JP2008008963A - Display panel - Google Patents

Abstract

The present invention provides a large display panel having a large screen and a display panel capable of super large display in which a plurality of display panels are arranged in a tile shape.
The display panel can be driven by using a thin film transistor substrate smaller than a printed circuit board because the pitch of the thin film transistor array is smaller than the pitch of the pixel electrodes. Therefore, even when a plurality of display panels are brought close to each other, a sufficient dimension margin for wiring connection can be obtained, and a useless area is not generated between adjacent display screens, so that a large display screen can be easily realized. Further, the uniformity of the thin film transistor can be increased, and a display panel with high quality can be obtained. Furthermore, a display panel that is not easily damaged can be provided by a structure using a printed board instead of a glass substrate.
[Selection] Figure 1

Description

  The present invention relates to a display panel such as a liquid crystal display device, and more particularly to a display panel capable of large display, which enables a large display by connecting a plurality of display panels.

Conventionally, a display panel using a liquid crystal display (LCD) or a plasma display (PDP) has been provided.
7A and 7B are diagrams illustrating an example of a display panel using a conventional thin film transistor. FIG. 7A is a perspective view and FIG. 7B is a cross-sectional view (see Non-Patent Document 1).
As shown in the figure, a display medium 120 such as a liquid crystal is disposed on a glass substrate 100 on which a driving circuit by a thin film transistor array 110 is mounted. Note that a counter electrode 121 is disposed on the display medium 120.
Further, the glass substrate 100 has a size larger than that of the display medium 120, and drive wirings 122 and 123 are drawn out from end portions on two sides of the display medium 120 and connected to the thin film transistor array 110.
Edited by Shoichi Matsumoto “Liquid Crystal Display Technology-Active Matrix LCD” p.70 Figure 2.14

  By the way, a large display may be performed by arranging a plurality of display panels as described above. In this case, since it is necessary to connect drive wiring to each of the plurality of display panels, a connection region is always required at the end of the display panel. For this reason, at least two sides of the display panel cannot be used as display areas.

  The reason why the display area is narrowed by the presence of the connection area provided in each display panel is that a glass substrate is used as the display panel material, so the electrode terminals of the display panel are connected to the display surface of the display panel. This is because they must be provided on the same surface.

  An object of the present invention is to provide a large display panel having a large screen and a display panel that enables a super large display in which a plurality of display panels are arranged in a tile shape. The object is to provide a display panel with good characteristics.

In order to achieve the above-described object, the display panel of the present invention includes a printed circuit board in which matrix-like pixel electrodes are arranged on the front surface side and a back electrode connected to the pixel electrode is arranged on the back surface side, and the print A display medium disposed on the front surface side of the substrate and connected to the pixel electrode; and a thin film transistor array disposed on the back surface side of the printed circuit board and connected to the back surface electrode, and driving the thin film transistor array in a matrix A display panel for performing display on the display medium on the front surface side, wherein a pitch of the thin film transistor array is smaller than a pitch of pixel electrodes.
In the display panel of the present invention, the printed board includes a capacitor disposed between the pixel electrode and the common electrode. In the display panel of the present invention, the semiconductor layer of the thin film transistor array is an oxide semiconductor or an organic semiconductor.

  In the display panel of the present invention, the thin film transistor array includes a ring-shaped gate electrode formed on an insulating substrate, an insulating layer formed thereon, an island-shaped drain electrode formed thereon, It has a source electrode surrounding the periphery and at least a semiconductor layer formed between the drain and source, and the gate electrode has a shape including a gap between the drain and source when viewed in a direction perpendicular to the substrate surface. A thin film transistor array in which thin film transistors are connected to a plurality of gate wirings and a plurality of source wirings and arranged in a matrix. In the display panel of the present invention, the display medium is a liquid crystal display, a plasma display, an organic EL, or electronic paper.

  According to the display panel of the present invention, since the pitch of the thin film transistor array is smaller than the pitch of the pixel electrodes, the display panel can be driven using a thin film transistor substrate smaller than the printed substrate. Therefore, even when a plurality of display panels are brought close to each other, a sufficient dimension margin for wiring connection can be obtained, and a useless area is not generated between adjacent display screens, so that a large display screen can be easily realized. Further, the uniformity of the thin film transistor can be increased, and a display panel with high quality can be obtained. Further, there is an advantage that a display panel which is not easily damaged can be provided by a structure using a printed board instead of a glass substrate.

  In the embodiment of the present invention, an electrode terminal can be provided on the back surface of the display panel surface by using a printed board instead of a glass substrate for the display panel material. In particular, recently, new display technologies such as organic EL and electronic paper have appeared, and the display panel configuration has made it possible to provide a larger display, and the present invention can effectively cope with such a situation.

1A and 1B are diagrams showing a configuration of a display panel according to an embodiment of the present invention. FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view.
As shown in FIG. 1A, the display panel 1 of this example is a combination of a display panel body 2 and a thin film transistor array 3 that causes the display panel body 2 to perform display operation. As shown in FIG. 1B, the display panel main body 2 includes a printed board 21, a display medium 22, and a counter electrode 23. As the display medium 22, liquid crystal, electronic paper, or the like can be used.

  Here, since the pitch of the thin film transistor array 3 is smaller than the pitch of the pixel electrodes 24 of the printed circuit board 21, the display panel 1 can be configured using the thin film transistor array 3 smaller than the printed circuit board 21. Therefore, even when a plurality of display panels 1 are brought close to each other, there is a space around the thin film transistor array 3, so that a sufficient dimension margin for wiring connection can be obtained. Further, the uniformity of the thin film transistor element characteristics can be improved, and the display panel 1 with good quality can be obtained.

  The printed circuit board 21 has a matrix-like pixel electrode 24 on the surface side, is in contact with the display medium 22, and a capacitor 26 is formed or connected between the pixel electrode 24 and the common electrode 25. The wiring from the electrode 24 is connected to the back electrode 27, and the drain electrode 34 of the thin film transistor array 3 is connected to the back electrode 27. By driving the thin film transistor array 3 in a matrix, the display medium 22 on the front surface side is connected. In the display panel 1 that performs display, the pitch of the drain electrodes 34 of the thin film transistor array 3 is smaller than the pitch of the pixel electrodes 24.

  As shown in FIG. 2, the printed circuit board 21 preferably has a structure in which a capacitor 26 is incorporated, but a capacitor may be externally attached. As the substrate with a built-in capacitor, various types such as those using an electric sheet, those using a dielectric paste, and those embedding a capacitor can be used.

  As the substrate 31 of the thin film transistor array 3, a substrate mainly composed of plastic can be used. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyimide (PI), polyetherimide (PEI), polystyrene (PS), polyvinyl chloride (PVC), polyethylene (PE), Plastic films such as polypropylene (PP) and nylon (Ny), and plastic-glass composites such as glass epoxy substrates can be used. Since these are not fragile substrates such as glass substrates, the display panel 1 can be made difficult to break even if it is accidentally dropped.

As the semiconductor 36 of the thin film transistor array 3, an oxide semiconductor or an organic semiconductor can be used. A thin film transistor using these can be formed at a low temperature of 200 ° C. or lower unlike silicon, and thus can be easily formed on the substrate 31 containing plastic as a main component as described above. Specifically, an InGaZnO-based, InZnO-based, ZnGaO-based, InGaO-based, In ₂ O ₃ , Ga ₂ O ₃ , ZnO, SnO ₂ , or a mixture thereof can be used as the oxide semiconductor.
These can be formed by sputtering or laser ablation. As the organic semiconductor, polythiophene derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyallylamine derivatives, polyacetylene derivatives, acene derivatives, oligothiophene derivatives, and the like can be used. These are obtained by application of raw materials or printing / firing.

As shown in FIG. 3 or FIG. 4, the structure of the thin film transistor array 3 includes a ring-shaped (closed line) gate electrode 32 formed on an insulating substrate 31, and an insulating layer 33 formed thereon. An island-shaped (isolated) drain electrode 34 formed thereon, a ring-shaped (closed line-shaped) source electrode 35 surrounding the periphery, and a semiconductor layer 36 formed at least between the drain and source The thin film transistor array 3 is formed by connecting thin film transistors in which the gate electrode 32 includes a drain-source gap when viewed in a plan view and connected to a plurality of gate wirings 32 ′ and a plurality of source wirings 35 ′. .
This structure simplifies the process because off-state current can be suppressed without patterning the semiconductor layer 36.
Here, the semiconductor layer 36 may be under the drain electrode 34 and the source electrode 35 as shown in FIG. 3, or may be over the drain electrode 34 and the source electrode 35 as shown in FIG. Good.

  However, even when the structure does not include a ring-shaped gate electrode or source electrode, the off-state current can be suppressed by patterning the semiconductor layer 36. Further, a sealing layer may be provided on the channel portion of the semiconductor layer 36. Of course, even in that case, a sealing layer is not provided on most of the drain electrode 34 for connection.

  As described above, in the case of one-transistor driving used for liquid crystal and electronic paper, the display panel body 2 has the capacitor 25, so that it is not necessary to form a capacitor in the thin-film transistor array 3. It becomes a simple structure. Furthermore, the capacitance of the capacitor 26 connected to each pixel electrode 24 can be increased, the thin film transistor can be formed within the pitch, the channel width can be increased, and the drive current can be increased.

  The display panel 1 has a circuit as shown in FIG. That is, the capacitor 26 and the display medium 22 are connected to the drain electrode 34 of the thin film transistor, and the signal voltage is applied to the source wiring 35 ′ connected to the source electrode 35, and the gate wiring 32 ′ connected to the gate electrode 32. When the thin film transistor is turned on by the selected voltage, the signal voltage is held by the capacitor 26. Therefore, the voltage continues to be applied to the display medium 22 even after the thin film transistor is turned off. The common electrode 25 is connected to a constant voltage.

  When a plurality of display panels 1 are arranged, they can be arranged without a gap as shown in FIG. That is, it is possible to connect the common signal wiring x or the selection wiring y to a plurality of matrices and drive the whole as one matrix by the common driving circuit 4. Of course, each display panel may be driven.

  As the gate electrode 32, the drain electrode 34, the source electrode 35, the gate wiring 32 ', and the source wiring 35' of the thin film transistor array 3, a metal such as Al, Cr, Au, Ag, Cu, Ti, Ni, or a conductive material such as ITO is used. A membrane can be used. These can be formed by vapor deposition, sputtering, or the like. Alternatively, Ag ink, Ni ink, or the like may be printed and fired.

As the gate insulating film 33 of the thin film transistor array 3, an inorganic insulating film such as SiO ₂ , Al ₂ O ₃ , SiN, or SiON, or an organic insulating film such as polyvinyl phenol, epoxy, or polyimide can be used. The inorganic insulating film can be formed by sputtering, vapor deposition, or the like. For the organic insulating film, a spin coating method or a printing method can be used.

Next, specific examples will be described.
Glass epoxy was used as the insulating substrate 31, and after Al was sputtered, a ring-shaped gate electrode 32 and a gate wiring 32 'were produced by photolithography and etching. Next, SiON of the gate insulating film 33 and InGaZnO 4 of the semiconductor layer 36 were formed by reactive sputtering. Further, after forming a resist pattern, an island-shaped drain electrode 34, a ring-shaped source electrode 35, and a source wiring 35 'were formed by Al sputtering and lift-off. Thus, a thin film transistor array 3 having 80 × 60 dots and a pitch of 0.5 mm was produced. Further, a fluorinated resin was screen-printed on the channel to form a sealing layer.

Here, polyimide was applied to the surface (on the pixel electrode 24 side) of the separately prepared capacitor-embedded printed circuit board 2 and the surface was polished to flatten the pixel electrode 24. Next, polyimide was thinly applied and rubbed. Further, a seal part was printed around the liquid crystal, and after dropping the liquid crystal, a film with the counter electrode 23 was stacked under reduced pressure, and the seal part was UV cured. Further, the drain electrode 34 of the thin film transistor array 3 was held in alignment with the back electrode 27 of the printed circuit board 2 and fixed by underfill. Note that the pitch of the pixel electrodes 24 was 5 mm.
The display panel 1 thus manufactured was driven to confirm that a desired display was possible.

Next, another embodiment will be described.
Glass epoxy was used as the insulating substrate 31, and after Al was sputtered, a ring-shaped gate electrode 32 and a gate wiring 32 'were produced by photolithography and etching. Next, epoxy was spin-coated and baked to form the gate insulating film 33. Further, the island-shaped drain electrode 34, the ring-shaped source electrode 35, and the source wiring 35 'were formed by screen printing with Ag ink. Next, a polythiophene derivative was spin-coated, and a fluorinated resin was screen printed on the channel to form a sealing layer. Thus, a thin film transistor array 3 having 80 × 60 dots and a pitch of 2 mm was produced.

Here, polyimide was applied to the surface (on the pixel electrode 24 side) of the separately prepared capacitor-embedded printed circuit board 2 and the surface was polished to flatten the pixel electrode 24. Next, polyimide was thinly applied and rubbed. Further, a seal part was printed around the liquid crystal, and after dropping the liquid crystal, a film with the counter electrode 23 was stacked under reduced pressure, and the seal part was UV cured. Further, the drain electrode 34 of the thin film transistor array 3 was held in alignment with the back electrode 27 of the printed circuit board 2 and fixed by underfill. Note that the pitch of the pixel electrodes 24 was 5 mm.
The display panel 1 thus manufactured was driven to confirm that a desired display was possible.

  The display panel of the present embodiment as described above is a display panel that can display a large size by connecting a plurality of display panels, and a driver for driving the display does not have to be mounted on each display panel itself. It can often be provided outside the display panel. Moreover, since the connection part of each display panel is provided in the back surface of each display panel, the area of the non-display part of each display panel can be minimized.

  Here, since the pitch of the thin film transistor array is smaller than the pitch of the pixel electrodes, the display panel can be driven using a thin film transistor substrate smaller than the printed circuit board. Therefore, even when a plurality of display panels are brought close to each other, a sufficient dimension margin for wiring connection can be obtained. Further, the uniformity of the thin film transistor can be increased, and a display panel with high quality can be obtained.

  Further, since the thin film transistor array substrate has plastic as a main component, it becomes a display panel that is not easily damaged even when dropped. By using an oxide semiconductor or an organic semiconductor as the semiconductor layer of the thin film transistor array, it becomes possible to use a plastic substrate that is vulnerable to heat. In addition, as a structure of the thin film transistor array, a ring-shaped gate electrode formed on an insulating substrate, an insulating layer formed thereon, an island-shaped drain electrode formed thereon, and a source surrounding the periphery thereof A thin film transistor comprising an electrode and a semiconductor layer formed at least between the drain and source, the gate electrode including a drain-source gap in plan view, and connected to a plurality of gate wirings and a plurality of source wirings By using a thin film transistor array arranged in a matrix, semiconductor patterning can be omitted.

1A and 1B are a perspective view and a cross-sectional view showing a display panel according to an embodiment of the present invention. It is sectional drawing which shows an example of the board | substrate with a built-in capacitor used for the display panel shown in FIG. 2A is a plan view showing an example of a thin film transistor used in the display panel shown in FIG. 1, and FIG. It is the top view (a), BB 'line, and sectional drawing (b) which show the other example of the thin-film transistor used with the display panel shown in FIG. It is a circuit diagram which shows the electric circuit for 1 pixel of the display panel shown in FIG. FIG. 2 is a perspective view showing an example in which a plurality of display panels shown in FIG. It is the perspective view (a) and sectional drawing (b) which show an example of the conventional display panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Display panel, 2 ... Display panel main body, 3 ... Thin-film transistor array, 4 ... Drive circuit, 21 ... Printed circuit board, 22 ... Display medium, 23 ... Counter electrode, 24 ... Pixel electrode, 25 …… Common electrode, 26 …… Capacitor, 27 …… Back electrode, 31 …… Insulating substrate, 32 …… Gate electrode, 32 ′ …… Gate wiring, 33 …… Gate insulating film, 34 …… Drain electrode, 35 ... Source electrode, 35 '... Source wiring, 36 ... Semiconductor layer.

Claims (4)

A printed circuit board in which a matrix-like pixel electrode is disposed on the front surface side, and a back surface electrode connected to the pixel electrode is disposed on the back surface side,
A display medium disposed on the surface side of the printed circuit board and connected to the pixel electrode;
A thin film transistor array disposed on the back side of the printed circuit board and connected to the back side electrode;
A display panel that displays the display medium on the surface side by driving the thin film transistor array in a matrix,
The pitch of the thin film transistor array is smaller than the pitch of the pixel electrodes,
A display panel characterized by that.   The display panel according to claim 1, wherein the printed circuit board includes a capacitor disposed between the pixel electrode and the common electrode.   3. The display panel according to claim 1, wherein the semiconductor layer of the thin film transistor array is an oxide semiconductor or an organic semiconductor. The thin film transistor array includes a ring-shaped gate electrode formed on an insulating substrate, an insulating layer formed thereon, an island-shaped drain electrode formed thereon, a source electrode surrounding the periphery thereof, A thin film transistor having a shape in which the gate electrode includes a gap between the drain and the source when viewed in a direction perpendicular to the substrate surface, and includes a plurality of gate wirings. 4. A display panel according to claim 1, wherein the display panel is a thin film transistor array connected to a plurality of source wirings and arranged in a matrix.

Images