Conductive laminate

Details Conductive laminate Conductive laminate

1986-06-18

1989-05-30

Swisher, Nancy A. B.

Stock material or miscellaneous articles

Composite

Of metal

428212, 4284722, 428480, 428701, 174 685, B32B 900, B32B 2706

Patent

active

048350613

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a conductive laminate, and more specifically to a conductive laminate suitably used in display devices such as a liquid crystal display device.
2. Background Art
Transparent conductive films and transparent conductive laminates are widely used in the electric and electronic fields including those concerning not only electrodes for liquid crystal display devices, electroluminescence display devices, and photoconductive photosensitive elements, but also cathode ray tubes, electrostatic shielding layers in the window portions of various measurement apparatuses, antistatic layers, and heating elements. Of them, transparent conductive films having selective light transmittance has an infrared ray reflection property and are utilized as window materials in collectors for utilization of solar energy and in buildings. A transparent electrode never fail to be used in various solid display devices wherein an electroluminescence, liquid crystal, plasma, or ferroelectric substance is used, which have been developed as substitutes for cathode ray tubes with the progress of information processing technologies. Besides, a film having transparency and electroconductivity is required in new photoelectric elements and recording materials utilizing interaction or interconversion between electric and optical signals, which are regarded as useful in the information processing technique from now on. These transparent conductive layers can be utilized also in condensation-proof window glass used in automobiles, airplanes, etc., in antistatic films for polymers, glass, etc., and in transparent heat-insulating windows for prevention of dissipation of solar energy. In liquid crystal, electroluminescence, plasma, electrochromic, and fluorescence display devices, etc., a demand particularly for high-quality picture element display has recently increased. Under these circumstances, there has been a proposal according to which the portion of a picture element and the signal input line are formed with an electrode made of a transparent conductive layer and a low resistance electrode, respectively, to attain improvements in the display speed of the picture element and the quality of images.
On the other hand, patterning of the transparent conductive layer of a conductive laminate in display devices such as a liquid crystal display device is generally effected by photoetching, which includes the step of immersion in an alkali to remove a photoresist remaining on the conductive laminate and the step of washing the surfaces of the conductive laminate with an acid after patterning. In these steps, cracking or local peeling sometimes occurs in the transparent conductive layer, leading to a grave defect to the conductive laminate as will be described later.
Although the cause of the above-mentioned phenomenon has not been elucidated, it is believed to be due to the action of an internal stress setting up in the transparent conductive layer because of a difference in thermal expansion coefficient between the substrate and the transparent conductive layer.
Specifically, in deposition of the transparent conductive layer on the substrate by vacuum evaporation, the substrate is heated at a temperature of 300.degree. C. or lower to raise the degree of oxidation of the deposited layer for the purpose of improving the transparency and electroconductivity thereof. The thermal expansion coefficient of the substrate is 5.5.times.10.sup.-5 cm/cm/.degree.C. in the case of polyether-sulfone (PES) and 1.5.times.10.sup.-5 cm/cm/.degree.C. in the case of polyethylene terephthalate (PET), while the thermal expansion coefficients of, for example, indium oxide (In.sub.2 O.sub.x, x.ltoreq.3) and indium-tin oxide (ITO) are of the order of 10.sup.-6 cm/cm/.degree.C. Thus, there is a large difference in thermal expansion coefficient between the substrate and the transparent conductive layer. Therefore, it is believed that, at room temperature, an internal stress may set up in the transparent conductive

REFERENCES:
patent: 4613549 (1986-09-01), Tanaka
patent: 4622120 (1986-11-01), Gillery

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