JPS6361228A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To reduce the occurrence of short-circuit accident by using a laminated body consisting of a transparent electrode material layer consisting of the same material as a display electrode and a metallic layer having a small resistance value as the source bus to which plural thin film transistors TRs are connected and forming this metallic layer of the source bus on the transparent substrate side. CONSTITUTION:The gate bus 18 of a liquid crystal display element is formed and extended on a gate electrode 23, and a source electrode 19a is connected to a source bus 19 by a connecting part 40. The laminated body consisting of a metallic layer 41 having a small resistance value and a transparent electrode material layer 42 consisting of the same material as a display electrode 15 is used as this bus 19. The metallic layer 41 is formed on the side of a transparent substrate 11 where a thin TR 16 is formed, and a first insulating layer 44 is formed on the metallic layer 41 of the bus 19 in a crossing part 43 between busses 19 and 18, and a semiconductor layer 45 is formed on the layer 44. A second insulating layer 6 is formed on the layer 45, and the bus 18 is formed on the layer 46. A three-layered part is interposed between source and gate busses 19 and 18 to reduce the short-circuit accident.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid crystal display device in which pixel electrodes serving as display electrodes are arranged in a matrix, and an image is actively displayed by selectively driving the pixel electrodes using thin film transistors. .

[Conventional technology]

In a conventional liquid crystal display element of this kind, for example, as shown in FIG. 1, transparent substrates 11 and 12 made of glass are provided close to each other, and a spacer 13 is interposed between the peripheral edges of these transparent substrates 11 and 12. A liquid crystal 14 is sealed between these transparent substrates 11 and 12 to constitute a liquid crystal cell IO.

A plurality of display electrodes 15 are formed on the inner surface of one transparent substrate 11, and a thin film transistor 16 is formed as a switching element adjacent to each display electrode 15, and the drain of the thin film transistor 16 is connected to the display 1 element 15. There is. A transparent common electrode 17 is formed on the inner surface of the other transparent substrate 12, facing the plurality of display electrodes 15.

The display electrodes 15 are, for example, pixel electrodes, and as shown in FIG. 2, square display electrodes 15 are arranged close to each other in rows and columns on the transparent substrate 11. Gate paths 18 are formed along these lines, and source buses 19 are formed adjacent to and along each column arrangement of display electrodes 15. A thin film transistor 16 is provided at each intersection of each gate path 18 and source bus 19, a dart of each thin film transistor 16 is connected to the dirt path 18, each source is connected to the source bus 19, and each drain is connected to the display electrode 15. I got 1 hit.

By selecting each of these f-) paths 18 and source buses 19 and applying a voltage between them, only the thin film transistor 16 to which that voltage has been applied becomes conductive, and is connected to the drain of the thin film transistor 16 that has become conductive. Display electrode 15
By accumulating electric charge in the display electrode 15 and applying a voltage only to the part of the liquid crystal 14 between the display electrode 15 and the common electrode 17, and thereby making only the part of the display electrode 15 transparent or light-blocking. Perform selective display. The display can be erased by discharging the charges accumulated in the display electrodes 15.

Conventionally, the seven-film transistor 16 has been constructed as shown in FIGS. 3 and 4, for example.

That is, a display electrode 15 and a source bus 19 are formed on a transparent substrate 11 using a layer of a transparent electrode material such as ITO, and a layer of a transparent electrode material such as amorphous silicon is formed across the parallel adjacent portions of the display electrode 15 and source bus 19. semiconductor layer 2
1 is formed, and a dirt insulating film 22 made of silicon nitride or the like is further formed thereon. A dirt electrode 23 is formed on the dirt insulating film 22 so as to partially overlap the display electrode 15 and the source bus 19 with the semiconductor layer 21 interposed therebetween. One end of date electrode 23 is connected to gate path 18 . In this way, the display electrode 15 and the source bus 19, which respectively face the dirt electrode 23, constitute a drain electrode 15a and a source electrode 19a, respectively, and these electrodes 15a
, 19a, the semiconductor layer 21, the dirt insulating film 22, and the dirt electrode 23 constitute the thin film transistor 16. The date electrode 23 and the gate path 18 are formed at the same time and are made of aluminum, for example. Also, this electrode 1
Ohmic contact layers 25 and 26 on 5a and 19a, respectively
is formed of, for example, an n-plus layer, and the contact resistance with the semiconductor layer 21 is considered to be small.

[Problem that the invention seeks to solve]

In a conventional liquid crystal display element of this type, when the display area is widened and the display is performed with high resolution, the display electrode 1
5 needs to be made dense, and the length of the source bus 19 becomes long. Therefore, the voltage on the source bus 19 differs between the voltage applied to the source bus 19 and the side further away due to voltage drop. Furthermore, signal waveforms occur as the time constant of the source bus increases, and as a result, uniform brightness over the entire display surface cannot be obtained, and a brightness gradient occurs in which the brightness decreases in areas farther from the power source. Also source bus 19
The longer the length of the path, the more likely the path will be disconnected. Furthermore, if the width of the source bus is made narrow in order to minimize disconnection of the source bus and to reduce the resistance value of the source bus, the ratio of the effective display area to the entire display surface of the display element, so-called aperture ratio, decreases.

[Means for solving problems]

According to the present invention, in a liquid crystal display element, the source bus to which the sources of a plurality of thin film transistors are connected is made of a laminate of a transparent electrode layer made of the same material as the display electrode and a metal layer whose resistance value is smaller than that of the transparent electrode layer. 9, and the metal layer of the stack is on the side of the transparent substrate on which the source bus is formed.

In this way, the overall resistance value of the source bus is small, the voltage drop is small, the time constant is small, and the waveform of the drive signal is not distorted. Furthermore, since it is a laminate, disconnection failures are less likely to occur, and the resistance value is low, so it can be made thinner.

The aperture ratio can be reduced.

Note that at the intersection of the source bus and the r-) path, short-circuit defects between the source gas and the dirt bus can be reduced by interposing a three-layer furnace layer between the source bus and the gate path.

〔Example〕

5 to 7 show main parts of a liquid crystal display element according to the present invention, and parts corresponding to those in FIGS. 2 to 4 are given the same reference numerals.

In this example, the gate bus 18 is formed to extend over the r-) electrode 24, and the source electrode 19a is connected to the source bus 19 at the connecting portion 40.
I am trying to connect to.

According to the present invention, as shown in FIG. 6, the source bus 19 includes a relatively resistive metal layer 41 made of, for example, chromium, and a transparent electrode material layer of, for example, ITO, made of the same material as the display electrodes 15. The metal layer 41 is on the side of the transparent substrate 11 on which the thin film transistor 16 is formed.

Further, in this example, at the intersection 43 of the source bus 19 and the gate path 18, S
A first insulating layer 44 such as iO2 is formed, and a semiconductor layer 4 such as amorphous silicon is formed on the first insulating layer 44.
5 is formed, and further thereon, for example, silicon nitride SiN
A second P edge layer 46 of x is formed on which a gate path 18 is formed, for example of aluminum. Three layers, a first insulating layer 44 , a semiconductor layer 45 , and a second insulating layer 46 , are interposed between the toe PR-top path 18 and the source bus 19 .

In this example, as shown in FIG. 6, in the thin film transistor 16 part, a light shielding layer 48 is formed on the transparent substrate 11 side facing the semiconductor layer 22, and the semiconductor layer 2 is formed from the transparent substrate 11 side.
The light incident on the semiconductor layer 2 is blocked by the light shielding layer 48.
The deterioration of the on-off ratio of the thin film transistor 16 due to the photoconductive effect of No. 2 is made small. This light shielding layer 48 is made of a metal layer such as chromium, and in order to insulate between the light shielding layer 48 and the display electrode 15 and the case electrode 19a, there is a gap between the light shielding layer 48 and the semiconductor layer 22, the display electrode 15, and the source electrode 19a. S
An insulating layer 49 such as iO2 is interposed.

For example, a chromium layer is formed on the inner surface of the transparent substrate 11, and this is etched in several turns to form the metal layer 41 of the source bus 19 and the light shielding layer 48 at the same time, and the metal layer 41 is masked. A first insulating layer 44 and an insulating layer 49 are formed at the same time by forming a 02 layer and then etching it. Furthermore, after forming ITO, the display electrode 15 and the transparent electrode material layer 4 of the source bus are formed by pattern etching.
2 is formed, and then semiconductor layers 22 and 45 are simultaneously formed of amorphous silicon. Thereafter, the gate insulating film 23 and the second insulating layer 46 are formed simultaneously, and after the dirt electrode 24 is formed, a protective layer 51 of silicon nitride or the like is formed over the entire structure. By adopting such a manufacturing process, the source bus 19 has a two-layer structure, and the source bus 19
It is possible to interpose a three-layer laminated portion at the intersection between the gate path 18 and the gate path 18 at the same time as forming the thin film transistor 16 with a light-shielding layer.

The display electrode 15 is not limited to a pixel electrode, and the present invention can also be applied to a case where seven bar-shaped display electrodes arranged in a mouth shape are selected to display numbers.

The transparent electrode material layer 42 is not limited to ITO, but may also be SnO□, and each of the above insulating layers may be 5i02, SiN
In addition to x, polyimide, SiO+Az203, and other inorganic or organic materials may be used.

〔Effect of the invention〕

As described above, since the source bus of the liquid crystal display element of the present invention has a two-layer structure, even if a defect such as a pinhole occurs in one of the metal layer 41 and the transparent electrode material layer 42, it will not affect the other. It is virtually possible for defects such as pinholes to occur at the same location; in other words, defects and disconnections compensate for each other, resulting in a source bus free from defects and disconnections.

The connection of the metal layer 41 to the transparent electrode material layer 42 is, for example, C
Since the resistance of r to ITO is about 1/10, the resistance of the source bus 19 can be made small, the brightness gradient is sufficiently small, and the distortion of the drive signal waveform is also small. The width could be reduced to 10 μm or less, and an aperture ratio of 70% could be obtained even with a pitch of 20011 m for one pixel electrode 15.

Further, when a three-layer stacked portion is interposed between the source bus and the gate path as in the above example, short-circuit accidents between the source bus and the source bus are reduced.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a part of a liquid crystal cell, Figure 2 is a diagram showing an electrical equivalent circuit of a liquid crystal display element, Figure 3 is a plan view of a part of a liquid crystal cell, and Figure 4 is a diagram of a part of a liquid crystal cell. 5 is a plan view showing a part of an example of the liquid crystal display element of the present invention, FIG. 6 is a sectional view taken along the BB line in FIG. 5, and FIG. 70 is a sectional view taken along the CC line in FIG. 5. It is. Agent Takuo Kusano 1
1 source bus for Tugaozu Sai 2 Illustrations 3 Engraving of drawings (no changes to the content) 5 Engraving of Hizu drawings (no changes to Baiyun) Formula% 1, Incident Display Patent Application 1986-206246'
2. Title of the invention: Liquid crystal display element 3. Person making the amendment: Relationship to the case: Patent applicant: Hoshi Denki Manufacturing Co., Ltd. 4, Agent: 2-21 Shinjuku 4-chome, Shinjuku-ku, Tokyo
No. Sagami Building (located at 03-350-6456-7) Contents of the amendment (1) As per the engraving and attached sheet of the specification originally attached to the application (no change in content) (2) Amendment to the drawings originally attached to the application Engraving (Fig. 5, Fig. 6, Fig. 7) / As shown in the attached sheet (Contents changed procedure amendment stamp button (3) ``Reducing the aperture ratio'' on page 6 of the same book, line 18)
A-4 illustration 5 mouths

Claims (1)

[Claims] (1) A liquid crystal cell is constructed by placing a first and second transparent substrate close to each other and encapsulating a liquid crystal, and a plurality of transparent display electrodes are formed on the inner surface of the first transparent substrate, and each of these display electrodes has a drain. The electrodes are connected and the thin film transistor is connected to the first
formed on a transparent substrate, a plurality of source electrodes of the thin film transistors are connected to a source bus, and a plurality of gate electrodes of the thin film transistors are connected to a gate bus;
In a liquid crystal display element in which a common electrode is formed on the inner surface of the second transparent substrate facing the display electrode, the source bus has a transparent electrode layer made of the same material as the transparent display electrode, and a resistance value of the transparent electrode layer. 1. A liquid crystal display element comprising a laminate including a metal layer having a small diameter, wherein the laminate has the metal layer on the side of the first transparent substrate.