JP2009244300A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form protection diodes in a frame region in a liquid crystal display having a configuration in which the frame region around a display region is set as a reflective display region. <P>SOLUTION: In order to set the frame region 20 as the reflective display region, a pixel electrode 110 and a reflective electrode 111 are formed in the frame region 20. Each of protection diodes D1, D2 formed in the frame region 20 is formed by connecting a gate electrode and a drain electrode or a source electrode to a TFT (Thin Film Transistor) formed by the same process as that for a TFT formed in the display region 10 through a connection electrode 130. On a portion where the connection electrode 130 is formed, a through-hole 120 is formed into the pixel electrode 110 and the reflective electrode 111 of the frame area 20. Consequently, the protection diodes D1, D2 can be formed without increasing processes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a liquid crystal display device that performs a white display or the like using a reflective electrode on a frame region around a display region.

  The liquid crystal display device is divided into a display area and a peripheral frame area. In general, liquid crystal display devices used in mobile phones, etc., often have a transmissive display using a backlight, but when external light is strong so that it can be used outdoors, a reflective display is also required. Has been. In order to satisfy this, a transflective liquid crystal display device has been developed. The display area is formed by many pixels. In a transflective liquid crystal display device, this is realized by dividing the pixels into a transmissive display area and a reflective display area.

  In addition, liquid crystal display devices used for mobile phones and the like are required to have various designs. Recently, there is a demand for various changes in the design of the frame area. Examples include making the frame area colorful or forming a specific image. On the other hand, instead of forming a fixed image in the frame area by printing or forming a specific color separately by printing, the frame area has the same configuration as the reflective display area, and the frame area has a fixed display such as white display. By doing so, there is a demand to improve the design.

  A TFT is formed in each pixel in the display area. In order to protect the TFT from static electricity or the like, it is necessary to form a protective diode connected to a scanning line or a video signal line. This protective diode must be formed outside the display area. Therefore, even when a reflective mode display region is formed in the frame region, it is necessary to form a protective diode in a part of the frame region. Note that “Patent Document 1” can be cited as a document describing the protection diode.

Japanese Patent Laid-Open No. 2001-21909

  FIG. 3 is a plan view of a liquid crystal display panel used for a mobile phone or the like. In FIG. 3, the counter substrate 200 is installed on the TFT substrate 100. A liquid crystal layer is sandwiched between the TFT substrate 100 and the counter substrate 200. A sealing material is provided around the inside of the TFT substrate 100 and the counter substrate 200 to seal the liquid crystal layer and to bond the TFT substrate 100 and the counter substrate 200 together.

  In the liquid crystal display panel, a region where an image is formed is the display region 10 in FIG. A TFT (thin film transistor), a pixel electrode 110, and the like are formed for each pixel in the display region 10 of the TFT substrate 100, and a counter electrode, a color filter, a black matrix (light shielding film), and the like are formed in the display region 10 of the counter substrate 200. Is formed. The display area 10 is formed by a large number of pixels. Each pixel has a transmissive display area for forming an image by controlling light transmitted from a backlight disposed behind the liquid crystal display panel, and reflection of external light. A reflective display area for forming an image is formed by controlling light. The liquid crystal display panel shown in FIG. 3 includes a transmissive display area and a reflective display area in one pixel.

  A frame area 20 is formed around the display area 10. The frame area 20 has the same configuration as the reflective display area. The frame region 20 of the liquid crystal display panel shown in FIG. 3 is set so as to have a constant display such as a white display mode in which external light is totally reflected.

  In FIG. 3, the TFT substrate 100 is formed larger than the counter substrate 200. A terminal portion 150 for supplying power and signals from the outside to the liquid crystal display panel is formed in a portion where the TFT substrate 100 is larger than the counter substrate 200. The terminal unit 150 is provided with an IC driver 30 for driving the liquid crystal display panel. The IC driver 30 is provided with a scanning signal driving circuit 31 and a video signal driving circuit 32.

  A large number of pixels are formed in a matrix in the display area 10, and a TFT is formed for each pixel. The TFT is connected to a scanning line and a video signal line (not shown). When a high voltage due to static electricity or the like enters the scanning line or the video signal line from the outside, the TFT is destroyed. If the TFT is destroyed, the pixel in that portion becomes defective. Therefore, in order to prevent the destruction of the TFT, it is necessary to form a protection circuit connected to the scanning line or the video signal line around the display area 10.

  In the liquid crystal display panel as shown in FIG. 3, a reflection mode region is formed around the display region 10, but for the reflection mode display, a reflection formed of a metal film on the TFT substrate 100 side. It is necessary to form an electrode.

  Here, when the protection diodes constituting the protection circuit are arranged further on the outer peripheral side so as not to overlap with the reflection mode display area of the frame area 20, there is a problem that the frame area 20 becomes wide. .

  Therefore, in order to narrow the frame, it is necessary to form a protective diode under the reflective electrode. However, if both are simply overlapped, an increase in the manufacturing process or a short circuit between the protective diode and the reflective electrode becomes a problem.

  An object of the present invention is to form a protective diode under a reflective electrode to form a narrow frame efficiently without increasing the cost and without degrading the display quality of the frame region 20. That is.

  The present invention overcomes the above problems, and specific means are as follows.

  (1) A TFT substrate having a display region and a frame region disposed around the display region, a counter substrate facing the TFT substrate, and a liquid crystal layer sandwiched between the TFT substrate and the counter substrate The TFT substrate extends in a first direction, the scanning line is arranged in a second direction intersecting the first direction, and extends in the second direction. And the image signal lines arranged in the first direction, and the display area includes a pixel electrode and an in-pixel TFT in an area surrounded by the scanning lines and the image signal lines. A pixel is formed, and the frame region of the TFT substrate is configured to have a reflection type display by forming a frame region pixel electrode and a frame region reflective electrode. A protection diode is formed to protect the TFT. The protective diode is formed by installing a connection electrode on a TFT formed by the same process as the TFT in the pixel, and the protective diode is partially in the frame region via an insulating film. A liquid crystal display device characterized in that a through-hole is formed in the frame region pixel electrode and the frame region reflective electrode at a portion where the connection electrode is installed, and is overlapped with the reflective electrode .

  (2) The liquid crystal display device according to (1), wherein the protection diode is provided for the scanning line and the video signal line.

  (3) The pitch of the through holes formed in the frame area pixel electrode and the frame area reflective electrode is equal to the pitch of the scanning lines or the pitch of the video signal lines. The liquid crystal display device described.

  (4) The liquid crystal display device according to any one of (1) to (3), wherein the connection electrode is formed of the same material as the pixel electrode.

  (5) A light-shielding film is formed on the counter substrate at a position corresponding to the through hole of the frame region reflective electrode formed in the frame region of the TFT substrate. To (4).

  (6) A TFT substrate having a display region and a frame region disposed around the display region, a counter substrate facing the TFT substrate, and a liquid crystal layer sandwiched between the TFT substrate and the counter substrate The TFT substrate extends in a first direction, the scanning line is arranged in a second direction intersecting the first direction, and extends in the second direction. In the display area, a pixel having an in-pixel TFT is formed in an area surrounded by the scanning line and the video signal line. The pixel includes a transmissive display region that has a pixel electrode and controls transmitted light from a backlight, and a reflective display region that has a reflective electrode and controls light from the outside. The frame area includes a frame area pixel electrode and a frame. A reflective electrode is formed to enable reflective display, and a protective diode for protecting the in-pixel TFT is formed in the frame region, and the protective diode is formed in the pixel. It is formed by installing a connection electrode on the TFT formed by the same process as the TFT, and the protective diode partially overlaps the frame region reflective electrode via an insulating film, A liquid crystal display device, wherein a through-hole is formed in the portion where the connection electrode is installed with respect to the frame region pixel electrode and the frame region reflection electrode.

  (7) The liquid crystal display device according to (6), wherein the protection diode is provided for the scanning line and the video signal line.

  (8) The pitch of the through holes formed in the frame area pixel electrode and the frame area reflection electrode is equal to the pitch of the scanning lines or the pitch of the video signal lines. The liquid crystal display device described.

  (9) The liquid crystal display device according to any one of (6) to (8), wherein the connection electrode is formed of the same material as the pixel electrode.

  (10) The light-shielding film is formed on the counter substrate at a position corresponding to the through hole of the frame region reflective electrode formed in the frame region of the TFT substrate (6) To a liquid crystal display device according to any one of (9).

  A reflective display area is formed in the frame area around the display area, a certain display such as white display is performed in the frame area, and a protection circuit for protecting the TFT formed in the display area is formed in the frame area. Therefore, a liquid crystal display device with excellent design and high reliability can be realized.

  Further, according to the present invention, since the protective diode can be formed under the reflective electrode, the frame can be narrowed.

  Further, according to the present invention, the protection diode is constituted by a TFT formed in the same process as the TFT formed in the display region, and the through hole and the connection electrode for forming the protection diode are accompanied by an increase in the number of process steps. Therefore, a highly reliable liquid crystal display device can be realized without increasing the manufacturing cost.

  FIG. 4 is a schematic diagram showing a circuit of the liquid crystal display device. In FIG. 4, a scanning signal driving circuit 31 is installed on the left side of the display area 10, and a video signal driving circuit 32 is installed on the upper side of the display area 10. FIG. 4 is a schematic diagram. In an actual product, as shown in FIG. 3, the scanning signal driving circuit 31 and the video signal driving circuit 32 are incorporated in one IC driver 30 and are installed on the lower side of the screen. Has been.

  In FIG. 4, a scanning line 40 extends from the scanning signal driving circuit 31 toward the display region 10 in a first direction (for example, a horizontal direction) and intersects the first direction (for example, a vertical direction). Are arranged. In addition, the video signal lines 50 extend from the video signal driving circuit 32 toward the display area 10 in the second direction (for example, the vertical direction) and are arranged in the first direction (for example, the horizontal direction). In the display area 10, pixels are formed in an area surrounded by the scanning lines 40 and the video signal lines 50. In the pixel, a pixel electrode 110, a TFT for switching, or the like is formed.

  A backlight is provided on the back surface of the liquid crystal display device shown in FIG. In the pixel shown in FIG. 4, a transmissive display region 13 that controls light from the backlight to form an image and a reflective display region 12 that reflects light from the outside to form an image are formed. In FIG. 4, the dotted line in the pixel indicates the boundary between the transmissive display area 13 and the reflective display area 12. The reflective display mode is used when the outside is bright, such as outdoors.

  When static electricity enters the scanning line 40 or the video signal line 50, the TFT formed in the display area 10 may be destroyed. A pixel in which the TFT is destroyed becomes defective. In FIG. 4, a protective diode 70 is formed around the display area 10 in order to prevent the TFT from being destroyed. Around the display area 10, a ground wire 60 is arranged. A protective diode 70 is formed between the ground line 60 and the scanning line 40 or the video signal line 50. When a high voltage due to static electricity or the like enters the scanning line 40 or the video signal line 50, the protective diode 70 is discharged. Then, static electricity and the like are released to the ground wire 60 to protect the TFT.

  The protective diode 70 is formed by connecting the gate of a TFT manufactured by the same process as the TFT formed in the display region 10 to the drain or source. In FIG. 4, the gate of the first protection diode D1 is connected to the scanning line 40 or the video signal line 50, and the gate of the second protection diode D2 is connected to the ground line 60. The reason why the diodes having different directions are installed between the scanning line 40 or the video signal line 50 and the ground line 60 is because the static electricity may be a positive voltage or a negative voltage.

  It should be noted that the portion of the ground line 60 that intersects the scanning line 40 is formed of the same material as the video signal line 50, and the portion of the ground line 60 that intersects the video signal line 50 is formed of the same material simultaneously with the scanning line 40. It is desirable to do.

  FIG. 5 is a circuit showing the configuration of the diode shown in FIG. 5A corresponds to, for example, the first protection diode D1 in FIG. 4, and FIG. 5B corresponds to, for example, the second protection diode D2 in FIG. Each of the diodes in FIGS. 5A and 5B is formed by connecting the gate of the TFT to the drain or source.

  FIG. 6 is a cross-sectional view of a liquid crystal display device in a pixel portion where a TFT is formed. The pixel portion is divided into a transmissive display area 13 and a reflective display area 12. FIG. 6 shows a cross-sectional structure in the reflective display area 12. In both the reflective display area 12 and the transmissive display area 13, the supply of the video signal is controlled by a single TFT. The liquid crystal display device of FIG. 6 uses a-Si as the semiconductor layer 103 and has a so-called bottom gate structure.

  In FIG. 6, the gate electrode 101 is formed on the TFT substrate 100. The gate electrode 101 is formed by sputtering and then patterned by photolithography. The gate electrode 101 is made of Al and has a thickness of about 300 nm. The scanning line 40, a part of the ground line 60, and the like are formed simultaneously in the same layer as the gate electrode 101. A gate insulating film 102 is formed to cover the gate electrode 101. The gate insulating film 102 is formed, for example, by forming a SiN film by a CVD method. The gate insulating film 102 is about 400 nm, for example.

  A semiconductor layer 103 is formed on the gate electrode 101 with the gate insulating film 102 interposed therebetween. The semiconductor layer 103 is formed of a-Si and has a thickness of about 150 nm. A channel region of the TFT is formed in the a-Si layer. The n + Si layer 104 is formed before the source electrode 105 and the drain electrode 106 are provided on the a-Si layer. This is because an ohmic contact is formed between the a-Si layer and the source electrode 105 or the drain electrode 106.

  A source electrode 105 or a drain electrode 106 is formed on the n + Si layer 104. In the same layer as the source electrode 105 or the drain electrode 106, the video signal line 50, part of the ground line 60, and the like are formed. The source electrode 105 or the drain electrode 106 is formed of Mo, Al, or the like. In addition, when Al is used, the upper and lower sides are covered with Mo or the like. This is because the contact resistance may become unstable when Al contacts with ITO or the like in the contact hole 113 portion.

  After the source electrode 105 or the drain electrode 106 is formed, channel etching is performed using the source electrode 105 and the drain electrode 106 as a mask. In order to completely remove the n + Si layer 104 from the channel layer, etching is performed up to the upper part of the a-Si layer, whereby a channel etching region 109 is formed. Thereafter, an inorganic passivation film 107 is formed to cover the entire TFT. The inorganic passivation film 107 is made of SiN. The inorganic passivation film 107 is about 400 nm, for example.

  An organic passivation film 108 is formed so as to cover the inorganic passivation film 107. Since the organic passivation film 108 has a role as a planarizing film, the organic passivation film 108 is formed thick, for example, with a thickness of about 2 μm. For example, an acrylic resin is used for the organic passivation film 108. The organic passivation film 108 is made of a photosensitive acrylic resin and can be patterned without using a resist.

  Thereafter, contact holes 113 are formed in the organic passivation film 108 and the inorganic passivation film 107. This is for the purpose of establishing electrical connection between the pixel electrode 110 formed of ITO and the source electrode 105 of the TFT. Since FIG. 6 is a cross-sectional view of the reflective display region 12, the reflective electrode 111 is formed on the pixel electrode 110. The reflective electrode 111 is made of Al having a high reflectance. In the transmissive display region 13, the reflective electrode 111 does not exist, and only the pixel electrode 110 that is a transparent electrode is formed. FIG. 6 shows an example in which the pixel electrode 110 that is a transparent electrode is formed in all the regions below the reflective electrode 111 in the reflective display region 12, but the present invention is not limited to this. The pixel electrode 110 that is a transparent electrode may be formed only in a part of the region 12 below the reflective electrode 111, or the pixel electrode 110 that is a transparent electrode may not be formed in the reflective display region 12. Good.

  In FIG. 6, an alignment film 112 for aligning liquid crystal molecules is formed on the reflective electrode 111. A liquid crystal layer 300 is sandwiched between the TFT substrate 100 and the counter substrate 200. The liquid crystal molecules of the liquid crystal layer 300 have an initial alignment defined by the alignment film 112 formed on the TFT substrate 100 and the alignment film 112 formed on the counter substrate 200.

  In FIG. 6, a color filter 201 is formed inside the counter substrate 200. The color filter 201 is formed with red, green, and blue color filters 201 for each pixel, and a color image is formed. A black matrix (light-shielding film) 202 is formed between the color filter 201 and another color filter 201 to improve the contrast of the image. In the transmissive display region 13 of the pixel, the black matrix 202 has a role as a light shielding film for the TFT and prevents a photocurrent from flowing through the TFT. In the reflective display region 12, the TFT is covered with an Al reflective film (reflective electrode 111), thereby blocking light incident from the viewer side. Accordingly, in the reflective display region 12, the black matrix 202 does not need a function as a light-shielding film for the TFT, so the area of the black matrix 202 may be smaller than that of the transmissive display region 13.

  An overcoat film 203 is formed to cover the color filter 201 and the black matrix 202. Since the surface of the color filter 201 and the black matrix 202 is uneven, the surface is flattened by the overcoat film 203. A step forming layer 204 is formed on the overcoat film 203. The step forming layer 204 is formed only in the reflective display region 12.

  Since the reflective display area 12 controls light incident on the liquid crystal layer 300 from the outside, the light is modulated by the liquid crystal layer 300 twice for incidence and reflection. On the other hand, in the transmissive display area 13, only the light incident from the backlight is modulated by the liquid crystal layer 300. Therefore, in order to match Δn · d in the transmissive display region 13 and the reflective display region 12, the step forming layer 204 is necessary in order to make the liquid crystal layer thickness in the reflective layer ½ that of the transmissive display region 13. . Note that Δn is the refractive index anisotropy of the liquid crystal layer 300, and d is the layer thickness of the liquid crystal layer 300.

  A counter electrode 205 is formed on the step forming layer 204. By applying a voltage between the pixel electrode 110 or the reflective electrode 111 formed on the pixel of the TFT substrate 100 and the counter electrode 205 formed on the counter substrate 200, the liquid crystal molecules are rotated to transmit or reflect light. An image is formed by controlling. An alignment film 112 that defines the initial alignment of the liquid crystal is formed on the counter electrode 205.

  FIG. 6 shows a method of operating a liquid crystal by applying a vertical electric field between the TFT substrate 100 and the counter substrate 200 as in the so-called TN method or VA method. The so-called IPS (In Plane Switching) system controls light by rotating liquid crystal molecules in a direction parallel to the TFT substrate 100. In the case of the IPS method, both the pixel electrode 110 and the counter electrode 205 are formed on the TFT substrate 100. The present invention can be applied regardless of the TN method, VA method, IPS method, or the like.

  In the liquid crystal display device to which the present invention is applied, as shown in FIG. 3, a reflective display area 12 is formed in a frame area 20 around the display area 10, and a constant display such as white display is always provided in the frame area 20. Display. Even when such a frame region 20 is formed, the protection diode 70 must be formed in order to protect the TFT formed in the display region 10.

  In this case, if the protective diode 70 is arranged at a position that does not overlap the reflective display area 12 of the frame area 20, there is a problem that the frame becomes wide. Therefore, in order to narrow the frame, it is necessary to form the protective diode 70 below the reflective display region 12 in the frame region 20. FIG. 7 shows an example in which the protective diode 70 is formed below the reflective display area 12 in the frame area 20. FIG. 7 shows a comparative example of the present invention and is a plan view showing a layout and the like of a protection diode formed under the reflective display region 12 in the frame region 20. 8 is a cross-sectional view taken along the line AA in FIG.

  In FIG. 7, the right side of the two-dot chain line is the display area 10, and the left side is the frame area 20. In FIG. 7, the scanning lines 40 extend in the horizontal direction and are arranged in the vertical direction. The video signal lines 50 extend in the vertical direction and are arranged in the horizontal direction. In the display area 10, an area surrounded by the scanning lines 40 and the video signal lines 50 is a pixel. The pixels are classified into a transmissive display area 13 and a reflective display area 12. A pixel electrode 110 is formed in the transmissive display area 13, whereas a reflective electrode 111 is formed on the pixel electrode 110 in the reflective display area 12. A TFT (not shown) is formed in each pixel and controls the transmissive display area 13 and the reflective display area 12 in common.

  The contact hole 113 formed in the reflective display region 12 is for establishing electrical connection between the source electrode 105 of the TFT formed under the pixel electrode 110 and the pixel electrode 110. The layer structure is as described with reference to FIG. 6, but the scanning line 40 is formed at the bottom of the conductive film, the video signal line 50 is formed thereon, and the pixel electrode 110 is formed thereon. .

  The frame region 20 is on the left side of the alternate long and short dash line. Since the frame region 20 is the reflective display region 12, the surface is covered with the frame region pixel electrode 110 and the frame region reflective electrode 111. The frame region pixel electrode 110 and the frame region reflective electrode 111 are the same as the pixel electrode 110 and the reflective electrode 111 in the pixels of the display region 10, but have a large area. Hereinafter, the frame area pixel electrode 110 is also simply referred to as the pixel electrode 110, and the frame area reflection electrode 111 is also simply referred to as the reflection electrode 111. In FIG. 7, the scanning line 40 extends in the frame area 20 similarly to the display area 10. The scanning line 40 is bent to form a first scanning line lead line 41, which is connected to an IC driver 30 (not shown) disposed on the lower side of FIG.

  Since many scanning lines 40 exist, the area | region which the leader line of the scanning line 40 requires increases. In order to prevent this, a layer in which the video signal line 50 is formed, which is different from the layer in which the scanning line 40 is formed, is used as the second scanning line lead line 42. Since the first scanning line lead line 41 and the second scanning line lead line 42 have different layers across the gate insulating film 102, the distance between the lines can be reduced, and as a result, the area of the lead wiring of the scanning line 40 can be reduced. I can do it. The scanning line 40 and the second scanning line lead line 42 are connected by the connection electrode 130 through the contact hole 113.

  In FIG. 7, a ground wire 60 extends in the vertical direction of the frame region 20 on the left side of the two-dot chain line. On both sides of the ground wire 60, a first protection diode D1 and a second protection diode D2 are installed. Both the first protection diode D1 and the second protection diode D2 are formed of TFTs, and the gate electrode 101 of the TFT is connected to the source electrode 105 or the drain electrode 106. Both the first protection diode D1 and the second protection diode D2 are connected to the same scanning line 40.

  The source electrode 105 of the first protection diode D 1 is connected to the ground line 60, and the gate electrode 101 and the drain electrode 106 are connected to the scanning line 40. On the other hand, the source electrode 105 of the second protection diode D2 is connected to the scanning line 40, and the gate electrode 101 and the drain electrode 106 are connected to the ground line 60. As a result, when viewed from the scanning line 40, a bidirectional diode is formed with respect to the ground line 60. Note that the drain electrode 106 or the source electrode 105 is temporarily named and may be interchanged. The first protection diode D1 and the second protection diode D2 are formed corresponding to all the scanning lines 40.

  In order to use the TFT as the protection diode 70, the drain electrode 106 or the source electrode 105 of the TFT must be connected to the scanning line 40 or the gate electrode 101. The drain electrode 106 and the source electrode 105 of the TFT are formed in the same layer, and the scanning line 40 and the gate electrode 101 of the TFT are formed in the same layer. Therefore, the drain electrode 106 or the source electrode 105 and the gate electrode 101 or the scanning line 40 need to be connected by forming the contact hole 113 in the gate insulating film 102 and connecting the connection electrode 130. The connection electrode 130 is made of ITO, which is a transparent conductive film, like the pixel electrode 110.

  FIG. 8 is a cross-sectional view taken along the line AA of FIG. In FIG. 8, the left side is a cross section of the frame area 20, and the right side is a cross sectional view of the reflective display area 12 in one pixel of the display area 10. A scanning line 40 and a second scanning line lead line 42 are displayed in the AR1 area which is the leftmost side of FIG. The scanning line 40 requires a lead line for connection to the IC driver 30 formed on the lower side of FIG. A lead line in the same layer as the scanning line 40 may be used. However, in order to reduce the interval between the lead lines, the second scanning formed in the same layer as the video signal line 50 is provided in the lead line of the scanning line 40. The line lead lines 42 and the first scan line lead lines 41 formed in the same layer as the scan lines 40 are alternately used. FIG. 8 shows an example in which the second scanning line leader line 42 is used as the leader line of the scanning line 40. The scanning line 40 and the second scanning line lead line 42 are connected by a connection electrode 130.

  In FIG. 8, the area AR2 displays the drain electrode 106 and the gate electrode 101 of the second protection diode D2 in FIG. As shown in FIG. 7, the ground wire 60 is branched to form the drain electrode 106 of the second protection diode D2. The drain electrode 106 and the gate electrode 101 are connected by a connection electrode 130 through a contact hole 113 formed in the gate insulating film 102. Note that although the connection electrode 130 is connected to a portion branched from the gate electrode 101, the connection electrode 130 is referred to as the gate electrode 101 in order to simplify the expression.

  On the right side of the second protection diode D2, a cross-sectional view of the reflective display region 12 in the pixel portion indicated by the region AR3 is displayed with the video signal line 50 interposed therebetween. In the area AR3, a part of the source electrode 105 of the TFT formed in the pixel portion is displayed. The TFT source electrode 105 and the pixel electrode 110 are connected via a contact hole 113. Since FIG. 8 shows the reflective display region 12, the reflective electrode 111 is formed on the pixel electrode 110.

  In FIG. 8, since the frame area 20 operates as the reflective display area 12, the entire frame area 20 is covered with the pixel electrode 110 and the reflective electrode 111. With the structure shown in FIGS. 7 and 8, the protective diode 70 can be formed under the reflective electrode 111 in the frame region 20 while operating the frame region 20 as the reflective display region 12. However, in order to realize the structure shown in FIGS. 7 and 8, there is a problem that the number of process steps required is increased.

  That is, as shown in FIG. 8, in order to realize this structure, after forming the inorganic passivation film 107, a contact hole 113 is formed in the inorganic passivation film 107 or in the inorganic passivation film 107 and the gate insulating film 102. Thereafter, ITO for constituting the connection electrode 130 is deposited, and further ITO is patterned by photolithography. Thereafter, a process such as formation of the organic passivation film 108 is performed. That is, in the configuration of FIG. 7 and FIG. 8, a process for forming the inorganic passivation film 107 or the contact hole 113 between the inorganic passivation film 107 and the gate insulating film 102, a process for depositing ITO as the connection electrode 130, and a process for patterning ITO Etc. will increase.

  The present invention solves such a problem, and enables the protective diode 70 to be formed in the frame region 20 while operating the frame region 20 as the reflective display region 12 by a process that is almost the same as the conventional example. Can be realized.

  FIG. 1 is a plan view of a TFT substrate 100 side of a liquid crystal display device according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line BB in FIG. In FIG. 1, the right side of the two-dot chain line is the display area 10, and the left side is the frame area 20. The display area 10 in FIG. 1 is the same as that described with reference to FIG. In FIG. 1, the frame region 20 is on the left side of the two-dot chain line. The frame region 20 is different from the structure of FIG. In FIG. 1, in order to operate the frame area 20 as the reflective display area 12, the pixel electrode 110 and the reflective electrode 111 are formed as in FIG. However, in FIG. 1, the pixel electrode 110 and the reflective electrode 111 are not formed in the portion where the connection electrode 130 is formed. That is, a through hole 120 indicated by a one-dot chain line is formed in the portion where the connection electrode 130 is formed with respect to the pixel electrode 110 and the reflective electrode 111.

  However, the portion where the through hole 120 is formed cannot be operated as the reflective display region 12. In this embodiment, in order to prevent the portion of the through hole 120 from becoming uneven in the screen, a black matrix (light shielding film) 202 is formed in the portion corresponding to the through hole 120 in the counter substrate 200. Prevent contrast degradation. The pitch HL of the through holes 120 is the same as the pitch of the scanning lines 40.

  In FIG. 1, in order to reduce the area of the lead line of the scan line 40, the second scan formed by the same layer as the first scan line lead line 41 and the video signal line 50 formed in the same layer as the scan line 40. The lead line 42 is used as in FIG. However, the configurations of the contact hole 113 and the connection electrode 130 that connect the second scanning line lead line 42 and the scanning line 40 are different.

  In the frame region 20 of FIG. 1, the first protection diode D1 and the second protection diode D2 are installed for all the scanning lines 40, as in FIG. However, the TFT connection method for forming the first protection diode D1 and the second protection diode D2 is different from that in FIG. In FIG. 1, a part of the ground wire 60 is branched to form the source electrode 105 or the drain electrode 106 of the first protection diode D1 and the second protection diode D2. Further, the scanning line 40 is branched to form the gate electrode 101 of the first protection diode D1. In the first protection diode D 1, the branched scanning line 40 is connected to the drain electrode 106 through the connection electrode 130. In the second protection diode D <b> 2, the branched scanning line 40 is connected to the source electrode 105 through the connection electrode 130. In this manner, bidirectional diodes composed of two diodes are formed between all the scanning lines 40 and the ground line 60.

  2 is a cross-sectional view taken along the line BB of FIG. 1, and is a cross-sectional view for explaining the configuration of FIG. In FIG. 2, the left side is a cross section of the frame area 20, and the right side is a cross sectional view of the reflective display area 12 in one pixel of the display area 10. In order to operate the frame region 20 of FIG. 2 as the reflective display region 12, the pixel electrode 110 and the reflective electrode 111 are formed on the organic passivation film 108, but the connection electrode 130 is not formed on the portion where the connection electrode 130 is formed. A through hole 120 is formed.

  The feature of the present invention is that the process for forming the connection electrode 130 can be simplified by forming the through hole 120 in the pixel electrode 110 and the reflective electrode 111 in the frame region 20. That is, in the present invention, the video signal line 50, the ground line 60 (a part of the ground line 60), the drain electrode 106, the source electrode 105, and the like formed in the same layer, and the scanning line 40 formed in another layer. Connection with the gate electrode 101 or the like (including other part of the ground wire 60 as necessary), the organic passivation film 108 and the inorganic passivation film 107, or the organic passivation film 108 and the inorganic passivation film 107 and the gate insulation. By forming a contact hole 113 in the film 102, the connection electrode 130 is formed of the same ITO as the pixel electrode 110.

  The formation process of the contact hole 113 can be performed by the same process as the formation of the contact hole 113 for connecting the TFT in the display region 10 and the pixel electrode 110. Since the contact hole 113 in the display region 10 is a connection between the pixel electrode 110 and the source electrode 105 of the TFT, it is a contact hole 113 for the organic passivation film 108 and the inorganic passivation film 107. The 20 contact holes 113 also require the contact holes 113 for the organic passivation film 108, the inorganic passivation film 107, and the gate insulating film 102. This can be dealt with by controlling the etching time for forming the contact holes 113. It is.

  ITO used as the connection electrode 130 is deposited and patterned by the same process as the pixel electrode 110. Therefore, the process for forming the connection electrode 130 does not substantially increase. Thereafter, the reflective electrode 111 is deposited on the ITO film. The reflective electrode 111 is patterned and removed from the through-hole 120 portion. However, since this patterning can be performed by the same patterning process as the reflective electrode 111 in the display region 10, the process of forming the through-hole 120 in the reflective electrode 111 is also substantial. Does not increase. Therefore, in this embodiment, the protective diode 70 can be formed in the frame region 20 without substantially increasing the process.

  In the through hole 120 of FIG. 2, a region BR <b> 1 is a diagram showing a connection between the scanning line 40 and the second scanning line lead line 42. Between the areas BR1 and BR2 in FIG. 2, a wiring that is branched from the scanning line 40 and becomes the gate electrode 101 is displayed. A region BR2 in FIG. 2 is a diagram illustrating a connection between the drain electrode 106 of the first protection diode D1 and the scanning line 40. In the first protection diode D1, the gate electrode 101 is at the same potential as the scanning line 40 and the drain electrode.

  A region BR3 in FIG. 2 is a diagram showing a connection between the ground wire 60 and the gate electrode 101 of the second protection diode D2. A region BR4 in FIG. 2 is a diagram illustrating a connection between the source electrode 105 of the second protection diode D2 and the scanning line 40. Therefore, in the second protection diode D2, the drain electrode 106 and the gate electrode 101 are connected to the ground line 60.

  2 is a cross-sectional view of the reflective display region 12 in the pixels of the display region 10. In BR5, only the source electrode 105 portion of the TFT of the pixel is described. A TFT source electrode 105 and a pixel electrode 110 formed of ITO are connected. Since the region BR5 is the reflective display region 12, the reflective electrode 111 made of Al is formed on the pixel electrode 110. In FIG. 2, the pixels are partitioned by video signal lines 50.

  1 and 2, it has been described that the connection electrode 130 is made of ITO. However, both ITO and Al electrodes can be used. Further, if necessary, Al of the reflective electrode 111 can be used as the connection electrode 130. In any case, only the exposure mask in photolithography is changed, and the number of process steps is not substantially increased.

  As a result, a part of the protective diode 70 can be hidden under the reflective electrode 111 in the frame region 20, so that the frame can be narrowed. In order to reduce the number and area of the through holes 120, when there are a plurality of connection electrodes 130 corresponding to one scanning line 40 or one video signal line 50, for example, as shown in FIG. It is desirable to arrange things together in one place.

  In the above description, the protection diode 70 connected to the scanning line 40 has been described. The protective diode 70 is provided not only for the scanning line 40 but also for the video signal line 50. In the case of installing to the video signal line 50, the layout for using the TFT as a diode, the position of the layer where the ground line 60 is formed, the layout for connecting the ground line 60 and the protective diode 70, etc. This is only slightly different, and is essentially the same as the method for forming the protection diode 70 for the scanning line 40 described above.

  A protective diode 70 for the video signal line 50 is also formed in the frame area 20 that operates as the reflective display area 12. Accordingly, the pixel electrode 110 and the reflective electrode 111 are formed on the organic passivation film 108, and a through hole 120 for the connection electrode 130 is formed in the pixel electrode 110 and the reflective electrode 111. The pitch of the through holes 120 is the same as the pitch of the video signal lines 50. The video signal line 50 may be drawn to the lower side of FIG. 3 with respect to the IC driver 30 shown in FIG. 3, and it is not necessary to provide a lead line area unlike the lead line of the scanning line 40. There is no need to perform drawing in layers, and all the video signal lines 50 can be formed by wiring in the same layer.

  In the above description, the display area 10 is described as a transflective liquid crystal display device capable of a transmissive display mode and a reflective display mode. That is, the pixel is composed of the transmissive display area 13 and the reflective display area 12. However, the present invention can also be applied to a reflective display type liquid crystal display device in which the display area 10 is entirely in the reflective display mode. Furthermore, the present invention can also be applied to the case where the display area 10 is a transmissive liquid crystal display device.

  In the above description, the TFT in the pixel electrode 110 and the TFT for forming the protective diode 70 in the frame region 20 have been described as being a bottom gate type using an a-Si film. The present invention is not limited to the case where a TFT in the pixel electrode 110 and a TFT for forming the protection diode 70 in the frame region 20 are so-called top gate type TFTs using a poly-Si film. I can do it.

  Further, as shown in the cross-sectional view of the modification of FIG. 2 of the present invention in FIG. 9, an opening is formed in the organic passivation film 108 in the region where the connection electrode 130 is formed, and the connection electrode is formed on the inorganic passivation film 107. 130 may be formed. Also in this case, the connection electrode 130 can be formed at the same time in the same process as the pixel electrode 110 or the reflective electrode 111.

It is a top view which shows the layout of the TFT substrate of this invention. It is BB sectional drawing of FIG. It is a top view of the liquid crystal display device with which this invention is applied. It is a schematic diagram of the drive circuit of a liquid crystal display device. It is a block diagram of a protection diode. It is sectional drawing of the reflective display area | region of a pixel. It is a top view which shows the layout of the TFT substrate of a comparative example. It is AA sectional drawing of FIG. It is a figure which shows the modification of this invention, and is sectional drawing corresponding to FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Display area, 12 ... Reflective display area, 13 ... Transmission display area, 20 ... Frame area, 30 ... IC driver, 31 ... Scan signal drive circuit, 32 ... Video signal drive circuit, 40 ... Scan line, 41 ... 1st Scanning line lead line 42... Second scanning line lead line 50. Video signal line 60. Ground line 70. Protection diode 100. TFT substrate 101. Gate electrode 102 102 Gate insulating film 103 Semiconductor layer 104 ... n + Si layer, 105 ... Source electrode, 106 ... Drain electrode, 107 ... Inorganic passivation film, 108 ... Organic passivation film, 109 ... Channel etching region, 110 ... Pixel electrode, 111 ... Reflective electrode, 112 ... Alignment film, 113 ... Contact hole, 120 ... Through hole, 130 ... Connection electrode, 150 ... End Sub-unit, 200 ... counter substrate, 201 ... color filter, 202 ... black matrix, 203 ... overcoat film, 204 ... step forming layer, 205 ... counter electrode, 300 ... liquid crystal layer, D1 ... first protection diode, D2 ... first 2 protection diodes.

Claims (10)

A TFT substrate having a display region and a frame region disposed around the display region, a counter substrate facing the TFT substrate, and a liquid crystal layer sandwiched between the TFT substrate and the counter substrate A liquid crystal display device,
The TFT substrate extends in the first direction, and is arranged in a second direction intersecting the first direction, and the scanning line extends in the second direction and is arranged in the first direction. Video signal lines,
In the display area, a pixel having a pixel electrode and an in-pixel TFT is formed in an area surrounded by the scanning line and the video signal line.
The frame region of the TFT substrate has a configuration in which a frame region pixel electrode and a frame region reflective electrode are formed to enable reflective display,
A protective diode that protects the in-pixel TFT is formed in the frame region, and the protective diode is formed by installing a connection electrode for the TFT formed by the same process as the in-pixel TFT. Has been
The protective diode partially overlaps the frame region reflective electrode through an insulating film,
A liquid crystal display device, wherein a through-hole is formed in the portion where the connection electrode is installed with respect to the frame region pixel electrode and the frame region reflection electrode.   The liquid crystal display device according to claim 1, wherein the protection diode is provided for the scanning line and the video signal line.   3. The liquid crystal according to claim 2, wherein a pitch of the through holes formed in the frame area pixel electrode and the frame area reflection electrode is equal to a pitch of the scanning lines or a pitch of the video signal lines. Display device.   The liquid crystal display device according to claim 1, wherein the connection electrode is formed of the same material as the pixel electrode.   The light shielding film is formed in the said opposing board | substrate in the position corresponding to the said through hole of the said frame area | region reflective electrode formed in the said frame area | region of the said TFT substrate. A liquid crystal display device according to any one of the above. A TFT substrate having a display region and a frame region disposed around the display region, a counter substrate facing the TFT substrate, and a liquid crystal layer sandwiched between the TFT substrate and the counter substrate A liquid crystal display device,
The TFT substrate extends in the first direction, and is arranged in a second direction intersecting the first direction, and the scanning line extends in the second direction and is arranged in the first direction. Video signal lines,
In the display area, a pixel having an in-pixel TFT is formed in an area surrounded by the scanning line and the video signal line.
The pixel includes a pixel electrode and includes a transmissive display region that controls transmitted light from a backlight, and a reflective display region that includes a reflective electrode and controls light from the outside.
The frame region of the TFT substrate has a configuration in which a frame region pixel electrode and a frame region reflective electrode are formed to enable reflective display,
A protective diode that protects the in-pixel TFT is formed in the frame region, and the protective diode is formed by installing a connection electrode for the TFT formed by the same process as the in-pixel TFT. Has been
The protective diode partially overlaps the frame region reflective electrode through an insulating film,
A liquid crystal display device, wherein a through-hole is formed in the portion where the connection electrode is installed with respect to the frame region pixel electrode and the frame region reflection electrode.   The liquid crystal display device according to claim 6, wherein the protection diode is provided for the scanning line and the video signal line.   The liquid crystal according to claim 7, wherein a pitch of the through holes formed in the frame region pixel electrode and the frame region reflective electrode is equal to a pitch of the scanning lines or a pitch of the video signal lines. Display device.   The liquid crystal display device according to claim 6, wherein the connection electrode is made of the same material as the pixel electrode.   10. The light-shielding film is formed on the counter substrate at a position corresponding to the through hole of the frame region reflective electrode formed in the frame region of the TFT substrate. A liquid crystal display device according to any one of the above.

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