JP2002258302A - Active matrix type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a liquid crystal display device to have small power consumption in a light place and to give a display state with sufficient display luminance in a dark place. SOLUTION: This active substrate has a pixel electrode 10 for reflection and a pixel electrode 11 for transmission in one pixel, and a pixel electrode part for reflection which reflects external light and a pixel electrode part for transmission which transmits the light of a back light are formed in one pixel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having a transmissive display area and a reflective display area.

[0002]

2. Description of the Related Art As a liquid crystal display device, a thin film transistor (TFT) made of amorphous Si together with a plurality of gate lines and data lines crossing each other is used.
Alternatively, an active matrix type liquid crystal display device having an MIM element formed on a substrate is known.

The active matrix substrate includes a transmission type liquid crystal display device using a backlight as a light source,
There is a reflection type liquid crystal display device that reflects external light and uses it for display.

In these active matrix type liquid crystal display devices, an organic material such as a photosensitive transparent acrylic resin is used as an interlayer insulating film, and a high aperture ratio is provided in which a pixel electrode is overlapped on a gate wiring and a data wiring via an interlayer insulating film. A transmission type liquid crystal display device and a reflection type liquid crystal display device having a structure have been developed.

FIG. 8A is a plan view of a reflection type 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 plan view of FIG. It is sectional drawing which shows -F cross section.

The active matrix type liquid crystal display device shown in FIG. 8 has a gate wiring 1, a data wiring 2, a driving element 3,
It includes 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, a reflective pixel electrode 10, and an auxiliary capacitance wiring 12.

A transmission type liquid crystal display device can be obtained by using a transparent electrode as the reflection picture element electrode 10 of the active matrix type liquid crystal display device shown in FIG.

The interlayer insulating film 9 used for the high aperture ratio structure
Is easily formed with a thickness of several μm in order to reduce the capacitance generated by superimposing the picture element electrode on the gate wiring and the data wiring via the interlayer insulating film 9; It is required that the dielectric constant is smaller than that of silicon nitride or the like, and an organic insulating film is used.

In order to form the high aperture ratio structure, the electrical contact between the drain electrode 4 provided below the interlayer insulating film 9 and the picture element electrode provided above the interlayer insulating film 9 is required. It is necessary to form a contact hole in the interlayer insulating film 9 in order to remove the
By using as a substrate, a liquid resin material is applied to a substrate by a spin coating method, then exposed in a photolithography process, and patterned by performing development with an alkaline solution to form a contact hole. And patterning can be performed simultaneously.

[0010]

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

The reflection type liquid crystal display has the advantages of low power consumption and long continuous use time because it does not use a backlight. However, the reflection intensity is not sufficient and it is difficult to use it in a dark place. There was a point.

[0012]

SUMMARY OF THE INVENTION The present invention provides an insulating substrate, a plurality of gate wirings provided on the insulating substrate,
An active matrix substrate having a plurality of data lines intersecting the gate lines, a driving element provided at an intersection of the gate lines and the data lines, and a pixel electrode electrically connected to the driving elements. And an opposing substrate on which an opposing electrode is formed, a liquid crystal layer interposed between the active matrix substrate and the opposing substrate, and an active matrix liquid crystal display device including a backlight, wherein the picture element electrode is It has a reflection picture element electrode and a transmission picture element electrode, and the reflection picture element electrode is formed in contact with the liquid crystal layer side of the transmission picture element electrode.

According to the present invention, an active matrix type liquid crystal display device which can be used as a transmission type liquid crystal display device which can be used as a reflection type liquid crystal display device in a bright place and turned on a backlight in a dark place to be used as a transmission type liquid crystal display device. Becomes possible.

Further, since the reflective picture element electrode and the transmissive picture element electrode are electrically connected, it is not necessary to separately provide a wiring for inputting a drive signal. Can be simplified.

Further, by forming the reflective picture element electrode above the driving element, it is possible to prevent external light from being incident on the driving element.

Further, if the area of a portion where external light is reflected by the reflective picture element electrode is made larger than an area of a part where light of a backlight is transmitted by the transmissive picture element electrode, a transmissive picture element is provided. The electrodes do not contribute to the brightness of the panel when the backlight is turned off, but the reflective picture element for reflecting external light contributes to the brightness of the panel regardless of whether the backlight is on or off. By increasing the area, the display brightness can be stabilized even when the backlight light is turned off or when the brightness is low.

If a microlens is provided between the active matrix substrate and the backlight, light from the backlight, which is shielded by the reflective picture element electrode or the gate wiring, can be collected by the transmissive picture element electrode. Therefore, the brightness of the display device can be increased without increasing the brightness of the backlight itself.

Further, if an interlayer insulating film having an inclined portion or an uneven portion is formed on the drain electrode, and the reflective picture element electrode is formed on the interlayer insulating film, the reflective picture element electrode can be used from outside. Since the light spreads in the direction in which the light is reflected, the viewing angle can be widened.

Further, if the reflection picture element electrode is formed in the same layer as the gate wiring or the data wiring, there is no need to provide a separate step of forming the reflection picture element electrode, which increases the number of steps and the manufacturing cost. I won't let you.

Further, if the reflection picture element electrode formed in the same layer as the gate wiring is electrically connected to the adjacent picture element gate wiring, stray capacitance of the reflection picture element electrode can be prevented. Thus, an auxiliary capacitor can be formed between the drain capacitor and the drain electrode.

Further, by inputting the same signal as the signal applied to the counter electrode to the reflection picture element electrode formed on the same layer as the gate wiring, it is possible to prevent the reflection picture element electrode from becoming a floating capacitance. Can be.

Further, if the auxiliary capacitance is formed by superimposing the reflective picture element electrode and the drain or transmissive picture element electrode formed in the same layer as the gate wiring, the voltage applied to the picture element electrode can be reduced. The auxiliary capacitance can be formed by using the reflective picture element electrode.

[0023]

(Embodiment 1) 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 line AA of FIG. 1A. 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, A pixel electrode 10 and a transmission pixel electrode 11 are provided.

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

The contact hole 8 is formed in the picture element electrode 1 for transmission.
1 is provided in the interlayer insulating film 9 to connect the storage capacitor electrode 1 to the storage capacitor electrode 5.

This active matrix substrate is provided with a reflection picture element electrode 10 and a transmission picture element electrode 11 in one picture element, and as shown in FIG. A reflective picture element electrode 10 that reflects light and a transmissive picture element electrode 11 that transmits light from the backlight are formed.

FIG. 2 is a sectional view showing a liquid crystal display device using the active matrix substrate shown in FIG. 1, and includes a data line 2, a drain electrode 4, a gate insulating film 6, an insulating substrate 7, an interlayer insulating film 9, It has a reflective picture element electrode 10, a transmissive picture element 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 portion of the transmitting picture element electrode 11 which transmits the light of the backlight 18 does not contribute to the brightness of the panel when the backlight is turned off, but the reflecting picture element electrode 10 which reflects light from the outside. Since the portion contributes to the brightness of the panel regardless of whether the backlight is turned on or off, it is desirable to make the area of the reflective picture element electrode 10 larger than that of the transmissive picture element electrode 11.

In this embodiment, in order to input the same signal to the reflection picture element electrode 10 and the transmission picture element electrode 11, the reflection picture element electrode 10 is formed on the transmission picture element electrode 11 and electrically connected. Although connected, 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 each to perform separate display.

In the liquid crystal display device shown in FIG.
Since the light from the backlight 18 incident on the region where 0 is formed cannot be used as display light, a micro lens is disposed between the backlight 18 and the liquid crystal display panel as shown in the sectional view of the liquid crystal display device shown in FIG. 19 and a microlens protective layer 20 are formed, and the backlight is condensed by the microlens 19 in a region of the transmission pixel electrode 11 where the reflection pixel electrode 10 is not formed. The amount of transmitted light can be increased to increase the display brightness.

FIG. 4A is a plan view of another example of the active matrix substrate of the present embodiment, and FIG.
FIG. 2A is a cross-sectional view taken along the line BB of FIG. 1, and the areas of the reflective picture element electrode 10 and the transmissive picture element electrode 11 are reversed with respect to FIG. Picture element electrode 1
The area ratio of 1 may be appropriately changed.

When the active matrix substrate of FIG. 1 is compared with the active matrix substrate of FIG. 4, the active matrix substrate of FIG. Light from the driving element 3
And since the transmission picture element electrode 11 is arranged at the center of the picture element, it is easy to form the condensing microlens 19.

In the present invention, it is desirable to increase the aperture ratio as much as possible in order to form a light-reflecting portion and a light-transmitting portion in one picture element. Although a high aperture ratio groove structure in which an interlayer insulating film 9 made of an organic insulating film is interposed between the source wiring 3 and the source wiring 3 is adopted, other structures may be used.

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

The active matrix type liquid crystal display device according to the second embodiment has an interlayer insulating film 9 having an inclined portion or an uneven portion.
The reflective picture element electrode 10 is formed on the upper part, and the reflection picture element electrode 10 spreads in the direction in which light from the outside is reflected, so that the viewing angle can be widened.

The interlayer insulating film 9 is the thickest on the gate wiring 1 and the data wiring 2, and if an inclined portion or an uneven portion is formed so as not to be formed on the drain electrode 4, the drain electrode 4 and the pixel electrode 10 There is no need to form a contact hole for making electrical contact, and it is possible to prevent alignment disorder of liquid crystal molecules generated due to a steep step in the contact hole portion, so that a large aperture ratio can be obtained.

The drain electrode 4 also serves as a transmission picture element electrode, and is a transparent electrode made of ITO or the like.

The angle of inclination of the inclined portion of the interlayer insulating film 9 or the pitch of the concave and convex portions of the concave and convex portions must be suppressed to such an angle that a rubbing process can be sufficiently performed after forming an alignment film. Conditions that are optimized for

Also in this embodiment, a microlens is provided in the drain electrode 4 which also serves as a transmission picture element electrode, so that the luminance when the backlight is turned on can be increased.

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

In this embodiment, the reflective picture element electrode 10
Are formed in the same layer as the gate wiring 1 in the same step.

In this way, there is no need to provide a separate step of forming the reflective picture element electrode 10, and the number of steps and the manufacturing cost do not increase.

In the case of this embodiment, the reflective picture element electrode 10
Is not connected to the drain electrode 4 of the driving element 3,
It is used only for reflecting light from the outside, and serves as an electrode for driving the liquid crystal.
1 does.

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

At this time, if no signal is input to the reflection picture element electrode 10, a floating capacitance is generated between the drain picture element electrode 10 and the transmission picture element electrode 11. It is desirable to input a signal which does not adversely affect the display. By connecting to the adjacent gate wiring 1, stray capacitance can be prevented, and an auxiliary capacitance can be formed between the gate electrode 1 and the drain electrode 4. .

Also in this embodiment, the brightness at the time of backlight lighting can be increased by condensing the light on the transmitting picture element electrode by the microlens.

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

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

Fourth Embodiment FIG. 7A shows a fourth embodiment.
FIG. 7 is a plan view of the active matrix substrate of FIG.
FIG. 7B is a cross-sectional view taken along the line EE in FIG.

In this embodiment, the reflective picture element 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, without increasing the number of steps and the manufacturing cost.

Also in the present embodiment, since the high aperture ratio structure via the interlayer insulating film 9 is adopted, the reflective picture element electrode 10 only reflects external light as in the third embodiment. Only the transmission picture element electrode 11 plays a role as an electrode for driving liquid crystal molecules.

Here, the present embodiment is different from the third embodiment in that the drain electrode 4 and the reflective picture element electrode are formed in an electrically connected form, and the interlayer insulating film 9 is not formed. When the drain electrode 4 is used as a transmission picture element electrode, the reflection picture element electrode 10 also contributes to driving of liquid crystal molecules.

Also in the present embodiment, the brightness when the backlight is turned on can be increased by condensing the light on the transmission picture element 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 light reflecting portion and a light transmitting portion in one picture element.

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

[0058]

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

Thus, the user can switch between transmission and reflection in accordance with the use condition, thereby realizing a liquid crystal display device which consumes a small amount of power and can be used for a long time while providing sufficient luminance in any use condition. it can.

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

Further, since the reflection picture element electrode and the transmission picture element electrode are electrically connected, it is not necessary to separately provide a wiring for inputting a drive signal, and the configuration of the active matrix substrate is simplified. it can.

[Brief description of the drawings]

FIG. 1 is a plan view and a cross-sectional view illustrating an active matrix substrate according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an active matrix substrate according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing an active matrix substrate provided with a microlens of the present invention.

FIG. 4 is a plan view and a sectional view showing another example of the active matrix substrate according to the first embodiment of the present invention.

FIG. 5 is a plan view and a cross-sectional view illustrating an active matrix substrate according to a second embodiment of the present invention.

FIG. 6 is a plan view and a cross-sectional view illustrating an active matrix substrate according to a third embodiment of the present invention.

FIG. 7 is a plan view and a cross-sectional view illustrating an active matrix substrate according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view showing a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate wiring 2 Data wiring 3 Driving element 4 Drain electrode 5 Auxiliary capacitance electrode 6 Gate insulating film 7 Insulating substrate 8 Contact hole 9 Interlayer insulating film 10 Reflection picture element electrode 11 Transmission picture element 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 Micro lens 20 Micro lens protective layer

Claims (1)

[Claims] An insulating substrate; a plurality of gate wirings provided on the insulating substrate; a plurality of data wirings intersecting the gate wirings; and an intersection provided between the gate wirings and the data wirings. An active matrix substrate having a driving element, a pixel electrode electrically connected to the driving element, a counter substrate on which a counter electrode is formed, and an interposition between the active matrix substrate and the counter substrate. In the active matrix type liquid crystal display device having a divided liquid crystal layer and a backlight, the picture element electrode has a reflection picture element electrode and a transmission picture element electrode, and the liquid crystal layer of the transmission picture element electrode An active matrix type liquid crystal display device, wherein the reflective picture element electrode is formed in contact with the side.