JP3210076B2 - Cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube, and more particularly to a cathode ray tube provided with a thin film having an antistatic function on an outer surface of a front panel.

[0002]

2. Description of the Related Art An outer surface of a front panel of a cathode ray tube accumulates static charges on the outer surface during operation or at the end of operation.
There were problems such as applying an electric shock to the human body and adsorbing dust.

In order to solve such a problem, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 64-27146 discloses a cathode ray tube provided with a glass gel thin film containing a salt of an alkali metal or a salt of an alkaline earth metal having a silanol group as a main component. However, these salts have a problem in terms of environmental stability because the metal thin film absorbs moisture in the air to lower the resistance of the glass thin film. That is, it is easily affected by humidity, and a sufficient effect cannot be obtained at low humidity. Furthermore, the metal salt also has the disadvantage that it absorbs carbon dioxide in the air and turns into a metal carbonate, which precipitates from the glass gel thin film. Japanese Patent Application Laid-Open No. 3-77247 discloses a technique for forming an antistatic film comprising conductive fine particles and an inorganic binder. However, in the method using conductive fine particles, the transmittance changes depending on the film thickness.
Therefore, in order to provide a cathode ray tube with sufficient transmittance, the thickness of the antistatic film must be reduced, and if the film thickness is reduced, a sufficient antistatic effect cannot be obtained. are doing.

[0004]

As described above, the prior art has problems such as instability to the environment and deterioration of optical characteristics. An object of the present invention is to provide a cathode ray tube provided with an antistatic film which is environmentally stable and has good optical characteristics with a small film shrinkage.

[0005]

In order to solve the above-mentioned problems, the present invention relates to a cathode ray tube having a front panel outer surface which is composed of at least SiO ₂ or P ₂ O ₅ as a main component, a heteropolyacid and a hygroscopic metal salt. And a glass gel thin film comprising:

Further, the present invention is characterized in that the heteropolyacid and the hygroscopic metal salt are contained in the range of 0.01% by weight or more and 60% by weight or less with respect to the thin film. Further, the hygroscopic metal salt is an alkali metal salt or an alkaline earth metal salt. Further, when the weight of the hygroscopic metal salt is A and the weight of the heteropolyacid is B, the weight ratio is 0.01 ≦ B
/ A ≦ 5000.

[0007]

According to the present invention, a hygroscopic metal salt is supported by a heteropolyacid, and the hygroscopic metal salt and the heteropolyacid are sealed in the gap between the glass skeletons in the glass gel thin film. By preventing the reaction with the air, the environmentally stable and transparent glass gel thin film can be reduced in resistance.

Conventionally, a hygroscopic metal salt has been used as an antistatic film.
There are those using, but as shown in JP-A-64-27146
Moisture-absorbing metal salts such as
You. When the metal element of the hygroscopic metal salt is M, the metal ion
M⁺ Is an alkoxide for forming the glass skeleton of the thin film, for example,
Si (OR)_Four, As shown in FIG.⁺ −^-
Make free radicals like O-Si). Through this free radical
And the protons of the moisture absorbed by the metal salt are conducted,
It is well known that rates go up. However, (M⁺ −
^- O-Si) free radical metal ion M⁺ Is dioxide in the air
It easily reacts with carbon to form carbonate, and metal carbonate is coated
Precipitates to the outside and the conductivity decreases. As a hygroscopic metal salt
Is, for example, as shown in JP-A-64-27146.
Li, K, Na, Ba, Sr, Ca nitrate, hydrochloric acid
Salts, sulfates, carbonates, etc.
No problem.

On the other hand, a heteropolyacid (hereinafter referred to as HPA) is known as a substance for lowering the resistance. HPA is a different type of condensed acid generated by condensation of an oxyacid. It refers to a product condensed between oxygen acids. HPA
Is a structure in which a poly atom is arranged via oxygen around a center hetero atom. There are many examples of the centrally located heteroatom, which extends to elements of Groups 1 to 8 of the Periodic Table, specifically, P, As, Si, etc., via oxygen around the central heteroatom. The formed poly atoms are composed of limited atoms such as Mo, W, Nb, and V. Specific examples of HPA include phosphotungstic acid (H
₃ PW ₁₂ O ₄₀ .nH ₂ O), phosphomolybdic acid (H ₃ P
Mo ₁₂ O ₄₀ .nH ₂ O), tungstosilicic acid (H ₄ Si
W ₁₂ O ₄₀ .nH ₂ O), molybdogermanic acid (H ₄ Ge
Mo ₁₂ O ₄₀ .nH ₂ O).

These polyanions of HPA have a structure called Keggin structure as shown in FIG. As shown in FIG. 2 (a), the Keggin structure means that twelve octahedral oxygen atoms 1 of a polyatom share vertices and edges with each other to form a tetrahedral oxygen atom of a heteroatom. 2 is a polyhedral structure, in which three octahedrons 1 share a vertex and a ridge with each other to form one unit. As shown in FIG. It refers to a polyhedral structure around which a tetrahedron is coordinated. For example, a structure in which three octahedrons WO ₆ are arranged in a tetrahedron around P. Assuming that the Keggin structure is a primary structure, HPA has a polyanion and a counter cation (H ⁺ It is well known that it has a three-dimensional array consisting of metal, inorganic and organic cations) and water of crystallization. Therefore, HPA usually exists as a three-dimensional array having water of crystallization. The water molecules in the water of crystallization are aqua cations that are protonated, for example, H
₃ (H ₂ O) constituting the crystal having a sequence of face-centered cubic lattice diamond in the form of ₂₉ ^3+. And, since these protons move around quickly in the crystal, HPA has attracted attention as a proton conductor. Further, since HPA has a three-dimensional array structure as described above, it is bulky in structure and has a large molecular weight. Such an HPA is, for example, Si
(OR) When dissolved in ₄ etc. to form a gel thin film,
HPA is encapsulated in the gaps in the glass skeleton present in the gel, and as shown in FIG. 3, the HPA is incorporated into the Si—O—Si network structure. This structure is stable, and the HPA does not deposit outside the coating. Therefore, a low resistance film can be obtained.

However, even when HPA is dissolved in a solution for forming the above-mentioned glass skeleton, for example, a solution of Si (OR) ₄ or the like, HPA itself does not react with Si (OR) ₄ and Si (OR) ₄ Condenses on its own to form Si-OS
Form an i-bond. For this reason, in a film composed of a strong Si—O—Si skeleton, HPAs are isolated from each other in gaps between the Si—O—Si skeletons, so that proton conduction between HPAs is blocked by the Si—O—Si skeleton. , The conductivity does not increase so much. Therefore, it is conceivable to increase the amount of HPA in order to increase the conductivity only with HPA. However, in order to provide sufficient conductivity, the relative amount of the molecules forming the glass skeleton is reduced, and the relative amount of HPA is increased. Will increase,
When these molecules are condensed, the formation of the Si-O-Si skeleton is prevented by the HPA, and as a result, a film is not formed. As a result, the film strength is greatly reduced and the film loses its transparency.
Therefore, the present inventors have paid attention to the fact that the above-mentioned HPA is bulky in structure and contains crystallization water.

That is, by mixing a hygroscopic metal salt with HPA which is a proton conductor and encapsulating it in a Si—O—Si skeleton, HPA and metal ions M ⁺ in the metal salt are mixed. To give a three-dimensional structure, and for example, (H
PA-M ⁺ )- ^- Making O-Si radicals such as in the gel framework. Here, (HPA-M ⁺ 4) The free radicals are bulky and larger than the gaps in the gel skeleton, and are surrounded by Si—O—Si, so that the free radicals are incorporated into the Si—O—Si network structure as shown in FIG. And HPA and metal ion M ⁺ Is considered to form free radicals and to stably exist in the gel thin film having a glass skeleton.

The reaction between the HPA and the hygroscopic metal salt occurs by mixing. Also, (HPA-M ⁺ ), Water molecules of water of crystallization contained in HPA are partially absorbed by the hygroscopic metal salt, and water of crystallization is not easily desorbed from the crystal. Therefore, metal M ⁺ Means that the proton is always adsorbed. In addition, since HPA functions to prevent invasion of carbon dioxide outside the membrane, (HPA-M ⁺ )
It is assumed that the free radical and carbon dioxide do not react to form a carbonate.

Further, unlike the case of only HPA, (HP
AM ⁺ ) Are free radicals and are not isolated from each other. As a result, the proton concentration in the thin film is increased, which has the effect of increasing the conductivity of the thin film. Most of the protons are different from those due to moisture in the air outside the membrane.
Because of the water of crystallization, it is held inside the coating, and the conductivity is not affected by the humidity outside the coating. Therefore, an antistatic film which is environmentally stable and has excellent optical characteristics can be obtained.

That is, when the hygroscopic metal salt and the HPA were used alone, the conductivity of the antistatic film was insufficient. However, these substances were mixed to form the hygroscopic metal salt with HPA.
When encapsulated in the skeletal component so as to be supported by PA, it is considered that the problem of conductivity can be solved by the interaction between the hygroscopic metal salt and HPA. Furthermore, (HP
AM ⁺ ) Is bulky in structure, so that the film of the gel thin film is less shrunk, so that a substance having a function other than antistatic, such as a dye, can be encapsulated without being affected by the film strength and environmental stability.

The substance serving as the skeleton of the gel thin film is SiO ₂ ,
Such as _{P 2 O 5, B 2 O} 3, or is a mixture thereof, metal alkoxides, are preferred made from a solution, such as metal acetyl compounds. Further, for the purpose of imparting functionality such as improvement of the film strength, an element other than Si, P, and B, such as Zr, Ti, Fe, Al, and V, may be included.

In order to utilize the interaction between the above-mentioned hygroscopic metal salt and HPA, it is desirable to mix them at a predetermined ratio. If the hygroscopic metal salt is A and HPA is B,
The weight ratio preferably satisfies 0.01 ≦ B / A ≦ 5000. When B / A is 0.01 or less, no interaction occurs, which is the same as when HPA was used alone.
When A is 5000 or more, it is the same as when the hygroscopic metal salt is used alone.

The content of the hygroscopic metal salt and HPA contained in the glass skeleton component is as follows with respect to the glass skeleton component.
It is desirable that the content be 0.01% by weight or more and 60% by weight or less. If the content is 0.01% by weight or less based on the glass skeleton component, a sufficient antistatic effect cannot be obtained because the amount of the conductive substance is insufficient with respect to the glass skeleton component. Also, 60
% Or more (HPA-M ⁺ ) By Si-O
-The formation of the Si skeleton is prevented, and the film strength is significantly reduced, and as a result, no film is formed.

The coating of the present invention can be obtained by dissolving the above-mentioned heteropolyacid and the hygroscopic metal salt in the skeleton component and the above-mentioned metal alkoxide, and applying the solution to a cathode ray tube by a spray method, a spin method, a dip method or the like. .

[0020]

Next, the present invention will be described with reference to examples.

First, a gel thin film coating solution was prepared by changing the addition amounts of lithium nitrate as a hygroscopic metal salt and phosphotungstic acid as a heteropoly acid at the following composition ratios. After dip coating this solution on a glass substrate,
By sintering at 120 ° C. for 10 minutes, the film thickness becomes about 0.1 mm.
A 1 μm thin film was obtained. Table 1 shows the evaluation results of the obtained films. Here, the amounts of lithium nitrate and phosphotungstic acid shown in Table 1 are represented by weight ratio to the obtained thin film. As an evaluation method of the obtained thin film, first, an initial resistance value, a film appearance, a pencil hardness (pencil hardness test JIS K540)
0) was measured, and then the film was subjected to two weathering tests, a heat resistance test and a water resistance test, to measure a resistance value. Here, the heat resistance test refers to a measurement of surface resistance after holding in a constant temperature oven at 60 ° C. for 500 hours.
After immersion in pure water at 0 ° C. for 24 hours, the surface resistance was measured. Each resistance value, film strength, and the like indicate an average value of the obtained data. Weight ratio: Tetraethoxysilane 27 wt% Nitric acid 0.29 wt% Water 34 wt% Isopropyl alcohol 72 wt% Lithium nitrate 0-5 wt% Phosphotungstic acid 0-15 wt% %

[0022]

[Table 1] 5 to 8 show the relationship between the addition amount and the film characteristics.

FIG. 5 shows the film characteristics when the amount of addition of the heteropolyacid alone was changed without adding the hygroscopic metal salt of Experiment Nos. 1 to 5 in Table 1, and the addition amount of phosphotungstic acid is plotted on the horizontal axis. The vertical axis represents a surface resistance value. FIG.
, The solid line indicates the initial resistance value, the broken line indicates the resistance value after the heat resistance test, and the dashed line indicates the resistance value after the water resistance test. In addition, a region indicated by oblique lines is a region where transparency is not maintained. Further, the film strength is within a practical range of 7H.
From 9H to 6H, which are not within the practical range, and those below 6H, which are not practical ranges, are indicated by x. Hereinafter, the same legend will be used from FIG. 6 to FIG. FIG.
Thus, in the case of the film to which phosphotungstic acid is added, the resistance value is almost the same as the initial value and shows excellent weather resistance, but the resistance value required for the antistatic effect is 1 × 10 ¹⁰ Ω.
It can be seen that the addition amount needs to be approximately 50 wt% or more in order to obtain the following. However, as shown in Table 1, at this amount, the film strength was weak and the transparency was not maintained. This tendency was observed in other HPAs.
It is considered that this is because excess HPA is precipitated as a crystal without being enclosed in the gap.

FIG. 6 shows the resistance values when the amount of the hygroscopic metal salt alone was changed without adding the HPAs of Experiment Nos. 6 to 11 in Table 1 above. This indicates that the initial resistance value in the region where the transparency of the film to which lithium nitrate is added is maintained is good, but the resistance value is significantly deteriorated after the weather resistance test and the weather resistance is poor. This tendency was the same for other hygroscopic metal salts. this is,
In the case of the heat resistance test, the relative humidity is reduced, so that the metal salt becomes a carbonate and precipitates outside the coating. In the case of the water resistance test, the metal salt dissolves in water. I understand.

FIG. 7 shows experiment numbers 12 to 1 in Table 1.
Fixing the addition amount of lithium nitrate of No. 5 to 0.01 wt%,
5 is a graph showing the addition amount of phosphotungstic acid on the horizontal axis and the surface resistance value on the vertical axis. Thus, when the metal salt was not added, the amount of HPA, which was a region having poor film properties, was reduced to 50 wt.
%, It is possible to obtain an antistatic film having good weather resistance when the metal salt is added in a small amount of 0.01 wt%. However, when the HPA content is 55 wt%, the transparency and the film hardness deteriorate. Therefore, the metal salt (A) and HPA
It is desired that the ratio to (B) is B / A ≦ 5000.

Therefore, the results obtained when the amount of lithium nitrate was changed while the amount of HPA was fixed at 55 wt% are Experiment Nos. 15 to 17. As can be seen from the result of Experiment No. 16, when the amount of the metal salt is increased, a film having good weather resistance and exhibiting an antistatic effect even when HPA is 55 wt% is obtained. This tendency was also observed when using other metal salts and HPA. Therefore, the metal salt (A) and HPA
It was found that the ratio of (B) to B / A ≦ 5000 was desired.

The sample of Experiment No. 17 is devitrified and has a low film strength of 6H. This means that the sum of the amounts of A and B is 6
2 wt% and more than 60 wt%, which is considered to be due to the amount of the conductive substance being too large with respect to the skeleton component. From other experimental results, it was found that to obtain a good antistatic film, A + B
It was found that ≦ 60 wt%. In addition, it was also found that the amount of the conductive substance was not more than 0.01 wt% and there was no antistatic effect. From the above, the preferable range of the addition amount of the metal salt (A) and the heteropolyacid (B) is 0.01
wt% ≦ A + B ≦ 60 wt%.

FIG. 8 shows the results of Experiment Nos. 18 to 21 when the amount of the metal salt was fixed at 10 wt% and the amount of HPA was changed. 3 is a graph expressed as a surface resistance value. From this, it can be seen that the smaller the amount of phosphotungstic acid, the worse the weather resistance becomes. If the amount is less than 0.1 wt%, both the transparency and the film hardness are not practical. This tendency was also observed when using other metal salts and HPA. Accordingly, it is desired that the ratio between the metal salt (A) and the HPA (B) is B / A ≧ 0.01. From the above, it was found that the desirable ratio between the metal salt (A) and the heteropolyacid (B) must be 0.01 ≦ B / A ≦ 5000.

Experimental results 22 to 25 show the results of examination of the composition ratio at which a better film strength and surface resistance value can be obtained. Accordingly, as a more preferable range, the amount of the conductive substance is 10% by weight or more and 32% by weight or less based on the skeleton component, and the ratio of the metal salt (A) to the heteropolyacid (B) is 1 ≦.
B / A ≦ 500. Next, specific examples of the present invention will be described. <Example 1>

FIG. 9 is a partially cutaway side view showing a cathode ray tube 10 manufactured according to the present invention. This cathode ray tube 10
It has an airtight glass envelope 11 whose interior is evacuated. The envelope 11 has a neck 12 and a cone 13 continuing from the neck 12. Furthermore, the envelope 11 has a cone 13 and a face plate 14 sealed with frit glass. A metal tension band 15 is wound around the outer periphery of the side wall of the face plate 14 for explosion protection.
An electron gun 16 for emitting an electron beam is arranged on the neck 12. The inner surface of the face plate 14 has an electron gun
A phosphor screen 17 made of a phosphor layer that emits light when excited by an electron beam from 16 is provided. Also,
Outside the cone 13, a deflecting device (not shown) for deflecting the electron beam so as to scan on the phosphor screen is mounted.

The antistatic film 18 of the present invention is formed on the outer surface of the face plate 14 of the cathode ray tube 10 by applying the lower layer forming solution and the upper layer forming solution of the first embodiment. .

In the above embodiment, the coating is performed by the dipping method. In the present embodiment, the composition liquids of Experiment Nos. 23 and 25 in Table 1 are spun on the front surface of the face plate of a 25-inch cathode ray tube after assembly. Apply by coat, 150 ℃
For 30 minutes to form a transparent antistatic film having a thickness of 0.2 μm. The surface resistance at this time is 1 × 10 ⁹ Ω. When this was subjected to the same heat resistance test and water resistance test as in Example 1, the surface resistance after the test was 1 × 10 ^{9 which was} not different from the initial resistance. Ω. As a result, a cathode ray tube having an antistatic film which is very stable against the environment was obtained, and the remarkable effect of the present invention was recognized. <Example 2>

Experiment No. 23 in Table 1 as in Example 1 above
2% by weight of a dye for a color selective absorption filter is further added to the composition liquids of No. 25 and No. 25, applied to a face plate of a color picture tube by a spray method, baked at 150 ° C. for 30 minutes, and provided with a color selective absorption filter. An antistatic film was prepared. The surface resistance at this time is 4 × 10 ⁹ When subjected to the same heat resistance test and water resistance test as in Table 1, the surface resistance after the test was 8 × 10 after the heat resistance test.
⁹ Ω, 1 × 10 ⁹ after water resistance test Ω. Than this,
Even when a dye was added, a remarkable effect of the present invention was observed.

[0034]

As described above, according to the present invention, a cathode ray tube having an antistatic film that is stable against the environment can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an atomic model showing a state of an antistatic film of a conventional cathode ray tube.

FIG. 2 is a schematic diagram showing a primary structure of a heteropoly acid.

FIG. 3 is a schematic diagram of an atomic model showing a state of a gel film containing a heteropolyacid.

FIG. 4 is a schematic diagram of an atomic model showing a state of a gel film for explaining the present invention.

FIG. 5 is a characteristic diagram showing film properties when a hygroscopic metal salt is not added to a gel thin film and the addition amount of only a heteropolyacid is changed.

FIG. 6 is a characteristic diagram showing film characteristics when a heteropolyacid is not added to a gel thin film and the amount of addition of only a hygroscopic metal salt is changed.

FIG. 7 is a characteristic diagram showing film properties when a hygroscopic metal salt and a heteropolyacid are added to a gel thin film and the amount of only the hygroscopic metal salt is changed.

FIG. 8 is a characteristic diagram showing film characteristics when a hygroscopic metal salt and a heteropoly acid are added to a gel thin film and the amount of addition of only a heteropoly acid is changed.

FIG. 9 is a sectional view showing a configuration of a cathode ray tube according to the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-27146 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 29/88

Claims (4)

(57) [Claims] 1. A cathode ray tube comprising a glass gel thin film mainly containing at least SiO ₂ or P ₂ O ₅ and containing a heteropolyacid and a hygroscopic metal salt on an outer surface of a front panel. 2. The thin film according to claim 1, wherein said heteropolyacid and said hygroscopic metal salt are contained in an amount of 0.01% by weight or more and 60% by weight or less based on said thin film.
A cathode ray tube as described. 3. The cathode ray tube according to claim 1, wherein the hygroscopic metal salt is an alkali metal salt or an alkaline earth metal salt. 4. When the weight of the hygroscopic metal salt is A and the weight of the heteropolyacid is B, the weight ratio is 0.01 ≦ 0.01.
2. The cathode ray tube according to claim 1, wherein B / A ≦ 5000.