JPH08176794A - Treating liquid for shielding electric field and production thereof - Google Patents

Abstract

PURPOSE: To obtain a coating film having high transparency and such satisfactory electric conductivity as to shield leakage electromagnetic waves from CRT by firing at a low temp. CONSTITUTION: Fine oxide particles of <=80nm average particle diameter are dispersed in a polar solvent for dispersion contg. N-methyl-2-pyrrolidone and the resultant dispersion treating liq. is mixed with a polar solvent for dilution and a partial hydrolyzate of an alkyl silicate. Fine particles of indium oxide to which 1-15wt.% tin has been added are effectively used as the fine oxide particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an electric field shield treatment on a cathode ray tube (CRT) face panel of a television of an OA equipment, and in particular, an electric field shield treatment liquid capable of obtaining a suitable electric field shield effect by a spin coating method. And a manufacturing method thereof.

[0002]

2. Description of the Related Art Recent office automation (O
Due to A), many OA equipments have been introduced into the office, and the chances of working facing the CRT display of the OA equipment are increasing. The surface of the face panel of this CRT is apt to be dust-attached due to electrostatic charge, and may be discharged and give an electric shock when a human body comes into contact during the work. As a countermeasure against this, it is widely known that a conductive film is attached to the surface of the panel to be grounded to prevent charging.

However, it has been pointed out that electromagnetic waves and light generated from electronic devices may affect the human body, and the working environment has come to be reviewed (for example, Nikkei Electronics, 1993,
No. 584, P85). In a CRT display, X-rays, β-rays as radiation, pulse magnetic fields, pulse electric fields and ultraviolet rays as electromagnetic fields are generated, and when working, simply stop dust adhesion on the face panel surface due to static electricity and shock shock. First, the impact on the human body must exceed safety standards.

Of these, electromagnetic waves are generated in the vicinity of the electron gun and the deflection yoke, and as the display becomes larger, a larger electromagnetic wave tends to leak to the surroundings. Leakage magnetism can be dealt with by improving the yoke shape and installing a cancel coil. In order to shield the leaked electromagnetic waves, a conductive film is attached to the surface of the CRT face panel to absorb the leaked electromagnetic waves, as in the case of preventing electrification. But with antistatic and electric field shields,
The conductivity level required for the film is greatly different, and the former is considered to have a surface resistance of about 10 ⁸ Ω / □, while the latter is at least 10 ⁵ Ω / □ or less, Preferably, a conductivity of the order of 10 ³ Ω / □ is required.

Further, since the conductive film here is formed on the screen surface, it is required to have various optical characteristics in order to prevent deterioration of resolution in addition to being transparent in the visible light region.
When viewed from the inside of the CRT, there is a light scattering phenomenon in the surface forming film. Therefore, the formed conductive film needs to have a sufficiently small diffusion component in transmitted light. The haze value is used to evaluate the scattering of the transmitted light, and it is defined by the percentage of the diffuse transmitted light amount to the linear transmitted light amount. In a practical CRT, the haze value is required to be approximately 2% or less, and in order to reduce the haze value, it is necessary to reduce the light scattering sources in the film and the film surface as much as possible.

As a cause of image disturbance caused by external light rays, reflection of a fluorescent lamp or an external scene due to reflection on the screen surface is raised. As one of the countermeasures, there is a method of forming an uneven film on the surface of a CRT, which blurs a reflected image by irregularly reflecting an external light ray, and has been put to practical use as an antiglare treatment. As another method, there is known a method of reducing reflection by utilizing a difference in refractive index between a film formed on the surface and CRT glass. This leads to destructive interference by controlling the film thickness of mutual interference of reflected light generated at the interface. As the CRT surface treatment, in consideration of resolution, the antiglare treatment scatters internal light rays as well, so that it is desirable to add an antireflection function.

Since the inside of the cathode ray tube is in a high vacuum of several Pa or less, it is designed to increase the wall thickness of the glass or to have a curved shape so as to withstand atmospheric pressure. It is not preferable in terms of strength to heat the cathode ray tube in this state to a high temperature. In order to secure the accuracy of the optical system such as the electron gun and the shadow mask inside, the surface coating is formed to substantially 200
It must be done at a temperature below ℃.

As a method of forming the transparent conductive film which satisfies the above requirements, there are vacuum vapor deposition and CVD method. The film formed by these methods has sufficient conductivity and high transparency to obtain an electromagnetic shielding effect. Furthermore, it is possible to add an antireflection function by controlling the film thickness. However, since a vacuum system is used, a large amount of cost is required to form the film, and it is not suitable for manufacturing a practical CRT.

Further, a treatment liquid in which an organic compound of indium, tin or antimony is mixed with an organic solvent is applied to the substrate, and a highly conductive film of tin-doped indium oxide or antimony-doped tin oxide is thermally decomposed. Although a method of forming at low cost is widely known, in order to complete the thermal decomposition reaction, it is necessary to set the firing temperature to 400 ° C. or higher. From the above reason, it is extremely inconvenient for the production of a practical CRT in the process. is there.

As an inexpensive low-temperature method for forming an antistatic coating, a method of spin coating an antistatic treatment liquid is known (Japanese Patent Laid-Open Nos. 1-211830 and 1-299).
887, etc.). As a treatment liquid, a method is known in which conductive fine particles are dispersed in a silicate solution and an organic solvent, and a film is formed by utilizing a polymerization reaction of alkyl silicate (for example, JP-A-62-273270). Japanese Patent Laid-Open Nos. 1-29887 and 2-202
443, JP-A-2-77473, etc.).
However, with these treatment liquids, although a conductive coating film that satisfies the antistatic function can be obtained, it is not possible to obtain sufficient conductivity to shield leakage electromagnetic waves.

[0011]

The object of the present invention is to provide an antireflection function because it has sufficient conductivity to shield a pulsed electric field which may affect the human body, especially in a CRT, and has excellent optical characteristics. An object of the present invention is to propose a treatment liquid for an electric field shield capable of forming a coating film that can be added directly on a CRT surface panel at a low temperature of 200 ° C. or less, and a manufacturing method thereof.

[0012]

The present invention has an average particle size of 8
The gist is to disperse indium oxide fine particles (ITO) having a thickness of 0 nm or less and 1 to 15% by weight of tin added thereto by using NMP which is a polar solvent.

Further, the invention is characterized in that a silicate solution is used as a binder for the ITO fine particles or for the surface of the glass of the CRT face panel. The silicate solution for a binder is a partial hydrolyzate of an alkyl silicate, and is, for example, an orthoalkyl silicate to which water and an acid catalyst are added to proceed hydrolysis and dehydration polycondensation. At this time, the alkyl group is preferably a lower alkyl group such as methyl and ethyl. A product obtained by previously polymerizing an orthoalkyl silicate to a tetramer to a pentamer is commercially available, but it can be used as a silicate solution even if hydrolysis and dehydration polycondensation are further progressed using such a material as a raw material. The silicate has a siloxane bond as a basic structure and is a polysiloxane. There is no problem even if a silicate solution in which Si in polysiloxane is replaced with Ti, Zr, or Al is used for adjusting the refractive index and reinforcing the strength. In order to substitute with Al, Ti or Zr, a method such as mixing and hydrolyzing a hydrolyzate of these metal alkoxides and a hydrolyzate of an alkyl silicate may be used.

The solution contains water necessary for the hydrolysis / polycondensation reaction of the alkoxide and hydrochloric acid or nitric acid as an acid catalyst. The content of solid components in the silicate solution,
The ratio by weight of the ITO fine particles is preferably 40/60 or less in terms of SiO ₂ .

A coupling agent may be used for the purpose of improving the dispersion, but in the present invention, any coupling agent may be used as long as it does not affect the conductivity, and if added in a small amount, no problem occurs. It is possible to use an aluminum-based or zirconia-based coupling agent. For example, as the silane coupling agent, γ-aminopropyltriethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, vinyltriethoxysilane, γ-mercaptopropylsilane and the like, and as the aluminum coupling agent, aluminum is used. Isopropylate, ethyl acetoacetate aluminum diisopropylate, mono se
As zirconia-based coupling agents such as c-poxyoxyaluminum diisopropylate, zirconia aluminate coupling agents having a carboxyl group and a methacryloxy group as functional groups are known.

As a method for producing the treatment liquid for electric field shielding of the present invention, the fine ITO particles having an average particle diameter of 80 nm or less are NM.
It comprises a dispersion treatment step of highly dispersing in a polar solvent for dispersion containing P, and a step of mixing the ITO fine particle dispersion, the silicate solution and the polar solvent for dilution.

[0017]

In the present invention, ITO fine particles having an average particle size of 80 nm or less are selected as the conductive substance of the electric field shield treatment liquid, and the ITO fine particles are dispersed in a mixed liquid of silica sol and a polar solvent containing NMP to form a low temperature film. Since the transparency at the time is improved and the ITO fine particles have extremely high conductivity as compared with the tin oxide fine particles and the like, a highly conductive coating having a sufficient electric field shielding effect can be obtained. Here, when the ITO particles have an average particle size of more than 80 nm, the haze value becomes large and the resolution deteriorates. More preferably, it is 50 nm or less.

The content of tin in the ITO fine particles is preferably in the range of 1 to 15% by weight in order to secure high conductivity as the ITO particles and considering the dispersibility of the particles in the treatment liquid. It is more preferably 1 to 12% by weight.

Further, the solid content concentration largely depends on the film thickness, and although increasing the film thickness contributes to the improvement of the film conductivity, it has a bad influence on the light transmittance and the haze value of the film. The solid content concentration of the treatment liquid for electric field shield suitable for a face panel is preferably 1 to 12% by weight. The content of ITO particles in the treatment liquid is preferably 1 to 10% by weight.

Further, the weight ratio of the silicate solution to the ITO particles is preferably 40/60 or less in terms of SiO ₂ , and when it is 40/60 or more, the film strength is improved.
It is not suitable as an electric field shield for the surface of a CRT face panel because it deteriorates the optical characteristics and reduces the conductivity. If it is less than 1/98, the optical properties are good, but the film strength tends to be extremely deteriorated. However, by overcoating with a silicate solution, the silicate permeates and functions as a binder, exhibiting good characteristics. Therefore, there is no problem when a two-layer structure is adopted to add an antireflection function.

The content of NMP in the electric field shield treatment liquid is preferably 1 to 20% by weight. When the dispersibility of the ITO fine particles is poor, the film formed by the treatment liquid has poor optical properties and the film conductivity is low, which is not preferable for a CRT face panel. Since the surface of the ITO fine particles is charged in the solvent and forms an electric double layer with the solvent, electrostatic repulsion due to adsorption of solvent molecules (or ions) near the surface of the ITO particles causes dispersion of the particles.・ It is one of the factors that affect the aggregation. Particularly, when NMP is less than 1% by weight, the absolute value of the potential difference (zeta potential) in the diffusion layer portion of the electric double layer is small,
In order not to give a sufficient repulsive force to the repulsion between ITO particles,
The dispersion system is not stable and particles are aggregated / precipitated, resulting in poor optical properties and conductivity of the film formed by the treatment liquid. However, when it is 20% by weight or more, the dispersibility of the ITO fine particles is improved, but since NMP is a high boiling point solvent, a high strength film cannot be obtained by low temperature firing (250 ° C. or less). In addition, since the drying speed becomes slow, it is likely to cause unevenness of the film, which is not particularly suitable for continuous multi-layer coating. N
The content of MP in the treatment liquid is more preferably 1 to
It is 10% by weight.

Further, in order to improve coatability with the substrate so as to obtain an even and smooth coating film that is compatible with NMP during film formation, particularly during coating, methanol, ethanol, 1 -Propanol, 2-propanol (IPA), 1-butanol, 2-butanol, diacetone alcohol (DAA) and other alcohols, 2-methoxyethanol (MCS), 2-ethoxyethanol (ECS), propylene glycol methyl ether (P
GM) and other glycols, cyclohexanone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MI
It is desirable to adjust the solution by adding a polar solvent such as ketones such as BK). The content of these diluents is 25-9
9% by weight, particularly 90 to 97% by weight is preferable. By using a liquid regulator, that is, a latent heat regulator or a viscosity or surface tension regulator, the coating property of the treatment liquid for electric field shielding on a substrate and film formation. It is possible to significantly improve the sex.

As a manufacturing method, ITO fine particles are previously dispersed and mixed in NMP, and then mixed with a silicate solution and a diluting polar solvent to obtain a treatment liquid for electric field shielding in which ITO fine particles are highly dispersed. .

The treatment liquid of the present invention is a dip, spray,
A film can be formed on the surface of the CRT face panel by a spin coating method. Particularly, when spin coating the surface of the CRT face panel, the surface of the panel serving as a substrate is 25 to 80.
It is desirable to preheat to ℃, especially 35 to 50 ℃. This is because the seasonal difference of the environmental temperature in the film production is removed, and the preheating optimizes the drying speed of the electric field shield treatment liquid, thereby improving the film forming property. In addition, the rotation speed of the spin coating is preferably in the range of 75 to 200 rpm. If the rotation speed is less than 75 rpm, the centrifugal force for applying the electric field shielding treatment liquid is insufficient with respect to the solvent viscosity, and the spin coating is uniform and smooth. No film can be obtained. On the contrary, high speed rotation of 200 rpm or more is not preferable because it damages the function of the CRT.

[0025]

EXAMPLES Examples of the present invention are shown below. The silicate solution serving as the binder was 17.6 g of methyl silicate 51 (manufactured by Tama Chemical Industry Co., Ltd.) and 27.1 g of DAA while stirring, 3.5 g of a 5% hydrochloric acid aqueous solution, and 1.8 g of distilled water.
g of the mixed solution was added dropwise, and 17.9% by weight in terms of SiO ₂
Was used as the methyl silicate sol.

The silicate for overcoat used when taking a two-layer structure for antireflection was prepared as follows, and diluted with ethanol so as to have an appropriate amount of SiO ₂ and used. 24 g of methyl silicate 51 and 43.6 g of ethanol were mixed, a water-ethanol solution (45.65 g of distilled water + 20 g of ethanol) was added dropwise with stirring, and 9.66 g of a 1 wt% HNO ₃ aqueous solution and ethanol 7.
It was obtained by dropping 1 g of the mixed solution.

The film formation for evaluating the treatment liquid was performed as follows. In the case of one layer, a soda lime glass substrate (20 × 10 cm, thickness 3 mm: refractive index 1.53) is washed and then placed in a drier kept at 35 to 50 ° C. and heated to a predetermined film formation substrate temperature. The processing liquid for electric field shielding is supplied from the beaker onto the temperature-adjusted substrate, and the rotation speed is set to 160.
Spin coating at rpm. After being shaken off for 3 minutes and dried, it was held at 180 ° C. for 30 minutes and baked.

When a two-layer film is formed by overcoating, the treatment liquid is applied, shaken off for 3 minutes and dried, and then a silicate solution for overcoating is applied and shaken off for 1 minute.
The same is fired at 180 ° C.

For measuring the surface resistance, Hiresta IP MCP-260 and Loresta FP manufactured by Mitsubishi Petrochemical Co., Ltd.
An MCP tester was used. A haze meter HR-200 (manufactured by Murakami Color Research Laboratory) was used to measure the haze value, and a spectrophotometer MPS-2000 was used to measure the reflectance.
As a film thickness measurement load, a surface roughness meter Surfcom 570A (manufactured by Tokyo Seimitsu Co., Ltd.) was used.

Examples 1 to 4 and Comparative Example 1 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm) and NMP were mixed and stirred, and an ITO dispersion treatment liquid was obtained by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. Next, the ITO dispersion treatment liquid and the silicate solution are mixed according to the ratio of the ITO fine particles and the SiO ₂ and stirred with a stirrer, and then a polar solvent for dilution (DMF, DAA, ethanol) is added to obtain a predetermined solid content concentration. It was adjusted. The composition and film properties are shown in Table 1.

Examples 1 to 4 and Comparative Example 1 in Table 1 are examples in which the SiO ₂ / ITO ratio was changed according to the manufacturing process according to the present invention. All the treatment solutions showed good dispersibility.

In Example 2, the SiO ₂ / ITO ratio was 2/9.
8 is an example. When the SiO ₂ / ITO ratio is larger than 5/95, the film strength and the surface resistivity of the ITO single-layer film decrease due to the small amount of binder silicate, and the film characteristics are poor, but the double-layer film with an overcoat is good. The film characteristics are shown.

Examples 1, 3 and 4 are SiO ₂ / IT
O ratios of 10/90, 20/80 and 35/6 respectively
5 is an example. It can be seen that the haze value and the sheet resistance increase as the content of SiO ₂ increases.

Comparative Example 1 has a SiO ₂ / ITO ratio of 50/5.
This is an example of 0. The dispersibility of the treatment liquid is good, but Si
It is understood that the O ₂ / ITO ratio is out of the range of the present invention, both the one-layer film and the two-layer film have high sheet resistance and haze value, and the reflectance of the two-layer film is also high, which is a problem in practical use.

Example 5 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm), NMP and DAA were mixed and stirred, and an ITO dispersion treatment liquid was obtained by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. next,
The ITO dispersion treatment liquid and the silicate solution are mixed and stirred with a stirrer, and then a polar solvent for dilution (DAA, ethanol)
Was added to adjust the concentration of the solid content. The composition and film properties are shown in Table 2.

Example 6 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm), NMP and DAA were mixed and stirred, and an ITO dispersion treatment liquid was obtained by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. next,
The ITO dispersion treatment liquid and the silicate solution are mixed and stirred with a stirrer, and then a polar solvent for dilution (DMF, ethanol)
Was added to adjust the concentration of the solid content. The composition and film properties are shown in Table 2.

When NMP and another polar solvent (eg DMF, DAA) are used as the dispersing solvent, the dispersibility is slightly reduced, but the characteristics of the obtained film are practically no problem and the treatment liquid It turns out that is enough.

Examples 7 and 8 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm), NMP, and a coupling agent were mixed and stirred, and then an ITO dispersion treatment liquid was obtained by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. Next, the ITO dispersion treatment liquid and the diluting polar solvent (DM
(F, DAA, ethanol) were mixed and adjusted to a predetermined solid content concentration. The composition and film properties are shown in Table 3.

Example 7 is a treatment prepared by using vinyltriethoxysilane (TSL8311: manufactured by Toshiba Silicone Co., Ltd.) as a coupling agent, and Example 8 is prepared by using methyltrimethoxysilane (TSL811: manufactured by Toshiba Silicone Co., Ltd.). It is a liquid. Since the binder silicate is not included, the ITO film single layer has high sheet resistance and haze value, and sufficient film strength cannot be obtained. But,
The two-layer film obtained by continuously applying the overcoat solution has low surface resistance and haze value, and shows practically sufficient characteristics for electric field shielding.

Comparative Example 2 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm) and ethanol were mixed and stirred, and an ITO dispersion treatment liquid was obtained by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. Next, the ITO dispersion treatment liquid and the silicate solution are mixed according to the ratio of the ITO particles and SiO ₂ , and after stirring with a stirrer, a polar solvent for dilution (NMP, DMF, DAA,) is added, and a predetermined solid content concentration is obtained. Adjusted to. The composition and film properties are shown in Table 4.

This Comparative Example 2 has the same composition as that of Example 1,
In this example, ethanol is used as the dispersion solvent. When NMP is not used as the dispersion solvent, the treatment liquid can be obtained but the dispersibility is poor, and as shown in Table 4, a film for electric field shielding cannot be obtained. Further, the stability as a treatment liquid was poor, and sedimentation of particles was observed.

Comparative Example 3 ITO fine particles (Sumitomo Metal Mining Co., Ltd .: average particle size 30)
nm), ethanol, NMP, DMF, DAA, and a silicate binder were mixed and stirred, and then an ITO dispersion treatment liquid was prepared by applying a ball mill using zirconia balls having a diameter of 5 mm for 12 hours. When the preparation methods were different, the dispersibility was poor even with the same composition as in Example 1, and a uniform film could not be formed by a spin coater.

Comparative Example 4 ITO fine particles having a tin content of 18.7% by weight (Sumitomo Metal Mining Co., Ltd .: average particle size 30 nm) were mixed and stirred, and then a ball mill using zirconia balls having a diameter of 5 mm was used. An ITO dispersion treatment liquid was obtained by spending 12 hours. Next, after mixing the ITO dispersion treatment liquid and the silicate solution and stirring with a stirrer, a polar solvent for dilution (DM
(F, DAA, ethanol) was added to adjust to a predetermined solid content concentration. The composition and properties are shown in Table 4. Tin content is 1
When it is 8.7% by weight, the sheet resistance becomes high and a sufficient electric field shielding effect cannot be obtained. Further, sedimentation of particles is observed and the dispersion is not sufficient.

The embodiment of the present invention has been described above.
Regarding the antireflection function when the two-layer film structure is adopted, the film thickness and the like can be set according to the substrate on which the film is to be formed, and the characteristics of the treatment liquid according to the present invention are not limited to those of the examples. Not something.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

As described above, according to the present invention,
After the ITO fine particles are previously dispersed in a polar solvent for dispersion (particularly NMP), a silicate solution and a polar solvent for dilution (DN
F, DAA, etc.) makes ITO efficient.
Since the fine particles can be highly dispersed, a transparent conductive film having good optical characteristics and conductivity can be obtained by baking at a low temperature of 200 ° C., and it can be applied to the surface treatment of a cathode ray tube to effectively prevent damage by electromagnetic waves leaking. It has the effect of being able to prevent. Furthermore, the two-layer transparent conductive film using the electric field shield treatment liquid can supply a low-cost CRT having not only an electric field shield effect but also a low reflection effect, and has an extremely great industrial value.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Keiichi Orita 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Inside Tohoku Kako Co., Ltd. (72) Takayuki Yumura 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Tohoku Kako Co., Ltd.

Claims (5)

[Claims] 1. A treatment liquid for electric field shield comprising a polar solvent for dispersion containing fine conductive oxide particles having an average particle diameter of 80 nm or less, a polar solvent for dilution and a silicate solution for a binder. 2. The conductive oxide fine particles are indium oxide (ITO) containing 1 to 15% by weight of tin.
The treatment liquid for electric field shield according to claim 1, which contains 1 to 10% by weight of fine particles. 3. The treatment liquid for electric field shield according to claim 1, wherein N-methyl-2-pyrrolidone (NMP) is contained in the polar solvent for dispersion. 4. The amount of SiO ₂ contained in the silicate solution for binder is 40 / weight ratio with respect to the ITO fine particles.
It is 60 or less, The processing liquid for electric field shields of Claim 1 characterized by the above-mentioned. 5. A treatment liquid for an electric field shield, characterized in that conductive oxide fine particles having an average particle diameter of 80 nm or less are dispersed in a polar solvent for dispersion, and then a polar solvent for dilution and a silicate solution for a binder are mixed. Production method.