JP2006010800A - Active matrix liquid crystal display device and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of iridescent unevenness on an LCD (liquid crystal display) panel by suppressing interference of light reflected with a pixel electrode in a reflective or transflective active matrix liquid crystal display device. <P>SOLUTION: The active matrix liquid crystal display device comprises a first insulating substrate 100 and a second insulating substrate 200 with a liquid crystal 12 sealed in between, wherein a pixel electrode 14 comprising a TFT 11 and a reflection layer is arranged on the first substrate 100. A plurality of recesses and protrusions are formed on a surface of the pixel electrode 14 on the side opposite to the liquid crystal 12. There is no periodicity of distance in intervals of mutually adjacent protrusions and those of mutually adjacent recesses. A common electrode 15 to which a common voltage Vcom is applied and a color filter layer 50 are formed on the second insulating substrate 200 placed opposite to the first insulating substrate 100. The liquid crystal 12 is driven with the voltage applied between the pixel electrode 14 and the common electrode 15 placed opposite thereto and interposing the liquid crystal 12 in between. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an active matrix liquid crystal display device and a manufacturing method thereof, and more particularly to an active matrix liquid crystal display device including a reflective electrode and a manufacturing method thereof.

  A liquid crystal display device (hereinafter referred to as an LCD) has a feature of being thin and has low power consumption, and is currently widely used as a monitor for a computer or a portable information device such as a mobile phone. There are transmissive LCDs and reflective LCDs. In the transmissive LCD, a transparent electrode is used as a pixel electrode for applying a voltage to the liquid crystal, a backlight light source is disposed behind the LCD panel, and the amount of light transmitted through the backlight is controlled by the LCD panel, thereby darkening the surroundings. Even bright display is possible. However, since the backlight light source is always turned on for display, power consumption is large, and there is a characteristic that a sufficient contrast cannot be secured in an environment with strong external light such as outdoors in the daytime.

  On the other hand, in a reflective LCD, external light such as sunlight or room light is used as a light source, and the external light incident on the LCD panel is reflected by a pixel electrode including a reflective layer formed on a substrate on the observation surface side. Then, display is performed by controlling the amount of light emitted from the LCD panel of light incident on the liquid crystal and reflected by the reflective layer for each pixel. Since this reflective LCD uses external light as the light source, it cannot be displayed in an environment without external light. However, unlike a transmissive LCD, it has low power consumption and no external light. Has a characteristic that a sufficient contrast can be obtained.

  In recent years, transflective LCDs have been developed as LCDs that have both a transmissive function and a reflective function, and are easy to see in both bright and dark environments. In this transflective LCD, a transparent electrode such as ITO is used in one pixel in order to realize a transmission function, and a pixel electrode including a reflective layer having a good reflection characteristic such as Al is used in order to realize a reflection function.

As described above, reflective LCDs and transflective LCDs include pixel electrodes including a reflective layer. However, in order to scatter external light in various directions and prevent specular reflection at the reflective layer, the pixel electrodes A surface in which a plurality of concave portions and convex portions are formed using a mask is known.
JP-A-5-325586 JP 2003-255375 A

  However, when the external light is reflected by the reflective layer because the pattern of the plurality of concave portions and convex portions formed on the surface of the pixel electrode including the reflective layer has periodicity in the distance as described above. In addition, there is a problem that interference of reflected light occurs and rainbow-like display unevenness occurs.

  The present invention provides an active matrix liquid crystal display device having a pixel electrode including a reflective layer, such as a reflective LCD or a transflective LCD, in which a plurality of concave portions and convex portions are formed on the surface of the pixel electrode and are adjacent to each other. There is no distance periodicity in the interval between the convex portions and the interval between the concave portions adjacent to each other.

  According to the present invention, in an active matrix type liquid crystal display device having a pixel electrode including a reflective layer, interference of reflected light by the pixel electrode is suppressed, so that rainbow-like unevenness is prevented from being generated on the LCD panel. The quality can be improved.

  Next, an active matrix liquid crystal display device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an equivalent circuit of four pixels of this active matrix type liquid crystal display device. FIG. 2 is a pattern layout diagram of the pixel of FIG. Although FIG. 1 and FIG. 2 show four pixels, in practice, a large number of pixels are arranged in a matrix of rows and columns to form a pixel region.

  The plurality of data lines 10 extend in the column direction, and the plurality of gate lines 20 extend in the row direction intersecting therewith. Each pixel includes a pixel selecting thin film transistor 11 (hereinafter referred to as TFT 11) connected to the data line 10 and the gate line 20. When the TFT 11 is turned on in accordance with a pixel selection signal output to the gate line 20, display data is supplied from the data line 10 to the pixel electrode 14 of the liquid crystal 12 through the TFT 11. A common voltage Vcom is supplied to a common electrode 15 (also referred to as a counter electrode) facing the pixel electrode 14 via the liquid crystal 12.

  In addition, it is necessary to securely hold the display data written in the pixel during the period from when the TFT 11 is selected according to the pixel selection signal and the display data is written into the pixel until the TFT 11 is next selected again. Therefore, the auxiliary capacitance element 13 is provided. The first terminal 13 a of the auxiliary capacitance element 13 is connected to the source region 61 s of the TFT 11 and the pixel electrode 14, and the second terminal 13 b is connected to the auxiliary capacitance line 30. A constant voltage Vsc is supplied to the auxiliary capacitance line 30.

  FIG. 3 shows a cross-sectional structure of the pixel at a position along the line XX in FIG. This pixel is a pixel of a reflective LCD, and has a configuration in which a liquid crystal 12 is sealed between a first insulating substrate 100 and a second insulating substrate 200. A TFT 11 and an aluminum layer are formed on the first substrate 100. A pixel electrode 14 including a reflective layer such as is disposed. As will be described later, a plurality of concave portions and convex portions are formed on the surface of the reflective layer on the side facing the liquid crystal 12 of the pixel electrode 14, and the distance between the convex portions adjacent to each other and the interval between the concave portions adjacent to each other. There is no periodicity. A common electrode 15 to which a common voltage Vcom is applied and a color filter layer 50 are formed on a second insulating substrate 200 that is disposed opposite to the first insulating substrate 100. Then, the liquid crystal 12 is driven by a voltage applied between the pixel electrode 14 and the common electrode 15 facing the liquid crystal 12 therebetween.

  Hereinafter, this cross-sectional structure will be described in more detail. A TFT 11 is formed on the first insulating substrate 100, and a so-called top gate type TFT in which the gate electrode 20 a is located above the active layer 61. The active layer 61 of the TFT 11 is made of polysilicon and is patterned on the first substrate 100. A gate insulating layer 62 is formed to cover the active layer 61, and a gate electrode 20 a that is a part of the gate line 20 is formed on the gate insulating layer 62. The portion of the active layer 61 below the gate electrode 20a is a channel region 61c of the TFT 11, and a drain region 61d and a source region 61s into which impurities are implanted are formed on both sides of the channel region 61c.

  The drain region 61d of the active layer 61 is connected to the data line 10 via a connection metal layer embedded in a contact hole H1 formed in the interlayer insulating layer 65 formed to cover the gate electrode 20a.

  Further, a planarization insulating layer 70 is formed so as to cover the data line 10, and the source region 61 s of the active layer 61 has a contact hole and a pixel electrode 14 including a reflective layer formed on the planarization insulating layer 70. They are connected via a connection metal layer embedded in H2.

  The source region 61s of the active layer 61 also serves as the first terminal 13a of the auxiliary capacitance element 13 provided in each pixel. As shown in FIG. 2, the auxiliary capacitance is further increased from the contact region with the pixel electrode 14. It extends to a region overlapping with the line 30. The second terminal 13b of the auxiliary capacitance element 13 is integrated with the auxiliary capacitance line 30, and is formed in the same process and in the same layer as the gate electrode 20a. The auxiliary capacitance line 30 is formed in a different region from the gate electrode 20a and the gate line 20 with a predetermined gap. The gate insulating layer 62 is also used as the capacitive insulating film of the auxiliary capacitive element 13.

  A first alignment film 81 for aligning the liquid crystal 12 is formed on the pixel electrode 14 formed with a plurality of recesses and projections having no periodicity in distance and on the planarization insulating layer 70. A second alignment film 82 for aligning the liquid crystal 12 is also formed under the common electrode 15 facing the pixel electrode 14 via the liquid crystal 12.

FIG. 4 is an enlarged cross-sectional view showing a plurality of concave portions and convex portions formed on the surface of the reflective layer on the side facing the liquid crystal 12 of the pixel electrode 14. Intervals A1, A2, A3 between adjacent convex portions
.. And intervals B1, B2, B3,... Between adjacent recesses have no distance periodicity. That is, these intervals are completely irregular, and there is no short-range regularity and long-distance regularity. This also applies to the pixel electrodes 14 of all other pixels.

  Accordingly, since external light such as sunlight is irregularly reflected by the pixel electrode 14, interference between the reflected lights is suppressed and rainbow-like unevenness is prevented from being generated on the LCD panel. Further, the intervals A1, A2, A3,... Between the adjacent convex portions and the intervals B1, B2, B3,... Between the adjacent concave portions are greater than 0 μm and distributed within a range of 10 μm or less. Is preferred. Further, the height h of the convex portion and the depth d of the concave portion are preferably distributed in a range of ± 1 μm with reference to the average height Hav of the surface of the reflective layer of the pixel electrode 14.

  Here, the height h of the convex portion is a height based on the average height Hav of the surface of the reflective layer of the pixel electrode 14, and the depth d of the concave portion is the height of the surface of the reflective layer of the pixel electrode 14. The depth is based on the average height Hav. Further, it is preferable that the intervals A1, A2, A3,... Between the adjacent convex portions and the intervals B1, B2, B3,.

  In the manufacturing method of the active matrix liquid crystal display device, the planarization insulating layer 70 made of a photosensitive insulating material or the like is deposited on the first insulating substrate 100 on which the TFT 11 is formed, and then aluminum (Al) or A metal layer such as silver (Ag) is sputtered to form a metal layer, and the surface of the metal layer is polished with a large number of particles (for example, fine particles of cerium oxide) to form a plurality of concave and convex portions. Form. According to this particle polishing, a plurality of concave portions and convex portions having no distance periodicity are formed. Thereafter, the particle-polished metal layer is patterned to form the reflective layer 14a. Thereafter, the transparent electrode 14b is formed on the reflective layer 14a, and the pixel electrode 14 is formed. Note that the pixel electrode 14 may be formed only by the reflective layer 14a without forming the transparent electrode 14b.

  As shown in FIG. 5, another manufacturing method of the active matrix liquid crystal display device described above covers a planarizing insulating layer 70 made of a photosensitive insulating material or the like on a first insulating substrate 100 on which a TFT 11 is formed. After the deposition, the surface of the planarization insulating layer 70 is subjected to particle polishing by the same method as described above to form a plurality of concave portions and convex portions.

  Then, a metal layer is formed by sputtering a metal such as aluminum (Al) or silver (Ag) on the planarized insulating layer 70 subjected to particle polishing. Then, a plurality of concave portions and convex portions that reflect the shape of the surface of the planarization insulating layer 70 as they are are formed on the surface of the metal layer. Since the plurality of recesses and projections on the surface of the planarization insulating layer 70 do not have distance periodicity, the plurality of recesses and projections reflected as they are on the surface of the metal layer naturally have distance periodicity. Absent. Thereafter, the metal layer is patterned to form the reflective layer 14a. Thereafter, the transparent electrode 14b is formed on the reflective layer 14a, and the pixel electrode 14 is formed. Note that the pixel electrode 14 may be formed only by the reflective layer 14a without forming the transparent electrode 14b.

  Next, an active matrix liquid crystal display device according to a second embodiment of the present invention will be described with reference to the drawings. Although the reflective LCD has been described in the first embodiment, the present embodiment relates to a transflective LCD. FIG. 6 is a layout pattern diagram of pixels of the active matrix liquid crystal display device, and FIG. 7 shows a cross-sectional structure of the pixel at a position along the line YY in FIG. Note that an equivalent circuit diagram of a pixel of the active matrix liquid crystal display device is the same as that shown in FIG.

  This active matrix liquid crystal display device includes a reflective region and a transmissive region in one pixel. The reflective area functions as a reflective LCD, and the transmissive area functions as a transmissive LCD. When this embodiment is compared with the first embodiment, the structures of the pixel electrodes 14 are different from each other. The pixel electrode 14 of the present embodiment includes a reflective layer 14a and a transparent electrode 14b. In the reflective region, the reflective layer 14a is formed on the planarizing insulating layer 70, and is formed of a transparent conductive layer such as ITO on the reflective layer 14a. A transparent electrode 14b is formed. The transparent electrode 14b is formed so as to extend from the reflection region onto the planarization insulating layer 70 in the transmission region.

  Since such a transflective LCD also includes the reflective layer 14a, when external light is reflected by the reflective layer 14a, interference of the reflected light occurs and rainbow-like unevenness occurs. Therefore, as in the first embodiment, by forming a plurality of concave portions and convex portions having no periodicity in distance on the surface of the reflective layer 14a in the reflective region, occurrence of such rainbow-shaped unevenness is prevented. be able to. The reflective layer 14a may be formed on the transparent electrode 14b.

  The active matrix type liquid crystal display device of this embodiment can be manufactured in the same manner as in the first embodiment. That is, after the planarization insulating layer 70 made of a photosensitive insulating material or the like is deposited on the first insulating substrate 100 on which the TFT 11 is formed, a metal such as aluminum (Al) or silver (Ag) is sputtered. Then, a metal layer is formed, and the surface of the metal layer is subjected to particle polishing using a large number of particles (for example, cerium oxide fine particles) to form a plurality of concave portions and convex portions. According to this particle polishing, a plurality of concave portions and convex portions having no distance periodicity are formed. Thereafter, the particle-polished metal layer is patterned to form the reflective layer 14a only in the reflective region. Thereafter, a transparent electrode 14b extending from the reflective layer 14a to the transmissive region is formed.

  In another method of manufacturing the active matrix liquid crystal display device, the flattening insulating layer 70 made of a photosensitive insulating material or the like is deposited on the first insulating substrate 100 on which the TFT 11 is formed, and then the flattening is performed. The surface of the insulating insulating layer 70 is subjected to particle polishing to form a plurality of recesses and protrusions, and a metal such as aluminum (Al) or silver (Ag) is sputtered onto the planarized insulating layer 70 subjected to particle polishing. To form a metal layer.

  Then, a plurality of concave portions and convex portions that reflect the shape of the surface of the planarization insulating layer 70 as they are are formed on the surface of the metal layer. Since the plurality of recesses and projections on the surface of the planarization insulating layer 70 do not have distance periodicity, the plurality of recesses and projections reflected as they are on the surface of the metal layer naturally have distance periodicity. Absent. Thereafter, the metal layer is patterned to form the reflective layer 14a. Thereafter, a transparent electrode 14b extending from the reflective layer 14a to the transmissive region is formed.

4 is an equivalent circuit of four pixels of the active matrix liquid crystal display device according to the first embodiment of the present invention. FIG. 3 is a pattern layout diagram of the pixel of FIG. 1 in FIG. 2. It is sectional drawing of the pixel in the position along the XX line of FIG. 2 is an enlarged cross-sectional view of the vicinity of the surface of a pixel electrode 14. FIG. FIG. 4 is another cross-sectional view of a pixel at a position along the line XX in FIG. 2. FIG. 6 is a pattern layout diagram of pixels of an active matrix liquid crystal display device according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view of a pixel at a position along line XX in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Data line 11 TFT 12 Liquid crystal 13 Auxiliary capacity element 13a 1st terminal 13b 2nd terminal 14 Pixel electrode 14a Reflective layer 14b Transparent electrode 15 Common electrode 20 Gate line 20a Gate electrode 30 Auxiliary capacity line 50 Color filter layer 61 Active layer 61d drain region 61c channel region 61s source region 62 gate insulating layer 65 interlayer insulating layer 70 planarizing insulating layer 81 first alignment film 82 second alignment film 100 first insulating substrate 200 second insulating substrate

Claims (9)

A plurality of pixels, each pixel being a thin film transistor disposed on an insulating substrate;
A pixel electrode including a reflective layer to which a display signal is applied through the thin film transistor;
A transparent common electrode disposed facing the pixel electrode;
A liquid crystal sealed between the pixel electrode and the common electrode, wherein a plurality of concave portions and convex portions are formed on the surface of the reflective layer of the pixel electrode, and the interval between the convex portions adjacent to each other and the concave portions adjacent to each other. An active matrix liquid crystal display device characterized in that there is no distance periodicity in the interval. 2. The active matrix liquid crystal display device according to claim 1, wherein the interval between the adjacent convex portions and the interval between the adjacent concave portions are distributed in a range from 0 μm to 10 μm. 3. The height of the convex portion and the depth of the concave portion are distributed in a range of ± 1 μm with reference to an average height of the surface of the reflective layer of the pixel electrode. The active matrix liquid crystal display device described. 3. The active matrix type liquid crystal display device according to claim 1, wherein the interval between the convex portions adjacent to each other and the interval between the concave portions adjacent to each other form a normal distribution. 4. The active matrix liquid crystal display device according to claim 1, wherein the height difference between the concave portion and the convex portion has a normal distribution. A plurality of pixels, each pixel being a thin film transistor disposed on an insulating substrate;
An insulating layer formed on the thin film transistor;
A pixel electrode formed on the insulating layer and including a reflective layer to which a display signal is applied through the thin film transistor;
A transparent common electrode disposed facing the pixel electrode;
A method of manufacturing an active matrix liquid crystal display device comprising a liquid crystal sealed between the pixel electrode and the common electrode,
The surface of the insulating layer is polished using a number of particles to form a plurality of concave portions and convex portions, and then the pixel electrode is formed by depositing a metal layer on the insulating layer, and the pixel electrode In the active matrix liquid crystal display device, a plurality of recesses and projections are formed on the surface of the reflective layer reflecting the plurality of recesses and projections formed on the surface of the insulating layer. Production method. A plurality of pixels, each pixel being a thin film transistor disposed on an insulating substrate;
An insulating layer formed on the thin film transistor;
A pixel electrode formed on the insulating layer and including a reflective layer to which a display signal is applied through the thin film transistor;
A transparent common electrode disposed facing the pixel electrode;
A method of manufacturing an active matrix type liquid crystal display device comprising a liquid crystal sealed between the pixel electrode and the common electrode,
An active matrix liquid crystal display device, wherein the pixel electrode is formed on the insulating layer, and the surface of the reflective layer of the pixel electrode is polished with a large number of particles to form a plurality of concave portions and convex portions. Manufacturing method. 8. The method of manufacturing an active matrix liquid crystal display device according to claim 6, wherein the pixel electrode is formed by sputtering metal. 9. The method of manufacturing an active matrix liquid crystal display device according to claim 8, wherein the metal is aluminum or silver.

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