof can be reduced without increasing the area occupied by the dividing gate line.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a partial circuit diagram of a drive circuit of an active matrix liquid crystal display device according to the first embodiment of the present invention. The drive circuit of the active matrix type liquid crystal display device according to the present invention shown in FIG. 1 has substantially the same configuration as the drive circuit of the active matrix type liquid crystal display device shown in FIGS. 5 and 6, and the same parts are designated by the same reference numerals. The duplicate explanation is omitted.
[0023]
The configuration of the liquid crystal display panel 3 according to the present invention is different from the liquid crystal display panel 2 according to the prior art in that a plurality of source lines for each source line of the liquid crystal display panel 3 can be driven in a time-sharing manner. Second switching means 28, 29,... (28a to 28d, 29a to 29d,...) Composed of switching elements are provided.
[0024]
In the example shown in the figure, four source lines are connected to one output terminal provided in the output circuit 12, and these four source lines are driven in a time-sharing manner. To illustrate the second switching means 28, the second switching means 28 includes first and second switching elements connected in series to the source line. Further, the first switching elements are commonly controlled by the first gate signal SG1, and the four second switching elements are also commonly controlled by the second gate signal SG2.
[0025]
Here, the first and second switching elements are selected to have a conductive type as shown in the drawing so that the conduction states of the respective switching means 28a to 28d are time-divisional based on these two gate signals SG1 and SG2. Has been.
[0026]
To exemplify a MOS transistor as a switching element, a switching element connected to a source line X ₁ MOS transistors 35, 35 of the N-channel type is a first conductivity type are used. Similarly, a P-channel MOS transistor 36 of the second conductivity type is used as the first switching element in the source line X ₂ , and an N-channel MOS transistor 35 is used as the second switching element. . An N channel type MOS transistor 35 is used as the first switching element connected to the source line X ₃ , and a P channel type MOS transistor 36 is used as the second switching element. P channel MOS transistors 36 and 36 are used for both the first and second switching elements in the source line X ₄ .
[0027]
Assuming that an analog image signal as shown in FIG. 2A is obtained at the output terminal 12a, a rectangular wave signal as shown in FIGS. B and C is supplied as the gate signals SG1 and SG2, so that an interval t1 Then, only the source line X ₁ is turned on and the corresponding image signal R is applied to the source line X ₁ . As a result, R pixels are projected. The following Similarly source line X ₂ in the interval t2 is turned on, the source line X ₃ in the interval t3 is turned on, and the source line X ₄ in the section t4 is turned on. As a result, the corresponding pixels are displayed by the corresponding image signals R, G, and B.
[0028]
Here, the number p of time-division gate lines provided in the second switching means 28, 29,... And the number q per output terminal of the source lines controlled by the gate lines are 2 ^p = q. Since there is a relationship, this embodiment is a case where p = 2 and q = 4. That is, when the four source lines X _{1 to} X ₄ , X _{5 to} X ₈ ,... Are time-divided, two gate lines are sufficient. Accordingly, when eight source lines are time-divided, three gate lines are sufficient.
[0029]
Since the number of time-division gate lines provided in the second switching means can be halved compared to the prior art, the width B of the time-division switching region 16 is made narrower than the conventional width A as shown in FIG. The size of the liquid crystal display panel can be reduced by this narrowing.
[0030]
Further, as described above, in the present invention, the number p of the time-division gate lines of the second switching means and the number q of the source lines controlled by the gate line per one output terminal are 2 ^p = q Therefore, as the number of source lines q connected to one output terminal is increased to increase the number of time divisions, the width of the region 16 for forming the number of time division gate lines of the present invention relative to the prior art becomes 1 / 2, 3/8, 1/4, 5/32. . . Therefore, the reduction effect becomes more remarkable.
[0031]
As a result of the reduction in the number of time division gate signals, the vertical width B of the time division switch region according to the present invention is smaller than the vertical width A of the time division switch region according to the prior art as shown in FIG. Is done. That is, according to the present invention, the vertical width D of the entire liquid crystal display panel can be made smaller than the vertical width C of the conventional whole panel.
[0032]
On the other hand, if the panel width (D = C) is the same as that of the prior art, the area of the effective display area 17 can be increased, so that the display section can be widened.
[0033]
FIG. 4 is a partial circuit diagram of an application example of the drive circuit of the active matrix liquid crystal display device according to the second embodiment of the present invention. The configuration of the second embodiment is substantially the same as the configuration of the first embodiment, and the same portions are denoted by the same reference numerals, and redundant description thereof is omitted.
[0034]
The difference of the configuration of the second embodiment from the first embodiment is the second switching means 28, 29,... Of the first embodiment, in which the source lines X ₁ , X ₂ ,. A P-channel TFT is connected to the N-channel TFT connected to ・, and an N-channel TFT is connected to the P-channel TFT in parallel with respect to the source and drain, respectively, so as to be complementary. Further, an inverter 33 is connected between the gates of the N-channel TFT and the P-channel TFT.
[0035]
In FIG. 4, for example, the time division gate signal SG1 or SG2 (FIG. 2) is inputted as it is to the gate of the TFT 38 on the left side of the paired TFT. Further, a time division gate signal SG1 or SG2 inverted by an inverter is input to the gate of the TFT 39 on the right side. Since the paired TFTs are an N-channel TFT and a P-channel TFT, the N-channel TFT and the P-channel TFT are simultaneously turned on / off. At this time, for example, since the P-channel TFT is completely turned on even if the N-channel TFT is not completely turned on, the switching operation by the AC drive signal supplied to the common electrode is the same as the switching operation of the first embodiment. become. The same applies to the other switching means 28b to 28d, 29,.
[0036]
Therefore, according to this embodiment, the number of time-division gate lines can be reduced, and the liquid crystal display device can be reduced in size.
[0037]
【The invention's effect】
As described above, according to the present invention, the area of the frame portion in the vertical direction of the liquid crystal display device is reduced by providing the second switching means including a plurality of switching elements on each source line of the liquid crystal display panel. Therefore, the driver IC can be made compact or the number thereof can be reduced without increasing the area of the liquid crystal display panel (area occupied by the time-division gate lines).
[0038]
As described above, according to the present invention, the area of the liquid crystal display panel can be reduced as compared with the prior art, so that the portability of the liquid crystal display device can be ensured. In addition, according to the present invention, the number of liquid crystal display panels obtained from a single transparent insulating substrate increases, so that the manufacturing yield can be improved.
[Brief description of the drawings]
FIG. 1 is a partial circuit diagram of a drive circuit of an active matrix liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is an operation explanatory diagram of the embodiment according to the present invention.
FIG. 3 is an explanatory view of narrowing a frame portion according to the present invention.
FIG. 4 is a partial circuit diagram of a drive circuit of an active matrix liquid crystal display device according to a second embodiment of the present invention.
FIG. 5 is a configuration diagram of a drive circuit of an active matrix type liquid crystal display device.
FIG. 6 is a partial circuit diagram of a driving circuit of an active matrix type liquid crystal display device according to the prior art.
FIG. 7 is an explanatory view showing a liquid crystal display panel according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Driver IC, 2, 3 ... Liquid crystal display panel, 12 ... Output circuit, 16 ... Time division switch area, 17 ... Effective display area, 18 ... Memory means, 22 , 23 ... first switching means, 24a to 24d, 25a to 25d, 28a to 28d, 29a to 29d ... second switching means, 26, 27 ... output terminals, 30 ... TFT, 31 ... Additional capacity, 32 ... Liquid crystal capacity, 33 ... Inverter

Claims (2)

Together are divisionally supplied when an image signal into a plurality of source lines constituting the display unit through the analog primary color signal gas switching means,
Upper kiss switching means p number of switching elements at least in series connection are provided corresponding to the analog primary color signals,
P gate lines are arranged to switch the p switching elements, respectively.
Among the p switching elements provided on the source line, the m-th (1 ≦ m ≦ p) switching elements are switched by the m-th gate signal,
2 ^{p of the} source lines are time-division driven in units of 2 ^p ,
A liquid crystal display device, wherein the switching element of the switching means comprises n-channel and p-channel transistors .   The liquid crystal display device according to claim 1, wherein the display unit is provided in a liquid crystal display panel.

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