Liquid crystal display panel having reflection electrodes improved in smooth surface morphology and process for fabrication thereof

The present invention relates to a liquid crystal display device and a method for manufacturing the same, in particular, a reflective liquid crystal display device having a reflective electrode or a reflective or transmissive (hereinafter referred to as semi-transmissive) liquid crystal display device and a transmissive liquid crystal display device. Regarding the manufacturing method.

[0002] In recent years, small liquid crystal display devices for mobile phones and PDAs have become widespread. As the liquid crystal display device used for these, a reflective or semi-transmissive type liquid crystal display device is used because of the demand for light weight, thinness, and low power consumption.

[0003] FIG. 24 shows a cross-sectional view of a general reflective liquid crystal display device shown in Japanese Patent Application Laid-Open No. 2000-258787.

[0004] In this reflective liquid crystal display device, a thin film transistor (TFT), which is a switching element, is formed on an insulating substrate (TFT substrate) 110 made of quartz glass, non-alkali glass, or the like. First, a gate electrode 111 made of a refractory metal such as chromium (Cr) and molybdenum (Mo), a gate insulating film 112, and an active layer 113 made of a polycrystalline silicon film are sequentially formed on the insulating substrate 110. The active layer 113 is provided with a channel 113c above the gate electrode 111 and a source 113s and a drain 113d formed by ion implantation on both sides of the channel 113c with the stopper insulating film 114 provided on the channel 113c as a mask. Has been done.

[0005] Next, SiO is applied to the entire surface of the gate insulating film 112, the active layer 113, and the stopper insulating film 114.₂Membrane, SiNx Membrane and SiO₂The interlayer insulating film 115 laminated in the order of the films is formed, and the contact holes provided corresponding to the drain 113d are filled with a metal such as aluminum (Al) to form the drain electrode 116. Further, a flattening insulating film 117 made of, for example, an organic resin and flattening the surface is formed on the entire surface. Then, a contact hole is formed at a position corresponding to the source 113s of the flattening insulating film 117, and the reflective electrode 119 which is composed of Al connected to the source 113s through the contact hole and also serves as a source electrode is a flattening insulating film. Form on 117. Next, an alignment film 120 made of an organic resin such as polyimide is formed on the reflective electrode 119.

[0006] Further, the opposing substrate 130, which faces the TFT substrate 110 and is made of an insulating substrate, has a black matrix having red (R), green (G), blue (B) colors and a light-shielding function on the TFT substrate side. A color filter 131 provided with 132, a protective film 133 made of resin formed on the color filter 131, a counter electrode 134 formed on the entire surface thereof, and an alignment film 135 are provided, and a retardation plate is provided on the opposite surface thereof. 143 and the polarizing plate 144 are arranged. Then, the periphery of the TFT substrate 110 and the opposing substrate 130 is adhered with a sealing material (not shown), and the twisted nematic (TN) liquid crystal 121 is sandwiched in the space formed by the sealing material (not shown).

[0007] Here, the reflective electrode 119 is made of an alloy of Al and neodymium (Nd). By setting the Nd concentration to 1 wt% or more, hillock does not occur and the surface becomes flat, and even if the film is formed at a substrate temperature of about 200 ° C, it is formed with pure Al formed at room temperature (unheated). Similarly, it is stated that a reflective electrode having a high reflectance can be obtained.

[0008] On the other hand, Japanese Patent Application Laid-Open No. 5-80327 describes a method for manufacturing a diffuse reflector for liquid crystal display, in which a reflective film is formed on an organic film while being heated to 100 ° C to 250 ° C. Wrinkles are generated in the organic film due to the difference in thermal expansion rate between the organic film and the reflective film, and the Al film or platinum (Pt) film constituting the reflective film is grain-grown at the time of film formation to make the reflective film fine. It is stated that it forms irregularities and improves the scattering reflection characteristics.

[0009] Further, in Japanese Patent Application Laid-Open No. 2000-111906, as a method for manufacturing an electro-optical device in which a reflective layer having unevenness is formed, unevenness is formed under the reflective layer, and a reflective layer is formed on the unevenness. The metal film to be used is formed under the conditions of 80 to 250 angstrom / min and the film formation temperature is 100 ° C to 300 ° C, and after the metal film is formed, heat treatment is performed to make the metal film surface have an average pitch of 1 to 2 μm and a depth of 1 to 2 μm. It is stated that it forms fine irregularities of 0.2 μm and improves the scattering reflection characteristics.

[0010] However, on a metal film serving as a reflective electrode of a reflective liquid crystal display device or a transflective liquid crystal display device, Al-as described in Japanese Patent Application Laid-Open No. 2000-258787 Even if an Nd alloy is used, according to the experiment of the present inventor, when the film is formed at a relatively high temperature of about 200 ° C, the color of the liquid crystal display device turns yellow depending on the alignment film material (the appearance is yellowish). It turned out that there was a problem (described later).

[0011] On the other hand, when the metal film to be the reflective electrode is formed without heating or at a low temperature of less than 70 ° C, the reflective liquid crystal in which the switching element and the reflective electrode are connected via the interlayer insulating film of the coating system. In the case of a display device or a semi-transmissive liquid crystal display device, there is a problem that the contact resistance between the metal film serving as the reflective electrode and the lower metal film used as the electrode of the switching element becomes high and the writing to the pixel electrode deteriorates. .. Further, when the metal film to be the reflective electrode is formed without heating, the metal film is altered by the gas emitted from the organic interlayer insulating film due to the temperature rise of the substrate due to the heat of condensation during the film formation, and the reflectance is lowered. There is a problem that it decreases. This phenomenon is particularly remarkable when an alloy mainly composed of Al or Al is used for the metal film serving as the reflective electrode, and in this case, there is a problem that Al becomes cloudy (white cloudy and the reflectance decreases).

[0012] An object of the present invention is a reflective liquid crystal display device or a semi-transmissive liquid crystal display that can prevent the color of the liquid crystal display device from turning yellow, can obtain high reflectance, and has no writing defects. To provide a device.

[Means for Solving the Problems] The liquid crystal display device of the present invention is a liquid crystal having a bus wiring, a switching element connected to the bus wiring, and a reflective electrode connected to the switching element on a substrate. In the display device, the reflective electrode<u style="single">Depends on the crystal structure</u>The surface unevenness is characterized by an average pitch of 1 μm or less.

[0014] Further, the liquid crystal display device of the present invention is characterized in that the reflectance of the reflective electrode in the wavelength range of 200 nm to 400 nm is 90% or more of the reflectance at a wavelength of 400 nm in the liquid crystal display device.

[0015] Further, the liquid crystal display device of the present invention is characterized in that the reflective electrode is made of an alloy of Al and Nd, and the concentration of Nd is 0.5 wt% or more and 10 wt% or less.

[0016] Further, the liquid crystal display device of the present invention is characterized in that, in the liquid crystal display device, the light transmittance of the alignment film formed on the reflective electrode in the wavelength range of 300 nm to 600 nm is 95% or more. ..

[0017] Further, the method for manufacturing a liquid crystal display device of the present invention is to manufacture a liquid crystal display device having a bus wiring, a switching element connected to the bus wiring, and a reflective electrode connected to the switching element on a substrate. The method is characterized in that the substrate temperature at the time of film formation of the reflective electrode is 170 ° C. or less.

[0018] Further, in the method for manufacturing a liquid crystal display device of the present invention, in the method for manufacturing a liquid crystal display device, the reflective electrode is formed on an interlayer insulating film of a coating system, and the substrate temperature at the time of film formation is 70 ° C. It is characterized by being C or more and 170 ° C or less.

[0019] Further, the method for manufacturing a liquid crystal display device of the present invention is characterized in that the substrate is heated at least before the film formation of the reflective electrode.

[0020] As described above, fine surface irregularities are formed by using an alloy of Al and Nd for the reflective electrode of the reflective liquid crystal display device or the semitransmissive liquid crystal display device and performing film formation at a temperature of 170 ° C. or lower. It is possible to form a reflective electrode having a fine and less uneven morphology with an average pitch of 1 μm or less, preferably 0.6 μm or less, thereby reducing light absorption in the ultraviolet light region with a wavelength of 200 nm to 400 nm and the color of the liquid crystal display device. It is possible to prevent yellowing of the taste. The morphology referred to here refers to the surface morphology of the metal film constituting the reflective electrode due to the crystal structure, and refers to the fine irregularities on the surface of the reflective electrode. Therefore, the reflective electrode is different from the unevenness reflected by the unevenness of the base film. (The same applies hereinafter) At the same time, especially in the case of a reflective liquid crystal display device or a semi-transmissive liquid crystal display device in which a reflective electrode is formed on an interlayer insulating film of a coating system, an alloy of Al and Nd is used for the reflective electrode, and the substrate is prepared in advance. By heating to a temperature of 70 ° C to 170 ° C to form a film, the influence of gas emitted from the interlayer insulating film of the coating system is eliminated, white turbidity of the reflective electrode is prevented, high reflectance is achieved, and reflection is achieved. It is possible to prevent an increase in contact resistance between the metal film that serves as the electrode and the lower metal film that serves as the electrode of the switching element.

BEST MODE FOR CARRYING OUT THE INVENTION [Embodiments of the Invention] A first embodiment of the present invention will be described with reference to the drawings. The first embodiment is an example of a reflective display device in which a reflective electrode is formed on an organic interlayer insulating film having irregularities. FIG. 1 is a conceptual diagram showing a configuration of a thin film transistor array substrate (TFT substrate) used in the liquid crystal display device according to the first embodiment of the present invention. Further, FIG. 2 is a panel plan view of the liquid crystal display device according to the first embodiment of the present invention, and FIG. 3 corresponds to a cross section of the AA line, CC line and one pixel portion of FIG. 2 (the BB line portion of FIG. 4 to be described later). ) Is a panel sectional view.

As shown in FIGS. 1 and 3, in the TFT substrate 10, a plurality of scanning lines 11 and a plurality of signal lines 12 are arranged substantially orthogonally on the transparent insulating substrate 10a, and are arranged in the vicinity of the intersection thereof. A thin film transistor (TFT) 14 which is a switching element connected to these is provided, and these are arranged in a matrix. Further, a plurality of common wirings 13 are arranged in parallel with the scanning line, and a holding capacitance is formed between the common wiring 13 and the pixel electrode (reflection electrode) 31 connected to the TFT 14. The reflective electrode 31 for applying a voltage to the liquid crystal is separated from the scanning line 11, the signal line 12, and the TFT 14 via an organic interlayer insulating film 32, and is provided on the scanning line 11, the signal line 12, and the TFT 14. Unevenness is formed on the organic interlayer insulating film 32, and unevenness (different from the surface morphological unevenness of the reflective electrode) is also formed on the reflective electrode 31 to reflect the shape.

Further, a scanning line terminal 15 for inputting an address signal is provided at the end of the scanning line 11, and a signal line terminal 16 for inputting a data signal is provided at the end of the signal line 12. Further, the common wiring 13 is usually bound to each other by a common wiring binding wire 17 on both sides of the TFT substrate, a common wiring terminal 18 is provided at the end thereof, and the same potential as that of the counter electrode 33 on the counter substrate 20 is given. Here, it is conceptually shown that the scanning line terminal 15 and the signal line terminal 16 occupy one side of each of the TFT board 10, but since the liquid crystal display device of the present invention is for small portable use, both of them are used for the TFT board 10. It is provided together on one side. (See FIG. 2) On the other hand, as shown in FIGS. 2 and 3, the facing substrate 20 has a color filter 21 and a counter electrode for applying a voltage to the liquid crystal corresponding to the display area on the transparent insulating substrate 20a. 33 is provided, and a black matrix 22 is provided in the peripheral portion. Since the reflective electrode 31 also serves as a light-shielding layer, a black matrix is not provided in the display area. The black matrix 22 is for improving the appearance of the liquid crystal display device (making black more black and making the appearance clearer).

An alignment film 34 for aligning liquid crystal molecules is provided on the facing surfaces of the TFT substrate 10 and the facing substrate 20, and both substrates are superposed at predetermined intervals via the sealing material 23 and the in-plane spacer 35. The liquid crystal 36 is sandwiched inside. The space of the sealing material into which the liquid crystal 36 is injected is sealed with the sealing material 24. Further, a 1/4 wave plate 37 and a polarizing plate 38 are provided on the surface of the facing substrate 20 opposite to the surface facing the TFT substrate 10, and serves as a liquid crystal display panel. Although not shown in FIG. 2, after that, an IC chip, which is a drive circuit, is mounted on the scanning line terminal 15 and the signal line terminal 16 by COG (chip on glass) to complete the liquid crystal display device.

As shown in FIG. 3, the incident light 39 incident from the back surface side of the facing substrate 20 passes through the facing substrate 20 and the liquid crystal 36 layer, and is transmitted on the reflective electrode 31 having a predetermined unevenness on the surface of the TFT substrate 10. It is reflected, passes through the liquid crystal 36 layer and the facing substrate 20 again, and is emitted to the outside as emitted light 40.

Next, the configuration of the TFT substrate of the liquid crystal display device according to the first embodiment of the present invention and the manufacturing method thereof will be described in detail with reference to FIGS. 4 to 8. FIG. 4 is a plan view showing the configuration of one pixel portion of the TFT substrate of the liquid crystal display device of the present embodiment, and FIGS. 5, 6, and 7 are process cross-sectional views corresponding to the BB line portion of FIG. Here, an example in which a TFT having an inverted staggered structure is used as the switching element is shown, and a diagram of the outermost peripheral pixel portion on the leftmost side of FIG. 1 is shown. Further, FIG. 8 shows a process cross section in the short side direction of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 (the terminals are arranged in an elongated rectangular shape when viewed in a plane, which means the short side direction). It is a figure.

As shown in FIGS. 4 and 7, one pixel portion of the TFT substrate of the liquid crystal display device of the present embodiment includes scanning lines 11 and signal lines 12 orthogonal to each other and a pixel region surrounded by these wires. The reflective electrode 31 and the reflective electrode 31 which reflect the light incident on each pixel region and apply a voltage to the liquid crystal 36 sandwiched between the TFT 14 which is a switching element provided and the opposite substrate 20. A first insulating film 51 and a second insulating film 52 for forming predetermined irregularities are included, the gate electrode 41 is on the scanning line 11, the drain electrode 42 is on the signal line 12, and the source electrode 43 is on the reflecting electrode 31. Each is connected to. Since the reflective electrode 31 also functions as a pixel electrode for applying a voltage to the liquid crystal, it needs to be separated for each pixel, and is separated for each pixel on the scanning line 11 and the signal line 12.

[0028] Further, in the TFT side substrate 10, a gate electrode 41 is formed in the TFT region on the transparent insulating substrate 10a, and the semiconductor layer 44 (a-Si layer 44a and n) is formed on the gate electrode 41 via the gate insulating film 53. ⁺Type a-Si layer 44b) is formed, n ⁺A drain electrode 42 and a source electrode 43 are formed on the mold a-Si layer 44b. Then, in each pixel region, a first insulating film 51 for forming predetermined irregularities on the reflective electrode 31 is irregularly arranged, and a step of the first insulating film 51 is gently formed on the first insulating film 51. A second insulating film 52 is formed.

[0029] Here, the first insulating film 51 is irregularly formed inside the display area in order to exhibit uniform reflected optical characteristics over the entire display area, but is outside the display area (FIG. 4). Since the region on the left side of the above is the region where the terminal electrodes and the like are provided, the first insulating film 51 is not formed. On the other hand, the second insulating film 52 is continuously formed inside the display area except for the contact hole 45, and has a slight spread outside the display area so as to completely cover the first insulating film 51. It is formed. Then, a reflective electrode 31 is formed on the passivation film 54, the first insulating film 51, and the second insulating film 52 that protect the TFT 14, and the second insulating film 52 and the passivation film 54 on the source electrode 43, respectively. It is connected to the source electrode 43 at the provided contact holes 45 and 55.

[0030] The surface of the reflective electrode 31 reflects the unevenness of the first insulating film 51 and the second insulating film 52, and the configuration of the uneven inclination angle of the surface of the reflective electrode 31 determines the optical characteristics of the reflected light. Become. Therefore, the angle of inclination of the unevenness is designed so as to obtain the desired catoptric characteristics. At this time, the unevenness may be composed of two or more different values for any one of the convex pitch, the concave pitch, the convex height, and the concave depth.

[0031] Further, the lower limit of the film thickness of the first insulating film 51 is defined by the above-mentioned reflected optical characteristics and is also limited from the viewpoint of parasitic capacitance. That is, if the first insulating film 51 is formed thinly, the reflection direction of the incident light cannot be changed significantly, and the distance between the reflecting electrode 31, the scanning line 11, and the signal line 12 becomes narrow. The parasitic capacitance between the wiring and the wiring becomes large, causing signal delay and making it impossible to transmit the correct signal, and the electric field between the signal line and the pixel becomes stronger, which affects the nearby liquid crystal and affects the liquid crystal molecules. The display quality will be impaired, such as disturbance in the orientation direction and slow response. Therefore, the first insulating film 51 is formed with a film thickness of about 1 to 3 μm. On the other hand, since the second insulating film 52 is provided to moderately alleviate the unevenness of the first insulating film 51 and make the surface a gentle curved surface, the above effect can be exhibited if it is too thin. However, if it is too thick, the unevenness of the first insulating film 51 will be offset and flattened. Therefore, the film thickness of the second insulating film 52 is preferably in the range of about 0.3 to 1.5 μm.

Next, a method of manufacturing the TFT substrate having the above configuration will be described. As shown in FIGS. 5 (a) to 7 and 8, the manufacturing process can be roughly divided into (1) film formation and patterning of the metal film of the gate electrode 41, and (2) gate insulating film 53, a. -Si layer 44a, n⁺Film formation and patterning of mold a-Si layer 44b, (3) Film formation and patterning of metal film of drain electrode 42 and source electrode 43, (4) Film formation and patterning of passion film 54, (5) Terminal Film formation and patterning of the transparent conductive film of the part connection electrode 63, (6) Film formation of the first insulating film 51, patterning and surface shape conversion processing, (7) Film formation and pattern of the second insulating film 52 Ning, (8) film formation of the metal film of the reflective electrode 31, and patterning consist of a total of 8 steps.

[0033] First, a metal film such as Cr having a thickness of 100 nm to 300 nm is formed on a transparent insulating substrate 10a made of non-alkali glass having a thickness of 0.5 mm by sputtering, and a known photolithography technique and etching technique are applied. It is used to form a terminal metal film 61 of a gate electrode 41, a scanning line 11 (not shown), a common wiring 13 (not shown), a scanning line terminal 15, a signal line terminal 16, and a common wiring terminal 18. The wiring material is not limited to Cr, but has low resistance and forms a thin film, such as a wiring film having a laminated structure in which a barrier metal such as Cr, Mo, or titanium (Ti) is formed on Mo, Al, or an Al alloy. Any material may be used as long as it can be easily patterned by photolithography technology. (Fig. 5 (a), Fig. 8 (a)) Next, a gate insulating film 53 made of silicon nitride (SiNx) having a thickness of 300 nm to 500 nm was formed by plasma CVD, and subsequently on the gate insulating film 53 by plasma CVD. Undoped amorphous silicon (a-Si) with a thickness of 150 nm to 300 nm and n with a thickness of 30 nm to 50 nm.⁺Mold-doped amorphous silicon (n) ⁺Mold a-Si) is formed and patterned through a photolithography process to form a-Si layers 44a and n. ⁺A semiconductor layer 44 composed of a type a-Si layer 44b is formed. The a-Si layer 44a is the active layer of TFT14, and n⁺The mold a-Si layer 44b is for ensuring ohmic contact between the drain electrode 42 and the source electrode 43 and the a-Si layer 44a. (Fig. 5 (b), Fig. 8 (b)) Next, a metal film such as Cr with a thickness of 100 nm to 300 nm is formed by sputtering, patterned through a photolithography process, and drain electrode 42, source electrode 43, and signal line. Form 12. After that, dry etching is performed using the drain electrode 42 and the source electrode 43 as masks, and n between the drain electrode 42 and the source electrode 43.⁺Remove mold a-Si layer 44b. This is n between the drain electrode 42 and the source electrode 43.⁺This is to prevent a direct current from flowing through the mold a-Si layer 13b. Here, too, the wiring material is not limited to Cr, but has low resistance, such as a wiring film having a laminated structure in which barrier metals such as Cr, Mo, and Ti are formed above and below Mo, Al, or Al alloy, and thin film formation and photolithography. Any material that can be easily patterned by a lithography technique may be used. (Fig. 5 (c), Fig. 8 (b)) Next, silicon nitride having a thickness of 100 nm to 300 nm was formed by plasma CVD to form a passivation film 54 (Fig. 8 (c)), and on the source electrode 43. The passivation film 54 and the passivation film 54 and the gate insulating film 53 on the terminal metal film 61 of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 are patterned to form the contact hole 55 and the terminal, respectively. The part contact hole 62 is opened. At this time, although not shown, the passivation film 54 and the gate insulating film 53 on the end of the common wiring 13 and the passivation film 54 and the gate insulating film 53 on the end of the terminal metal film 61 of the signal line terminal 16 , The passivation film 54 on the end of the signal line 12 on the signal line terminal 16 side is simultaneously patterned and opened. The passivation film 54 is for preventing impurities such as ions from diffusing into the a-Si layer 44a and causing the TFT 14 to malfunction. (Fig. 5 (d), Fig. 8 (d)) Next, a transparent conductive film such as ITO having a thickness of 40 nm to 100 nm is formed by sputtering, and patterned through a photolitho process, and is placed on the terminal metal film 61 of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. A connection electrode 63 (not shown) for connecting the connection electrode 63, the common wiring binding wire 17 (not shown) on the end of the common wiring 13, and the terminal metal film 61 of the signal line terminal 16 and the signal line 12 (not shown). To form. At this time, the pattern of the transparent conductive film is not formed in the display area. Therefore, when a metal film such as Mo, Al, or an Al alloy in which Mo is laminated on top of each other is used for the source electrode 43, it is necessary to perform ITO patterning with an etching solution such as oxalic acid that does not etch Mo. When a metal film such as Cr or Ti laminated on top of Cr or Al or Al alloy is used for the source electrode 43, a royal water-based or ferric chloride-based etching solution may be used. Here, the reason why the pattern of the transparent conductive film is not formed in the display region is to avoid the risk of peeling of the transparent conductive film due to the battery action between ITO and Al described later in 55 parts of the contact hole. Further, forming the connection electrode 63 with a transparent conductive film on the terminal portion metal film 61 of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 ensures the connection reliability at the terminal portion at the time of COG mounting. To do. (Fig. 5 (d), Fig. 8 (e)) Next, for example, a photosensitive novolak resin with a thickness of 1 to 3 μm is applied, and the inside of the display area is irregularly patterned with an alkaline developer through a photolithography process. The first insulating film 51 is formed. As the first insulating film 51, either a non-photosensitive resin or a photosensitive resin can be used, and when a non-photosensitive resin is used, the forming step is as follows: 1) Coating of the first insulating film 51, (2) Coating resist coating of the first insulating film 51, (3) Exposure, (4) Development, (5) Etching of the first insulating film 51, ( 6) It consists of each process of resist stripping. On the other hand, when a photosensitive resin is used, the forming process is as follows: (1) Coating of the first insulating film 51 on the substrate. , (2) Exposure and (3) Development, and the steps of coating and peeling the patterning resist can be omitted. (FIGS. 6 (a) and 8 (e)) Next, the first insulating film 51 is subjected to a predetermined surface shape conversion process to form a gentle convex shape. In this method, the surface of the first insulating film 51 after pattern formation is melted and converted into a smooth shape by performing a heat treatment at a temperature of about 80 ° C to 200 ° C. The surface shape conversion treatment is not limited to heat treatment, and for example, a melting treatment with a chemical such as NMP (N-methyl-2-pyrrolidone) may be used. After the surface shape conversion treatment, firing is performed again at a temperature of about 200 ° C to 250 ° C. (Fig. 6 (b), Fig. 8 (e)) Next, for example, a photosensitive novolak resin with a thickness of 0.3 to 1.5 μm is applied, patterned with an alkaline developer through a photolithography process, and 200 ° C to 250 ° C. It is fired at a temperature of about 2 to form a second insulating film 52, and a pixel contact hole 45 is formed corresponding to the contact hole 55 opened in the passivation film 54 on the source electrode 43. (FIGS. 6 (c) and 8 (e)) Here, an example is shown in which the first insulating film 51 and the second insulating film 52 are made of a novolac-based organic resin material. For example, JSR's PC403 or the like can be used. However, these materials do not have to be of the same type and may be of different types. Further, not only the novolak resin but also a combination of an inorganic resin and an organic resin such as an acrylic resin and a polyimide resin, a silicon nitride film and an acrylic resin, a silicon oxide film and a polyimide resin, or vice versa is used. However, the desired unevenness can be formed. 5 μm is applied, patterned with an alkaline developer through a photolithography process, and fired at a temperature of about 200 ° C to 250 ° C to form a second insulating film 52 and on the passivation film 54 on the source electrode 43. The pixel portion contact hole 45 is formed corresponding to the opened contact hole 55. (FIGS. 6 (c) and 8 (e)) Here, an example is shown in which the first insulating film 51 and the second insulating film 52 are made of a novolac-based organic resin material. For example, JSR's PC403 or the like can be used. However, these materials do not have to be of the same type and may be of different types. Further, not only the novolak resin but also a combination of an inorganic resin and an organic resin such as an acrylic resin and a polyimide resin, a silicon nitride film and an acrylic resin, a silicon oxide film and a polyimide resin, or vice versa is used. However, the desired unevenness can be formed.

[0034] Although the method of forming the first insulating film 51 and the second insulating film 52 by using the photolithography method has been described here, a printing method may be used. In this case, the manufacturing process can be simplified. Further, it can be formed by using a wet treatment such as a liquid phase growth method or a dry treatment such as a plasma polymerization method. That is, the coating-based insulating film (interlayer insulating film) referred to in the present application is a general term for insulating films that generate gas.

Next, a Mo film having a thickness of 50 nm to 200 nm and an Al-Nd alloy film having a thickness of 100 nm to 300 nm are sequentially formed by sputtering, and patterned through a photolithography process to form a highly reflective reflective electrode 31. To do. This patterning is performed by wet etching with a mixed acid consisting of phosphoric acid, acetic acid and nitric acid heated to 40 ° C to 60 ° C. At this time, the reflective electrode 31 is connected to the source electrode 43 of each pixel and is removed between the respective pixel regions (on the scanning line 11 and on the signal line 12) in order to function as a pixel electrode. At the same time, the outside of the display area is also removed. Therefore, no Mo and Al-Nd alloy film remains on each of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. Here, the Mo film is a barrier metal between the transparent conductive film (ITO film), which is the connection electrode 63 of the terminal portion, and the Al-Nd alloy film, and is generated between ITO and Al by the developer penetrating during the development of the photolitho process. It has a role of preventing the transparent conductive film from peeling off due to the battery action of the above, and a sufficient film thickness is required to prevent this battery action. (FIGS. 6 (d) and 8 (e)) Next, a method for forming a metal film to be a reflective electrode 31 will be described in detail. In the sputtering apparatus, the TFT substrate 10 in the states shown in FIGS. 6 (c) and 8 (e) is first conveyed to the heating chamber, heated to a temperature of 70 ° C to 170 ° C, and then heated to a temperature of 70 ° C to 170 ° C for about 1 to 2 minutes. And sufficiently release the water contained in the second insulating film. Next, the TFT substrate 10 is transported to the film forming chamber, and the Mo film and the Al-Nd alloy film are rapidly formed continuously. Here, it is desirable that the heating chamber and the film forming chamber are independently evacuated in different chambers. This is because the gas emitted from the coating system insulating films (first and second insulating films) of the TFT substrate 10 adversely affects the film quality of the Mo film and Al-Nd alloy film and the contact resistance between the underlying metal film. This is to prevent giving. When heating and film formation are performed in the same chamber, it is important to take a long heating time of about 2 to 5 minutes and exhaust the chamber sufficiently during substrate heating (heat retention). As a result, Al- with high reflectance without cloudiness

[0036] In the above, it is not always necessary to heat the substrate at the time of forming the Mo film and the substrate at the time of forming the Al-Nd alloy film at the same temperature. The substrate heating temperature at the time of forming the Mo film may be controlled to be high, such as 120 ° C at the time of forming the -Nd alloy film. This is because if the substrate heating temperature at the time of forming the Mo film is low, the crystallinity of the Mo film deteriorates, which adversely affects the film quality of the Al-Nd alloy film and the etching property of the Al-Nd alloy / Mo film.

[0037] Further, it is desirable that the Nd concentration of the Al-Nd alloy film is 0.5 wt% or more. As a result, hillock in a heat treatment step such as firing of an alignment film in a subsequent step can be suppressed, and a highly reflective reflective electrode 31 can be obtained. Furthermore, by setting the substrate temperature at the time of film formation to 170 ° C or less, the surface morphology (fine irregularities) of the reflective electrode 31 can be controlled to an average pitch of 1 μm or less, and the reflectance in the wavelength range of 200 nm to 400 nm can be controlled in the visible light region. It can be 90% or more of the reflectance of. As a result, the reflective electrode 31 without yellowing can be obtained regardless of the type of the alignment film (described later). On the other hand, the Nd concentration is preferably 10 wt% or less. As a result, an Al-Nd alloy film having a high reflectance can be obtained (described later).

[0038] Here, an example in which an Al-Nd alloy having high reflectance and good consistency with the TFT process is used as the material of the reflective electrode 31 is shown, but the present invention is not limited to this, and reflection is not limited to this. Any metal having a high reflectance may be used, and for example, other Al alloys such as Al-Ti alloys and Al-Mo alloys, or silver (Ag) or a silver alloy having a higher reflectance may be used.

[0039] Next, an alignment film 34 having a thickness of 50 nm to 100 nm is formed on the TFT substrate 10 by printing, and fired at a temperature of about 200 ° C to 230 ° C to perform an alignment treatment. On the other hand, a counter electrode 33 made of a transparent conductive film such as ITO is formed on the transparent insulating substrate 20a corresponding to the display region, and a black matrix 22 is formed on the peripheral portion of the counter electrode 33. Similarly, an alignment film 34 having a thickness of 50 nm to 100 nm is formed on the 20 by printing and fired at a temperature of about 200 ° C to 230 ° C to perform an alignment treatment. Here, it is desirable to use an alignment film having a light transmittance of 95% or more in the wavelength range of 300 nm to 600 nm. As a result, the reflective electrode 31 without yellowing can be obtained (described later).

[0040] Each of these TFT substrates 10 and the opposing substrate 20 is interposed via a sealing material 23 (not shown) made of an epoxy resin adhesive and an in-plane spacer 35 (not shown) made of plastic particles or the like. The film surfaces of the films are overlapped at predetermined intervals so as to face each other. After that, the liquid crystal 36 is injected between the TFT substrate 10 and the facing substrate 20, and the space (injection port) of the sealing material 23 (not shown) into which the liquid crystal 36 is injected is a sealing material made of a UV curable acrylate resin. Seal at 24 (not shown). Finally, the 1/4 wave plate 37 and the polarizing plate 38 are attached to the surface of the facing substrate 20 opposite to the film surface to complete the liquid crystal display panel. (Fig. 7) After that, although not shown, an IC chip to be a drive circuit is COG mounted on 15 scanning line terminals, 16 signal line terminals, and 18 common wiring terminals to complete a liquid crystal display device. As described above, a reflective liquid crystal display device having high reflectance, no yellowing, and no problem of writing defects can be obtained.

Next, a second embodiment of the present invention will be described with reference to the drawings. The second embodiment is also an example of a reflective display device in which a reflective electrode is formed on an organic interlayer insulating film having irregularities. The purpose of this embodiment is to simplify the manufacturing process of the TFT substrate, and the structure and manufacturing method of other parts are exactly the same as those of the first embodiment described above.

The configuration of the TFT substrate of the liquid crystal display device according to the second embodiment of the present invention and the manufacturing method thereof will be described in detail with reference to FIGS. 4, 5, 8 to 10. FIG. 4 is a plan view showing the configuration of one pixel portion of the TFT substrate of the liquid crystal display device of the present embodiment, and FIGS. 5, 9 to 10 are process cross-sectional views corresponding to the BB line portion of FIG. Here, an example in which a TFT having an inverted staggered structure is used as the switching element is shown, and a diagram of the outermost peripheral pixel portion on the leftmost side of FIG. 1 is shown. Further, FIG. 8 is a process cross-sectional view in the short side direction of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18.

[0043] In the present embodiment, as shown in FIG. 10B, in order to form predetermined unevenness on the reflective electrode 31, the insulating film 71 is integrally formed and irregularly and gently arranged. There is. That is, the roles of the first insulating film and the second insulating film in the first embodiment are held in the insulating film 71 of the present embodiment.

As shown in FIGS. 5 (a) to 5 (c), 9 (a) to 10 (b), and FIG. 8, the manufacturing process of the TFT substrate having the above configuration can be roughly classified into (1). ) Formation and patterning of the metal film of the gate electrode 41, (2) Gate insulating film 53, a-Si layer 44a, n ⁺Film formation and patterning of mold a-Si layer 44b, (3) Film formation and patterning of metal film of drain electrode 42 and source electrode 43, (4) Film formation and patterning of passion film 54, (5) Terminal All of (6) film formation of insulating film 71, patterning and surface shape conversion processing, (7) film formation of metal film of reflective electrode 31 and patterning It consists of 7 steps.

[0045] The steps (1) to (5) are exactly the same as those in the first embodiment, and the TFT 14 and the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 are formed on the transparent insulating substrate 10a. To do. (Fig. 9 (a), Fig. 8 (e)) Next, for example, the insulating film 71 made of photosensitive novolak resin has a thickness of 2 to 4. Apply 5 μm. Then, the insulating film 71 is exposed and developed to form irregularities. In the present embodiment, a transmission region that transmits the exposure light as a photomask, a semitransmissive region that attenuates and transmits the exposure light by a predetermined amount, and the like. It is characterized by using a halftone mask in which a light-shielding region is formed. That is, the light-shielding region corresponds to the region 72a forming the convex portion, the semi-transmissive region corresponds to the region 72b forming the concave portion, and the transmissive region corresponds to the region 72c in which the insulating film 71 is completely removed. Align to and expose. (Fig. 9 (b)) Next, development is performed, and the insulating film 71 remains as it is in the light-shielding region, and the insulating film 71 is etched to some extent in the semi-transmissive region, so that predetermined irregularities are formed on the insulating film 71. .. In addition, next to the region where the insulating film 71 is completely removed (transmission region 72c), a region where a certain amount of film remains (semi-transmissive region 72b) is always arranged so that the insulating film 71 does not cause a steep step. I am trying to do it. In this way, the area where the insulating film 71 is completely exposed by exposure for a long time or exposed to strong light using a halftone mask during exposure and the insulating film 71 is completely removed by development is short. The first insulating film 51 and the second insulating film of the first embodiment are created by creating a region in which the insulating film 71 is left to some extent by time exposure or weak light, and a region in which the film is not removed without being exposed to light. The 52 forming steps can be performed in one step. (Fig. 9 (c)) Next, the surface shape conversion process is performed in the same manner as in the first actual form. By performing heat treatment at a temperature of about 80 ° C to 200 ° C, the surface of the insulating film 71 after pattern formation is melted and converted into a smooth shape. The surface shape conversion treatment is not limited to the heat treatment, and for example, a melting treatment with a chemical may be used. After the surface shape conversion treatment, firing is performed again at a temperature of about 200 ° C to 250 ° C. (Fig. 10 (a)) Next, as in the first actual form, a Mo film having a thickness of 50 nm to 200 nm and an Al-Nd alloy film having a thickness of 100 nm to 300 nm are sequentially formed by sputtering, and through a photolithography process. Patterned and high reflectance reflective electrode 31 Form and complete the TFT substrate. The method of forming the high reflectance reflective electrode 31 is exactly the same as that of the first embodiment. (FIGS. 10 (b) and 8 (e)) As described above, by using the halftone mask, the insulating film 71 having unevenness can be formed in one step, which is a step as compared with the first embodiment. Can be reduced.

[0046] In the present embodiment, the method of forming the unevenness by using the halftone mask has been described, but in addition to the method of using the halftone mask, separate masks are used for the half-remaining area and the full-remaining area. Irradiate the insulating film 71 by using a method of forming similar irregularities by changing the exposure amount, or by arranging a pattern finer than the limit of the resolution ability of exposure to make it pseudo-transmissive. It is also possible to apply a method of changing the amount of exposure to be applied depending on the location.

Next, a third embodiment of the present invention will be described with reference to the drawings. The third embodiment is an example of a semi-transmissive liquid crystal display device in which a reflective electrode is formed on an organic interlayer insulating film having irregularities and a pixel electrode made of a transparent conductive film is also formed. In this embodiment, only a step of forming a pixel electrode made of a transparent conductive film is added to the manufacturing process of the TFT substrate, and the structure and manufacturing method of other parts are exactly the same as those in the first embodiment described above. is there.

[0048] The configuration of the TFT substrate of the liquid crystal display device according to the third embodiment of the present invention and the manufacturing method thereof will be described in detail with reference to FIGS. 11 to 15 and 8. FIG. 11 is a plan view showing the configuration of one pixel portion of the TFT substrate of the liquid crystal display device of the present embodiment, and FIGS. 12 to 15 are process cross-sectional views corresponding to the BB line portion of FIG. Here, an example in which a TFT having an inverted staggered structure is used as the switching element is shown, and a diagram of the outermost peripheral pixel portion on the leftmost side of FIG. 1 is shown. Further, FIG. 8 is a process cross-sectional view in the short side direction of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18.

In the present embodiment, as shown in FIGS. 11 and 15, one pixel portion of the TFT substrate of the liquid crystal display device of the present embodiment is composed of scanning lines 11 and signal lines 12 orthogonal to each other and their wiring. A reflective electrode that reflects and transmits light incident on each of the switching elements provided in each of the enclosed pixel regions and light incident on each pixel region, and applies a voltage to the liquid crystal 36 sandwiched between the facing substrate 20. 31. A pixel electrode 81 made of a transparent conductive film and a first insulating film 51 and a second insulating film 52 for forming predetermined irregularities on the reflective electrode 31 are included, and the gate electrode 41 is formed on the scanning line 11. The drain electrode 42 is connected to the signal line 12, the source electrode 43 is connected to the reflective electrode 31, and the reflective electrode 31 is connected to the pixel electrode 81 made of a transparent conductive film.

[0050] Here, the reflective electrode 31 is formed so as to surround the periphery of the pixel electrode 81, and the periphery of the transparent conductive film constituting the pixel electrode 81 is coated with a metal film constituting the reflective electrode 31, and is electrically operated at this portion. The connection is made.

As shown in FIGS. 12 (a) to 15 and 8, the manufacturing process of the TFT substrate having the above configuration can be roughly divided into (1) film formation and patterning of the metal film of the gate electrode 41, (1). 2) Gate insulating film 53, a-Si layer 44a, n ⁺Film formation and patterning of mold a-Si layer 44b, (3) film formation of metal film of drain electrode 42 and source electrode 43, film formation of patterning and passionation film 54, (4) film formation of first insulating film 51 Film formation, patterning and surface shape conversion processing, (5) film formation and patterning of the second insulating film 52, (6) patterning of the passion film 54, (7) pixel electrode 81 and terminal connection electrode 63 It consists of a total of 8 steps: film formation of transparent conductive film, patterning, (8) film formation of metal film of reflective electrode 31, and patterning.

[0052] Steps (1) to (3) are exactly the same as the steps up to the formation of the passivation film 54 in the first embodiment, and the TFT 14 is formed on the transparent insulating substrate 10a. The opening of the passivation membrane 54 is not performed at this point. (FIGS. 12 (d) and 8 (c)) Steps (4) to (5) are exactly the same as steps (6) to (7) of the first embodiment. However, since this embodiment is a semi-transmissive liquid crystal display device, in order to prevent coloring of the first insulating film 51 and the second insulating film 52, full exposure is performed after development in the first embodiment. Different from. (Fig. 13 (c), Fig. 8 (c)) Next, the passivation film 54 on the source electrode 43, the scanning line terminal 15, the signal line terminal 16, and the terminal metal film 61 of the common wiring terminal 18 The passivation film 54 and the gate insulating film 53 are patterned to open the contact hole 55 and the terminal contact hole 62, respectively. At this time, although not shown, the passivation film 54 and the gate insulating film 53 on the end of the common wiring 13 and the passivation film 54 and the gate insulating film 53 on the end of the terminal metal film 61 of the signal line terminal 16 And the passivation film 54 on the end of the signal line 12 on the signal line terminal 16 side are simultaneously patterned and opened. (Fig. 14 (a), Fig. 8 (d)) Next, a transparent conductive film such as ITO having a thickness of 40 nm to 100 nm is formed by sputtering, and patterned through a photolitho process, and the pixel electrode 81 and the scanning line terminal 15 are formed. , Signal line terminal 16, terminal part of common wiring terminal 18 Connection electrode 63 on the metal film 61, common wiring binding wire 17 (not shown) on the end of common wiring 13, and terminal part of signal line terminal 16. A connection electrode (not shown) for connecting the metal film 61 and the signal line 12 is formed. At this time, it is desirable that the film formation of the transparent conductive film is performed in the same manner as the film formation of the metal film to be the reflective electrode 31 described in the first embodiment to avoid the influence of gas emission. Further, as described in the first embodiment, the pattern of the transparent conductive film is not formed on the pixel portion contact hole 45 on the source electrode 43. (Fig. 14 (b), Fig. 8 (e)) Next As in the first embodiment, a Mo film having a thickness of 50 nm to 200 nm and an Al-Nd alloy film having a thickness of 100 nm to 300 nm are sequentially formed by sputtering, patterned through a photolithography process, and reflected with high reflectance. The electrode 31 is formed to complete the TFT substrate. The method of forming the high reflectance reflective electrode 31 is exactly the same as that of the first actual form. At this time, the reflective electrode 31 is connected to the source electrode 43 and the pixel electrode 81 of each pixel, is removed between the respective pixel regions (on the scanning line 11 and on the signal line 12), and is in the display region. The outside is also removed. Therefore, no Mo and Al-Nd alloy film remains on each of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. This situation is exactly the same as that of the first embodiment. Further, since the transparent conductive film (ITO film) constituting the pixel electrode 81 is covered with the metal film (Al-Nd alloy / Mo film) constituting the reflective electrode 31, it is developed during the development of the photolitho process. There is no risk of the liquid seeping through the metal film from the edge of the transparent conductive film (because the photoresist is not developed on the edge of the transparent conductive film and the metal film is not exposed to the developing solution), and ITO-Al. It is possible to prevent the transparent conductive film from peeling off due to the battery action between them, and it is possible to significantly reduce the defect defects of the liquid crystal display device. (FIGS. 14 (c) and 8 (e)) and thereafter, a liquid crystal display panel is manufactured in exactly the same manner as in the first embodiment (FIG. 15), and the liquid crystal display device is completed. As described above, a transflective liquid crystal display device having high reflectance, no yellowing, and no problem of writing defects can be obtained. At the same time, the outside of the display area is also removed. Therefore, no Mo and Al-Nd alloy film remains on each of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. This situation is exactly the same as that of the first embodiment. Further, since the transparent conductive film (ITO film) constituting the pixel electrode 81 is covered with the metal film (Al-Nd alloy / Mo film) constituting the reflective electrode 31, it is developed during the development of the photolitho process. There is no risk of the liquid seeping through the metal film from the edge of the transparent conductive film (because the photoresist is not developed on the edge of the transparent conductive film and the metal film is not exposed to the developing solution), and ITO-Al. It is possible to prevent the transparent conductive film from peeling off due to the battery action between them, and it is possible to significantly reduce the defect defects of the liquid crystal display device. (FIGS. 14 (c) and 8 (e)) and thereafter, a liquid crystal display panel is manufactured in exactly the same manner as in the first embodiment (FIG. 15), and the liquid crystal display device is completed. As described above, a transflective liquid crystal display device having high reflectance, no yellowing, and no problem of writing defects can be obtained. At the same time, the outside of the display area is also removed. Therefore, no Mo and Al-Nd alloy film remains on each of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. This situation is exactly the same as that of the first embodiment. Further, since the transparent conductive film (ITO film) constituting the pixel electrode 81 is covered with the metal film (Al-Nd alloy / Mo film) constituting the reflective electrode 31, it is developed during the development of the photolitho process. There is no risk of the liquid seeping through the metal film from the edge of the transparent conductive film (because the photoresist is not developed on the edge of the transparent conductive film and the metal film is not exposed to the developing solution), and ITO-Al. It is possible to prevent the transparent conductive film from peeling off due to the battery action between them, and it is possible to significantly reduce the defect defects of the liquid crystal display device. (FIGS. 14 (c) and 8 (e)) and thereafter, a liquid crystal display panel is manufactured in exactly the same manner as in the first embodiment (FIG. 15), and the liquid crystal display device is completed. As described above, a transflective liquid crystal display device having high reflectance, no yellowing, and no problem of writing defects can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. In the fourth embodiment, unlike the first to third embodiments, the emitted light is not scattered by the reflecting electrode having unevenness, but the scattering film 91 attached on the color filter 21 on the opposite substrate 20 side. This is an example of a reflective liquid crystal display device performed in. In the present embodiment, there is no step of forming an insulating film having irregularities on the TFT substrate 10. That is, the reflective electrode 31 is formed directly on the passivation film 54.

[0054] The configuration of the liquid crystal display device according to the fourth embodiment of the present invention and the manufacturing method thereof will be briefly described with reference to FIG. FIG. 16 is a panel cross-sectional view of the liquid crystal display device of the present embodiment, and is a cross-sectional view of the AA line, CC line, and one pixel portion of FIG. 2 (the BB line portion corresponds to the cross section shown in FIG. 4). ).

The manufacturing process of the TFT substrate of the liquid crystal display device having the above configuration is roughly divided into (1) film formation and patterning of the metal film of the gate electrode 41, (2) gate insulating film 53, and a-Si layer 44a. , N ⁺Film formation and patterning of mold a-Si layer 44b, (3) Film formation and patterning of metal film of drain electrode 42 and source electrode 43, (4) Film formation and patterning of passion film 54, (5) Terminal It consists of a total of 6 steps: film formation and patterning of the transparent conductive film of the part connection electrode 63, and (6) film formation and patterning of the metal film of the reflective electrode 31. Since the steps (6) to (7) are deleted from the first embodiment, the description thereof will be omitted.

[0056] However, since the reflective electrode 31 is formed on the passivation film 54 made of silicon nitride formed by plasma CVD instead of the insulating film of the coating system, the method of forming the metal film to be the reflective electrode is the first. It is a little different from the first embodiment. That is, in the present embodiment, in the sputtering apparatus, the TFT substrate 10 in the states shown in FIGS. 5 (d) and 8 (e) is first conveyed to the heating chamber and heated at room temperature or at a temperature of 170 ° C. or lower. After that, the TFT substrate 10 is transported to the film forming chamber, and the Mo film and the Al-Nd alloy film are rapidly formed continuously. Here, the heating chamber and the film forming chamber may be the same chamber or different chambers. This is because, unlike the first embodiment, the TFT substrate 10 does not have an insulating film for coating, and is hardly affected by gas emission. As a result, an Al-Nd alloy film having a high reflectance without white turbidity can be obtained (described later). In the present embodiment, it is desirable to increase the film thickness of the passivation film 54 to about 300 nm to 800 nm. When the passivation film 54 is flattened with a coating-based insulating film, step (6) (concavo-convex forming step by the first insulating film 51) is only deleted in the first embodiment, and reflection is performed. Since the method of forming the metal film to be the electrode is the same as that of the first embodiment, it is not suitable for the present embodiment having the purpose of almost eliminating the influence of the exhaust gas.

[0057] Further, it is desirable that the Nd concentration of the Al-Nd alloy film is 0.5 wt% or more and 10 wt% or less, exactly as in the first embodiment. Furthermore, by setting the substrate temperature at the time of film formation to 170 ° C or less, the surface morphology (fine irregularities) of the reflecting electrode can be controlled to an average pitch of 1 μm or less, and the reflectance in the wavelength range of 200 nm to 400 nm can be controlled at a wavelength of 400 nm. It can be 90% or more of the reflectance. As a result, hillock in the heat treatment step such as firing of the alignment film in the subsequent step can be suppressed, and a high reflectance reflective electrode 31 can be obtained, and at the same time, a reflective electrode 31 without yellowing can be obtained regardless of the type of the alignment film. Can be (described later).

[0058] Hereinafter, a liquid crystal display panel is manufactured in the same manner as in the first embodiment to complete the liquid crystal display device, but the difference from the first embodiment is that the liquid crystal display panel is scattered on the color filter 21 of the facing substrate 20. The film 91 is provided. The scattering film 91 is composed of, for example, a novolak resin mixed with beads made of plastic particles or the like. By optimizing the diameter and blending ratio of the plastic particles, a scattering effect similar to that of a reflective electrode having irregularities can be obtained. As described above, a reflective liquid crystal display device having high reflectance, no yellowing, and no problem of writing defects can be obtained.

[0059] In the above embodiment, an example in which a reverse staggered channel etch type TFT is used as the switching element has been described, but a channel protection type TFT or a forward staggered type TFT may be used. Further, not only these staggered type TFTs but also coplanar type TFTs may be used, and further, polysilicon (p-Si) TFTs may be used. Further, as the switching element, a MIM diode may be used instead of the TFT. Further, as the substrate having the switching element and the opposing substrate, other substrates such as a plastic substrate, a ceramics substrate, a semiconductor substrate (excluding the case of a semitransmissive liquid crystal display device) and the like may be used instead of the glass substrate.

[0060] Further, the present invention can be applied not only to an active matrix type liquid crystal display device but also to an STN liquid crystal display device and the like. Further, the method of forming the metal film to be the reflective electrode of the fourth embodiment does not use a coating-based insulating film as a base, for example, forming the unevenness of the reflective electrode with a roughened glass substrate. Needless to say, it can be widely applied to reflective or semi-transmissive liquid crystal display devices in general.

Next, the basis for the numerical limitation of the present invention will be described below with reference to FIGS. 17 to 23.

[0062] FIG. 17 is an example of a graph showing the relationship between the substrate temperature during film formation of an Al-Nd alloy and the average pitch of fine surface irregularities of the Al-Nd alloy film. Here, an Al-Nd alloy having a composition of Nd 4.5 wt% was used, and a film was formed on a glass substrate by changing the substrate temperature by sputtering to prepare a sample. The surface unevenness was obtained by taking an SEM photograph from directly above 50,000 times and measuring it with a ruler. From the SEM photograph from the diagonal direction of the sample, it was confirmed that the surface morphology of Al became finer as the substrate temperature decreased, and both the size and depth of the unevenness became smaller. It was found that when the substrate temperature was 200 ° C, the average pitch of the unevenness was about 1.5 μm, but it was about 0.9 μm at 150 ° C and 0.5 μm or less at 100 ° C or less. On the other hand, although the depth of the unevenness is not accurate, it is about 0.5 μm when the substrate temperature is 200 ° C, about 0.3 μm when the substrate temperature is 150 ° C, and about 0.1 μm to 0.2 μm when the substrate temperature is 100 ° C or less.

[0063] FIG. 18 is an example of a graph showing the reflectance of the AlNd alloy film obtained by the film formation of FIG. Here, the reflectance is standardized with the reflectance of the Al-deposited film attached to the measuring device as 100%. It can be seen that when the substrate temperature at the time of film formation is 120 ° C, the reflectance gradually increases toward the short wavelength side. On the other hand, when the substrate temperature at the time of film formation was 200 ° C, the same tendency was shown up to about 400 nm, but it was found that the reflectance sharply decreased in the wavelength range of 200 nm to 400 nm.

[0064] FIGS. 19 and 20 are examples of graphs showing the reflectance due to the substrate temperature during film formation when the film thicknesses of the AlNd alloy film are 150 nm and 300 nm, respectively. This reflectance is the relative reflectance standardized with the reflectance of the sample when the substrate temperature at the time of film formation is 120 ° C in FIG. 18 as 100%. In the graph, RT is the data formed at room temperature. When the substrate temperature at the time of film formation is 150 ° C or higher, the reflectance tends to decrease in the wavelength range of 200 nm to 400 nm, and it can be seen that the reflectance decreases sharply especially at 200 ° C. Further, it can be seen that the thicker the Al film thickness, the greater this tendency.

[0065] FIG. 21 is an example of a graph showing the transmittance of the alignment film. Here, an alignment film manufactured by Nissan Chemical Industries and a general alignment film manufactured by JSR were used. It was found that the transmittance on the wavelength side shorter than 600 nm decreases depending on the alignment film. When a material such as polyimide, which is a component, is easily colored, it is presumed that such a transmittance characteristic is obtained.

FIG. 22 is a table showing the relationship between the Nd concentration of the AlNd alloy and the hillock and reflectance due to heat treatment. Here, hillock was heat-treated at 230 ° C. for 1 hour, which was the same as that for firing the alignment film, and observed with an optical microscope. Hillock occurred when the Nd concentration was 0.1 wt% (x mark), but did not occur when the Nd concentration was 0.5 wt% or more ( mark). In addition, the reflectance could be maintained at the same level as pure Al formed at room temperature when the Nd concentration was 0.1 wt% to 5 wt%, but decreased by about 6 to 8% at a wavelength of 400 nm at 10 wt%, and further. At 20 wt%, it decreased by more than 10% at a wavelength of 400 nm.

[0067] Fig. 23 shows the substrate temperature during film formation of an Al-Nd alloy (Nd concentration 4.5 wt%), the color appearance and reflectance of the manufactured liquid crystal display device, and the contact between the lower metal film and the metal film serving as the reflective electrode. It is a table which shows the relationship with resistance. Regarding the color appearance, when the substrate temperature at the time of film formation of the Al-Nd alloy is 200 ° C and the alignment film has a transmittance characteristic like the alignment film B shown in FIG. 21 is used. Only yellowing was observed (x mark). Regarding the reflectance, when the substrate temperature was 170 ° C and 200 ° C, it decreased by about 1 to 5% at a wavelength of 400 nm ( mark) (see FIGS. 19 and 20). When the substrate temperature was 20 ° C (room temperature), there was no problem on the glass, but on the organic insulating film, white turbidity occurred due to the influence of the exhaust gas, and it decreased by about 5% at a wavelength of 400 nm ( mark). Regarding contact resistance, there was no problem when the substrate temperature was 70 ° C or higher, but when the substrate temperature was 20 ° C (room temperature), an increase in contact resistance was confirmed due to the effect of gas emission (x mark). ..

[0068] Summarizing the above experimental results, regarding the Al-Nd alloy film constituting the reflective electrode of the liquid crystal display device, if the substrate is an insulating film such as silicon nitride formed by the plasma CVD method, the film is formed. The temperature is preferably 170 ° C or lower. On the other hand, when the base is a coating-type insulating film such as resin, it is desirable that the temperature is 70 ° C or higher and 170 ° C or lower. As a result, even when a alignment film having a transmittance characteristic such as the alignment film B in FIG. 21 is used, yellowing of the color appearance of the liquid crystal display device can be prevented and high reflectance can be obtained. At the same time, it is possible to prevent poor contact between the lower metal film and the metal film serving as the reflective electrode. At this time, from FIG. 17, the surface morphology of the AlNd alloy film constituting the reflective electrode preferably has an average pitch of fine irregularities of 1 μm or less, and more preferably 0.6 μm or less. That is, it is necessary to control such surface morphology. Further, from FIGS. 19 and 20, it is desirable that the reflectance of the Al-Nd alloy film constituting the reflective electrode is such that the reflectance in the wavelength range of 200 nm to 400 nm is 95% or more of the reflectance in the wavelength range of 400 nm. That is, it is necessary to control the film quality having such reflectance characteristics.

[0069] On the other hand, the Nd composition of the Al-Nd alloy film constituting the reflective electrode is preferably 0.5 wt% or more and 10 wt% or less, and more preferably 0.5 wt% or more and 5 wt% or less. As a result, it is possible to prevent the occurrence of hillock on the reflective electrode due to the heat treatment in the subsequent process (thus, it is possible to prevent contamination of the rubbing roll during the alignment process), and at the same time, it is possible to obtain a liquid crystal display device having high reflectance. ..

[0070] Further, it is desirable that the alignment film formed on the reflective electrode of the liquid crystal display device has a light transmittance of 95% or more in the wavelength range of 300 nm to 600 nm. This makes it possible to prevent yellowing of the color appearance of the liquid crystal display device.

It is not yet clear that the combination of the surface morphology of the reflective electrode and the alignment film causes yellowing of the color appearance of the reflective or transflective liquid crystal display device, but the following mechanism is presumed. Will be done. That is, if the surface of the reflective electrode has large irregularities, the alignment film penetrates into the surface, and the optical path passing through the alignment film is effectively lengthened, so that it is easily absorbed as in the alignment film B in FIG. it is conceivable that. In particular, in the reflective liquid crystal display device, light passes through the alignment film a total of four times, so that the light absorption by the alignment film is larger than that in the transmissive liquid crystal display device. As a result of increased light absorption in the ultraviolet light region, it is considered that the color appearance of the liquid crystal display device turns yellow.

[0072] The situation described here is not only when the reflective electrode is an Al-Nd alloy or another Al alloy, but also when the reflective electrode material is another reflective electrode material, for example, silver or a silver alloy having a higher reflectance than Al. It is believed that this is exactly the same.

[Effect of the Invention] As described above, according to the present invention, according to the present invention, there is no yellowing in color appearance with high reflectance, and there is no writing defect due to contact resistance between the source electrode and the reflective electrode. Alternatively, a semi-transmissive liquid crystal display device can be provided with a high yield.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing a configuration of a thin film transistor array substrate (TFT substrate) used in the liquid crystal display device according to the first embodiment of the present invention. (Common with the second, third and fourth embodiments) FIG. 2 is a panel plan view of the liquid crystal display device according to the first embodiment of the present invention. (Common to the second, third and fourth embodiments) FIG. 3 is a panel sectional view of the AA line, CC line and one pixel portion (corresponding to the cross section of the BB line portion in FIG. 4) in FIG.

FIG. 4 is a plan view showing a configuration of a pixel portion of a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention. (Common with the second embodiment) FIG. 5 is a process cross-sectional view corresponding to the BB line portion of FIG. (Common with the second embodiment) FIG. 6 is a process cross-sectional view showing a manufacturing process following FIG. (Common with the second embodiment) FIG. 7 is a process cross-sectional view showing a manufacturing process following FIG. 6, and is a panel cross-sectional view.

FIG. 8 is a process cross-sectional view in the short side direction of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 of the liquid crystal display device according to the first embodiment of the present invention. (Common with the second and third embodiments) FIG. 9 is a process cross-sectional view showing a manufacturing process of a TFT substrate of the liquid crystal display device of the second embodiment of the present invention, and corresponds to the BB line portion of FIG. It is a process cross-sectional view following the process (c) of FIG.

FIG. 10 is a process cross-sectional view showing a manufacturing process following FIG.

FIG. 11 is a plan view showing the configuration of one pixel portion of the TFT substrate of the liquid crystal display device according to the third embodiment of the present invention.

12 is a process cross-sectional view corresponding to the BB line portion of FIG. 11. FIG.

FIG. 13 is a process cross-sectional view showing a manufacturing process following FIG.

FIG. 14 is a process cross-sectional view showing a manufacturing process following FIG.

FIG. 15 is a process cross-sectional view showing a manufacturing process following FIG. 14, and is a panel cross-sectional view.

16 is a panel cross-sectional view of the liquid crystal display device according to the fourth embodiment of the present invention, and is a cross-sectional view of AA line, CC line and one pixel portion (corresponding to the cross section of the BB line portion in FIG. 4) of FIG. Is.

FIG. 17 is an example of a graph showing the relationship between the substrate temperature during film formation of an Al-Nd alloy and the average pitch of surface irregularities of the Al-Nd alloy film.

FIG. 18 is an example of a graph showing the reflectance of the AlNd alloy film obtained by the film formation of FIG.

FIG. 19 is an example of a graph showing the reflectance due to the substrate temperature during film formation when the film thickness of the Al-Nd alloy film is 150 nm.

FIG. 20 is an example of a graph showing the reflectance due to the substrate temperature during film formation when the film thickness of the Al-Nd alloy film is 300 nm.

FIG. 21 is an example of a graph showing the transmittance of an alignment film.

FIG. 22 is a table showing the relationship between the Nd concentration of an Al-Nd alloy and the hillock and reflectance due to heat treatment.

FIG. 23 shows the substrate temperature at the time of film formation of an Al-Nd alloy (Nd concentration 4.5 wt%), the color appearance and reflectance of the manufactured liquid crystal display device, and the contact resistance between the lower metal film and the metal film serving as the reflective electrode. It is a table showing the relationship between.

FIG. 24 is a cross-sectional view of a conventional general reflective liquid crystal display device.

[Code description] 10 TFT board 11 Scan line 12 Signal line 13 Common wiring 14 TFT 15 Scan line terminal 16 Signal line terminal 17 Common wiring binding wire 18 Common wiring terminal 20 Opposing board 21 Color filter 22 Black matrix 23 Sealing material 24 Sealing hole Material 31 Reflective electrode 32 Organic interlayer insulating film 33 Opposite electrode 34 Alignment film 35 In-plane spacer 36 Liquid crystal 37 1/4 wavelength plate 38 Deflection plate 41 Gate electrode 42 Drain electrode 43 Source electrode 44 Semiconductor layer 45 Pixel contact hole 51 1st Insulating film 52 Second insulating film 53 Gate insulating film 54 Passion film 55 Contact hole 61 Terminal metal film 62 Terminal contact hole 63 Connection electrode 71 Insulation film 81 Pixel electrode 91 Scattering film