JPS61169882A - Liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Field of Application of the Invention" The present invention provides a display panel using ferroelectric liquid crystal (hereinafter referred to as FLC) to solidify the display part of a microcomputer, word processor, television, etc. The present invention relates to a liquid crystal display device.

``Prior Art'' For solid-state display panels, a system in which each picture element is controlled independently is effective for large-area displays. Conventionally, such panels use dual-frequency liquid crystals, such as twin-stick nematic liquid crystals (hereinafter referred to as TN liquid crystals), and are multi-branched into a simple matrix structure of 44-size size with 400 elements in the horizontal direction and 200 elements in the vertical direction. Display devices using this driving method are known.

However, it has been found that it is impossible to use TN liquid crystal to create a large-area display device with a larger number of pixels due to limitations in frequency characteristics.

In addition, even if each pixel is spaced apart by a predetermined distance and arranged in a matrix, crosstalk (a phenomenon of weak electrical conduction) is likely to occur between adjacent pixels. Therefore, even if one has an ON function and the other has an OPP function, each pixel cannot be turned ON or OFF sufficiently, resulting in insufficient contrast.

In order to eliminate this drawback, a method is known in which an active element is connected to each pixel. A typical example is one that uses TPT (thin film type insulated gate field effect semiconductor device) as the element.

Also, a method using a nonlinear element is known.

Further, in a passive configuration (simple matrix type), attempts have been made to use FLC as the liquid crystal instead of the conventionally known TN type liquid crystal, but this has cross talk and is not the best.

This FLC is a bistable liquid crystal that has a memory function, and has particularly excellent frequency characteristics.

"Problems to be Solved by the Invention" As described above, we are considering a method that combines these methods, that is, a method that uses a passive method (hereinafter referred to as P) or TPT, and a method that uses TN or FLC for the liquid crystal. Then, the result will be as shown in Table 1 below.

Table 1 □ However, ◎ indicates very good, O indicates good, △ indicates slightly poor, and × indicates poor.

When considering the above four methods, it was found that there is always an x mark in each method, and that there is no final answer in any of these methods.

As a result, methods other than these four methods are required.

The present invention solves this problem.

"Means for Solving the Problem" In order to solve the problem, the present invention combines a bidirectional nonlinear element (hereinafter referred to as NE) and an FLC. Below, a comparison is made with an ideal structure as a nonlinear element, a particularly known MIM (conductor-insulating film-conductor) structure, and a diode ring (hereinafter referred to as DR) structure using a PIN junction.

Table 2 shows the outline.

Table 2 As is clear from the above, the present invention has a nonlinear element and an F
LC, both work synergistically and there is no cross talk, the process is not very complicated, and F
The use of LC also improved the viewing angle, and it was found that the configuration was extremely close to the ideal type.

Furthermore, regarding the operating temperature range, which is a problem that remains even in the present invention, it is now possible to use a combination of a plurality of different FLCs in a range of 0 to 50°C. Therefore, it has been found that there is no problem in practical use, and as far as the color adjustment is concerned, if up to eight colors are used, adjustment is not necessary, and it has been found that it is fully usable as a display for a microcomputer or the like. Furthermore, if an MIM structure is used, this capacitor component enters in series with the FLC, which puts a limit on the frequency characteristics of the pixel, but it is still possible to create 400 x 200 pixels without crosstalk.

Therefore, it has been found that it is possible to manufacture a large, large-area liquid crystal display for the first time by using a pixel in which a nonlinear element and a ferroelectric liquid crystal are connected in series, as described in the present invention.

In particular, in the present invention, an MIM diode is used as a nonlinear element, and the configuration of this nonlinear element and a pixel is more integrated.

That is, the nonlinear element used in the present invention mainly has a tantalum-tantalum nitride-tantalum structure or a chromium-silicon nitride-chromium structure.

Furthermore, the present invention can be completed by simply aligning one mask in which the MIM diode, the X wiring constituting the matrix, and the nonlinear element connected thereto have approximately the same shape. One electrode (third electrode) and one electrode (first electrode) of the connected composite diode are connected to a common rectangular electrode, and Y or X wiring on the semiconductor above the common rectangular electrode (in the drawing, only the X wiring Therefore, the process can be carried out using only two sheets of second masks necessary for forming the X wiring (hereinafter representatively referred to as the X wiring). A typical example of the structure of the present invention is shown in FIG. 4, and the manufacturing process thereof is shown in FIG.

Furthermore, in the present invention, since FLC is used as the liquid crystal, the distance between opposing electrodes is typically 1±0
．． Can be made 5μ. Therefore, in addition to being used in a smaller amount than TN liquid crystal, the laminate having the above-mentioned nonlinear elements also acts as a spacer to prevent two electrodes from electrically shorting each other. I can do it.

“Function” Thus, nonlinear elements (NH) and ferroelectric liquid crystals (FLC)
) in series to form each pixel, A
For the first time, it has become possible to eliminate crosstalk between each pixel even for large-area matrices of 4th edition or more.

As shown in Figures 1 and 4, the other X of the ferroelectric liquid crystal
Red (referred to as R) and green (referred to as G) correspond to the wiring.

It has the feature that color display is also possible by passing it through a blue (referred to as B) filter.

The present invention will be explained below according to examples.

"Example 1" FIG. 1 shows a circuit diagram using the solid state display device of the present invention.

In the drawing, the pixel is connected to the electrode of the MIN diode (2) (
21) (first electrode) is connected to one electrode (23) (third electrode) of the ferroelectric liquid crystal (3). The composite diode has a second electrode (
22). On the other hand, the fourth of FLC(3)
The electrode (24) has an X configuration f% @ (6), (7) 2 connection 1
．． ．． Te11. Nru, X number 41! ;! Third electrode (23
) Correspondingly, other transparent insulating substrates are typically used, such as glass substrates (fourth glass substrate closely located on the (20') side in FIG. 4(C)).
electrode (24) ((6 in Fig. 1, Fig. 4(C))
) or (24) ) are respectively connected in correspondence. This fourth electrode (24) has an R, G, or B filter to provide full color.

Examples of the manufacturing process and characteristics of a nonlinear element that is part of a pixel using such a composite diode are shown in Figures 2 and 3.
Shown in the figure.

The manufacturing process shown in FIG. 2 is (40
) is particularly suitable for expanding the manufacturing area.

Figure 2 (A), (B), (C), (D-1
) corresponds to the longitudinal sectional view of FIG. 4A-A'. FIGS. 2(D-2) and (E) correspond to longitudinal cross-sectional views taken along line c-c' in FIG. 4, and show the device structure thereof.

In FIG. 2(A), Corning 7059 glass (20) was used as the light-transmitting insulating substrate. An ITO or tin oxide film serving as a conductive film (13) was formed on this upper surface by sputtering or electron beam evaporation to a thickness of 0.1 to 0.5 μm. In addition, a film for the lower electrode of the MrM structure (14
) For example, chromium was formed to a thickness of 0.1 to 0.2 μm.

Thereafter, a silicon nitride film was formed on the entire surface of these using a photo-CVD method. That is, disilane (SiJJ and ammonia are NH3/S!Jh=30, pressure is 3 torr, substrate temperature is 300 to 450°C, 184ns+, 254ns
irradiated with ultraviolet light. Thus, as a silicon nitride coating, 10
It was possible to form a thickness of 0 to 500 people, for example, 300 people. The breakdown voltage of this silicon nitride film is 350℃ at 300℃4V.
It can be controlled by increasing the temperature of the substrate to 7V and 400°C IOV. For this reason, it was made at 400°C and had an old structure for 5V drive.

After this, add chrome (500 to 1500") to the top surface.
(15) was laminated to a thickness of 0.1 to 0.2 μm by electron beam evaporation or sputtering.

Furthermore, as shown in FIG. 2(B), the first photomask ■
Anisotropic plasma etching was performed so that the peripheral portion (26) was vertical.

Next, a photosensitive polyimide resin (27) was formed on the entire surface of these to a thickness of about 1 μm by a coating method.

Thus, the upper surface of the electrode (15) of the laminate (50) and the upper surface (39) of the polyimide resin (27) have a structure in which the insulator surface and the laminate surface are smoothly continuous after curing except for the convex portions of the laminate. A zero-order glass substrate (20
) was exposed to ultraviolet light from the back side of the glass using a known mask aligner without using a mask. For example, the Cobilt aligner was exposed for about 2 minutes. Ultraviolet light with a wavelength of 300 to 400n− (10a+W
/ca+, 15 to 30 seconds is sufficient.

Then, a laminate (about 1μ thick) with side surfaces (26) (
50), the convex region above it that is in the shadow is not exposed to light, and only the surrounding area on that side is exposed to light. After further development, the non-photosensitive convex portions were dissolved away using a rinsing solution.

Next, do all of this at 180℃ for 30 minutes + 300℃ for 30 minutes +
Cure was performed by heating at 400° C. for 30 minutes in nitrogen. In this way, in addition to exposing the second electrode of the nonlinear element, which is the upper surface of the laminate, without using a photomask, this upper surface and the surface of the polyimide resin insulator in the peripheral area are smoothly connected, and the second electrode It became possible to obtain figure (C).

Next, apply aluminum (16) for the lead (6) to a thickness of 0.5 to 1 μm, for example 0.7 μm, on the entire upper surface of FIG.
1 to 1.5 μm, and then an insulating film is formed on the upper surface of the
For example, a polyimide coat (17) was formed to a thickness of 0.3 μ to obtain Figures 2 (D-1) and (D-2). This insulating film determines the size of the spacer when filling the FLC, and also ensures that the upper electrode and the lead (6) are aligned.
This is to prevent it from being picked up. After this, Figure 2 (E)
As shown in FIG.
Patterning was performed using the mask ■.

That is, insulating film (17), aluminum (16),
Patterning chromium (15) to create an insulating film between the eyebrows (17)
, a second electrode (22) was formed. Furthermore, this electrode is used as a mask for insulation [(2), and chromium (
14) was patterned to obtain Figure 2 (E).

Thus, the lead (6) extending from the second electrode (15) of one pixel extends onto the insulator (27) provided on the side surface of the first electrode in the semiconductor constituting the pixel. It was possible to connect it to the second electrode of the adjacent pixel.

That is, in FIG. 2, a third electrode for FLC made of a transparent conductive film on a glass substrate (20), a first electrode (21) connected thereto, and an insulating film for an MIM stack (2) are shown. )
, chromium second electrode (15), aluminum (1
6) consists of an electrode lead (22). The symbol of this MIM structure is indicated as (2) in FIG.

As a result, the nonlinear characteristics shown in Figure 3 (A) (electrode area 20μ x 420μ) can be achieved corresponding to Figure 2 (the vertical axis shows the absolute value on a log scale). Ta.

Moreover, on the upper side of this, as shown in FIG.
0μ), and in the gap, FLC such as DOBAMB
The threshold characteristics when C is used as the filling material are shown in (B). Even in the drawings, it was found that by applying ±5V, it was possible to make the film transparent and non-transparent, and it was also possible to sufficiently reverse the polarity. Figure 3 (
In B), the vertical axis is the transmittance.

"Example 2" The configuration of the present invention is shown in FIG. 4, and a plan view (^) and a vertical cross-sectional view (B) of the area (1) surrounded by the broken line in FIG.
, (C) and (D) are shown.

Furthermore, Fig. 4 (B), (C), and (D) are (A
), A-A', B-B', C-C', respectively.
In addition, Fig. 4 (C) and (D
) are the liquid crystal (3) and the upper electrode (6).

(7) and the substrate (20') are also shown;
A).

(B) shows only the side having nonlinear elements for simplicity.

The manufacturing method of this element is the same as in Example 1.

That is, the rectangular first electrode (2
1) and a third electrode (23), and a semiconductor having the same shape and a conductor forming a part of the second electrode are formed therebetween. The shape of the transparent conductive film constituting this third electrode was 420μ×420μ.

Further, the size of the laminate is 420μ×20μ. In the drawings, the first, second and third portions on the side and underside of the insulator are shown.
A polyimide resin (29) is coated to cover the electrodes and form an alignment film. In addition, the upper electrode of FLC (
24), (24'), lead (6),
(7) is also coated with an alignment film (29'').

Since the second electrode is provided above the rectangular first and third electrodes, if its position is set at the center from its original position, it will not be linear even if it deviates by ±200μ (maximum) above and below. The electrode area of the element remains unchanged, and patterning is possible without affecting the electrical characteristics (current value) at all. That is 640
For example, a glass substrate (30 cm
X20c■) The upper cloth edge and the lower edge of the mask cause a misalignment of the mask, and it is now possible to align the mask even with poor accuracy, for example, one side is 200μ on the + side, and the other is 200μ on the positive side.

In the drawing, FLC (3) has two substrates (20),
(20''). Among them, a region (30) between the third electrode (23) and the fourth electrode (24) operates as a ferroelectric liquid crystal having a shutter function.

Further, as is clear from FIG. 4(D), the thickness of the laminate (50) having this non-linear element is 0.5 to 1.5μ and generally 1μ. And the upper surface is the fourth electrode (24
) are in close contact with the alignment films on the leads (6) and (7) connected to the leads (6) and (7). That is, both glass substrates have a structure in which they are integrated by a laminate. In addition, the thickness of this laminate is T
A thickness of 1 μm, which is much thinner than the 5-10 μm used in N liquid crystals, is sufficient. Conventionally, the opposing electrodes would short out in part due to the unevenness of the glass plate, but in the present invention, the upper glass plate (20°) has semi-hard bendability, and the laminate has a spacer. Also, since the gap between these spacers has one item every 400μ,
The thickness of the FLC filled between the electrodes can be set to a predetermined thickness, for example, 1μ±0.2μ.

Therefore, even if ±5V is applied, the electric field will be ±50V/
cm, and was able to provide a sufficient electric field to drive the FLC.

As a display panel, a reflective plate is then provided for the reflective type, a light source is provided on the back side for the transmissive type, and the peripheral circuits (8) and (9) shown in Figure 1 are arranged on the printed circuit board. The leads of the display element and each lead of the display element were connected in correspondence with each other.

In this way, it has become possible to pattern an active element type panel using only three masks.

"Effects" As described above, the present invention is a combination of a nonlinear element and an FLC. As a result, even in a 2×2 matrix configuration as shown, when the nonlinear element and (1,1) as shown in FIG. 1 are turned on, (1°2), (2
, 2) and (2, 1), the current value of Ov of the nonlinear element is sufficiently sensitive to the voltage applied at the same time through (2, 1), so it does not flow out. As a result, when (1, 1) is turned on, it becomes possible for the first time to simultaneously turn off other addresses using a nonlinear element, making it possible to completely prevent crosstalk. Furthermore, the manufacturing process was extremely simple in the structure shown in the example.

The aperture ratio is 86.7χ for the pattern shown in the drawing, which is 4% compared to 91.2χ for the passive method that does not use any elements.
．． We were able to limit the decrease to 5χ. This is well within the specification of not feeling bothersome if the aperture ratio is 80% or more, and should be satisfied.

Further, since the viewing angle uses l'iLc, there is not only one light shielding plate, and since ferroelectricity is used in particular, the viewing angle does not have the narrow viewing angle seen in TN.

Furthermore, since the laminate also serves as a spacer, there is no need to disperse spacers as seen in conventionally known displays using TN, making the process easier.

The embodiment of the invention showed a 2x2 matrix. However, the experiment was conducted by creating a matrix of 100xloo. It was also confirmed that characters, etc. could be displayed sufficiently. Considering the frequency characteristics, 8-bit parallel processing is applied, and 1920 (640 x 3) x
It is estimated that it is possible to create as many as 400 full-color displays.

In addition, in the present invention, the number of photomasks required for manufacturing a substrate to create a pixel consisting of a nonlinear element and a ferroelectric liquid crystal is two (in addition, the electrode surface area of the nonlinear element (predetermined voltage The current value when applying the current) does not change even if the center part of the rectangular electrode is shifted by up to ±200 μ vertically or by several degrees left and right, and has certain nonlinear characteristics.
It was possible to prevent variations in the electrical characteristics of active drive throughout the matrix.

In the examples of the present invention, MIMJ construction was mainly shown.

Further, M (conductor) in this MIM structure represents metals such as tantalum and chromium. However, other metals such as aluminum, titanium, and copper may also be used. Alternatively, a semiconductor doped with impurities at a sufficiently high concentration, ie, a P' or N' type non-single crystal semiconductor may be used.

On the other hand, as other non-linear elements of the present invention, one of the PIN structures or a tandem structure diode may be provided as a diode ring, or the PIN structure may be formed of Ba.
It is also possible to provide a ck-to-back junction. However, although the former has the disadvantage of requiring four photomasks, it has better frequency characteristics than the MIM structure, with 64 photomasks required.
It can be estimated that a large area of 0x400 is possible. On the other hand, the latter process uses NIP instead of the MIM stack of the present invention.
Only the -electrode-PIN structure is used, and exactly the same process can be used, and the process can be performed using two photomasks. However, it has the disadvantage that the reverse breakdown voltage is too large and tends to vary over a large area.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram of a liquid crystal display panel of the present invention. FIG. 2 is a longitudinal sectional view showing the manufacturing process of the MIM diode of the present invention. FIG. 3 shows the operating characteristics of the nonlinear element and ferroelectric liquid crystal of the MIM diode of the present invention. FIG. 4 shows a plan view and a longitudinal sectional view of the display panel of the present invention.

Claims (1)

[Claims] 1. In a solid-state display device in which pixels each having a plurality of active elements are arranged in a matrix on a substrate, each pixel is provided with a non-linear element and a ferroelectric liquid crystal connected in series. A liquid crystal display device characterized by: 2. A liquid crystal display device according to claim 1, wherein the nonlinear element having bistability has an M (conductor)-I (insulating film)-M (conductor) structure. 3. In claim 1, the nonlinear element is a PN
Or use a diode with PIN structure as Back-To-
A liquid crystal display device characterized in that it is electrically connected to a back. 4. In claim 1, the nonlinear element is a PN
Alternatively, a liquid crystal display device comprising one or more diodes having a PIN structure connected in a ring structure.