JP2007264304A - Transflective liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the reflection efficiency etc., of a transflective liquid crystal display device. <P>SOLUTION: A reflecting plate 16 is arranged on a pixel substrate 100 to form a reflection region. Further, a contact 20 which connects a pixel electrode 18 and a TFT of a TFT layer 12 to each other is arranged in a boundary region between the reflection region and a transmission region. A projection part 32 is provided in a reflection region on a counter substrate 300, and at a circumference of the projection part, a black matrix 34 is provided including the boundary region between the reflection region and transmission region. Consequently, improper reflection in the boundary region can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transflective liquid crystal display device having a transmissive region that transmits light from the back surface side and a reflective region that reflects light from the observation side.

  There are two types of liquid crystal display devices: a transmissive type that transmits light from the backlight on the back to the liquid crystal layer, a reflective type that reflects external light through the liquid crystal layer, and a transflective type that has both a transmissive region and a reflective region. .

  Here, in the transmissive type, light from the backlight passes through the liquid crystal layer only once, but in the reflective type, external light passes through the liquid crystal layer twice. For this reason, if the thickness of the liquid crystal layer is constant in the transflective type, the display characteristics differ between the reflective region and the transmissive region. Accordingly, a configuration is known in which the thickness of the liquid crystal layer in the reflective region is halved compared to the thickness of the transmissive region. For example, it is shown in patent document 1.

JP 2003-255399 A

  In the prior art, a protrusion is provided in the reflection region. The boundary of the protrusion has a slope that is substantially vertical or nearly perpendicular. When rubbing for aligning the liquid crystal, the manner in which the rubbing cloth strikes the inclined portion changes, and alignment failure (disclination) occurs. This lowers the display quality (contrast).

  In the case of a transflective liquid crystal, the contrast of the transmissive part is as high as 100 or more, and the reflection part is as low as about 20; Therefore, such a disclination part is used as a reflection part, and the boundary between the transmission part and the reflection part is set so as not to occur in the transmission part. Specifically, a reflective electrode is provided on the substrate side corresponding to a portion where disclination occurs, and is used as a reflective portion. However, since the portion has no protrusion, the cell gap is not a desired value as the optical characteristic of reflection. As a result, the optical characteristics are degraded. In addition to this defect, considering that there is a misalignment between the pixel substrate and the counter substrate, in order to prevent the disclination part from entering the transmissive part, up to the part including the misalignment (cell gap) It was necessary to set it as a reflection part).

  For this reason, the reflection optical characteristic is lowered by increasing the area where the cell gap occupied in the reflection part is not a desired value, and the transmission optical characteristic (luminance) is lowered by lowering the aperture ratio of the transmission part. There was a problem.

  A liquid crystal is arranged between a pixel substrate in which pixel electrodes formed for each pixel are arranged in a matrix and a counter substrate provided with a counter transparent electrode, and display is performed by controlling voltage application to the pixel electrode. And a transflective liquid crystal display device having a transmissive region that transmits light from the back side and a reflective region that reflects light from the observation side in each pixel, wherein each pixel of the pixel substrate includes the reflective layer A pixel circuit that is located in the region and controls voltage application to the pixel electrode; a reflector that covers at least a part of the pixel circuit; and a reflector that is formed on the reflector and has no reflector And a pixel electrode located in both the transmissive region and the reflective region. The reflective region of each pixel of the counter substrate is provided with a protrusion for reducing the thickness of the liquid crystal layer. , And the stepped surface of this protrusion That and forming a black matrix for preventing transmission of light in the vicinity of the boundary between the reflective region and the transmissive region.

  The pixel circuit and the pixel electrode are connected by a contact, and the contact is arranged at a position corresponding to the black matrix in the vicinity of the reflective region and the transmissive region.

  In the present invention, by disposing a black matrix in the boundary region between the reflective region and the transmissive region, it is possible to effectively prevent an undesirable display from occurring in the boundary region, and thereby the optical in the reflective region. Characteristics (reflectance, contrast) are improved. In particular, when a design margin due to an error in attaching the pixel substrate and the counter substrate is taken into consideration, the reflector is made larger in the boundary region between the transmissive region and the reflective region. The light can be reliably shielded by the matrix, and there is no need to consider the design margin, and the transmission region can be made sufficiently large.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

“Embodiment 1”
FIG. 1 is a cross-sectional view showing the configuration of one pixel of a transflective liquid crystal display device according to Embodiment 1 of the present invention.

  The pixel substrate 100 includes a glass substrate 10, and a TFT layer 12 is provided on the glass substrate 10, and a switching TFT (not shown) is provided for each pixel. The switching TFT is connected to a gate line extending in the row direction at the gate, and is turned on / off by the gate line. When the switching TFT is turned on, the data voltage on the data line is held in the holding capacitor, and this data voltage is applied to the liquid crystal of the pixel via the pixel electrode.

  A planarization film 14 is formed on the TFT layer 12. For the planarizing film 14, for example, an acrylic resin is employed. A reflective plate 16 is formed in the reflective region on the planarizing film 14. The reflector 16 is made of a metal such as aluminum, an aluminum alloy, or silver.

  Further, a pixel electrode 18 made of a transparent conductor is formed so as to cover the entire reflection region and transmission region of the pixel. The pixel electrode 18 is made of ITO (indium tin oxide), IZO (indium zinc oxide), or the like.

  A contact 20 is provided in a boundary region between the reflection region and the transmission region. The contact 20 is formed by inserting a transparent conductor for forming the pixel electrode 18 into a contact hole that penetrates the planarizing film 14, and thereby the switching TFT and the storage capacitor of the TFT layer 12, and the pixel electrode 18. Are electrically connected.

  Opposing the pixel substrate 100, the counter substrate 300 is provided through the liquid crystal layer 200. The counter substrate 300 has a glass substrate 30, and a protrusion 32 is formed in a reflective region on the back surface thereof. The protrusion 32 is made of, for example, the same material (such as acrylic resin) as the above-described planarization film 14.

  Further, a black matrix 34 that covers the gaps between the pixels and the outer periphery of each pixel is also formed. The black matrix 34 may be a metal type such as black chrome or a resin type. Then, a counter electrode 36 made of a transparent conductor is formed so as to cover the entire surface including the protrusion 32 and the black matrix 34 of the counter substrate. The counter electrode 36 is also formed of ITO, IZO or the like, like the pixel electrode.

  In the present embodiment, the black matrix 34a is disposed in the boundary region between the reflective region and the transmissive region. This avoids undesirable display in the border region.

  Here, the protrusion 32 of the counter substrate 300 is formed only in the reflection region, but the periphery thereof is slightly inclined. This slope portion changes the way the rubbing cloth is applied during the rubbing process, and therefore orientation failure (disclination) occurs. In addition, the pixel substrate 100 and the counter substrate 300 are bonded to each other after fabrication. Therefore, there is a bonding error, and it is inevitable that the positional relationship between the area where the protrusions 32 are located and the area where the reflector 16 is located are slightly shifted. As for the peripheral area of the pixel, there is no problem because the black matrix 34 is originally arranged for separation from other pixels. However, the boundary area between the reflective area and the transmissive area inside the pixel is not a problem. In many cases, the display is not set correctly depending on the reflection area and the transmission area, and normal display is difficult to be performed.

  In the present embodiment, by disposing the black matrix 34a in such a boundary region, it is possible to effectively prevent an undesirable display from occurring in this boundary region, and to improve the optical characteristics (reflectance, contrast) in the reflection region. Will improve.

  In particular, when a design margin due to a bonding error between the pixel substrate 100 and the counter substrate 300 is taken into consideration, the reflector 16 is enlarged in the boundary region between the transmissive region and the reflective region. With the black matrix 34a, the disclination portion generated under the step boundary portion of the counter substrate can be reliably shielded from light by the black matrix 34a, and there is no need to consider the design margin. Can be of any size.

  Furthermore, since the contact 20 is also arranged in the same boundary region, the contact 20 and the black matrix 34 overlap as a planar position. Therefore, the contact 20 is hidden by the black matrix 34 in the boundary region. The surface of the contact is uneven, and desired reflection is not performed on this surface. By keeping this portion light-shielded by the black matrix 34a, undesirable reflection can be prevented.

  FIG. 2 is a diagram showing a planar layout for the TFT layer 12. The data line DL is arranged in the vertical direction corresponding to each column of pixels, and the gate line GL is arranged in the horizontal direction corresponding to each row of pixels. One end of the pixel is connected to the data line DL, extends through the gate line GL along the data line DL, and then makes a U-turn to pass through the gate line GL again. A semiconductor layer SF extending to about half of the pixels is provided. A contact is provided in a portion of the semiconductor layer SF after passing through the gate line GL for the second time, and a metal pad MP is connected through the contact. The metal pad MP has substantially the same planar shape as the semiconductor layer SF arranged from the contact toward the center of the pixel. Further, the SC line SC is similarly overlapped at the same position as the metal pad MP, and the SC line SC is also overlapped. In this part, the wiring has a three-layer structure of the semiconductor layer SF, the SC line SC and the metal pad MP. It has become. A contact 20 is disposed at a portion of the metal pad MP located at the center of the pixel.

  A portion where the semiconductor layer SF passes through the gate line constitutes a double gate type switching TFT, and a portion where the semiconductor layer SF and the SC line SC overlap constitutes a storage capacitor Cs.

  FIG. 3 shows an XX cross-sectional view including the pixel electrode 18 in the storage capacitor Cs and the contact 20 from the second gate portion of the switching TFT SW.

  On the glass substrate 10, a semiconductor layer SF made of polysilicon or amorphous silicon is patterned, and a gate insulating film 50 made of a laminated layer of silicon oxide and silicon nitride is provided so as to cover the semiconductor layer SF. On the gate insulating film 50, gate lines GL and SC lines made of molybdenum or chromium are arranged. An interlayer insulating film 52 having a laminated structure of silicon nitride and silicon oxide is disposed.

  A data line DL and the like are disposed on the interlayer insulating film 52, but a metal pad MP is disposed as shown in the drawing. The end of the metal pad MP is connected to the semiconductor layer SF on the storage capacitor Cs side of the switching TFT by a contact penetrating the interlayer insulating film 52.

  A planarizing film 14 is formed to cover the metal pad MP and the interlayer insulating film 52, and a reflecting plate 16 and a pixel electrode 18 are formed thereon. Further, the pixel electrode 18 and the metal pad MP are connected by the contact 20 penetrating the planarizing film 14. The position of the contact 20 is located in the boundary area between the reflection area and the transmission area in the center of the pixel.

  FIG. 3 is a diagram schematically showing the scale in the thickness direction plane direction and the like, which are completely different from actual ones.

It is a figure which shows the structure for 1 pixel of the display apparatus which concerns on embodiment. It is a figure which shows the layout of a TFT layer. It is a figure which shows the cross-sectional structure of a TFT layer.

Explanation of symbols

  10, 30 glass substrate, 12 TFT layer, 14 planarization film, 16 reflector, 18 pixel electrode, 20 contacts, 30 glass substrate, 32 protrusion, 34, 34a black matrix, 36 counter electrode, 50 gate insulating film, 52 Interlayer insulating film, 100 pixel substrate, 200 liquid crystal layer, 300 counter substrate, Cs storage capacitor, DL data line, GL gate line, MP metal pad, SC line, SF semiconductor layer, SW switching TFT.

Claims (2)

A liquid crystal is arranged between a pixel substrate in which pixel electrodes formed for each pixel are arranged in a matrix and a counter substrate provided with a counter transparent electrode, and display is performed by controlling voltage application to the pixel electrode. And a transflective liquid crystal display device having a transmissive region that transmits light from the back side and a reflective region that reflects light from the observation side in each pixel,
Each pixel of the pixel substrate is
A pixel circuit that is located in the reflective region and controls voltage application to the pixel electrode;
A reflector formed to cover at least a part of the pixel circuit;
A pixel electrode that is formed on the reflector and is also formed in a region where the reflector is not present, and is located in both the transmissive region and the reflective region;
Have
The reflective area of each pixel of the counter substrate is provided with a protrusion for reducing the thickness of the liquid crystal layer, and prevents light from being transmitted in the vicinity of the boundary between the reflective area and the transmissive area that forms the stepped surface of the protrusion. A transflective liquid crystal display device characterized by forming a black matrix. The transflective liquid crystal display device according to claim 1,
The pixel circuit and the pixel electrode are connected by a contact, and the contact is disposed at a position corresponding to the black matrix in the vicinity of the reflective region and the transmissive region. apparatus.

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