JP4059731B2 - Active matrix substrate and display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix substrate and a display device used for liquid crystal display devices, organic EL display devices, inorganic EL display devices, X-ray sensors, memory elements, and the like.
[0002]
[Prior art]
An active matrix type liquid crystal display device using a thin film transistor (hereinafter abbreviated as “TFT”) as a driving element has a display quality equivalent to or higher than that of a conventional CRT (Cathode Ray Tube). Yes. In addition, it has features of being thin, lightweight, high-definition, and low power consumption, so that a large-screen display device can be manufactured. For this reason, in all fields, active matrix liquid crystal display devices are currently used as next-generation image display devices that replace conventional CRTs. In recent years, organic EL display devices using organic EL as a display medium have been attracting attention as next-generation image display devices.
[0003]
The use of such an image display device as an alternative to a printed material printed on paper, such as electronic paper, as well as a replacement for a conventional CRT is being studied. For this reason, it is required to configure such an image display device as a flexible display that can be carried without being broken even if it is bent or rolled.
[0004]
In order to realize a flexible display using a technology such as a liquid crystal display device or an organic EL display device, the substrate needs to be flexible. Instead of glass, which is a conventional substrate material, room temperature is required. As a substrate material, plastic or stainless that can be deformed must be used. In order to form a TFT on such a substrate, a new problem arises due to a change in the substrate material, and therefore, a different contrivance is required.
[0005]
For example, when a plastic substrate is used for a flexible display, it is necessary to form a gas barrier layer that does not transmit gas or moisture on the entire surface of the plastic substrate in order to prevent degassing and water absorption to the plastic substrate. Further, in order to reduce damage to the plastic substrate due to heat and suppress thermal stress, the thin film provided on the plastic substrate needs to be deposited at a low temperature. However, if the deposition temperature is too low, the film quality of the deposited thin film is deteriorated, which may impair the performance and reliability of the TFT as a switching element. For this reason, the formation temperature of the thin film must be optimized more strictly than before. Further, since the substrate can be deformed at room temperature, it is necessary to prevent the substrate itself from being warped by the stress of the thin film formed on the substrate.
[0006]
These problems are recognized as important problems to be overcome in realizing flexible disk play, and various proposals for solving the problems have been made. In recent years, academic societies and others have reported that a TFT array is formed on a plastic substrate at a relatively lower temperature than before and has been successfully driven.
[0007]
[Problems to be solved by the invention]
Once a TFT array is successfully formed on a substrate made of a material that can be deformed at room temperature, such as plastic, in order to realize a flexible display with practicality, its performance and reliability in practical use. It is necessary that there is no problem with sex. Specifically, even if the flexible display is bent or rounded, it is necessary that the TFT of the flexible display operates normally and does not affect its performance and reliability.
[0008]
However, according to the conventional technology, when the substrate is bent or rounded, the insulating film, the semiconductor layer, the conductive layer, etc. constituting the TFT are cracked, and the performance and reliability of the TFT are remarkably lowered. Occurs. This problem will be described with reference to the drawings.
[0009]
FIG. 10 schematically shows a cross section of a conventional active matrix substrate 101 in which a plurality of TFTs 10 are formed in an array on a plastic substrate 11. FIG. 11 schematically shows the structure of the TFT 10.
[0010]
As described above, since the active matrix substrate 101 is formed using the plastic substrate 11 as a substrate, degassing from the plastic substrate 11 is prevented between the plastic substrate 11 and the TFT 10, and In order to prevent moisture absorption, a gas barrier layer 4 is provided. The plastic substrate 11 is flexible.
[0011]
On the other hand, the TFT 10 has the same structure as a TFT used in a display device in which a conventional substrate is not deformed. Specifically, as shown in FIG. 8, the TFT 10 includes a gate electrode 5, a gate insulating film 6 formed on the gate electrode, a semiconductor layer 7 formed on the gate insulating film 6, and n. ⁺ Layers 8 and n ⁺ And source and drain electrodes 9 provided on the layer.
[0012]
Therefore, as shown in FIG. 10, when the plastic substrate 11 is rolled so that the surface 11a of the plastic substrate 11 is on the inside, stress acts on the TFT 10 formed on the surface 11a. However, as described above, the TFT 10 formed on the plastic substrate 11 has the same structure as the TFT used in the display device in which the conventional substrate is not deformed. For example, a crack 12 is generated from the edge portion of the gate electrode 5 to the gate insulating film 6. For this reason, the TFT 10 may not function normally as a switching element. Even if the TFT 10 functions normally, bending the plastic substrate 11 many times concentrates stress on the interface between the gate insulating film 6 and the semiconductor layer 7 and gradually increases the interface state of the semiconductor layer 7. To do. As a result, a change with time in transistor characteristics in which the threshold value of the TFT 10 gradually shifts occurs, which adversely affects the reliability of the TFT 10.
[0013]
As described above, even if an active matrix substrate capable of obtaining good initial characteristics can be manufactured by forming TFTs on a flexible substrate, stress generated by bending the active matrix substrate thereafter. It is difficult to realize a flexible display unless the adverse effects due to the above are reduced.
[0014]
The present invention has been made to solve the above-described problems, and its purpose is to provide an active device that can be bent and rounded while maintaining the performance and reliability of a TFT switching element. It is an object of the present invention to provide a matrix substrate and a display device using such an active matrix substrate.
[0015]
[Means for Solving the Problems]
The active matrix substrate of the present invention includes a flexible substrate, a plurality of scanning wirings formed on the substrate, a plurality of signal wirings formed on the substrate so as to intersect the scanning wirings, A plurality of thin film transistors formed on a substrate and operating in response to a signal applied to a corresponding scanning line; and a plurality of pixel electrodes that can be electrically connected to the corresponding signal line through the thin film transistor; The substrate has a direction with a higher Young's modulus in the main surface of the substrate as compared with other directions, and the scanning wiring extends along the direction with the higher Young's modulus.
[0016]
In a preferred embodiment, the substrate is provided on a surface of the network structure having a plurality of first wire rods and a plurality of second wire rods arranged to intersect the first wire rods. The first wire has a higher Young's modulus than the second wire, and the scanning wiring is formed in parallel with the first wire.
[0017]
In a preferred embodiment, the first wire and the second wire are woven to form the network structure.
[0018]
In a preferred embodiment, the thin film transistor is formed on the first wire.
[0019]
In a preferred embodiment, the plurality of wires or the first wire has a diameter of 10 μm to 2000 μm.
[0020]
In a preferred embodiment, the diameter of the first wire rod is larger than the width of the scanning wiring and smaller than the arrangement pitch of the scanning wiring.
[0021]
In a preferred embodiment, the substrate includes a plurality of wires arranged in parallel and a resin layer provided so as to cover at least a part of the wires, and the scanning wiring is formed in parallel with the wires. ing.
[0022]
In a preferred embodiment, the plurality of wires are arranged at a predetermined interval through the resin layer.
[0023]
In a preferred embodiment, the resin layer has translucency.
[0024]
In a preferred embodiment, the plurality of wires have a higher Young's modulus than the resin layer.
[0025]
In a preferred embodiment, the thin film transistor is formed on the first wire.
[0026]
In a preferred embodiment, the substrate has a flexible plate whose Young's modulus is substantially equal in any direction, a Young's modulus higher than the flexible plate, and is parallel to the scanning wiring. A plurality of wires arranged on the flexible plate.
[0027]
In a preferred embodiment, the scanning wiring is made of metal, and the signal wiring is made of a conductive resin.
[0028]
The display device of the present invention includes any one of the active matrix substrates described above, a counter substrate, and the display matrix layer sandwiched between the active matrix substrate and the counter substrate.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
According to the study of the present inventors, a conventional active matrix substrate has been selected as a flexible substrate having no anisotropy in flexibility. For this reason, it was possible to bend the active matrix substrate in the direction in which the TFT is easily broken.
[0030]
In the present invention, the direction in which the active matrix substrate is bent is regulated so that stress is not applied to a weak portion of the TFT structure. For this purpose, a substrate having a direction with a higher Young's modulus in the main surface of the substrate than the other directions is used as the flexible substrate. Such a substrate has anisotropy with respect to the bending of the substrate, the bending rigidity of the substrate is strong in the direction with a high Young's modulus, and the substrate is difficult to be bent.
[0031]
In the active matrix substrate of the present invention, the TFT array is formed on the substrate having this characteristic so that the scanning wiring extends along the direction in which the Young's modulus of the substrate is high. Since the scanning wiring is used to apply a signal to the gate electrode of the TFT, the TFT gate electrode is provided close to the scanning wiring, or a part of the scanning wiring is used as a gate electrode, A TFT is formed on the substrate. For this reason, by making the direction in which the Young's modulus of the substrate is high and the direction in which the scanning line extends the same, the TFT provided in the vicinity of the scanning line and the scanning line becomes less susceptible to stress, and the TFT has a weak structure. In this case, it is difficult to cause breakdown or change in characteristics due to stress concentration.
[0032]
(First embodiment)
A first embodiment of an active matrix substrate of the present invention will be described. First, a flexible substrate 51 used for an active matrix substrate will be described with reference to FIGS. FIG. 1 shows a cross section of the flexible substrate 51. The flexible substrate 51 includes a network structure 41 having a plurality of first wires 1 and a plurality of second wires, and a resin layer 3 provided on the surface of the network structure 41. As shown in FIG. 2 and FIG. 3, in the net-like structure 41, the plurality of first wire rods 1 and the plurality of second wire rods are arranged in parallel, and the second wire rod 2 is the same as the first wire rod 1. It is arranged to intersect.
[0033]
The first wire 1 and the second wire are woven so as to form a network structure 41 using warp and weft respectively. The network structure 41 shown in FIGS. 1 to 3 is formed by forming the first wire 1 and the second wire into a so-called “plain weave”. However, as long as the plurality of first wire rods 1 are kept in parallel, they may be knitted by other weaving methods. Further, when the first wire 1 and the second wire 2 can be fixed by the resin layer 3, the first wire 1 and the second wire 2 are simply arranged so as to intersect with each other, and the resin layer 3 The network structure 41 may be formed by fixing these wires.
[0034]
The first wire 1 has a higher Young's modulus than the second wire 2, the first wire 1 has a relatively high rigidity, and the second wire 2 has a relatively low rigidity. Preferably, the 1st wire 1 is 1x10. ^Ten It has a Young's modulus of Pa or more, and the second wire 2 is 1 × 10 ⁹ It has a Young's modulus of Pa or higher. As the first wire 1, for example, a thin wire made of stainless steel, copper, tungsten, titanium, or the like can be used. As the second wire 2, for example, a thin wire made of glass, plastic, or the like can be used. In FIG. 3, the first wire 1 and the second wire 2 have a circular cross section, but the cross section may be an ellipse, a triangle, a rectangle, a polygon, or the like. The diameter of the circle inscribed in the cross-sectional shapes of the first wire 1 and the second wire 2 is preferably 10 μm to 2000 μm, but the diameter of the first wire 1 is different from the diameter of the second wire 2. It may be. By appropriately selecting the diameter of the first wire 1, the diameter of the second wire 2, and the weaving method, the distance between the first wires 1 can be adjusted. The optimum wire diameter may vary depending on the application of the active matrix substrate to be manufactured. For example, in the case of a display device, the optimum diameter of the wire may differ depending on the size and resolution. In this case, the diameter of the wire to be used can be selected according to the application.
[0035]
The resin layer 3 planarizes the surface of the net-like structure 41 and regulates the relative arrangement of the first wire 1 and the second wire 2 so that the stitches are not broken. As the resin layer 3, a material such as an empty acrylic resin or a polyimide resin can be used. In the case of forming a transmissive display device, a resin having a high light transmittance is desirable. For example, a resin that transmits 80% or more of light having a wavelength of 500 nm, such as acrylic resin, is desirable. The Young's modulus of the resin layer 3 is at least smaller than the Young's modulus of the first wire 1.
[0036]
In this flexible substrate 51, due to the difference in rigidity between the first wire 1 and the second wire 2 constituting the network structure 41, the second wire 2 is bent in parallel with the first wire 1. It is easy to bend in the direction, and it is difficult to bend in the direction perpendicular to the first wire 1 in which the first wire 1 is bent. This is because the rigidity of the second wire 2 is lower than the rigidity of the first wire 1. For this reason, in the main surface of the flexible substrate 51, the Young's modulus is higher in the direction in which the first wire 1 extends than in other directions.
[0037]
On the other hand, the second wire 2 with a low Young's modulus extends in a direction perpendicular to the direction with a high Young's modulus of the flexible substrate 51. For this reason, it is possible to bend the flexible different substrate 51 so that the 2nd wire 2 may bend. At this time, a force that bends the first wire 1 in a direction perpendicular to the longitudinal direction acts on the first wire 1, but the distance of the cross section of the first wire 1 in this direction is short. Further, the Young's modulus of the first wire 1 is larger than that of the second wire 2. For this reason, the first wire 1 is not substantially deformed, and only the second wire 2 is deformed. That is, stress concentrates on the second wire 2.
[0038]
The flexible substrate 51 can be manufactured by the following method. First, for example, a stainless wire having a diameter of 100 μm is prepared as the first wire 1, and a plastic wire made of polyethersulfone having a diameter of 100 μm is prepared as the second wire 2. The glass transition point of polyalesulfone is about 200 ° C.
[0039]
Next, the first wire 1 and the second wire 2 are woven so as to form a network structure 41 as warp and weft, respectively. In order to weave the 1st wire 1 and the 2nd wire 2, the well-known manufacturing technique and manufacturing apparatus used for preparation of metal meshes, such as a stainless steel screen door and the mesh for screen printing, can be used.
[0040]
Thereafter, a crosslinkable resin is applied onto the network structure 41 by a spin coat method or the like, and the crosslinkable resin is thermally cured by a baking apparatus, and then the surface thereof is planarized by a CMP (Chemical Mechanical Polishing) method or the like, and the resin layer 3 Form.
[0041]
Next, the active matrix substrate 61 of this embodiment will be described. FIG. 4 schematically shows the active matrix substrate 61. The active matrix substrate 61 includes a flexible substrate 51, a plurality of scanning wires 5 formed on the flexible substrate 51, and a plurality of signals formed on the flexible substrate 51 so as to intersect the scanning wires 5. A plurality of thin film transistors (TFTs) 22 formed on the wiring 21 and formed on the flexible substrate 51 and operating in response to a signal applied to the corresponding scanning wiring, and the corresponding signal wiring 21 via the TFT 10 are electrically connected A plurality of pixel electrodes 23 that can be connected to each other. The scanning wiring 5 is arranged in parallel with the first wire 1 of the flexible substrate 51. That is, the scanning wiring 5 extends along the direction in which the Young's modulus of the flexible substrate 51 is high. The diameter of the circle inscribed in the cross-sectional shape of the first wire 1 is preferably at least larger than the width of the scanning wiring 5 and smaller than the arrangement pitch of the scanning wiring.
[0042]
FIG. 5 is an enlarged sectional view showing the vicinity of the TFT 10 of the active matrix substrate 61. As shown in FIG. 5, the scanning wiring 5 is preferably located on the first wire 1. The TFT 10 is formed on the flexible substrate 51 via the gas barrier layer 4 and has a part of the scanning wiring 5 as a gate electrode. The entire size of the TFT 10 is several tens of μm × several tens of μm. For this reason, when the diameter of the circle inscribed in the cross-sectional shape of the first wire 1 is the above-described preferred dimension, the entire TFT 10 is positioned on the first wire 1 as shown in FIG.
[0043]
In the TFT 10, a gate insulating film 6 is formed on the scanning wiring 5, and a semiconductor layer 7 is formed on the gate insulating film 6. The semiconductor layer 7 includes a source electrode 9a and a drain electrode 9b. ⁺ They are electrically connected via the layer 8. The source electrode 9 a is connected to the signal wiring 21, and the drain electrode 9 b is electrically connected to the pixel electrode 23.
[0044]
According to the active matrix substrate 61, the scanning wiring 5 extends in the direction in which the Young's modulus is higher than that of the flexible substrate 51. A part of the scanning wiring 5 is used as a gate electrode, and the TFT 10 is formed on the scanning wiring 5. Yes. Therefore, it is difficult to bend the active matrix substrate 61 so that the scanning wiring 5 bends, and the scanning wiring 5 and the TFT 10 provided on the scanning wiring 5 are not easily subjected to stress. As a result, it becomes difficult for the scanning wiring 5 to be disconnected, to break down in the TFT 10 with a weak structure, or to change characteristics due to stress concentration. Further, since the scanning wiring 5 hardly bends, a conventional scanning wiring material such as Ti or Ta can be used, and the characteristics of the TFT 10 as a switching element are not deteriorated.
[0045]
On the other hand, the flexible substrate 51 can be bent so as to bend in a direction perpendicular to a direction having a high Young's modulus. Since such a flexure of the flexible substrate 51 is parallel to the scanning wiring 5, the scanning line 5 and the TFT 10 provided on the scanning line 5 are not easily subjected to stress. Therefore, the active matrix substrate 61 can be bent in a direction perpendicular to the direction in which the flexible substrate 51 has a high Young's modulus without destroying the TFT 10.
[0046]
In particular, when the scanning wiring 5 is formed on the first wire 1 of the flexible substrate 51, the entire scanning wiring 5 and the TFT 10 are located on the first wire 1. For this reason, as shown in FIG. 6, even if the active matrix substrate 61 is bent in parallel with the first wire 1, only the second wire 2 of the flexible substrate 51 is deformed by the stress, and the highly rigid first The TFTs 10 positioned on the wire 1 and the first wire 1 are hardly subjected to stress due to bending. Therefore, it is possible to realize a display device that can be bent or rounded using the active matrix substrate 61 while maintaining the performance and reliability of the TFT as a switching element.
[0047]
When the active matrix substrate 61 is bent in a direction perpendicular to the direction in which the Young's modulus of the flexible substrate 51 is high, the signal wiring 21 bends. Since the signal wiring 21 is not close to the channel portion of the TFT 10, the bending of the signal wiring 21 has less influence on the destruction of the TFT 10 and the lowering of the reliability than the scanning wiring 5. However, when the active matrix substrate 61 is bent repeatedly, the signal wiring 21 may be fatigued and disconnected. In such a case, it is preferable to form the signal wiring 21 with a conductive resin or the like.
[0048]
From the viewpoint of disconnection of the wiring caused by repeatedly bending the active matrix substrate 61, the signal wiring 21 is disposed in parallel to the direction of high flexibility of the flexible substrate 51, and the scanning wiring 5 is formed of a conductive resin. It is also possible to do. However, in this case, there is a possibility that the characteristics and reliability of the TFT 10 are lowered by forming the scanning wiring 5 with a conductive resin. Therefore, such a configuration is not preferable.
[0049]
The active matrix substrate 61 having the flexible substrate 51 is manufactured by, for example, the following method. As shown in FIG. 5, first, silicon nitride (SiN) is formed on the flexible substrate 51 by plasma CVD. _x ) A gas barrier layer 4 made of a film is formed. The formation conditions of the gas barrier layer 4 are adjusted according to the heat resistant temperature of the flexible substrate 51. In the present embodiment, since the glass transition point of the second wire 2 of the flexible substrate 51 is 200 ° C., it is not preferable to expose the flexible substrate 51 to a temperature higher than 200 ° C. For this purpose, the flexible substrate 51 is heated to 200 ° C., and SiH _Four : 125sccm, NH _Three : 190sccm, N ₂ : The raw material gas is introduced into the chamber at a flow rate of 1000 sccm, and the pressure in the chamber is maintained at 130 Torr, while 0.5 W / cm ² A silicon nitride film is formed at a power density of
[0050]
Next, using a sputtering apparatus, a thin film is formed on the gas barrier layer 4 under the conditions of a substrate temperature: 100 ° C., an Ar flow rate: 100 sccm, a pressure: 5 mTorr, and an output density: 1 W / cm 2 using a gate wiring material such as tantalum as a target. To do. Thereafter, the thin film is patterned to form the scanning wiring 5 having a thickness of 300 nm and a width of 20 μm.
[0051]
Thereafter, the gate insulating film 6 made of silicon nitride, the semiconductor layer 7 made of amorphous silicon, and n made of amorphous silicon containing high-concentration impurities are formed by plasma CVD. ⁺ Layer 8 is formed. The gate insulating film 6 can be formed, for example, under the same conditions as the gas barrier layer 4. The semiconductor layer 7 is made of SiH _Four : 200sccm, H ₂ The raw material gas was introduced into the chamber at a flow rate of 1800 sccm, and the pressure in the chamber was kept at 80 Torr, while 0.1 W / cm ² It can be formed by applying power at a power density of. N ⁺ Layer 8 is PH _Three : 6 sccm, SiH _Four : 200sccm, H ₂ : The raw material gas is introduced into the chamber at a flow rate of 2000 sccm, and the pressure in the chamber is kept at 80 Torr, and 0.2 W / cm. ² It can be formed by applying power at a power density of.
[0052]
Thereafter, the signal wiring 21, the source electrode 9a, and the drain electrode 9b are formed under the same conditions as the scanning wiring 5, and the source electrode 9a and the drain electrode 9b are used as masks to form n ⁺ By etching the layer 8, the TFT 10 is formed. The signal wiring 21 may be formed using a conductive resin or the like. Finally, the active matrix substrate 61 is obtained by forming the pixel electrode 23.
[0053]
(Second Embodiment)
A second embodiment of the active matrix substrate of the present invention will be described with reference to FIGS. 7 shows a cross section of the main part of the active matrix substrate 62 provided with the flexible substrate 52, and FIGS. 8 and 9 show a plan view and a cross sectional view of the flexible substrate 52, respectively.
[0054]
The active matrix substrate 62 includes a flexible substrate 52 having a structure different from that of the flexible substrate 51 of the first embodiment. Specifically, the flexible substrate 52 includes a plurality of first wire rods 1 arranged in parallel at a predetermined interval, and a resin layer 3 that holds the first wire rods 1. The first wire 1 is preferably formed of a material having a high Young's modulus, and preferably has the same characteristics as the first wire 1 of the first embodiment. The resin layer 3 preferably has a Young's modulus lower than that of the first wire 1 and has light transmittance. For example, the resin layer 3 is formed from an acrylic resin, a polyester resin, or the like.
[0055]
As shown in FIG. 8 and FIG. 9, in the flexible substrate 52, the first wire 1 is arranged at a predetermined interval, and the resin layer 3 provided between the first wires 1 can be used. Light is transmitted between the front surface and the back surface of the flexible substrate 52. Therefore, the flexible substrate 52 has a light-transmitting property and is suitable for manufacturing a transmissive display device using the active matrix substrate 62. The light transmittance of the flexible substrate 52 can be arbitrarily adjusted by adjusting the ratio between the thickness of the first wire 1 and the interval between the adjacent first wires 1.
[0056]
Unlike the first embodiment, the flexible substrate 52 does not include the second wire. However, since the first wire 1 is included, the flexible substrate has a higher Young's modulus in the direction in which the first wire 1 extends than in other directions. Therefore, as in the first embodiment, the flexible substrate 52 is easily bent in a direction parallel to the first wire 1, and the flexible substrate 52 is not easily bent in a direction perpendicular to the first wire 1. Yes. Further, since the second wire is not used, it is not necessary to weave two kinds of wires, and the cost for manufacturing the flexible substrate 52 can be reduced.
[0057]
As shown in FIG. 7, in the active matrix substrate 62, the scanning wiring 5 is arranged to be parallel to the first wire 1 of the flexible substrate 52 and to be positioned on the first wire 1. The TFT 10 is also formed on the first wire 1. For this reason, as described in the first embodiment, the active matrix substrate 62 can be bent in the direction perpendicular to the high Young's modulus direction of the flexible substrate 52 without destroying the TFT 10.
[0058]
The active matrix substrate 62 can be manufactured, for example, by the following method. First, a stainless wire having a diameter of 100 μm is prepared as the first wire 1 and arranged in parallel at intervals of 200 μm. Thereafter, the first wire 1 is cured and flattened with an acrylic resin to produce a flexible substrate 52.
[0059]
The gas barrier layer 4 is formed on the flexible substrate 52, and a metal thin film such as Ti or Ta is deposited using a sputtering apparatus. The metal thin film is patterned to form the scanning wiring 5. At this time, the scanning wiring 5 is patterned so as to be positioned on the first wire 1.
[0060]
Thereafter, the gate insulating film 6, the semiconductor layer 7, n are formed by plasma CVD. ⁺ After the layer 8 is formed and the signal wiring 21, the source electrode 9a, and the drain electrode 9b are formed, n is used as a mask. ⁺ Layer 8 is patterned to produce TFT 10. Finally, the active matrix substrate 62 is obtained by forming the pixel electrode 23.
[0061]
In the first and second embodiments, by forming the TFT on the first rigid wire, the TFT can be prevented from being broken by bending the active matrix substrate, and the TFT characteristics and reliability can be reduced. It was suppressed. However, when the active matrix substrate is bent so that the polarities are not so small and the stress acting on the TFT is small, the TFT does not necessarily have to be formed on the first rigid wire. However, even in this case, in order to suppress the separation of the scanning wiring from the substrate and the concentration of stress on the gate insulating film and the semiconductor layer of the TFT formed in the vicinity of the scanning wiring, It is preferable to restrict the bending of the active matrix substrate such that the substrate is bent.
[0062]
For this reason, in an active matrix substrate including a flexible substrate, it is preferable to form a highly rigid wire material inside the substrate or outside the substrate so as to be parallel to the scanning wiring. In this case, a flexible plate having substantially the same Young's modulus in any direction is used as the substrate, and a wire having a higher Young's modulus than the flexible plate is used as the wire. With such a structure, the Young's modulus of the substrate becomes higher in the direction in which the scanning wiring extends than in other directions, and the bending of the active matrix substrate in the direction in which the scanning wiring is bent can be restricted. For example, after the TFT structure is formed on the plastic substrate, the bending direction of the substrate may be regulated by arranging a stainless steel wire or the like on the plastic substrate so as to be parallel to the scanning wiring.
[0063]
Also, a flexible plate having substantially the same Young's modulus in any direction is prepared, and a plurality of grooves are provided in parallel on the back surface of the flexible plate to bend in a direction perpendicular to the direction in which the grooves are provided. It is easy to obtain a substrate that is not easily bent in a parallel direction. An active matrix substrate may be manufactured by forming an array of TFTs in which the scanning wirings are arranged in parallel with the grooves on the surface of the substrate. In this case, if the scanning wiring is disposed on the ridge formed between the grooves, the structure is more difficult to apply stress to the scanning wiring and the TFT.
[0064]
In the first and second embodiments, the active matrix substrate including the TFT formed on the scanning wiring using a part of the scanning wiring as the gate electrode has been described. However, the active matrix substrate of the present invention is not limited to the one having the TFT of this structure. For example, the active matrix substrate of the present invention may include a TFT having an electrode branched from a scanning wiring as a gate electrode. Since the TFT with this structure is located in the vicinity of the scanning wiring, if the scanning wiring is formed on the first wire, the TFT is also located on the first wire. Therefore, as described in detail in the first embodiment, the first wire rod can suppress the breakdown of TFT and the deterioration of characteristics and reliability.
[0065]
In the first and second embodiments, in addition to the first wire or the second wire, a third wire having a Young's modulus smaller than that of the first wire may be arranged together.
[0066]
The active matrix substrate according to these modified examples described above according to the first and second embodiments is preferably used for a liquid crystal display device. For example, a counter substrate provided with a counter electrode and a color filter layer is prepared, an alignment film is provided on the active matrix substrate and the counter substrate, an alignment process is performed by a rubbing method, and the alignment processing surfaces are set inside to each other through a sealing material. The liquid crystal display device according to the present invention can be obtained by injecting liquid crystal between the laminated substrates.
[0067]
In addition to a liquid crystal display device, a material that modulates optical properties or emits light when a voltage is applied is used as a display medium layer, and is interposed between the counter substrate and the active matrix substrate of the present invention. By holding such a display medium layer, various display devices can be obtained. For example, the active matrix substrate of the present invention is also suitably used for display devices such as organic EL display devices and inorganic EL display devices using organic or inorganic fluorescent materials as the display medium layer. Furthermore, it can also be suitably used as an active matrix substrate used for X-ray sensors, memory elements, and the like.
[0068]
【The invention's effect】
According to the present invention, it is possible to realize an active matrix substrate capable of bending a substrate while reducing disconnection of scanning lines, element destruction of TFTs, or deterioration of TFT characteristics and reliability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a flexible substrate used for an active matrix substrate according to a first embodiment of the present invention.
2 is a plan view showing a network structure of the flexible substrate of FIG. 1; FIG.
3 is a cross-sectional view showing a network structure of the flexible substrate of FIG. 1. FIG.
FIG. 4 is a schematic view showing an active matrix substrate according to the first embodiment of the present invention.
5 is a cross-sectional view showing a main part of the active matrix substrate of FIG. 4;
6 is a cross-sectional view showing a state in which the active matrix substrate of FIG. 4 is bent.
FIG. 7 is a cross-sectional view showing a main part of an active matrix substrate according to a second embodiment of the present invention.
8 is a plan view showing a flexible substrate used for the active matrix substrate of FIG. 7. FIG.
9 is a cross-sectional view showing a flexible substrate used in the active matrix substrate of FIG.
FIG. 10 is a cross-sectional view showing a state in which a conventional active matrix substrate is bent.
11 is a cross-sectional view showing a main part of the active matrix substrate of FIG.
[Explanation of symbols]
1 First wire
2 Second wire
3 Resin layer
4 Gas barrier layer
5 Scanning wiring
6 Gate insulation film
7 Semiconductor layer
8 n ⁺ layer
9a Source electrode
9b Drain electrode
10 TFT
21 Signal wiring
23 Pixel electrode
41 Reticulated structure
51, 52 Flexible substrate
61, 62 Active matrix substrate

Claims (11)

A flexible substrate;
A plurality of scanning lines formed on the substrate;
A plurality of signal wirings formed on the substrate to intersect the scanning wirings;
A plurality of thin film transistors formed on the substrate and operating in response to signals applied to corresponding scanning lines;
A plurality of pixel electrodes that can be electrically connected to the corresponding signal wiring through the thin film transistor;
In the main surface of the substrate, the substrate has a direction having a higher Young's modulus compared to other directions, and the scanning wiring extends along the direction in which the Young's modulus is high ,
The substrate includes a network structure having a plurality of first wire rods and a plurality of second wire rods arranged to intersect the first wire rods, and a resin layer provided on a surface of the network structure, The first wire has a higher Young's modulus than the second wire, and the scanning wiring is formed in parallel with the first wire,
The thin film transistor is an active matrix substrate formed on the first wire . Said first wire and said second wire material by being woven, the active matrix substrate according to claim 1 that forms the network. 3. The active matrix substrate according to claim 1, wherein the first wire has a diameter of 10 μm to 2000 μm. A flexible substrate;
  A plurality of scanning wirings formed on the substrate;
  A plurality of signal wirings formed on the substrate to intersect the scanning wirings;
  A plurality of thin film transistors formed on the substrate and operating in response to signals applied to corresponding scanning lines;
  A plurality of pixel electrodes that can be electrically connected to the corresponding signal wiring through the thin film transistor;
  In the main surface of the substrate, the substrate has a direction having a higher Young's modulus compared to other directions, and the scanning wiring extends along the direction in which the Young's modulus is high,
  The substrate includes a plurality of wires arranged in parallel and a resin layer provided so as to cover at least a part of the wires, and the scanning wiring is formed in parallel with the wires,
  The thin film transistor is an active matrix substrate formed on the plurality of wires. The active matrix substrate according to claim 4 , wherein the plurality of wires are arranged at predetermined intervals with the resin layer interposed therebetween. The active matrix substrate according to claim 5 , wherein the resin layer has translucency. The active matrix substrate according to claim 4 , wherein the plurality of wires have a higher Young's modulus than the resin layer. The active matrix substrate according to claim 4 , wherein the wire has a diameter of 10 μm to 2000 μm. The diameter of the first wire is larger than the width of the scan lines, the active matrix substrate according to claim 1 arranged smaller than the pitch of the scanning lines. The scanning line is made of metal, the active matrix substrate according to any one of claims 1 to 9, wherein the signal line is made of a conductive resin. Display device comprising an active matrix substrate according to claims 1 to 10, a counter substrate, and a display medium layer sandwiched between the active matrix substrate and the counter substrate.

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