JPS6344622A - Display element - Google Patents

Abstract

PURPOSE:To prevent an upper and a lower electrode from being short-circuited at a light shield layer part by forming the light shield layer of the 1st light shield layer which contains a conductive material and the 2nd light shield material made of only a non-conductive material. CONSTITUTION:A part 8 where powder of a conductive pigment coagulates in the 1st light shield layer 3 increases the thickness of the light shield layer to form a projection structure. The 2nd light shield layer 4 is laminated on the 1st light shield layer 3. Therefore, even if an electrode 2B on a lower substrate contacts a light shield layer formed on an upper substrate at the time of the application of pressure to the substrates of a liquid crystal display element, the electrode that this electrode contacts is the 2nd light shield layer 4 which has no conductivity, so the upper and lower electrodes 2A and 2B are never short-circuited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a display element having a light shielding layer formed on its inner surface.

[Prior Art] An electro-optic display medium such as a liquid crystal is sandwiched between a pair of electrode-attached substrates such as a liquid crystal display element, and a voltage is applied between these electrodes to increase the optical power of the electro-optic display medium. In order to improve the display quality of display elements that perform display by changing the state, a light-shielding layer is added to the non-display area in order to reduce the transmitted light stitching in the non-display area and to improve the contrast between the display-on area and the background area. are beginning to form.

This C light layer is formed inside or outside the cell of the display element, but if it is outside the cell, the light shielding layer may become noticeable or the display may be obscured due to the heat of the substrate when viewed from an oblique direction. Since the light-shielding layer may appear shifted, a structure is desired in which a light-shielding layer is formed inside the cell to make the difference between the off-display area and the non-display area due to the light-shielding layer less noticeable, and to prevent this shift. There is.

Also, as a method for forming this light shielding layer.

Methods such as a dyeing method, a plating method, a vapor deposition method, and a printing method are known.

Although fine patterning is possible with this dyeing method, the process is complicated, including formation of the dyed layer, patterning of the dyed layer, dyeing, resist dyeing treatment, and removal of the patterning resist.
Although it is suitable for forming fine color films, etc., it has the drawbacks of being difficult to work with and high cost for forming such a light-shielding layer.

There are two types of plating methods: electrolytic plating and %17tt deplating. In either case, if the C light layer overlaps the electrode, an insulating layer is required between the plating layer and the electrode layer. becomes. Considering the purpose of blocking light, the light-shielding layer formed by this makeup has a fairly wide area and is highly conductive over its entire surface.For this reason, even if an insulating layer is formed, there will be pin holes in the insulating layer. If there were, a short circuit would occur between the electrodes, the plating layer, and the electrodes, which would be a big problem.

Furthermore, there are two methods for patterning the light-shielding layer using the plating method. One of them is the case where patterning is performed before forming the light-shielding layer, and in this case, it is necessary to form the plating electrode pattern into a predetermined pattern in advance.

The second case is when buttering is performed after forming the light-shielding layer, and a resist pattern must be applied using photolithography or printing. Therefore, no matter which method is used, the number of steps increases and workability is poor. However, the cost was also high.

Furthermore, the light-shielding layer formed by this method has a metallic feel, which is good when such a feeling is desired, but it is not preferable when a metallic feel is not desired, and the degree of freedom is low. Met.

The vapor deposition method is performed under vacuum, resulting in poor productivity and high cost, and results in a metallic appearance similar to the plating method.

On the other hand, the printing method uses colored ink and can perform patterning at the same time as forming the light-shielding layer, so productivity is high, costs are low, and it is easy to create a variety of looks. can be obtained.

Colored inks for the light-shielding layer include those using black pigments and those that have a black tone by mixing pigments of three colors, cyan, magenta, and yellow. When using a mixture of these three color pigments as this pigment, these pigments are not conductive, so if you use the fine powder of these three colors, this light-shielding layer will also become insulating, which will prevent short circuits, etc. Although this method does not cause any problems, it does have the problem that it is difficult to obtain high light-shielding properties.

For this reason, it has been proposed to use fine carbon powder, which has electrical conductivity but exhibits high light-shielding properties, as a pigment. Even when this carbon was used as a pigment, no problem occurred as long as the electrodes of the two substrates did not face each other in the light-shielding layer portion.

[Problems to be solved by the invention] However, the display becomes complicated, and many lead wires to the display electrodes are routed even in the non-display area, and many electrodes are oriented in the t4 direction in the light-shielding layer. Also, as display elements have become larger, the upper and lower substrates have become more flexible.

Short circuits are starting to occur between the upper and lower electrodes in the light-shielding layer.

Even if fine carbon powder is conventionally used as a pigment, this fine carbon powder is only mixed in as a fine powder, and it is almost impossible to imagine that this fine powder connects and conducts electricity like in conductive adhesives. In fact, no short circuit occurred between adjacent electrodes.

However, when we investigated a display element in which a short circuit occurred between the upper and lower electrodes, we found the following. First, this carbon fine powder is, for example, 5 to 10 μm, which is the cell gap of a liquid crystal cell.
It was found that although the particles were sufficiently finely divided compared to about m, they were not completely dispersed in the ink. Therefore, as shown in Fig. 2, when this ink is used to print on the substrate 1, parts where carbon fine powder has aggregated are formed as protrusions 2 containing a large amount of carbon, and the aggregated parts become conductive. If you use a substrate on which a light-shielding layer with such protrusions is formed to make a tatami mat, which has been found to be effective, 2! By applying slight pressure to the plate, the electrode on the other substrate and the electrode on the side where this light shielding layer is formed,
It was found that contact occurred at the protruding portion of the light shielding layer, causing a short circuit.

This is due to an increase in the number of electrodes being routed, an increase in the number of areas where the upper electrode faces the non-display area, and an increase in the size of the display panel, causing the substrate of the display element to be partially pushed due to external pressure. As a result, this phenomenon has become noticeable as the gap between the substrates becomes partially narrow, and a solution to this short circuit has been desired.

In order to prevent this, it was considered to reduce the thickness of the light-shielding layer, but the light-shielding properties deteriorated and this was not practical. Also, reduce the amount of carbon.

It was considered that the resulting decrease in light-shielding properties could be compensated for by adding other non-conductive pigments, but even if the number of protrusions was reduced, it could not be completely eliminated, and this did not solve the problem of short circuits. . Furthermore, it was considered to use only a non-tetraelectric ItrJ material, but the light-shielding layer would have to be considerably thicker, and it would be difficult to arrange it well between the narrow display element substrates. Means for Solving] The present invention has been made to solve these problems, and includes a method in which an electro-optical display medium is sandwiched between a pair of substrates with electrodes, and a light-shielding layer is formed on the inner surface of at least one of the substrates. However, in a display element in which the optical state of an electro-optic display medium is changed by applying a voltage between these electrodes.

The present invention proposes a display element characterized in that the light-shielding layer is composed of a first light-shielding layer containing a conductive substance and a second light-shielding layer consisting only of a non-conductive substance.

In the present invention, since two light-shielding layers are formed, it is possible to use highly light-shielding ink containing a conductive pigment such as carbon. This improves the performance and makes it difficult to cause short circuits between substrates.

The display element that can be used in the present invention has a pair of electrodes (an electro-optic display medium is held between the plates), a light-shielding layer is formed on the inner surface of at least one of the substrates, and a voltage is applied between these electrodes. Any display element may be used as long as it is formed by changing the optical state of an electro-optic display medium by applying a
Various known display elements such as electrophoretic display elements and PLZT display elements can be used.

The electrodes used in this display element are usually indium oxide.
Clearance of tin oxide (ITO), tin oxide, etc. 1! Although it is often used as a II electrode, it may also be used in conjunction with a low-resistance metal lead, or may be formed with a metallic reflective electrode or an electrode made of an opaque material.

The substrate on which the electrodes are formed can be made of glass, plastic, etc., and at least one of the substrates is a transparent substrate. In the case of a reflective display element, the back substrate may be made of an opaque material such as opaque glass, ceramics, or metal.

The light-shielding layer of the present invention consists of a first light-shielding layer containing a conductive substance and a second light-shielding layer consisting only of a non-conductive substance. This first light-shielding layer is a light-shielding layer containing a large amount of conductive pigment with high light-shielding properties. The second layer laminated on this
The light-shielding layer is a light-shielding layer made only of a non-conductive material, and by using these two light-shielding layers together, conductivity will not be exhibited in this cross-sectional direction. This eliminates the risk that the electrodes on the upper and lower substrates will be shortened by the light shielding layer even if the substrates on the upper and lower sides of the display element are pressurized.

These two light shielding layers may be formed on the inner surface of the same substrate, or may be formed on the inner surfaces of different substrates.

When these two light-shielding layers are formed on the inner surface of the same substrate, it is usually sufficient to form them on the front side, that is, the inner surface of the Tomei side of the substrate, but depending on the application, they may be formed on the inner surface of the back substrate. may be formed.

In addition, when formed on the inner surface of separate substrates, one front side, that is, ri9. It is preferable that a first light-shielding layer with high light-shielding properties be formed on the inner surface of the substrate on the Tomei side.

However, from the viewpoint of productivity including printing masks, etc., it is preferable to form these two light shielding layers on the inner surface of the same substrate.

Specifically, this first light-shielding layer may be formed of a colored pigment made by mixing fine powder of a pigment such as carbon, which is conductive but has a large light-shielding power, with an adhesive material, and may be formed by printing. Formation of the light-shielding layer and its patterning can be performed at the same time, resulting in high productivity.

The thickness of this first light-shielding layer may be set to a thickness that provides a desired light-shielding property, and is usually about 0.2 to 3 gm.

The second light-shielding layer is made of a colored ink containing fine powder of a pigment that is not conductive but has a lower light-shielding property than a conductive pigment, for example, by mixing pigments of three colors, cyan, magenta, and yellow, to create a black tone. Productivity is improved by forming this second light-shielding layer by a printing method, which may be formed using L'' color ink.

The thickness of this second light-shielding layer may be set to a thickness that provides desired insulation properties, and this may also normally be about 0.2 to 3 μm.

In addition, forming a light shielding layer by printing is a method with high productivity as mentioned above, and it is only necessary to print the first layer, dry blast, and then print the second layer. Depending on the properties of the colored ink, it may not be dried before printing the second layer, or it may be pre-dried only and then dried all at once after printing the second layer.

In addition, in order to change the appearance of this light-shielding layer, one or more other colored layers or interference films may be formed on the viewer's side, or a layer such as a liquid crystal alignment film may be formed on the surface in contact with the electro-optic display medium. may be formed.

Note that aggregation of the conductive material t1 in the first (7J) light-shielding layer does not necessarily occur. However, such colored ink may be stored to some extent and used, and from the point of view of workability. Even if it is possible to always select and use ink that does not agglomerate, it is extremely difficult to use an operation that eliminates agglomeration and results in poor workability.For this reason, when considering productivity, The structure of the present invention that does not cause problems even if aggregation occurs is extremely useful.

In addition, the aggregation of the conductive material in this first light-shielding layer is at most a few meters, and even in the case of only this light-shielding layer, there was a risk of short circuit between substrates, but if the same substrate Since the gap between adjacent electrodes on the top is usually wider than this, this adjacent 'i! Since there were almost no problems with short circuits between the electrodes, there is usually no problem even if the light shielding layer of part 1 is formed directly on the electrodes of this substrate. If the gap is approximately equal to or narrower than the diameter of the agglomerated face 4, an insulating layer of some kind may be formed on the electrode so that the first light-shielding layer does not come into direct contact with the electrode. Preferably, A has a structure in which the light-shielding layer has a three-layer structure in the body, and a pair of non-conductive second light-shielding layers are laminated on both sides of the first light-shielding layer that may cause conductive aggregation. Alternatively, a layer of an insulating material that does not have a light blocking property may be formed under the two light blocking layers.

A typical example of the display device of the present invention will be described below with reference to the drawings, taking a liquid crystal display element as an example.

FIG. 1 is a cross-sectional view of an example of a liquid crystal display element having a light shielding layer of the present invention, and FIG. 2 is a cross-sectional view of an example of a liquid crystal display element having a C light layer of the present invention.

In FIG. 1, LA and IB are transparent substrates such as glass, 2A and 2B are transparent electrodes such as ITO (indium oxide-tin oxide) formed on their inner surfaces, and 3 is a first
4 is a second light shielding layer, 5A and 5B are liquid crystal alignment films, 6 is a sole material of the substrate, and 7 is a liquid crystal sealed inside.

In this example, two light-shielding layers are formed in the non-display area, and are formed on the electrodes of the front substrate in the following order: the first light-shielding layer, and then the second light-shielding layer.

In the example shown in FIG. 2, the two light-shielding layers are formed on separate substrates, and the first light-shielding layer 3 is formed on the transparent substrate 1i11 of the transparent substrate IA on the front side to the pole 2A, and the first light-shielding layer 3 is formed on the transparent substrate IA on the front side. Toru lJ+
7! A second light-shielding layer 4 is formed on the transparent plate IB, and although it is formed on a separate substrate, these two C light-shielding layers form a two-layer light-shielding layer. layers are formed.

[Function] FIG. 3 is an enlarged cross-sectional view of the light-shielding layer portion of FIG. 1,
This shows the agglomeration of fine conductive pigment powder.

In this figure, in a portion 8 of the first light-shielding layer 3 where fine conductive pigment powder aggregates, the thickness of the light-shielding layer is thicker only in that portion, resulting in a protruding structure. In unreleased light 1!11, the second light shielding layer 4 is laminated on the first light shielding layer d3. For this reason.

Even if the substrate of the liquid crystal display element is pressurized and the electrode 2B on the lower substrate comes into contact with the light-shielding layer formed on the upper substrate, this electrode will only come into contact with a non-conductive second layer. Since the light-shielding layer 4 is 4, no short circuit occurs between the upper and lower electrodes 2^ and 2B.

In this example, only the basic structure of the liquid crystal display element was explained, but in addition to this, it is also possible to use color filters, stack active elements for active matrix, have two liquid crystal layers, and use electrodes. The structure of the liquid crystal display element may be well-known, such as having two layers with an insulating layer in between, or stacking polarizing films, reflectors, light sources, light guides, various filters, etc., and is not limited to nematic liquid crystal, but also cholesteric liquid crystal. It can also be applied to liquid crystal display elements using smectic liquid crystals, smectic liquid crystals, etc.

In this explanation, the liquid crystal display element most suitable for the present invention has been taken up as a representative example, but the present invention is not limited thereto and can be applied to other display elements.

[Example] Example 1 With the configuration shown in Figure 1, a colored ink mixed with fine carbon powder as a pigment was printed and dried as a light-shielding layer of 51 on the non-display part of a glass substrate with ITO as the front side substrate. The second light-shielding layer was printed with sepia ink (a mixture of non-conductive pigments of three colors cyan, magenta, and yellow) and dried to a thickness of about 1.2 pm. 7Qnm polyimide is used as the liquid crystal alignment film.
I used the one that I applied and rubbed.

The light-shielding degree of this first light-shielding layer is about 95%, the light-shielding degree of the second light-shielding layer is about 76%, and 2)'! When used as a light shielding layer of X, the light transmittance was about 1.25%.

As the back side substrate, the same glass substrate with ITO was coated with 70 nm of polyimide as a liquid crystal alignment film and rubbed.

The periphery of these two substrates was sealed with a sealing material so that the cell gap in the display section was 9 μLm.

A liquid crystal cell with a cell gap of 9 Bm was manufactured by sealing liquid crystal inside.

As a comparative example, a liquid crystal display element in which only the first light-shielding layer was formed with a thickness of about 1.2 lumen was also manufactured.

When we compared the incidence of short circuits between the upper and lower substrates of this cell, we found that in the uninvented embodiment, the occurrence of short circuits was only 0.5.
%, whereas in the comparative example it reached about 5%. In this manner, the display element of the present invention could easily provide a display element that is unlikely to cause a short circuit between the upper and lower substrates even when the upper and lower substrates are pressurized.

Example 2 A first light-shielding layer of about 1.2 meters long was applied to the front substrate, followed by an alignment film of 70 nm thick, and a second light-shielding layer of about 1.2 meters long was applied to the back side substrate. Subsequently, a cell was formed in the same manner as in Example 1 except that an alignment film with a thickness of 70 nm was used. Even when the substrate was pressurized in this cell as in Example 1, almost no short circuit occurred.

Example 3 In Example 1, the width between the electrode lines was set to 30 μm or more, so no short circuit occurred between adjacent electrodes on the same substrate, but when the distance between the lines was set to about 10 gm,
Short circuits between adjacent electrodes could occur. For this reason, before forming the first light-shielding layer in Example 1, an insulating layer of silicon oxide and titanium oxide with a thickness of 0.1 μm was formed. A cell was formed in the same manner as in Example 1.

As a result, even when the distance between the lines was 10 μm, no short circuit occurred between adjacent electrodes.

[Effects of the Invention] In the present invention, since two light-shielding layers are formed as described above, it is possible to use ink with high light-shielding properties mixed on a conductive pigment such as carbon, and the display area and The contrast of the non-display area is improved, and the defect 8 due to the substrate width is less likely to occur.

In addition, it is not necessary to control the ink to prevent agglomeration of highly light-shielding ink containing an arsenic-conducting pigment such as carbon, or to perform an operation to eliminate agglomeration, and it is easy to use.

Furthermore, the printing method allows layer formation and patterning to be performed simultaneously, resulting in good productivity, and also allows for easy control of the transmittance, ie, the thickness of the layer, providing a high degree of freedom.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example in which the present invention is applied to a liquid crystal display element. FIG. 2 is a sectional view of another example in which the present invention is applied to a liquid crystal display element. FIG. 3 is an enlarged sectional view of the light-shielding layer portion of FIG. JS1. Transparent substrate: IA, IB Transparent electrode: 2A, 2B First light shielding layer = 3 Second light shielding layer, 4 Liquid crystal alignment jII4 ・5A, 5B Nur material
°6 Liquid crystal ;7 Agglomerated part 28 Gi10 Leaf 20 Rhinoceros 3 ward

Claims (8)

[Claims] (1) An electro-optical display medium is sandwiched between a pair of substrates with electrodes, and a light-shielding layer is formed on the inner surface of at least one of the substrates,
In a display element in which the optical state of an electro-optical display medium is changed by applying a voltage between these electrodes, the light-shielding layer consists of only a first light-shielding layer containing a conductive substance and a non-conductive substance. 1. A display element comprising: a second light-shielding layer; (2) The display element according to claim 1, wherein the conductive substance of the first light-shielding layer is carbon. (3) Claim 1 in which the light-shielding layer is formed by a printing method
Display element described in section. (4) The display element according to claim 1, wherein the first light-shielding layer and the second light-shielding layer are laminated. (5) The display element according to claim 4, wherein the first light-shielding layer is formed on the electrode side, and the second light-shielding layer is formed on the electro-optic display medium side. (6) The display element according to claim 1, wherein the first light-shielding layer and the second light-shielding layer are formed on electrodes of different substrates. (7) The display element according to any one of claims 1 to 6, wherein the electro-optical display medium is a liquid crystal. (8) The display element according to claim 7, wherein an alignment film is formed on the light shielding layer.