CN1084361C - Low-resistance internal conductive coating material for cathode-ray tube and its preparation method - Google Patents

Abstract

The present invention relates to a low-resistance internally conductive coating material for a CRT. The present invention is characterized in that the low-resistance internally conductive coating material has the components by the weight percentage: 12 to 30 percent of graphite powder, 10 to 20 percent of alkali metal silicate, 0.1 to 3 percent of dispersing agent, 0.5 to 5 percent of ethylene glycol and 42 to 60 percent of pure water. After the practical proof for many times, the resistivity of a coating film of the present invention is usually between 0.03 and 0.05 omega cm, the discharge current(100 to 150 A) generated by the resistivity can not damage various electronic elements, and meanwhile, the brightness and the stability of a picture are enhanced.

Description

Low-resistance internal conductive coating material for cathode-ray tube and preparation method

The present invention is electrically conducting coating and the preparation method who is coated on cathode tube cone inwall.

Fig. 1 is the general configuration figure of picture tube.1, cone inwall; 2, anode cap; 3, electron beam gun; 4, cone outer wall; 5, neck; 6, screen.Whole body is made by glass among the figure, 4 ones of cones to be coated be the outer conductive paint with electroconductibility, 1 internal conductive coating that is painted with of cone.Electron beam gun 3 is arranged in neck 5 and contacts with electrically conductive graphite coating, in assembling electron beam gun process, keeps away and unavoidably can scrape a spot of shred of filming.Because three electrodes have the voltage of tens KV usually on the electron beam gun, the shred layer of filming that these are peeled off can make between the electrode and be short-circuited, and causes the electron beam gun sparking, produces immediate current, and current value is up to more than the 500A.Outside the electrode of these immediate currents energy damages own, can also damage the low semiconductor element of proof voltage and puncture insulator element.So in actual applications, immediate current can not surpass 200A, but low excessively also not all right, is good with 100-150A.And existing high-impedance internal conductive coating (as application number: 96102050.4), be to adapt to Toshiba and Philips colour picture tube, they all use in the high resistant and are coated with.It is that main raw material is formulated with the ferric oxide, and film coated surface resistance is up to more than the 0.2 Ω cm, the electric current that obtains behind the high pressure by electron beam gun and anode cap too little (＜100A) phenomenons such as the dark and picture instability of television image appear.In addition,, lose a part of electric capacity, the emissive power of colour kinescope are reduced, not reach best effect, reduce brightness, also reduce work-ing life because the resistance height must make the resistance very low (usually less than 60 Ω) of managing the outer material that applies.This shows that the above-mentioned defective that high-impedance internal conductive coating exists can not satisfy the needs of Hitachi's type technology at the colour picture tube production line, therefore, this is a technical problem of being badly in need of solution.

The objective of the invention is provides a kind of low-resistance internal conductive coating material for cathode-ray tube and preparation method in order to solve the problem of above-mentioned existence.It can realize film coated surface resistance below 0.08 Ω cm, improves purposes such as picture brightness and increase picture stability.

In order to achieve the above object, the present invention adopts following proportioning and composition (weight percent):

Graphite Powder 99 12-30%;

Alkalimetal silicate 10-20%;

Dispersion agent 0.1-3%;

Ethylene glycol 0.5-5%;

Pure water 42-60%;

Wherein the Graphite Powder 99 median size is at 0.8-10 μ m;

Wherein alkalimetal silicate is at least a in water glass or the sour potassium, and its modulus is between 2.7-3.7, and granularity is at 1-3 μ m, and concentration is at 25-35%;

Wherein said dispersion agent is selected at least a in carboxymethyl cellulose, sodium naphthalene sulfonate, methylcellulose gum, cellulose acetate, polyacrylic ester sodium salt or the polyacrylic acid ester ammonium salt for use.

The preparation method of low-resistance internal conductive coating material for cathode-ray tube:

A, stir by top component and proportioning thorough mixing after, add ball milling in the ball mill, 8-10 hour ball milling time;

B, sieve through 200-300 purpose vibratory screening apparatus and get final product again.

Adopt be coated with in the low-resistance with high resistant in be coated with and the method for usefulness overcomes all with being coated with the adverse consequences of bringing in the high resistant.In the high resistant of pipe rear portion coating 1/3rd, be coated with (claiming again to be coated with in the soft arcing), be coated with in the rest part low-resistance, can make pipe outer coating material resistance higher relatively (getting final product) like this less than 150 Ω.Use be coated with in the low-resistance of the present invention after, cathode tube has produced bigger electric capacity, its emissive power have also improved a lot, and the brightness of cathode tube and life-span all are improved, and very big leeway are also being arranged aspect the emissive power of cathode tube adjusting.

Through repeatedly facts have proved, the present invention films resistivity usually between 0.03-0.05 Ω cm, and consequent discharging current (100-150A) neither can damage various electronic components, has also improved picture brightness simultaneously and has increased picture stability.

Do a simple declaration with regard to this electrically conducting coating material therefor below:

Graphite Powder 99 adopts the pure natural high-carbon graphite, below the median size 10 μ m, accounts for about 70% below the common 1 μ m, and median size can not be too thin, and when all being lower than 0.8 μ m, because the coating densification, the colored picture tube cone is after 400-450 ℃ of burning handled, and it is bad to exit easily.The weight of Graphite Powder 99 in electrically conducting coating must not be lower than 12%, is higher than 30%, and content is low excessively, is coated with the electroconductibility that rete can not get being scheduled to, too high levels, and the coating thickening is peeled off tendency, and can be reduced the release rate of gas.

What caking agent used among the present invention is alkalimetal silicate, as water glass, potassium silicate all can, its modulus between 2.7-3.7, concentration about 30%, granularity 1-3 μ m.Modulus is low excessively, and bonding strength is not enough, and modulus is too high, causes coatingsurface coarse easily, and extracting vacuum is time-consuming more, and the above equadag coating that either way can cause comes off.

The used dispersion agent kind of colour picture tube internal conductive coating is a lot, the present invention selects carboxymethyl cellulose, sodium naphthalene sulfonate, methylcellulose gum, cellulose acetate, polyacrylic ester sodium salt or polyacrylic acid ester ammonium salt for use, dispersion effect is all good, can be used alone, but also also mix together.By experiment showed, that repeatedly its consumption should be between 0.1-3%, less than 0.1% o'clock, disperse insufficiently, be higher than at 3% o'clock, increased discharge quantity.

The purpose that makes spent glycol is in order to improve venting speed, increase the levelling property of coating, make film coated surface smooth, has good surface appearance, because ethylene glycol can be evenly dispersed in this electrically conducting coating, behind the dried coating film, the ethylene glycol volatilization, form countless trickle apertures in film coated surface, these holes help emitting of gas.

Water as dispersion medium must be pure water, otherwise will influence electroconductibility.It is too high that consumption is lower than the viscosity of 42% o'clock coating, difficulty when brushing operation, also influence the homogeneous of coat-thickness, be difficult to form uniform coating, and consumption surpasses at 60% o'clock, concentration and viscosity are low excessively, easily cause trickling during brushing, above film forming preferably either way, so, should strict control pure water add-on.

Adopting 200-300 order vibratory screening apparatus to filter among the preparation method, mainly is to filter impurity or big micelle particle in the coating.Because in manufacturing processed, can infiltrate impurity, or form big micelle etc.

Fig. 1 is the picture tube structural representation.

Embodiment 1, (the Graphite Powder 99 median size accounts for 70% at 1 μ m to select Graphite Powder 99 28% for use, all the other are in 0.8-10 μ m), (modulus is 3 to potassium silicate 15%, granularity is at 1-3 μ m, and concentration is about 30%), carboxymethyl cellulose 2.8%, ethylene glycol 4.5% pure water 49.7%.The said components thorough mixing is stirred, add ball milling in the ball mill, 8-10 hour ball milling time, sieving with 200-300 order vibratory screening apparatus gets final product.

Embodiment 2, select Graphite Powder 99 12% (all the other are the same), water glass 20% (modulus is 2.7, and all the other are with embodiment 1), sodium naphthalene sulfonate 3%, ethylene glycol 5%, pure water 60% for use.The said components thorough mixing is stirred, add ball milling in the ball mill, 8-10 hour ball milling time, sieving with 200-300 order vibratory screening apparatus gets final product.

Embodiment 3, select Graphite Powder 99 20% (all the other are with embodiment 1), water glass and potassium silicate 18% (they account for each 1/2nd is 9%, and modulus is 3.7, and all the other are with embodiment 1) for use, methylcellulose gum 2%, ethylene glycol 4%, all the other pure water add to 100%.The said components thorough mixing is stirred, add ball milling in the ball mill, 8-10 hour ball milling time, sieving with 200-300 order vibratory screening apparatus gets final product.

The mensuration of resistivity: get the slide glass of 76 * 26mm, clean, on 50mm length, brush the coating that mixes equably with absorbent gauze, put into 105-110 ℃ of loft drier baking 30 minutes, insert again in 450 ℃ of electric furnaces, heated 30 fens, take out and put into 105-110 ℃ of loft drier baking 15 minutes, moved into the moisture eliminator internal cooling 10 minutes, sheet glass being filmed one faces down again, and is disposed across on the mercury electrode, and coated surface is contacted with mercury, on sheet glass, put one piece of 50g counterweight, use the resistance measurer measuring resistance.Measure by the said determination mode, the resistivity of three embodiment is respectively: embodiment 1 is 0.05 Ω cm; Embodiment 2 is 0.04 Ω cm; Embodiment 3 is 0.035 Ω cm.And the resistivity of high resistant is generally about 0.25 Ω cm.Its formula is resistivity (Ω cm)=actual measurement resistance * weight of filming (g)/film wide (cm) * length (cm) * graphite density (g).

Claims (2)

1, a kind of low-resistance internal conductive coating material for cathode-ray tube is characterized in that: proportioning and composition (weight percent) are as follows:

Graphite Powder 99 12-30%;

Alkalimetal silicate 10-20%;

Dispersion agent 0.1-3%;

Ethylene glycol 0.5-5%;

Pure water 42-60%;

Wherein the Graphite Powder 99 median size is at 0.8-10 μ m;

Wherein alkalimetal silicate is at least a in water glass or the potassium silicate, its modulus between 2.7-3.7, granularity 1-3 μ m, concentration is at 25-35%;

Wherein said dispersion agent is selected at least a in carboxymethyl cellulose, sodium naphthalene sulfonate, methylcellulose gum, cellulose acetate, polyacrylic ester sodium salt or the polyacrylic acid ester ammonium salt for use.

2, a kind ofly make the preparation method that right is wanted 1 low-resistance internal conductive coating material for cathode-ray tube, it is characterized in that:

A, stir by the component of claim 1 and proportioning thorough mixing after, add ball milling in the ball mill, 8-10 hour ball milling time;

B, sieve through 200-300 purpose vibratory screening apparatus and get final product again.

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