JP3662013B2 - Active matrix liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display device having a transmissive display area and a reflective display area.

  As a liquid crystal display device, an active matrix liquid crystal display device in which a thin film transistor (TFT) or an MIM element made of amorphous Si is formed on a substrate together with a plurality of gate wirings and data wirings intersecting each other is known.

  This active matrix substrate includes a transmissive liquid crystal display device that uses a backlight as a light source and a reflective liquid crystal display device that reflects external light and uses it for display.

  In these active matrix liquid crystal display devices, an organic material such as a photosensitive transparent acrylic resin is used as an interlayer insulating film, and transmission of a high aperture ratio structure in which pixel electrodes are superimposed on the gate wiring and data wiring through the interlayer insulating film. Type liquid crystal display devices and reflection type liquid crystal display devices have been developed.

  8A is a plan view of a reflective liquid crystal display device having a high aperture ratio structure using an organic insulating film as an interlayer insulating film, and FIG. 8B is a cross-sectional view taken along line FF in FIG. FIG.

  The active matrix liquid crystal display device shown in FIG. 8 includes a gate line 1, a data line 2, a drive element 3, a drain electrode 4, an auxiliary capacitance electrode 5, a gate insulating film 6, an insulating substrate 7, a contact hole 8, and an interlayer insulating film. 9, a reflective picture element electrode 10, and an auxiliary capacitance wiring 12 are provided.

  A transmissive liquid crystal display device can be obtained by using the reflective pixel electrode 10 of the active matrix liquid crystal display device shown in FIG. 8 as a transparent electrode.

  As a material of the interlayer insulating film 9 used for this high aperture ratio structure, in order to reduce the capacitance generated by superimposing the pixel electrode on the gate wiring and the data wiring through the interlayer insulating film 9, several μm is used. An organic insulating film is used because it is required to be easily formed with a thickness and to have a dielectric constant smaller than that of silicon nitride or the like.

  In order to form this high aperture ratio structure, the drain electrode 4 disposed in the lower layer of the interlayer insulating film 9 and the pixel electrode disposed in the upper layer of the interlayer insulating film 9 are brought into electrical contact. In addition, it is necessary to form a contact hole in the interlayer insulating film 9, but by using a photosensitive acrylic resin as the interlayer insulating film 9, a liquid resin material is applied to the substrate by a spin coating method, and then in a photolithography process. Since patterning is performed by exposure and development with an alkaline solution to form a contact hole, film formation and patterning can be performed simultaneously.

  A transmissive liquid crystal display device that uses light from a backlight for display uses a backlight and consumes a lot of power. When a battery is used, the continuous use time is short.

  Reflective liquid crystal display devices have the advantages of low power consumption and long continuous use time because they do not use a backlight, but there are problems in that the reflection intensity is not sufficient and it is difficult to use in dark places. It was.

The present invention includes an active matrix substrate having a pixel electrode electrically connected to a driving element provided on an insulating substrate, a counter substrate on which a counter electrode is formed, and the counter substrate and the active matrix substrate a liquid crystal layer interposed between the, in the active matrix liquid crystal display device having a backlight, the picture element electrodes have a the transmissive pixel electrode and the reflective pixel electrode, the one picture element A reflective display region and a transmissive display region are provided therein, and the reflective pixel electrode is formed on an interlayer insulating film having an inclined portion or an uneven portion, and a boundary region between the reflective display region and the transmissive display region The reflective pixel electrode and the transmissive pixel electrode are electrically connected .

  According to the present invention, it is possible to form an active matrix liquid crystal display device that can be used as a reflection type liquid crystal display device in a bright place and can be used as a transmission type liquid crystal display device by turning on a backlight in a dark place. Become.

  According to the present invention, since the reflective pixel electrode and the transmissive pixel electrode are electrically connected, it is not necessary to provide a wiring for inputting a drive signal separately, and the configuration of the active matrix substrate is simplified. Can be

According to the present invention, by forming the pixel electrode reflecting on the drive element, it is possible to prevent light from the outside is incident on the driving element.

  According to the present invention, the transparent pixel electrode does not contribute to the brightness of the panel when the backlight is turned off, but the reflective pixel electrode that reflects light from the outside is used to turn on and off the backlight. Regardless, it contributes to the brightness of the panel. By increasing the area, the brightness of the display can be stabilized even when the backlight is turned off or when the brightness is low.

  According to the present invention, the viewing angle can be widened because the reflecting picture element electrode spreads in the direction in which light from the outside is reflected.

  According to the present invention, an active matrix liquid crystal display device capable of switching between a reflective type and a transmissive type can be formed.

  As a result, the user can switch between transmission and reflection according to usage conditions, thereby realizing a liquid crystal display device that consumes less power and can be used for a long time while providing sufficient luminance in any usage situation.

  Further, it is possible to form an active matrix type liquid crystal display device that can be used as a reflection type liquid crystal display device in a bright place and can be used as a transmission type liquid crystal display device by turning on a backlight in a dark place.

  In addition, since the reflective pixel electrode and the transmissive pixel electrode are electrically connected, it is not necessary to provide a wiring for inputting a drive signal separately, and the configuration of the active matrix substrate can be simplified.

Further, if the reflective pixel electrode is formed on the driving element, it is possible to prevent light from the outside from entering the driving element.

  In addition, the transmission pixel electrode does not contribute to the brightness of the panel when the backlight is turned off, but the reflective pixel electrode that reflects light from the outside does not affect the panel regardless of whether the backlight is turned on or off. Since it contributes to luminance, the display luminance can be stabilized even when the backlight is turned off or when the luminance is low, by increasing the area.

  In addition, since the reflection picture element electrode spreads in the direction in which light from the outside is reflected, the viewing angle can be widened.

  FIG. 1A is a plan view of an active matrix substrate according to Embodiment 1 of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA of FIG.

  The active matrix substrate includes a gate wiring 1, a data wiring 2, a driving element 3, a drain electrode 4, an auxiliary capacitance electrode 5, a gate insulating film 6, an insulating substrate 7, a contact hole 8, an interlayer insulating film 9, and a reflective pixel electrode. 10 and a transmission picture element electrode 11 are provided.

  The auxiliary capacitance electrode 5 is electrically connected to the drain electrode 4 and overlaps with the gate wiring 1 through the gate insulating film 6 to form an auxiliary capacitance.

  The contact hole 8 is provided in the interlayer insulating film 9 to connect the transmissive pixel electrode 11 and the auxiliary capacitance electrode 5.

  This active matrix substrate includes a reflection pixel electrode 10 and a transmission pixel electrode 11 in one picture element, and reflects light from the outside in one picture element as shown in FIG. A reflective picture element electrode 10 and a transparent picture element electrode 11 that transmit the light of the backlight are formed.

  FIG. 2 is a cross-sectional view showing a liquid crystal display device using the active matrix substrate shown in FIG. 1, and includes data wiring 2, drain electrode 4, gate insulating film 6, insulating substrate 7, interlayer insulating film 9, and reflection picture. It has an element electrode 10, a transmission pixel electrode 11, a color filter layer 13, a counter electrode 14, a liquid crystal layer 15, an alignment film 16, a polarizing plate 17, and a backlight 18.

  The transmissive pixel electrode 11 portion that transmits the light of the backlight 18 does not contribute to the brightness of the panel when the backlight is turned off, but the reflective pixel electrode 10 portion that reflects light from the outside does not contribute to the backlight. In order to contribute to the brightness of the panel regardless of whether the light is turned on or off, it is desirable to make the area of the reflective pixel electrode 10 larger than the transparent pixel electrode 11.

  In this embodiment, in order to input the same signal to the reflective pixel electrode 10 and the transmissive pixel electrode 11, the reflective pixel electrode 10 is formed on the transmissive pixel electrode 11 and electrically connected thereto. However, the reflective picture element electrode 10 and the transmissive picture element electrode 11 may not be electrically connected, and different signals may be input to the respective display parts.

  In the liquid crystal display device of FIG. 2, the light from the backlight 18 that is incident on the region where the reflective pixel electrode 10 is formed cannot be used as display light, and therefore, as in the cross-sectional view of the liquid crystal display device shown in FIG. A microlens 19 and a microlens protective layer 20 are formed between the backlight 18 and the liquid crystal display panel, and backlight light is applied to a region of the transmissive pixel electrode 11 where the reflective pixel electrode 10 is not formed by the microlens 19. The amount of light transmitted through the transmission pixel electrode 11 can be increased to increase the display brightness.

  FIG. 4A shows a plan view of an active matrix substrate of another example of this embodiment, and FIG. 4B shows a cross-sectional view taken along the line BB of FIG. 4A. On the other hand, the areas of the reflection pixel electrode 10 and the transmission pixel electrode 11 are reversed, and the area ratio of the reflection pixel electrode 10 and the transmission pixel electrode 11 may be changed as appropriate.

  When the active matrix substrate of FIG. 1 is compared with the active matrix substrate of FIG. 4, the active matrix substrate of FIG. 1 has the reflective pixel electrode 10 formed on the driving element 3, and light from the outside Can be prevented from entering the driving element 3, and the condensing microlens 19 can be easily formed because the transmitting picture element electrode 11 is disposed at the center of the picture element.

  In the present invention, it is desirable to increase the aperture ratio as much as possible in order to form a light reflecting part and a light transmitting part in one picture element. In this embodiment, the picture element electrode, the gate wiring 1 and the source wiring are used. Although a high aperture ratio groove structure in which an interlayer insulating film 9 made of an organic insulating film is interposed between the two is employed, other structures may be used.

  FIG. 5A shows a plan view of the active matrix substrate of Embodiment 2, and FIG. 5B shows a cross-sectional view taken along the line CC in FIG. 5A.

  In the active matrix liquid crystal display device according to the second embodiment, the reflective pixel electrode 10 is formed on the interlayer insulating film 9 formed with the inclined portion or the uneven portion, and light from the outside is reflected by the reflective pixel electrode 10. Since the spread appears in the reflected direction, the viewing angle can be widened.

  Further, when the interlayer insulating film 9 is thickest on the gate wiring 1 and the data wiring 2 and an inclined portion or an uneven portion is formed so as not to be formed on the drain electrode 4, electrical contact between the drain electrode 4 and the pixel electrode 10 is achieved. It is not necessary to form a contact hole for removing the liquid crystal, and it is possible to prevent alignment disorder of the liquid crystal molecules generated due to the steep step at the contact hole portion, so that the aperture ratio can be increased.

  The drain electrode 4 also serves as a transmissive pixel electrode, and is a transparent electrode made of ITO or the like.

  In addition, the inclination angle of the inclined portion of the interlayer insulating film 9 or the uneven pitch of the uneven portion needs to be suppressed to an angle at which the rubbing treatment can be sufficiently performed after forming the alignment film. Use optimized conditions.

  Also in the present embodiment, a microlens is provided in the drain electrode 4 portion which also serves as a transmissive pixel electrode, and the luminance when the backlight is turned on can be increased.

  FIG. 6A shows a plan view of the active matrix substrate of Embodiment 3, and FIG. 6B shows a cross-sectional view taken along the line DD in FIG. 6A.

  In this embodiment, the reflective pixel electrode 10 is formed in the same layer as the gate wiring 1 in the same process.

  In this way, there is no need to provide a separate process for forming the reflective pixel electrode 10, and the number of processes and manufacturing costs are not increased.

  In the case of this embodiment, the reflective pixel electrode 10 is not connected to the drain electrode 4 of the driving element 3 and is used only for reflecting light from the outside, and is an electrode for driving the liquid crystal. The transmission picture element electrode 11 performs the role of.

  That is, the transmittance of the light reflected by the reflective pixel electrode 10 is controlled by controlling the liquid crystal layer by the voltage of the transparent pixel electrode 11.

  At this time, if no signal is input to the reflective pixel electrode 10, stray capacitance is generated between the drain electrode 4 and the transmissive pixel electrode 11. It is desirable to input a signal that does not adversely affect the gate electrode. By connecting to the adjacent gate wiring 1, stray capacitance can be prevented and an auxiliary capacitance can be formed between the drain electrode 4.

  Also in this embodiment, it is possible to increase the luminance when the backlight is turned on by condensing the transmission pixel electrode by the microlens.

  Also in the present invention, it is desirable to increase the aperture ratio as much as possible in order to form a light reflecting part and a light transmitting part in one picture element.

  Therefore, as a configuration of the present embodiment, a high aperture ratio structure using an organic insulating film as an interlayer insulating film is adopted, but other structures may be used.

  FIG. 7A shows a plan view of the active matrix substrate of Embodiment 4, and FIG. 7B shows a cross-sectional view of the EE cross section of FIG. 7A.

  In this embodiment, the reflective pixel electrode 10 is formed in the same layer as the data wiring 2.

  In this way, the reflective picture element electrode 10 can be formed when the data wiring 2 is formed, and the number of processes and manufacturing cost are not increased.

  Even in the case of the present embodiment, since the high aperture ratio structure through the interlayer insulating film 9 is adopted, the reflective pixel electrode 10 is used only for reflecting light from the outside as in the third embodiment. Thus, only the transmission pixel electrode 11 plays a role as an electrode for driving the liquid crystal molecules.

  Here, the present embodiment is different from the third embodiment in that the drain electrode 4 and the reflective pixel electrode are formed in an electrically connected form, and the drain electrode is formed without forming the interlayer insulating film 9. When 4 is used as a transmission pixel electrode, the reflection pixel electrode 10 also contributes to driving of liquid crystal molecules.

  Also in the present embodiment, the luminance when the backlight is turned on can be increased by condensing the transmission pixel electrode 11 by the microlens.

  Also in this embodiment, it is desirable to increase the aperture ratio as much as possible in order to form a portion that reflects light and a portion that transmits light in one picture element.

  Therefore, as the configuration of this embodiment, a high aperture ratio structure using an organic insulating film as an interlayer insulating film is adopted, but other configurations may be used.

It is the top view and sectional drawing which show the active matrix substrate of Embodiment 1 of this invention. It is sectional drawing which shows the active matrix substrate of Embodiment 1 of this invention. It is sectional drawing which shows the active matrix board | substrate provided with the micro lens of this invention. It is the top view and sectional drawing which show the other example of the active matrix substrate of Embodiment 1 of this invention. It is the top view and sectional drawing which show the active matrix substrate of Embodiment 2 of this invention. It is the top view and sectional drawing which show the active matrix substrate of Embodiment 3 of this invention. It is the top view and sectional drawing which show the active matrix substrate of Embodiment 4 of this invention. It is sectional drawing which shows the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gate wiring 2 Data wiring 3 Drive element 4 Drain electrode 5 Auxiliary capacity electrode 6 Gate insulating film 7 Insulating substrate 8 Contact hole 9 Interlayer insulating film 10 Reflection pixel electrode 11 Transmission pixel electrode 12 Auxiliary capacity wiring 13 Color filter Layer 14 Counter electrode 15 Liquid crystal layer 16 Alignment film 17 Polarizing plate 18 Backlight 19 Microlens 20 Microlens protective layer

Claims (1)

Interposed between the active matrix substrate having a pixel electrode electrically connected to a driving element provided on an insulating substrate, a counter substrate on which a counter electrode is formed, and the counter substrate and the active matrix substrate In an active matrix liquid crystal display device having a liquid crystal layer and a backlight,
The pixel electrode may possess a transmissive pixel electrode and the reflective pixel electrode, together with and a reflective display region and the transmissive display region in one picture element, the reflective pixel electrode inclined portion Alternatively, the reflective pixel electrode and the transmissive pixel electrode are electrically connected to each other at a boundary region between the reflective display region and the transmissive display region. An active matrix type liquid crystal display device.

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