JPH09178903A - Anti-reflective coating - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an antireflection film capable of reliably achieving an antireflection function at low cost even when applied to a large area. SOLUTION: The depth of a valley formed by a convex portion and a concave portion is 0.05 on the outer surface of an antireflection film for preventing reflection of external light.
To 0.2 μm, fine convexes and concaves are formed, and the area of the convexes forming the irregularities is 7 times the surface area of the outer surface.
Configure to occupy more than half.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an antireflection film,
Particularly, it relates to an antireflection film for an image display face plate of a cathode ray tube or the like.

[0002]

2. Description of the Related Art Research on a film (antireflection film) for reducing the reflectance of a glass surface has long been used for lenses of cameras, glasses, and the like. Currently, VDT (visual
It is used as an antireflection filter to reduce the reflected light from the display terminal. There are various types of antireflection films, but the ones currently used are mainly multilayer films and heterogeneous films.

The multi-layer film has a structure in which a low-refractive index material and a high-refractive index material are alternately laminated on the glass surface, and the antireflection effect thereof is a total effect of optical interference between the layers. For the multilayer film, see Physics of Sin Film No. 2 (1964), pages 243 to 284 (Physics
of Thin films 2, (1964) p.243-p. 284).

A film having a refractive index distribution in the thickness direction of the film is called an inhomogeneous film. When the average refractive index of this film is lower than that of the substrate glass, it becomes an antireflection film. In the case of a heterogeneous film, it is general that the surface of gas is made porous. After forming an island-shaped metal film deposited on the glass surface, fine unevenness is formed by sputter etching to form an inhomogeneous film, and a method of reducing the reflectance is known as Upride Physics Letter No. 36 (1980). Pp. 727-730 (Appl. Phys.
Lett, 36 (1980) p.727-p.730). In addition, Zoda lime glass is replaced with SiO ₂ supersaturated H ₂ S
Solar Energy, No. 6 (1980) is a method of dipping in an iF ₆ solution to make the surface porous to reduce the reflectance.
Year) page 28 to page 34 (Solar Energy 6 (1980)
p.28-p.34).

[0005]

The above-mentioned prior art, the multilayer film, is limited in the forming method to the sputtering and the vacuum deposition method, and requires high-precision control of the film thickness, so that the cost is high and it is difficult to increase the area. There was a problem. The method of forming a heterogeneous film by sputter etching also has the problems of high cost and difficulty in increasing the area. H ₂ Si
In the method of forming a heterogeneous film by immersing it in an F ₆ solution to make the surface porous, it is difficult to form fine irregularities, and a sufficient antireflection function does not occur. Further, since the unevenness is not sufficiently fine, there is a problem that the transmittance is reduced together with the reflectance.

By the way, the present inventors have previously proposed to apply ultrafine particles to an antireflection film, but as a result of further diligent studies, in order to exert the antireflection film function, the surface is subjected to submicron-order fine processing. We obtained the finding that is effective.

An object of the present invention is to provide an antireflection film which can achieve an antireflection function reliably at low cost even when applied to a large area.

[0008]

The above-mentioned object is to achieve a depth of a valley formed by a projection and a depression of 0.05 to 0.2 μm on the outer surface of an antireflection film for preventing reflection of external light. Yes,
This is achieved by forming fine irregularities in which the area of the convex portion forming the irregularities occupies 70% or more of the surface area of the outer surface.

For example, when the antireflection film is formed of ultrafine particles, it is difficult to maintain the film formation only by using the ultrafine particles, and thus a binder material is required. In this case, if the outer surface exposed area of the ultrafine particles is 70% or more, the unevenness of the particles is exposed on the film surface, in other words, the binder is scraped, resulting in a fine (submicron) size. It becomes the surface (of the order).

The reason for the above 70% of the area ratio is that the ultrafine particles are geometrically obtained from a schematic plan view after observing (that is, averaging) the ultrafine particles as a sphere having a uniform particle size. 73% in the case of vertical and horizontal respective parallel Haihashi (∵ πΓ ^2/4
r ² : r is the ultrafine particle diameter, the numerator means the ultrafine particle exposed area, and the denominator means the binder exposed area. In the plan view, the ratio of one binder space surrounded by four particles is shown as an inverse number. It is 73% in the calculation, but it is defined as 70% because it is almost 70% due to the actual dispersion of particles and the relationship of plane → spherical conversion. If close packing is assumed (3 particles form one binder space), it is about 80% or more. (∵ π
/ 2√3).

(Ultrafine Particles) The average particle diameter of the ultrafine particles preferably applied to the antireflection film is 0.1 μm or less. These are commonly called submicron-order particles.

The desirable particle size distribution is such that the maximum peak is in the vicinity of the average particle size and the particle size is about 50% of all particles.
The maximum particle size is about twice the average particle size, and the minimum particle size is about 1/2 of the average particle size. More preferably, a mixture of Si (OR) ₄ alcohol solution added with SiO ₂ ultrafine particles having an average particle size of 0.1 μm or less and at least two or more of acetylacetone, acetone and ethyl alcohol is added to a glass. This is achieved by coating the surface.

The solution is a mixed solution of an alcohol solution of Si (OR) ₄ (R is an alkyl group, preferably having 8 or less carbon atoms, for example, C ₂ H ₅ —) and at least two or more of acetylacetone and acetone ethyl alcohol. Is preferred.

It should be noted that if the average particle size exceeds 0.3 μm, optical interference will be a visual obstacle.

In the method of forming the antireflection film on the glass surface, the glass surface is coated with a solvent to which ultrafine particles having an average particle size distribution of 0.1 μm or less are added, and after firing, Si (OR) It is preferable to overcoat a mixed solution of ₄ (R is an alkyl group) alcohol solution and at least two or more of acetylacetone and acetone ethyl alcohol. Incidentally, such an antireflection film is particularly suitable for an image display tube.

Further, it is a composite granular material composed of two or more kinds of inorganic oxides, in which two or more kinds of inorganic oxides are mixed with each other or one inorganic oxide is mixed with the other inorganic oxide. It is effective to use ultrafine particles that form a granular structure included in the oxide. In this case, it is preferable that at least one of the two or more kinds of inorganic oxides is an antireflection functional component and the rest are conductive components.
Further, the conductive component is preferably at least 10 (wt)%.

The particle size (average particle size) of the ultrafine particles (especially SiO ₂ ultrafine particles) is restricted by the relationship between the image resolution and the antireflection effect of external light, and the lower limit is the antireflection effect. If it is less than 100Å, the desired antireflection effect is not obtained, and it is difficult. On the other hand, the upper limit is determined from the viewpoint of resolution, and if it is more than 10,000Å, the resolution is remarkably lowered. Therefore, although the above range is defined as a practical range, it is preferably 500 to 1,200Å, more preferably 500 to 600.
Å, more preferably about 550Å.

In addition, when SiO ₂ ultrafine particles are used, a small amount of the SiO ₂ ultrafine particles gives a certain effect, but it is practically 0.01 to 1 mg / cm ² per unit area of the substrate.
It is preferably 0.1 to 0.3 mg / cm ² . The reason for the upper limit and the lower limit is that the lower limit is determined from the viewpoint of the antireflection effect and the upper limit is determined from the viewpoint of the resolution, as in the case of the above-mentioned particle size.

The additive is added for antistatic purposes, and the metal salt particles are selected from those having hygroscopicity, but preferably at least one of Group II and Group III of the periodic table. It is a salt of a metal element selected from among, practically, a hydrochloride, a nitrate, a sulfate and a carboxylate, and at least one of these salts is selected. Particularly desirable is at least one of the above salts of magnesium and aluminum.

The metal salts absorb water in the atmosphere and reduce the electric resistance of the substrate surface. On the other hand, since the conductive metal oxide particles themselves have conductivity, they are preferable to the above metal salts in order to reduce the resistance of the substrate surface. This is because at least one kind of oxides of tin, indium and altimone is practical as the metal oxide particles of this kind, and all of them are oxides forming the transparent conductive film. However, it goes without saying that other known conductive metal oxides such as those having a perovskite structure may be used. And, even if the practically fixed amount of such an additive is small, a certain effect is recognized, but 0.01 to 1.0 per unit area of the substrate.
0 mg / cm ² is preferable, more preferably 0.15 to 0.3 mg
/ cm ² . That is, the lower limit is restricted by the effect of reducing the conductivity of the substrate surface, and the upper limit is restricted by the adhesion strength to the substrate surface. That is, as the fixed amount increases, the resistance value decreases, but the adhesion strength decreases.

When a conductive component (a small amount component) and an antireflection functional component (a large amount component) are used in combination as ultrafine particles, the composition ratio varies somewhat depending on the production conditions, but the conductive component is 10% of the total weight of the ultrafine particles. It is preferable that the volume ratio is 0.1 or more (volume ratio is 0.1 or more). If this amount exceeds 50%, the antireflection function may be deteriorated, and it is necessary to adjust the amount to 50% or less. When the antireflection film composed of the ultrafine particles is used for the image display face plate, the conductive component is preferably transparent. This is because it does not interfere with the optical path.

It is not clear whether or not each component constituting the ultrafine particles forms a granular body depending on the type and performance of each component, but it is not clear that a certain amount of the small component is contained in the large component. In some cases, it is desirable that the average particle size of the granules formed by the minor components is 0.01 to 0.05 μm.

Representative examples of the antireflection functional component are SiO ₂ (silicon oxide) and MgO (magnesium oxide). On the other hand, typical examples of the conductive component are SnO ₂ (tin oxide), In ₂ O ₃
Examples include (indium oxide) Sb ₂ O ₃ (antimony oxide). In addition, you may use together 2 or more types of electroconductive components. The combination of both components is not limited to the combination between the above components, and the point is that each ultrafine particle can fulfill two kinds of functions. As described above, when the minor component is mixed with the major component, if the ultrafine particles composed of the major component are compared to the sea, the minute particles of the minor component mixed are present as if they were islands. Even if the ultrafine particles of the present invention are added with 10% or less by weight ratio of fine particles comprising a conductive component having an average particle size of 0.01 to 0.05 μm or a conductive component and an antireflection functional component, the ultrafine particles of the present invention The same effect as when only one is used can be obtained.

Ultrafine particles can be usually produced by using an apparatus for producing ultrafine particles using a metal component.
As such a manufacturing apparatus, arc, plasma (induction plasma, arc plasma), laser, electron beam, gas, etc. are used as a heat source to evaporate the antireflection functional component and the conductive component together, and then rapidly cool these raw material components to mutually There is a device that can be produced as ultrafine particles in a mixed form.

In the method for producing ultrafine particles by arc, the gas atmosphere in the system is oxygen gas or a mixed gas atmosphere of oxygen gas and an inert gas (helium gas, argon gas, etc.), and the ultrafine particle raw material and the raw material are inclined to this raw material. Alternatively, an arc is generated between the discharge electrode and the discharge electrode which are made to go straight to generate the oxide-mixed ultrafine particles of the raw material.

More specifically, an ultrafine particle producing apparatus using a laser described in US Pat. No. 4,619,691 and US Pat. No. 4,61
It is an ultrafine particle generator using an arc described in No. 0,718 and No. 4,732,369.

These devices may be operated according to a conventional method, and ultrafine particles can be produced by using these devices without any difficulty. If ultrafine particle raw material in which at least two or more kinds of materials are mixed is used, oxide mixed ultrafine particles of the raw material can be produced. In this case, the composition ratio of the mixed raw materials can be increased by mixing the materials having almost the same evaporation rate. It is possible to generate ultrafine particles having an oxide concentration close to.

Similar oxide ultrafine particles are produced whether the raw material is a metal or a metal oxide. At this time, if the mixed metal materials are easy to combine with each other, compound ultrafine particles tend to be produced, and if they are difficult to combine, respective oxide ultrafine particles tend to be produced. Since an oxide having conductivity and an oxide having an antireflection function do not usually combine, ultrafine particles in which the respective oxides are mixed are produced.

(Thin Film) The thin film is mainly composed of the above ultrafine particles. If the raw material component of the ultrafine particles is ultrafine particles (average particle size 0.01 to 0.05 μm), a mixture of the ultrafine particles of the present invention and the ultrafine particles is also within the scope of the present invention.

One layer is sufficient for the number of layers, but two layers may be used if desired. The thickness of this thin film is 0.
1 to 0.2 μm is preferable. In either case of one layer or two or more layers, the total film thickness is preferably 0.3 μm or less on average.

When the mixed ultrafine particles are used, the optimum ratio of the conductive component and the antireflection functional component in the thin film is the same as the optimum ratio described in the above-mentioned ultrafine particles. The thinning of the mixed ultrafine particles of the conductive component and the antireflection functional component may be performed by coating a proper amount of ultrafine particles on the substrate,
An even coat is ideal because of workability and economy. The depth of the valley formed between the ultrafine particles is preferably 0.05 to 0.2 μm. Further, the distance between the conductive components of the ultrafine particles in contact with each other is preferably 0.05 μm or less.

The thin film forming method is as follows: Disperse the ultrafine particles of the present invention or the raw material ultrafine particles in an alcohol solution in which Si (OR) ₄ (where R is an alkyl group) is dissolved, and display this solution as a light-transmitting image. After coating on the drawing plate, the coated surface is heated (baked) to form a film in which the ultrafine particle thin film obtained by hydrolyzing the Si (OR) ₄ is covered with SiO ₂ . Since SiO _{2 which} is a decomposition product of Si (OR) ₄ also enters the gap between the ultrafine particles and the substrate, it also serves as an adhesive.

As R of Si (OR) ₄ , an alkyl group having 1 to 8 carbon atoms, especially 5 is preferable. Also Si
The alcohol for dissolving (OR) ₄ increases the viscosity of the Si (OR) ₄ alcohol solution with an increase in the number of carbon atoms of R, and therefore the alcohol is appropriately alcohol so as not to become too high in consideration of workability. Should be selected. Alcohols generally usable include those having 1 to 5 carbon atoms. Further, in order to impart an antistatic effect to the above-mentioned thin film, a salt of a Group II or Group III metal of the periodic table may be added and used. Representative examples include aluminum hydrochloride, nitrate, sulfate and carboxylate.

Further, in order to accelerate the hydrolysis of Si (OR) _4, water and a mineral acid such as nitric acid as a solvent may be added to prepare a thin film coating solution.

As a method for coating the above alcohol solution on a substrate, it is practical to use a coating method consisting of a spinning method, a dipping method and a spray method, or a combination thereof, and to heat the coated surface at 50 to 200 ° C. Is.

For the antireflection film, it is practical to further laminate a transparent conductive film. In this case, the transparent conductive film serves as a base of the antireflection film, but its thickness is practically preferably 2,000 Å or less, more preferably 50 to 500 Å depending on the material constituting the film. Is. In addition, typical examples of the transparent conductive film include SnO ₂ and In ₂ O.
₃ and Sb ₂ O ₃ are formed of a conductive metal oxide film, and at least one of these transparent conductive metal oxides and hygroscopic metal salts is used as SiO ₂ film. It may be a thin film to which conductivity is imparted by being contained in the thin film.

The hygroscopic metal salt contained in the SiO ₂ thin film may be an inorganic acid salt such as hydrochloride, nitrate or sulfate or an organic acid salt such as carabonate. Preferred examples of these metal salts include salts of Group II metal elements represented by magnesium and salts of Group III metal elements represented by aluminum. These metal salts reduce the electric resistance of the panel surface by absorbing atmospheric moisture.

On the other hand, the conductive metal oxide is more preferable than the metal salt in order to reduce the electric resistance of the panel surface because it has conductivity itself. And S
The amount of the above-mentioned metal oxides and metal salts which impart the conductivity contained in the iO ₂ thin film is small, but some effect can be recognized, but the amount per unit area of the SiO ₂ thin film is 0.01 to
The amount is preferably 1.0 mg / cm ² , and more preferably 0.15 to 0.1.
It is 3 mg / cm ² . That is, the lower limit of this numerical value is limited by the effect of decreasing the conductivity, and the upper limit is limited by the strength of adhesion to the panel surface.

The underlying conductive film must have such a film thickness characteristic that it hardly affects the performance of the antireflection film formed thereon. It satisfies these conditions.

The step of forming the transparent conductive film will be described in detail. Due to the fact that the transparent conductive film is formed on the panel (image display face plate) of the cathode ray tube, a temperature (about 500 ° C. or less) at which the glass plate constituting the panel is not strained It is desirable to form it by (4), and any method may be used as long as it satisfies this. Hereinafter, a typical method for forming a transparent conductive film will be described.

I) As a method for directly forming a conductive metal oxide composed of at least one of SnO ₂ , In ₂ O ₃ and Sb ₂ O _{3 on} a glass panel, (1) using each metal oxide as a target A method of forming a metal oxide film on a panel surface by sputtering in a sputtering device facing the panel surface, and (1) a method of forming a metal oxide film on the panel surface by a known CVD method using an organic metal compound as a raw material. There is. As the organometallic compound in the case of the above (2), for example, when tin, indium or antimony is represented by M, its valence is represented by m, and an alkyl group is represented by R (where R = C _n H _{2n + 1} , practical N = 1 ~
5), an alkyl metal compound M (R) m or an alkoxy metal compound M (OR) m.
Specific examples include Sn (CH ₃ ) ₄ and Sn (OC ₂
H ₅ ) ₄ etc.

Ii) Next, a method for forming a transparent conductive film by incorporating a conductive substance into the SiO ₂ thin film will be specifically described.

The thin film of SiO ₂ is alkoxysilane Si
(OR) ₄ (However, R is an alkyl group, and practically n
= 1-5) can be easily obtained by hydrolysis. In the present invention, the transparent conductive metal oxide and the moisture-absorbing material described in detail in the invention of the cathode ray tube for achieving the first object for imparting conductivity to the alcohol solution of Si (OR) ₄ are provided. At least one additive of a metallic liquid having properties is applied, the solution is applied to the panel surface, and the applied surface is heated to decompose Si (OR) ₄ to form a SiO ₂ thin film. is there. Practically, the amount of the above additive is preferably 0.05 to 7 wt% with respect to the alcohol solution, and more preferably 1.0 to 2.0 wt%. Among the above additives, the transparent conductive metal oxide is not dissolved in the alcohol solution but merely dispersed, but in the case of a metal salt, a part or all is dissolved. In order to form a SiO ₂ thin film having good conductivity, it is desirable to disperse or dissolve this additive in the alcohol solution. From this point, a further dispersion medium such as acetylacetone such as acetylacetone may be added to the solution. Alternatively, it is more preferable to add ethyl cellosolve and water and a catalyst such as an inorganic acid such as nitric acid to facilitate the hydrolysis of Si (OR) ₄ .

The alcohol solvent that dissolves Si (OR) ₄ is preferably an alcohol that constitutes an alkyl group R, and the most practical example is tetraethoxysilane Si in which R is an ethyl group with n = 2. (OC ₂ H ₅ )
_{In 4} , when the solvent is ethyl alcohol.

As a method of applying the above-mentioned alcohol solution to the panel, a coating method including a spinning method, a depping method, a spray method or a combination thereof is used.

The heat treatment condition for heating the coated surface to decompose Si (OR) ₄ to form a SiO ₂ thin film is preferably 50 to 200 ° C., more preferably 160.
~ 180 ° C. This method of forming a conductive SiO ₂ thin film is advantageous over the method i) because it is processed at a relatively low temperature in this way. For example, when applied to a cathode ray tube such as a cathode ray tube, Therefore, it is suitable for a mass production process. Also, it goes without saying that it can be processed in the process of manufacturing a CRT before it is completed as a sphere.

In the method for obtaining an antireflection film by providing unevenness on the glass surface, the size of the unevenness is 0.1 μm.
It is desirable that the volume continuously changes in the depth direction at about m. As a result, the refractive index changes continuously and an antireflection effect is obtained. In this case, when SiO ₂ ultrafine particles having a uniform particle size without a particle size distribution are used, they adhere in an orderly manner, so that a film having a continuous volume change in the depth direction cannot be obtained. Is very few.

However, when ultrafine particles having a particle size distribution are used, appropriate voids can be provided, and as a result, the volume continuously increases in the depth direction and an antireflection effect is obtained. To be Also, by using a Si (OR) ₄ alcohol solution as a solution, Si (O) ₄
R) ₄ Alcohol solution in the alcohol solution sublimates values other than Si
Has the effect of firmly adhering the glass and the SiO ₂ ultrafine particles to form a film. Meanwhile Si (OR) ₄ acetylacetone to mix the alcoholic solution, acetone, ethyl alcohol has an effect of controlling the thickness of Si by diluting Si (OR) ₄ alcohol solution, precipitated.

Although a normal chemical ultrafine particle manufacturing method can naturally be applied to this, in this case, since the particles become uniform, in order to positively give a particle size distribution, a physical method such as an arc method is used. It is effective to devise to obtain ultrafine particles by the method. The conductive particles (In
A mixed system of O ₂ and SnO ₂ etc. and antireflection particles (SiO ₂ etc.) is effective, but it is not a mixed system of particles having different characteristics, but particles having both characteristics. If it is obtained (for example, Si-In-O-based particles), the conductivity is not lowered, and the antireflection is effectively achieved.

Next, the step of forming the antireflection film on the transparent conductive film as a base will be described in detail.

First, a method for dissolving and preparing alkoxysilane Si (OR) ₄ in alcohol will be described. All of Si (OR) _{4 as} a raw material and alcohol as a solvent form a base of the above-mentioned transparent conductive film. Since it is the same as the method of forming the SiO ₂ thin film described in the section (1), detailed description will be omitted.

In the same manner as in the above item ii), a particle size of 100 to 10,000 is added to an alcohol solution in which Si (OR) ₄ is dissolved.
The Å SiO ₂ fine particles are dispersed, but this dispersion amount is practically from the viewpoint of antireflection effect and image resolution.
0.1-10 wt% is preferable, and more preferably 1-3
wt%. And the dispersibility of SiO ₂ particles and Si
To improve the hydrolyzability of (OR) ₄ , water is added to the above solution as a dispersion medium such as ketones such as acetylacetone or ethyl cellosolve, and water and a catalyst such as nitric acid to facilitate hydrolysis. It is more preferable to add an inorganic acid such as

The above Si (OR) ₄ is hydrolyzed to S
It forms a thin film of iO ₂ and plays a role of fixing the SiO ₂ fine particles to the panel surface. When the alkyl group R is represented by the general formula C _n H _{2n + 1} , practical n is 1 to 1 5 and preferably an ethyl group of n = 2. The alcohol of the solvent that dissolves Si (OR) ₄ is preferably an alcohol having an alkyl group R. In the most practical example, R of alkoxysilane Si (OR) ₄ is an ethyl group of n = 2 and the solvent is a solvent. Is ethyl alcohol. Further, as a method of applying the alcohol solution of Si (OR) ₄ in which the SiO ₂ fine particles are dispersed onto the panel on which the underlying transparent conductive film is formed, the conductive Si described in the above section ii) is used.
As in the case of forming the O ₂ thin film, a coating method including a spinning method, a dipping method, a spray method, or a combination thereof is used.

Furthermore, the coated surface is heated to produce Si.
(OR) ₄ is decomposed to form a SiO ₂ thin film and dispersed S
The heat treatment conditions for coating and fixing the iO ₂ fine particles with this SiO ₂ thin film are preferably 50 to 200 ° C, and more preferably 160 to 180 ° C.

A thin film as an antireflection film material is formed by each of the above methods, but the heat treatment temperature can be formed at a relatively low temperature as in the forming method of the undercoat film ii) described above, so that it is particularly completed. It is convenient to form it on the panel surface of the cathode ray tube.

As described above, the antireflection film may have a fine (submicron-order) surface, but in the case of particles of uniform size such as ultrafine particles produced by a chemical method, it is difficult to form such an uneven surface. Funny Therefore, the present inventor decided to perform etching treatment after forming the thin film in order to surely form fine irregularities on the surface.

In this case, if a binder having an etching rate faster than that of the ultrafine particles is used, the binder is gradually removed from the surface more aggressively than the ultrafine particles in the etching solution, and as a result, the sub-reliability is surely ensured. An ultrafine particle film having micron-order irregularities can be obtained. The etching solution is an aqueous solution of sodium hydroxide or an aqueous solution of hydrogen fluoride, depending on various etching conditions.
However, sodium fluoride (for example, a 5% aqueous solution) is preferable because hydrogen fluoride easily removes ultrafine particles such as SiO ₂ in a short time and process control becomes difficult. Even if SiO ₂ is contained in the binder decomposition product using an aqueous sodium hydroxide solution, the binder is more positively dissolved and removed than the SiO ₂ ultrafine particles. (Ultrafine particle film utilization device) The device in which the thin film for the antireflection film is most effective is the image display face plate formed on the translucent substrate such as the thin film glass substrate, and further the cathode line incorporating this image display face plate. It is a tube.

When the mixed ultrafine particles are used to form a thin film, the function of the minor component continues to be utilized as the function of the main (major component) ultrafine particles. The function of the remaining ultra-fine ultrafine particles (mixed component) is that there is a distance between the ultrafine ultrafine particles when focusing on the adjacent ultrafine particles, but because of the extremely short distance that does not exceed the size of the ultrafine particles,
It is demonstrated by the tunnel effect.

In this case, the function of the component formed from a small amount of components and mixed in the ultrafine particles in the form of ultrafine particles is that the ultrafine particles existing in the adjacent ultrafine particles have a distance, but the ultrafine particles are present. Because of the extremely short distance that does not exceed the size of
The tunnel effect is exhibited in terms of conductivity. In this case, the major component inevitably forms due to its viscosity, and the roughness of the surface is mainly effective to achieve the low reflection function. With respect to the conductive component, conductivity is exhibited due to the tunnel effect. Therefore, the film strength is improved by reducing the number of peeled portions as compared with the laminate of each functional component. In addition, since the tunnel effect can be utilized compared to the case where ultrafine particles are made for each functional component and mixed, the connection between both functions can be improved.

If the main ultrafine particles are used as the antireflection function component, the roughness of the surface is mainly effective to achieve the low reflection function. With respect to the conductive component, conductivity is exhibited due to the tunnel effect. Therefore, the film strength is improved by reducing the peeling points (potential) as compared with the laminate of each functional component. In addition, the tunnel effect can be utilized compared to the case where ultrafine particles are prepared and mixed for each functional component, so that both functions can be maintained.

An arc is generated between the ultrafine particle raw material and the discharge electrode by using the gas atmosphere in the system as an atmosphere of oxygen gas or a mixed gas atmosphere of oxygen gas and an inert gas, and vapor is generated from the ultrafine particle raw material by the arc heat. And reacts with oxygen in the activated atmosphere gas to generate ultrafine oxide particles.

At this time, by using the ultrafine particle raw material in which at least two or more kinds of materials are mixed, it is possible to generate the oxide mixed ultrafine particle of the raw material. In this case, by mixing materials having substantially the same evaporation rate, oxide-mixed ultrafine particles having a composition ratio close to that of the mixed raw material can be generated.

The same raw material of metal or metal oxide produces similar oxide ultrafine particles. At this time, if the mixed materials are easy to combine with each other, compound ultrafine particles tend to be produced, and if they are difficult to combine, respective oxide ultrafine particles tend to be produced. Of these, the oxide having conductivity and the oxide having antireflection function may not be combined, and in that case, ultrafine particles in which the respective oxides are mixed are generated.

When the oxide-mixed ultrafine particles are applied to the surface of glass or a display tube to form a film, a film having two properties of conductivity and antireflection function is obtained. This film is subjected to etching treatment to form fine irregularities on the surface.

Thus, it becomes possible to form a single layer of the conductive antireflection film on the surface of the display tube at a low temperature.

Alternatively, in the case of a single layer of antireflection film (meaning no conductive film and no mixing of conductive particles), Si is used.
The SiO ₂ thin film formed by the hydrolysis of (OR) ₄ coats the uniformly dispersed SiO ₂ fine particles and fixes it on the surface of the glass body (substrate). This film is etched as described above. The uniformly dispersed SiO ₂ particles maintain the antireflection effect and the high resolution of the displayed image. Further, the SiO ₂ thin film contains at least one kind of additive, that is, a metal salt having a hygroscopic property and a conductive metal oxide, and the former is a heat treatment for hydrolyzing Si (OR) ₄ (this heat treatment is a film strength. Of which the hygroscopicity is improved), the hygroscopicity is maintained, and it has the effect of reducing the resistance value of the substrate surface without losing its performance.

The function of the conductive treatment is as follows. That is, the conductive metal oxide shows a decrease in the surface resistance value on the same principle as that of the so-called transparent conductive film, and the antistatic function is maintained due to the small surface resistance value.
As described above, the additive exhibits an antistatic effect, but the conductive metal oxide is superior to the metal salt in terms of reducing the surface resistance value of the substrate. In particular, oxides such as tin, indium and antimony are preferable in that the transparency of the film is good and the image resolution can be kept high. Some metal salts, unlike oxides, are fixed in the film in a dissolved state, and in such a case, the film has good transparency and has an effect of maintaining high resolution.

When the conductive film is used as the base film, the following functions are exhibited.

The underlying transparent conductive film is brought into close contact with the panel surface, thereby exerting the effect of reducing the electric resistance of the panel surface. A film composed of a metal oxide that itself has conductivity or a film in which a conductive metal oxide is dispersed in a SiO ₂ thin film shows a decrease in the surface resistance value on the same principle as a so-called transparent conductive film. As a result, the antistatic function is maintained.

On the other hand, in the case of a film in which a metal salt having a hygroscopic property is contained in the SiO ₂ thin film, the metal salt absorbs and retains water to impart conductivity.
It retains its hygroscopicity even after a heat treatment during hydrolysis of i (OR) ₄ (this heat treatment also improves the film strength), and has the effect of reducing the resistance value of the panel surface without losing its performance. doing.

As the additive contained in the SiO ₂ thin film, the conductive metal oxide is superior to the metal salt in terms of lowering the resistance value of the panel surface. In particular, oxides such as tin, indium and antimony are preferable in that the transparency of the film is good and the image resolution can be kept high. Some metal salts, unlike oxides, are fixed in the film in a dissolved state, and in such a case, the film has good transparency and has an effect of maintaining high resolution.

The reason why the front panel surface (image display face plate) of a cathode ray tube such as a Braun tube is charged is that a thin and uniform aluminum film 4 is vapor-deposited on the phosphor coated on the inner surface of the Braun tube. When a high voltage is applied to the aluminum film, a charging phenomenon occurs due to electrostatic induction on the front panel of the cathode ray tube when the high voltage is applied and cut off.

Si (OR) ₄ (wherein R is an alkyl group)
Alcohol solution in which is dissolved ultrafine particles (mainly SiO ₂
(Having an anti-reflection function) is dispersed and the solution is coated on a substrate, and then the coated surface is heated (baked) to form Si.
(OR) ₄ is decomposed to form a film in which the ultrafine particle film is covered with SiO ₂ . SiO _{2 which} is a decomposed product of Si (OR) ₄ enters the gaps between the ultrafine particles and the gaps between the ultrafine particles and the substrate and serves as an adhesive.

When the thin film formed by the above method is etched by a dry or wet method for an extremely short time (several seconds to several tens seconds), a SiO ₂ rich layer which is a decomposed product of the binder on the surface of the film is etched, and the ultrafine particles are separated. A minute etching groove is formed in the. In this way, minute irregularities at the level of ultrafine particles are formed on the entire surface of the film, which exhibits an antireflection function.

If a spin coating method, a dipping method, or a spraying method is used as a method for applying the above alcohol solution on a substrate, large-area treatment can be performed easily and can be formed at low cost. Furthermore, the etching after baking is also done with NaOH.
When the method of immersing in an aqueous solution is used, large area treatment is easy and the cost is low. Therefore, since the film is formed by ultrafine particles, minute irregularities are generated on the surface of the coating film, and there is a further antireflection effect. Further, since the antireflection film is formed by the coating method, an expensive vacuum vapor deposition device is not required, the area can be easily increased, and the cost can be reduced.

Since light reflection occurs at the interface where the refractive index suddenly changes, conversely, if the refractive index gradually changes at the interface, no reflection occurs. The above-mentioned heterogeneous film is a film having a refractive index distribution in the film thickness direction based on the above principle.

If there are irregularities smaller than the wavelength of light on the substrate, the individual irregularities can be regarded not as interfaces but as surfaces having an average refractive index corresponding to the volume fractions of the substrate and air. That is, the average refractive index n at the position of the depth x in the film thickness direction
_x is the volume fraction occupied by the substrate, v ( _X ), and the refractive index of the substrate is n.
_{Let S be} the refractive index of air and n _a be n _x = n _s · v ( _x ) + n _a
It is expressed as (1-v ( _x )). Therefore, when minute irregularities are formed and the volume fraction v ( _X ) of the substrate is continuously changed, the refractive index is also continuously changed, and a non-uniform film can be formed to prevent reflection.

When the ultrafine particle film is etched, irregularities having a size equal to or smaller than that of the ultrafine particles are formed, and the film becomes a heterogeneous film as in the case of the anterior function and becomes an effective antireflection film.

[0079]

Embodiments of the present invention will be described below with reference to the drawings.

On the surface of the front panel (glass face plate) of the cathode ray tube, the underlying transparent conductive film is formed as in Examples 1 to 4 shown in Table 1.

In the case of Example 1, the conductive film was made of SnO ₂ , and the film was formed by the CVD method under the following conditions.

Apparatus used: atmospheric pressure CVD apparatus Raw material organic tin compound: Sn (CH ₃ ) ₄ dopant: Freon gas carrier gas: N ₂ substrate temperature (glass face plate): 350 ° C. In the case of Example 2, in the SiO ₂ thin film The transparent conductive fine powder contains SnO ₂ fine powder, and the method for forming the film is as follows.

(1) Alkoxylane Si (OR) ₄ alcohol solution composition: Ethyl alcohol (C ₂ H ₅ OH) 88 cc Tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) 6 cc SnO ₂ transparent conductive material Powder 1.2 g Water (H ₂ O) 6 cc (2) Solution coating on glass face plate: Spinner 500 rpm (3) Coating film firing: 160 ° C., 30 minutes As the transparent conductive powder, the above SnO ₂ is used instead. Similar trials were made for those containing In ₂ O ₃ , Sb ₂ O _4, etc. alone or in combination, but the results were almost the same, so SnO ₂ powder was used as a typical example here.

In the case of Example 3, In ₂ O ₃ and SnO
_It is a film prepared by forming a composite target with ₂ (5 wt%) and depositing a mixture of In ₂ O ₃ and SnO ₂ on a glass face plate by high frequency sputtering, and by a high frequency sputtering method.

In the case of Example 4, aluminum nitrate Al (NO) was used as the hygroscopic metal salt in the SiO ₂ thin film.
_{3) 3} · 9H ₂ O in which was contained, the method of forming the film are as follows.

(1) Alkoxysilane Si (OR) ₄ alcohol solution composition: ethyl alcohol (C ₂ H ₅ OH) 88 cc Etraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) 6 cc Metal salt Al (NO ₃ ). ₃ · 9H ₂ O 1.2g water _{(H 2 O) 6cc (2} ) solution coating to the glass faceplate: spinner 500 rpm (3) coated film baking: 160 ° C., 30 minutes the metal salt of the aluminum nitrate Instead, AlCl ₃ , Ca (NO ₃ ) ₂ , Mg (NO ₃ ) ₂ , ZnC
l _2, etc. alone or have been similarly tried for those composite addition, since a substantially equivalent result, here is a representative example aluminum nitrate as described above.

Next, a thin film to be an antireflection film was formed on the underlying conductive film obtained as described above by the following method.

Tetraethoxysilane [Si (OC ₂ H ₅ )
₄ ] is dissolved in ethanol, and water (H ₂ O) for hydrolysis and nitric acid (HNO ₃ ) as a catalyst are added to prepare a solution. This alcohol solution has a particle size of 500-100
Fine particles of SiO ₂ sized to 0Å (grain shape is almost spherical)
1% by weight (wt)% is added. At this time, an appropriate amount of acetylacetone is added as a dispersion medium so that the particles are sufficiently dispersed.

The formulation solution shown in Table 1 above is dropped onto the underlying conductive film on the glass face plate, and further uniformly coated with a spinner.

Then, it is baked in air at 150 ° C. for about 30 minutes to decompose tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ]. The fine particles of SiO ₂ added to the alcohol solution are firmly fixed by a continuous uniform thin film of SiO ₂ formed by decomposition.

Next, various tests were carried out by immersing in a 5 wt% NaOH aqueous solution for about 15 seconds to carry out etching treatment, washing with water and drying.

[0092]

[Table 1]

The glass face plate on which this antireflection film is formed has 5
The light having a wavelength of 550 nm was made incident at an incident angle of °, the reflectance (the light intensity opposite to the light intensity) was measured, and the same reflected light intensity in the Al vapor-deposited film was set as 100 and shown as a percentage.
As shown in Table 1, the reflectance was 0.4% or less, and the reflectance was 1% or less in the visible light range of wavelength 450 to 650 nm. The spectrophotometer used is U-3400 manufactured by Hitachi, Ltd. (the same applies hereinafter). This value is a value that sufficiently satisfies the conditions required for a VDT (visual display terminal).

Next, the surface of the glass face plate laminated with the base conductive film and the antireflection film was strongly erased (Lion 50-50 manufactured by Lion Corporation) under the strong pressure (printing pressure 1
When the surface was rubbed uniformly 50 times with a cross-sectional area of kgf and eraser of about 18 × 10 mm), the reflectance was only shifted by 0.1% to 0.2%, and there was no problem in quality.

In the eraser test, the 60-degree specular glossiness (see JIS, K5400) before and after rubbing 50 times is measured.

The reason why the reflectance can be lowered in the glass face plate having the above antireflection film formed thereon will be described below.

FIG. 2 shows a cross section of the antireflection film. As shown in the figure, the outermost surface layer has irregularities formed by exposing ultrafine particles. The refractive index at the position indicated by A is the refractive index no of air, and its value is about 1. On the other hand, at the position indicated by B, the refractive index of the SiO ₂ ultrafine particles 1 is almost equal to the refractive index _ng of glass (SiO ₂ ) = 1.48 in the state of being clogged. In the uneven portion sandwiched between A and B, the refractive index is the volume fraction of SiO ₂ , that is, when a plate of a minute thickness cut by a plane parallel to the A and B planes is hypothesized, the entire volume of the plate It continuously changes according to the volume ratio of the SiO ₂ portion of the. Assuming that the refractive index at the C position slightly inside the A is n ₁ and the refractive index at the D position slightly outside the B is n ₂ , the glass surface on which this antireflection film is formed is The condition that the reflectance R is minimum is

[0098]

[Equation 1]

And from now on

[0100]

[Equation 2]

When the condition of is satisfied, antireflection performance is obtained.

Here, the value of n ₂ / n ₁ is determined by the shape of the unevenness of the film surface, but since the binder in the surface layer portion is removed by etching as described above, the unevenness due to the surface layer portion ultrafine particle group is increased. Can be formed to satisfy the equation approximately 1%
It is considered that the following low reflectance can be obtained.

Next, the reason why the antireflection film of the present invention retains high mechanical strength is because there is a SiO ₂ film formed by hydrolysis of Si (OR) ₄ as follows, which protects it. This is probably because it is a film.

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH → SiO ₂ + 2H ₂ O Next, the antistatic function shown at the bottom of Table 1 will be described. FIG. 3 shows the relationship between the surface charge decay time after the switch of the television receiver is turned off and the charge amount, and corresponds to Example No. in Table 1. In the comparative example shown for comparison, the voltage does not drop to 1 kV or less even after 200 seconds and has no antistatic function. Such a device absorbs dust and dust in the air and does not separate the dust, so that the screen becomes dirty and the image becomes very difficult to see.

Further, as a process for forming such an antireflection film, a completed sphere on which an underlying conductive film is formed is
All you have to do is to add commercially available SiO ₂ ultrafine particles to an existing Si (OR) ₄ alcohol solution, apply it, and bake it. There is no use of harmful chemicals such as hydrofluoric acid, and it can be manufactured safely and at low cost. You can The etching treatment can be achieved with a low-concentration NaOH aqueous solution, which is safe. Incidentally, SiO ₂
The ultrafine particles are not limited to the spherical shape, and may have an irregular shape.

SiO ₂ Si (OR) ₄ with ultrafine particles added
The application method of the alcohol solution is not limited to the spinning method shown in the above embodiment, but a dipping method or a coating method,
A spray method and a combination thereof may be used.

The baking temperature after coating is 50 to 200 ° C.
The degree is appropriate.

Although Sn (CH ₃ ) ₄ was used as a raw material for CVD in forming the underlying conductive film of Example 1, other alkyltin compounds Sn (R) ₄ or alkoxytin compounds Sn (OR) _{4 were used.} Needless to say, the same organic compound as tin can be used for indium and antimony in addition to tin. Also, the metal salts to be added are aluminum, calcium, magnesium,
Not limited to zinc salt, any salt may be used as long as it has hygroscopicity. When the transparent conductive powder such as tin, indium, and altimone of Example 2 is added, a SiO ₂ thin film having good conductivity is prepared at a relatively low temperature (50 to 500).
It is particularly preferable because it can be formed at (° C.).

Furthermore, in the formation of the antireflection film, an example in which R is an ethyl group was shown as Si (OR) ₄ , but as described above, when R = CnH _{2n + 1} , n = 1.
5 to 5 are preferable, and similar effects can be obtained when n = 1 and 3 to 8. As n becomes larger, the viscosity of the solution becomes slightly higher. Therefore, as the solvent, alcohol corresponding to the workability may be selected in consideration of workability.

The fifth embodiment will be described below. This example has a particle size distribution.

FIG. 4 is a particle size distribution of the SiO ₂ ultrafine particles used in this example, which has an average particle size of 450 nm and a fairly wide particle size distribution, and a specific surface area of 70 to 80 m ² / g.
It is. The ultrafine particles are dispersed in a 1 wt% Si (OR) ₄ alcohol solution + 50% acetylacetone solution, and applied on a glass substrate by spin coating.
It was baked at 0 ° C. for 30 minutes.

The composition of the coating solution is SiO ₂ ultrafine particles 1-2.
% By weight, the balance being Si (OC ₂ H ₅ ) ₄ and 50% acetylacetone, coated with a spinner of 600 rpm × 30 seconds, and then dried and baked at 160 ° C. for 30 minutes.

By using the ultrafine particles having the particle size distribution as in this example, a film having a proper number of pores was obtained. The reflection characteristic of this film measured after the etching treatment as described above is 0.0 in the visible light region (400 to 700 nm).
6 to 0.3%. A film having a transmittance of 90% or more can be obtained by applying a Si (OR) ₄ alcohol solution + 50% acetylacetone solution on this film and baking it.
According to this embodiment, there is an effect that a good antireflection film can be obtained by a simple method.

It is preferable to wash the surface of the glass substrate and preheat it to about 50 ° C. before forming the antireflection film.

Next, examples of use of mixed ultrafine particles will be described as Examples 6 to 10 with reference to FIG.

In this example, one layer of ultrafine particle thin film 5 is formed on the glass substrate 3. The ultrafine particle thin film is mainly composed of ultrafine particles 1, and each ultrafine particle 1 is a mixture of a conductive component 7 and an antireflection functional component 6. The conductive component 7 is, as it were, extremely small ultrafine particles and may be present outside the ultrafine particles 1. In this example, the ultrafine particles are not covered with the SiO ₂ thin film by removing the surface layer binder by etching, that is, the ultrafine particles are not exposed to the SiO ₂ coating and are left bare. A SiO ₂ filled portion (binder) 2 is provided in the gap between the ultrafine particles and the glass substrate 3.
Is formed. The SiO ₂ thin film 2 as a binder is made of Si (O
R) _{4 is} a calcination decomposition product.

In this example, SnO ₂ is used as the conductive component 7.
And SiO ₂ is used as the antireflection functional component 6. The volume ratio of SnO ₂ / SiO ₂ during film formation is 0.1 (1
0%) or more and 0.5 (50%) or less. In this case, the ratio of the conductive functional component in the film forming in the ultrafine particles is 1% or more and 50% or less in weight%. SiO
₂ Exclude thin film 4 for calculation.

Further, it is necessary that the distance between the ultrafine particles be such that the distance between the conductive components contained in the adjacent ultrafine particles is such that the so-called tunnel effect appears. . Such a distance is 0.05μ
m or less is preferable.

Further, since the average particle diameter of ultrafine particles (≈thickness of one thin film) is 0.1 μm or less, the thickness of the thin film is allowed to be 0.1 μm to 0.2 μm. The depth of the valley of the thin film formed between the particles is usually 0.05 μm to 0.2 μm due to the etching treatment. FIG. 2 shows these relationships, where a is the distance between the conductive components, b is the particle size of the ultrafine particles, and c is the depth of the valley.

Since SiO _{2 which} is a decomposition product of Si (OR) ₄ also enters the gap between the ultrafine particles and the thin film, it also serves as an adhesive.

Using the apparatus schematically shown in FIG. 5, Si: 80 wt% and 20 wt% S as a mixed ultrafine particle raw material were used.
nO ₂ and Sb {SnO ₂ ; 90 wt% and Sb; 10 wt
%) Compressed powder, argon gas + 30% oxygen gas as system gas atmosphere, argon 3 l / min as shield gas, argon + 30% oxygen gas 20 l / min as atmosphere introduction gas, and arc conditions of 150A-30V. To produce oxide-mixed ultrafine particles. The produced ultrafine particles are oxide-mixed ultrafine particles of SiO ₂ + SnO ₂ + Sb ₂ O ₃ , and the composition ratio is almost the same as that of the raw material 40: 9:
It was one. The specific surface area is 60 to 70 m ² / g,
The production amount is about 15 to 20 g / hour, and is about 6 as compared with the value when SiO ₂ ultrafine particles are produced using Si as an ultrafine particle raw material.
Microscopic observation showing that twice the amount produced was found that Sn was uniformly dispersed, and that SnO ₂ + Sb ₂ O ₃ ultrafine particles were finely dispersed in and around the amorphous SiO ₂ ultrafine particles. understood.

As described above, according to this embodiment, at least two or more kinds of ultrafine oxide particles can be produced in a substantially uniform mixture by using an arc heat source.

In addition, Ar + O ₂ induction plasma or arc plasma is used as a heat source for generating oxide-mixed ultrafine particles, and similar oxide-mixed ultrafine particles can be obtained by adding the mixed powder to this plasma. The oxide-mixed ultrafine particles are dispersed in a solvent and coated on a glass substrate,
A conductive antireflection film was formed.

An example in which the present invention is applied to the front panel surface (glass face plate) of a cathode ray tube is shown in FIG. 1 and below.

Tetraethoxysilane [Si (OC ₂ H ₅ )
₄ ] is dissolved in ethanol, and water (H ₂ O) for water addition and nitric acid (HNO ₃ ) as a solvent are added to prepare a solution. To the above alcohol solution, 1 g of ultrafine particles (particles having a substantially spherical shape) 1 sized in the same manner as in Example 1 were added. At this time, acetylacetone is added as a dispersion medium in an appropriate amount so that the particles are sufficiently dispersed.

Before adding the ultrafine particles 1, various additives shown in Table 2 were added to the above alcohol solution in predetermined amounts.

The formulation solutions of Table 2 were dropped on the glass face plate,
Furthermore, apply evenly with a spinner. Then 150
Baking in air at 30 ° C. for about 30 minutes decomposes tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ]. The ultrafine particles added to the alcohol solution are firmly fixed by a continuous uniform thin film of SiO ₂ formed by decomposition. 5 wt% N
The glass substrate is dipped in an aOH aqueous solution for about 15 seconds for etching, washed with water and dried to form irregularities on the glass face plate.

The cross section of the antireflection film thus formed was observed by a scanning electron microscope. As a result, it was confirmed that the antireflection film 13 having a uniform depth of 1,000Å ± 200Å and a pitch of 500Å was formed on the outermost surface. Been formed.

The binder 2 is a SiO ₂ portion formed by decomposition of tetraethoxysilane, and contains an antistatic component as an additive.

[0130]

[Table 2]

The glass face plate on which this antireflection film is formed has 5
As a result of measuring the reflectance by making light incident at an incident angle of °, as shown in Table 2, 0.5% or less at a wavelength of 500 nm,
As shown by the curve 1 in FIG. 6, the reflectance was 1% or less in the wavelength range of 450 to 650 nm. This value is a value that sufficiently satisfies the condition as a VDT (visual display terminal).

Then, the surface of the glass face plate having the antireflection film formed thereon was rubbed uniformly with an eraser [Lion Office Equipment Co., Ltd., trade name Lion 50-50] 50 times under a pressure of 1 kg. The rate is the intensity of Table 2 and the curve II of FIG.
As shown in, there was no problem in the product, only by increasing by 0.1 to 0.2%. For comparison, a similar test was performed on a glass face plate having a concavo-convex pattern formed by conventional etching. When the eraser was rubbed once, the reflectance was increased by 2%. The reflectance was exactly the same as that of the untreated glass face plate.

Next, the seventh embodiment will be described.

0.2 g of the ultrafine particles of the oxide obtained in Example 6 were dispersed in 1 g of nitric acid, and 5 g of the silicic acid ester alcohol solution, 5 g of acetylacetone and 0.1 g of dicarboxylic acid were added to this solution, and the mixture was stirred and dispersed. . This solution was dropped on a glass substrate, spin-coated at 600 rpm for 1 minute, spin-coated at 160 ° C. for 30 minutes, and then etched according to Example 6. The formed film had a 5 ° regular reflectance of 0.06% in the visible region of 400 to 700 nm and a surface resistance of 0.5 to 1 × 10 ⁷ Ω / mouth.

The surface resistance when a film was formed in the same manner as in the above-mentioned embodiment by using a mixture of materials produced by separately producing SiO ₂ ultrafine particles and SnO ₂ + Sb ₂ O ₃ ultrafine particles was used.
/ It was a mouth.

As described above, according to Examples 6 to 10, at least two or more kinds of oxide ultrafine particles can be produced in a substantially uniformly mixed form by using an arc heat source. Further, by using the oxide-mixed ultrafine particles, a film having a combined function of conductivity and antireflection can be formed by a single coating operation.

Further, as a heat source for generating the oxide-mixed ultrafine particles, Ar—O ₂ induction plasma or arc plasma is used, and the same oxide-mixed ultrafine particles can be obtained by adding the mixed powder to this plasma.

The eleventh embodiment will be described below. FIG.
FIG. 9 is a sectional view when an ultrafine particle film is formed on a glass substrate according to this example, and FIG. 9 is a sectional view after the ultrafine particle film is etched to form a fine uneven surface.

The binder composition used was ethanol 74.0.
7wt%, water 7.66wt%, isopropyl alcohol 8.43w
t%, ethyl silicate 7.51 wt%, methyl ethyl ketone 1.39 wt%, nitric acid 0.89 wt%, total 99.95 wt%
Becomes A mixture obtained by adding the same amount of acetylacetone to the total amount was used as a binder composition. Therefore, the final composition is 50% by weight of acetylacetone and 37.04w of ethanol.
t%, water 3.83wt%, isopropyl alcohol 4.22wt%,
Ethyl silicate 3.76 wt%, methyl ethyl ketone 0.70 wt
%, Nitric acid 0.45 wt%.

First, ethyl silicate [Si (OS
₂ H ₅ ) ₄ ] is dissolved in ethanol, and water, nitric acid (HNO ₃ ) as a thermal decomposition reaction accelerator, and isopropyl alcohol and acetylacetone as a drying rate adjusting agent for film formation are added to make a solvent. In addition to this, SiO ₂ ultrafine particles (average particle size of 40-
(50 nm) was added and dispersed sufficiently by ultrasonic vibration. The amount of ultrafine particles was 25 g per 1 liter of the solvent.

After dispersing the ultrafine particles, citraconic acid was further added and sufficiently dissolved. Citraconic acid helps reduce the amount of bubbles generated during film formation and increases transparency. The amount of citraconic acid was 20 g per 1 l of the solvent. After that, ultrasonic vibration was further applied to sufficiently disperse the ultrafine particles and sufficiently mix each component.

Next, this compounded solution was dropped onto the pretreated and washed soda glass plate surface (1100 × 100 mm, thickness 1 mm), and further uniformly applied with a spinner.

Then, it was baked in air at about 160 ° C. for about 45 minutes to decompose the ethyl silicate to form SiO ₂ .
The above-mentioned citraconic acid and the like remain in SiO ₂ generated by this thermal decomposition. SiO ₂ ultrafine particles are Si produced by thermal decomposition
It is firmly fixed on the glass substrate by the continuous thin film of O ₂ .

When the cross section of the ultrafine particle film thus formed was observed with an electron microscope, as shown in FIG. 7, a film having a film thickness of about 0.3 μm and SiO ₂ ultrafine particles densely observed was observed. Was done.

The glass plate with the ultrafine particle film formed as described above is immersed in a 5 wt% aqueous solution of chemical conversion soda (NaOH) for about 15 seconds. Then, from the surface of the ultrafine particle film, first, the SiO ₂ -based compound (binder changed) produced by thermal decomposition of ethyl silicate is dissolved. Then, in the case of ultrafine particles, minute irregularities are generated between the ultrafine particles as shown in FIG. 8, and an effective antireflection function is exhibited. Under these conditions, the SiO ₂ ultrafine particles themselves are not etched.

After forming this ultrafine particle film, light having a wavelength of 400 to 700 nm was made incident on the etched glass plate and the untreated glass plate at an incident angle of 5 °, and the reflectance was measured. Is shown in the curve IV.

In the entire wavelength region, the antireflection film of this example has a reflectance of about half or less that of the untreated glass plate and other examples of the present invention. Further, if it is represented by an integral value between wavelengths of 400 to 700 nm, the reflectance is reduced to about 1/3. Further, the transmittance between the wavelengths of 400 and 700 nm is about 92% for the untreated glass plate and about 87% for the glass plate on which the antireflection film of the present invention is formed, as an integrated value. Since it has low reflection and high transmittance, it is suitable as an antireflection film against VDT. Especially, the effect of keeping the transmittance high and reducing the reflectance is great.

In the above description, the ultrafine particles are mainly used by the physical process, but it is naturally suitable to use the ultrafine particles having a substantially uniform particle size produced by the chemical process.

[0149]

According to the present invention, it is possible to provide an antireflection film which can surely achieve the antireflection function even when applied to a large area at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a Braun tube to which the present invention is applied.

FIG. 2 is an enlarged cross-sectional view of a reflective film according to an example of the present invention.

FIG. 3 is a characteristic diagram showing an antistatic effect.

FIG. 4 is a particle size distribution chart of ultrafine particles.

FIG. 5 is an apparatus configuration explanatory diagram showing an example of an ultrafine particle manufacturing process.

FIG. 6 is a reflectance characteristic diagram of an example of the present invention and a comparative example.

FIG. 7 is a schematic cross-sectional view of a thin film before etching.

FIG. 8 is a schematic cross-sectional view of a thin film after etching.

[Explanation of symbols]

 1 ... Ultra fine particles, 2 ... Binder, 3 ... Glass substrate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kei Kawamura 3300 Hayano, Mobara-shi, Chiba Hitachi Mobara Plant, Inc. (72) Inventor Akira Triangle 3300 Hayano, Mobara-shi, Chiba Hitachi Mobara Plant, Ltd.

Claims (1)

[Claims] 1. An antireflection film for preventing reflection of external light, wherein a valley formed by a convex portion and a concave portion has a depth of 0.05 to 0.2 μm on the outer surface of the antireflection film. An antireflection film, wherein certain fine irregularities are formed, and the area of the convex portion forming the irregularities occupies 70% or more of the surface area of the outer surface.