JP4019080B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

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

  In recent years, small liquid crystal display devices for portable and PDA applications have been widely used. Reflective or transflective liquid crystal display devices are used as liquid crystal display devices used for these because of demands for light weight, thickness reduction, and low power consumption.

  FIG. 24 shows a cross-sectional view of a general reflective liquid crystal display device disclosed in Japanese Patent Laid-Open No. 2000-258787 (Patent Document 1).

  In this reflective liquid crystal display device, a thin film transistor (TFT) as 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) or 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 using the stopper insulating film 114 provided on the channel 113c as a mask. It has been.

Next, an interlayer insulating film 115 in which an SiO ₂ film, an SiNx film, and an SiO ₂ film are stacked in this order is formed on the entire surface of the gate insulating film 112, the active layer 113, and the stopper insulating film 114, and provided corresponding to the drain 113d. A drain electrode 116 is formed by filling the contact hole with a metal such as aluminum (Al). Further, a planarization 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 113 s of the planarization insulating film 117, and the reflective electrode 119 that also serves as the source electrode is made of Al connected to the source 113 s through the contact hole. 117 is formed. Next, an alignment film 120 made of an organic resin such as polyimide is formed on the reflective electrode 119.

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

  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, hillocks are not generated, the surface becomes flat, and even if the film is formed at a substrate temperature of about 200 ° C., it is the same as pure Al formed at room temperature (non-heated) Describes that a reflective electrode having a high reflectance can be obtained.

  On the other hand, in JP-A-5-80327 (Patent Document 2), as a method of manufacturing a diffusive reflector for liquid crystal display, when forming a reflective film on an organic film, it is performed while heating at 100 ° C. to 250 ° C., Wrinkles are generated in the organic film due to the difference in thermal expansion coefficient between the organic film and the reflective film, and further, an Al film or a platinum (Pt) film constituting the reflective film is grain-grown at the time of film formation, and the reflective film is finely grown. It is described that irregularities are formed to improve scattering reflection characteristics.

  Japanese Patent Application Laid-Open No. 2000-111906 (Patent Document 3) discloses a method of manufacturing an electro-optical device in which a reflective layer having irregularities is formed. A metal film to be a reflective layer is formed under conditions of 80 to 250 angstroms / min and a film formation temperature of 100 ° C. to 300 ° C. Further, after the metal film is formed, heat treatment is performed, and an average pitch of 1 to 2 μm and a depth of the metal film surface are formed. It is described that a fine asperity of 0.2 μm is formed to improve the scattering reflection characteristics.

JP 2000-258787 A Japanese Patent Laid-Open No. 5-80327 JP 2000-111906 A

  However, even if an Al—Nd alloy as described in Japanese Patent Laid-Open No. 2000-258787 is used for the metal film that becomes the reflective electrode of the reflective liquid crystal display device or the transflective liquid crystal display device, the experiment of the present inventor is performed. Thus, it has been found that when the film is formed at a relatively high temperature of about 200 ° C., there is a problem that the color of the liquid crystal display device turns yellow (the appearance becomes yellowish) depending on the alignment film material (described later). ).

  On the other hand, when the metal film serving as the reflective electrode is formed without heating or at a low temperature of less than 70 ° C., a reflective liquid crystal display device in which the switching element and the reflective electrode are connected via a coating type interlayer insulating film or a half In the case of a transmissive liquid crystal display device, there is a problem that contact resistance between a metal film serving as a reflective electrode and a lower layer metal film serving as an electrode of a switching element is increased, and writing to the pixel electrode is deteriorated. In addition, when the metal film to be the reflective electrode is formed without heating, the metal film is altered by the outgas from the organic interlayer insulating film due to the temperature rise of the substrate due to the condensation heat at the time of film formation, and the reflectivity is increased. There is a problem of lowering. This phenomenon is particularly noticeable when Al or an alloy mainly composed of Al is used for the metal film to be the reflective electrode. In this case, there is a problem that Al becomes cloudy (white cloudy and reflectance decreases).

  An object of the present invention is to provide a reflective liquid crystal display device or a transflective liquid crystal display device that can prevent yellowing of the color of the liquid crystal display device, can obtain a high reflectance, and has no writing defects. It is to be.

The method of manufacturing a liquid crystal display device according to the present invention includes a bus wiring on a substrate, a switching element connected to the bus wiring, a reflective electrode made of an alloy mainly composed of aluminum connected to the switching element, and the reflective In a method for manufacturing a liquid crystal display device having an alignment film on an electrode, the reflective electrode is formed on a glass substrate or an uncoated interlayer insulating film, and the substrate temperature at the time of forming the reflective electrode is 170 ° C. or lower. The reflectance of the reflective electrode in a wavelength range of 200 nm to 400 nm is 90% or more of the reflectance at a wavelength of 400 nm.

Further, the manufacturing method of the liquid crystal display device of the present invention includes a bus wiring on a substrate, a switching element connected to the bus wiring, a reflective electrode made of an alloy mainly composed of aluminum connected to the switching element , In the method of manufacturing a liquid crystal display device having an alignment film on the reflective electrode, the reflective electrode is formed on a resin substrate or a coating type interlayer insulating film, and the substrate temperature at the time of forming the reflective electrode is 70 ° C. or more. The reflectance is set to 150 ° C. or lower, and the reflectance of the reflective electrode in the wavelength region of 200 nm to 400 nm is set to 90% or more of the reflectance at a wavelength of 400 nm.

Furthermore, 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 when the reflective electrode is formed.

As described above, by using an alloy of Al and Nd for a reflective electrode of a reflective liquid crystal display device or a transflective liquid crystal display device and performing film formation at a temperature of 170 ° C. or less, the average pitch of fine surface irregularities can be reduced. It is possible to form a reflective electrode having a fine morphology with less unevenness of 1 μm or less, preferably 0.6 μm or less, thereby reducing light absorption in the ultraviolet light region of a wavelength of 200 nm to 400 nm. Changes can be prevented. In addition, the morphology mentioned here refers to the surface form by the crystal structure of the metal film constituting the reflective electrode, and is a fine unevenness on the surface of the reflective electrode. Therefore, the reflective electrode is different from the unevenness reflected by the unevenness of the base film. (same as below)
At the same time, particularly in the case of a reflective liquid crystal display device or a transflective liquid crystal display device in which a reflective electrode is formed on a coating type interlayer insulating film, an alloy of Al and Nd is used for the reflective electrode, and the substrate is preliminarily set at 70 ° C. By forming the film by heating to a temperature of 0 ° C., the influence of the outgas from the interlayer insulating film of the coating system is eliminated, the cloudiness of the reflective electrode is prevented, the reflectance is high, and the metal film that becomes the reflective electrode It is possible to prevent an increase in contact resistance with the lower layer metal film serving as the electrode of the switching element.

BEST MODE FOR CARRYING OUT 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. 2 is a panel plan view of the liquid crystal display device according to the first embodiment of the present invention, and FIG. 3 is a line AA, CC line and one pixel portion of FIG. 2 (BB in FIG. 4 described later). It is a cross-sectional view of a panel corresponding to the cross section of the line portion).

  As shown in FIGS. 1 and 3, the TFT substrate 10 has a plurality of scanning lines 11 and a plurality of signal lines 12 arranged substantially orthogonally on a transparent insulating substrate 10a and connected to the intersections in the vicinity thereof. Then, a thin film transistor (TFT) 14 which is a switching element is provided, and these are arranged in a matrix. A plurality of common wirings 13 are arranged in parallel with the scanning lines, and a storage capacitor is formed between the pixel electrodes (reflection electrodes) 31 connected to the TFTs 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 the organic interlayer insulating film 32, and is provided thereon. Concavities and convexities are formed in the organic interlayer insulating film 32, and concavities and convexities (different from the surface morphological concavities and convexities of the reflective electrode) are also formed in the reflective electrode 31 reflecting the shape.

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 the common wiring binding line 17 on both sides of the TFT substrate, and the 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, the scanning line terminal 15 and the signal line terminal 16 are conceptually shown as occupying one side of the TFT substrate 10, but since the liquid crystal display device of the present invention is small and portable, both of them are the TFT substrate 10. Are provided together on one side. (See Figure 2)
On the other hand, as shown in FIGS. 2 and 3, the counter substrate 20 is provided with a counter electrode 33 for applying a voltage to the color filter 21 and the liquid crystal corresponding to the display area on the transparent insulating substrate 20a. A black matrix 22 is provided at the periphery. Since the reflective electrode 31 also serves as a light shielding layer, no black matrix is 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 clear).

  An alignment film 34 for aligning liquid crystal molecules is provided on the opposing surfaces of the TFT substrate 10 and the counter substrate 20, and both substrates are overlapped at a predetermined interval via a sealing material 23 and an in-plane spacer 35. 36 is clamped. The space of the sealing material into which the liquid crystal 36 is injected is sealed with a sealing material 24. Further, a quarter wavelength plate 37 and a deflection plate 38 are provided on the surface of the counter substrate 20 opposite to the surface facing the TFT substrate 10 to form a liquid crystal display panel. Although not shown in FIG. 2, thereafter, an IC chip as a drive circuit is mounted on the scanning line terminal 15 and the signal line terminal 16 by COG (chip on glass), and the liquid crystal display device is completed.

  As shown in FIG. 3, incident light 39 incident from the back side of the counter substrate 20 passes through the counter substrate 20 and the liquid crystal 36 layer, and is reflected on the reflective electrode 31 having predetermined irregularities on the surface of the TFT substrate 10, The light again passes through the liquid crystal 36 layer and the counter substrate 20 and is emitted to the outside as outgoing 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. FIG. 4 is a plan view showing the configuration of one pixel portion of the TFT substrate of the liquid crystal display device of this embodiment, and FIGS. 5, 6, and 7 are process sectional views corresponding to the BB line portion of FIG. is there. Here, an example in which a reverse staggered TFT is used as a switching element is shown, and a diagram of the leftmost outermost pixel portion in FIG. 1 is shown. FIG. 8 is 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 a long and narrow rectangular shape when viewed in plan view, meaning the short side direction). FIG.

  As shown in FIGS. 4 and 7, one pixel portion of the TFT substrate of the liquid crystal display device according to the present embodiment is provided in each of a scanning line 11 and a signal line 12 which are orthogonal to each other and a pixel region surrounded by these wirings. A reflective electrode 31 for reflecting light incident on each pixel region and applying a voltage to the liquid crystal 36 sandwiched between the counter substrate 20 and a predetermined unevenness on the reflective electrode 31. The gate electrode 41 is connected to the scanning line 11, the drain electrode 42 is connected to the signal line 12, and the source electrode 43 is connected to the reflective electrode 31, respectively. Has been. The reflective electrode 31 also functions as a pixel electrode that applies a voltage to the liquid crystal, and therefore needs to be separated for each pixel, and is separated for each pixel on the scanning line 11 and the signal line 12.

In addition, the TFT side substrate 10 has a gate electrode 41 formed in a TFT region on the transparent insulating substrate 10a, and a semiconductor layer 44 (a-Si layer 44a and n ⁺ type a−) via a gate insulating film 53 thereon. Si layer 44b) is formed, and a drain electrode 42 and a source electrode 43 are formed on the n ⁺ -type a-Si layer 44b. In each pixel region, a first insulating film 51 for irregularly forming a predetermined unevenness on the reflective electrode 31 is irregularly arranged, and a step of the first insulating film 51 is gently formed thereon. A second insulating film 52 is formed.

  Here, the first insulating film 51 is irregularly formed inside the display region in order to exhibit uniform reflective optical characteristics over the entire display region, but the outside of the display region (on the left side of FIG. 4). The region) is a region where a terminal electrode or the like is provided, and thus 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 portion, and has a slight spread outside the display area so as to completely cover the first insulating film 51. Is formed. Then, the reflective electrode 31 is formed on the passivation film 54 that protects the TFT 14, the first insulating film 51, and the second insulating film 52, and the second insulating film 52 and the passivation film 54 on the source electrode 43 are respectively formed. The provided contact holes 45 and 55 are connected to the source electrode 43.

  The surface of the reflective electrode 31 reflects unevenness due to 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. Therefore, the inclination angle of the unevenness is designed so that desired reflection optical characteristics can be obtained. In addition, the unevenness | corrugation should just be comprised by 2 or more types of different values about either a convex pitch, a concave pitch, convex height, or a concave depth at this time.

  Further, the lower limit of the film thickness of the first insulating film 51 is defined by the reflection optical characteristics and is also limited from the viewpoint of parasitic capacitance. That is, when the first insulating film 51 is thinly formed, the reflection direction of incident light cannot be changed greatly, and the distance between the reflective electrode 31 and the scanning line 11 and the signal line 12 becomes narrow. The parasitic capacitance between the signal line and the wiring increases, causing a delay in the signal, making it impossible to transmit a correct signal, and increasing the electric field between the signal line and the pixel. Display quality is 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, the second insulating film 52 is provided to moderate the unevenness of the first insulating film 51 and to make the surface a gentle curved surface. In addition, if the thickness is too large, the unevenness of the first insulating film 51 is canceled and flattened. Therefore, the thickness of the second insulating film 52 is preferably in the range of about 0.3 to 1.5 μm.

Next, a manufacturing method of the TFT substrate having the above configuration will be described. As shown in FIG. 5A to FIG. 7 and FIG. 8, this manufacturing process is roughly divided into (1) film formation and patterning of the gate electrode 41, and (2) gate insulating film 53, a. -Si layer 44a, n ⁺ -type a-Si layer 44b film formation, patterning, (3) metal film formation, patterning of drain electrode 42 and source electrode 43, (4) film formation of passivation film 54, Patterning, (5) film formation of transparent conductive film of terminal connection electrode 63, patterning, (6) film formation of first insulating film 51, patterning and surface shape conversion treatment, (7) second insulation The film formation and patterning of the film 52, and (8) the metal film formation and patterning of the reflective electrode 31 are all comprised of eight steps.

First, on a transparent insulating substrate 10a made of alkali-free glass having a thickness of 0.5 mm, a metal film such as Cr having a thickness of 100 nm to 300 nm is formed by sputtering, and using a known photolithography technique and etching technique. The terminal metal film 61 of the gate electrode 41, the scanning line 11 (not shown), the common wiring 13 (not shown), the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 is formed. In addition, the wiring material is not limited to Cr, and the resistance is low and the thin film is formed like a wiring film having a laminated structure in which a barrier metal such as Cr, Mo, titanium (Ti) is formed on Mo, Al, or an Al alloy. Any material can be used as long as it can be easily patterned by photolithography. (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 is formed by plasma CVD, and subsequently 150 nm to 300 nm of undoped amorphous silicon is formed on the gate insulating film 53 by plasma CVD. (A-Si) and an amorphous silicon (n ⁺ -type a-Si) doped with n ⁺ -type having a thickness of 30 nm to 50 nm are formed and patterned through a photolithography process, and the a-Si layer 44a and the n ⁺ -type are patterned. A semiconductor layer 44 made of the a-Si layer 44b is formed. The a-Si layer 44a is an active layer of the TFT 14, and the n ⁺ -type 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 having a thickness of 100 nm to 300 nm is formed by sputtering and patterned through a photolithography process to form the drain electrode 42, the source electrode 43, and the signal line 12. Thereafter, dry etching is performed using the drain electrode 42 and the source electrode 43 as a mask, and the n ⁺ -type a-Si layer 44b between the drain electrode 42 and the source electrode 43 is removed. This is to prevent direct current from flowing between the drain electrode 42 and the source electrode 43 via the n ⁺ -type a-Si layer 13b. Here, the wiring material is not limited to Cr, but has a low resistance, such as a laminated wiring film in which barrier metals such as Cr, Mo, and Ti are formed on the upper and lower sides of Mo, Al, or Al alloy. Any material that can be easily patterned by a lithography technique may be used. (Fig. 5 (c), Fig. 8 (b))
Next, a silicon nitride film having a thickness of 100 nm to 300 nm is formed by plasma CVD to form a passivation film 54 (FIG. 8C), the passivation film 54 on the source electrode 43, the scanning line terminal 15, and the signal. The passivation film 54 and the gate insulating film 53 on the terminal part metal film 61 of the line terminal 16 and the common wiring terminal 18 are patterned to open a contact hole 55 and a terminal part 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 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 photolithography process, and the scanning line terminal 15 and the signal line terminal 16 are formed. The connection electrode 63 on the terminal part metal film 61 of the common wiring terminal 18, the common wiring binding wire 17 (not shown) on the end part of the common wiring 13, the terminal part metal film 61 of the signal line terminal 16 and the signal A connection electrode (not shown) for connecting the line 12 is formed. At this time, a transparent conductive film pattern is not formed in the display region. Therefore, when a metal film in which Mo is laminated on top and bottom of Mo, Al, or an Al alloy is used for the source electrode 43, the ITO patterning needs to be performed with an etching solution such as oxalic acid that does not etch Mo. When the source electrode 43 is made of a metal film in which Cr or Ti is laminated on top and bottom of Cr, Al, or an Al alloy, an aqua regia or ferric chloride etchant may be used. Here, the reason why the transparent conductive film pattern is not formed in the display region is to avoid as much as possible the risk of peeling of the transparent conductive film due to the battery action between ITO and Al, which will be described later, in the contact hole 55 portion. In addition, the connection electrode 63 formed of the transparent conductive film on the 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 part during COG mounting. It is to do. (Fig. 5 (d), Fig. 8 (e))
Next, for example, a photosensitive novolac resin is applied in a thickness of 1 to 3 μm, and patterned with an alkaline developer through a photolithography process, thereby forming the first insulating film 51 irregularly in the display region. As the first insulating film 51, either a resin having no photosensitivity or a resin having photosensitivity can be used, and a formation process in the case of using a resin having no photosensitivity is performed on a substrate ( (1) Application of first insulating film 51, (2) Application of resist for patterning of first insulating film 51, (3) Exposure, (4) Development, (5) Etching of first insulating film 51, 6) Each process of resist stripping. On the other hand, the formation process when using a resin having photosensitivity consists of (1) application of the first insulating film 51 on the substrate, (2) exposure, and (3) development processes. The resist coating and stripping steps can be omitted. (FIG. 6A, FIG. 8E) 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 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 novolac resin is applied in a thickness of 0.3 to 1.5 μm, patterned with an alkali developer through a photolithography process, and baked at a temperature of about 200 ° C. to 250 ° C. A film 52 is formed, and a pixel portion contact hole 45 is formed corresponding to the contact hole 55 opened in the passivation film 54 on the source electrode 43. (Fig. 6 (c), Fig. 8 (e))
Here, an example in which the first insulating film 51 and the second insulating film 52 are made of a novolac organic resin material is shown. For example, a JSR PC403 or the like can be used. However, these materials do not have to be the same type and may be different types. Also, not only novolac resin, but also a combination of inorganic resin and organic resin such as acrylic resin and polyimide resin, silicon nitride film and acrylic resin, silicon oxide film and polyimide resin, or vice versa However, desired irregularities can be formed.

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

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 reflective electrode 31 having a high reflectivity. This patterning is performed by wet etching using a mixed acid composed 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 functions as a pixel electrode, so that the reflective electrode 31 is removed between the pixel regions (on the scanning line 11 and the signal line 12). At the same time, the outside of the display area is also removed. Therefore, the Mo and Al—Nd alloy film does not remain on the terminal portions 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 the ITO-Al gap generated by the developer soaking in the development of the photolithography process. There is a role to prevent peeling of the transparent conductive film due to the battery action, and a sufficient film thickness is required to prevent this battery action. (Fig. 6 (d), Fig. 8 (e))
Next, a method for forming a metal film to be the reflective electrode 31 will be described in detail. In the sputtering apparatus, the TFT substrate 10 in the state of FIGS. 6C and 8E is first transported to a heating chamber and heated to a temperature of 70 ° C. to 170 ° C. for about 1 to 2 minutes. The moisture contained in the insulating film 2 is sufficiently released. Next, the TFT substrate 10 is transported to the film formation 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 formation chamber are evacuated independently in different chambers. This is because the outgas from the coating system insulating film (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 avoid giving When heating and film formation are performed in the same chamber, it is important that the heating time is extended to about 2 to 5 minutes and the chamber is sufficiently evacuated during substrate heating (heat retention). Thereby, an Al—Nd alloy film having high reflectivity without white turbidity can be obtained, and at the same time, the contact resistance between the source electrode 43 and the reflective electrode 31 can be stabilized low (described later).

  Note that the substrate heating at the time of forming the Mo film and the substrate heating at the time of forming the Al—Nd alloy film do not necessarily have to be performed 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. during the film formation. This is because if the substrate heating temperature during the formation of the Mo film is low, the crystallinity of the Mo film is deteriorated, and the film quality of the Al—Nd alloy film and the etching property of the Al—Nd alloy / Mo film are adversely affected.

  The Nd concentration of the Al—Nd alloy film is desirably 0.5 wt% or more. Thereby, the hillock in heat processing processes, such as alignment film baking of a post process, can be suppressed, and the reflective electrode 31 with a high reflectance is obtained. Furthermore, by setting the substrate temperature during film formation to 170 ° C. or less, the surface morphology (fine irregularities) of the reflective electrodes 31 can be controlled to an average pitch of 1 μm or less, and the reflectance in the wavelength region of 200 nm to 400 nm is in the visible light region. The reflectance can be 90% or more. Thereby, the reflective electrode 31 without yellowing can be obtained irrespective of the type of the alignment film (described later). On the other hand, the Nd concentration is preferably 10 wt% or less. Thereby, an Al—Nd alloy film with high reflectivity is obtained (described later).

  Here, an example in which an Al—Nd alloy having a high reflectivity and a good consistency with the TFT process is used as the material of the reflective electrode 31 is not limited to this, but the reflectivity is high. Any metal may be used. For example, other Al alloys such as an Al—Ti alloy and an Al—Mo alloy, or silver (Ag) or a silver alloy having higher reflectivity may be used.

  Next, an alignment film 34 having a thickness of 50 nm to 100 nm is formed on the TFT substrate 10 by printing, and is baked at a temperature of about 200 ° C. to 230 ° C. to perform an alignment process. On the other hand, a counter substrate in which a color filter 21 and a counter electrode 33 made of a transparent conductive film such as ITO are formed on the transparent insulating substrate 20a corresponding to the display area, and a black matrix 22 is formed in the peripheral portion. Similarly, an alignment film 34 having a thickness of 50 nm to 100 nm is formed on the substrate 20 by printing, and is baked at a temperature of about 200 ° C. to 230 ° C. to perform an alignment process. Here, it is desirable to use an alignment film having a light transmittance of 95% or more in a wavelength range of 300 nm to 600 nm. Thereby, the reflective electrode 31 without yellowing can be obtained (described later).

The film surfaces of the TFT substrate 10 and the counter substrate 20 are connected to each other through a sealing material 23 (not shown) made of an epoxy resin adhesive and an in-plane spacer 35 (not shown) made of plastic particles. Are overlapped at a predetermined interval so as to face each other. Thereafter, the liquid crystal 36 is injected between the TFT substrate 10 and the counter substrate 20, and the space (injection port) of the sealing material 23 (not shown) into which the liquid crystal 36 is injected is sealed with a UV curable acrylate resin. Seal with 24 (not shown). Finally, a quarter-wave plate 37 and a deflection plate 38 are pasted on the surface opposite to the film surface of the counter substrate 20 to complete the liquid crystal display panel. (Fig. 7)
Thereafter, although not shown, an IC chip serving as a drive circuit is COG mounted on the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18, thereby completing the liquid crystal display device. As described above, a reflective liquid crystal display device with high reflectivity, no yellowing, and no problem of writing failure 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. This embodiment is intended to simplify the manufacturing process of the TFT substrate, and the structure of other parts and the manufacturing method 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, and 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 this embodiment, and FIGS. 5 and 9 to 10 are process cross-sectional views corresponding to the BB line portion of FIG. is there. Here, an example in which a reverse staggered TFT is used as a switching element is shown, and a diagram of the leftmost outermost pixel portion in FIG. 1 is shown. FIG. 8 is a process 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 FIG. 10B, in order to form predetermined unevenness on the reflective electrode 31, an insulating film 71 is integrally formed and irregularly and gently disposed. That is, the insulating film 71 of this embodiment has the role of the first insulating film and the second insulating film in the first embodiment.

As shown in FIGS. 5A to 5C, FIGS. 9A to 10B, and FIG. 8, the manufacturing process of the TFT substrate having the above structure is roughly divided into (1) gate electrode. 41 metal film formation / patterning, (2) gate insulating film 53, a-Si layer 44a, n ⁺ -type a-Si layer 44b film formation, patterning, (3) drain electrode 42, source electrode 43 (4) Formation and patterning of passivation film 54, (5) Formation and patterning of transparent conductive film of terminal connection electrode 63, and (6) Formation of insulating film 71. The film, patterning, and surface shape conversion treatment, (7) the metal film formation of the reflective electrode 31, and the patterning are composed of seven steps.

Steps (1) to (5) are exactly the same as those of the first embodiment, and the TFT 14, the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 are formed on the transparent insulating substrate 10a. (Fig. 9 (a), Fig. 8 (e))
Next, for example, an insulating film 71 made of a photosensitive novolac resin is applied to a thickness of 2 to 4.5 μm. Then, the insulating film 71 is exposed and developed to form irregularities, but in this embodiment, as a photomask, a transmissive region that transmits exposure light, a semi-transmissive region that attenuates and transmits a predetermined amount, A halftone mask in which a light shielding region is formed is used. In other words, 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 from which the insulating film 71 is completely removed. Align and align the exposure. (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 unevenness is formed in the insulating film 71. It should be noted that a region where a certain amount of film remains (semi-transmissive region 72b) is always arranged next to a region where the insulating film 71 is completely removed (transmission region 72c), and no steep step is generated by the insulating film 71. I am doing so. As described above, in the exposure, the halftone mask is used to expose the insulating film 71 for a long time or to expose the insulating film 71 completely by applying strong light, and the region where 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 formed by creating a region where the insulating film 71 is left to some extent by applying time exposure or weak light, and a region where the film is not removed without being exposed to light. The forming process 52 can be performed in one process. (Fig. 9 (c))
Next, similarly to the first embodiment, surface shape conversion processing is performed. In this process, the surface of the insulating film 71 after pattern formation is melted and converted into a smooth shape by performing heat treatment at a temperature of about 80 ° C. to 200 ° C. Note that the surface shape conversion process is not limited to heat treatment, and for example, a melting process using chemicals or the like 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 embodiment, a Mo film with a thickness of 50 nm to 200 nm and an Al—Nd alloy film with a thickness of 100 nm to 300 nm are sequentially formed by sputtering, patterned through a photolithography process, and have a high reflectivity. The reflective electrode 31 is formed to complete the TFT substrate. The method of forming the reflective electrode 31 with high reflectivity is exactly the same as in the first embodiment. (Fig. 10 (b), Fig. 8 (e))
Thus, by using the halftone mask, the insulating film 71 having projections and depressions can be formed in one step, and the number of steps can be reduced as compared with the first embodiment.

  In the present embodiment, the method of forming irregularities using a halftone mask has been described. However, in addition to the method using a halftone mask, exposure is performed using separate masks for the half-remaining region and the entire remaining region. Exposure amount to irradiate the insulating film 71 by a method of forming the same unevenness by changing the amount, or a method of making the pattern semi-transparent by arranging a pattern finer than the limit of the resolution of exposure. It is also possible to apply a method of changing the position 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 transflective 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, a pixel electrode forming process made of a transparent conductive film is added to the TFT substrate manufacturing process, and the structure and manufacturing method of the other parts are exactly the same as those of the first embodiment described above. is there.

  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. FIG. 11 is a plan view showing a 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 reverse staggered TFT is used as a switching element is shown, and a diagram of the leftmost outermost pixel portion in FIG. 1 is shown. FIG. 8 is a process 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 includes a scanning line 11 and a signal line 12 that are orthogonal to each other and pixels surrounded by these wirings. A reflective electrode 31 that applies a voltage to the liquid crystal 36 sandwiched between the TFT 14 that is a switching element provided in each region and the light incident on each pixel region and reflects and transmits light that is sandwiched between the counter substrate 20 and a transparent electrode It includes a pixel electrode 81 made of a conductive film, a first insulating film 51 and a second insulating film 52 for forming predetermined irregularities on the reflective electrode 31, and the gate electrode 41 is connected to the scanning line 11 and the drain electrode 42. Are 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.

  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 covered with the metal film constituting the reflective electrode 31. It is supposed to be.

As shown in FIGS. 12A to 15 and 8, the manufacturing process of the TFT substrate having the above configuration is roughly divided into (1) film formation / patterning of the metal film of the gate electrode 41, and (2) gate. Deposition and patterning of insulating film 53, a-Si layer 44a and n ⁺ -type a-Si layer 44b, (3) Deposition of metal film of drain electrode 42 and source electrode 43, patterning and formation of passivation film 54 (4) film formation, patterning and surface shape conversion treatment of the first insulating film 51, (5) film formation and patterning of the second insulating film 52, (6) patterning of the passivation film 54, ( 7) The film formation and patterning of the transparent conductive film of the pixel electrode 81 and the terminal portion connection electrode 63, and (8) the film formation and patterning of the metal film of the reflective electrode 31 are all comprised of 8 steps.

Steps (1) to (3) are exactly the same as the steps up to the formation of the passivation film 54 of the first embodiment, and the TFT 14 is formed on the transparent insulating substrate 10a. The opening of the passivation film 54 is not performed at this point. (FIGS. 12D and 8C) Steps (4) to (5) are exactly the same as steps (6) to (7) of the first embodiment. However, since the present embodiment is a transflective liquid crystal display device, in order to prevent coloring of the first insulating film 51 and the second insulating film 52, the entire exposure is performed after the development. And different. (FIG. 13 (c), FIG. 8 (c))
Next, the passivation film 54 on the source electrode 43, and the passivation film 54 and the gate insulating film 53 on the scanning line terminal 15, the signal line terminal 16, and the terminal metal film 61 of the common wiring terminal 18 are patterned. Then, a contact hole 55 and a terminal part contact hole 62 are opened, respectively. At this time, although not shown, the passivation film 54 and the gate insulating film 53 on the end portion of the common wiring 13, and the passivation film 54 and the gate insulating film 53 on the end portion of the terminal portion metal film 61 of the signal line terminal 16. Then, the passivation film 54 on the end of the signal line 12 on the signal line terminal 16 side is 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 photolithography process, and the pixel electrode 81, the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18 terminal portion. For connecting the connection electrode 63 on the metal film 61, the common wire binding wire 17 (not shown) on the end of the common wire 13, and the terminal metal film 61 of the signal line terminal 16 and the signal line 12. A connection electrode (not shown) is formed. At this time, the transparent conductive film is preferably formed by the same method as the formation of the metal film to be the reflective electrode 31 described in the first embodiment to avoid the influence of the outgas. Further, as described in the first embodiment, the transparent conductive film pattern 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, and patterned through a photolithography process to obtain a high reflectance. The reflective electrode 31 is formed to complete the TFT substrate. The method of forming the reflective electrode 31 with high reflectivity is exactly the same as in the first embodiment. At this time, the reflective electrode 31 is connected to the source electrode 43 and the pixel electrode 81 of each pixel, and is removed between the pixel regions (on the scanning lines 11 and the signal lines 12). The outside is also removed. Therefore, the Mo and Al—Nd alloy film does not remain on the terminal portions of the scanning line terminal 15, the signal line terminal 16, and the common wiring terminal 18. This situation is also exactly the same as in the first embodiment. Further, since the periphery of 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, development is performed during development in the photolithography process. There is no risk that the liquid penetrates from the edge of the transparent conductive film through the metal film (because the photoresist is not developed on the edge of the transparent conductive film and the metal film is not exposed to the developer), ITO-Al It is possible to prevent the transparent conductive film from being peeled off due to the battery action, and to greatly reduce point defects of the liquid crystal display device. (FIG. 14 (c), FIG. 8 (e))
Thereafter, a liquid crystal display panel is manufactured in 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 with high reflectivity, no yellowing, and no problem of writing failure 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 scattering of the emitted light is not performed by the reflective electrode having unevenness, but the scattering film 91 provided on the color filter 21 on the counter substrate 20 side. FIG. In this 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.

  A configuration of a liquid crystal display device according to a fourth embodiment of the present invention and a manufacturing method thereof will be briefly described with reference to 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, the CC line, and one pixel portion of FIG. 2 (the BB line portion is shown in FIG. 4). Corresponds to the cross section).

The manufacturing process of the TFT substrate of the liquid crystal display device having the above configuration is roughly classified as follows: (1) Formation / patterning of a metal film of the gate electrode 41, (2) Gate insulating film 53, a-Si layer 44a, n ⁺ Film formation and patterning of type a-Si layer 44b, (3) Metal film formation and patterning of drain electrode 42 and source electrode 43, (4) Film formation and patterning of passivation film 54, (5) Terminal The film formation and patterning of the transparent conductive film of the partial connection electrode 63 and (6) the film formation and patterning of the metal film of the reflective electrode 31 are all comprised of six steps. Since this is one obtained by deleting the steps (6) to (7) from the first embodiment, the description thereof will be omitted.

  However, since the reflective electrode 31 is formed not on the coating type insulating film but on the passivation film 54 made of silicon nitride formed by plasma CVD, the film forming method of the metal film serving as the reflective electrode is the first implementation. A little different from the form. That is, in this embodiment, after the TFT substrate 10 in the state of FIGS. 5D and 8E is first transferred to the heating chamber and heated to room temperature or a temperature of 170 ° C. or lower in the sputtering apparatus. Then, 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 formation chamber may be the same chamber or different chambers. This is because, unlike the first embodiment, the TFT substrate 10 has no coating-type insulating film and is hardly affected by the outgas. Thereby, an Al—Nd alloy film having high reflectivity without white turbidity is obtained (described later). In the present embodiment, it is desirable to increase the thickness of the passivation film 54 to about 300 nm to 800 nm. Note that, when the passivation film 54 is planarized with a coating-type insulating film, the step (6) (unevenness forming step by the first insulating film 51) is merely deleted in the first embodiment, and reflection is performed. Since the method for 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 outgas.

  The Nd concentration of the Al—Nd alloy film is desirably 0.5 wt% or more and 10 wt% or less, just as in the first embodiment. Furthermore, by setting the substrate temperature during film formation to 170 ° C. or less, the surface morphology (fine irregularities) of the reflective electrodes 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 is reflected at the wavelength of 400 nm. It can be 90% or more of the rate. Thereby, hillocks in a heat treatment step such as alignment film baking in the subsequent step can be suppressed, and a reflective electrode 31 with high reflectivity can be obtained. At the same time, a reflective electrode 31 without yellowing can be obtained regardless of the type of alignment film. (To be described later).

  Thereafter, in the same manner as in the first embodiment, a liquid crystal display panel is manufactured and a liquid crystal display device is completed. The difference from the first embodiment is that a scattering film 91 is formed on the color filter 21 of the counter substrate 20. It is to provide. The scattering film 91 is made of, for example, a novolac resin in which beads made of plastic particles or the like are mixed. By optimizing the diameter and blending ratio of the plastic particles, the same scattering effect as that of the reflective electrode having irregularities can be obtained. As described above, a reflective liquid crystal display device with high reflectivity, no yellowing, and no problem of writing failure can be obtained.

  In the above embodiment, an example of using an inverted staggered channel etch type TFT as a switching element has been described. However, a channel protection type TFT or a forward staggered type TFT may be used. In addition to these staggered TFTs, coplanar TFTs may be used, and polysilicon (p-Si) TFTs may also be used. Further, an MIM diode may be used as the switching element instead of the TFT. In addition, the substrate having the switching element and the counter substrate may be other than the glass substrate, for example, a plastic substrate, a ceramic substrate, a semiconductor substrate (except for a transflective liquid crystal display device), or the like.

  Furthermore, the present invention can be applied not only to an active matrix liquid crystal display device but also to an STN liquid crystal display device. In addition, the method for forming a metal film to be a reflective electrode according to the fourth embodiment does not use a coating-type insulating film as a base, for example, the reflective electrode is formed with a roughened glass substrate. Needless to say, the present invention can be widely applied to all reflective or transflective liquid crystal display devices.

  Next, the grounds for limiting the numerical values of the present invention will be described below with reference to FIGS.

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

  FIG. 18 is an example of a graph showing the reflectance of the Al—Nd alloy film obtained by the film formation of FIG. Here, the reflectance is normalized with the reflectance of the Al vapor deposition film attached to the measuring apparatus as 100%. It can be seen that when the substrate temperature during film formation is 120 ° C., the reflectance gradually increases as the wavelength becomes shorter. On the other hand, when the substrate temperature at the time of film formation is 200 ° C., the same tendency is shown up to about 400 nm, but it has been found that the reflectance rapidly decreases in the wavelength range of 200 nm to 400 nm.

  FIGS. 19 and 20 are examples of graphs showing the reflectivity depending on the substrate temperature during film formation when the film thickness of the Al—Nd alloy film is 150 nm and 300 nm, respectively. This reflectance is a relative reflectance normalized in FIG. 18 assuming that the reflectance of the sample when the substrate temperature during film formation is 120 ° C. is 100%. In the graph, RT is data formed at room temperature. It can be seen that when the substrate temperature during film formation is 150 ° C. or higher, the reflectance tends to decrease in the wavelength range of 200 nm to 400 nm, and particularly when the substrate temperature is 200 ° C. Moreover, it turns out that this tendency is so large that Al film thickness is thick.

  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 some alignment films have reduced transmittance on the shorter wavelength side than 600 nm. It is presumed that such a transmittance characteristic is obtained when a material that is easily colored is used for the component polyimide or the like.

  FIG. 22 is a table showing the relationship between the Nd concentration of the Al—Nd alloy and the hillocks and reflectivity due to heat treatment. Here, hillocks were heat-treated at 230 ° C. for 1 hour, which was equivalent to the alignment film baking, and observed with an optical microscope. When the Nd concentration was 0.1 wt%, hillocks were generated (x mark), but not 0.5 wt% or more (◯ mark). Further, the reflectivity was maintained at the same reflectivity as that of pure Al deposited at room temperature when the Nd concentration was 0.1 wt% to 5 wt%, but at 10 wt%, the reflectivity decreased by about 6 to 8% at a wavelength of 400 nm. Furthermore, at 20 wt%, the wavelength decreased by 10% or more at a wavelength of 400 nm.

  FIG. 23 shows the substrate temperature at the time of film formation of the Al—Nd alloy (Nd concentration 4.5 wt%), the color appearance of the manufactured liquid crystal display device, the reflectance, and the contact resistance between the lower metal film and the metal film serving as the reflective electrode. It is a table | surface which shows these relationships. As for coloration, only 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 such as the alignment film B shown in FIG. Yellowing was observed (x mark). Further, the reflectance decreased by about 1 to 5% at a wavelength of 400 nm (Δ mark) when the substrate temperature was 170 ° C. and 200 ° C. (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 was generated due to the influence of the outgas and decreased by about 5% at a wavelength of 400 nm (Δ mark). As for the contact resistance, there was no problem when the substrate temperature was 70 ° C. or higher. However, when the substrate temperature was 20 ° C. (room temperature), an increase in contact resistance was confirmed due to the effect of outgassing (× mark).

  Summarizing the above experimental results, regarding the Al—Nd alloy film constituting the reflective electrode of the liquid crystal display device, when the base is an insulating film such as silicon nitride formed by plasma CVD, the film forming temperature is 170. It is desirable that the temperature is not higher than ° C. On the other hand, when the base is a coating-type insulating film such as a resin, the temperature is desirably 70 ° C. or higher and 170 ° C. or lower. Thereby, even when the alignment film having a transmittance characteristic such as the alignment film B in FIG. 21 is used, yellowing of the color of the liquid crystal display device can be prevented and high reflectance can be achieved. At the same time, it is possible to prevent contact failure 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 Al—Nd alloy film constituting the reflective electrode is preferably such that the average pitch of the fine irregularities is 1 μm or less, and more preferably 0.6 μm or less. . That is, it is necessary to control to such a 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 95% or more of the reflectance in the wavelength region of 200 nm to 400 nm at the wavelength of 400 nm. That is, it is necessary to control the film quality having such reflectance characteristics.

  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, the occurrence of hillocks on the reflective electrode due to the heat treatment in the subsequent process can be prevented (thereby preventing contamination of the rubbing roll during the alignment process), and at the same time, a highly reflective liquid crystal display device can be obtained. .

  In addition, the alignment film formed on the reflective electrode of the liquid crystal display device desirably has a light transmittance of 95% or more in a wavelength region of 300 nm to 600 nm. Thereby, yellowing of the color of the liquid crystal display device can be prevented.

  It is not clear yet that the color change of the reflective or transflective liquid crystal display device is caused by the combination of the surface morphology of the reflective electrode and the alignment film, but the following mechanism is presumed. That is, if the unevenness of the reflective electrode surface is large, the alignment film will enter this, and the optical path passing through the alignment film will be effectively lengthened, and accordingly, it will be more susceptible to absorption as in the alignment film B of FIG. it is conceivable that. In particular, in a reflective liquid crystal display device, light passes through the alignment film a total of four times, so that light absorption by the alignment film is greater than in the transmissive liquid crystal display device. As a result of increased light absorption in the ultraviolet region, it is considered that the color of the liquid crystal display device turns yellow.

  The situation described here is exactly the same not only when the reflective electrode is an Al—Nd alloy or another Al alloy, but also when another reflective electrode material, for example, silver or silver alloy having a higher reflectance than Al is used. It seems that this is true.

  As described above, according to the present invention, there is provided a reflective or transflective liquid crystal display device having high reflectivity, no color change, and no writing failure due to contact resistance between the source electrode and the reflective electrode. Can be provided with high yield.

It is a conceptual diagram which shows the structure of the thin-film transistor array substrate (TFT substrate) used for the liquid crystal display device of the 1st Embodiment of this invention. (Common to the second, third and fourth embodiments) It is a panel top view of the liquid crystal display device of the 1st Embodiment of this invention. (Common to the second, third and fourth embodiments) FIG. 5 is a panel cross-sectional view of the AA line, the CC line, and one pixel portion (corresponding to the cross section of the BB line portion of FIG. 4) in FIG. 2. It is a top view which shows the structure of the one pixel part of the TFT substrate of the liquid crystal display device of the 1st Embodiment of this invention. (Common with the second embodiment) It is process sectional drawing corresponding to the BB line part of FIG. (Common with the second embodiment) It is process sectional drawing which shows the manufacturing process following FIG. (Common with the second embodiment) It is process sectional drawing which shows the manufacturing process following FIG. 6, and is panel sectional drawing. FIG. 5 is a process cross-sectional view in the short side direction of a scanning line terminal 15, a signal line terminal 16, and a 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. 10 is a process cross-sectional view illustrating a manufacturing process of a TFT substrate of a liquid crystal display device according to a second embodiment of the present invention, corresponding to the line B-B in FIG. 4 and a process cross-sectional view subsequent to process (c) in FIG. It is. FIG. 10 is a process cross-sectional view illustrating the manufacturing process following FIG. 9. It is a top view which shows the structure of the one pixel part of the TFT substrate of the liquid crystal display device of the 3rd Embodiment of this invention. It is process sectional drawing corresponding to the BB line part of FIG. It is process sectional drawing which shows the manufacturing process following FIG. It is process sectional drawing which shows the manufacturing process following FIG. It is process sectional drawing which shows the manufacturing process following FIG. 14, and is panel sectional drawing. FIG. 6 is a cross-sectional view of a liquid crystal display device according to a fourth embodiment of the present invention, which is taken along lines AA, CC, and one pixel portion (corresponding to the cross section of the line BB in FIG. 4). It is sectional drawing. It is an example of the graph which shows the relationship between the substrate temperature at the time of Al-Nd alloy film-forming, and the average pitch of the surface unevenness | corrugation of an Al-Nd alloy film. It is an example of the graph which shows the reflectance of the Al-Nd alloy film obtained by the film-forming of FIG. It is an example of the graph which shows the reflectance by the substrate temperature at the time of film-forming when the film thickness of an Al-Nd alloy film is 150 nm. It is an example of the graph which shows the reflectance by the substrate temperature at the time of film-forming when the film thickness of an Al-Nd alloy film is 300 nm. It is an example of the graph which shows the transmittance | permeability of an alignment film. It is a table | surface which shows the relationship between the Nd density | concentration of an Al-Nd alloy, the hillock by heat processing, and a reflectance. The relationship between the substrate temperature at the time of film formation of the Al—Nd alloy (Nd concentration 4.5 wt%), the color appearance of the manufactured liquid crystal display device, the reflectance, and the contact resistance between the lower metal film and the metal film serving as the reflective electrode. It is a table | surface shown. It is sectional drawing of the conventional general reflection type liquid crystal display device.

Explanation of symbols

10 TFT substrate 11 Scanning line 12 Signal line 13 Common wiring 14 TFT
DESCRIPTION OF SYMBOLS 15 Scan line terminal 16 Signal line terminal 17 Common wiring bundling line 18 Common wiring terminal 20 Counter substrate 21 Color filter 22 Black matrix 23 Seal material 24 Sealing material 31 Reflective electrode 32 Organic interlayer insulation film 33 Counter electrode 34 Orientation 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 part contact hole 51 First insulating film 52 Second insulating film 53 Gate insulating film 54 Passivation film 55 Contact Hole 61 Terminal part metal film 62 Terminal part contact hole 63 Connection electrode 71 Insulating film 81 Pixel electrode 91 Scattering film

Claims (3)

A liquid crystal display device comprising: a bus wiring on a substrate; a switching element connected to the bus wiring; a reflective electrode made mainly of an aluminum connected to the switching element ; and an alignment film on the reflective electrode. In the manufacturing method,
The reflective electrode is formed on a glass substrate or an uncoated interlayer insulating film, the substrate temperature at the time of forming the reflective electrode is 170 ° C. or less, and the reflectance of the reflective electrode in a wavelength range of 200 nm to 400 nm is set to a wavelength. A method for manufacturing a liquid crystal display device, characterized in that the reflectivity at 400 nm is 90% or more. A liquid crystal display device comprising: a bus wiring on a substrate; a switching element connected to the bus wiring; a reflective electrode made mainly of an aluminum connected to the switching element ; and an alignment film on the reflective electrode. In the manufacturing method,
The reflective electrode is formed on a resin substrate or a coated interlayer insulating film, the substrate temperature at the time of forming the reflective electrode is set to 70 ° C. or higher and 150 ° C. or lower, and the reflective electrode has a reflectance in a wavelength range of 200 nm to 400 nm. Is 90% or more of the reflectance at a wavelength of 400 nm.   3. The method of manufacturing a liquid crystal display device according to claim 2, wherein the substrate is heated at the time of forming the reflective electrode at least before the film formation.

Images