JP4449366B2 - Electro-optical device and electronic apparatus - Google Patents

Description

  The present invention relates to an electro-optical device and an electronic apparatus.

  A display device, for example, a liquid crystal display device using a liquid crystal as an electro-optical material, is widely used as a display device in place of a cathode ray tube (CRT) in a display unit of various information processing devices, a liquid crystal television, and the like.

  A liquid crystal display device includes a pixel electrode arranged in a matrix, an element substrate provided with a switching element such as a TFT (Thin Film Transistor) connected to the pixel electrode, and a counter electrode facing the pixel electrode. And a liquid crystal which is an electro-optic material filled between the two substrates. A pixel is composed of a switching element, a pixel electrode, an electro-optic material, and a counter electrode, and is arranged in a matrix.

  In such a liquid crystal display device, it is necessary to supply an image signal corresponding to the display gradation to each data line. In general, since display gradation is often given as image data, liquid crystal display devices including a DA converter as a data line driving circuit are known (for example, Patent Document 1 and Patent Document 2).

JP 2003-84727 A JP-A-9-138670

  By the way, a liquid crystal display device may be provided with a plurality of data line driving circuits, and a predetermined number of data lines may be assigned to each data line driving circuit for driving. In such a case, DA conversion characteristics cannot be completely matched in a plurality of data line driving circuits, and there are many variations. The variation in the DA conversion characteristic appears as luminance unevenness, and there is a problem that the display image quality deteriorates.

  Accordingly, it is an object of the present invention to provide an electro-optical device with improved display image quality in an electro-optical device including a plurality of data line driving circuits.

  In order to solve the above-described problem, an electro-optical device according to the present invention includes a plurality of data lines, a plurality of scanning lines, and a pixel region in which a plurality of pixels corresponding to intersections of the data lines and the scanning lines are formed. And a plurality of data line driving circuits respectively provided corresponding to a predetermined number of data lines, wherein the data line driving circuits are connected in series between a high potential power source and a low potential power source. A ladder resistor, a DA converter that obtains each gradation voltage from each connection point of the ladder resistor, converts image data from a digital signal to an analog signal, and outputs the image signal to the data line, and each of the ladder resistor And a plurality of wirings for connecting some of the connection points to each other.

  According to the present invention, since some of the connection points of the ladder resistors provided in the plurality of data line driving circuits are connected to each other, the potentials of the connected connection points are the same. Therefore, even if the value of the ladder resistance varies in each data line driving circuit, the DA conversion characteristics can be made uniform. As a result, display unevenness of the electro-optical device can be greatly improved.

  In the electro-optical device described above, it is preferable that the plurality of wirings are provided at equal intervals with respect to the plurality of ladder resistors. In this case, since the gradation voltages match for each predetermined gradation, display unevenness can be improved over all gradations.

  In the electro-optical device described above, the plurality of wirings may be arranged such that a distance between the plurality of ladder resistors becomes closer as the distance from the center gray scale increases. The human vision becomes more sensitive as the gray level is farther than the intermediate gray level. Therefore, the user detects a slight difference in brightness as display unevenness in a dark gradation or a light gradation. According to the present invention, since the plurality of wirings are provided so that the distance between the plurality of ladder resistors increases as the distance from the center gradation increases, the gradations are aligned in a region having high sensitivity in visual characteristics. Therefore, display unevenness can be further reduced.

  Further, the electro-optical device described above includes an electro-optical panel in which the pixel region is formed, and a flexible substrate connected to the electro-optical panel and an external substrate, and the plurality of data line driving circuits include the flexible circuit It is preferable that the plurality of wirings are provided on the substrate and formed on the electro-optical panel or the external substrate. In this case, the data line driving circuit can be formed on the flexible substrate.

  The electro-optical device includes the electro-optical device in which the pixel region is formed, and a flexible substrate connected to the electro-optical panel and an external substrate, and the plurality of data lines. The drive circuit may be provided on the electro-optical panel, and the plurality of wirings may be formed on the electro-optical panel, the flexible substrate, or the external substrate. In this case, the data line driving circuit can be formed on the electro-optical panel.

  In addition, the above-described electro-optical device includes an electro-optical panel in which the pixel region is formed, and a flexible substrate connected to the electro-optical panel and an external substrate, and the plurality of data line driving circuits include the external The plurality of wirings provided on the substrate may be formed on the electro-optical panel, the flexible substrate, or the external substrate. In this case, the data line driving circuit can be formed on the external substrate.

  In the electro-optical device described above, it is preferable that each of the plurality of data line driving circuits is configured as an IC chip, and each of the IC chips is fixed via an anisotropic conductive film.

  Next, an electronic apparatus according to the present invention includes the above-described electro-optical device, and includes, for example, a liquid crystal projector, a personal computer, a mobile phone, an electronic camera, and a PDA.

Embodiments according to the present invention will be described below with reference to the drawings. In the present embodiment, a liquid crystal panel using liquid crystal as an electro-optical material will be described as an example of an electro-optical panel, and a liquid crystal display device using the liquid crystal panel will be described as an example of an electro-optical device.
<1. Overall configuration of liquid crystal display device>
FIG. 1 shows the overall configuration of the liquid crystal display device. As shown in this figure, the liquid crystal display device includes a liquid crystal panel AA, flexible substrates B1 to B5, and an external substrate C. In the liquid crystal panel AA, an image display area A in which an image is displayed is formed, and a scanning line driving circuit 100 that drives scanning lines is formed.

  FIG. 2 shows an electrical configuration of the liquid crystal panel AA. In the image display area A, as shown in FIG. 2, m (m is a natural number of 2 or more) scanning lines 2 are formed in parallel along the X direction, while n (n is (Natural number of 2 or more) number of data lines 3 are arranged in parallel along the Y direction. In the vicinity of the intersection of the scanning line 2 and the data line 3, the gate of the TFT 50 is connected to the scanning line 2, while the source of the TFT 50 is connected to the data line 3 and the drain of the TFT 50 is connected to the pixel electrode 6. Connected. Each pixel includes a pixel electrode 6, a counter electrode (described later) formed on the counter substrate, and a liquid crystal sandwiched between the two electrodes. As a result, the pixels are arranged in a matrix corresponding to each intersection of the scanning line 2 and the data line 3.

  Further, scanning signals Y1, Y2,..., Ym are applied to each scanning line 2 to which the gate of the TFT 50 is connected in a pulse-by-line manner. Therefore, when a scanning signal is supplied to a certain scanning line 2, the TFT 50 connected to the scanning line is turned on, so that the data line signals X1, X2,..., Xn supplied from the data line 3 at a predetermined timing. Are sequentially written in the corresponding pixels and then held for a predetermined period.

  Since the orientation and order of liquid crystal molecules change according to the potential level applied to each pixel, gradation display by light modulation becomes possible. For example, in the normally white mode, the amount of light passing through the liquid crystal is limited as the applied potential is increased. In the normally black mode, the amount of light is reduced as the applied potential is increased. As a whole, light having contrast according to the image signal is emitted for each pixel. For this reason, a predetermined display becomes possible.

  Returning to FIG. Data line drive circuits 201 to 204 are provided on the respective flexible substrates B1 to B4. These drive circuits are configured as drive IC chips mounted on a film using TAB (Tape Automated Bonding) technology, and are electrically and mechanically attached to each flexible substrate B1 to B4 via an anisotropic conductive film. It is fixed. The flexible substrates B1 to B5 are configured by patterning wiring on a base material such as polyimide, but a part or all of the flexible substrates B1 to B5 may be configured by patterning wiring on a base material such as polychlorinated biphenyl (PCB). .

  The data line driving circuits 201 to 204 are provided corresponding to a predetermined number of data lines 3, and DA-convert image data to generate data line signals. In this example, the data line driving circuit 201 is on the data line 3 in the area A1, the data line driving circuit 202 is on the data line 3 in the area A2, and the data line driving circuit 203 is on the data line 3 in the area A3. Reference numerals 204 correspond to the data lines 3 in the area A4.

  The flexible substrate B5 functions as a relay substrate between the flexible substrates B1 to B4 and the external substrate C, and wirings L1 to L3 are formed therein. The wirings L1 to L3 will be described later. The external substrate C is provided with a timing generation circuit 300, an image processing circuit 400, a power supply circuit 500, and the like.

  The input image data D supplied to the liquid crystal display device is, for example, in an 8-bit parallel format. The timing generation circuit 300 generates control signals such as a Y clock signal YCK, an inverted Y clock signal YCKB, and a Y transfer start pulse DY in synchronization with the input image data D. The timing generation circuit 300 generates various timing signals for controlling the image processing circuit 400 and outputs them.

  The Y clock signal YCK specifies a period for selecting the scanning line 2, and the inverted Y clock signal YCKB is obtained by inverting the logic level of the Y clock signal YCK. The X clock signal XCK specifies a period for selecting the data line 3, and the inverted X clock signal XCKB is obtained by inverting the logic level of the X clock signal XCK.

  The image processing circuit 400 performs gamma correction and the like on the input image data D considering the light transmission characteristics of the liquid crystal panel AA, generates line sequential image data, and outputs the data to the data line driving circuits 201 to 204. . The power supply circuit 500 supplies potential power to the timing generation circuit 300 and the image processing circuit 400 and generates power supply voltages for the scanning line driving circuit 100 and the data line driving circuits 201 to 204.

  Next, details of the data line driving circuits 202 to 204 will be described. The data line driving circuits 202 to 204 include a DA converter that converts image data from a digital signal to an analog signal and a reference voltage generation circuit. A plurality of DA converters are provided in each of the data line driving circuits 202 to 204, and one DA converter corresponds to one data line. On the other hand, one reference voltage generating circuit is provided for each data line driving circuit 201-204. The reference voltage generating circuit includes a plurality of ladder resistors connected in series between a high potential power source and a low potential power source.

  FIG. 3 shows an equivalent circuit of the reference voltage generation circuits 201a to 204a used in the data line driving circuits 201 to 204. In this example, the high potential power supply VDD and the low potential power supply VSS are supplied to the reference voltage generation circuits 201a to 204a. The high potential power supply VDD corresponds to the gradation “0”, and the low potential power supply VSS corresponds to the gradation “255”. The symbol R shown in the figure corresponds to the ladder resistance for 32 gradations.

  In this example, some of the connection points of the ladder resistors are connected to each other by wirings L1 to L3. For example, the potential of the connection points Q1 to Q4 is V32 corresponding to the gradation “32”, but the value of the ladder resistance varies among the reference voltage generation circuits 201a to 204a. Does not match. The display unevenness generated in the conventional liquid crystal display device is caused by such a difference in the reference potential. In the present embodiment, since some of the connection points of the ladder resistor are connected to each other by the wirings L1 to L3, the potentials of the connection points can be made uniform and display unevenness can be eliminated. . Further, the wirings L1 to L3 are provided at equal intervals with respect to the plurality of ladder resistors (in this example, every 32 gradations). Therefore, it is possible to make the brightness uniform over all gradations with a limited number of wires.

<2. Configuration of LCD panel>
Next, the overall configuration of the liquid crystal panel AA will be described with reference to FIGS. Here, FIG. 4 is a perspective view showing a configuration of the liquid crystal panel AA, and FIG. 5 is a sectional view taken along the line ZZ ′ in FIG.

  As shown in these drawings, the liquid crystal panel AA includes an element substrate 151 such as glass or semiconductor on which the pixel electrode 6 or the like is formed, and a transparent counter substrate 152 such as glass on which the common electrode 158 or the like is formed. In addition, the sealing material 154 mixed with the spacer 153 is bonded so that the electrode forming surfaces face each other while maintaining a certain gap, and a liquid crystal 155 as an electro-optical material is sealed in the gap. Note that the sealant 154 is formed along the periphery of the counter substrate 152, but a part thereof is opened to enclose the liquid crystal 155. Therefore, after the liquid crystal 155 is sealed, the opening is sealed with the sealing material 156.

  Here, on the opposite surface of the element substrate 151 and on the outer side of the sealing material 154, the scanning line driving circuit 100 is formed to drive the data lines 3 extending in the X direction. In addition, a plurality of input terminals 157 are formed on one side adjacent to the one side, and a driving signal is supplied to the scanning line driving circuit 100 and an image signal is supplied to the data line 3 as a data line signal. It has become.

  The common electrode 158 of the counter substrate 152 is electrically connected to the element substrate 151 by a conductive material provided in at least one of the four corners of the bonding portion with the element substrate 151. In addition, the counter substrate 152 is provided with, for example, a color filter arranged in a stripe shape, a mosaic shape, a triangle shape, or the like according to the use of the liquid crystal panel AA. And a black matrix such as resin black in which carbon or titanium is dispersed in a photoresist, and third, a backlight for irradiating the liquid crystal panel AA with light. Particularly in the case of color light modulation, a black matrix is provided on the counter substrate 152 without forming a color filter.

  In addition, the opposing surfaces of the element substrate 151 and the counter substrate 152 are each provided with an alignment film or the like that is rubbed in a predetermined direction, and a polarizing plate (not shown) corresponding to the alignment direction on each back side. Are provided respectively. However, if a polymer-dispersed liquid crystal dispersed as fine particles in a polymer is used as the liquid crystal 155, the above-described alignment film, polarizing plate, and the like are not required. This is advantageous in terms of reducing power consumption.

<3. Application example>
<3-1: Configuration Example of Wirings L1 to L3>
In the embodiment described above, the wirings L1 to L3 are provided at equal intervals with respect to the plurality of ladder resistors, but the present invention is not limited to this. FIG. 6 shows another configuration example of the wirings L1 to L3. In this example, the wirings L <b> 1 to L <b> 3 are provided so that the intervals become closer to the plurality of ladder resistors as the distance from the central gradation increases. The wirings L1 to L3 make the potential between them uniform by connecting the connection points of the ladder resistors to each other. However, since there is a limit to the number of wirings, it is important to determine what gradation potential is uniform. Human vision has a characteristic that sensitivity is high in a bright region and a dark region, and a slight gradation difference can be distinguished. Therefore, in the application example, by providing the wirings L1 to L3 so that the intervals become closer to the plurality of ladder resistors as the distance from the center gradation becomes smaller, the gradation difference is reduced in the bright and dark areas. is doing.

<3-2: Data Line Driver Circuit and Wiring Arrangement Example>
In the above-described embodiment, the data line driving circuits 201 to 204 are arranged on the flexible boards B1 to B4, and the wirings L1 to L3 are arranged on the flexible board B5. It may be formed.

  Further, the data line driving circuit may be arranged in the liquid crystal panel AA. FIG. 7 shows a configuration example in which the data line driving circuit is arranged in the liquid crystal panel AA. In this example, three data line driving circuits 201 to 203 are provided in the liquid crystal panel AA. In this case, each driving IC chip may be electrically and mechanically connected to a predetermined position of the element substrate 151 via an anisotropic conductive film using COG (Chip On Grass) technology. In this example, the wirings L1 and L2 are formed on the liquid crystal panel AA, but they may be arranged on a flexible substrate or an external substrate C.

  Further, the data line driving circuits 201 to 204 may be arranged on the external substrate C, and the wirings L1 to L3 may be arranged on any of the liquid crystal panel AA, the flexible substrate, or the external substrate C.

<3-3: Other example of electro-optical device>
Further, in the above-described embodiment, the switching element of the pixel has been described as a three-terminal element typified by a TFT, but may be configured by a two-terminal element such as a diode. However, when a two-terminal element is used as a pixel switching element, the scanning line 2 is formed on one substrate, the data line 3 is formed on the other substrate, and the two-terminal element is connected to the scanning line 2 or the data line. 3 must be formed between the pixel electrode and the pixel electrode. In this case, the pixel is composed of a two-terminal element connected in series between the scanning line 2 and the data line 3 and a liquid crystal.

Although the present invention has been described as an active matrix liquid crystal display device, the present invention is not limited to this, and can also be applied to a passive type using STN (Super Twisted Nematic) liquid crystal. Furthermore, as an electro-optical material, in addition to liquid crystal, an electroluminescence element or the like can be used for a display device that performs display by the electro-optical effect. The electro-optical device also includes an electrophoretic device such as electronic paper, and a device using an electron-emitting device (Field Emission Display and Surface-Conduction Electron-Emitter Display).
That is, the present invention can be applied to all electro-optical devices having a configuration similar to that of the liquid crystal device described above.

<3-4: Electronic equipment>
Next, the case where the above-described liquid crystal display device is applied to various electronic devices will be described.
<3-4-1: Projector>
First, a projector using this liquid crystal device as a light valve will be described. FIG. 8 is a plan view showing a configuration example of the projector.

  As shown in this figure, a lamp unit 1102 including a white light source such as a halogen lamp is provided inside the projector 1100. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and serves as a light valve corresponding to each primary color. The light enters the liquid crystal panels 1110R, 1110B, and 1110G.

  The configuration of the liquid crystal panels 1110R, 1110B, and 1110G is the same as that of the liquid crystal panel AA described above, and is driven by R, G, and B primary color signals supplied from an image signal processing circuit (not shown). The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In this dichroic prism 1112, R and B light is refracted at 90 degrees, while G light travels straight. Accordingly, as a result of the synthesis of the images of the respective colors, a color image is projected onto the screen or the like via the projection lens 1114.

Here, paying attention to the display images by the liquid crystal panels 1110R, 1110B, and 1110G, the display image by the liquid crystal panel 1110G needs to be horizontally reversed with respect to the display images by the liquid crystal panels 1110R, 1110B.
Note that since light corresponding to the primary colors R, G, and B is incident on the liquid crystal panels 1110R, 1110B, and 1110G by the dichroic mirror 1108, it is not necessary to provide a color filter.

<3-5-2: Mobile computer>
Next, an example in which the liquid crystal panel AA is applied to a mobile personal computer will be described. FIG. 9 is a perspective view showing the configuration of this personal computer. In the figure, a computer 1200 includes a main body 1204 having a keyboard 1202 and a liquid crystal display unit 1206. The liquid crystal display unit 1206 is configured by adding a backlight to the back surface of the liquid crystal panel 1005 described above.

<3-5-3: Mobile phone>
Further, an example in which the liquid crystal panel AA is applied to a mobile phone will be described. FIG. 10 is a perspective view showing the configuration of this mobile phone. In the figure, a mobile phone 1300 includes a reflective liquid crystal panel 1005 together with a plurality of operation buttons 1302. In the reflective liquid crystal panel 1005, a front light is provided on the front surface thereof as necessary.

  In addition to the electronic devices described with reference to FIGS. 8 to 10, a liquid crystal television, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a work Stations, videophones, POS terminals, devices equipped with touch panels, and the like can be mentioned. Needless to say, the present invention can be applied to these various electronic devices. The panel plate may be one using an organic LED instead of liquid crystal as an electro-optical material, one using plasma, or one using an inorganic electroluminescence element. Further, it can be applied to an electrophoretic panel such as electronic paper.

1 is a block diagram illustrating an overall configuration of a liquid crystal display device according to an embodiment of the present invention. It is a block diagram which shows the electrical constitution of liquid crystal panel AA. It is a circuit diagram which shows the equivalent circuit of the reference voltage generation circuits 201a-204a. It is a perspective view which shows the mechanical structure of liquid crystal panel AA. FIG. 5 is a sectional view taken along line Z-Z ′ in FIG. 4. It is a conceptual diagram which shows the other structural example of wiring L1-L3. It is a top view which shows the structural example which has arrange | positioned the data line drive circuit to liquid crystal panel AA. It is sectional drawing of the video projector which is an example of the electronic device to which the liquid crystal display device is applied. It is a perspective view which shows the structure of the personal computer which is an example of the electronic device to which the liquid crystal display device is applied. It is a perspective view which shows the structure of the mobile telephone which is an example of the electronic device to which the liquid crystal display device is applied.

Explanation of symbols

  2. Scanning lines, 3 ... Data lines, 100 ... Scanning line drive circuits, 201-204 ... Data line drive circuits, L1-L3 ... Wirings, B1-B5 ... Flexible substrates, C ... External substrates, AA ... Liquid crystal panels.

Claims (8)

A plurality of data lines, a plurality of scanning lines, a pixel region in which a plurality of pixels corresponding to intersections of the data lines and the scanning lines are formed, and a plurality of data line driving circuits for supplying an image signal to the data An electro-optical device comprising:
The plurality of data line driving circuits are arranged corresponding to each of the plurality of regions constituting the pixel region, and each data line driving circuit arranged in the region includes a high potential power source and a low potential power source. DA that outputs a plurality of ladder resistors connected in series between each other and each gradation voltage from each connection point of the ladder resistors, converts image data from a digital signal to an analog signal, and outputs the image signal to the data line With a converter ,
The electro-optical device , wherein the ladder resistors of the respective data driving circuits are connected to each other at connection points corresponding to the same gradation .   The electro-optical device according to claim 1, wherein the plurality of wirings are provided at equal intervals with respect to the plurality of ladder resistors.   2. The electro-optical device according to claim 1, wherein the plurality of wirings are spaced apart from the plurality of ladder resistors as the distance from the center gray scale increases. The electro-optical device includes: an electro-optical panel in which the pixel region is formed;
A flexible substrate connected to the electro-optical panel and an external substrate;
The plurality of data line driving circuits are provided on the flexible substrate,
The electro-optical device according to any one of claims 1 to 3, wherein the plurality of wirings are formed on the flexible substrate, the electro-optical panel, or the external substrate. The electro-optical device includes: an electro-optical panel in which the pixel region is formed;
A flexible substrate connected to the electro-optical panel and an external substrate;
The plurality of data line driving circuits are provided in the electro-optical panel,
The electro-optical device according to any one of claims 1 to 3, wherein the plurality of wirings are formed on the electro-optical panel, the flexible substrate, or the external substrate. The electro-optical device includes: an electro-optical panel in which the pixel region is formed;
A flexible substrate connected to the electro-optical panel and an external substrate;
The plurality of data line driving circuits are provided on the external substrate,
The electro-optical device according to any one of claims 1 to 3, wherein the plurality of wirings are formed on the electro-optical panel, the flexible substrate, or the external substrate.   The plurality of data line driving circuits are each configured as an IC chip, and each of the IC chips is fixed via an anisotropic conductive film. Electro-optic device.   An electronic apparatus comprising the electro-optical device according to claim 1.

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