KR20020007835A - Cleaning solution for antireflection/antistatic coatings on braun tubes - Google Patents

Abstract

PURPOSE: A solution of a cathode-ray tube for shielding an electromagnetic wave and removing a low reflective coating film is provided to enable a liquid remover to be used in place of an ineffective CeO2 sludge, improve work efficiency, reduce a defect ratio, and decrease a possibility of corroding a reinforcing band. CONSTITUTION: A solution for shielding an electromagnetic wave and removing a low reflective coating film is coated on a front surface of a TV's cathode-ray tube(CRT). The coating film remover serves to prevent an aluminum reinforcing band of the cathode-ray tube from being corroded, shield an electromagnetic wave of the TV's cathode-ray tube in a short time, and remove a low reflective coating film. To do that, ions are removed from water. pH of the water ranges from 2.0 to 6.0 at a temperature of 25°C. 0.05 to 2 weight % of hydrofluoric acid, fluoride salt, or Zn2+ or Mg2+ of salt are contained in the water from which the ions are removed. The fluoride salt is NH4F. The coating film remover is manufactured by using NH4F at 1.0 to 10.0 weight % relative to an overall remover.

Description

Electromagnetic shielding and low reflection coating film removal solution of CRT tube {cleaning solution for antireflection / antistatic coatings on braun tubes}

The present invention relates to a composition for removing the electromagnetic shielding and low reflection coating film applied to the front surface of a TV CRT, and more particularly, in an acidic liquid form in which an electrolyte and hydrofluoric acid, ammonium fluoride or fluoride are added to the deionized water. The removal liquid which removes an electromagnetic shielding and / or a low reflection coating film.

The TV CRT emits harmful electromagnetic waves to the human body and has a problem in that dusts easily adhere to the surroundings due to the charging phenomenon. In addition, the background in front of the screen is reflected on the screen may overlap with the image from the TV may not be clearly visible. These problems of TV CRTs have been solved by applying a low reflection coating to shield electromagnetic waves on CRTs.

Electromagnetic waves are mainly coated with nanometer-sized conductor particles such as In ₂ O₃ / SnO₂ (ITO), Sb ₂ O₃ / SnO₂ (ATO), carbon black and Ag / Pd on the front of the CRT to form a transparent and conductive layer. It is shielded by the method of forming. Since the conductive particles are not adhesive, the conductive particles are coated together with SiO ₂ to stably place the conductive particles on a glass substrate. In addition to these functions, SiO₂polymers lower the reflectivity. Depending on the coating method, the conductive particles and SiO₂polymers are coated with two, three, or four layers, and the multilayer reflects a wider wavelength range with low reflectance. SiO 2 polymers undergo a firing process to form a very hard layer of glass.

In the electromagnetic shielding and low reflection coating process of the front surface of the CRT, various defects may appear as follows. First, foreign matter spots are formed on the CRT coating film by foreign matter in the workplace. These spots distort the image of the CRT. Second, when the spin coating process conditions such as rotation speed or CRT preheating temperature are not appropriate in the spin coating process, line smears or color smudges spread outwards. Third, various kinds of spots, color spots, and line spots appear when the drying time or viscosity of the coating solution is not appropriate.

The coating process is at the end of the whole CRT production process, and since the state before coating is almost a finished product, when such defects appear, there is a problem of reprocessing and reusing.

In order to solve this problem, the present work site is mixing CeO2 powder with pure water to form a slurry and polishing the surface of the CRT to remove the coating film. In this case, a skilled engineer takes 10-15 minutes per panel to remove the outermost layer of glassy, hard SiO2 polymer, and it is difficult to make a continuous work process.

In addition, the CeO ₂ particles in the air blow like dust, the work environment worsens, and these particles settle on the surface of the CRT, causing a lot of spots caused by foreign substances when recoating.

In order to solve this problem, the necessity of the liquid coating removal solution has emerged. However, the results of the study on the removal of electromagnetic shielding and the low reflection coating on the surface of the CRT have been insufficient, and the concentration of hydrofluoric acid that is harmful to the human body is more than 10%. Providing high concentrations of liquids inhibits the environmental stability of the work process.

US Patent No. 5,011,443 proposes a method of spraying an abrasive such as CeO2 in the form of a gas, and Korean Patent Publication No. 95-15071 discloses a solution for diluting hydrofluoric acid with pure water and a process thereof. Korean Patent Application No. 96-54311 discloses a method for recycling a coating removal liquid of a hydrofluoric acid component, and WO 98-31768 discloses a fluorine ion as a coating removal liquid or a front surface cleaning liquid in an overall display device. , Liquids using phosphoric acid, acetic acid and inhibitors, surfactants and the like are disclosed.

The inventions using hydrofluoric acid in the above patents disclose solutions in which only hydrofluoric acid is diluted in pure water and WO 98-31768 describes the use of salts containing fluorine.

The hydrofluoric acid component has been used so far for etching glass or cleaning or polishing a silicon based surface.

In this example, first, when used to etch the CRT panel itself made of glass, it was used when the CRT panel was subjected to irregularities with a hydrofluoric acid-based cleaner by a low reflection treatment method on the glass surface. Korean Patent Publication No. 90-4123 discloses a method of low reflection treatment by etching a glass surface using 30 to 60 parts by weight of HF, 0 to 30 parts by weight of H ₂ SO₄0 to 30 parts by weight, and 40 to 65 parts by weight of H ₂ O + glycerin. Korean Unexamined Patent Publication No. 89-1896 discloses a glass surface low reflection treatment method. In Korean Patent Publication No. 88-1254, HF 15 to 20% by weight, HBF '3 to 5% by weight, H ₂ SO'60 to 68% by weight, NH ₄ F 1 to 3% by weight, C ₃ H ₈ O 0.1 to 1.0 A method of low reflection treatment is disclosed by etching a glass surface at a ratio of weight percent, C ₆ H ₁₄ O 1 to 2 weight percent and H ₂ O 7 to 8 weight percent.

The amount of hydrofluoric acid used in this method is still high because it is high concentration of more than 10% by weight and its use is used only for low reflection treatment through the unevenness of the CRT panel itself.

Second, hydrofluoric acid is used to clean various types of glass without any flaws and impurities. US Pat. No. 4,332,649 discloses a method for removing impurities from the glass surface and wiping the surface evenly using 52 to 63% by weight sulfuric acid and 3 to 10% hydrofluoric acid. US Pat. No. 4,555,304 also discloses the same. Doing.

Third, a hydrofluoric acid component is used for the method of removing the polysilicon film of a semiconductor device. In Korean Patent Publication No. 94-1528, CrO ₃ , HF, NH ₄ OH, and H ₂ O were used as etching solutions used to measure reliability in a wafer during fabrication of a semiconductor device. Korean Patent Publication No. 95-34556 discloses the removal of a polysilicon film on a semiconductor substrate using other acids such as HF and HNO 3. As a method of etching a semiconductor device, Korean Laid-Open Patent Publication No. 97-8397 discloses a semiconductor etching solution using ammonium fluoride and hydrogen peroxide hydrofluoric acid as pure water.

As described above, studies on removing polysilicon films using hydrofluoric acid have been conducted. However, studies on removing electromagnetic wave shielding and low reflection coating films of CRTs are insignificant, and excessive amounts of hydrofluoric acid are included to make the work environment worse. There is a problem.

In order to solve the problems as described above, an object of the present invention is to provide a liquid-type removal liquid that can replace the existing inefficient CeO 2 sludge in removing the electromagnetic shielding, low reflection coating film of the TV CRT.

Another object of the present invention is to reduce the defects caused by foreign material spots during recoating when using the slurry, to increase the efficiency of the workplace and to improve the working environment.

Still another object of the present invention is to reduce the harmful hydrofluoric acid component of the coating removal liquid to within 2% by weight, and to reduce the side effects of corrosion of the reinforcing band on the side of the CRT in addition to removing the coating film.

The present invention provides a coating film removal liquid comprising a) 0.05 to 2% by weight of hydrofluoric acid, b) a fluorinated salt and c) a salt of Zn ²⁺ or Mg ²⁺ in order to achieve the object as described above. .

The coating film removal solution is preferably pH of 2.0 to 6.0 at 25 so as to remove the electromagnetic shielding, low reflection coating film of the TV brown tube in a short time without corroding the aluminum reinforcing band of the CRT.

The hydrofluoric acid is preferably used within 0.05 to 2.0% by weight based on the total coating film removal liquid, and when the amount of acid is used at 0.05% by weight or less, the washing power is deteriorated due to the lack of H ⁺ ions, and the cleaning power is used when the amount is more than 2% by weight. Is slightly improved, but the corrosion of the reinforcing band on the side of the CRT becomes worse, and the excessive amount of hydrofluoric acid that is harmful to the human body is used, which is not preferable.

In addition, the pH of the coating film removal liquid can be adjusted to the desired conditions during the operation by adjusting the relative ratio of the acid amount and the fluorine salt, the cleaning power of the removal liquid by adjusting the pH and the concentration of the total fluorine salt, and also in the appropriate conditions during the operation I can regulate it.

It is proposed that a SiO2 polymer, a coating film, is decomposed by the following mechanisms by H ⁺ and F ^- ions in hydrofluoric acid.

Scheme

The rate at which SiO 2 polymers decompose depends on the pH of the liquid and the concentration of F ⁻ ions. The SiO 2 polymer film tends to be removed as the pH is lower and as the total amount of F ^- ions increases. However, the metal of the cathode-ray tube side, to lower the pH as shown in the reaction scheme ^F-there is a need to control the amount of ^properly-the more the content of ions, so a lot of corrosion and pH F.

2H ⁺ + Fe → Fe ²⁺ + H₂

In the present invention, the pH of the removal solution can be adjusted in various ways by relatively adjusting the amount of HF and NH ₄ F, when a pair of bases of HF such as NH ₄ F is provided, only a constant pH can be obtained by adjusting the amount of HF. Therefore, it is possible to obtain a desired pH value by relatively adjusting the amount of NH ₄ F.

When the molar ratio of HF / NH ₄ F is 1: 1, the pH is about 4, and when the molar ratio is 1: 4, it is about 5.

Therefore, in the present invention, the pH is adjusted to 2.0 to 6.0, using HF within 0.5 to 2% by weight to provide a coating film removal liquid that can remove the coating film within 50 seconds.

On the other hand, NH ₄ F is used as the fluorinated salt of b). In order to maintain a constant rate of removal of the SiO 2 polymer film, since the pH must be kept constant during the decomposition of the SiO 2 polymer, in the present invention, NH ₄ F containing a pair of F ^- ions, which is a base of hydrofluoric acid, is used to maintain a constant pH. A buffer effect was obtained by adding. In addition, NH ₄ F also serves to supply F ⁻ ions which continue to decrease during the reaction.

The NH ₄ F is preferably used in an amount of 1.0 to 10.0% by weight based on the total removal liquid, and when used in an amount of 1.0% by weight or less, the fluorine ions continue to decrease during the removal of the coating layer, thereby significantly reducing the cleaning power during wiping. Not desirable In addition, the use of more than 10% by weight of fluorine salts will remain when the CRT panel wiped with water is removed, and NH ₃ and HF from NH ₄ F decomposed at high temperature will damage the CRT panel. not.

In the case of using fluorine salts such as KF or NaF in addition to NH ₄ F, K ₂ SiF ₆ or Na ₂ SiF ₆ which is insoluble in water is formed by combining with SiF ₆ ^2- , a monomeric form of SiO 2 polymer, formed during the coating film removal process. This has the disadvantage of sticking to the CRT panel again. Fluoride salts such as ZnF ₂ and MgF ₂ are not preferred because they are insoluble in water and are not suitable for use.

When the total amount of F ^- ions is 0.3 M by adding the amount of HF and NH ₄ F, the pH shows good cleaning power at 2 or less, and the pH is 4 or less at 0.5 M, and the pH is 5 or less at 0.7 M. , 0.1 M shows good washing power at pH 6 or less.

In the present invention, the electrolyte is added to increase the rate of decomposition of the SiO 2 polymer. The present inventors found that the effect of removing the coating film varies greatly depending on the kind of salt of the electrolyte, and found that the addition of a salt containing Zn ²⁺ and Mg ²⁺ shows the best effect among many salts.

^Electrolytic salts containing Zn ²⁺ or Mg ²⁺ salts have the effect of improving the washing power and at the same time eliminating salts precipitated during washing.

Salts of Mg ²⁺ include, for example, Mg (NO 3) 2, MgSO 2, and MgCl 2. Zn ²⁺ salts include Zn (NO 3) 2, ZnSO 2, and ZnCl 2.

In the present invention, it is preferable to use 0.05 to 5% by weight of Zn ²⁺ or Mg ²⁺ as the electrolyte salt. Zn ²⁺ or Mg ²⁺ and 0.05 The use of a% by weight or less is not preferred because the washing off of the coating remover, In case of using more than 5% by weight of F in solution ^- in combination with the ion precipitate, forming a ZnF₂ or MgF₂ This is undesirable because it sinks to the bottom of the solution.

When KNO₃ or NaNO₃ other than these Zn ²⁺ or Mg ²⁺ ions are used, salts that do not dissolve in water such as K₂SiF ₆ or Na₂SiF ₆ are formed and reattach to the CRT panels. It is undesirable because it is formed.

A cation which combines with SiF ₆ ^2- which is formed during the reaction to form a soluble salt in water is, but this addition is Pb ²⁺ Pb ²⁺ is not preferred for use because harmful to the human body.

When the amount of the salt containing Zn ²⁺ or Mg ²⁺ is used in an amount of 0.01 M or more, MgF ₂ and ZnF ₂ do not dissolve, and there is a side effect of forming a solid.

In addition, the inventors have found that the use of surfactants has the effect of reducing metal corrosion of brown and side surfaces.

In the present invention, an anionic surfactant such as sodium dodecyl sulfate (SDS) and sodium dodecyl benzyl sulfate (SDBS) may be further included in the coating film removal solution, including an amount of critical micelle concentration (CMC).

In the case of SDS, using 0.01 to 0.3% by weight or SDBS in the case of 0.01 to 0.07% by weight or more is not preferable because the foaming.

The effect of the surfactant is not preferable because the degree of corrosion is already low enough when the pH of the removal liquid before the addition of the surfactant is 4 or more, but when the pH is 4 or less, the effect of reducing the degree of corrosion on the side of the CRT tube appears. Therefore, it is preferable.

Hereinafter, preferred examples and comparative examples are presented to aid in understanding the present invention. However, the following examples are only presented to more easily understand the present invention, and the present invention is not limited to the following examples.

Example 1

The removal solution was prepared by changing the pH of the coating solution removal solution to the components shown in Table 1 below.

Table 1

Removal liquid HF Mg (NO₃) ₂ NH₄F (1-a) 0.48 0.10 0.48 (1-b) 0.60 0.10 0.36 (1-c) 0.20 0.10 0.76 (1-d) 0.11 0.10 0.85 (1-e) 0.03 0.10 0.93

Example 2

The removal solution was prepared using the components shown in Table 2 below so as to check the washing power corrosion resistance while changing the total amount of fluorine ions in the solution.

TABLE 2

(Unit: M)

Removal liquid HF Mg (NO₃) ₂ NH₄F (2-a) 0.35 0.10 0.35 (2-b) 0.15 0.10 0.15 (2-c) 0.08 0.10 0.64 (2-d) 0.07 0.10 0.48 (2-e) 0.06 0.10 0.48 (2-f) 0.05 0.10 0.40

Example 3

Using SDS as a surfactant, a coating film removal solution was prepared using the ingredients shown in Table 3 below.

TABLE 3

(Unit: M)

Removal liquid HF Mg (NO₃) ₂ SDS (3-a) 0.72 0.01 0.01 (3-b) 0.48 0.01 0.01 (3-c) 0.60 0.01 0.01

Comparative Example 1

In Example 1, except for Mg (NO₃) ₂ and NH 에서 F, a coating film removal solution was prepared.

Comparative Example 2

In Example 1 KF was used instead of NH₄F to prepare a coating film removal solution.

The coating film removal solutions prepared in Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 4 by measuring the physical properties and cleaning power and the metal corrosion of the side of the CRT in the following manner.

Table 4

[F￣] total pH Cleaning power Band Corrosion Degree Example 1-a 0.96M 4.4 15 seconds 25 sec 1-b 0.96M 3.4 12 seconds 17 seconds 1-c 0.96M 5.5 20 seconds 90 sec 1-d 0.96M 5.8 20 seconds 120 seconds 2-a 0.96M 6.5 Inner wipe > 4 minutes 2-b 0.70M 4.4 15 seconds 30 seconds 2-c 0.30M 4.4 Inner wipe 40 seconds 2-d 0.72M 5.8 45 seconds > 1 minute 2-e 0.63M 5.8 60 seconds > 1 minute 2-f 0.54M 5.8 Inner wipe > 1 minute 3-a 0.45M 5.8 Inner wipe > 1 minute 3-b 0.72M 2.8 12 seconds 40 seconds 3-c 0.96M 4.3 12 seconds 40 seconds 3-d 0.82M 3.4 12 seconds 40 seconds Comparative Example 1 0.96M 3.3 30 seconds 17 seconds Comparative Example 2 0.96M 4.4 Inner wipe

The measurement method of the physical properties and the cleaning power and corrosion in the experiment is as follows.

(1) cleaning power

The time taken to wipe off 20 ml of ATO / carbon black / SiO2 polymer film coated with a single layer on a 29 inch LG Platon Brown tube panel was wiped with a cloth.

(2) CRT side metal corrosion

When the metal on the side of the CRT was immersed in the washing solution prepared by the method (1) for 1 minute, the time taken for hydrogen gas to occur was measured.

(3) pH

It was measured at 25 ° C. using a pH meter.

The electromagnetic wave shielding and total reflection coating film removal liquid of the TV CRT of the present invention replaces the conventional coating removal method using the CeO₂ powder with the liquid coating removal solution and solves the problems caused by the inefficiency of the conventional operation and the foreign matter during recoating, and the hydrofluoric acid. By using less ingredients, the electromagnetic shielding and low reflection coating on the front side of the CRT can be easily removed and the corrosion of the metal on the side of the CRT can be reduced without harming the workers' working environment.

In addition, the coating film removal solution of the present invention can be used to remove all kinds of electromagnetic shielding and low reflection coating film using SiO2 polymer as a binder regardless of the size of the CRT panel, the type of conductor of the electromagnetic shielding coating film, and the coating method. have.

Claims (8)

a) 0.05-2% by weight of hydrofluoric acid; b) fluorine; And c) salts of Zn ²⁺ or Mg ²⁺ Coating film removal liquid comprising a. The method of claim 1, The coating film removal liquid having a pH of 2 to 6 of the removal liquid. The method of claim 1, A coating film removal liquid, wherein the fluorinated salt of b) is NH₄F. The method of claim 3, wherein The coating film removal solution prepared by using the NH ₄F 1.0 to 10.0% by weight based on the total removal solution. The method of claim 1, The electrolytic salt of Mg ²⁺ of c) is a salt selected from the group consisting of Mg (NO₃) ₂, MgSO₄ and MgCl₂, and the salt of Zn ²⁺ is a salt selected from the group consisting of Zn (NO₃) ₂, ZnSO₄ and ZnCl₂. Coating film removal solution. The method according to any one of claims 1 to 5, Coating film removal solution prepared using 0.05 to 5% by weight of the salt of Mg ²⁺ or Zn ²⁺ . The method of claim 1, Coating membrane removal liquid further comprising an anionic surfactant in the coating membrane removal liquid. The method of claim 7, wherein As the anionic surfactant, SDS (Sodium Dodecyl Sulfate) is 0.01 to 0.3% by weight, SDBS (Sodium Dodecyl Benzyl Sulfate) is a coating film removal solution prepared using 0.01 to 0.07% by weight.