JPH09251161A - Substrate for display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a substrate for a display element having high resistance against an electric field, high heat and moisture resistance and water resistance in the voltage input terminal by depositing, from a transparent substrate, a lower antireflection layer, a metal layer and an upper antireflection layer to constitute a transparent electrode for a display part, while forming only the lower antireflection layer as the electrode in the input terminal part. SOLUTION: A transparent electrode 4 is patterned into a predetermined form of an electrode on the surface of a glass substrate 5. The transparent electrode 4 consists of a transparent electrode 4a in a display part and an electrode 4b in an input terminal part which is extended from the transparent electrode 4a to the edge of the glass substrate. The transparent electrode 4a in the display part consists of a laminated body comprising, from the glass substrate 5, a lower antireflection layer 1, a metal layer 2 and an upper antireflection layer 4 deposited in this order, while the electrode 4b in the input terminal part consists of only the lower antireflection layer 1. Since no metal layer is used on the contact point with a transparent electrode of an external input terminal and on the area near the contact point, the obtd. substrate having a transparent conductive film has both of high transmittance for visible rays and durability against an electric field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate with a transparent electrode used for a thin display device such as a liquid crystal display device,
Particularly, the present invention relates to a substrate with a transparent electrode, which is preferably used for a liquid crystal display device having a large area, high definition, and high speed response, and a liquid crystal display device using the same. Further, the substrate with a transparent electrode of the present invention can be applied to a display element driven by other electric signals such as a plasma display element and a plasma addressed liquid crystal display element.

[0002]

2. Description of the Related Art Conventionally, as a substrate with a transparent electrode used for a liquid crystal display element, tin-containing indium oxide (I
A glass substrate coated with (TO) is used. The ITO transparent electrode of this substrate, which is patterned into a transparent electrode of a predetermined shape, has excellent transparency to visible light, but the transparent conductive film has a large resistivity of the order of 10 ⁻⁴ Ωcm. There is a problem that the film thickness of the transparent electrode must be increased in order to increase the area and realize the high definition display and the high speed response.

If the thickness of the transparent conductive film is increased, it becomes difficult to form electrodes with a high definition in a high yield, and a remarkable step due to the transparent electrodes is formed inside the liquid crystal display element. There is a problem in that the alignment process of the liquid crystal by the above causes the alignment defect around the step portion. In order to solve this problem, a silver thin film having a low resistivity is used as a conductive layer, and in order to improve the transmittance, this silver layer is sandwiched between conductive antireflection layers such as ITO, and has a three-layer structure transparent electrode. As a transparent electrode for liquid crystal display
It is disclosed in Japanese Patent No. 87399 and Japanese Patent Application Laid-Open No. 7-114841.

[0004]

However, the conventional technique of using a silver thin film for the conductive layer has both transparency (visible light transmittance) and low resistance characteristics, but the strong electric field at the input terminal connecting portion However, there is a problem that silver migrates and causes corrosion deterioration. Further, since the vicinity of the input terminal portion is used in a state of being directly exposed to the outside air, there is a problem that the moisture resistance and the water resistance are not sufficient and the material deteriorates with time. The present invention has been made in order to solve the above-mentioned problems of the related art.

[0005]

The present invention provides a substrate with a transparent electrode for a display element, in which a transparent electrode is formed on one main surface of a transparent substrate, which serves as a display portion when the display element is formed. The transparent electrode, the lower antireflection layer counting from the transparent substrate, a metal layer, an upper antireflection layer are laminated in this order, the electrode of the input terminal portion connected to the transparent electrode of the display unit, the lower antireflection layer, the It is a substrate with a transparent electrode for a display element, which is a laminated body in which an upper antireflection layer or a transparent substrate is coated with the lower antireflection layer and the upper antireflection layer in this order, and is made conductive.

When the substrate with a transparent electrode of the present invention is used for a liquid crystal display element, the transparent electrode of the display portion in the closed space (in the liquid crystal cell) in which the liquid crystal is sealed is the lower antireflection layer counted from the transparent substrate, The metal layer and the upper antireflection layer are assembled in this order to form a laminated body.

Further, at least the input terminal portion and the transparent electrodes in the vicinity thereof are connected to the transparent electrodes of the display section, and the lower antireflection layer, the upper antireflection layer, or the lower antireflection layer and the upper antireflection layer from the transparent substrate side. Are coated in this order to form a laminated body, and are assembled so as to form a conductive layer.

The lower antireflection layer or the upper antireflection layer of the present invention has a refractive index of 1.6 to 550 nm.
A metal oxide transparent in the visible light wavelength range of 2.9 can be used. These metal oxides include indium oxide, zinc oxide, tin oxide, neodymium oxide, zirconium oxide, cerium oxide, cadmium oxide, antimony oxide, tantalum pentoxide, bismuth oxide, titanium dioxide, aluminum oxide and mixtures thereof. A complex oxide can be illustrated. Further, silicon dioxide having a smaller refractive index can be used as a mixture with the transparent metal oxide for the purpose of adjusting the refractive index.

The upper antireflection layer of the present invention is preferably a layer containing indium oxide as a main component, and in particular, indium oxide containing tin (ITO) is preferable. A layered body in which a layer containing zinc oxide as a main component and a layer containing indium oxide as a main component are stacked in this order is also preferably used.
In this case, zinc oxide (A
Most preferred is a laminate of ZO or ZnO: Al) and ITO.

In the present invention, the transparent electrode of the input terminal portion is formed of the antireflection layer. Here, the input terminal portion includes the contact portion with the external input device provided in the peripheral portion of the glass substrate and its vicinity, and the glass substrate on the outer peripheral side of the encapsulating material for enclosing the liquid crystal substance between the two transparent substrates. Includes all of the surface. Further, the boundary between the transparent electrode of the display section and the transparent electrode of the input terminal section may be provided at a position in the liquid crystal cell that does not substantially participate in image display or at a position where the sealing material is provided. In the present invention, the conductivity of the transparent electrode of the display unit,
Although it is ensured by a metal layer which is transparent to visible light, the transparent electrode of the input terminal portion needs to be ensured by the conductivity of the lower antireflection layer or the upper antireflection layer. Therefore, either one of the lower antireflection layer and the upper antireflection layer must be a transparent conductive metal oxide. Such oxides include indium oxide,
Examples thereof include oxides containing indium oxide as a main component and zinc oxide containing a small amount of aluminum. In particular, ITO is preferable in terms of easy electrode processing.

For the metal layer of the present invention, silver or a metal containing silver as a main component is preferably used. Metals such as palladium, gold and platinum may be included in silver to the extent that resistance is not significantly lowered and in order to improve resistance to heat and humidity. The volume resistivity of the metal layer at this time is preferably 10 μΩcm or less.

In the present invention, the thickness of the lower antireflection layer is preferably 10 to 200 nm and the thickness of the metal layer is 5 to 100 nm in order to secure transparency to visible light and low sheet resistance. The thickness of the upper antireflection layer is preferably 10 to 200 nm.

The metal layer of the present invention can be further divided into two or more layers with a dividing layer having the same composition as the lower antireflection layer or the upper antireflection layer. That is, by inserting one or more dividing layers, it is possible to divide into two or more metal layers. As a result, if the sheet resistance is almost the same as in the case where the metal layer is not divided,
A substrate with a transparent conductive film having higher transmittance can be obtained. When the metal layer is divided as described above, the total thickness of the divided metal layers is preferably 100 nm or less.

As the substrate that can be used in the present invention, not only known glass substrates such as glass of soda lime silica composition and borosilicate glass (non-alkali glass) but also polyethylene terephthalate (PET) and acrylic (PMMA) are used. Examples thereof include a plastic substrate, a plastic film, and a substrate provided with a color filter for the purpose of color display on the surface of these substrates. Further, these substrates do not have to be flat and may be substrates having a curved surface.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 shows an example of a substrate with a transparent electrode according to the present invention.
A transparent electrode 4 is formed on the surface of a glass substrate 5 whose surface is covered with a silicon dioxide film (not shown) for preventing alkali elution.
Are electrode-formed into a predetermined shape. The transparent electrode 4 is composed of a display portion 4a used as a liquid crystal display element and an electrode 4b of an input terminal portion which is connected to the transparent electrode 4a of the display portion and is extended to the end of the glass substrate. The transparent electrode 4a of the display unit is, as shown in the AA sectional view of FIG.
The lower antireflection layer 1, the metal layer 2, and the upper antireflection layer 3 are made of a laminated body which is coated in this order from the glass substrate 5 side, and the electrode 4b of the input terminal portion is composed of only the lower antireflection layer 1. . FIG. 5 is a cross-sectional view of an embodiment of a liquid crystal display device produced using the substrate with a transparent electrode of the present invention. Two glass substrates with a transparent electrode according to the present invention are adhered at regular intervals with a sealing material 14 made of an organic resin such as an epoxy resin to form a liquid crystal cell 13 having a sealed space. Liquid crystal in the liquid crystal cell 13 (indicated by a black circle in the figure)
The liquid crystal is contained, and the alignment is controlled by the voltage applied between the transparent electrodes coated with the alignment film 12 for aligning the liquid crystal on the surface, and images and characters are displayed. In FIG. 5, the transparent electrode 4 of the display unit of the present invention is shown.
The boundary between the liquid crystal cell 13a and the transparent electrode 4b of the input terminal is
It is provided in the inner peripheral area.

The electrode 4b of the input terminal portion is provided on the entire outer surface of the liquid crystal cell 13 which is directly exposed to the outside air, and is connected to the input terminal 16 at the tip portion of the glass substrate of the input terminal portion electrode.

For each layer of the above-mentioned substrate with a transparent electrode, a masking plate is appropriately provided between the glass substrate and the raw material (target for sputtering, evaporation material for vapor deposition) for coating the layer by sputtering or vacuum vapor deposition. It can be performed by a method.

For example, ITO as the lower antireflection layer 1 is formed on the entire surface of the glass substrate by sputtering or vacuum deposition.
And then the silver as the metal layer 2 and the ITO as the upper antireflection layer 3 are sputtered through a masking jig that opens the central portion of the glass substrate to be the display portion and shields the peripheral portion. A method of subsequently forming a coating by a vacuum vapor deposition method can be used. After that, if necessary, by acid etching using a photolithographic method using a photosensitive resist or dry film,
The electrodes of the three layers of ITO, silver and ITO are processed into a predetermined shape in one step.

FIG. 3 shows another embodiment of the substrate 6 with a transparent electrode according to the present invention. An acid-insoluble transparent insulating film such as titanium oxide serving as the lower antireflection layer 1 is formed on the portion 4a of the glass substrate 1 that serves as a display portion by a sputtering or vacuum deposition method performed through a masking jig. And a silver layer as the metal layer 2 is coated and laminated. Thereafter, the entire glass substrate is covered with ITO as the upper antireflection layer 3 without using a masking jig. The obtained transparent electrode-attached substrate was subjected to etching with an acid using a photolithography method, and the IT of the silver layer and the upper antireflection layer was obtained as necessary.
The electrode of O is processed into a predetermined shape in one step.

FIG. 4 shows another embodiment of the present invention, which is a display portion 4a.
The electrode of 5 is composed of 5 layers of glass substrate / ITO layer as lower anti-reflection layer / silver layer / ITO layer as dividing layer / silver layer / ITO layer as upper anti-reflection layer, and the electrode 4b in the input terminal part is the lower part. It shows that it is composed of an ITO layer as an antireflection layer. In this case, the electrode of the input terminal portion may be an ITO layer which is coated three times, that is, an ITO layer as a lower antireflection layer / an ITO layer as a division layer / an ITO layer as an upper antireflection layer.

The transparent electrode, which is a connection point with the input terminal device, has a chemical durability evaluated by high electric field resistance, high humidity resistance and high alkali resistance, and high visible light transmittance including the substrate. The electrical characteristics evaluated by transparency and low sheet resistance, and the electrode workability evaluated by ease of etching and in-plane uniformity were evaluated. From these characteristics, as a particularly preferred embodiment of the present invention, the sheet resistance value is about 2.5Ω / □ or less 1, 5Ω / □ or more, and the visible light transmittance is 60%.
In the display cell in which the transparent electrode having the above characteristics is sealed, a laminated structure of substrate / ITO / silver / ITO / silver / ITO is adopted, and the transparent electrode of the input terminal is substrate / ITO, substrate / I.
TO / ITO (a laminated body of ITO of the lower antireflection layer and ITO of the upper antireflection layer) or substrate / ITO / ITO
/ ITO (meaning a laminated body of ITO as a lower antireflection layer, ITO as a dividing layer, and ITO as an upper antireflection layer). The substrate of the present invention having a visible light transmittance of 60% or more in the range of 1.5Ω / □ or less includes a substrate / ITO / silver / I in the display unit.
It has a laminated structure of TO / silver / ITO / silver / ITO, and the electrodes of the input terminal are substrate / ITO, substrate / ITO / ITO,
Substrate / ITO / ITO / ITO or Substrate / ITO /
An example is one composed of ITO / ITO / ITO.

The present invention will be described below with reference to examples. Example 1 A glass substrate of 400 mm in length, 300 mm in width and 0.7 mm in thickness having a soda lime silica composition for simple matrix liquid crystal display was washed, and then a silicon dioxide layer for alkali passivation was formed to a thickness of 30 nm. Then, using indium oxide containing 10% by weight of tin oxide and silver as sputtering targets, respectively, by a DC sputtering method, IT
O layer / silver layer / ITO layer having a thickness of 40 nm, 15
nm and 40 nm are sequentially coated on the glass substrate,
A sample 1 of a substrate with a transparent electrode was obtained. At this time, a masking jig was used to prevent the silver layer from being coated on and near the place where the voltage input device was connected. The electrode of the input terminal portion of this sample 1 is composed of an ITO single layer, and the lamination is formed by sputtering the lower antireflection layer ITO and the upper antireflection layer ITO twice.
The film formation history of the electrode of the input terminal portion is represented by a slash. Table 1 collectively shows the configuration of the electrodes and the results of the durability test.

The transparent electrode thus obtained was patterned by an etching solution containing an aqueous solution containing hydrochloric acid and nitric acid as an acid so as to form a stripe transparent electrode having an electrode width of 70 μm and an electrode interval of 15 μm by a photolithography method. Examples 2 to 6 Using the same glass substrate as in Example 1, the electrode structure of the display section,
By changing the electrode structure of the input terminal portion and the division of the metal layer, Samples 2 to 6 of the substrate with a transparent electrode of the present invention were obtained. Table 1 shows the structures of these electrodes, the film formation history of the input terminal portion, and the durability test results.

Comparative Examples 1 to 4 Comparative samples 1 to 4 of transparent electrode-equipped substrates in which a silver layer was provided as a metal layer on both the display portion and the input terminal portion were prepared using the same glass substrate as in the examples. . Table 1 shows the durability test results evaluated by the same method as in the electrode structures of Samples 1 to 4 and Example 1. The obtained transparent electrode was subjected to an electrode pattern processing by a photolithography method so as to form a striped transparent electrode having an electrode width of 70 μm and an electrode interval of 15 μm with an etching solution containing an aqueous solution containing hydrochloric acid and nitric acid as acids.

[0025]

[Table 1]

From the above examples, the electrodes of the substrate with a transparent electrode of the present invention have a much higher durability against voltage application at the input terminal portion than those having the electrode structure of the comparative example described as the prior art. It turns out to be excellent. In addition, if the transparent electrode having a structure containing silver is provided in the liquid crystal cell without being provided in a portion exposed to the external atmosphere of the liquid crystal display element, the durability against voltage application is improved, and the wet heat resistance and water resistance are improved. Expected to be obtained together.

[0027]

According to the substrate with a transparent electrode of the present invention, the electrode serving as the liquid crystal display part has a high visible light transmittance including a metal layer and a low resistance, and at least the transparent electrode of the external input terminal other than the display part. Since a metal layer is not used at the contact point with and in the vicinity thereof, a substrate with a transparent conductive film that has both low resistance and high visible light transmittance in the display section having a large area and high electric field resistance in the electrode section of the input terminal section Can be This makes it possible to obtain a large-screen, high-quality display element with excellent durability.

[0028]

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a substrate with a transparent electrode film for a display device of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a cross-sectional view of another embodiment of the substrate with a transparent electrode for a display device of the present invention.

FIG. 4 is a cross-sectional view of another embodiment of the substrate with a transparent electrode for a display device of the present invention.

FIG. 5 is a cross-sectional view of an embodiment of a liquid crystal display device using the substrate with a transparent electrode for a display device of the present invention.

[0029]

[Explanation of symbols]

1: Lower Antireflection Layer 2: Metal Layer 3: Upper Antireflection Layer 4: Transparent Electrode 4a: Transparent Electrode of Display 4b: Transparent Electrode of Input Terminal 5: Transparent Substrate 6: Substrate with Transparent Electrode of the Present Invention 10: Color filter 11: Protective film 12: Alignment film 13: Liquid crystal cell 14: Encapsulating material 15: Liquid crystal display device using the substrate with a transparent electrode of the present invention 16: Input device

Claims (7)

[Claims] 1. A substrate with a transparent electrode for a display element, wherein a transparent electrode is formed on one main surface of a transparent substrate, wherein the transparent electrode serving as a display portion when the display element is formed is the transparent substrate. Bottom anti-reflection layer, metal layer, counting from
The upper antireflection layer is laminated in this order, and the electrode of the input terminal portion connected to the transparent electrode of the display unit is formed from the lower antireflection layer, the upper antireflection layer or the transparent substrate to the lower antireflection layer and the upper antireflection layer. A substrate with a transparent electrode for a display element, which is a laminated body in which layers are coated in this order, and is made conductive. 2. The substrate with a transparent electrode for a display element according to claim 1, wherein a color filter is provided between the transparent electrode that serves as the display section and the transparent substrate. 3. The lower antireflection layer is a transparent metal oxide layer having a refractive index of 1.6 to 2.9 at a wavelength of 550 nm, and the upper antireflection layer is a layer containing indium oxide as a main component. Item 3. A substrate with a transparent electrode for a display device according to item 1 or 2. 4. The lower antireflection layer is a layer of a transparent metal oxide having a refractive index of 1.6 to 2.9 at a wavelength of 550 nm, and the upper antireflection layer is a layer containing zinc oxide as a main component and an oxide. The substrate with a transparent electrode for a display element according to claim 1, which is a laminate in which layers containing indium as a main component are laminated in this order. 5. The substrate with a transparent electrode for a display element according to claim 3, wherein the lower antireflection layer is a layer containing indium oxide as a main component. 6. The metal layer of the transparent electrode which becomes the display section is n.
The substrate with a transparent electrode for a display element according to any one of claims 1 to 5, wherein (n is an integer of 1 or more) layers divided into n + 1 layers with a division layer containing indium oxide as a main component. 7. A liquid crystal display device using the substrate with a transparent electrode for a display device according to claim 1.