JP2006098757A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display with high display quality by preventing the reflectance from lowering. <P>SOLUTION: A liquid crystal panel 40 is constituted, by placing an array substrate 50 and a color filter substrate 30 opposite to each other with a liquid crystal material 20 interposed in between, and is equipped with a plurality of pixels. On the array substrate 50, a thin-film transistor 4 formed for each pixel, a transmission electrode 11, a planarizing film 6 formed between the thin-film transistor 4 and the transmission electrode 11, and a contact pad 8 formed on a recessing section penetrating the planarizing film 6 and connecting the thin-film transistor 4 and the transmission electrode 11 to each other are formed. The color filter substrate 30 is equipped with a common electrode 32 and a protruding portion 34, formed at the position of the common electrode 32 facing the contact pad 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device having a contact portion that electrically connects a semiconductor layer having a reflection portion that reflects external light and a pixel electrode. More specifically, the contact portion has a step. The present invention relates to a liquid crystal display device in which the cell gap of the liquid crystal layer is different between the inner peripheral portion and the peripheral portion of the contact portion.

  In recent years, the application of liquid crystal display devices has rapidly spread not only in information communication equipment but also in general electric equipment. In particular, for the portable type, a reflective liquid crystal display device that reflects an external light and displays an image without using a backlight is used in order to reduce power consumption. Since the device uses external light as a light source, it is difficult to see in a dark room. Thus, in recent years, transflective liquid crystal devices having both transmissive and reflective properties have been developed.

  This transflective liquid crystal display device has a transmissive part with a transmissive electrode and a reflective part with a reflective film in one pixel, and the backlight is turned on in a dark place to transmit the light. Since the image is displayed using the transmitting part and the image is displayed using the external light in the reflecting part without turning on the backlight in a bright outdoor environment, the power consumption can be greatly reduced. Have.

  An array substrate of a conventional transflective liquid crystal display device (see Patent Document 1) will be described with reference to a plan view of FIG. 4 and a cross-sectional view taken along line XX of FIG. 4 in FIG.

  On the glass substrate 101, a gate electrode G and an auxiliary capacitance electrode Cs are arranged for each pixel, and the entire glass substrate 101 including the surface thereof is covered with a gate insulating film 102 made of a silicon nitride film or a silicon oxide film. Next, an active layer 103, a drain electrode D, and a source electrode S1 are sequentially formed around the gate electrode G to form a MOS-type thin transistor element 104 (hereinafter referred to as a TFT element 104) as a switching element.

  Then, a protective film 105 made of a silicon oxide film or a silicon nitride film is formed so as to cover the TFT element 104, and an interlayer film 106 made of a scattering layer or a planarizing film is formed on the protective film 105. The protective film 105 and the interlayer film 106 are provided with a contact hole 107 for electrical connection between the transmissive electrode 111 as a pixel electrode and the source electrode S1 above the source electrode S1 of the TFT element 104. A groove portion from which the interlayer film 106 is removed is provided at a location away from 104. This groove corresponds to the transmission part 109.

  A transmissive electrode 111 is laminated on the protective film 105 and the interlayer film 106. ITO (Indium-Tin-Oxide) is laminated on the entire pixel as a material of the transmissive electrode 111, and a material for the reflective film 110 is laminated on a portion of the transmissive electrode 111 excluding the transmissive portion 109. A portion where the reflection film 110 is laminated is a reflection portion 112. In the illustrated example, expensive Ag is used as the material of the reflective film 110 instead of Al which is generally widely used. The reason is that ITO and Al do not form an ohmic contact unless Ti is interposed between them, and therefore a Ti film forming step is required. However, ITO and Ag form a good ohmic contact, so the number of steps is small. This is because. The transmissive electrode 111 is electrically connected to the source electrode S1 at the contact hole 107 portion.

  A color filter substrate 130 is disposed facing the array substrate 100, and a liquid crystal material 120 is sandwiched between the array substrate 100 and the color filter substrate 130 (cell gap). Columnar spacers 133 are formed on the color filter substrate 130 so that the cell gap is uniform in each of the regions of the reflection portion 112 and the transmission portion 109.

  In the color filter substrate 130, a common electrode 132 made of a color filter or ITO is formed on a glass substrate 131. The array substrate 100, the color filter substrate 130, the liquid crystal material 120, and the like constitute a liquid crystal panel 140.

Although not shown below the array substrate 100, a backlight device having a well-known light source, light guide plate, diffusing sheet, and the like is disposed, and transmitted light transmitted from the backlight device passes through the transmission unit 109 and is externally transmitted. The light is reflected by the reflecting portion 112. The array substrate 100 having the transmissive portion 109 and the reflective portion 112 in the same pixel, the liquid crystal material 120, the color filter substrate 130, the backlight device, and the like are combined to form a transflective liquid crystal display device.
JP 2004-144965 A

  The cell gap dr in the region of the reflective portion 112 is the best at which the reflectance of the external light incident from the color filter substrate 130 side is the largest, depending on conditions such as the type of the liquid crystal material 120 and the drive voltage applied between the electrodes 111 and 132. The interval is set to be.

  However, the contact hole 107 is a recess as shown in FIG. 5, and the cell gap dc2 in this portion is approximately twice as long as dr. For this reason, the retardation value (Δn · d (Δn is refractive index anisotropy, d is cell gap)) is different in the contact hole 107 portion, and the reflectance is lowered in the contact hole 107 portion. It turns out that quality falls.

  In view of the above problems, an object of the present invention is to provide a liquid crystal display device devised so as not to cause a decrease in reflectivity at the contact hole 107 portion.

  The first invention of the present invention is configured such that two substrates (array substrate 50 and color filter substrate 30) each having an electrode for driving a liquid crystal on the opposite surface side are opposed to each other with a liquid crystal layer (liquid crystal material 20) interposed therebetween. A liquid crystal display device (liquid crystal panel 40) having a plurality of pixels, on one side of the substrate (array substrate 50), a thin film transistor (TFT element 4) formed for each pixel and a pixel electrode ( The transmissive electrode 11), an interlayer film (planarization film 6) formed between the thin film transistor and the pixel electrode, and the thin film transistor formed in a recess (contact hole 7) penetrating the interlayer film (planarization film 6) And a contact portion (contact pad 8) for connecting the pixel electrode and a counter electrode (common electrode 32) and a counter electrode (common electrode 32) on the other side (color filter substrate 30) of the substrate. A liquid crystal display device (liquid crystal panel 40) comprising a protrusion (protrusion 34) formed at a position facing the contact portion (contact pad 8) of the pole 32).

  In another aspect of the present invention, in the first invention, the protrusion (protrusion 34) includes a cell gap (dr) around the contact (contact pad 8) and a gap between the contact and protrusion. The liquid crystal display device (liquid crystal panel 40) is characterized in that the cell gap (dc1) is formed at a height that is substantially the same.

  In another aspect of the present invention, in the first invention, the protrusion (protrusion 34) is substantially the same length as the depth (dc1) of the recess (contact hole 7) of the contact (contact pad 8). The liquid crystal display device (liquid crystal panel 40) is characterized in that a height (h) is formed on the liquid crystal display device.

  In another aspect of the present invention, in the first invention, the pixel electrode (transmissive electrode 11) is a reflective region (reflecting portion 12) that reflects light incident from the other substrate (color filter substrate 30). ), And the contact portion (contact pad 8) is formed in the reflective region (reflective portion 12). This is a liquid crystal display device (liquid crystal panel 40).

  In another aspect of the present invention, in the first invention, a reflective region (reflecting portion 12) that reflects light incident from the other substrate (color filter substrate 30) superimposed on the pixel electrode (transmissive electrode 11). ) And a transmissive region (transmissive portion 9) that transmits light incident from the other substrate (color filter substrate 30), and the contact portion (contact pad 8) is located in the reflective region (reflective portion). The liquid crystal display device (liquid crystal panel 40) is characterized by being formed.

  In another aspect of the present invention, in the first invention, the contact portion (contact pad 8) may interfere with a counter electrode (common electrode 32) formed on the protrusion (protrusion 34) (contact pad). The liquid crystal display device (liquid crystal panel 40) is characterized in that the punching portion 14) is removed.

  In another aspect of the present invention, a columnar spacer (columnar spacer 33) that maintains a constant cell gap (dr) between the two substrates (array substrate 50, color filter substrate 30) is provided, and the columnar spacer (columnar spacer) is provided. 33) is a liquid crystal display device formed by the same process as that of the projection (projection 34). .

  According to the present invention, in a liquid crystal display device, it is possible to provide a liquid crystal display device with high display quality by preventing a decrease in reflectance.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings. 1 is a schematic plan view of a liquid crystal display device, FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a diagram showing another embodiment of a contact hole portion.

An active layer 3 made of a polysilicon film is formed on the glass substrate 1, and the entire glass substrate 1 including its surface is covered with a gate insulating film 2 made of a silicon nitride film or a silicon oxide film. A gate electrode G and an auxiliary capacitance electrode Cs are disposed at a portion overlapping the active layer 3. The drain electrode D, source electrode S1 and gate electrode G of the active layer 3 form a MOS type thin transistor element 4 (hereinafter referred to as TFT element 4) which is a switching element.
An interlayer insulating film 5 made of a silicon oxide film or a silicon nitride film is formed so as to cover the TFT element 4, and a planarizing film 6 is formed on the interlayer insulating film 5. A metal pad 13 made of molybdenum, which is electrically connected to the source electrode S1, is formed through the interlayer insulating film 5. Further, the planarizing film 6 has a contact hole recessed in a substantially octagonal shape for electrical connection between the transmissive electrode 11 as a pixel electrode and the source electrode S1 above the source electrode S1 of the TFT element 4. 7 is provided. A contact pad 8 made of a refractory metal such as chromium is formed in the contact hole 7, and the contact pad 8 is electrically connected to the metal pad 13.

  A groove portion from which the planarizing film 6 is removed is provided at a location away from the TFT element 4. The groove portion corresponds to the transmission portion 9.

  On the flattening film 6, a material (Al) for the reflective film 10 is laminated on the portion excluding the transmission part 9. A portion where the reflection film 10 is laminated is a reflection portion 12. And ITO (or IZO (Indium-Zinc-Oxide)) is laminated | stacked on the reflection part 12 and the whole transmission part 9. As shown in FIG. This transparent material layer is electrically connected to the source electrode S 1 through the metal pad 13 at the contact hole 7, and this transparent material layer functions as the transparent electrode 11.

  The color filter substrate 30 is disposed to face the array substrate 50, and the liquid crystal material 20 is sandwiched between the array substrate 50 and the color filter substrate 30 (cell gap). The cell gap is formed at an interval of about 2 μm at the reflecting portion 12 and about 4 μm at the transmitting portion 9 because the thickness of the planarizing film 6 is about 2 μm. The contact hole 7 has a cell gap of about 4 μm with the addition of the thickness 2 μm of the planarizing film 6. In this embodiment, columnar spacers 33 are formed on the color filter substrate 30 so that the cell gap for each pixel is uniform.

  The color filter substrate 30 is disposed to face the array substrate 50, and the liquid crystal material 20 is sandwiched between the array substrate 50 and the color filter substrate 30 (cell gap). Columnar spacers 33 are formed on the color filter substrate 30 so that the cell gap is uniform in each region of the reflective portion 12 and the transmissive portion 9.

  Reference numeral 34 denotes a protrusion formed at a position facing the contact hole 7, and is formed by the photolithography method in the same process using the same resist as the columnar spacer 33 as a material. The cell gap dc1 between the bottom 7a of the contact hole 7 and the tip 34a of the protrusion 34 is formed at the same interval as the cell gap dr of the reflecting portion 12. Since the cell gaps dc1 and dr are formed at substantially the same interval as described above, the retardation value becomes the same value between the cell gaps dr and dc1, and the reflectance is reduced in the contact hole 7 portion. It can be prevented from occurring.

  In the color filter substrate 30, a common electrode 32 made of a color filter or ITO is formed on a glass substrate 31. The array substrate 50, the color filter substrate 30, and the liquid crystal material 20 constitute a liquid crystal panel 40.

  Although not shown below the array substrate 50, a backlight device having a well-known light source, light guide plate, diffusion sheet, and the like is disposed, and transmitted light transmitted from the backlight device passes through the transmission unit 9 and is externally transmitted. The light is reflected by the reflector 12. The array substrate 50 having the transmissive portion 9 and the reflective portion 12 in the same pixel, the liquid crystal material 20, the color filter substrate 30 and the backlight device are combined to constitute a transflective liquid crystal display device.

  FIG. 3 is a view showing another embodiment of the present invention, FIG. 3A is a plan view showing an outline of a portion of the contact hole 7, and FIG. 3B is a cross-sectional view taken along line BB of FIG.

  In this embodiment, the transmissive electrode 32a laminated on the surface of the protruding portion 34 is formed by patterning so as to cover a part of the protruding portion 34, the tip 32a from the root to a strip shape. On the other hand, the contact pad 8 is formed with a portion where the contact pad is not formed (contact pad punched portion 14) at a portion facing the belt-like transmissive electrode 32 a formed on the protrusion 34.

  As a result, even if the projection 34 comes into contact with the array substrate 50 side in the contact hole 7 due to misalignment of the alignment between the array substrate 50 and the color filter substrate 30, misalignment at the time of formation of the projection 34, etc. Since the contact pad removal portion 14 is formed in the portion facing the portion where the electrode 32a is formed and the contact pad 8 is cut away, the transmission electrode 32a and the contact pad 8 do not contact each other, and a short circuit occurs. There is nothing.

  In the present embodiment, the protrusion 34 has a height of about 2 μm, a width of about 6 to 8 μm, and the contact hole 7 has a diameter of about 10 μm.

  In the present embodiment, the top gate type TFT element is described as the array substrate 50. However, the present invention is not limited to this, and the present invention can also be applied to a liquid crystal display device adopting a bottom gate type TFT element. Further, the present invention is not limited to the transflective type, and can be applied to a reflective / transmissive liquid crystal display device. In addition, as an example of a method for making the cell gap different between the reflective portion 12 and the transmissive portion 9, an example in which the method of removing the planarizing film 6 in the transmissive portion 9 is described in the present embodiment, but the present invention is not limited thereto. Alternatively, a method of forming a cell gap adjusting layer with a resist on the reflective portion 12 on the color filter substrate 30 side may be employed.

  The protrusion 34 may be formed to have a height (h) substantially the same length as the depth (dc1) of the recess of the contact pad 8.

  It can be employed in a liquid crystal display device mounted on various electronic devices.

1 is a schematic plan view of a liquid crystal display device according to an embodiment of the present invention. It is a figure which shows schematic sectional structure of the liquid crystal display device in the position along the AA line of FIG. 1 concerning embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is a top view which shows schematic structure for demonstrating the conventional liquid crystal display device. It is a figure which shows schematic sectional structure of the transflective liquid crystal display device in the position along the XX line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Gate insulating film 3 Active layer 4 TFT element 5 Interlayer insulating film 6 Planarizing film 7 Contact hole 8 Contact pad 9 Metal pad 10 Reflective film 11 Transmission electrode 12 Reflecting part 13 Metal pad 14 Contact pad extraction part 20 Liquid crystal material 30 color filter substrate 31 glass substrate 32 transmissive electrode 33 columnar spacer 34 protrusion 40 liquid crystal panel 50 array substrate 100 array substrate 101 glass substrate 102 gate insulating film 103 active layer 104 TFT element 105 protective film 106 interlayer film 107 contact hole 109 transmissive portion DESCRIPTION OF SYMBOLS 110 Reflective film 111 Transparent electrode 112 Reflector 130 Color filter substrate 131 Glass substrate 132 Common electrode 133 Columnar spacer G Gate electrode Gl Gate wiring D Drain electrode S1 Source electrode Cs Auxiliary capacitance electrode

Claims (7)

A liquid crystal display device comprising a plurality of pixels, wherein two substrates each having electrodes for driving a liquid crystal on opposite sides are arranged to face each other with a liquid crystal layer interposed therebetween,
On one side of the substrate, a thin film transistor formed for each pixel, a pixel electrode, an interlayer film formed between the thin film transistor and the pixel electrode, and the thin film transistor formed in a recess penetrating the interlayer film, A contact portion for connecting the pixel electrode,
A liquid crystal display device comprising: a counter electrode on the other side of the substrate; and a protrusion formed at a position facing the contact portion of the counter electrode.   The liquid crystal display according to claim 1, wherein the protrusion is formed at a height at which a cell gap around the contact portion and a cell gap between the contact portion and the protrusion are substantially the same. apparatus.   The liquid crystal display device according to claim 1, wherein the protrusion has a height substantially the same length as the depth of the recess of the contact portion.   2. The pixel electrode according to claim 1, wherein a reflection region that reflects light incident from the substrate on the other side is formed to overlap the pixel electrode, and the contact portion is formed in the reflection region. Liquid crystal display device.   A reflection region that reflects light incident from the other substrate superimposed on the pixel electrode; and a transmission region that transmits light incident from the other substrate, and the contact portion is disposed in the reflection region. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed.   The liquid crystal display device according to claim 1, wherein a portion of the contact portion that interferes with a counter electrode formed on the protrusion is removed. The liquid crystal display device according to claim 1, further comprising a columnar spacer that keeps a cell gap between the two substrates constant, wherein the columnar spacer is formed in the same process as the protrusion.