JP2005266815A - Liquid crystal display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a display defect from being caused by a short circuit formed between upper and lower electrodes by insertion of conductive foreign matter by using a structure in which two substrates in a liquid-crystal display device are not easily short-circuited. <P>SOLUTION: An insulating film 16 consisting of various insulators is formed on a wiring layer 12, a first electrode portion 13, a insulating layer 14, and a second electrode layer 15. The insulating film 16 nearly entirely covers the surfaces of the wiring layer 12 and an MIM element, and a part of the insulating film 16 is slightly inserted into the inner side of a pixel region. A portion of the insulating film 16 corresponding to a pixel contact portion 15b of the insulating film 16 serves as an opening for assuring the electric conductivity between the MIM element and a pixel electrode 17. The peripheral portion of the pixel electrode 17 is formed to overlap the inner edge portion of the insulating film 16 . The peripheral portion is designed to be in contact with the pixel contact portion 15b of the second electrode layer 15 through the opening of the insulating film 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to an inner surface structure of a substrate constituting a liquid crystal panel.

  In general, a liquid crystal display device includes a liquid crystal panel in which two substrates having electrodes corresponding to pixel regions arranged on the display surface are provided on the inner surface, and a liquid crystal layer is sandwiched between the substrates. . In order to drive the liquid crystal display device, various electrodes can be displayed by changing the optical characteristics of the liquid crystal layer by applying an electric field to the liquid crystal layer with the electrodes. In this case, a wiring layer for applying a predetermined driving potential to the electrodes may be formed in parallel on the inner surface of at least one substrate.

  In an active matrix liquid crystal display device, an active element such as a TFT (thin film transistor) element or a MIM (metal-insulator-metal) element is connected to a wiring layer formed on the inner surface of the element substrate. These active elements are connected to each pixel electrode formed for each pixel region.

  On the other hand, in a liquid crystal display device capable of color display, for example, by forming a colored resist or the like in a predetermined pattern on the inner surface of the counter substrate facing the element substrate on which the active element is formed, red (R ), Green (G), and blue (B) colored layers are arranged. After the color filter is covered with an overcoat film, a transparent counter electrode made of ITO (indium tin oxide) is further formed. There is something formed.

  In the conventional liquid crystal display device, a liquid crystal layer is sealed between two substrates, and a predetermined voltage is applied between two opposing electrodes formed on the inner surfaces of both substrates to align liquid crystal molecules. It is configured to change. However, in the manufacturing process, conductive foreign matter may be mixed between the two substrates or inside the liquid crystal. In this case, the conductive foreign matter is between the electrodes formed on the two substrates. In some cases, there is an influence on the electric field to be applied to the liquid crystal, or a point defect may occur due to a short circuit between the electrodes.

  Here, even if a conductive foreign substance enters the pixel region and short-circuits the electrodes, only the pixel does not operate in the active matrix type liquid crystal display device, and only a so-called point defect occurs. However, if similar foreign matter exists above the wiring layer of the element substrate or the active element, the wiring layer and the counter electrode may be short-circuited. Line defects may occur. Unlike the above point defects, such a line defect causes a defect in the liquid crystal panel at the time of occurrence, so that the yield during the production of the liquid crystal display device is remarkably reduced and the production process and production cost are greatly affected.

  In particular, such defects due to conductive foreign matter are difficult to prevent by inspection in the manufacturing process because the foreign matter may occur after the shipment after the shipment even if there is no abnormality during manufacturing. Therefore, it is necessary to take complete measures to prevent defects even if foreign matter is present.

  Accordingly, the present invention solves the above-mentioned problem, and the problem is that a display defect caused by a short circuit between the upper and lower electrodes is achieved by adopting a structure in which a short circuit between two substrates in a liquid crystal display device is unlikely to occur. Is to prevent.

  In order to solve the above-mentioned problems, the present invention has a means in which a liquid crystal layer is sandwiched between two substrates, and a wiring layer, a pixel electrode, and the wiring layer are formed on the inner surface of one of the substrates. And an active element connected directly or indirectly between the pixel electrode and an insulating film, the insulating film covering the wiring layer and the active element, and over the end of the insulating film The pixel electrode is formed so that the peripheral edge of the pixel electrode overlaps, and is not formed inside the peripheral edge of the pixel electrode.

  According to this means, by covering the surface of the wiring layer with an insulating film, there is no risk of contact of the conductive foreign matter with the wiring layer and a short circuit between the wiring layer and the counter electrode via the foreign matter. The occurrence of fatal line defects can be prevented.

  Here, the active element includes a connection portion that conducts the active element and the pixel electrode, and the insulating film is disposed so as to insulate between the wiring layer and the pixel electrode, and the connection portion It is preferable to provide an opening for ensuring electrical continuity between the pixel electrode and the pixel electrode.

  According to this means, since the insulating film is formed not only on the surface of the wiring layer but also between the wiring layer and the pixel electrode, the conductive portion between the connection portion and the pixel electrode is not provided. Except for this, there is no contact with each other, and deterioration of the display state due to a short circuit between the wiring layer and the pixel electrode can be prevented.

  Preferably, an MIM element is formed between the connection portion and the pixel electrode, and the insulating film covers the surface of the MIM element.

  According to this means, since the insulating film also covers the surface of the MIM element, contact between the MIM element and the conductive foreign matter and a short circuit between the counter electrode via the foreign matter are prevented.

  Preferably, a TFT element is formed between the connection portion and the pixel electrode, and the insulating film is provided on a wiring layer connected to the TFT element.

  According to this means, the contact between the wiring layer connected to the TFT element and the conductive foreign material is prevented from being short-circuited between the counter electrode through the foreign material.

  The insulating film preferably has a light shielding property.

  According to this means, since it is not necessary to provide a light shielding member on the substrate on which the color filter is formed, the manufacturing cost can be reduced and high alignment accuracy between the opposing substrates can be eliminated.

  Next, a liquid crystal layer is sandwiched between the two substrates, and the wiring layer, the pixel electrode, and the wiring layer and the pixel electrode are directly or indirectly disposed on the inner surface of one of the substrates. In a method of manufacturing a liquid crystal display device including a connected active element and an insulating film, the wiring layer and the active element are formed on an inner surface of one of the substrates, and the wiring layer and the active element are formed. The insulating film is formed to cover, and the pixel electrode is formed so that the peripheral edge of the pixel electrode overlaps the edge of the insulating film, and the insulating film is formed inside the peripheral edge of the pixel electrode. It is characterized by not.

  According to this means, the surface of the wiring layer can be covered with the insulating film, and between the wiring layer and the pixel electrode can be insulated with the insulating film. And the pixel electrode can be secured.

  In this case, after forming the MIM element connected between the connection portion and the pixel electrode, it is preferable to form the insulating film so as to cover the surface of the MIM element.

  Next, embodiments according to the present invention will be described with reference to the accompanying drawings.

(First embodiment)
1 and 2 show an embodiment of a liquid crystal display device according to the present invention. The present embodiment shows an example in which the present invention is applied to an active matrix type liquid crystal display device provided with MIM elements for each pixel region.

  In the present embodiment, as shown in FIG. 2, a transparent base layer 11 is formed on the surface of the element substrate 10. The base layer 11 is for improving the adhesion between the element substrate 10 and a film such as a wiring layer formed thereon. A wiring layer 12 made of a metal thin film is formed in a predetermined pattern shape on the surface of the base layer 11 as shown in FIG. The wiring layer 12 is integrally provided with a first electrode portion 13 formed so as to protrude for each pixel region.

  A thin insulating layer 14 formed by an anodic oxidation method is provided on the surface of the wiring layer and the first electrode portion 13, and the second electrode layer 15 is formed through the insulating layer 14. The second electrode layer 15 includes an electrode portion 15a located immediately above the first electrode portion 13, and a pixel contact portion 15b extending from the electrode portion 15a and projecting greatly.

  The electrode portion 15a of the first electrode portion 13, the insulating layer 14, and the second electrode layer 15 constitutes an MIM element that is a two-terminal active element made of metal-insulator-metal.

  An insulating film 16 made of various insulators is formed on the wiring layer 12, the first electrode portion 13, the insulating layer 14, and the second electrode portion 15. As shown in FIG. 1, the insulating film 16 covers the entire surface of the wiring layer 12 and the MIM element, and part of the insulating film 16 slightly enters the inside of the pixel region.

  Here, the insulating film 16 is not formed on the surface of the pixel contact portion 15b in the second electrode layer 15, and a portion corresponding to the pixel contact portion 15b is composed of an MIM element and a pixel electrode described later. 17 is an opening for ensuring electrical continuity with 17.

  A transparent pixel electrode 17 made of ITO is formed in the pixel region where the MIM elements are formed one by one. The peripheral edge portion of the pixel electrode 17 is formed so as to ride on the inner edge portion of the insulating film 16, and is configured to contact the pixel contact portion 15 b of the second electrode layer 15 through the opening of the insulating film 16. ing.

  On the other hand, as shown in FIG. 2, on the inner surface of the counter substrate 20, a colored layer 21 </ b> C that exhibits any color tone of red (R), green (G), and blue (B), and these colored layers 21 </ b> C. A color filter 21 including a black matrix layer 21BM formed therebetween is formed. A protective film 22 made of a transparent resin is deposited on the surface of the color filter 21. This protective film 22 is for protecting the color filter 21. A counter electrode 23 made of ITO formed in a stripe shape is formed on the surface of the protective film 22. Here, the colored layers in the present embodiment are not limited to the above three colors of red, green, and blue, and may be, for example, three colors of cyan, magenta, and yellow.

  An alignment film is further applied and formed on the inner surfaces of the element substrate 10 and the counter substrate 20, and a rubbing process is performed in a predetermined direction. The liquid crystal layer 30 is disposed in a state of being sandwiched between these alignment films.

  In this embodiment, since the insulating film 16 completely covers the wiring layer 12 and the surface of the MIM element, even if conductive foreign matter is mixed between the element substrate 10 and the counter substrate 20, the wiring There is no risk of conductive contact between the layer 12 and the MIM element and the counter electrode. Therefore, it is possible to prevent occurrence of a cross-line-like line defect that is fatal to the liquid crystal display device.

  Further, since the insulating film 16 is interposed between the wiring layer 12 and the pixel electrode 17 except where the pixel contact portion 15b of the second electrode layer 15 and the pixel electrode 17 are in conductive contact, the wiring It is possible to prevent a short circuit between the layer 12 and the pixel electrode 17 and a leak current between them.

  3 to 6 show main manufacturing steps of the element substrate 10 in the above embodiment. As shown in FIG. 3, Ta is deposited on the entire surface of an element substrate 10 made of alkali-free glass by a sputtering method, and a base layer 11 made of Ta oxide is formed by thermal oxidation. The underlayer may be formed by Ta oxide RF sputtering. Next, Ta or a Ta alloy is again deposited on the surface of the underlying layer 11 by sputtering, and patterned by photolithography to form a wiring layer 12 (see FIG. 1, not shown in FIG. 3). .

  Here, the first electrode portion 13 is integrally formed on the wiring layer 12 as described above.

  Next, as shown in FIG. 4, a thin insulating layer 14 is formed on the surfaces of the wiring layer 12 and the first electrode portion 13 by an anodic oxidation method. The insulating layer 14 is formed by oxidizing the surface of Ta by immersing the element substrate 10 in the electrolytic solution and causing a current to flow between the wiring layer 12 and the counter electrode in the electrolytic solution. Since this insulating film 14 determines the electrical characteristics of the MIM element, it is necessary to strictly set the film forming conditions, film thickness, etc., and if necessary, annealing (heat treatment) may be performed after film forming. .

  Further, Cr is deposited on the insulating film 14 formed on the surface of the first electrode portion 13 by a sputtering method, and predetermined patterning is performed to form the second electrode layer 15. As shown in FIG. 1, the second electrode layer 15 includes an electrode portion 15 a formed so as to partially overlap the first electrode layer 13 and a pixel contact for making conductive contact with a pixel electrode 17 described later. Part 15b. In addition, aluminum, titanium, molybdenum or the like may be used for the second electrode layer 15.

  Next, as shown in FIG. 5, an insulating film 16 having a predetermined thickness is formed on the surface of the element substrate 10. As this insulating film, an inorganic insulating film such as Ta oxide, silicon oxide, silicon nitride, or aluminum oxide formed by sputtering or the like is preferable. These insulating films 16 are formed so as to have a film thickness sufficient to ensure sufficient insulation between the lower wiring layer 12 and the like. For example, the thickness is preferably about 1000 mm or more for Ta oxide and about 400 mm or more for silicon oxide. Generally, the thickness of the insulating film 16 is about 400 to 5000 mm. The insulating film 16 may be made of polyimide resin, acrylic resin, or the like.

  The insulating film 16 formed as described above is a mask having a plane pattern substantially the same as the light-transmitting region (the portion other than the region where the black matrix 21BM is formed) of the color filter 21 on the counter substrate 20 shown in FIG. Patterning is performed by the photolithography process used, and the region A corresponding to the pixel region of the liquid crystal display device of FIG. 5 and the region B that is the opening corresponding to the pixel contact portion 15b of the second electrode layer 15 are removed.

  Here, when the patterning of the insulating film 16 is performed in common with the mask for forming the light-transmitting region of the color filter, the number of masks used in the photolithography process can be reduced, and the manufacturing cost can be reduced. Can do.

  Finally, as shown in FIG. 6, ITO is deposited by the whole surface sputtering method and patterned to form the pixel electrode 17. The pixel electrode 17 completely covers the region A from which the insulating film 16 has been removed, and is deposited on the pixel contact portion 15b of the second electrode layer 15 in the region B. Further, the pixel electrode 17 is formed so that the peripheral edge thereof is positioned on the inner edge of the removed portion of the insulating film 16 (the portion corresponding to the region A).

  According to this manufacturing method, since the surface of the wiring layer 12 and the MIM element is already completely covered with the insulating film 16 when the pixel electrode 17 is formed, the pixel electrode 17 is short-circuited to the wiring layer 12 and the MIM element. Can be formed without danger. As a result, it is possible to form the pixel electrode 17 to the limit of the region where the wiring layer 12 is formed, and the aperture ratio can be improved.

  Here, after the first electrode portion 13 and the insulating layer 14 are formed, the insulating film 16 is formed so that the insulating layer 14 is exposed, and the pixel electrode 17 is connected to the insulating layer 14 by using, for example, ITO. May be formed. In this case, since the second electrode layer and the pixel electrode are integrally formed, the patterning of the second electrode layer is unnecessary, and part of the manufacturing process of the two-terminal active element can be omitted. it can.

  Further, the insulating film 16 may be a light-blocking insulating film. In this case, the black matrix 21BM does not need to be formed on the counter substrate 20 side shown in FIG. In alignment, high alignment accuracy can be eliminated. Furthermore, the structure of the counter substrate can be simplified, and the manufacturing cost can be reduced.

  As shown in FIG. 7, the element substrate 10 and the counter substrate 20 formed in this way are bonded together via a sealing material 41, and a liquid crystal layer 30 is injected by injecting liquid crystal into a liquid crystal sealing region partitioned by the sealing material. The peripheral circuit components of the drive circuits 42a and 42b are mounted to form a liquid crystal display device.

  In the embodiment described above, an example in which the insulating film 16 is formed on the element substrate provided with the MIM element is shown. However, according to the present invention, the wiring layer is formed on the inner surface of the substrate without distinguishing between the element substrate and the counter substrate. If the liquid crystal application electrode is formed, the same effect as described above can be obtained by forming an insulating film on the wiring layer of the substrate.

(Second Embodiment)
Next, an embodiment in which the present invention is applied to a matrix type liquid crystal display device including a TFT (thin film transistor) element as a three-terminal type active element will be described.

  FIG. 8 is a plan view showing a schematic structure of a pixel of a liquid crystal display device having a TFT (thin film transistor) element as the liquid crystal display device according to the present invention, and FIG. 9 is a cross-sectional view taken along line AA in FIG. It is.

First, the pixel portion will be described. In FIG. 8, reference numeral 51a denotes a first polysilicon layer constituting the active layer (source region 50a, channel region 50b, drain region 50c) of the TFT. As shown in FIG. 9, a gate insulating film 62 is formed on the surface by thermal oxidation. Reference numeral 52a denotes a scanning line that becomes a gate electrode of the TFT, 53a denotes a data line that supplies a voltage to be applied to the pixel electrode to the TFT source region 50a disposed so as to intersect the scanning line 52a, and the scanning line 52a is The second polysilicon layer and the data line 53a are each formed of a conductive layer such as an aluminum layer.

  Reference numeral 54 denotes a contact hole for connecting the pixel electrode 56a made of ITO to the TFT drain region 50c of the polysilicon layer 51a, and 55 connects the data line 53a to the TFT source region of the polysilicon layer 51a. This is a contact hole.

  In FIG. 9 showing a cross section along the line AA in FIG. 8, 10 is a substrate such as a glass substrate, a quartz substrate or a silicon substrate, and 62 is formed on the surface of a polysilicon layer 51a which becomes an active layer of the TFT. A gate insulating film such as a silicon oxide film is formed by thermal oxidation or the like. Reference numeral 63 denotes a first interlayer insulating film made of an NSG film (a silicate glass film containing no boron or phosphorus). This is formed by high temperature CVD and low temperature CVD methods.

  In the present embodiment, the insulating layer 64 is formed so as to cover the scanning lines 52a and the data lines 53a, which are wiring layers, including the upper part of the channel region 50b.

  The insulating layer 64 is formed except for the periphery of a contact hole 54 for connection to a pixel electrode 56a described later, and is patterned so that its inner peripheral portion partially overlaps with the outer peripheral portion of the pixel electrode 56a. .

  Also in this embodiment, an inorganic insulating film such as Ta oxide, silicon oxide, silicon nitride, or aluminum oxide formed by sputtering or the like is preferable, and a film thickness that can sufficiently ensure insulation between the lower data line 53a. Is formed. For example, the thickness is preferably about 1000 mm or more for Ta oxide and about 400 mm or more for silicon oxide.

  With this insulating layer 64, even if the pixel electrode 56a is formed close enough to the data line 53a, the short circuit between them can be prevented, thereby preventing the occurrence of display defects.

  In the patterning of the insulating layer 64, when a liquid crystal display device is manufactured by sharing a light-transmitting region of a color filter (not shown) disposed facing the substrate 10 with a mask for patterning. The mask used for the photolithography process can be reduced.

  Also in this embodiment, when the insulating layer 64 is made of a light-shielding material, it is possible to prevent the occurrence of leakage current due to light irradiated on the wiring layer and active layer region of the TFT element, Since the black matrix is formed on the element substrate, the black matrix can be eliminated on the counter substrate, and high alignment accuracy can be eliminated in bonding the element substrate and the counter substrate. Furthermore, the structure of the counter substrate can be simplified, and the manufacturing cost can be reduced.

  Thereafter, a contact hole 54 penetrating the first interlayer insulating film 63 and the gate insulating film 62 is formed, and a pixel electrode 56a made of ITO is formed.

  In this embodiment, the case where ITO is used as the pixel electrode has been described. However, the present invention is not limited to this. For example, a transparent electrode material made of a metal oxide having a high melting point such as SnOx or ZnOx. Can also be used.

  The element-side substrate having such a structure and the counter-side substrate 20 that is disposed opposite to the element-side substrate and on which the counter electrode 23 is formed are bonded together via a seal material 41 as shown in FIG. Reference numeral 25 denotes a light shielding layer made of a chromium layer or the like provided on the counter substrate 20.

  By injecting the liquid crystal 30 into the liquid crystal sealing area partitioned by the sealing material 41 and mounting a circuit board (not shown) for inputting a video signal or the like to be displayed in the pixel area on the input terminal portion 90, a liquid crystal display The device is configured.

  In the present embodiment, the transistors constituting the peripheral circuits 70 and 80 for supplying drive signals to the TFT elements are so-called polysilicon TFTs having a polysilicon layer as an operating layer in the same manner as the pixel drive TFT elements. The transistors constituting the peripheral circuit are simultaneously formed on the substrate by the same process together with the pixel driving TFT elements.

  In the present embodiment, since the insulating layer 64 is formed so as to cover the scanning line serving as the wiring layer, even if conductive foreign matter is mixed between the scanning line and the counter electrode, the insulating layer 64 is interposed between them. Does not short-circuit, preventing the occurrence of defects due to it.

  Although the transmissive liquid crystal display device has been described in the above embodiment of the present invention, the present invention is not limited to this, and a reflective liquid crystal display in which a reflective layer is provided on either the element side substrate or the counter substrate. It is good also as an apparatus.

  The present invention described above provides a structure suitable for preventing display defects caused by a short circuit between the upper and lower electrodes and a method for manufacturing the same by adopting a structure in which a short circuit between two substrates of a liquid crystal display device is unlikely to occur. It can be done.

1 is a schematic enlarged plan view showing a planar structure on an element substrate in an embodiment of a liquid crystal display device according to the present invention. It is an enlarged longitudinal cross-sectional view which shows the cross-section of the same embodiment. It is a schematic process drawing which shows embodiment of the manufacturing method of the liquid crystal display device which concerns on this invention. It is a schematic process drawing which shows embodiment of the manufacturing method of the liquid crystal display device which concerns on this invention. It is a schematic process drawing which shows embodiment of the manufacturing method of the liquid crystal display device which concerns on this invention. It is a schematic process drawing which shows embodiment of the manufacturing method of the liquid crystal display device which concerns on this invention. It is a block diagram which shows schematic structure of the liquid crystal display device which concerns on this invention. 1 is a schematic enlarged plan view showing a planar structure on an element substrate in an embodiment of a liquid crystal display device according to the present invention. It is an enlarged longitudinal cross-sectional view which shows the cross-section of the same embodiment. It is a block diagram which shows schematic structure of the liquid crystal display device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Element substrate, 11 ... Underlayer, 12 ... Wiring layer, 13 ... 1st electrode part, 14 ... Insulating layer, 15 ... 2nd electrode layer, 15a ... Electrode part, 15b ... Pixel contact part, 16 ... Insulating film, 17 ... Pixel electrode, 20 ... Counter substrate, 21C ... Colored layer, 21BM ... Black matrix layer, 22 ... Protective film, 23 ... Counter electrode, 25 ... Light shielding layer, 30 ... Liquid crystal layer, 41 ... Sealing material, 42a, 42b ... Drive circuit, 50a ... source region, 50b ... channel region, 50c drain region, 51a ... TFT active layer, 52a ... scanning line, 53a ... data line, 54/55 ... contact hole, 56a ... pixel electrode, 62 ... gate insulating layer , 63 ... first interlayer insulating film, 64 ... insulating layer, 70 · 80 ... peripheral circuit, 90 ... input terminal

Claims (7)

A liquid crystal layer is sandwiched between two substrates, and the wiring layer, the pixel electrode, and the wiring layer and the pixel electrode are directly or indirectly connected on the inner surface of one of the substrates. An active element and an insulating film,
The insulating film covers the wiring layer and the active element, and is formed so that a peripheral portion of the pixel electrode overlaps an end portion of the insulating film, and is not formed inside the peripheral portion of the pixel electrode. A liquid crystal display device characterized by the above.   2. The active element according to claim 1, wherein the active element includes a connection portion that conducts the active element and the pixel electrode, and the insulating film is disposed to insulate between the wiring layer and the pixel electrode. In addition, the liquid crystal display device includes an opening for ensuring electrical connection between the connection portion and the pixel electrode.   2. The liquid crystal display device according to claim 1, wherein the active element is an MIM element.   2. The liquid crystal display device according to claim 1, wherein the active element is a TFT element.   2. The liquid crystal display device according to claim 1, wherein the insulating film has a light shielding property. A liquid crystal layer is sandwiched between two substrates, and the wiring layer, the pixel electrode, and the wiring layer and the pixel electrode are directly or indirectly connected on the inner surface of one of the substrates. In a manufacturing method of a liquid crystal display device including an active element and an insulating film,
Forming the wiring layer and the active element on the inner surface of one of the substrates;
Forming the insulating film covering the wiring layer and the active element;
The pixel electrode is formed so that a peripheral edge portion of the pixel electrode overlaps an end portion of the insulating film, and the insulating film is not formed inside the peripheral edge portion of the pixel electrode. Device manufacturing method. 7. The liquid crystal display device according to claim 6, wherein the active element is an MIM element.

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