JPS5877598A - Etching method for transparent conductive film - Google Patents

Abstract

PURPOSE:To permit etching at a constant speed in a titled method having a Cr<2+>/Cr<3+> redox system in a diaphragm separated electrolytic cell by adding an electrode pair for recovering of metals from metallic ions that decrease the etching rate. CONSTITUTION:The Cr<2+>/Cr<3+> redox system dissolved in mineral acids exist in a cathode compartment 1 separating an electrolytic cell by a diaphragm 3. Voltage is applied between electrodes 4 and 5 in such a way that the potential of the electrode 4 attains <=-0.3V (US.RHE) whereby a tin oxide transparent conductive film is etched. Metallic ions (impurities) of Sn, etc. increase gradually in an etching soln. and when the concn. thereof exceeds a certain value, the etching speed decreases considerably. Thereupon a pair of sub electrodes 6, 7 are provided in the compartment 1 and are maintained under weak current of 0.1- 5A/dm<2>. Thus the above-mentioned impurities are removed and semipermanent etching is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of etching a transparent conductive film, and particularly to an etching method that can be used semi-permanently even in mass production.

Transparent conductive films are widely used in displays such as liquid crystal display panels, and most of them are used with some kind of patterning. Although this patterning accuracy, yield, etc. greatly influence the specifications and costs of products using these, M9″Δ is not blind.

Commonly used transparent conductive films include indium oxide and tin oxide. The former is expensive and has inferior electrochemical stability to the latter. The latter is inexpensive, but has the disadvantage that patterning is difficult. Z11 powder/HCl method has long been used for the latter type of patterning, or etching, but it is difficult to control the reaction speed, and there are problems such as the resist peeling off due to physical contact, so it is not suitable for fine patterning in recent years. I can't do it anymore. On the other hand, immersion etching technology using Cr2°l/Cr3+ redox system is N S Pat40
09061, this method causes severe deterioration of the etching solution and is not practical at all. Therefore, the present inventor previously investigated a method of separating the Or2+/Cr3'' redox system using electrolytic heating and causing the reaction from Cr3+ to Cr2+ to occur under electrolysis. It was found that the etching speed gradually deteriorated due to the above etching.The results of the etching liquid analysis showed that Sn of q43.1? Originally, it should be deposited as metal tin on the electrode in the cathode compartment where Cr3'' → Cr2+ is carried out, but because the current density was too high, it formed as electrolytic powder and was missing from the electrode. Not collected. On the other hand, if the current density is lowered, Cr
The efficiency of 3+→Or2+ decreases and the etching speed cannot be kept constant. The present invention is intended to solve such drawbacks, and in addition to the high current density electrode pair that promotes Or → Cr2+, it also removes various metals such as tin ions, iron ions, nickel ions, copper ions, etc. that cause a decrease in etching speed. The present invention will be described below with reference to the drawings, which is characterized in that it is equipped with a pair of electrodes for recovery at a lower ηL flow density. FIG. 1 is a sectional view of the basic etching bath of the present invention.

3 is 1♀AliI'a which separates the cathode compartment 1 and the anode compartment 2, and is unglazed,
Ion exchange 11! ``G + Teflon filter, etc. In the cathode compartment <jh: c
There is an Or 2+/Or 3+ redox system dissolved during the reaction. Examples of mineral acids include hydrochloric acid, 9-sulfuric acid, nitric acid, phosphoric acid, 9-hydrofluoric acid, hydroiodic acid, and hydrobromic acid, which may be used alone or in combination of any of these. The concentration is 0. I N or higher is usually used.

Among these acids, hydrohalic acids such as hydrochloric acid and aqueous bromide have particularly excellent etching properties. Or2″゛／O
r redox threads are Or O/-3 to these mineral acids.
By dissolving a chromium salt such as -6H20,0r2(SO4)3 or metallic chromium, and applying a voltage of 1030cm (υ5-RHE) between electrodes 4 and 5, 71.
Led. This 'gaze point difference center J potentiostat may be used, or direct current electric currents i1', j may be used. In this way, a transparent conductive +
! The transparent conductive layer can be easily etched by dipping A. As for the electrode No. 4, the one with a larger hydrogen overvoltage has a better j purchasing efficiency of Or"+ → Or2+. Carbon, P b , Fe , Sn , Hg
, Hg, ama-fiv gum, stainless steel, etc. are good, but inexpensive carbon and Pb are particularly good. 5 is insoluble 1
One electrode is best made of carbon, Pt, Rh, Ti-Pt,
Ti-Rh.

T i Rh O, T i Ru O'4 are good.

Figure 21 shows electric 4i1ii 5 and carbon arashi mochi to electric 24
to PbηL and to cathode compartment 1.
OL, ・6 H2O at 100 r/l, 6N hydrochloric acid, bisque fired separator for 5 A, / tbl for 5 hours. Shows the liquid temperature and etching speed when the electrolytic etching speed reaches a steady state. . Note that the transparent conductive film is made of tin oxide. Approximately 20,000 such etchings (
1ootα20o++X500A) If the process continues, the steady state etching speed will drop to about half. As a result of liquid analysis, it was found that etched tin ions were responsible for preventing damage. When the tin ion concentration exceeds 0.1ii'/A, a significant decrease occurs. Originally, tin ions should be attached to the electrode 4 as metal tin, but 5
At temperatures above 0°C, tlj arrival hardly occurs in No. J. This is because the current density is too high and it falls off from the electrode as 'rat iW powder, or carbon, PI
) etc., it is thought that it is missing due to poor adhesion. Therefore, the present inventor used 697 sub-electrode pairs, and used 697 sub-electrode pairs. By removing impurities (metal ions that adversely affect the etching speed) in Step 1, he was able to invent a permanent etching method that could produce 50,000 to 100,000 sheets. The electrode used in 6 is free of these impurities.
i-! When wearing L, one with good adhesion was selected, P t ,
A u, L(ll.

A plate or mesh made of Pb or the like is preferable, and 7 may be any insoluble electrode and may be made of the same material as 5. The DC' electric field applied between 6 and 7 is preferably 0.1 A to 5 A/drJ, and more preferably 12 A to 2 A/tU.

If the current density is too low, electrodeposition will not be possible, and if the current density is too high, the adhesion will be poor and the effect will be lost. Or2+10r like this
The system for keeping the redox system stable does not necessarily have to be used as an etching tank. There is no problem even if the solution in tank 1 is introduced into a separate tank and etching is performed in that tank. However, the system of the present invention is indispensable when this type of etching is carried out industrially.

[Brief explanation of the drawing]

Fig. 1...Cross-sectional view of the etching bath of the present invention.Second sectional view
Figure: Temperature-etching speed relationship in the embodiments of the present invention Applicant: K W'J Seikosha Co., Ltd.

Claims (1)

[Claims] Cr2+/Cr3+ redox threads formed in a mineral acid are electrolytically maintained in the cathode compartment of a 'gL decomposition tank at a cathode potential of -0, 3 V (Us -R) (E) or less. In the method of etching a transparent conductive film, in addition to a pair of electrodes that hold the redox system,
A method for etching a transparent conductive film, characterized in that a pair of electrodes is further provided and the film is maintained under weak electrolysis of 0.1 A to 5 vdΔ.