JPS62265626A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve visibility by forming plural divided common electrodes on the whole surface of a substrate so as to be close to each other and forming a light shielding layer based upon a metallic thin film on a common electrode in a non-display part. CONSTITUTION:The common electrodes 2A based upon plural divided transparent electrodes are formed on a substrate 1A and plural segment electrodes 2B based upon similar electrodes are formed on a substrate 1B. These substrates 1A, 1B are arranged so respective electrodes are opposed to each other, the periphery of the substrates 1A, 1B are sealed by a sealing material 4 and a liquid crystal layer 5 is injected into a space between the substrates 1A, 1B. In the liquid crystal display element constituted as mentioned above, the electrodes 2A on the substrate 1A are arranged close to each other within a range where adjacent electrodes 2A are not mutually shorted and then the light shielding layer based upon the metallic thin film is formed on the electrodes 2A in the non-display part formed on almost the whole surface of the substrate 1A. Consequently, light leakage from the non-display part can be removed and the contrast of a lighting part on a virtual display part can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element with improved visibility.

[Conventional technology] Liquid crystal display elements have been used for various purposes,
Its structure includes a first substrate having a common electrode,
A structure in which a second substrate having segment electrodes is arranged so that the electrode surfaces face each other, the periphery is sealed with a sealing material, and liquid crystal is sealed between them is often used. Particularly often used is a liquid crystal display device in which a pair of polarizing films are placed on both sides of the display element, and when no voltage is applied, the liquid crystal takes on a 90° twisted structure, and when a voltage is applied, the liquid crystal takes on a 4-shape structure. Twisted Nematch (
There is a TN) type liquid crystal display element.

When such liquid crystal display elements are used as a reflective type, they usually have a pair of polarizing films arranged so that their polarization axes are perpendicular to each other, producing a positive display in which only the part to which voltage is applied appears black. There is. In this reflective positive display, the background is a little dark, but it is not particularly difficult to see.

[Problems to be solved by the invention] In contrast, in recent years, there has been a demand for performance that can be used even in dark rooms and has good visibility, mainly in audio and home appliances, and it has become necessary to use reflective type liquid crystal display elements. There is a growing demand for the use of both the transparent type and the use of the transparent type.

In the case of this transmissive type, the light from the backlight is directly f
Because it is easier to see in negative type, a pair of polarizing films are usually arranged so that their polarization axes are parallel, and the background is dark and the light is turned on when a voltage is applied. Only certain parts are made to appear bright.

However, in this transmissive negative type display, the background part is darkened, but when viewed in a dark room, although the background part inside the liquid crystal display element is darkened, a certain amount of light is transmitted through it. Therefore, no matter how much voltage is applied and only the illuminated parts appear bright, the visual contrast is reduced and visibility is reduced.

For this reason, it has been considered to form a film of a light-shielding substance on the outside of the liquid crystal display element to prevent light from leaking from the non-display area, but due to problems with alignment viscosity, Because it is laminated, there is a problem of misalignment with the electrodes when viewed from an oblique direction, making it unsuitable for liquid crystal display elements with fine patterns.In addition, the side of the substrate of the liquid crystal display element where the electrodes are formed It has also been proposed to form a thin-film light-shielding layer between the electrode and the substrate on the plane of When used, it is necessary to form an insulating film on top of the light-shielding layer, and an electrode layer on top of that, which tends to cause problems such as difficulty in obtaining a thin, perfect insulating film, and reduced electrode reliability. was there. Furthermore, when using an insulating light-shielding layer made of colored ink or the like, there are problems such as it is difficult to make the metal thin, and the electrodes formed thereon tend to peel off, reducing reliability. .

On the contrary, it has also been proposed to form a light-shielding layer on a patterned electrode;
Even if a layer is formed, there is a risk of a short circuit, and colored ink, etc., will be thick, so it may affect the shape of the liquid crystal injection, or it may have a negative effect on the creation of the alignment film formed on the display area. There was a problem that sufficient light-shielding properties could not be obtained.

In addition, in the case of a liquid crystal display element of this type that forms a metal light-shielding layer, if there is only one common electrode, it is sufficient to form a common electrode on the entire surface, and there is no problem; Forming a layer of electrolytic nickel plating or vapor deposition of chromium II! I was able to form 2.

However, such liquid crystal display elements with only one common electrode can only be static driven or active matrix type, and non-active matrix types have a large number of terminals and require a wide operating temperature range. It is difficult to use it only for special purposes, and it is usually driven dynamically by forming a plurality of common electrodes. In particular, in a matrix type liquid crystal display element, it is necessary to use a large number of strip-shaped common electrodes and a large number of strip-shaped segment electrodes that are perpendicular to the common electrodes.

In such a liquid crystal display element using common electrodes with the number 8, it is not possible to easily form a light-shielding layer on the entire surface as described above, and light leaks from between the common electrodes. Sometimes it leaked.

[Means for Solving the Problems] The present invention has been made to solve these problems, and is divided into several parts: 1. The first with a +1 common electrode
a substrate and a plurality of segments 114. In the liquid crystal display element in which the electrodes are arranged so that the electrode surfaces face each other, and the periphery is sealed with a sealing material, 11) 1 contains one liquid crystal, 801. The common electrode of the board is placed close to the adjacent common electrode 1 (the first) 1 (the first one is arranged close to each other within the range that the peak phase pressure does not short-circuit), and the common electrode of the non-display part is formed on the common electrode of the non-display part. (2) This is a liquid crystal display element having a 4ν characteristic in which a light-shielding layer made of a thin film is formed.

The liquid crystal display element of the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of a basic example of the liquid crystal display element of the present invention.

In Figure 1, IA and IB are glass, plastic, etc. substrates, 2A is indium oxide-tin oxide (ITO),
The common electrode is made of a transparent electrode such as tin oxide, 2B is a segment electrode made of a similar electrode, 3 is a light shielding layer made of a metal thin film, 4 is a sealing material for peripheral sealing, and 5 is an enclosed liquid crystal layer. In this case, the common electrode is divided into two.

In Fig. 1, there are segment electrodes facing the common electrode, and a light-shielding layer of a metal thin film is formed on the common electrode corresponding to the area required for display, and an extra layer is removed from the non-display area. Light is prevented from leaking through.

In addition, in the area where two common electrodes are adjacent to each other, the distance W between both common electrodes is set to 80 gm or less in order to reduce light leakage and make it difficult to recognize the gap. It is sufficient if it is set to lpm or more. However, this narrower one, except for the difficulty of manufacturing,
If it is set to pm or more, the insulation resistance between the electrodes can be made to be IOKΩ or more, so it may be set to 0.01 gm or more. In particular, W.
From the viewpoint of appearance, it is preferable to set the amount to about 1 to 30 grn. However, due to the shape of the pattern, it may not be possible to set the spacing between all the common quasi-poles within this range, and in this case, the spacing may be larger than this spacing within a range that does not cause any visual problems.

As the light shielding layer made of the thin metal layer of the present invention, a thin layer of nickel, chromium, copper, gold, aluminum, etc. can be used, and it can be formed into a desired shape by a known method such as electroless plating, electrolytic plating, or vapor deposition. It is fine if it is done.

Among these forming methods, the Menki method, which can selectively form a metal thin film on the common electrodes, is preferred because short circuits between the common electrodes can be easily prevented.

Among these, the electroless plating method is easy to apply, and particularly when a tin oxide-indium oxide based electrode is used for the common electrode, nickel can be easily selectively electrolessly plated, so it is preferable.

The substrate on which the common electrode on which this light shielding layer is formed is a
It is preferable to arrange it on the observer's side, so that light leakage within the liquid crystal layer will not be a problem and the electrodes on the front side of the non-display area will not be visible even when viewed with a single reflection type, resulting in a good view.

The present invention can be used to display the species 1/ from a 1-shaped numeric display to a tosomatrix-type display. In particular, in a donmatrix type display, a large number of band-shaped common electrodes and a large number of band-shaped segment electrodes perpendicular to the common electrodes are used. It is easy to design the interval between the electrode and the common electrode to be constant, and it is easy to apply the present invention.

In addition, in a Japanese character-shaped numeric display, etc., the area of the non-display part is larger than that of the display part, so the effect of providing a light-shielding layer is large, and the apparent contrast is greatly improved.

In addition, the metal thin film of the present invention does not need to be formed on the entire non-display part of the common electrode, and the light-shielding layer of the metal thin film may not be formed on some non-display parts, for example. In the case of the above-mentioned dot matrix type display, even if a metal E1 film is formed on all of the common electrodes corresponding to the non-display areas between segment electrodes, the visual effect is often small; It may be formed in a frame shape outside the dot matrix display section. In such a case, in order to improve visual visibility, a common electrode unrelated to one display may be formed, or a segment electrode may be formed in a frame shape. A gold & iQ film may also be formed thereon.

This metal? The thickness of one film may be appropriately set based on the light transmittance, but it is usually about 500 to 5000 people.

In particular, when forming electroless nickel plating on a tin oxide-indium oxide (ITO) based transparent electrode, the thickness of the transparent electrode should be 300 to 1500, and the thickness of electroless nickel plating should be 1000 to 2000. By arranging the substrate on the common electrode side toward the viewer, a glossy black light-shielding layer with good appearance can be obtained, which is preferable.
If the place of use is not limited to a dark condition, but is also a place where it can be used to some extent, a sense of luxury will be created and the appearance will be greatly improved.

In the liquid crystal display element of the present invention, in addition to this basic structure, an alignment film is formed on the electrode and the gold f1 thin film, a color filter is formed on or below the electrode and the metal FM film, and a color filter is formed on the electrode and the metal FM film below. A layer may be formed to prevent elution of alkali from the substrate.

FIG. 2 is a cross-sectional view of a preferred example of the present invention, I
IA, 11B are glass substrates, 18A, 18B
is an undercoat layer made of inorganic oxides such as silica, alumina, and titania to prevent alkali elution.

12A is a common electrode, 12B is a segment electrode, 13 is a light shielding layer made of a metal thin film, 17 is an insulating overcoat layer made of inorganic oxide such as silica, alumina, titania, etc.
18A and 18B are overcoat layers for alignment made of resin such as polyimide or polyamide, 14 is a sealing material for peripheral sealing, and 15 is an encapsulated liquid crystal layer.

In this example, when a spacer material is placed between the electrodes to maintain a constant substrate gap, the conductive material may come into contact between the electrodes due to movement of the spacer material or foreign matter mixed between the substrates, causing the common electrode to contact the spacer material between the electrodes. In order to prevent short circuits with the segment electrodes, an insulating overcoat layer 17 made of an inorganic oxide such as silica, alumina, or titania is formed under one of the resin alignment overcoat layers. Of course, this insulating overcoat layer is
May be formed under both orientation overcoat layers.
This insulating overcoat layer is less likely to be damaged than the resin orientation overcoat layer, and there is a low possibility that the insulation will be damaged by foreign matter that has entered the cell.

Also,! It is also possible to provide only one overcoat layer for orientation made of IIl resin or inorganic oxide, and the orientation may be achieved by a rubbing method or by a method such as oblique vapor deposition.

This overcoat for orientation uses polyimide, and stable orientation can be obtained by aligning by rubbing.

FIG. 3 is a plan view showing an example of a common electrode pattern used in the present invention, and shows an example in which the square-shaped common electrode is divided into two.

In this figure, a one-dot line indicates a pattern of one display. When the area of the display area is smaller than the area of the non-display area as in this example, the contrast of the display area can be increased by preventing light from passing through the non-display area according to the present invention. improves.

Although the common electrodes are not completely parallel, they are almost parallel strips, and the interval between the two common electrodes can be easily kept narrow and constant as in the case of the dot matrix described above.

In the case of such a pattern, the area of the display area is much smaller than the area of the non-display area, so the structure of the present invention significantly improves the apparent contrast by preventing light from passing through the non-display area. do.

When the liquid crystal display element of the present invention is applied to a TN type liquid crystal display element, a pair of polarizing films are arranged on both sides of the liquid crystal display element as described above so that the polarization axes are parallel to each other, and in the case of a dual-reflection/transmission type, a pair of polarizing films are arranged on both sides of the liquid crystal display element as described above. It may be used by placing a semi-transmissive reflector at the top and placing a light source after that. Of course, it is also possible to place a scattering plate or light guide plate in front of this light source, or to install a filter to correct the color temperature of the light source, or to guide outside light instead of the light source. You may also arrange other members.

[Function] In the present invention, by forming a light shielding layer made of a metal thin film on the common electrode of the non-display area, light leakage from the non-display area is eliminated, and the apparent contrast of the lit part of the display area is improved.

This is because although light passes through the non-lit parts of the display area as before, light does not pass through other non-display parts of the background area, resulting in less light passing through the background area. The apparent contrast of the lighting section of the display section is improved.

[Example] Example 1 ITO was formed to a thickness of 1000 nm on a glass substrate having an underneat layer of silica with the structure shown in Fig. 2 and the pattern shown in Fig. 3. Then, the electrodes were patterned using a photoetching method, and the spacing between the electrodes was set to 15 pm.
A common electrode substrate and a segment electrode substrate were manufactured.

Of the substrates patterned in this way.

The common electrode substrate was degreased with a 10% aqueous sodium hydroxide solution, washed with water, immersed in a solution containing a diluted adhesion promoter, rinsed with water, immersed again in a solution containing a diluted adhesion promoter, washed with water, and heated. It was immersed in a nickel electroless coating bath for 1 minute to obtain a plating thickness of 2,000 mm. As a result, a nickel plating layer was formed in the same pattern on the common electrode pattern.Next, a photoresist was applied, and the nickel plating on the display portion was etched by a photoetching method. This photoresist film was peeled off to produce a common electrode substrate on which a light shielding layer was formed.

On the common electrode substrate on which the light-shielding layer was formed by nickel plating, an alignment overcoat layer of 1,000 polyimide was formed and rubbed to form an alignment film.

On the other hand, an insulating overcoat layer of 2000 silica was formed on the segment electrode substrate produced as described above, and an alignment overcoat layer of 1000 polyimide was further formed and rubbed to form an alignment film.

The common electrode substrate and the segment electrode substrate on which the alignment film has been formed in this way are placed facing each other at a distance of 7 gm so that the '1 shield faces face each other, and the periphery is sealed with a sealing material to form a cell. Nematic liquid crystal was injected into the cell, the injection port was sealed, and a liquid crystal display element was manufactured.

A pair of polarizing films were placed on both sides of this liquid crystal display element so that the polarization axes were parallel to each other, and a light a: ( was placed on the back side to form a transmission type TN type liquid crystal display element.

This TN type liquid crystal display element had a light-shielding layer that was easy to manufacture, and the apparent contrast was about three times better than that of a liquid crystal display element without a light-shielding layer.

Example 2 The pattern was a 200 x 200 dot matrix strip electrode, a nickel-plated light-shielding layer electrode was formed on the outside of the common electrode at both ends, and the nickel-plated part was used as the dot display part of the 200 common electrodes. A TN-type liquid crystal display element was manufactured in the same manner as in Example 1 except that nickel plating was formed on the outside of the two outer common electrodes, and as a result, nickel plating was formed in the frame shape.

This TN type liquid crystal display element also had a light-shielding layer that was easy to manufacture, and the apparent contrast was improved compared to a liquid crystal display element without a light-shielding layer.

[Effects of the Invention] In the present invention, a total bending Q I+
! By forming the light-shielding layer according to No. 2, light leakage from the non-display area is eliminated, and the apparent contrast of the lit portion of the display area is improved.

This metal thin film does not need to be thick like colored ink, is thin and has a high degree of light shielding.

In addition, by placing the common electrode substrate on the viewer's side, nickel plating on ITO produces a glossy black color, which makes it look good when used in places where it is used to some extent. .

Further, according to the electroless plating method, since a metal thin film is formed only on the portion of the underlying electrode, there is no problem even if there is a fine pattern, and the electrodes can be arranged at narrow intervals, which is preferable.

The present invention can be applied in various ways in the future without detracting from the effects of the present invention.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a basic example of the present invention. FIG. 2 is a sectional view of a preferred embodiment of the present invention. FIG. 3 is a plan view of an example of a common electrode according to an example of the present invention.

Claims (10)

[Claims] (1) A first substrate having a common electrode divided into a plurality of parts and a second substrate having a plurality of segment electrodes are arranged so that the electrode surfaces face each other, and the periphery is sealed with a sealing material, and the In a liquid crystal display element in which a liquid crystal is sealed in a liquid crystal display element, common electrodes of a first substrate are arranged close to each other within a range where adjacent common electrodes do not short-circuit each other, and are formed on almost the entire surface of the first substrate. A liquid crystal display element characterized in that a light shielding layer made of a metal thin film is formed on a common electrode. (2) The liquid crystal display element according to claim 1, wherein the metal thin film is formed by plating. (3) The liquid crystal display element according to claim 2, wherein the metal thin film is formed by electroless plating. (4) The liquid crystal display element according to claim 3, wherein the common electrode is a tin oxide-indium oxide based electrode, and the metal thin film formed thereon is formed by electroless nickel plating. (5) The liquid crystal display element according to any one of claims 1 to 4, wherein the distance between adjacent common electrodes is 1 to 80 μm. (6) A plurality of common electrodes are formed in a substantially parallel band shape,
6. The liquid crystal display element according to claim 5, wherein the plurality of segment electrodes are formed in a strip shape substantially parallel to the common electrode in a direction substantially perpendicular to the common electrode to display a dot matrix display. (7) A plurality of common electrodes are formed in substantially parallel strips,
6. The liquid crystal display element according to claim 5, wherein the plurality of segment electrodes are formed in a direction substantially perpendicular to the common electrode to produce a sun-shaped display. (8) The liquid crystal display element according to any one of claims 1 to 4, wherein an alignment film is formed on the electrode and the metal thin film. (9) The liquid crystal display element according to claim 8, wherein the alignment film is a two-layer film consisting of an insulating overcoat layer made of an inorganic oxide and an overcoat layer for the alignment film made of a resin film. (10) The liquid crystal display element according to claim 9, wherein the resin film is a polyimide film.