JPS6328308B2 - - Google Patents

Description

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

Conventionally, this type of device was developed by Japanese Patent Application Laid-Open No. 17599
The display cell described in the patent specification is known.

In the driving switching element of such a display cell, a gate line is placed on the substrate B as shown in FIG.
G ₁ , G ₂ . . . , and an insulating layer I and a semiconductor SC are further laminated over the entire surface thereof. In addition, source lines S ₁ and S ₂ are provided that intersect with the gate lines G ₁ and G ₂ and are in contact with the semiconductor SC, and drains D ₁ , D ₂ , and D that serve as segment electrodes are provided near the intersection of the gate lines and the source lines. ₃ ,
_D4 is provided.

The above semiconductor SC is formed into a thin film, and TFT
(Thin Film Transistor) is used as a driving switching element.

The equivalent circuit shown in FIG. 2 is formed by sandwiching a liquid crystal layer between a substrate having the driving switching element array and a counter substrate provided with a counter electrode (for example, a full surface electrode).

A drive voltage is applied to the gate lines G ₁ , G _{2 . .} . , and a signal is applied to the source lines _{S 1 ,} S ₂ . …
Rn and P ₁ , P ₂ , . . . Pn are tangents, and a row temporary scan is performed.

Further, T ₁₁ , T ₁₂ , T ₂₁ , T ₂₂ , ... are TFTs configured as described above, and C ₁₁ , C ₁₂ , C ₂₁ ,
C ₂₂ , ... are storage capacitors formed between each gate line of the TFT switching element array and its own drain, LC ₁₁ , LC ₁₂ , LC ₂₁ , LC ₂₂ ,
... is a capacitor including a liquid crystal layer formed between drains D ₁ , D ₂ , D ₃ , D ₄ ... and a grounded counter electrode (not shown).

On the other hand, as a display cell similar to the above, I EE E
Trans.on Electron Devices ED−20, P.995
(1973).
FIG. 3 shows a plan view of a portion of a driving switching element segment related to such a cell.

That is, a plurality of gate lines G ₁ , G _{2 .} . . are provided on a substrate such as glass, and a semiconductor SC is provided on this via an insulating layer (not shown). A source line S ₁ is provided in contact with one end of the semiconductor SC, and a drain D ₁ of a display segment is provided in contact with the other end. The drain D ₁
Opposed to the lower surface of the gate line _G2 is an electrode P electrically connected to the gate line _{G1 adjacent to the gate line G2} provided with the semiconductor SC. An equivalent circuit of this configuration is shown in FIG. In this equivalent circuit diagram, (as in Figure 2) T ₁ is the TFT shown in Figure 3, and LC ₁ is the drain
A capacitor containing a liquid crystal layer formed between D ₁ and a grounded counter electrode (not shown), C ₁ is
Electrode P electrically connected to the drain of the TFT and the gate line G ₁ adjacent to the gate line G ₂ 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, the first
In the display device equipped with the drive switching element illustrated in the figure, as shown in the equivalent circuit of Figure 2, the opposite electrode of the storage capacitor _C11 is the gate line for addressing. ,
To apply a given voltage to this capacitor,
A differential voltage with respect to the gate signal voltage must be supplied to _P1 . Furthermore, the capacitance component of liquid crystal LC ₁₁
When has non-negligible magnitude, C ₁₁ and LC ₁₁
A signal corrected according to the capacitance ratio of P1 must be given to _P1 , which requires complex signal processing. Another problem is that in a cell having such a structure, the semiconductor forming a part of the structure is opaque, and it is difficult to make the display part 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. 4, if G ₁ is grounded when G ₂ is ON, then
The signal voltage of S ₁ is accumulated in C ₁ , and after G ₂ is turned off, the predetermined voltage applied to S ₁ is applied to LC ₁ , so there is no problem from the perspective of the circuit.

However, although 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 _C1 , an electrode P must be formed under the drain _D1 via an insulating layer (not shown). Generally, D ₁ is the display pixel unit.
When it is desired to increase the effective display area and at the same time increase the density of this picture element, the gate line _G1 , which is the non-display area, 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 construct the counter electrode P of the display picture element, that is, 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 undesirable because it makes the processing method difficult and increases the number of processing steps when forming a fine pattern. In this way, the configuration shown in Figure 3 is more convenient from a circuit perspective than the one shown in Figure 1, and also has the advantage of being able to configure a transmission type cell, but it has the drawbacks of being complicated to manufacture and requiring more processing steps. have

The present invention has been made in view of the above points, and a first object thereof 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 device of the present invention that achieves the above-mentioned objects has a first substrate provided with a thin film transistor array as a driving switching element, and a second substrate provided with a counter electrode, and has a The display device is configured to perform display using electro-optical changes that occur, and is characterized in that the thin film transistor array is placed on a conductive film formed on the first substrate surface with an insulating layer interposed therebetween.

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 TC ₁ is formed over the entire surface of a substrate B ₁ made of glass or the like. Furthermore, an insulating layer _I1 is laminated on this upper surface. In the present invention, a normal TFT array is constructed on a substrate subjected to such processing. Gate lines G ₁ and G ₂ are provided on the insulating layer I ₁ , 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. An insulating layer I ₂ is separately formed on the entire surface of the gate lines G ₁ , G ₂ , . . . . Then, thin film semiconductors _{SC 1 ,} SC ₂ ,
SC ₃ , SC ₄ , . . . are formed as shown. Source lines S ₁ , S 2 , _. . . are in contact with one end of the semiconductors SC 1 , SC ₂ , SC ₃ , SC ₄ , _. . . and are perpendicular to the gate line.
are provided, and drains D ₁ , D ₂ , D ₃ , D ₄ , . . . are further provided in contact with the other end of each semiconductor. These drains D ₁ , D ₂ , D ₃ , D ₄ . . . all serve as one electrode of a storage capacitor and at the same time serve as segment electrodes for display picture elements. FIG. 6 shows a partial cross-sectional structure of a display cell in which an electro-optic modulating material is sandwiched between a substrate having a driving switching element array constructed as described above and a separate substrate having electrodes formed on one side thereof. . In addition,
The configuration of the substrate on the lower side of the drawing in FIG. 6 is a cross-section taken along line A-A' in FIG. And the sixth
In the figure, regarding the lower substrate, those using the same symbols as in FIG. 5 are the same members, and the explanation of FIG. 5 will be referred to and the explanation thereof will be omitted here. A thin film electrode TC ₂ is formed on one side of the substrate B ₂ on the upper side of the drawing. These two substrates B ₁ and B ₂ face each other with a spacer (not shown) in between so as to maintain a predetermined gap, and after sandwiching the electro-optic modulating material LC, the surroundings are hermetically sealed, and the display shown in FIG. 6 is obtained. The device is configured. FIG. 7 shows an equivalent circuit for one picture element of such a display device. In Figure 7, S ₁ , S ₂
is a source line, and G ₁ and G ₂ are gate lines, which are the same elements as shown in FIG. LC ₁ is a display picture element composed of a drain electrode D ₁ and a counter electrode TC ₂ sandwiching an electro-optic modulation material LC. C ₁ is a storage capacitor, which is formed by a drain electrode D ₁ and an electrode TC ₁ specific to the present invention via an insulating layer I ₁ . T ₁ is a MOS type in which a source electrode S ₁ and a drain _{D 1 are} formed with a predetermined gap, which is ohmicly connected to the semiconductor SC ₁ provided on the gate component of G ₁ via an insulating layer I 2. This is a transistor.

The feature of the present invention according to the illustrated example described above is that _C1 can be operated with the counter electrode always grounded, and is easy to operate 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 making the gate line thinner, it is possible to use a structure such as a transparent conductive film for TC ₁ . . Moreover, in such a configuration, the semiconductors SC ₁ ,
Since a metal gate is provided only in the lower part of SC ₂ , SC ₃ , SC ₄ , etc., the semiconductors SC ₁ , SC ₂ , SC _{3 ,} etc. are
An added effect is that SC ₄ ... can be prevented from producing photoconductive effects.

The effects of the present invention are not limited to the use of a transmission type configuration. That is, when configuring a reflective display device, it is possible to form a conductive film TC ₁ of the same material as the reflective metal of each drain in the gap between each pixel of the drain and the source line. , a display surface having apparently optically uniform reflectivity can be constructed, and the operational effects as described above can also be obtained with a configuration 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 further enhanced 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 sixth
In the structure according to the present invention shown in the figure, a conductive layer TC ₂ is formed on the entire surface of the upper substrate B ₂ and another conductive layer TC ₁ is formed below the circuit structure layer of the lower substrate B ₁ . If both are grounded as shown in Figure 2, this TFT array circuit section provides a shielding effect against external electric fields. This shielding effect is MOS
This structure is advantageous for stable operation of the transistor. Further, in the present invention, since these conductive films TC ₁ and TC ₂ are electrically independent, a predetermined bias voltage can be applied to only one or both of them, if necessary.

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

The materials used in the present invention are as substrates B ₁ and B ₂ ;
Glass is generally used, but if the display device is of a reflective type, one side may be made of an opaque material such as metal or ceramics.

Conductive materials, namely gate lines G ₁ , G ₂ , ..., source lines S ₁ , S ₂ , ..., drains D ₁ , D ₂ , D ₃ , D ₄ , ...
For the counter electrode TC ₂ and the conductive film TC ₁ , if transparency is required, a thin film of transparent conductive inorganic oxide such as In ₂ O ₃ or SnO ₂ may be used. ,
A thin film made of metal or alloy such as Cr, Ni, Mo, Si, etc. is used. Furthermore, as an insulating layer, SiO, SiO ₂ , TiO ₂ ,
Metal oxides such as ZrO ₂ , Al ₂ O ₃ , CeO _{2 ,} MgF ₂ ,
It is appropriately selected from halides such as _CaF2 , silicon dioxide, etc. Semiconductor SC ₁ , SC ₂ , SC ₃ , SC ₄ ,...
As the material, CdS, CdSe, Se, Te, amorphous silicon, 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, DAP,
It can be any type such as DSM, HAN, guest host, phase change, etc., and depending on the selected mode and display effect, suitable optical detection means (λ/4 plate, polarizing plate, reflector, color filter, lens, A lighting device) is selected as appropriate and added to the device of the present invention.

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

[Brief explanation of the drawing]

FIGS. 1 and 3 are explanatory diagrams showing configuration examples of conventional drive switching element arrays, and FIGS.
The figures are equivalent circuit diagrams according to FIG. 1, and FIG. 4 is an equivalent circuit diagram according to FIG. 3. FIG. 5 is a schematic configuration diagram of a driving switching element array installation board according to the present invention, FIG. 6 is a partial cross-sectional view of a configuration example of a display device of the present invention, and FIG. 7 is a diagram showing a display device of the present invention. FIG. 3 is an equivalent circuit diagram of one picture element in the device. In the figure, B ₁ and B ₂ are substrates, TC ₁ is a conductive film,
TC ₂ is a thin film electrode, I ₁ , I ₂ are insulating layers, G ₁ , G ₂ are gate lines, S ₁ , S ₂ are source lines, SC ₁ , SC ₂ , SC ₃ , SC ₄
is a semiconductor, D ₁ , D ₂ , D ₃ , and D ₄ are drains, and LC is an electro-optic modulation material.

Claims (1)

[Claims] 1. A substrate, a thin film transistor array provided on the substrate, and a conductive film interposed between the substrate and the thin film transistor and over the entire surface of the substrate, so that the conductive film and A thin film transistor substrate comprising a storage capacitor formed between a drain of the thin film transistor and a segment electrode connected to the drain of the thin film transistor. 2. Claim 1, wherein the thin film transistor includes amorphous silicon as a semiconductor.
The thin film transistor substrate described in Section 1. 3. The thin film transistor substrate according to claim 1 or 2, wherein the conductive film is connected to a ground potential point and an electrical point. 4. The thin film transistor substrate according to claim 1 or 2, wherein the conductive film is connected to a bias potential point and an electric point.