JPS6214813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal cell equipped with a plurality of liquid crystal layers arranged in a stacked manner, and more specifically to a so-called liquid crystal cell equipped with a plurality of liquid crystal layers as described above. This paper relates to an adhesive structure in a multilayer liquid crystal cell.

In recent years, as display functions have increased, multilayer liquid crystal cells having multiple liquid crystal layers have been put into practical use.

FIG. 1 shows a cross-sectional view of a liquid crystal cell having two liquid crystal layers, which is a typical conventional structure in which a plurality of liquid crystal layers are installed. 1 is an upper substrate, 2 is a middle substrate, 3 is a lower substrate, 4 is a segment side electrode, 5 is a common side electrode, and 8 is a liquid crystal layer. 6 indicates the adhesive layer between the upper substrate 1 and the middle substrate 2, that is, the first adhesive layer; 7 indicates the adhesive layer between the middle substrate 2 and the lower substrate 3, that is, the second adhesive layer; the first adhesive layer 6 The second adhesive layer 7 is made of the same type of adhesive.

The biggest problem from a practical standpoint with the conventional two-layer liquid crystal cell with the above structure is the manufacturing cost, which is extremely expensive compared to the manufacturing cost of a single-layer liquid crystal cell that has only one liquid crystal layer. Therefore, it cannot be put to practical use. That is, the two-layer liquid crystal cell is, needless to say, equivalent to two single-layer liquid crystal cells, and the manufacturing cost is simply twice that of the single-layer liquid crystal cell. However, in reality, various functional and cosmetic defects occur in liquid crystal cells during the manufacturing process at a much higher rate than in the case of single-layer liquid crystal cells, and in general, single-layer liquid crystal cells In many cases, the cost of manufacturing the cell is about three times as high.

Therefore, in the past, as a means to reduce manufacturing costs, the upper substrate 1 shown in FIG.
and the middle substrate 2 are bonded together via the first adhesive layer 6, and then the liquid crystal 8 is filled in the gap between both the substrates 1 and 2, and the first
The first layer liquid crystal cell is completed, the first layer liquid crystal cell is inspected functionally and visually, defective products are excluded, and only good first layer liquid crystal cells and the lower substrate 3 are inspected. Attempts have been made to manufacture a two-layer liquid crystal cell by adhering with a second adhesive layer 7 and filling the gap with liquid crystal 8 to form a second layer liquid crystal cell.

In this case, after the upper substrate 1, the middle substrate 2, and the lower substrate 3 are bonded in advance using the first adhesive layer 6 and the second adhesive layer, the liquid crystal 8 is placed in the gap between each substrate.
Compared to the manufacturing method in which the two-layer liquid crystal cell is filled with liquid crystal cells and then functionally and visually inspected after completion, the manufacturing cost is significantly reduced.However, the first major problem with the manufacturing method is Adhesive layer 6 and second
The adhesive used for the adhesive layer 7 is of the same type, and it is impossible to form a second layer liquid crystal cell after completing the first layer liquid crystal cell. .

That is, if, for example, low melting point sealing glass is used as the adhesive for the first adhesive layer 6 and the second adhesive layer 7, the first adhesive layer 6 may be formed even when the second adhesive layer 7 is formed. In the same way as when the sealing glass is used, the sealing glass must be heated to a high temperature, usually 400° C. or higher, to melt it. Therefore, it is already the first
The liquid crystal 8 filled in the liquid crystal cells of the second layer changes in quality due to the melting heating temperature of the sealing glass, and completely loses its liquid crystal properties.

On the other hand, when an epoxy resin adhesive is used as the other adhesive, the heating temperature required for bonding may be around 100° C. as in the case of the above-mentioned sealing glass, and the liquid crystal 8 does not change in quality. However, since the epoxy resin adhesive lacks the inherent chemical stability, after completing the first layer of liquid crystal cells, the back surface of the inner substrate 2, which was contaminated during the manufacturing process, was cleaned with an organic solvent, etc. It is extremely difficult to do so. Therefore, the back surface of the middle substrate 2 constituting the second layer liquid crystal cell comes into contact with the liquid crystal 8 while a certain amount of impurities generated during the manufacturing process of the first layer liquid crystal cell remains attached. Needless to say, this will have an extremely negative effect on the characteristics of the liquid crystal cell.

The object of the present invention is to significantly reduce manufacturing costs by improving the conventional adhesive structure having the above-mentioned drawbacks.

The present invention will be explained below along with examples.

Example Of the two adhesive layers shown in FIG. 1, the adhesive layer between the upper substrate 1 and the middle substrate 2, that is, the first adhesive layer 6, is made of low melting point sealing glass as a typical example of an inorganic adhesive. In this example, an epoxy resin adhesive is used as a typical example of an organic adhesive for the adhesive layer between the middle substrate 2 and the lower substrate 3, that is, the second adhesive layer 7.

In this manufacturing method, for the first layer liquid crystal cell, an upper substrate having a segment-side electrode 4 and a middle substrate 2 having a common-side electrode 5 on the upper surface are placed on the surfaces (not shown) in contact with the liquid crystal 8, respectively. After forming an alignment control film to align liquid crystal molecules in a predetermined direction, a PbO-B ₂ O ₃ -based low melting point sealing glass with a melting temperature of 450°C is applied to each substrate 1 and 2 by screen printing, etc. Apply by means. Thereafter, the sealing glass is heated to 450° C. and melted and fixed to the respective substrates 1 and 2. Then, overlap both substrates 1 and 2 while maintaining a predetermined positional relationship,
Temporarily attach using a jig etc. and heat to 450℃ again.
The sealing glass is remelted and both substrates 1 and 2 are melted.
Glue. Next, although not shown, the vicinity of the liquid crystal injection port, which is provided by cutting out a part of the first adhesive layer 6 made of the sealing glass in advance, is coated with Cr--
A so-called metallization process such as Pd is applied. Subsequently, liquid crystal 8 is filled into the gap between both substrates 1 and 2 through the injection port, and the metalized injection port is sealed with solder or the like.

After the first layer liquid crystal cell is completed in this manner, the first layer liquid crystal cell is inspected functionally and visually, and defective products are eliminated. Then, using only non-defective products, the middle substrate 2 is provided with the segment-side electrode 4 for the second layer liquid crystal cell that is contaminated during the manufacturing process.
Thoroughly clean the back side of the unit with an organic solvent, etc. Then, an alignment control film is formed on the back surface of the middle substrate 2 and on the surface of the lower substrate 3 provided with the common side electrode 5 in contact with the liquid crystal 8 in the same manner as in the first layer liquid crystal cell. Then, apply an epoxy resin adhesive to either the back surface of the middle substrate 2 or the lower substrate 3 by screen printing, etc., and overlap the substrates 2 and 3 while maintaining a predetermined positional relationship until the temperature reaches about 100°C. Heat is applied to bond both substrates 2 and 3 together. Next, the gap between the two substrates 2 and 3 is filled through a liquid crystal injection port provided by cutting out a part of the second adhesive layer 7 made of the epoxy resin adhesive. 2 adhesive layer 7
Seal using almost the same type of adhesive. Therefore, according to the above embodiment, by using a low melting point sealing glass having chemical and mechanical stability as the adhesive for the first layer liquid crystal cell, the conditions necessary for the second layer liquid crystal cell can be met. By establishing a clean state on the back side of the middle substrate 2 and using an epoxy adhesive as the adhesive for the second layer of liquid crystal cells, the heating temperature required when forming the second adhesive layer 7 can be kept at the same level as that of the liquid crystal 8. Since the deterioration temperature can be kept below the deterioration temperature, it is possible to eliminate functionally and visually defective products in the first layer of liquid crystal cells before forming the second layer of liquid crystal cells, making it possible to eliminate conventional adhesives. The manufacturing cost is much lower than that of a two-layer liquid crystal cell having this structure.

Example This is an example of a so-called three-layer liquid crystal cell having three liquid crystal layers, and the lower substrate 3 of the two-layer liquid crystal cell shown in FIG.
Another substrate is bonded to the back surface of the substrate via an adhesive layer (third adhesive layer).

This manufacturing method includes a first adhesive layer 6 and a second adhesive layer 7.
An inorganic adhesive is used as the adhesive in both cases, and the first layer liquid crystal cell and the second layer liquid crystal cell are completed simultaneously in the same manner as in the conventional manufacturing method. Then, using an organic adhesive as a third adhesive layer,
The lower substrate 3 constituting the liquid crystal cell of the third layer and the substrate installed on the back thereof are bonded together to form the liquid crystal cell of the third layer.

The same procedure may be applied to a liquid crystal cell having three or more liquid crystal layers. In each of the above embodiments, an organic adhesive was used for the bottom adhesive layer, but it may be used only for the top layer, or for two or more adhesive layers such as the top layer and the bottom layer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a two-layer liquid crystal cell among the multilayer liquid crystal cells. 1, 2, 3...Substrate, 6...First adhesive layer, 7...Second
Adhesive layer, 8...liquid crystal.

Claims (1)

[Claims] 1. At least three substrates arranged in a stacked manner,
are bonded to each other via an adhesive layer on the periphery of the substrate,
A liquid crystal cell comprising a liquid crystal layer held in a gap between each of the substrates, wherein each of the adhesive layers is made of two different types of adhesives. 2. A liquid crystal cell characterized in that the two types of adhesives described in claim 1 are an inorganic adhesive and an organic adhesive.