JP3373101B2 - Paint for cathode ray tube interior - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for the interior of a cathode ray tube, comprising water glass in a medium and having iron oxide particles and graphite particles dispersed therein. 2. Description of the Related Art A conductive film is provided on the inner surface of a funnel glass of a cathode ray tube. This conductive film is formed by applying a paint containing conductive particles to the inner surface of the funnel portion, then drying and heating in the air. [0003] This coating material is typically represented by graphite particles of a conductive material and iron oxide, titanium oxide and silicon carbide for adjusting to an arbitrary electric resistance value in an aqueous medium containing water glass as an adhesive and a dispersant. Of the metal oxide or metal carbide to be suspended and dispersed. Depending on the specifications of the cathode ray tube to be applied, there is also a paint in which only graphite particles of a conductive material are suspended or dispersed, but as described in JP-B-63-45428, the spark current becomes relatively high. Therefore, it is common to use particles of graphite and metal oxides in combination. That is, graphite imparts conductivity and lowers the electric resistance of the coating, and metal oxide and the like function as a filler, while increasing the resistance of the coating similarly to the water glass of the adhesive. Therefore, by adjusting these compounding ratios, the electric resistance value and the adhesive strength of the coating are controlled to predetermined values. [0004] As described above, it is very important to disperse metal oxide particles in an aqueous paint and, in addition, to continuously disperse the metal oxide particles in order to prolong the pot life of the paint, in a paint for an interior of a cathode ray tube. It is. Improving the dispersion stability of the components contained in the paint for the interior of the cathode ray tube, extending the pot life, the applicant has been conducting various studies,
For example, the above publication describes the following findings. In this method, graphite and metal oxide fine particles are granulated using a negatively charged surface treatment agent to produce a composite powder having a negative charge as a whole, and then the composite powder is mixed with a binder and a dispersion. It is suspended in water containing the agent to make a paint. [0005] In the process of applying paint to the inner surface of a cathode ray tube, a spray coating method and a brush coating method have been frequently used in the past. The flow coating method called a coating method is becoming mainstream. Accordingly, it is required that the applied paint has a low viscosity. That is, while the viscosity of the paint by the conventional coating method was 100 to 200 mPa · s, the viscosity of the paint for flow coating was 10 mPa · s.
・ Low as s. As a result, it is clear from the Stokes equation representing the spontaneous sedimentation state of the particles in the liquid that it becomes difficult to maintain the dispersion of the metal oxide particles in the paint.
Further, considering the influence on the preservation environment, the above-mentioned prior art is unsatisfactory, and further improvement in dispersibility is required. In addition, if the conductive coating obtained from this coating is not firmly adhered to the inner surface of the funnel, it has an adverse effect on the characteristics of the cathode ray tube. In view of the above, an object of the present invention is to provide a coating for a cathode ray tube containing water glass in which iron oxide particles and graphite particles are dispersed, particularly, having excellent dispersion stability at a high temperature and a long time. It is an object of the present invention to provide a paint which can save time and is easy to handle. Other objects will be clarified in the following description. SUMMARY OF THE INVENTION The object of the present invention is to provide a method for producing silica and water in a water medium containing a dispersant and water glass, which is a main part of the present invention.
Suspended iron oxide particles and graphite particles coated with alumina, the coating applied to the inner surface of the cathode ray tube dispersed,
The amount of silica-alumina coating on the iron oxide particles is 4
-20% by weight, and the alumina content in the silica-alumina coating is adjusted to 40-90% by weight. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube interior in which silica-alumina-coated iron oxide particles and graphite particles are suspended and dispersed in an aqueous medium containing water glass. In the paint, the amount of the silica-alumina coating on the iron oxide particles is 4 to 20% by weight. In this case, the silica / alumina coating amount is more preferably 10 to 15% by weight. The silica-alumina coating on the iron oxide particles has the effect of changing the charge (positive charge) on the surface of the iron oxide particles into a negative charge. In a paint in which negatively charged graphite particles are dispersed together, such as a cathode ray tube interior paint according to the present invention, the particles are electrically repelled by making each particle surface have the same charge, Maintains a dispersed state. At present, the minimum amount that the surface of the iron oxide particles can be completely covered with silica-alumina is 4% by weight. If the amount is less than 4%, the iron oxide itself is exposed on the surface, and the graphite particles are attracted to this portion. As a result, agglomeration of dispersed particles occurs in the paint, which is not preferable. Conversely, if the coating amount exceeds 20% by weight, the silica-alumina coating becomes a main product to the iron oxide particles, and the adhesion of the formed conductive coating to the cathode ray tube decreases. . This is because silica-alumina coating has a lower hardness than iron oxide particles, in other words, it is soft, so if the amount of coating is large, particles such as metal oxides (iron oxide particles in the present invention) will be applied to the interior coating of the cathode ray tube. The function as a filler is no longer exhibited due to the incorporation of, and the hardness of the resulting conductive coating is reduced, and the adhesiveness to a CRT is reduced. Further, from the viewpoint of the dispersion state of the particles in the paint, no particular change is observed even if the coating amount exceeds 20% by weight. Increasing the amount of coating is not economical because it increases processing cost and time. Further, the present invention provides a method of suspending and dispersing silica-alumina-coated iron oxide particles and graphite particles in an aqueous alkali solution, particularly an aqueous solution containing silicate anions, ie, an aqueous medium containing water glass. In the cathode ray tube interior coating, the alumina content in the silica-alumina coating is 40 to 90% by weight. In this case, the alumina content is more preferably 45 to 60% by weight. Alumina has the effect of suppressing the dissolution of silica, but if its content also exceeds 90% by weight, KO
As in the case of suspension in an aqueous alkali solution such as an aqueous H solution or an aqueous NaOH solution, even in an aqueous medium containing water glass, aggregation and precipitation of particles due to the low surface charge of alumina occur. Conversely, even if the alumina content in the silica-alumina coating is less than 40% by weight, in other words, even if the silica content is 60% by weight or more, agglomeration and sedimentation of particles occur.
This is because silica has a much higher solubility in water glass than alumina, and is a phenomenon that occurs when the paint is left for a long time or the storage environment changes in temperature. That is, silica
If the silica content in the alumina coating is high, the silica component in the coating will dissolve in the water glass as silicate,
The ionic micelle concentration of the silicate in the aqueous solution locally increases. The aqueous solution having the increased ionic micelle concentration is unstable in terms of concentration equilibrium, and precipitates as silica on the surface of the particles existing in the solution. If this phenomenon continues, the bonding of the dispersed particles tends to occur, and as described above,
Agglomeration and sedimentation of the particles occur, which makes it impossible to improve the dispersion stability of the paint and extend the pot life, which are the objects of the present invention. Hereinafter, the present invention will be described in more detail by way of examples. (Adjustment of paint) Particle size 0.05 to 0.1 μm as conductive material
The graphite particles pulverized to a sufficient degree and the 15 types of iron oxide particles (F1 to F15) shown in Table 1 were used as dispersed particles, and carboxymethyl cellulose (Carboxy Methyl Cellulos) was used as a dispersant.
e, hereinafter abbreviated as CMC), potassium silicate as a binder and water as a medium were prepared as coating materials. These materials were added in the following mixing ratios, and sufficiently stirred using a stirrer to prepare each suspension. Graphite particles 3.0% by weight Iron oxide particles 18.0% by weight CMC 0.3% by weight Potassium silicate 8.7% by weight Water 70.0% by weight Then, these suspensions are dispersed by a ball mill. By doing so, it became a paint for the interior of the cathode ray tube. (Evaluation of paint) When the paint is left at a high temperature, the dispersion state of the dispersed particles changes, and the viscosity decreases as the paint temperature rises, so that the dispersed particles tend to settle. For this reason, dispersion stability at high temperatures is an important issue from the viewpoint of maintaining the usable life of the paint for a long time without being affected by the environment. Therefore, as a study evaluation, each of the produced paints was allowed to stand at 50 ° C. for 3 weeks, and the sedimentation state of the contained dispersed particles was investigated. Specifically, the paint was poured into a 100 ml screw tube, sealed, and left in a thermostat kept at 50 ° C. for 3 weeks. After standing, the sedimentation rate was calculated from the thickness (or height) of the sediment in the tube and the height of the poured paint, and the sedimentation rate (%) = (thickness (or height) of the sediment in the tube.
塗料 height of paint in pipe) × 100. In this study, it was determined that a paint with less sediment had better dispersibility at high temperatures. The results are shown in Table 1. The evaluation of the homogenization treatment required for the cathode ray tube interior paint will be described. As described in the section of the problem to be solved by the invention, in a recent cathode ray tube manufacturing process, a flow coating method is mainly used as a method of applying a paint for forming an interior coating. In this flow coating method, the excessively flowing conductive paint is collected,
Again, it is sink-coated. For this reason, a part of the paint circulates several times, and is homogenized (stirred) in the paint pool tank.
Will be processed. However, when the stirring treatment is performed for a long time, the coating on the surface of the metal oxide is destroyed, the charge on the surface of the metal oxide changes, and aggregation by electric suction occurs. As an experimental study of this phenomenon, a paint stirrer that rotates the paint at a speed of 400 revolutions / min.
The coating was gently poured into a screw tube, and the sedimentation state was observed when the coating was left for 10 minutes. The state of sedimentation is the same as the case of leaving under high temperature as described above, the sedimentation rate (%)
= (Thickness (or height) of sediment in tube / height of paint in tube) × 100. (Evaluation of Conductive Coating) Next, the evaluation (adhesion) of the conductive coating obtained from each of the prepared paints will be described. Regarding this adhesion, 150 mm × 10
A glass plate of 0 mm x 1 mm is tilted at 60 degrees, paint is applied from the top of a clean glass plate, and after waiting for excess paint to drip, it is dried at a temperature of about 100 ° C.
By baking at about 0 ° C., conductive coatings from various paints were prepared. Then, after a tape was applied to each of the obtained coatings, the tape was peeled off, the state of the coating adhered to each tape was observed, and the presence or absence of peeling was evaluated. In Table 1, the amount (%) of coating is silica
Alumina coverage / (iron oxide + silica / alumina coverage)
And the amount (%) of alumina in the coating is Al2O3 / (A
l2 O3 + SiO2). Settling rate (%) 50 ° C is 50
It shows the thickness of the sediment / the height of the total paint after standing at 3 ° C. for 3 weeks. The sedimentation rate (%) stirring is the thickness of the sediment / the height of the total paint when the stirring treatment is performed for 6 hours under the condition of a stirrer-400 revolutions / minute and left for 10 minutes. The adhesiveness was shown with and without peeling on the state of adhesion of the film to the tape side.
Remarks are classified into Examples and Comparative Examples according to the evaluation results. [Table 1] The test results are as shown in Table 1. Coatings in which iron oxide was not coated with silica-alumina (iron oxide particles F1) and coatings in which the amount of silica-alumina coating was 1.9% by weight (iron oxide particles F2) were left at 50 ° C. and left after stirring. In both cases, the sedimentation of paint-containing particles is remarkable,
In addition, peeling of the film was observed in the adhesiveness. Also,
In a coating material having a silica / alumina coating amount of about 4% by weight (iron oxide particles F3 and F4), the amount of alumina in the coating is 1%.
At 9.5% by weight (F3), sedimentation of about 10% occurs at a sedimentation rate, but the amount of alumina in the coating is 39.7% by weight.
At (F4), a remarkable improvement effect on sedimentation can be seen. When the coating amount is about 10% by weight (F
5 to F8), the effect of the amount of alumina in the silica-alumina coating was confirmed, and the amount of alumina in the coating was 49.6.
In the case of the coatings of 8% by weight and 80.8% by weight (iron oxide particles F6 and F7), even after standing at 50 ° C. for 3 weeks and stirring, the particles were hardly sedimented and were in a good dispersion state. Hereinafter, the coating amount is 15% by weight (iron oxide particles F9 to F9).
11) Even when it changed to about 20% by weight (F12 to F14), the dependence of the amount of alumina in the coating was similarly confirmed. The paint having an amount of coating on the iron oxide particles of 24.8% by weight (iron oxide particles F15) shows a dispersed state. The evaluation result of the sedimentation rate is good, but peeling was observed due to adhesiveness. This is because, as described in the embodiments of the invention, silica
This is because when the amount of the alumina coating was too large, the hardness of the coating was lowered, and sufficient adhesiveness was not obtained. To summarize the above, the amount of coating is 4 to 2
When the coating content is 0% by weight and the alumina content in the coating is 40 to 90% by weight, the sedimentation rate of the coating is low, and the adhesion of the obtained conductive coating to glass is good. Especially when the amount of coating is about 10-1
The dispersion stability is best when the content is 5% by weight and the alumina content is 45 to 60% by weight. The difference between the sedimentation rate and the paint outside this range is remarkable, and in Table 1, the paints of Examples 1 to 6 are very similar in terms of the homogenization treatment required for the cathode ray tube interior paint. It turns out that it is excellent. As described above, in the water glass-containing coating material in which the iron oxide particles and the graphite particles are dispersed, the coating amount of the silica-alumina coating on the iron oxide particles and the alumina content in the coating are adjusted to a specified range. It turned out that useful results were obtained alone. From this, the paint of the present invention can maintain a stable dispersion state in an environment such as a temperature environment or a long-time homogenization treatment. As described above, the cathode ray tube interior paint according to the present invention is less affected by the storage environment than conventional paints, can be stored for a long period of time, and is easy to handle. Can be supplied.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01J 9/20 H01J 9/20 A 29/88 29/88 (58) Field surveyed (Int.Cl. ⁷ , DB name) C03C 15/00-23/00 C09C 1/00-3/12 C09C 15/00-17/00 C09D 1/00-10/00 C09D 101/00-201/00 H01J 9/20-9/236 H01J 29 / 86-29/98 H01J 61/30-61/48

Claims (1)

(57) [Claim 1] A cathode ray tube in which iron oxide particles and graphite particles coated with silica / alumina are suspended and dispersed in an aqueous medium containing a dispersant and water glass. In the paint applied to the inner surface, the amount of the silica-alumina coating based on the iron oxide particles is adjusted to 4 to 20% by weight, and the alumina content in the silica-alumina coating is adjusted to 40 to 90% by weight. Characteristic paint for cathode ray tube interior.