Active matrix substrate, liquid crystal display device including the same, and method for manufacturing active matrix substrate

Abstract

To suppress formation of a hang structure in a reflection suppressing layer.SOLUTION: An active matrix substrate includes: a base substrate 10a; a plurality of TFTs provided on the base substrate 10a; a color filter 16 on each TFT; a first transparent electrode 18a provided above the color filter 16; a second transparent electrode 20a which is provided on the first transparent electrode 18a through a protective film 19a and on which a slit S is formed; and a reflection suppressing layer Ba which is provided in a belt-like shape on the second transparent electrode 20a so as to overlap with an end of the slit S at a boundary portion L between colored layers 16r and 16g having different colors from each other and on which a first metal layer 22a, an intermediate layer 23a, and a second metal layer 24a are stacked in order. An etching stopper layer 21a, made of a material having etching selectivity with respect to the second transparent electrode 20a and the protective film 19a and thinner than the second transparent electrode 20a, is provided between the second transparent electrode 20a and the reflection suppressing layer Ba.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an active matrix substrate, a liquid crystal display device including the same, and a method for manufacturing the active matrix substrate. [Background technology]

[0002] In recent years, liquid crystal display devices have often adopted a color filter on array (hereinafter also referred to as "COA") structure, in which color filters are provided on an active matrix substrate (array substrate), eliminating the need for alignment with the opposing substrate.

[0003] For example, Patent Document 1 discloses a liquid crystal display device in which a pixel electrode and a common electrode are provided on a substrate having a COA structure, and which utilizes a FFS (Fringe Field Switching) mode, which is one of the in-plane switching driving methods.

[0004] In a liquid crystal display device equipped with an active matrix substrate having a COA structure in which pixel electrodes (first transparent electrodes), an inorganic protective film made of an inorganic insulating film, and a common electrode (second transparent electrode) having notches for liquid crystal alignment are sequentially arranged, a reflection-reducing layer including a metal layer disposed between each colored layer of a color filter may be formed on the second transparent electrode. In this case, when the reflection-reducing layer is formed by dry etching, the inorganic protective film exposed from the second transparent electrode is etched, and there is a risk of a step being formed by the edge of the inorganic protective film. This step can easily cause light leakage due to alignment disturbance in the liquid crystal layer, thereby degrading the optical characteristics of the liquid crystal display device.

[0005] Therefore, Patent Document 2 proposes a method for manufacturing an active matrix substrate, in which a first transparent conductive film formed on the upper side of a color filter is patterned to form a first transparent electrode (pixel electrode), an inorganic protective film is formed on the first transparent electrode, a second transparent conductive film is formed on the inorganic protective film, an anti-reflection layer in which a metal layer and an inorganic insulating layer are laminated is formed on the second transparent conductive film, and the second transparent conductive film is patterned to form a second transparent electrode (common electrode), thereby suppressing etching of the inorganic protective film exposed from the second transparent electrode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-116821 [Patent Document 2] JP 2023-167272 A (Fig. 50) Summary of the Invention [Problem to be solved by the invention]

[0007] Furthermore, as in Patent Document 2, in IPS-driven liquid crystal display devices equipped with an active matrix substrate having a COA structure in which slits for liquid crystal alignment are formed in the common electrode, for example, when ultra-high-resolution pixel sizes of 1000 to 1200 ppi (pixels per inch) or more are achieved for head-mounted display applications, the edges of the slits formed in the common electrode often overlap the anti-reflection layer disposed between the colored layers of the color filter. In this case, when the second transparent conductive film that forms the common electrode is patterned after the anti-reflection layer is formed, the second transparent conductive film below the anti-reflection layer is etched to the sides (toward the substrate surface) by wet etching, which can result in the anti-reflection layer forming a hanging structure like a canopy in the area where the slits are formed. Since no alignment film is formed in the hanging structure of the anti-reflection layer, alignment disturbances in the liquid crystal layer occur, resulting in reduced contrast due to light leakage and other factors, degrading display quality.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to suppress the formation of a hanging structure in an antireflection layer. [Means for solving the problem]

[0009] In order to achieve the above object, the active matrix substrate of the present invention comprises: a base substrate; a plurality of thin film transistors provided on the base substrate corresponding to a plurality of sub-pixels; color filters provided on each of the thin film transistors, with colored layers of predetermined colors arranged corresponding to each of the sub-pixels; a first transparent electrode provided on top of the color filters; a second transparent electrode provided on the first transparent electrode via a protective film made of an inorganic insulating film, the second transparent electrode having a strip-shaped slit formed therein; and an anti-reflection layer provided in a strip shape on the second transparent electrode at a boundary portion between the colored layers of different colors so as to overlap with ends of the slits, the anti-reflection layer comprising a first metal layer, an intermediate layer, and a second metal layer laminated in this order; and an etching stopper layer formed between the second transparent electrode and the anti-reflection layer, the etching stopper layer being made of a material having etching selectivity with respect to the second transparent electrode and the protective film and being thinner than the second transparent electrode.

[0010] A liquid crystal display device according to the present invention is characterized by comprising the above-mentioned active matrix substrate, a counter substrate provided opposite to the active matrix substrate, and a liquid crystal layer provided between the active matrix substrate and the counter substrate.

[0011] Furthermore, a method for manufacturing an active matrix substrate according to the present invention includes a thin film transistor forming step of forming a plurality of thin film transistors on a base substrate corresponding to a plurality of sub-pixels; a color filter forming step of forming color filters, each having a colored layer of a predetermined color arranged on each of the thin film transistors corresponding to each of the sub-pixels; a first transparent electrode forming step of forming a first transparent conductive film on top of the color filters and then patterning the first transparent conductive film to form a first transparent electrode; a protective film forming step of forming a protective film made of an inorganic insulating film on the first transparent electrode; a second transparent electrode forming step of forming a second transparent conductive film on the protective film and then patterning the second transparent conductive film to form a second transparent electrode having strip-shaped slits; and an etching step of etching the etching stopper film exposed from the antireflection layer, wherein in the antireflection layer forming step, the etching stopper film is made of a material that has etching selectivity with respect to the second transparent conductive film and the inorganic insulating film, and is formed thinner than the second transparent conductive film. [Effects of the Invention]

[0012] According to the present invention, it is possible to suppress the formation of a hanging structure in the antireflection layer. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a plan view of an active matrix substrate constituting a liquid crystal display device according to a first embodiment of the present invention. [Figure 2] 2 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line II-II in FIG. [Figure 3]3 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line III-III in FIG. [Figure 4] 4 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line IV-IV in FIG. [Figure 5] 1A to 1C are first cross-sectional views illustrating a part of a manufacturing process for an active matrix substrate constituting a liquid crystal display device according to a first embodiment of the present invention. [Figure 6] 5A to 5C are second cross-sectional views showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 7] 7 is a third cross-sectional view following FIG. 6 showing part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 8] 8 is a fourth cross-sectional view following FIG. 7 showing part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 9] 8 showing a fifth cross-sectional view following FIG. 8 illustrating a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 10] 9 showing a sixth cross-sectional view following FIG. 9 illustrating a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 11] 10 showing a seventh cross-sectional view following FIG. 10 illustrating a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. [Figure 12] 11 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 13] 12 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 14]13 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 15] 14 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 16] 12 is a twelfth cross-sectional view following FIG. 15 showing part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 17] 16 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 18] 17 showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the first embodiment of the present invention. FIG. [Figure 19] FIG. 10 is a plan view of an active matrix substrate constituting a liquid crystal display device according to a second embodiment of the present invention. [Figure 20] 20 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line XX-XX in FIG. 19. [Figure 21] 20 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line XXI-XXI in FIG. 19. [Figure 22] 20 is a cross-sectional view of the active matrix substrate and a liquid crystal display device including the same, taken along line XXII-XXII in FIG. 19. [Figure 23] 10A to 10C are first cross-sectional views illustrating a part of a manufacturing process for an active matrix substrate constituting a liquid crystal display device according to a second embodiment of the present invention. [Figure 24] 24 is a second cross-sectional view following FIG. 23 showing part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the second embodiment of the present invention. [Figure 25] 25 is a third cross-sectional view following FIG. 24 showing part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the second embodiment of the present invention. [Figure 26] 25A to 25C are fourth cross-sectional views showing a part of the manufacturing process of the active matrix substrate constituting the liquid crystal display device according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0015] First Embodiment 1 to 18 show a first embodiment of an active matrix substrate, a liquid crystal display device including the same, and a method for manufacturing the active matrix substrate according to the present invention. Fig. 1 is a plan view of an active matrix substrate 30a constituting a liquid crystal display device 50a of this embodiment. Figs. 2, 3, and 4 are cross-sectional views of the active matrix substrate 30a and the liquid crystal display device 50a including the same, taken along lines II-II, III-III, and IV-IV in Fig. 1.

[0016] As shown in FIGS. 2 to 4, the liquid crystal display device 50a includes an active matrix substrate 30a having a COA structure, a counter substrate 40 disposed opposite the active matrix substrate 30a, and a liquid crystal layer 45 disposed between the active matrix substrate 30a and the counter substrate 40. The liquid crystal display device 50a also includes a display region for displaying images, in which a plurality of subpixels P (see FIG. 1) are arranged in a matrix. As shown in FIGS. 2 to 4, the display region includes a subpixel P having a red layer 16r for displaying red gradations, a subpixel P having a green layer 16g for displaying green gradations, and a subpixel P having a blue layer (not shown) for displaying blue gradations, arranged adjacent to each other. In the display region, three adjacent subpixels P for displaying red, green, and blue gradations constitute one pixel.

[0017] As shown in Figures 2 to 4, the active matrix substrate 30a includes a base substrate 10a such as a glass substrate, a plurality of thin film transistors (hereinafter also referred to as "TFTs") 5 provided on the base substrate 10a corresponding to a plurality of sub-pixels P, a color filter 16 provided on each TFT 5, an organic protective film 17 provided on the color filter 16, a plurality of pixel electrodes 18a each provided as a first transparent electrode on the organic protective film 17, an inorganic protective film 19a provided on each pixel electrode 18a, a common electrode 20a provided as a second transparent electrode on the inorganic protective film 19a, a surface protective film 27 provided on the common electrode 20a, and an alignment film 29 provided on the surface protective film 27. As shown in FIG. 1, the active matrix substrate 30a is provided on a base substrate 10a with a plurality of gate lines 11 arranged in the display region so as to extend parallel to one another in the Y direction in the figure, and a plurality of source lines 14 arranged so as to extend parallel to one another in the X direction in the figure and to intersect with each gate line 11 via a gate insulating film 12 (see FIGS. 2 to 4).

[0018] 2, the TFT 5 includes a gate electrode 11a provided on a base substrate 10a, a gate insulating film 12 provided to cover the gate electrode 11a, a semiconductor layer 13 provided on the gate insulating film 12 in an island shape to overlap the gate electrode 11a, and a source electrode 14a and a drain electrode 14b provided on the semiconductor layer 13 to be spaced apart from each other. The TFT 5 is provided at each intersection of the gate line 11 and the source line 14, i.e., for each sub-pixel P. Here, the gate electrode 11a is a wide portion of the gate line 11 as shown in FIG. 1. The semiconductor layer 13 includes, for example, an intrinsic amorphous silicon layer provided on the gate insulating film 12 side, and a pair of n-type ... + 1, the source electrode 14a is a portion that protrudes in an L-shape to the side of the source line 14, and is located on one n-side of the semiconductor layer 13. +The drain electrode 14b is provided in contact with the amorphous silicon layer 13. + 2, the semiconductor layer 13 is provided in contact with the amorphous silicon layer and is electrically connected to the pixel electrode 18a via a contact hole H formed in the color filter 16 and the organic protective film 17. Note that, although the present embodiment illustrates the semiconductor layer 13 including an intrinsic amorphous silicon layer, the semiconductor layer 13 may be composed of, for example, a polysilicon film of LTPS (low temperature polysilicon) or an In-Ga-Zn-O based oxide semiconductor film.

[0019] The color filter 16 is provided so that colored layers of predetermined colors are arranged corresponding to the respective sub-pixels P. Specifically, as shown in FIGS. 2 to 4, the color filter 16 includes a red layer 16r provided as a colored layer in the sub-pixels P for displaying red gradations, a green layer 16g provided as a colored layer in the sub-pixels P for displaying green gradations, and a blue layer (not shown) provided as a colored layer in the sub-pixels P for displaying blue gradations. An interlayer insulating film 15 is provided between the TFT 5 and the color filter 16. The gate insulating film 12, the interlayer insulating film 15, the inorganic protective film 19a, and the surface protective film 25 are each formed of a single layer or a multilayer film of an inorganic insulating film such as silicon nitride, silicon oxide, or silicon oxynitride.

[0020] The organic protective film 17 is made of a transparent organic resin material such as an acrylic resin.

[0021] 1 to 4, the pixel electrode 18a is provided in a rectangular shape on the organic protective film 17. Here, as shown in Fig. 1, the plurality of pixel electrodes 18a are provided in a matrix corresponding to the plurality of sub-pixels P. The pixel electrode 18a, together with the common electrode 20a and the inorganic protective film 19a provided between the pixel electrode 18a and the common electrode 20a, constitutes an auxiliary capacitance for each sub-pixel P.

[0022] As shown in FIG. 1, the common electrode 20a is provided in common to a plurality of subpixels P. Furthermore, as shown in FIGS. 1 and 4, the common electrode 20a is provided with strip-shaped slits S penetrating the common electrode 23 for aligning the liquid crystal layer 45. Here, as shown in FIG. 1, both ends of the slits S are provided so as to overlap with antireflection layers Ba (described later). Furthermore, as shown in FIGS. 1 and 2, the common electrode 20a is provided with rectangular openings M penetrating the common electrode 20a so as to overlap with the contact holes H. Furthermore, within the openings M of the common electrode 20a, a transparent conductive layer 20b, which is formed in the same layer and made of the same material as the common electrode 20a, is provided in a concave shape spaced apart from the common electrode 20a so as to overlap the bottom and side surfaces of the contact holes H. As shown in FIG. 2, a resin filling layer 26 is provided between the transparent conductive layer 20b and the surface protective film 27. Furthermore, as shown in FIGS. 1, 3 and 4, an antireflection layer Ba is provided on the common electrode 20a so as to overlap a boundary portion L between colored layers of different colors.

[0023] As shown in Fig. 1, the reflection-suppressing layer Ba is provided in a strip shape across the entire display area so as to overlap each source line 14. As shown in Figs. 3 and 4, the reflection-suppressing layer Ba includes a first metal layer 22a, an intermediate layer 23a, and a second metal layer 24a, which are stacked in this order on the common electrode 20a with an etching stopper layer 21a interposed therebetween. The reflection-suppressing layer Ba is configured such that light incident from the liquid crystal layer 45 side is reflected by the second metal layer 24a, and light that is not reflected by the second metal layer 24a but passes through the second metal layer 24a is reflected by the first metal layer 22a. The light reflected by the second metal layer 24a and the light reflected by the first metal layer 23a cancel each other out, thereby suppressing reflection of light incident from the liquid crystal layer 45 side. The first metal layer 22a is formed of a first metal film 22 (see Fig. 14) made of, for example, a tungsten film, a molybdenum film, or a molybdenum-tungsten alloy having a thickness of approximately 60 nm or more. The intermediate layer 23a is made of an inorganic insulating film such as a silicon nitride film having a refractive index of about 1.8 to 2.1 and a thickness of about 40 to 90 nm, or a transparent conductive film such as an ITO (Indium Tin Oxide) film or an IZO (Indium Zinc Oxide) film (see FIG. 14). The second metal layer 24a is made of a third metal film 24 (see FIG. 14) such as a tungsten film or a molybdenum film having a thickness of about 2 to 15 nm. The etching stopper layer 21a is made of an etching stopper film 21 (see FIG. 14) having a thickness of about 3 to 30 nm, and is thinner than the common electrode 20a, and is made of an oxide semiconductor film made of a material having etching selectivity with respect to the common electrode 20a and the inorganic protective film 19a. Examples of the oxide semiconductor film that constitutes the etching stopper layer 21a include In-Ga-Zn-O-based, In-Sn-Zn-O-based, and In-Ti-Zn-Sn-O-based oxide semiconductor films.

[0024] The alignment film 29 and an alignment film 31 (described later) are made of, for example, polyimide resin whose surface has been subjected to rubbing treatment.

[0025] As shown in FIGS. 2 to 4, the counter substrate 40 includes a base substrate 10b such as a glass substrate, and an alignment film 31 provided on the base substrate 10b.

[0026] The liquid crystal layer 45 is made of, for example, a nematic liquid crystal material having electro-optical properties, and is sealed between the active matrix substrate 30a and the counter substrate 40 by a frame-shaped sealant that bonds the active matrix substrate 30a and the counter substrate 40 to each other in a frame region around the display area.

[0027] The liquid crystal display device 50a having the above configuration applies a predetermined voltage to the liquid crystal layer 45 and auxiliary capacitance disposed between each pixel electrode 18a and the common electrode 20a, and changes the orientation state of the liquid crystal layer 45 due to an electric field generated in a direction along the substrate surface, i.e., in the horizontal direction, thereby adjusting the transmittance of light passing through the panel of each sub-pixel P and displaying an image.

[0028] Next, a method for manufacturing the liquid crystal display device 50a of this embodiment will be described, focusing on a method for manufacturing the active matrix substrate 30a. Figures 5 to 18 are first to fourteenth cross-sectional views sequentially illustrating a portion of the manufacturing process for the active matrix substrate 30a. In each of the cross-sectional views of Figures 5 to 18, the right, center, and left sides of the broken lines correspond to the cross-sectional views of Figures 2, 3, and 4, respectively. The manufacturing process for the active matrix substrate 30a includes a TFT formation step, a color filter formation step, a first transparent electrode formation step, a protective film formation step, a second transparent electrode formation step, an antireflection layer formation step, and an etching step.

[0029] First, an aluminum film (about 300 nm thick) and a molybdenum niobium film (about 50 nm thick) are sequentially formed on a base substrate 10a such as a glass substrate by, for example, a sputtering method to form a metal laminate film, and then the metal laminate film is subjected to photolithography, etching, and resist stripping and cleaning to form gate lines 11 including gate electrodes 11a.

[0030] Subsequently, on the surface of the substrate on which the gate lines 11 are formed, an inorganic insulating film (about 350 nm thick) such as a silicon nitride film or a silicon oxide film, an intrinsic amorphous silicon film (about 120 nm thick), and a phosphorus-doped n + After forming an amorphous silicon film (thickness: about 30 nm) in order, an intrinsic amorphous silicon film and an n + The stacked film of amorphous silicon films is subjected to photolithography, etching, and resist stripping and cleaning to form a gate insulating film 12 and a semiconductor formation layer.

[0031] Thereafter, a titanium film (about 30 nm thick), an aluminum film (about 300 nm thick), and a titanium film (about 50 nm thick) are sequentially formed by, for example, sputtering on the substrate surface on which the gate insulating film 12 and the semiconductor formation layer have been formed, to form a metal laminate film, and then the metal laminate film is subjected to photolithography, etching, and resist stripping and cleaning to form a source line 14 including a source electrode 14a and a drain electrode 14b.

[0032] Furthermore, the source electrode 14a and the drain electrode 14b are used as a mask to form the n-type semiconductor layer. + The amorphous silicon film is removed by etching to form the semiconductor layer 13 and the TFT 5 including the semiconductor layer 13 (TFT formation step).

[0033] Next, an inorganic insulating film (about 750 nm thick) such as a silicon nitride film or a silicon oxide film is formed on the substrate surface on which the TFTs 5 are formed, for example, by plasma CVD to form an interlayer insulating film 15. Then, an acrylic photosensitive resin (about 1.6 μm thick) colored red, green, or blue is applied, for example, by spin coating or slit coating, and the applied photosensitive resin is partially exposed to light and then developed for patterning to form a colored layer of the selected color (for example, red layer 16r). Similar steps are then repeated for the other two colors to form colored layers of the other two colors (for example, green layer 16g and blue layer), thereby forming a color filter 16 having contact holes H, as shown in FIG. 5 (color filter formation step).

[0034] Thereafter, an acrylic photosensitive resin (about 2.0 μm thick) is applied to the surface of the substrate on which the color filter 16 has been formed, for example, by spin coating or slit coating, and the applied photosensitive resin is partially exposed to light and then developed for patterning, thereby forming an organic protective film 17 having contact holes H, as shown in FIG. 6.

[0035] Furthermore, the interlayer insulating film 15 exposed from the contact hole H is etched to form the contact hole H in the interlayer insulating film 15 as shown in FIG.

[0036] Next, a first transparent conductive film 18 of an ITO film or an IZO film having a thickness of about 70 nm is formed on the surface of the substrate on which the contact hole H has been formed in the interlayer insulating film 15, for example, by sputtering, as shown in FIG. 8, and then the first transparent conductive film 18 is subjected to photolithography, etching, and resist stripping and cleaning to form a pixel electrode 18a as shown in FIG. 9 (first transparent electrode formation process).

[0037] Thereafter, an inorganic insulating film 19 such as a silicon nitride film having a thickness of about 100 nm is formed on the surface of the substrate on which the pixel electrode 18a is formed, for example, by plasma CVD, as shown in FIG. 10, and then the inorganic insulating film 19 is subjected to photolithography, etching, and resist stripping and cleaning to form an inorganic protective film 19a as shown in FIG. 11 (protective film forming process).

[0038] Furthermore, a second transparent conductive film 20 made of an ITO film having a thickness of approximately 70 nm is formed on the surface of the substrate on which the inorganic protective film 19a has been formed, for example, by a sputtering method, and then a resist Ra is formed on the surface of the second transparent conductive film 20 by photolithography, as shown in Figure 12.

[0039] Next, the second transparent conductive film 20 exposed from the resist Ra is subjected to wet etching using, for example, an oxalic acid solution, to form the pixel electrode 20a and the transparent conductive layer 20b as shown in FIG. 13 (second transparent electrode formation process).

[0040] Thereafter, the resist Ra is removed and washed, and then the pixel electrode 20a and the transparent conductive layer 20b are crystallized by annealing at 220° C. for about 50 minutes, for example.

[0041] Furthermore, on the substrate surface on which the pixel electrode 20a and the transparent conductive layer 20b are formed, for example, by sputtering an etching stopper film 21 made of a semiconductor film such as InGaZnO4 and having a thickness of about 3 nm to 30 nm, and a first metal film 22 made of a tungsten film having a thickness of about 60 nm. Then, by plasma CVD, an intermediate film 23 made of a silicon nitride film having a thickness of about 60 nm is formed. Then, by sputtering, a second metal film 24 made of a tungsten film having a thickness of about 6 nm is formed. Then, as shown in FIG. 14, a resist Rb is formed on the surface of the second metal film 24 by photolithography.

[0042] Next, the first metal film 22, the intermediate film 23, and the second metal film 24 exposed from the resist Rb are dry-etched using, for example, a fluorine-based gas to form an antireflection layer Ba in which the first metal layer 22a, the intermediate layer 23a, and the second metal layer 24a are laminated in this order, as shown in Fig. 15 (antireflection layer forming step). Here, in the antireflection layer forming step, the first metal layer 22a, the intermediate layer 23a, and the second metal layer 24 are formed all at once by dry etching or the like, so that the antireflection layer Ba in which the first metal layer 22a, the intermediate layer 23a, and the second metal layer 24a are laminated in this order can be formed with high accuracy.

[0043] Thereafter, the etching stopper film 21 exposed from the resist Rb and the antireflection layer Ba is wet-etched using, for example, an oxalic acid solution to form an etching stopper layer 21a, and then the resist Rb is stripped and washed (etching step) as shown in Fig. 16. Note that, although the present embodiment illustrates a manufacturing method in which the etching stopper film 21 is wet-etched before the resist Rb is stripped, the etching stopper film 21 may be wet-etched after the resist Rb is stripped.

[0044] Furthermore, an acrylic photosensitive resin (about 2.5 μm thick) is applied to the substrate surface on which the etching stopper layer 21a has been formed, for example, by spin coating or slit coating, and the applied photosensitive resin is partially exposed to light and then developed for patterning, thereby forming a filling resin layer 26 as shown in FIG. 17.

[0045] Thereafter, an inorganic insulating film (about 30 nm thick) such as a silicon nitride film is formed on the substrate surface on which the filled resin layer 26 has been formed, for example, by plasma CVD, thereby forming a surface protection film 27 as shown in FIG.

[0046] Finally, a polyimide resin film is applied by, for example, a printing method to the entire substrate on which the surface protection film 27 has been formed, and then the resin film is subjected to baking and rubbing treatments to form an alignment film 29.

[0047] In this manner, the active matrix substrate 30a can be manufactured.

[0048] Furthermore, the active matrix substrate 30a and the counter substrate 40 manufactured as described above are bonded together via a frame-shaped sealant, and a liquid crystal material is sealed between the active matrix substrate 30a and the counter substrate 40 to form a liquid crystal layer 45, thereby manufacturing the liquid crystal display device 50.

[0049] As described above, in the active matrix substrate 30a, the liquid crystal display device 50a including the active matrix substrate 30a, and the method for manufacturing the active matrix substrate 30a according to this embodiment, in the antireflection layer formation step, the first metal film 22, the intermediate film 23, and the second metal film 24 exposed from the resist Rb are dry-etched using, for example, a fluorine-based gas to form the antireflection layer Ba, in which the first metal layer 22a, the intermediate layer 23a, and the second metal layer 24a are stacked in this order. Then, in the etching step, the etching stopper film 21 exposed from the resist Rb and the antireflection layer Ba is wet-etched using, for example, an oxalic acid solution. Here, the etching stopper film 21 is made of a material that has etching selectivity with respect to the second transparent electrode 20a and the inorganic protective film 19a, i.e., an oxide semiconductor film. Therefore, when the etching stopper film 21 is etched using an oxalic acid solution, the surface of the inorganic protective film 19a below the etching stopper film 21 is less likely to be etched. Moreover, because the etching stopper film 21 is thinner than the second transparent electrode 20a, the etching time for the etching stopper film 21 is shorter, and etching of the surface of the inorganic protective film 19a can be further suppressed. This suppresses etching of the surface of the inorganic protective film 19a when etching the etching stopper film 21, thereby suppressing the formation of a hanging structure in the antireflection layer Ba. Furthermore, suppressing the formation of a hanging structure in the antireflection layer Ba suppresses alignment disturbance in the liquid crystal layer due to the absence of the alignment film 29, thereby suppressing a decrease in contrast and improving the display quality of the liquid crystal display device 50a.

[0050] Here, if the etching stopper film 21 were thick, it would take a long time to etch the etching stopper film 21, and in addition, there is a risk that part of the etching stopper film 21 in the region where the antireflection layer Ba is laminated would be side-etched, resulting in a hanging structure of the antireflection layer Ba. However, in this embodiment, the thickness of the etching stopper film 21 is thinner than the second transparent electrode 20a, and therefore side-etching of the etching stopper film 21 in the region where the antireflection layer Ba is laminated can be suppressed compared to when the etching stopper film 21 is thicker than the second transparent electrode 20a, and the antireflection layer Ba can be further suppressed from forming a hanging structure.

[0051] Second Embodiment 19 to 26 show a second embodiment of an active matrix substrate, a liquid crystal display device including the same, and a method for manufacturing the active matrix substrate according to the present invention. Here, FIG. 19 is a plan view of an active matrix substrate 30b constituting a liquid crystal display device 50b of this embodiment. Also, FIGS. 20, 21, and 22 are cross-sectional views of the active matrix substrate 30b and a liquid crystal display device 50 including the same, taken along lines XX-XX, XXI-XXI, and XXII-XXII in FIG. 19. In the following embodiments, the same parts as those in FIGS. 1 to 18 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0052] In the first embodiment described above, a liquid crystal display device 50a is illustrated as including an active matrix substrate 30a having a reflection suppression layer Ba with a three-layer laminated structure, whereas in the present embodiment, a liquid crystal display device 50b is illustrated as including an active matrix substrate 30b having a reflection suppression layer Bb with a four-layer laminated structure.

[0053] 20 to 22, the liquid crystal display device 50b includes an active matrix substrate 30b having a COA structure, a counter substrate 40 provided opposite the active matrix substrate 30b, and a liquid crystal layer 45 provided between the active matrix substrate 30b and the counter substrate 40. In the liquid crystal display device 50b, a display region for displaying an image has a plurality of sub-pixels P (see FIG. 19) arranged in a matrix, similar to the liquid crystal display device 50a of the first embodiment.

[0054] As shown in Figures 20 to 22, the active matrix substrate 30b includes a base substrate 10a such as a glass substrate, a plurality of TFTs 5 arranged on the base substrate 10a corresponding to a plurality of sub-pixels P, a color filter 16 arranged on each TFT 5, an organic protective film 17 arranged on the color filter 16, a plurality of pixel electrodes 18a arranged on the organic protective film 17, an inorganic protective film 19a arranged on each pixel electrode 18a, a common electrode 20a arranged on the inorganic protective film 19a, a surface protective film 27 arranged on the common electrode 20a, and an alignment film 29 arranged on the surface protective film 27. As shown in FIG. 19, the active matrix substrate 30b, like the active matrix substrate 30a of the first embodiment, includes a base substrate 10a on which, in the display region, are provided a plurality of gate lines 11 extending parallel to one another in the Y direction in the figure, and a plurality of source lines 14 extending parallel to one another in the X direction in the figure so as to intersect with the gate lines 11 via gate insulating films 12 (see FIGS. 20 to 22).

[0055] As shown in FIGS. 19, 21 and 22, an antireflection layer Bb is provided on the common electrode 20a so as to overlap a boundary portion L between colored layers of different colors.

[0056] 19, the antireflection layer Bb is provided in a strip shape across the entire display area so as to overlap each source line 14. 21 and 22, the antireflection layer Bb includes a first metal layer 22a, an intermediate layer 23a, a second metal layer 24a, and a surface layer 25a, which are stacked in this order on the common electrode 20a with an etching stopper layer 21a interposed therebetween, and is configured such that light incident from the liquid crystal layer 45 side is reflected by the second metal layer 24a, and light that is not reflected by the second metal layer 24a but passes through the second metal layer 24a is reflected by the first metal layer 22a, and the light reflected by the second metal layer 24a and the light reflected by the first metal layer 23a cancel each other out, thereby suppressing reflection of light incident from the liquid crystal layer 45 side. Here, the surface layer 25a is composed of a surface film 25 (see Figure 23) which has a refractive index of about 1.8 to 2.1 and is an inorganic insulating film such as a silicon nitride film with a thickness of about 10 nm to 30 nm, or a transparent conductive film such as an ITO (Indium Tin Oxide) film or an IZO (Indium Zinc Oxide) film.

[0057] The liquid crystal layer 45 is sealed between the active matrix substrate 30b and the counter substrate 40 by a frame-shaped sealant that bonds the active matrix substrate 30b and the counter substrate 40 to each other in the frame region.

[0058] The liquid crystal display device 50b having the above configuration, like the liquid crystal display device 50a of the first embodiment, applies a predetermined voltage to the liquid crystal layer 45 and auxiliary capacitance arranged between each pixel electrode 18a and the common electrode 20a, and changes the orientation state of the liquid crystal layer 45 due to the electric field generated in the horizontal direction, thereby adjusting the transmittance of light passing through the panel of each sub-pixel P and displaying an image.

[0059] Next, a method for manufacturing the liquid crystal display device 50b of this embodiment will be described, focusing on a method for manufacturing the active matrix substrate 30b. Figures 23 to 26 are first to fourth cross-sectional views successively illustrating part of the manufacturing process for the active matrix substrate 30b. In each of the cross-sectional views of Figures 23 to 26, the right, center, and left sides of the broken line correspond to the cross-sectional views of Figures 20, 21, and 22, respectively.

[0060] First, in the first embodiment, on the substrate surface on which the pixel electrode 20a and the transparent conductive layer 20b are formed, for example, by sputtering an etching stopper film 21 made of a semiconductor film such as InGaZnO4 having a thickness of about 3 nm to 30 nm, and a first metal film 22 made of a tungsten film having a thickness of about 60 nm. Then, by plasma CVD, an intermediate film 23 made of a silicon nitride film having a thickness of about 60 nm is formed. Then, by sputtering, a second metal film 24 made of a tungsten film having a thickness of about 6 nm is formed. Then, by plasma CVD, a surface film 25 made of a silicon nitride film having a thickness of about 20 nm is formed. Then, as shown in FIG. 23, a resist Rc is formed on the surface of the surface film 25 by photolithography.

[0061] Next, the first metal film 22, the intermediate film 23, the second metal film 24 and the surface film 25 exposed from the resist Rc are dry-etched using, for example, a fluorine-based gas, thereby forming a reflection-suppressing layer Bb in which the first metal layer 22a, the intermediate layer 23a, the second metal layer 24a and the surface layer 25a are stacked in this order, as shown in Figure 24 (reflection-suppressing layer formation process).

[0062] Thereafter, the etching stopper film 21 exposed from the resist Rc and the antireflection layer Bb is subjected to wet etching using, for example, an oxalic acid aqueous solution to form an etching stopper layer 21a, and then the resist Rc is peeled off and washed as shown in FIG. 25 (etching process).

[0063] Furthermore, an acrylic photosensitive resin (about 2.5 μm thick) is applied to the substrate surface on which the etching stopper layer 21a has been formed, for example, by spin coating or slit coating, and the applied photosensitive resin is partially exposed to light and then developed for patterning, thereby forming a filling resin layer 26 as shown in FIG. 26.

[0064] Finally, a polyimide resin film is applied by, for example, a printing method to the substrate surface on which the filled resin layer 26 has been formed, and then the resin film is subjected to baking and rubbing treatments to form an alignment film 29.

[0065] In this manner, the active matrix substrate 30b can be manufactured.

[0066] Furthermore, the active matrix substrate 30b manufactured as described above and the counter substrate 40 are bonded together via a frame-shaped sealant, and a liquid crystal material is sealed between the active matrix substrate 30b and the counter substrate 40 to form a liquid crystal layer 45, thereby manufacturing the liquid crystal display device 50b.

[0067] As described above, in the active matrix substrate 30b, the liquid crystal display device 50b including the active matrix substrate 30b, and the method for manufacturing the active matrix substrate 30b according to this embodiment, in the antireflection layer formation step, the first metal film 22, the intermediate film 23, the second metal film 24, and the surface film 25 exposed from the resist Rc are dry-etched using, for example, a fluorine-based gas to form an antireflection layer Bb including the first metal layer 22a, the intermediate layer 23a, the second metal layer 24a, and the surface layer 25a stacked in this order. Then, in the etching step, the etching stopper film 21 exposed from the resist Rc and the antireflection layer Bb is wet-etched using, for example, an oxalic acid solution. Here, the etching stopper film 21 is made of a material that has etching selectivity with respect to the second transparent electrode 20a and the inorganic protective film 19a, i.e., a transparent conductive film other than the ITO film that constitutes the second transparent electrode 20a. Therefore, when the etching stopper film 21 is etched using an oxalic acid solution, the surface of the inorganic protective film 19a below the etching stopper film 21 is less likely to be etched. Moreover, because the etching stopper film 21 is thinner than the second transparent electrode 20a, the etching time for the etching stopper film 21 is shorter, and etching of the surface of the inorganic protective film 19a can be further suppressed. This suppresses etching of the surface of the inorganic protective film 19a when etching the etching stopper film 21, thereby suppressing the formation of a hanging structure in the antireflection layer Bb. Furthermore, suppressing the formation of a hanging structure in the antireflection layer Bb suppresses alignment disturbance in the liquid crystal layer due to the absence of the alignment film 29, thereby suppressing a decrease in contrast and improving the display quality of the liquid crystal display device 50b.

[0068] Third Embodiment In the above-described first and second embodiments, the active matrix substrates 30a and 30b are provided with an etching stopper film 21 (etching stopper layer 21a) made of an oxide semiconductor film. However, the etching stopper film 21 (etching stopper layer 21a) has etching selectivity with respect to the second transparent electrode 20a and the inorganic protective film 19a, is formed thinner than the second transparent electrode 20a, and may be made of a transparent conductive film such as an IZO film or a tin oxide film.

[0069] Other Embodiments In the above-described embodiments, a liquid crystal display device 50a (50b) is exemplified, which includes an active matrix substrate 30a (30b) in which a common electrode 20a is provided above a pixel electrode 18a and a slit S is formed in the common electrode 20a. However, the present invention can also be applied to an active matrix substrate in which a pixel electrode is provided above a common electrode and a slit is formed in the pixel electrode, and a liquid crystal display device including the active matrix substrate.

[0070] Furthermore, in each of the above embodiments, a liquid crystal display device including an active matrix substrate in which an electrode of a TFT connected to a pixel electrode serves as a drain electrode has been exemplified. However, the present invention can also be applied to a liquid crystal display device including an active matrix substrate in which an electrode of a TFT connected to a pixel electrode serves as a source electrode. [Industrial Applicability]

[0071] As described above, the present invention is useful for a liquid crystal display device of the in-plane switching driving type that includes an active matrix substrate having a color filter on-array structure. [Explanation of symbols]

[0072] Ba,Bb reflection suppression layer P subpixel S slit 5 TFT (Thin Film Transistor) 10a Base board 16 Color Filters 16g green layer (colored layer) 16r Red layer (colored layer) 18a Pixel electrode (first transparent electrode) 20a Common electrode (second transparent electrode) 21 Etching stopper film 21a Etching stopper layer 22 First metal film 22a 1st metal layer 23 Interlayer 23a middle class 24 Second metal film 24a 2nd metal layer 30a, 30b Active matrix substrate 40 Opposing substrate 45 Liquid crystal layer 50a,50b LCD display device

Claims

1. A base substrate; a plurality of thin film transistors provided on the base substrate corresponding to a plurality of sub-pixels; a color filter provided on each of the thin film transistors, the color filter including a colored layer of a predetermined color arranged corresponding to each of the sub-pixels; a first transparent electrode provided above the color filter; a second transparent electrode provided on the first transparent electrode via a protective film made of an inorganic insulating film, the second transparent electrode having strip-shaped slits; a reflection-suppressing layer provided in a strip shape on the second transparent electrode at a boundary portion of the colored layers having different colors so as to overlap an end portion of the slit, the reflection-suppressing layer being formed by sequentially stacking a first metal layer, an intermediate layer, and a second metal layer; an etching stopper layer made of a material having etching selectivity with respect to the second transparent electrode and the protective film, and thinner than the second transparent electrode, is provided between the second transparent electrode and the antireflection layer.

2. 2. The active matrix substrate according to claim 1, The active matrix substrate is characterized in that the etching stopper layer has a film thickness of 3 nm to 30 nm.

3. 3. The active matrix substrate according to claim 1, The active matrix substrate is characterized in that the etching stopper layer is made of an oxide semiconductor film.

4. 3. The active matrix substrate according to claim 1, The active matrix substrate is characterized in that the etching stopper layer is made of a transparent conductive film.

5. 3. The active matrix substrate according to claim 1, the first transparent electrode is a pixel electrode provided corresponding to each of the sub-pixels, The active matrix substrate, wherein the second transparent electrode is a common electrode provided in common to the plurality of sub-pixels.

6. An active matrix substrate according to claim 1 or 2; an opposing substrate provided opposite the active matrix substrate; a liquid crystal layer provided between the active matrix substrate and the counter substrate;

7. a thin film transistor forming step of forming a plurality of thin film transistors on a base substrate corresponding to a plurality of sub-pixels; a color filter forming step of forming a color filter on each of the thin film transistors, the color filter having a colored layer of a predetermined color disposed corresponding to each of the sub-pixels; a first transparent electrode forming step of forming a first transparent conductive film on the upper side of the color filter and then patterning the first transparent conductive film to form a first transparent electrode; a protective film forming step of forming a protective film made of an inorganic insulating film on the first transparent electrode; a second transparent electrode forming step of forming a second transparent conductive film on the protective film and then patterning the second transparent conductive film to form a second transparent electrode having strip-shaped slits; a reflection-suppressing layer forming step of sequentially depositing an etching stopper film, a first metal film, an intermediate film, and a second metal film so as to cover the second transparent electrode, and then patterning the first metal film, the intermediate film, and the second metal film to form a first metal layer, an intermediate layer, and a second metal layer, respectively, and forming a reflection-suppressing layer in which the first metal layer, the intermediate layer, and the second metal layer are sequentially stacked in a strip shape so as to overlap the boundary portions of the colored layers of different colors and the end portions of the slits; an etching step of etching the etching stopper film exposed from the antireflection layer, a second transparent conductive film formed on the first insulating film and a second transparent conductive film formed on the second insulating film; a second transparent conductive film formed on the first insulating film and a second transparent conductive film formed on the second insulating film;

8. 8. The method for manufacturing an active matrix substrate according to claim 7, the etching stopper film is composed of an oxide semiconductor film or a transparent conductive film, The method for manufacturing an active matrix substrate, wherein the etching step includes etching the etching stopper film with an aqueous solution of oxalic acid.

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