JPH01295223A - Color liquid crystal display element - Google Patents

Abstract

PURPOSE:To hardly generate disconnection and to obtain the element having high durability by laminating two over coating layers having the coefft. of thermal expansion intermediate of the coeffts. of thermal expansion of color filters having a large coefft. of thermal expansion and electrodes or substrate having a small cofft. of thermal expansion between said color filters and electrodes or substrate. CONSTITUTION:The color filters are formed on the glass substrate and the over coating layers formed thereon have the two-layered structure. The 1st over coating layer having the coefft. of thermal expansion smaller than the coefft. of thermal expansion of the color filters is laminated on the color filters and the 2nd over coating layer having the coefft. of thermal expansion smaller than the coefft. of thermal expansion of the 1st over coating layer is formed thereon. The electrodes are formed thereon. The stress of the electrodes by thermal expansion is thereby decreased and the disconnection of the electrodes is hardly generated. The element having the high durability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color liquid crystal display element suitable for color, high-density display.

[Prior Art] Various types of liquid crystal display elements that have a color filter on the inner surface of a liquid crystal cell and perform color display have been proposed and put into practical use in color liquid crystal televisions and the like.

This has two structures, one on the substrate.

One is a structure in which an electrode is formed on a substrate and a color filter is formed thereon, and the other is a structure in which a color filter is formed on a substrate and an electrode is formed thereon.

The former is generally applied to simple matrix liquid crystal display elements, and uses electrodes in the form of fine stripes arranged in rows and columns. In this structure, the electrodes are formed on the substrate below the color filters, so even if there is a difference in thermal expansion coefficient between the color filters and the electrodes, the electrodes are hardly damaged.

The latter is generally applied to active matrix liquid crystal display elements, and if the color filter is provided on the common electrode side, the common electrode is not thinned, so there is a possibility of defects such as electrode breakage. low.

The former has the advantage of being relatively easy to manufacture and being able to produce color liquid crystal display elements at low cost compared to the latter, but because the applied voltage is partially distributed to a color filter with a low dielectric constant. However, the voltage component effectively applied to the liquid crystal layer decreases, the voltage vs. transmittance characteristic becomes dull, and it is difficult to obtain a sufficient contrast ratio when the number of scanning lines is increased.

Furthermore, when forming electrodes on color filters, the electrodes had to be formed at low temperatures due to the low durability of color filters, and there was no way to stably and reliably form thin transparent electrodes.

This is because the thermal expansion coefficient of a color filter made of cured resin is on the order of 10-5/deg, whereas the thermal expansion coefficient of a glass substrate and transparent electrode is 10-'/deg or 10-'/deg. This difference in thermal expansion causes cracks in the thin transparent electrode, leading to wire breakage. Furthermore, since the color filter is soft, the mechanical strength of the transparent electrode formed on the color filter is low, resulting in the problem that the electrode can be easily scratched or damaged.

[Problem to be solved by the invention] An object of the present invention is to provide an electrode on a color filter,
To obtain a color liquid crystal display element that can obtain a sufficient contrast ratio even when the number of scanning lines is increased, and to improve the stability and reliability of the electrodes even though the electrodes are provided on the color filter. It is.

In particular, it makes it difficult for the electrodes to crack due to differences in thermal expansion due to temperature changes.

[Means for Solving the Problems 1] The present invention has been made without solving the above-mentioned problems, and involves forming a color filter on a glass substrate, and forming a layer on a transparent overcoat 1 on top of the color filter. Further, a first substrate on which an electrode is formed and a second substrate on which an electrode is formed are arranged so that the electrode surfaces face each other, and the peripheral part is sealed with a sealing material, and the inside is sealed. In a color liquid crystal display element that encapsulates liquid crystal, two transparent overcoat layers are used.
It has a layered structure, in which a first overcoat layer having a lower coefficient of thermal expansion than the color filter is laminated on the color filter, and a second overcoat layer having a lower coefficient of thermal expansion than the tenth overcoat layer is laminated on top of the first overcoat layer having a lower coefficient of thermal expansion than the tenth overcoat layer. The present invention provides a color liquid crystal display element characterized in that an overcoat layer is formed and electrodes are formed on the overcoat layer.

The present invention uses a substrate having a structure in which a color filter is provided on the inner surface of the substrate of a liquid crystal display element, a transparent two-layer overcoat layer is formed on the color filter, and electrodes are further provided on top of the color filter. .

As the substrate used in the present invention, a glass substrate used for ordinary liquid crystal display elements can be used.

For this first substrate, a color filter is formed on the substrate, two transparent overcoat layers are formed thereon, and ITO (In203-3n02) is formed on the substrate.
), 5n02, etc. with transparent electrodes are used.

As this color filter, any known color filter forming method such as dyeing method, printing method, method of buttering photocurable colored resin, etc. can be used, and if necessary, a light-shielding film is placed between them. Addition of configurations such as forming a hardened film between the filter and the substrate to improve adhesion, and forming a film on the color filter to correct unevenness of the color filter or improve electrode adhesion. You can.

This color filter is usually made of hardened resin and has a coefficient of thermal expansion on the order of 10-5/deg.

On the other hand, the coefficient of thermal expansion of the glass substrate and transparent electrode described above is on the order of 10-6/deg or 10-7/deg.

A transparent overcoat layer is usually formed on the color filter to flatten the unevenness of the color filter or to form a hard layer.

In the present invention, this overcoat layer is made into two layers, the first overcoat layer is placed on the color filter side, and then the second overcoat layer is placed on the color filter side.
an overcoat layer is disposed, and an electrode is formed adjacent to the second overcoat layer.

The coefficient of thermal expansion of this first overcoat layer is made smaller than that of the color filter. The second overcoat layer has a lower coefficient of thermal expansion than the first overcoat layer and a higher coefficient of thermal expansion than the electrode and substrate.

For these two overcoat layers, it is generally preferable to use a material that has the effect of flattening the surface of the color filter and increasing the surface hardness. Specifically, epoxy-based, acrylic-based, silicone-based materials, etc. can be used. Among these, acrylic materials can be selectively coated by photolithography. Furthermore, epoxy-based and silicon-based materials can be applied selectively by masking the parts that are not desired to be applied and then removing the mask.

The setting of the thermal expansion coefficient of these 21 layers is as follows:
It varies depending on the resin used, and is usually controlled by the type and amount of the inorganic particles added.

Typically, the first overcoat layer has a coefficient of thermal expansion of 10'
The coefficient of thermal expansion is lower than that of the color filter, on the order of ~10-6760 g. As for the material, the aforementioned epoxy-based, acrylic-based, and silicon-based materials are all suitable.

The setting of this coefficient of thermal expansion is controlled by the structure of the resin used or the type and amount of the inorganic particles added.

The second overcoat layer has a coefficient of thermal expansion of 10-6 to 10
On the order of -7/deg, the coefficient of thermal expansion is lower than that of the first overcoat layer, and higher than that of the glass substrate and electrodes. This material is preferably the silicon-based material mentioned above.

This thermal expansion coefficient can be set by adding an appropriate amount of a silicon compound or other resin containing an organic chain or a large amount of organic chains to the side chain of the molecular structure of the resin used, or by adding the type of inorganic fine particles to be added. and controlled by the amount added.

Depending on the coefficient of thermal expansion, these two overcoat layers may have a structure of three or more layers as necessary.

The total thickness of this overcoat layer may be about 1 to 5 μm, and the thickness of each layer is usually 0.5 to 4 μm.
It may be approximately m or may be determined as appropriate.

This first single barcode layer is made to almost completely cover the top of the color filter. For this reason, it is preferable that the pattern extends slightly to the periphery of the color filter pattern. However, the part where electrodes are not provided even if it is the second part of the color filter,
This first overcoat layer may not be provided.

Preferably, the second overcoat layer 1 to 1 covers a wider area than the first overcoat layer. This is to prevent the electrode from being directly formed on the first overcoat layer in the portion where the electrode is drawn out to be taken out to the terminal.

Furthermore, although this overcoat layer is transparent, it does not have to be completely colorless and transparent as long as it does not deteriorate the characteristics of the color filter even if it is slightly colored.

In the present invention, electrodes are formed on these two overyaw layers 1 to 1. This electrode is usually I
A transparent electrode such as T O (In2O3-3nOa) or 5n02 may be used, and the transparent electrode may be formed by a known low-temperature process such as vapor deposition or sputtering.

Moreover, a low-resistance non-transparent electrode such as a thin metal wire may be provided alongside this transparent electrode.

On top of this, an insulating layer and an alignment layer are provided as necessary.

On the other hand, electrodes are formed on a normal substrate, a counter electrode substrate is created with an insulating layer and an alignment film provided as necessary, and a substrate with a color filter as described above is placed on this with the electrode surfaces facing each other. The periphery is sealed with a sealant, and liquid crystal is sealed inside to form a liquid crystal cell.

The present invention is a twisted nematic (TN) liquid crystal display element.
) It can also be used for liquid crystal display elements, such as super twisted nematic (STN) liquid crystal display elements, which have been attracting attention in recent years, and ferroelectric liquid crystal display elements using smectic liquid crystal.

In particular, we have developed a black-and-white STN liquid crystal cell for display in which the twist angle of liquid crystal molecules is 16(] to 3[)0°, and a reverse twist liquid crystal element without electrodes and birefringence compensation means such as a birefringence plate laminated. It is suitable for use as a color liquid crystal display element by applying it to a super twist liquid crystal display element and providing a color filter thereto. In such a black and white super twist liquid crystal display element in which a birefringence compensation means is laminated on a display liquid crystal cell, the birefringence compensation means compensates for circularly polarized light passing through the display liquid crystal cell, and no color filter is provided. In most cases, a nearly black and white display can be obtained, so by providing a color filter, a color liquid crystal display element with a high contrast ratio and a wide viewing angle can be easily obtained.

Such a black and white super twist liquid crystal display element requires very strict control of the substrate gap, so it is necessary to adopt a configuration in which color filters are accurately provided under the electrodes as in the present invention. The advantages of adopting the two-layer overcoat layer structure are extremely large.

Further, in the second example, a color filter is provided on one substrate, but the color filter may be formed by dividing the substrate into both substrates.

In the present invention, other components of the liquid crystal display element, such as an alignment film, an insulating film, a liquid crystal material, a sealing material, a polarizing plate, a reflecting plate, an illumination means, a driving circuit, etc., are the same as those for a known liquid crystal display element. Can be used.

For example, known rubbing methods, oblique evaporation methods, etc. can be used to orient liquid crystal molecules in a specific direction, and if necessary, inorganic materials such as SiO□, Ti09, Δ1°O7, etc. After forming the film and/or the film of an organic material such as polyimide or polyamide, alignment treatment may be performed.

In addition to this, the present invention includes, within the scope that does not impair the effects of the present invention,
Various techniques used in ordinary liquid crystal display elements can be applied.

The color liquid crystal display device of the present invention is suitable as a color display device for personal computers, word processors, workstations, etc. In addition, color liquid crystal display devices, color display fish finders, color display devices for automobiles, color display radars, etc. color display oscilloscope,
It can be used for various purposes such as various dot matrix display devices for color display.

[Operation 1] In the present invention, between the color filter having a large coefficient of thermal expansion and the electrode or substrate having a small coefficient of thermal expansion, two overlapping layers having a coefficient of thermal expansion between them and different coefficients of thermal expansion are formed. By stacking the coat layers, the risk of electrode disconnection due to thermal expansion of the color filter is reduced.

That is, the process of manufacturing a liquid crystal cell involves the formation of ITO,
Since the substrate is heated to some extent during processes such as forming an alignment film and curing a seal, a temperature change occurs due to the heating.

Furthermore, even after a product has been commercialized, there are environmental temperature changes during actual use of the product. In response to such temperature changes, there is a risk that the color filter will thermally expand and disconnect the electrodes with different coefficients of thermal expansion, but with the present invention, the 2N
By laminating the overcoat layer, stress on the electrode due to thermal expansion is reduced, electrode disconnection becomes less likely to occur, and a highly durable element can be obtained.

In addition, by forming an overcoat layer on these two layers, the unevenness on the surface of the color filter is flattened, which improves the uniformity when controlling the gap between the substrates by dispersing spacers within the surface of the liquid crystal cell. .

In particular, by using a material with hard coat properties for this overcoat layer, the base of the electrode becomes hard, which improves the mechanical strength of the electrode and has the advantage of making it less likely to be scratched during handling.

In addition, by forming the second overcoat layer to cover a wider area than the first overcoat layer, the second overcoat layer has a low coefficient of thermal expansion from the part above the color filter to the terminal part. The reliability of the electrode is improved because the layer is formed on the substrate.

[Example] Example 1 Glass substrate - Thickness of 3 colors of RGB by crab dyeing method 2.0
Thick film color filters of μm were formed to correspond to a group of 960 striped column electrodes, and black light-shielding portions were formed between the color filters by a dyeing method. On top of this, the color bar 1 is made of acrylic bar 1, which has a coefficient of thermal expansion smaller than that of the collar 1.
A coating agent was applied over the entire surface using a spinner, and a first overcoat layer having a thickness of about 1 μm was formed on the color filter and its surrounding area by photolithography. Next, a silicone heart coat agent, which has a lower thermal expansion coefficient than the acrylic heart coat agent and a higher thermal expansion coefficient than ITO produced by low-temperature sputtering, is applied to the entire surface using a spinner to a thickness of approximately 1.
A second overcoat layer of .mu.m was formed.

On top of this, ITO was applied by low-temperature sputtering method (substrate iXM degree 18
0° C.) to form a group of 960 striped column electrodes with a pitch of 200 μm.

Furthermore, an insulating film of SiO□-T102 was formed on this to a thickness of 1100 nm by vapor deposition, and polyimide was laminated to a thickness of about 70 nm, and this was rubbed to form an alignment film to produce a column electrode substrate.

On the other hand, ITO was deposited on a glass substrate at high temperature, and was patterned to have a 200 mm diameter perpendicular to the column electrode group.
Forming a book stripe-shaped row electrode group, 5102-T1
An insulating film of No. 02 was formed to a thickness of 300 nm, and polyimide was laminated to a thickness of about 70 nm, and this was rubbed to form an alignment film to form a row electrode substrate.

The column electrode substrate and row electrode substrate are arranged so that the helix angle of the liquid crystal molecules is 90°, the periphery is sealed with a sealing material to form a cell, and nematic liquid crystal is injected to form a dot matrix liquid crystal cell. was manufactured.

This Totmar 1~Rix liquid crystal cell exhibited almost the same contrast ratio and viewing angle characteristics as a conventional liquid crystal cell (Comparative Example 1) in which the ITO column electrode substrate was placed on a color filter and one overcoat layer was provided. Ta. Also, Retsuden Fi!
The liquid crystal cell (under the top of the board or the color filter)
Compared to Comparative Example 2), it exhibited a high contrast ratio and wide viewing angle characteristics.

Furthermore, this liquid crystal cell was subjected to a heat cycle test of -30°C to +90°C IO cycle, 80°C 190%, 20°C
Even in the 0-hour high-temperature humidity test, no electrode breakage occurred.

In addition, the electrode on the color filter side of this liquid crystal cell was
When a felt cloth was subjected to an abrasion test by soaking it in water while applying a load of 00 g/cm2, it showed abrasion resistance of 100 times or more, which is the number of times the electrical resistance doubled.

On the other hand, in the liquid crystal cell of Comparative Example 1, about 20% of electrode disconnections occurred in the heat cycle test and about 10% in the high temperature humidity resistance test.

Furthermore, the liquid crystal cell of Comparative Example 1 had durability in the scratch test of about 60 times.

Example 2 The second overcoat layer of Example 1 was applied to the silicone bar 1 using a spinner, with the peripheral area masked so that it adhered to the first overcoat layer and its surrounding area. A liquid crystal cell was formed in the same manner as in Example 1, except that the first overcoat layer and its peripheral portion were formed.

This liquid crystal cell showed the same reliability as Example 1.

[Effects of the Invention] In the present invention, two overcoat layers having an intermediate coefficient of thermal expansion are laminated between a color filter having a high coefficient of thermal expansion and an electrode or a substrate having a low coefficient of thermal expansion. As a result, wire breakage is less likely to occur due to temperature changes due to the process of manufacturing the liquid crystal cell and environmental temperature changes during actual use, making it possible to obtain a highly durable element.

Furthermore, these two overcoat layers improve the flatness of the unevenness of the color filter and improve the uniformity of the gap between the cell substrates.

In particular, by using a material having heart coat properties for this overcoat layer, the mechanical strength of the electrode is improved and there is also the advantage that it is less likely to be scratched during handling.

In addition, by forming the second overcoat layer to cover a wider area than the first overcoat layer, there is no part where the electrode is directly formed on the first overcoat layer with a low coefficient of thermal expansion. , improving the reliability of the electrode.

The present invention can be applied to known liquid crystal display elements in various ways without detracting from the effects of the present invention.

Q

Claims (1)

[Claims] (1) A color filter is formed on a glass substrate, a transparent overcoat layer is formed on it, a first substrate is formed with an electrode on it, and a second substrate is formed with an electrode. In a color liquid crystal display element in which the surfaces are arranged to face each other, the periphery thereof is sealed with a sealing material, and the liquid crystal is sealed inside, two transparent overcoat layers are used.
It has a layered structure, in which a first overcoat layer having a smaller coefficient of thermal expansion than the color filter is laminated on the color filter, and a second overcoat layer having a smaller coefficient of thermal expansion than the first overcoat layer is laminated on top of the color filter. 1. A color liquid crystal display element comprising an overcoat layer formed thereon and electrodes formed thereon.