JPS6353527B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes two glass plates spaced apart from each other via a frame having a space containing a liquid crystal, and these plates have control electrodes therein; and an orientation layer of active ingredient molecules.

The aim of the invention is to overcome the problems in the mass production of display cells with liquid crystals.

The first type of problem is labor saving and improving product life. This type of problem has already been proposed in the simultaneous mass production of a group of cells (Swiss Patent No. 11387/78).

Although the problem that the present invention seeks to solve is of the second type, it is appropriate to point out that the manufacturing method of the present invention is also suitable for mass production. In mass production, the various layers containing the cells are formed attached to a glass plate that is larger than the dimensions of the plate of each cell, and then cutting is performed to separate each cell.

Defects that have been frequently observed in passive electro-optic display cells and which the present invention seeks to eliminate or alleviate are as follows.

(a) Formation of micro-areas in the bottom band that causes a decrease in contrast and formation of micro-areas in the display band (segment) that causes the so-called "back-wobble" phenomenon that affects the uniformity of the effective segment.

(b) Increase in display control current over time.

(c) Rapid collapse of orientation after long-term use or use at high temperatures.

These three disadvantages are caused by the dissolution of the alignment layer due to the solvent action of the liquid crystal, especially gradual dissolution when the alignment layer is made of organic matter, and the penetration of impurities into the poorly protected liquid crystal. These impurities originate from the cell containment frame, the glass plate, and the plate holding layer, and migrate by diffusion.

Other drawbacks often observed are weak bonding between the display cell and the resin frame and increased current consumption in humid atmospheres. This is because water molecules easily diffuse into the cell.

A voltage drop across the insulating layer that properly covers the electrode network has also been observed, and this voltage drop has a negative impact on the electro-optical behavior of the cell.

Finally, due to the slightly excessive rocking angle for the alignment layer, the formation of a "bulk" at the periphery of the active display segment is noted.

According to the invention, these disadvantages are eliminated or reduced.

Next, the present invention will be explained in detail with reference to the accompanying drawings.

The cell shown is made of polymeric material, e.g. phenol.
A waterproof or sealed frame 2 made of formaldehyde resin encompasses two glass plates 1 facing each other with a distance between them.

The faces of the two opposing glass plates 1 are completely coated with a protective layer 3 of approximately 800 angstroms thick, made of silicon dioxide, for example, which protects, in particular, the ions emanating from the plates 1 into the cells. It has the effect of preventing diffusion.

An electrode, designated 4 and made of, for example, indium monoxide and approximately 400 angstroms thick, is pressed into contact with each of the protective layers 3.

The electrodes themselves are covered with a bonding layer 5 of transparent organic material, such as organosilane, organoaluminate or organosilicon.

The layers 5 themselves are each coated with a molecular alignment layer 6 for the liquid crystal, which is sealed between the plates 1 inside the frame 2.

The alignment layer 6 is made of a polymeric material, for example polyimide. The thickness of the pairs of layers 5 and 6 is on the order of about 50-500 Angstroms.

The illustrated cell is manufactured as follows using glass plates with dimensions larger than those of the completed cell.

First, a glass plate is coated with a protective layer 3 of silicon dioxide by spray painting or vacuum deposition.

The entire surface of these plates is then coated with a thin transparent conductive layer by vapor deposition or spray painting. This conductive thin layer is partially removed using photochemical methods, and
This creates counter electrodes and a network of electrical connection paths on each plate. It is worth noting that if the cell is not dual controlled, the counter electrode can cover the entire plate without a break.

Each plate has a bonding layer 5 ensuring an interface between the alignment layer 6 and the substrate. Organosilane, organoaluminate or organosilicon is applied in solution to form the bonding layer 5. The solvent is then evaporated by drying.

A polyimide precursor solution is then applied in the same manner onto each plate to form an alignment layer 6.

The two alignment layers 6 are then rubbed unidirectionally with a soft fabric to ensure the desired alignment of the liquid crystal molecules. When the plates are assembled to form a cell, the two directions of friction are perpendicular to each other.

A frame 2 consisting of a resin precursor material diluted with a solvent is then applied to one of the plates by silk-screening. Its thickness is approximately 15 microns after drying.

Next, the two plates are assembled and the frame 2 is interposed between the plates. The entire body was heated at approximately 100 to 150°C to soften the resin precursor material that makes up the frame 2, and while the material was softened, both plates were heated to a desired spacing between the two plates. Apply external pressure. At this time, for example, a spherical spacing member that does not soften due to heat and can limit the spacing between the plates may be present in the frame 2 material. In practice, the spacing is about 8 microns.

When the resin precursor is a phenol-formaldehyde resin prepolymer, the first temperature for softening the resin precursor constituting the frame 2 should not have any effect on the alignment layer 6 made of a polyimide precursor. It should be noted that

After the fitting operation is completed, the cell is heated to a second temperature, e.g. about 250 DEG C., for an extended period of time, e.g. 1 hour.

As a result, the resin precursor, that is, the prepolymer constituting the frame 2, and the alignment layer 6 made of the polyimide precursor are simultaneously polymerized. Care is taken in the selection so that the polymerization temperatures of the two precursor materials are not too different.

This heating operation is carried out between the containment frame 2 and the orientation layer 6.
It is extremely important to cause copolymerization between the two, and the chemical bonds between the members created by the copolymerization protect the liquid crystal 7 from any contamination and any external influences.

Next, the passage created when attaching the frame 2 by the silk screen method is similarly closed using a known method to confine the crystal 7 inside.

One of the glass plates is pre-configured to be significantly larger than the other in order to enable the cell to be energized. This makes it easier for the electrode to approach from the outside. Since the bonding layer and the alignment layer are placed over the entire surface of the glass covering the electrodes, it is necessary to later remove these two layers by cutting.

Since the material of the bonding layer 5 can be selected more freely than the material of the alignment layer 6, this selection allows the bonding layer 5 and the alignment layer 6 to be
The chemical bond at the contact area can be strengthened.

Thus, on the one hand, between the bonding layer 5 and the alignment layer 6,
On the other hand, a perfect chemical bond between bonding layer 5 and protective layer 3 is achieved.

It should be noted that the chemical bond between the frame 2 and the alignment layer 6 is not destroyed even when the glass plate is cut to separate a large number of cells in series in mass production.

Good bonding is important to ensure that the protection of the liquid crystal is maintained when the cell is operated under harsh weather conditions, especially high humidity. The effect of moisture on the liquid crystal leads to an increased consumption of the control current of the cell. Furthermore, this can cause the collapse of liquid crystal molecules.

Since the sum of the positive and negative puzzles for cell control always remains positive or negative, it is preferable to improve the superposition of the alignment layer and the bonding layer to ensure protection of the liquid crystal from direct current. Such protection against direct current is achieved when layers 5 and 6 together form a volume. The smaller the impedance of this three-dimensional structure, the more advantageous it is, and thus voltage drop can be prevented.

According to the present invention, since the frame frame 2 is made of resin, there is no need for a high-temperature heating process for the cell, which causes diffusion of ions emitted from the glass plate and impurities emitted from the frame material, compared to a conventional frame made of glass frit. This has the advantage that it also retains the advantages of glass frit over resinous materials, which ensure maximum waterproofness and reliability.

The use of a protective layer 3 to avoid the diffusion of ions that would disturb the molecular alignment of liquid crystals is known, but in the present invention, a glass plate is formed directly above the electrodes on the glass plate that is the substrate of the protective layer. It should be noted that it is located on the substrate.

Conventional protective layers placed on the electrode surface have the disadvantage of creating an impedance on the glass plate, causing a voltage drop and flattening the contrast/voltage curve. The curve requires particularly steep slope areas in the case of multiplex control.

[Brief explanation of the drawing]

The accompanying drawings are explanatory views showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Frame, 3... Protective layer, 4... Electrode, 5... Bonding layer, 6... Alignment layer, 6... Liquid crystal.

Claims (1)

[Claims] 1. A method for manufacturing a passive electro-optic display cell, comprising:
The manufacturing method includes a step of applying a coating made of a conductive material to each of two glass plates, selectively removing a part of the conductive coating on at least one of the glass plates by a photochemical method to form a cell. forming a control electrode and simultaneously forming an electrical connection path thereto; coating each plate with a film made of a polymerizable first material to form an alignment layer;
rubbing each of the coatings made of the first polymerizable material in a certain direction so that the directions of friction are perpendicular to each other when the plate is assembled; A step of depositing on one side of the frame and simultaneously forming a passage in this frame, a step of assembling the plate with the frame in between,
heating the assembly to a first temperature to soften the frame material, adjusting the spacing between the plates with the softened frame, and polymerizing the frame material to create an impermeable case for the cells. , filling the interior of the case with liquid crystal through the frame passageway, and impermeably sealing the passageway, comprising the steps of: prior to the polymerization of the first material, the deposition of the frame on one of the glass plates is performed after the friction operation and before the polymerization of the polymerizable first material, and the spacing between the plates is adjusted. A method of manufacturing comprising subsequently heating the assembly to a second temperature higher than the first temperature to copolymerize the first polymerizable material and the second polymerizable material with each other. 2. The manufacturing method according to claim 1, wherein the polymerizable first material is a polyimide precursor.