JPS62122192A - Flexible circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to flexible circuit boards. In recent years, with the development of information devices, in order to facilitate human labor, a screen display system in which manual input is performed directly from the display 1-1 using a pen or fingertip has been introduced. has been done.

Unpublished 1!11 is intended to provide a flexible circuit board as a type of transparent conductive film.

(Prior Art and Problems) A flexible copper-clad laminate has a base material made of a plastic film such as Tingtong polyethylene terephthalate (PET) or polyimide, on which copper foil is laminated using an adhesive.

As the copper foil for g, a commercial copper foil or a rolled copper foil by a roll rolling method is used.゛When using copper foil, the surface is not smooth, so there is no problem with adhesion, so it is used as is without roughening it, but when a printed circuit is formed on it, it becomes transparent. Bad, ascending light transmittance is 40
There was a problem that only numbers less than % could be added.

First, rolled copper foil has a medium-smooth surface, so if the surface is used as a 4J single-layer board without phasing, it has poor adhesion and has not been put into practical use. In order to improve the properties, a material whose surface has been roughened and pressed (rough surface IBto or more) is usually used.

However, since such copper-clad laminates use copper foil whose surface has been treated with a double-sided surface, when the copper is removed by etching, the adhesive surface appears as a frosted glass-like translucent surface, and the parallel of the film base material The light transmittance is 20% or less. This is thought to be due to the fact that the copper foil has a high degree of roughness, so this rough surface is transferred as is.

As mentioned above, conventional copper-clad laminates had the problem of poor parallel light transmittance when printed circuits were formed.

(Structure of the Invention) The present invention provides a highly transparent flexible circuit board that can solve these problems. A printed circuit made of rolled copper foil with a surface roughness in the range of 5 to 5 is laminated and integrated through the agent, and the printed circuit area is 30% or less of the total area, and the parallel light transmittance is is 50% or more, and the total beam transmittance is 70% or more.

To explain this in detail, final perfect 1j is i'i
(A plastic film with visual light transmittance of 85% or more and sufficient flexibility as a flexible circuit board is used as a base material, and surface roughness (the true surface area Divided by area) is 5 to 5
Preferably, rolled copper foils having a diameter of 5 to 3 are laminated and integrated, and the plastic film is made of polycarbonate, polyether ether ketone, polyether sulfone, polyethylene terephthalate (CPET), etc., and is colorless and transparent. Among these, PE
T film is superior.

[-Although the film base material described above can be used as it is, it is preferable to activate its surface by subjecting it to low-temperature plasma treatment in advance in machine gas.This will provide strong adhesion to the rolled copper foil.

In this case, the film is held in a low-temperature plasma generation type that can be depressurized, and the film is heated between the electrodes at a temperature of, for example, 10 K while passing an inorganic gas under a low pressure of o, ot - to torr.
Hz - 100 MHz) by applying high J4 wave power. As the discharge frequency band, in addition to the above-mentioned high frequency, low frequency, microwave, and even direct current can be used.

The film substrate transparency is not affected by this treatment and has the same light transmittance as before treatment.

If the surface roughness of the rolled copper foil is 5 or more, the transparency of the film will be lost, and if it is less than 5, it will be difficult to form the foil.

The adhesive must be colorless, transparent, and thermosetting; for example, thermosetting acrylic resin, thermosetting polyester resin, etc. are suitable.

The flexible circuit board of the present invention is based on a flexible copper-clad board obtained by applying an adhesive to a film base material surface, drying it, laminating a rolled copper foil thereon, and integrating the rolled copper foil by pressing with a heating roll. A printed circuit is formed on copper foil using a photoresist method or a screen printing method. Note that the flexible circuit board of the present invention preferably uses a film that has been subjected to low-temperature plasma treatment in advance.

In order to achieve the purpose of the present invention, it is necessary that the copper area of the printed circuit is 30% or less of the total area, and that the parallel light transmittance is 50% or more and the l-1 total light transmittance is 70% or more. When the flexible circuit board of the present invention is applied to a display etc., transparency will be impaired if the line width is large.
To ensure high light transmittance, the line gap is 2 times the copper line width.
It is preferable that it is twice or more, and the line gap is 1000g
m or less is preferable.

Examples of the present invention will be given below.

Example PET film with a thickness of 100 gm (Lumirror T manufactured by Toshi)
15g of polyester thermosetting adhesive when dry
After coating and drying to a thickness of 1.5 m, a 35 m thick rolled copper foil (surface roughness 3) was continuously laminated and rolled up using a heated roll at 120°C to produce a copper foil-polyester laminated film. did.

By printing a circuit on this laminated film L using a conventional method and etching it, a line width of 50 lm was achieved! a interval 50
A copper circuit area of 17% was formed to form a circuit of 0 pm and its transparency was measured. The results were as follows.

Total light transmittance 85%, parallel light transmittance 65% Comparative Example The procedure was carried out in the same manner as in the example except that an 18 pm thick electrolytic copper foil (surface phase degree of about 10) was used instead of the rolled copper foil in the example. A copper foil-polyester laminate film was obtained. A circuit is printed on the copper foil of this laminated film, and etched to form a circuit with a line width of 50 pm and a line gap of 500 pm (copper circuit surface a1
7%). When the transmittance of this material was measured, the total light transmittance was about 85% and the parallel light transmission rate was 40%.

Claims (1)

[Claims] 1. A surface roughness of 1 is applied to a transparent film base material via an adhesive.
．． Printed circuits of rolled copper foil within the range of 5 to 5 are laminated and integrated, the printed circuit area is 30% or less of the total area, and the parallel light transmittance is 50% or more, and the total light transmittance 70% or more. 2. The copper line width of the printed circuit is 100 μm or less, and the line spacing is 10
The flexible circuit board according to claim 1, which has a thickness of 00 μm or less.