JPH0225A - Driving device - Google Patents

Abstract

PURPOSE:To shield a thin film transistor (TR) from an external voltage by forming a conductive layer on the entire surface of an upper substrate and another conductive layer below the circuit constitution layer of a lower substrate and grounding the both. CONSTITUTION:A thin film electrode TC2 is formed on one side of the upper substrate B2. Then both substrates B1 and B2 are faced each other across a spacer so as to leave a specific gap and an electrooptic modulating material LC is sandwiched; and then the periphery is sealed to constitute a display device. In this constitution, metal gates are provided only below semiconductors SC1, SC2, SC3, SC4, etc., so the semiconductors SC1, SC2, SC3, SC4... are prevented from causing photoconductive influence with light which is made incident on the respective semiconductors from the side of the lower substrate B1 and the thin film TR can be shielded from the external voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a display driver, and more particularly to a display driver having a substrate provided with a thin film transistor (TPT) array of a novel configuration.

[Prior art]

Conventionally, as this type of device, a display cell described in Japanese Patent Laid-Open No. 17599/1984 is known.

In the switching element for driving such a display cell,
As shown in FIG. 6, gate lines Gl, G, .
. . . Furthermore, an insulating layer (1) and a semiconductor SC are laminated over the entire surface of these layers. In addition, a source line Sls S2 is provided which intersects with the gate lines G, , G, and is in contact with the semiconductor SC, and drains D1, D2, D3, and D4, which serve as segment electrodes, are provided near the intersection of the gate line and the source line. .

The semiconductor SC is formed in the form of a thin film, and TFT (Th
nF i l m T r a n s i s t
o r ) It is a driving switching element as typified by T.

The equivalent circuit shown in FIG. 7 is formed by sandwiching a liquid crystal layer between the substrate having the drive switching element array and the counter substrate provided with counter electrodes (for example, full-surface electrodes).

A drive voltage is applied to the gate line G 1 #G 11 w ”-, a signal is applied to the source lines s, , S2e-”, and appropriate row generation paths (R1゜R2-R , and P 1 e Plg·-pIl) are tangent and a row-time scan is performed.

Also, T11. T,,, T,,, T22. --- is a TPT configured as described above, and C11s
CL! wC21e CKM e "" is a storage capacitor formed between each gate line of the TPT switching element array and its own drain, LC11m l
ctt t t, c gt IL Cne "-" is a capacitor including a liquid crystal layer formed between a drain CD*-D2e D3e n4°...) and a grounded counter electrode (not shown).

On the other hand, as a display cell similar to the above, IEEE Tran
s.

on Electron Devices ED
-20, P. 995 (1973).

A plan view of a portion of a driving switching element segment related to such a cell is shown in FIG.

That is, a plurality of gate lines Gl, G, . . . are provided on a substrate made of glass or the like, and a semiconductor SC is provided thereon via an insulating layer (not shown). A source line S11 is provided at one end of the semiconductor SC, and a drain D1 of a display segment is provided at the other end in contact with the source line S11. On the lower surface of the drain D1, a gate line G! adjacent to the gate line G2 provided with the semiconductor SC! Electrodes P that are electrically connected are facing each other. An equivalent circuit of this configuration is shown in FIG. In this equivalent circuit diagram,
(Similar to Figure 7) TI is TFT%L shown in Figure 3.
Cl is a capacitor, C1, including a liquid crystal layer formed between a drain D1 and a grounded counter electrode (not shown).
is an electrode P that is electrically connected to the drain of the TFT and the gate line (G1) adjacent to the gate line (G2) corresponding to the drain.
This is a storage capacitor formed between the

In a circuit like the one described above, the moment a signal is applied to a selected gate line, the voltage of the source line is applied to the drain and a display is produced. Its rise time constant is determined by the product of the on-resistance of the semiconductor and the capacitance (the sum of the capacitor including the liquid crystal layer and the storage capacitor).

However, both of the display cells described above have problems that need to be solved. For example, in the display device equipped with the driving switching element illustrated in FIG.
As shown in the equivalent circuit in the figure, the opposite electrodes of storage capacitors 〇 and 1 are the opposite electrodes of the gate line for addressing, and in order to apply a predetermined voltage to this capacitor, The differential voltage must be supplied to Pl. Furthermore, when the capacitance component LC1□ of the liquid crystal has a size that cannot be ignored, a signal corrected according to the capacitance ratio between C□ and LC11 must be given to P, which requires complicated signal processing. Another problem is that in a cell having such a structure, the semiconductor forming a part of the structure may be opaque, and it is difficult to make the display section a transmissive type in the sense that it has photoconductivity.

On the other hand, in the configuration of the display device equipped with the driving switching element shown in FIG. 3, as shown in the equivalent circuit of FIG.
is ON, if G1 is grounded, the signal voltage of S1 is C
, and after G2 is turned off, the predetermined voltage applied to S1 will be applied to LCl, causing no problem from the perspective of the circuit.

However, since this cell originally has a structure that allows a transmission type structure, problems arise when actually manufacturing it as a transmission type cell. That is, as a counter electrode of the storage capacitor 08, P is connected below the drain D through an insulating layer (not shown).
In general, when you want to increase the effective display area of DI, which is a display pixel unit, and at the same time increase the density of this pixel, the gate line G1, which is a non-display area, must be formed. The wire must be made as thin as possible. However, if the wire is made thinner, the resistance value will increase, so in this respect it is necessary to use a metal film with good conductivity.

Therefore, if a transparent conductive film is used to constitute the display picture element, that is, the counter electrode P of the drain D1, as a transmission type, members different from the gate line metal and the transparent conductive film will be used. This configuration is not preferable because it makes the processing method difficult and increases the number of steps when forming a fine pattern. In this way, the configuration shown in Figure 3 is more convenient than the one shown in Figure 1 in terms of circuitry, and has the advantage of being able to configure a transmission type cell, but it has the disadvantages that it is complicated to manufacture and requires a large number of parts to be added. also have

[Summary of the invention]

Therefore, the present invention has been made in view of the above points,
The first objective is to provide a display device having high density pixels as a display panel that maintains high reliability and is easy to produce. Another object of the present invention is to provide a display device that exhibits stable and uniform image characteristics using a simple driving method. Furthermore, another object of the present invention is to provide a transmissive display panel suitable for the above two purposes.

A display driving device of the present invention that achieves the above objects includes: a) a plurality of thin film transistors arranged along a plurality of rows and columns; a gate line commonly connecting the gates of the plurality of thin film transistors arranged along the rows; A source line that commonly connects the sources of multiple thin film transistors arranged along a column,
and a segment electrode having a first capacitor and a second capacitor connected in parallel with the drain of each thin film transistor, the first capacitor being connected to the drain of the thin film transistor, a first counter electrode disposed opposite to the segment electrode, and a first counter electrode disposed opposite to the segment electrode. A second capacitor is formed by a liquid crystal layer disposed between a segment electrode and a first counter electrode, and a second capacitor is disposed opposite to the segment electrode, and a second capacitor is disposed opposite to the back surface of the segment electrode and insulated from the gate of the thin film transistor. a circuit formed of an electrode and an insulating film disposed between the segment electrode and a second opposing electrode, and having a connecting conductive part for commonly connecting the second opposing electrodes of the second capacitor; A driving voltage is applied to the selected gate line, a signal according to image information is applied to the source line, and a bias voltage is applied to the first counter electrode and the second counter electrode electrically independently. The invention is characterized by a drive device having means.

[Detailed description of aspects of the invention]

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 5 is a schematic perspective view of a substrate provided with a driving switching element array according to the present invention. A conductive film TC1 is formed over the entire surface of a substrate B made of glass or the like. Furthermore, an insulating layer 1 is formed on this upper surface. are layered. In the present invention, a normal TFT array is constructed on a substrate subjected to such processing.

A gate line Gl* cll! is placed on the insulating layer ■1. is provided, and a pattern is formed in this gate component so as to extend to the lower surface of the semiconductor that will be superimposed later. This gate line G,
, G, . . . , an additional insulating layer 2 is formed over the entire surface. Then, thin film semiconductors sc, sc2 ., sc2 . sc3゜SC4,・
. . is formed as shown in the figure. This semiconductor sc, .
sc2. sc3. sc4. - a source line s, #521-, in contact with one end of the gate line and perpendicular to the gate line;
... are provided, and a drain D1... is provided in contact with the other end of each of the semiconductors. D,,D3. D4. -... is provided. These drains D1 + D2 w D3 e D4
- and both serve as one electrode of a storage capacitor and also serve as segment electrodes for display picture elements. FIG. 1 shows a partial cross-sectional structure of a display cell having an electro-optic modulating material sandwiched between a substrate having a drive switching element array constructed in this way and a separate substrate having an electrode formed on one side. . Note that the configuration of the substrate on the lower side of the drawing in FIG. 1 is shown in the AA cross section of FIG. 5. In Fig. 1, the same symbols as in Fig. 5 are used for the lower board, and they are the same members.
The explanation of the figure will be omitted here with reference to the explanation of the figure. A thin film electrode TC is formed on one side of the substrate B2 on the upper side of the drawing. These two substrates B, , B are made to face each other with a spacer (not shown) in between so as to maintain a predetermined gap, and after sandwiching the electro-optic modulation material LC, the periphery is hermetically sealed and the first
The display device illustrated in the figure is constructed. An equivalent circuit for one picture element of such a display device is shown in FIG.

In FIG. 2, S, , S are source lines, GK and G2 are gate lines, which are the same elements as shown in FIG. 5.

LC□ is a display picture element composed of a drain electrode and a counter electrode TC sandwiching an electro-optic modulating material LC. C
Reference numeral 1 denotes a storage capacitor, which is formed by a drain electrode D1 and an electrode TC1 specific to the present invention, with an insulating layer 2 interposed therebetween.

TI is a MOS transistor in which a source electrode S1 and a drain D are formed with a predetermined gap and are ohmically connected to a semiconductor SC□ provided on a Gi gate component via an insulating layer 2. be.

The feature of the present invention according to the above-described illustrated example is that C1 can be operated with its opposite pole always grounded, and is easy to operate in a manner similar to the equivalent circuit shown in FIG. 4 described above. In addition, since the gate line and the counter electrode of the storage capacitor are not integrated, it is not necessary to use the same material, and there is no need to pattern the counter electrode of the storage capacitor. sex is brought about. In other words, if a metal member with good conductivity is used to prevent the resistance value from increasing when the gate line is made thinner, a structure such as a transparent conductive film can be used for TCl. . Also, in such a configuration, the semiconductor SC.

sc,,sc 3. Since a metal gate is provided only at the lower part of the semiconductors sc 4-, etc., the semiconductors sc, , sc2°5C,
, SC4-... can be prevented from producing photoconductive effects.

The effects of the present invention are not limited to the adoption of a transmission type configuration. That is, when configuring a reflective display device, if a conductive film TC is formed from the same material as the reflective metal of each drain in the gap between each picture element of the drain and the source line, A display surface having optically uniform reflectivity can be constructed, and the operational effects as described above can also be obtained with a construction that is easy to manufacture. Furthermore, as described above, the effect of blocking light incident from the side of the lower substrate B1 can be enhanced more than in the case of a transmissive display device.

The present invention also has other effects that can be obtained with either the transmission type structure or the reflection type structure. That is, the structure according to the present invention shown in FIG. 1 has a conductive layer TC on the entire surface of the upper substrate B2.
,,Another conductive layer TC1 is provided below the circuit structure layer of the lower substrate B1.
is formed, and if both are grounded as shown in FIG. 2, this TFT array circuit section provides a shielding effect against external electric fields. Such a shielding effect is advantageous for stable operation of a transistor having a MOS structure. Further, in the present invention, these conductive films TC.

Since Te3 is electrically independent, a predetermined bias voltage can be applied to only one or both, if necessary.

As described above, the present invention has both manufacturing technology advantages and driving effects related to display devices.

The material used in the present invention is generally glass as the substrate (B*t B2), but when the display device is of a reflective type, one side is made of metal or ceramic.

It may also be made of an opaque material such as camphor.

Conductive materials, i.e. gate lines G,,G,, -.-, source lines Sls S! w”..., drain D,,D,,D3
゜D4. -...The counter electrode "C2m conductive film TC,"
When transparency is required, a thin film of transparent conductive inorganic oxide such as In 203 or Sn 02 may be used.
1. Ag, Pd, Pt, Cr, Ni,
A thin film made of metal or alloy such as Me or Si is used. Furthermore, as an insulating layer, Sin, Si02, Ti02
, Zr02, AjF 203.

Metal oxides such as CeO2, MgF2. It is appropriately selected from halides such as CaF2, silicon nitride, and the like. The semiconductors SC,,SC2,SC3,SC4,-... are Cd
Amorphous silicon other than S, CdSe, Se, Te, etc. are selectively used.

As the electro-optic modulation material LC, liquid crystal, EC (electrochromy), EL (electroluminescence), etc. are used. The liquid crystal used may be a single liquid crystal or a mixture of liquid crystals exhibiting nematic, cholesteric, or smectic properties depending on the display operation mode.

These display operation modes are so-called TN and DAP.

It can be any type such as DSM, RAN, guest host, phase change, etc. (Depending on the selected mode and display effect, use appropriate optical detection means (λ/4 plate, polarizing plate, reflector, color filter, lens). , lighting device) are selected as appropriate and added to the device of the present invention.

〔Effect of the invention〕

Since the counter electrode of the capacitor used in the present invention is insulated from the gate line, the bias voltage can be set independently of the gate line, and the insulating film that becomes the capacitor is the sixth
As shown in the figure, since the conductive film for the capacitor counter electrode is formed extending from the insulating film used to insulate the capacitor from the gate, the conductive film for the capacitor counter electrode can be formed over the entire surface of the substrate. Therefore, the thin film transistor can be shielded from external voltage.

Therefore, according to the present invention, even if a bias voltage is set on the conductive film of the counter electrode of the capacitor, for example, in order to provide temperature compensation for driving the liquid crystal, the thin film transistor does not malfunction due to this voltage.

The display device made of soft clay according to the present invention has good drive performance, productivity, and reliability, and has high-density pixels, and can be used as a small display device for televisions,
It can be suitably used for display devices such as video camera monitors.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a configuration example of a display device of the present invention, and FIG. 2 is an equivalent circuit diagram of a -picture element in a driving device of the present invention. Figure 3 and 6th floor! 4 is an explanatory diagram showing a configuration example of a conventional driving switching element array, FIG. 4 is an equivalent circuit diagram of FIG. 3, and FIG. 5 is an illustration of a driving switching element array installation board according to the present invention. The schematic configuration diagram, FIG. 7, is an equivalent circuit diagram of FIG. 6. In the figure, Blp B11 is a substrate, TC is a conductive film,
TC2 is a thin film electrode, ■1.1□ is an insulating layer, G, ,G. is a gate line, SL, S2 are source lines, SC1, SC2° SC3, SC4 are semiconductors, D1e D2e D35 D
4 is a drain, and LC is an electro-optic modulation material.

Claims (1)

[Claims] a. A plurality of thin film transistors arranged along a plurality of rows and columns, a gate line that commonly connects the gates of the plurality of thin film transistors arranged along the rows, and a plurality of thin film transistors arranged along the columns. a source line to which the sources of the thin film transistors are commonly connected, and a first capacitor and a second capacitor connected in parallel to the drain of each thin film transistor, a segment electrode in which the first capacitor is connected to the drain of the thin film transistor; a liquid crystal layer disposed between the segment electrode and the first counter electrode; Formed by a second counter electrode insulated from the gate of the thin film transistor and an insulating film disposed between the segment electrode and the second counter electrode, and for commonly connecting the second counter electrodes of the second capacitor. and (b) applying a driving voltage to the selected gate line, applying a signal according to image information to the source line, and electrically connecting the first counter electrode and the second counter electrode. A drive device having means for independently applying a bias voltage.