Method for producing light-transmitting electromagnetic wave-shielding film, light-transmitting electromagnetic wave-shielding film and plasma display panel using the shielding film

Abstract

A silver salt-containing layer containing a silver salt and provided on a support is exposed and developed to form a metal silver portion and a light-transmitting portion, and then the metal silver portion is further subjected to physical development and / or plating to form a conductive metal portion consisting of the metal silver portion carrying conductive metal particles. A method for producing a light-transmitting electromagnetic wave-shielding film which enables production of an electromagnetic wave-shielding material simultaneously having high EMI-shielding property and high transparency in a fine line pattern and also enables mass production of such films at a low cost, and a light-transmitting electromagnetic wave-shielding film obtained by the production method and free from the problem of moire are provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method for producing an electromagnetic wave-shielding material which shields electromagnetic waves generated from front faces of displays such as CRT (cathode ray tube), PDP (plasma display panel), liquid crystal display, EL (electroluminescence) display and FED (field emission display), microwave oven, electronic equipment, printed wiring board and so forth and has transparency, and an electromagnetic wave-shielding material having transparency obtained by the production method.[0003]2. Description of the Background[0004]In recent years, electromagnetic interferences (EMI) have rapidly increased with the increase in utilization of various electric installations and electronics-applied equipments. It is pointed out that EMI not only causes malfunctions and damages to electronic or electric equipments, but also damages health of operators of these apparatuses. Therefore, it is required...

AI Technical Summary

Benefits of technology

[0024]The present invention has been achieved in view of the state of the art described above. An object of the present invention is to provide a method for producing an electromagnetic wave-shielding material simultaneously exhibiting high EMI-shielding property and high transparency and free from moire with easy formation of fine line pattern at a low cost in a large amount. Another object of the present invention is to provide a light-transmitting electromagnetic wave-shielding film obtained by the aforementioned production method.

[0025]The inventors of the present invention assiduously studied aiming at simultaneously obtaining high EMI-shielding property and high transparency. As a result, they found that the aforementioned objects could be effectively achieved by the following production method and light-transmitting electromagnetic wave-shielding film and thus accomplished the present invention.

Problems solved by technology

It is pointed out that EMI not only causes malfunctions and damages to electronic or electric equipments, but also damages health of operators of these apparatuses.

Therefore, all of the aforementioned methods were unsuitable as a method for shielding electromagnetic waves, since the aforementioned methods often provide opaque display front faces.

However, this shielding material has a drawback that it has a thick mesh line width, and therefore when a display screen is shielded with this shielding material, the screen becomes dark, and thus characters displayed on the display are hard to see.

However, the line width of the printed catalyst is as large as about 60 μm and is not suitable for use in a display that requires a relatively small line width and a precise pattern.

However, the visible light transmittance of the conductive film is 72%, which means insufficient transparency.

In addition, since extremely expensive palladium must be used as the electroless plating catalyst, most part of which is removed after the exposure, this method also suffers from a problem of production cost.

However, this method suffers from problems of the time-consuming and complicated production process and thus high production cost.

Moreover, it is known that this mesh has a problem that, since it is produced by etching, the width of the intersectional points in the grid pattern is thicker than that of the straight line portions.

However, any method has not been known at all for forming conductive metal silver by such methods to shield electromagnetic waves emitted from image display surfaces of displays including CRT, PDP etc. without inhibiting the image display.

Therefore, they suffer from a problem that opaque physical development nuclei remain in an exposed portion in which the metal silver is not formed, and thus light transmission is degraded.

The aforementioned problem is serious particularly in a case that the metal pattern material is used as a light-transmitting electromagnetic wave-shielding material for a display such as CRT and PDP.

Moreover, it is also difficult to obtain high conductivity by those methods, and attempts of obtaining a thick silver film for high conductivity should be accompanied by a problem of degradation of transparency.

Therefore, even if the aforementioned silver salt diffusion transfer process is used as it is, a light-transmitting electromagnetic wave-shielding material showing superior light transmission and conductivity and thus suitable for shielding electromagnetic waves from image display surfaces of electronic display equipments cannot be obtained.

Further, if the silver salt diffusion transfer process is not used, and conductivity is imparted by using a commercially available usual negative film through development, physical development and plating processes, obtainable conductivity and transparency are insufficient for use as a light-transmitting electromagnetic wave-shielding material for CRT or PDP.

As described above, any method has not been known at all for forming a conductive metal silver from a silver salt light-sensitive material as means for shielding electromagnetic waves emitted by electronic display equipments, and if the known silver salt diffusion transfer process is used as it is for electromagnetic wave shielding of displays, transparency and conductivity becomes insufficient.

As described above, conventional electromagnetic wave-shielding materials and methods for producing them each have problems.

However, when the aperture ratio (ratio of portions not having fine lines constituting a mesh with respect to the total area) is increased in order to improve the light transmittance, conductivity becomes lower, and thus electromagnetic wave-shielding effect is degraded.

Therefore, it has been extremely difficult to simultaneously improve conductivity (electromagnetic wave-shielding effect) and light transmittance with conventional techniques.

Moreover, since the material is installed on the front of the image display surface of a display, moire is generated, and it has constituted a problem.