JP2788295B2 - Method for producing antistatic film and cathode ray tube - Google Patents

Description

The present invention relates to a method for producing an antistatic film and a cathode ray tube using the same.

(Prior Art) The front panel of a cathode ray tube used for a personal computer, various display terminals, and the like is easily charged, which causes a problem that an image is difficult to see due to adhesion of dust and the like in the atmosphere. To cope with this problem, JP-A-61-118946 discloses a technique for forming an antistatic film containing a silanol group, and JP-A-63-76247 discloses a technique of forming an Si (O
R) ₄ (R is an alkyl group) is applied by spraying and baked to form an antireflection film, and then an antistatic film of SnO ₂ and In ₂ O ₃ is formed on the antireflection film by a normal pressure CVD method. Techniques are disclosed. However, the former is easily affected by an external environment such as humidity and has an insufficient antistatic effect. The latter is
Since the CVD method is employed, it is not suitable for forming a large-area antistatic film, but also has a problem that the film forming cost is increased.

On the other hand, antistatic problems are not limited to cathode ray tubes, but also pose a problem for OA equipment with many glass and plastic parts. In particular, static electricity is easily generated in a copy machine or the like. Conventionally, a conductive paint containing an organic binder as a main component has been used. However, it has been difficult to provide a stable antistatic effect due to problems such as lack of heat resistance and weak film strength.

(Problems to be Solved by the Invention) As described above, although there is a wide range of demands for antistatic films, at present, satisfactory antistatic films cannot be obtained. In particular, an antistatic film which is easy to manufacture and has a stable antistatic effect has been desired.

The present invention has been made in order to satisfy the above demand, and provides a manufacturing method capable of easily obtaining an antistatic film having a stable antistatic effect. It is intended to provide a cathode ray tube obtained.

[Constitution of the Invention] (Means for Solving the Problems) The present invention provides a method for producing an antistatic film by applying a silica sol containing conductive oxide fine particles and then heat-treating the silica sol. C _n H _{2n + 1} OH
(N ≧ 4) alcohol containing alcohol is used.

The conductive oxide fine particles are stable in silica sol,
Any material may be used as long as the characteristics do not deteriorate at the temperature required for firing, and in particular, at least one of SnO ₂ or In ₂ O ₃
When a seed is used as a main component, an antistatic film having a high transmittance can be produced, which is effective for optical devices. Further, conductive oxide fine particles such as SnO ₂ : Sb, SnO ₂ : P, and In ₂ O ₃ : Sn to which an additive is added as necessary may be used. It is desirable to use such conductive oxide fine particles having a primary particle diameter of 200 ° or less, more preferably 150 ° or less, particularly when an antistatic film having a high transmittance is produced.

The above silica sol is basically made of silica (Si
O ₂ ) may be generated, but a solution containing Si (OR) ₄ (R is an alkyl group) as a main component is particularly preferable because a target antistatic film can be formed at a low temperature of 100 to 600 ° C. Further, M (OR) x (M; Zr, Al, M
g, Ca, etc.). In addition,
The concentration (solid content) of the silica sol may be appropriately set depending on the coating conditions and the like, but is preferably in the range of 0.5 to 10% by weight in terms of oxide.

The amount of the conductive oxide fine particles in the silica sol is:
It may be appropriately set so as to realize a good surface resistance of about 10 ¹⁰ Ω / □ or less as an antistatic film, and particularly in the range of 30 to 80% by weight based on the solid content (in terms of oxide) of the entire silica sol. It is desirable. The reason for this is that if the amount of the conductive oxide fine particles is less than 30% by weight, the antistatic effect under low humidity is reduced, that is, the surface resistance is increased by one to two digits, while the amount is 80% by weight. %, It becomes difficult to stably disperse the conductive oxide fine particles in the coating solution, and as a result, the storage stability of the coating solution may be reduced.

C _n H _{2n + 1} OH (n ≧ ₂₎ as a solvent component of the silica sol
Examples of the alcohol 4) include n-butanol, isobutyl alcohol, amyl alcohol and the like. As the solvent component, in addition to the alcohol component, methyl alcohol, ethyl alcohol, propyl alcohol and the like are used.From the viewpoint of forming a uniform antistatic film with a large area, the solvent component contains the C _n H _{2n + 1 in the} solvent component. OH alcohol is 2
It is desirable to contain 5% or more.

As a method for applying the silica sol, various methods such as a spray method, a spin coating method, and a dipping method can be adopted. When applied to the outer surface of the front panel of a cathode ray tube, it is preferable to employ a spray method (spraying method) from the viewpoint of simultaneously having an antireflection function. In this case, since the formed film surface has fine irregularities, a good antireflection effect can be provided. The uneven state can be arbitrarily adjusted depending on the coating conditions, but the average thickness of the formed film is around 1000 °, and the pitch of the unevenness is about 10 to 30 μm.
It is particularly preferable in terms of optical characteristics such as resolution to apply the coating so that the height before and after the unevenness is about 0.2 μm in surface roughness.

Further, after forming the antistatic film according to the present invention, spray coating silica sol containing no conductive oxide fine particles.
By baking, an antireflection film can be separately provided.

(Action) According to the present invention, it contains conductive oxide fine particles, and has a vapor pressure at room temperature of 30 mmHg or more and a boiling point of 100 ° C. as a solvent component.
After applying a silica sol containing an alcohol having a high C _n H _{2n + 1} OH (n ≧ 4) as described above, a heat treatment is performed to partially uneven the film thickness due to rapid volatilization of a solvent component in the coating process. Therefore, a smooth antistatic film having a uniform thickness and composition over a large area can be manufactured. Further, since the antistatic film is homogeneous in composition, it has a high film strength and is hardly deteriorated by an external environment. Further, since it can be formed by coating and baking, production becomes extremely easy. Especially,
By forming an antistatic film on the outer surface of the front panel by the above method, a cathode ray tube having an antistatic function can be obtained without deteriorating optical characteristics.

(Example) Hereinafter, an example of the present invention will be described in detail.

Example 1 Five kinds of conductive oxide fine particles shown in Table 1 below were contained on a glass substrate, and [Si (OC ₂ H ₅ ) ₄ ] was dissolved in an alcohol solvent, and the concentration in terms of siO ₂ was 3% by weight. After spin-coating silica sol, it was heat-treated at 250 ° C. to produce an antistatic film.

The surface resistance of each of the obtained antistatic films was measured. The results are shown in Table 1.

As is clear from Table 1, all of the antistatic films No. 1 to No. 5 can realize a low resistance of 10 ¹⁰ Ω / □ or less and have a good antistatic effect. However, in the case of the silica sol having the No. 1 composition, the conductive oxide fine particles are likely to settle,
The antistatic film formed by using the silica sol having the composition of 4 had a surface resistance of 10 ¹¹ Ω / □ in an environment of 10% humidity, and the antistatic effect was reduced.

Example 2 A silica sol having a composition of No. 3 in Table 1 was spin-coated on the front panel surface of a cathode ray tube, and was heat-treated through a 400 ° C. tunnel furnace.

When the surface resistance of the front panel of the cathode ray tube was measured,
It was 10 ⁷ Ω / □. On the other hand, the surface resistance of the front panel of the cathode ray tube not coated with the antistatic film was 10 ¹² Ω / □. The transmittance of the front panel surface of the cathode ray tube of Example 2 was as high as 90% or more, and no fogging was observed on the screen.

Example 3 A silica sol having the composition of No. 3 in Table 1 was spray-coated on the front panel surface of a cathode ray tube, and was heated through a tunnel furnace at 400 ° C.

The surface resistance of the front panel of the cathode ray tube was 10 ⁹ Ω / □, and the reflection was small.

Example 4 A silica sol having a composition of No. 3 in Table 1 was spin-coated on the front panel surface of a cathode ray tube, and heated through a tunnel furnace at 400 ° C. to form an antistatic film. Next, the [Si (OC
₂ H _{5) 4]} only ethanol 25%, n-butanol 75%
A silica sol having a concentration of 3% by weight in terms of SiO ₂ without the addition of conductive oxide fine particles dissolved in an alcohol solvent was sprayed and applied, and the panel was heated to 150 ° C.

The surface resistance of the front panel of the cathode ray tube, 10 ⁸ Ω / □ and is, also was reduced glare. Further, even when the cathode ray tube of Example 4 was exposed to an environment having a humidity of 10 to 90%, the surface resistance of the front panel did not increase to 10 ¹⁰ Ω / □ or more.

In the cathode ray tubes of Examples 2 to 4 described above, the time required for the induced voltage to become 0 V after the switch-off was measured. On the other hand, the cathode ray tube not coated with the antistatic film took 5 minutes or more.

[Effects of the Invention] As described in detail above, according to the present invention, an antistatic film having a stable antistatic effect can be easily obtained, and particularly, remarkable effects such as effective use as an antistatic film of a cathode ray tube. To play.

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Claims (2)

(57) [Claims] 1. A method for producing an antistatic film by applying a silica sol containing conductive oxide fine particles, followed by heat treatment, wherein C _n H _{2n + 1} OH (n ≧ 4) is used as a solvent component of the silica sol.
A method for producing an antistatic film, characterized by using an alcohol-containing film. 2. A cathode ray tube having an antistatic film formed on an outer surface of a front panel by the method according to claim 1.