JPH07155713A - Cleaning method of fluorescent screen of cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a cleaning method of fluorescent screen of a cathode-ray tube enabling to clean and regenerate a panel inside surface inexpensively, capable of sufficiently cleaning even without using an aqueous hydrofluoric acid and not damaging the panel inside surface. CONSTITUTION:By this cleaning method, the fluorescent screen 3 formed by sticking fluorescent materials 3R, 3G, 3B and a graphite 3C on the glass panel inside surface 2a of the Braun tube 1 is cleaned. The fluorescent screen 3 is dipped into a cleaning liquid being an aqueous solution of an oxidizing agent and is applied with ultrasonic vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a fluorescent screen of a cathode ray tube.

[0002]

2. Description of the Related Art As shown in FIGS. 3 and 4, a cathode ray tube 1 for displaying an image on a television or the like includes a panel 2 and a funnel 4.
An image is obtained by causing the fluorescent substance to emit light while scanning the fluorescent screen 3 formed on the inner surface 2a of the panel with an electron beam. As shown in FIG. 5, the phosphor screen 3 of the color cathode-ray tube 1 is composed of the phosphor 3
It is formed of R, 3G, 3B and graphite 3C. That is, phosphors 3R, 3G, and 3B of three colors of red, green, and blue are adhered to the inner surface 2a of the glass panel in a predetermined stripe-shaped or dot-shaped pattern. It is filled with graphite 3C in black to form a so-called black matrix.

In the manufacture of the cathode ray tube 1, the panel 2 which has conventionally been defective during the formation of the fluorescent surface 3 on the inner surface 2a of the panel has the phosphors 3R, 3G, 3 attached once.
By washing B and graphite 3C, the panel inner surface 2a is regenerated, and the fluorescent surface 3 is formed again. The cleaning in this case needs to avoid physical impact on the panel in order to maintain the smoothness of the glass surface. Therefore, cleaning is performed by showering a solution of hydrogen fluoride, which is a strong oxidant, and a nitric acid solution. Particularly, the hydrogen fluoride solution is necessary for cleaning the graphite 3C, which is difficult to remove.

[0004]

However, since the above-mentioned cleaning step requires about 30 minutes to 1 hour, the amount of cleaning per day is limited, and a highly efficient cleaning method has been desired. Further, since hydrogen fluoride corrodes the glass surface to remove the graphite 3C, the phosphors 3R, 3G, 3B to which the graphite 3C is not attached.
At the portion, the panel inner surface 2a is attacked. As a result, unevenness may be formed on the inner surface 2a of the panel, and the phosphor screen 3 may not be re-formed, resulting in a non-reproducible product. Moreover, the hydrogen fluoride solution used needs to be drained after being subjected to a special treatment, which is also inconvenient in terms of waste liquid treatment cost. Further, the hydrogen fluoride solution has an irritating odor and is extremely toxic, and when it comes into contact with the skin, the contact portion is significantly damaged. Therefore, handling such a hydrogen fluoride solution is undesired in terms of safety in the working environment.

Therefore, in order to solve the above-mentioned conventional problems, the present invention can clean and regenerate the inner surface of the panel at low cost, and can sufficiently clean the surface without using a hydrogen fluoride solution. An object of the present invention is to provide a method for cleaning a fluorescent screen of a cathode ray tube that does not damage the inner surface of the panel.

[0006]

As a means for solving the above problems, the present inventor is a method of washing and removing a phosphor screen formed by adhering a phosphor and graphite on the inner surface of a glass panel of a cathode ray tube. Then, a method for cleaning a fluorescent screen of a cathode ray tube was created, in which the fluorescent screen is immersed in a cleaning solution which is an aqueous solution of an oxidant, and ultrasonic vibration is radiated to the fluorescent screen in the cleaning solution. Further, a method for cleaning the fluorescent surface of a cathode ray tube was created, wherein the cleaning solution is an aqueous solution of potassium permanganate and sodium hydroxide.

As the oxidant, a usual oxidant can be used, but it is desirable to use an oxidant having a strong oxidizing power. For example, potassium permanganate, potassium dichromate, hydrogen peroxide, etc. can be mentioned. Also,
When using an oxidizing agent, an appropriate liquidity (pH) can be selected according to the kind of the oxidizing agent. For example, when using potassium permanganate under alkaline,
50-250 g / L of potassium permanganate and 50-150 g / L of sodium hydroxide are desirable, but potassium permanganate can be used under acidic conditions such as sulfuric acid and under neutral conditions. Further, hydrogen peroxide under acidic conditions of oxalic acid and potassium dichromate under acidic conditions of sulfuric acid can also be used.

The frequency of the ultrasonic waves used can be appropriately selected. Further, in order to uniformly obtain the cleaning effect due to the occurrence of cavitation on the cleaning surface, the pitch of cavitation can be made fine by using a plurality of frequencies.

After the washing with the oxidizing agent, the graphite and the oxidizing agent which have been treated with the oxidizing agent are removed with water or an appropriate rinse solution. For example, in the case of treating with an oxidizing agent under alkaline conditions, an acidic rinse solution (hydrochloric acid, nitric acid, etc.) or a washing agent suitable for washing the oxidizing agent is selected. The phosphor forming the phosphor screen is easily removed by washing with water. An oil-based base material is applied to the portion of the panel on which the fluorescent screen is formed that is joined to the funnel, but it is necessary to simultaneously clean the oil-based base material when cleaning the fluorescent screen. For this purpose, cleaning with, for example, 8 to 22% nitric acid is performed. Furthermore, in order to eliminate fine deposits on the inner surface of the panel,
To finish the cleaning, cleaning with pure water (ion-exchanged water) or ultrapure water is effective. This prevents dust from adhering and prevents the ionic substance dissolved in water from remaining as spots on the glass surface after drying.

[0010]

According to the above structure, graphite is removed from the inner surface of the glass panel by the oxidizing action of the oxidizing agent and the generation of cavitation due to the emission of ultrasonic waves.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to FIGS. The present invention is not limited to this embodiment. FIG. 1 is a process diagram showing the entire cleaning process of the fluorescent screen of the cathode ray tube. As shown in FIGS. 3 and 4, the panel 2 of the cathode ray tube 1, which is the object to be cleaned in the main cleaning step, is a glass panel having a gently curved surface similar to the conventional one. The phosphor 3R, 3G, 3B and the graphite 3C are attached in a mosaic pattern on the inner surface (inside the curved surface) 2a to form the phosphor surface 3.

Although not shown, the ultrasonic cleaning apparatus used in the main cleaning step is mainly composed of 11 cleaning tanks, an ultrasonic oscillator, and a cleaning material transfer device. Each washing tank 8
Are arranged in a predetermined order so that the panel 2 attached to the carrier can be taken in and out from above,
The panel 2 is designed to be cleaned in the cleaning tank 8 in order by the transfer device. As shown in FIG. 2, each cleaning tank 8 can store about 10 panels 2 in a standing state.
It has a volume of 0 L and is filled with a predetermined amount such that a predetermined cleaning liquid according to each process can immerse the entire panel 2. Further, an ultrasonic transducer 10 connected to an ultrasonic oscillator is attached to the side surface of the cleaning tank 8. As a result, ultrasonic vibrations are radiated from one side surface portion to the other side surface portion in the cleaning liquid filled in the cleaning tank 8. The frequency of the ultrasonic waves used is 24k
There are two types, Hz and 45 kHz.

As the cleaning liquid, tap water, an alkaline sodium hydroxide solution of potassium permanganate, 10% nitric acid,
And use pure water. Sodium hydroxide alkaline solution of potassium permanganate is 150 g of kalim permanganate.
Dissolve 150g of sodium hydroxide in tap water and 1L
Prepare as.

Next, the process of cleaning the panel 2 will be described with reference to FIG. First, the panel 2 is attached to the carrying device and set at the start position of the process. When the cleaning process is started, the panel 2 is the first cleaning tank ((I) in FIG. 1).
It is immersed in standing water in tap water at room temperature,
Ultrasonic vibration is radiated from 0 to tap water in its phosphor screen 3 for 1 minute. As shown in FIG. 2, the ultrasonic vibration is radiated directly to the phosphor screen 3, and cavitation is generated on the surface of the phosphor screen 3, so that the phosphor 3R that forms the phosphor screen 3 by its destructive force or dispersion action. , 3G, 3B and graphite 3C weaken the binding force to the glass inner surface 2a. The phosphors 3R, 3G, 3B are almost removed in this washing process.

In the second step ((II) in FIG. 1), the panel 2 is immersed in the alkaline solution of potassium permanganate heated in the second tank at 55 to 60 ° C. and ultrasonically vibrated. 1
The light is emitted toward the phosphor screen 3 for a minute. In the presence of the oxidant and the cavity due to ultrasonic vibration, the bond of the graphite 3C on the inner surface 2a of the panel is weakened, and the graphite 3C is peeled off by the action of the oxidant.

On the panel 2 pulled up from the second tank,
In the third tank ((III) in FIG. 1), ultrasonic vibrations are radiated to the fluorescent surface 3 in tap water at room temperature, and the exfoliated and decomposed products of the graphite 3C adhering to the panel inner surface 2a are washed off.

In the next step ((IV) in FIG. 1),
It is immersed in 10% nitric acid in the fourth tank, and ultrasonic vibration is radiated to the phosphor screen 3 for 1 minute. As a result, the oily base material at the joint portion of the panel 1 with the funnel 4 is washed off, and the potassium permanganate remaining on the panel 2 is dissolved and removed. Further, after pulling up the panel 2 from the fourth tank, it is immersed in 10% nitric acid in the fifth tank ((V) in FIG. 1) and ultrasonic vibration is radiated for 1 minute. As a result, almost the oily base material can be washed off.

Next, in the sixth tank ((VI) in FIG. 1),
Ultrasonic vibration is radiated to the fluorescent screen 3 in normal temperature tap water for 1 minute,
The nitric acid remaining on panel 2 is washed off. Further, the panel 2 is again immersed in the alkaline solution of potassium permanganate in the seventh tank ((VII) in FIG. 1) to irradiate the phosphor screen 3 with ultrasonic vibration for 1 minute. Due to
The graphite 3C, etc., which were not separated by the oxidizing agent cleaning treatment in the second tank, are separated and decomposed.

Then, in the eighth tank ((VIII) in FIG. 1), ultrasonic waves are radiated in tap water to almost wash the remaining deposits and potassium permanganate, and then the ninth tank (((VIII) in FIG. 1). IX)) 1
It is immersed in 0% nitric acid, and ultrasonic vibration is radiated toward the panel inner surface 2a for 1 minute. This dissolves or decomposes the residual potassium permanganate in the seventh tank, as well as the stripped products and decomposed products.

Next, nitric acid etc. are removed by ultrasonic cleaning in tap water in the 10th tank ((X) in FIG. 1), and immersed in ion-exchanged water in the 11th tank ((XI) in FIG. 1). Then, the ultrasonic vibration is radiated toward the panel inner surface 2a for 1 minute to completely remove the ionic substance, dust and the like attached to the panel inner surface 2a.

The cleaning time in the cleaning process so far is 11 minutes in total. Therefore, the process time is reduced by about half compared with the conventional cleaning process. After that, it is forcibly dried by hot air (see FIG. 1 (XII)). Since the panel 2 having the phosphor screen 3 thus washed and removed has been washed with potassium permanganate twice, the phosphor screen 3 is completely removed. Further, by washing with nitric acid three times, residual potassium permanganate, nitric acid, and deposits are removed by washing with tap water five times. Furthermore, since it is finally washed with pure water, stains do not remain on the panel inner surface 2a after drying. Therefore, the cleaning method has a high cleaning efficiency and enables a large amount of treatment.

Also, unlike the conventional treatment with hydrogen fluoride, the inner surface 2a of the glass panel is not etched to remove the graphite 3C, so that the inner surface 2a of the panel is not uneven. Therefore, the occurrence of defective reproduction due to the cleaning process is reduced,
Low cost regeneration is possible.

Furthermore, since hydrogen fluoride, which is highly toxic and has a problem in safety, is not used, it is possible to eliminate dangerous substances from the working environment and to create a safe working environment. together,
The elimination of hydrogen fluoride from the process simplifies the storage of dangerous substances and the treatment of the cleaning liquid, and in this respect also reduces the cost.

In the present embodiment, potassium permanganate is used as an oxidizing agent in an alkaline solution, and the oily base material is also removed by washing with nitric acid. However, the method is not limited to this. The graphite 3C can be removed by utilizing the action of cavitation by ultrasonic waves of other frequencies under the appropriate conditions of the oxidizing power of other oxidizing agents.

[0025]

As described in detail above, according to the present invention,
Oxidizing power of the oxidant and the action of cavitation due to the emission of ultrasonic vibration can effectively remove the graphite attached to the inner surface of the glass panel as the fluorescent surface forming substance without damaging the glass surface. Therefore, it is possible to regenerate the fluorescent screen of the cathode ray tube with high efficiency and with reduced occurrence of cleaning failure, and at low cost. further,
Since it does not use highly toxic hydrogen fluoride, it is possible to ensure the safety of the work environment.

[Brief description of drawings]

FIG. 1 is a diagram showing a cleaning process according to an embodiment of the present invention.

FIG. 2 is a diagram of a cleaning tank used in an example of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a cathode ray tube.

FIG. 4 is an enlarged sectional view of a panel.

FIG. 5 is a diagram showing a phosphor screen formed of a phosphor and graphite.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Braun tube 2 ... Panel 2a ... Panel inner surface 3 ... Phosphor screen 3R, 3G, 3B ... Phosphor 3C ... Graphite

Claims (2)

[Claims] 1. A method for cleaning and removing a fluorescent screen formed by adhering a phosphor and graphite to the inner surface of a glass panel of a cathode ray tube, wherein the phosphor screen is immersed in a cleaning solution which is an aqueous solution of an oxidizer,
A method for cleaning a fluorescent screen of a cathode ray tube, which comprises radiating ultrasonic vibrations to the fluorescent screen in the cleaning liquid. 2. The method for cleaning a fluorescent screen of a cathode ray tube according to claim 1, wherein the cleaning liquid is an aqueous solution of potassium permanganate and sodium hydroxide.