JPH0371693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device in which a driving circuit is formed on a substrate constituting a liquid crystal panel.

[Conventional technology]

In recent years, display devices using liquid crystal dot matrix have attracted attention as moving image display devices that operate with lower power than cathode ray tubes. Since this display device operates with low power, it has potential as a display device for portable televisions.

FIG. 1 is an exploded view of a conventionally widely used dynamic drive type liquid crystal display. 10
1 is a glass substrate, 102 is a transparent electrode, and 103 is a spacer, which is located between the two glass substrates and plays the role of keeping the distance between the two glass substrates constant and the role of sealing the liquid crystal. 105 is a glass substrate with a transparent electrode 104 attached thereto. The liquid crystal is sealed between glass substrates 101 and 105, and the voltage is applied between electrodes 102 and 1.
Applied by 05.

FIG. 2 is an equivalent circuit of FIG. 1, and 201 represents a liquid crystal. X ₁ , X ₂ ... are the electrodes 102
y ₁ , y ₂ . . . represent electrodes 104. electrode
x ₁ , x ₂ . . . and y ₁ , y ₂ .

Although this method is easier to drive than static drive, it has the following drawbacks.

If you increase the number of picture elements to improve resolution, the time it takes to drive each picture element becomes shorter, and a liquid crystal with a slow response cannot keep up with this.

Crosstalk occurs and the image quality is poor. For example, when a voltage is applied to x ₂ and y ₁ , a voltage is applied to liquid crystal a. However, x ₂ →b ₁ →b ₂ →c ₃ →c ₁ →
Due to the loop of d ₁ →d ₂ →y ₁ , voltage is also applied to untargeted picture elements b, c, and d, resulting in a halftone around the targeted picture element a.

As a way to compensate for these shortcomings, the substrate constituting the display body is silicon single crystal or SOS.
Possible methods include using a (Si1icon on Safire) substrate or forming a compound semiconductor on the substrate and attaching a switching element to each picture element.

[Problem that the invention seeks to solve]

However, when using a silicon single crystal substrate or an SOS substrate as described above, the substrate becomes extremely expensive, making it difficult to obtain a large display body. Furthermore, since the substrate has poor transparency, it is difficult to obtain a transmissive display panel. Furthermore, when a compound semiconductor is used, it is difficult to form a compound with a uniform composition ratio, which causes problems such as uneven display and changes over time when forming a large screen. The present invention creates a switching transistor by forming a thin film semiconductor made of amorphous silicon on an insulating substrate, and supplies a video signal to a liquid crystal drive electrode through this switching transistor, thereby achieving a high duty and stable display. The purpose of this is to obtain an accurate display.

[Means for solving problems]

The present invention relates to a liquid crystal display device in which a liquid crystal is enclosed within a pair of substrates and a plurality of liquid crystal drive electrodes are arranged in a matrix on one of the substrates. a source region made of amorphous silicon, a semiconductor region made of amorphous silicon,
It has a drain region connected to a drain wiring, a gate electrode connected to the semiconductor region via an insulating film, and the source region and the semiconductor region and the drain region and the semiconductor region overlap each other. The source region, the semiconductor region, the drain region, and the gate electrode form a thin film transistor.

〔Example〕

FIG. 3 shows the principle of the present invention using an equivalent circuit. Third
In the figure, 301a, 301b... are switching transistors attached to each picture element, respectively.
2a, 302b... Capacitor, 303a, 30
3b... is a liquid crystal display. Now, if we consider the case where a scanning signal is input to ^y1 and a drive input is input to _x2 , only the switching transistor 301a is turned on and the drive input is connected to the capacitor 302a and the liquid crystal display 303.
applied to a. At this time, the transistors 301b, 301c, . . . attached to other picture elements are in an OFF state, so crosstalk does not necessarily occur. Furthermore, the picture element to which the signal is applied has a liquid crystal 303.
Since a capacitor 302a is inserted in parallel with a, even if the scanning point moves, the display can be maintained by the charge stored in the capacitor until the next scan is performed.

Figures 4a, b, and c show the structure of the present invention. Figure a shows the cross-sectional structure of one picture element, and figure b is a partially enlarged view. 401 is a transparent glass substrate with a common electrode 402; 403
is a drain region of a thin film transistor (hereinafter referred to as TFT), 404 is a source, 412 is a semiconductor region, 405 is a gate insulator, 406 is a gate electrode, 407 is a drain region, 408 is Sio, Sio ₂ ,
It is a protective film made of an insulator such as Si ₃ H ₄ . Also, 4
Reference numeral 09 denotes a liquid crystal drive electrode, which is made of a transparent electrode. A capacitor 410 is made of a dielectric film formed by sputtering or vapor deposition, a thick film formed by printing, or an organic resin film. This capacitor performs its original role as a capacitor, preventing the flow of other liquid crystals, preventing electrical effects on adjacent picture elements, and separating picture elements. Further, 411 is an insulating substrate.

FIG. 4C shows the parallel structure of FIG. 4A, but the common electrode 402 and the glass substrate 401 are omitted.

Amorphous silicon is used for the semiconductor region 412 constituting the TFT. Conventionally, compound materials such as Cds and CdSe have been widely used as materials for this semiconductor region. However, it is difficult to create fine patterns, which causes problems such as deterioration of characteristics.

However, in the present invention, by using an amorphous silicon film, the photoetching technology established in the IC manufacturing process can be used as is, and it has become possible to easily form micro-order fine patterns.

Furthermore, good results have been obtained in terms of long-term reliability.

In this example, the transistor is spattered, CVD,
Since it is made using technology such as that, it is possible to make large display bodies. Furthermore, since a transparent substrate is used for the substrate itself, it has the advantage that display bodies can be stacked to form a multilayer panel, and colorization can be easily done.

〔Effect of the invention〕

By implementing the invention as described above, the following effects can be obtained.

That is, (a) when a thin film transistor is formed using non-monocrystalline silicon, the crystallinity is poorer than that of a transistor formed from single-crystalline silicon, so there is a large amount of leakage current when the transistor is turned off. In addition, especially when thin film transistors are formed using amorphous silicon, as can be inferred from the fact that amorphous silicon is used in solar cells, photo leakage current occurs when exposed to external light, so when the thin film transistor is turned off, There was a drawback that the charge stored in the liquid crystal layer leaked, but in this application, a capacitor for charge retention is provided, so even if there is a leakage current when it is OFF, sufficient charge can be stored. .

(b) Since amorphous silicon has high resistance, when using amorphous silicon for the channel of a thin film transistor, it is better to form the channel region as thin as possible.

Therefore, when the channel portion is formed of amorphous silicon as in the present application, the amorphous silicon of the channel portion can be formed as thin as possible by forming the channel portion, the source electrode, and the drain electrode as separate members.

(c) Since amorphous silicon can be formed at low temperatures, inexpensive glass substrates can be used, and it is very effective in increasing the screen size of liquid crystal display devices.

[Brief explanation of drawings]

FIG. 1 is an exploded view of a conventional liquid crystal display, and FIG. 2 is an equivalent circuit diagram of the display shown in FIG. FIG. 3 is an equivalent circuit of the display device of the present invention, and FIG. 4 is a, b, and c of the structure of the display of the present invention, a is a cross-sectional view, and b is an enlarged view of a. c shows a plan view. 101...Glass substrate, 102...Transparent electrode,
103...Spacer, 104...Transparent electrode, 10
5...Glass substrate, 201...Liquid crystal, 301a,
b...Switching transistor, 302a, b
... Capacitor, 303a, b ... Liquid crystal display,
401... Glass substrate, 402... Transparent electrode, 403... Drain region, 404... Source region, 405... Gate insulator, 406... Gate electrode, 407... Drain electrode, 408... Protective film , 409... Drive electrode, 410... Capacitor, 411... Insulator substrate, 413... Semiconductor region.

Claims (1)

[Claims] 1. A liquid crystal is sealed within a pair of substrates, pixel electrodes arranged in a matrix on one of the substrates, and a thin film transistor connected to the pixel electrode, the thin film transistor comprising: A channel region made of an amorphous silicon thin film, a source electrode and a drain electrode electrically connected to the channel region, the pixel electrode connected to the drain electrode, and the other substrate of the substrate. A liquid crystal display device characterized in that the counter electrode formed in the above forms a charge storage capacitor via a dielectric film.