JP2858821B2 - Anti-reflection film, its manufacturing method and image display face plate - Google Patents

Description

The present invention relates to an antireflection film, its production and its application,
In particular, the present invention relates to the use of an antireflection film using ultrafine particles which can effectively function as an antireflection film for an image display surface plate such as a cathode ray tube.

[Conventional technology]

Research on films that reduce the reflectance of glass surfaces (anti-reflection films) has long been used for lenses such as cameras and glasses. Currently, VDT (Visual Display
Terminal) is used as an anti-reflection filter for reducing reflected light. There are various types of antireflection films, and currently used ones are mainly multilayer films and heterogeneous films.

The multilayer film has a structure in which a low-refractive index substance and a high-refractive index substance are alternately laminated on a glass surface, and the antireflection effect is a total effect of optical interference between phases. Regarding the multilayer film, No.2 (19
64) pp. 243-284 (Physics of Thin Films2, (196
4) pp. 243 to 284).

A film having a refractive index distribution in the thickness direction of the film is referred to as a heterogeneous film. If the film has an average refractive index lower than that of the substrate glass, the film becomes an antireflection film. Generally, a glass surface is made porous in a heterogeneous film. After forming an island-shaped metal film on the glass surface, a method of forming unevenness by forming a non-uniform film by stutter etching to reduce the reflectance is described in Applied Fixture Letter No. 36 (1980). No.
727 to 730 (Appl. Phys. Lett, 36 (1980) P. 727-P.
730). Also, a method of immersing soda lime glass in an H ₂ SiF ₆ solution supersaturated with SiO ₂ to make the surface porous and reduce the reflectance is described in pages 28 to 34 of Solar Energy, No. 6, 1980. (Solar Energy6
(1980) pp. 28-34).

[Problems to be solved by the invention]

The multilayer film of the prior art is formed by sputtering,
Since the method is limited to the vacuum evaporation method and requires high-precision control of the film thickness, there is a problem that the cost is high and it is difficult to increase the area. The method of forming a heterogeneous film by sputter etching also has a problem that the cost is high and it is difficult to increase the area. In the method of immersing in an H ₂ SiF ₆ solution to make the surface porous and forming a heterogeneous film, fine irregularities are difficult to form, and a sufficient antireflection function does not occur. Further, there is a problem that the transmittance is reduced together with the reflectance because the unevenness is not sufficiently fine.

By the way, the present inventors have proposed to apply ultrafine particles to an anti-reflection film, but after further intensive studies, it is effective to apply sub-micron-order fine processing to the surface in order to exhibit the anti-reflection film function. Was obtained.

An object of the present invention is to provide an anti-reflection film capable of reliably achieving an anti-reflection function even when applied to a large area at low cost, and an image display face plate using the anti-reflection film.

[Means for solving the problem]

The antireflection film of the present invention is mainly composed of ultrafine particles. The ultrafine particles require a binder material because it is difficult to maintain the film formation by itself. The present invention first defines the exposed area of the binder and the ultrafine particles. That is, the outer surface exposed area of the ultrafine particles is 70% or more. In this case, the surface of the film naturally exposes the irregularities of the particles. In other words, the film has a shape in which the binder is removed, and as a result, the surface becomes fine (submicron order). The method for forming an antireflection film according to the present invention is characterized by performing an etching treatment to form the fine uneven surface.

Now, 70% of the area ratio is based on the fact that ultrafine particles are regarded as spheres of uniform particle size (that is, averaged) and geometrically obtained from a schematic plan view. 73% (πr ² / 4r ² ; r is the ultrafine particle diameter, the molecule is the ultrafine particle exposed area, and the denominator is the binder exposed area.) Binder space 1 surrounded by four particles in a plan view The ratio is calculated as the reciprocal of 73%, but it is almost 70% due to the actual particle dispersion and the relationship from plane to spherical conversion.
The percentage was specified as 70%. In addition, assuming close packing (three particles form one binder space) about 80%
Becomes more (Ultrafine particles) The average particle size of the superfine particles preferably applied to the present invention is 0.
1 μm or less. This is commonly referred to as submicron order fine particles.

Desirable particle size distribution is such that the largest peak is near the average particle size and that particle size accounts for about 50% or more of all particles,
The maximum particle diameter is about twice the average particle diameter, and the minimum particle diameter is about 1/2 of the average particle diameter. More preferably, the average particle size is 0.1 μm
Si with ultra-fine particles of SiO ₂ having the following particle size distribution
(OR) ₄ alcohol solution and acetyl acetone, acetone, at least two or more of the mixture of ethyl alcohol is accomplished by coating the glass surface.

The solution is preferably 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 of acetylacetone and acetone ethyl alcohol.

Note that if the average particle size exceeds 0.3 μm, light interference becomes a visual hindrance.
A solvent containing ultrafine particles having an average particle size distribution of 0.1 μm or less is coated on a glass surface, baked, and then an alcohol solution of Si (OR) ₄ (R is an alkyl group) and acetylacetone, acetone-ethyl alcohol. It is preferable to overcoat at least two or more liquid mixtures. Incidentally, such an antireflection film is particularly suitable for an image display tube.

Further, the present invention provides a composite granular material composed of two or more inorganic oxides, wherein two or more inorganic oxides are mixed alternately or one inorganic oxide is 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 inorganic oxides is an antireflection functional component and the rest is a conductive component. Further, the content of the conductive component is preferably at least 10 (wt)%.

The ultra fine particles (especially SiO ₂ ultrafine particles) the particle size (average particle diameter) is intended to be constrained by the relationship between the anti-reflection effect of the resolution and ambient light image, the lower limit as defined antireflection effect If the angle is smaller than 100 °, it is difficult to obtain the desired antireflection effect. On the other hand, the upper limit is determined from the viewpoint of the resolution, and if it is larger than 10,000 °, the resolution is significantly reduced. Accordingly, the above range is determined as a practical range, but is preferably 500 to 1,200 °, more preferably 500 to 600 °, and still more preferably about 550 °.

Also, when using SiO ₂ ultrafine particles, in its fixed amount is moderate effect even in a small amount is observed but practically a unit area of the substrate around 0.01 to 1 mg / cm ^2, preferably 0.1~0.3m
g / c 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 a hygroscopic property,
Preferably at least one of Group II and III of the periodic table
It is a salt of a metal element obtained from a seed, and is practically a hydrochloride, a nitrate, a sulfate, or a carboxylate, and at least one of these salts is selected. Particularly preferred are at least one of the above salts of magnesium and aluminum.

The metal salts absorb the moisture in the atmosphere and reduce the electric resistance of the substrate surface. On the other hand, since the conductive metal oxide has such conductivity, it is preferable to the above-mentioned metal salts in order to reduce the resistance of the substrate surface. Practical ones of this kind of metal oxide particles are at least one oxide of tin, indium and alimon, all of which are oxides constituting a transparent conductive film. However, it goes without saying that other well-known conductive metal oxides, for example, those having a perovskite structure may be used. And while such practical fixed amount of additive moderate effect even in a small amount is observed, preferably per unit area 0.01 to 1.0 mg / cm ² of substrate, more preferably, 0.15~0.3mg / cm ² It is. 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. In other words, as the fixed amount increases, the resistance value decreases,
On the contrary, the adhesion strength decreases.

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

It is not clear whether each component constituting the ultrafine particles according to the present invention forms a granular material in a certain form depending on the type of each component, performance, etc.,
In some cases, the minor component is included in the major component in the form of a granular material. In this case, the average particle size of the granular material formed by the minor component is desirably 0.01 to 0.05 μm.

Typical examples of anti-reflection functional components are SiO ₂ (silicon oxide) and Mg
O (magnesium oxide). On the other hand, typical examples of the conductive component are SnO ₂ (tin oxide) and In ₂ O ₃ (indium oxide) Sb ₂ O ₃
(Antimony oxide). Incidentally, two or more conductive components may be used in combination. The combination of the two components is not limited to the combination between the above components, but it is essential that each ultrafine particle can fulfill two functions. When a small component is mixed with a large component as described above, if the ultrafine particles composed of the large component are compared with the sea, the small particles of the mixed small component exist as if they were islands. Further, even when 10% or less by weight ratio of a conductive component having an average particle diameter of 0.01 to 0.05 μm or fine particles comprising a conductive component and an antireflection function component is added to the ultrafine particles of the present invention, only the ultrafine particles of the present invention are used. The same effect can be obtained.

The ultrafine particles used in the present invention can be usually produced using an apparatus for producing ultrafine particles using a metal component. Such a manufacturing apparatus uses a mark, plasma (induction plasma, arc plasma), laser, electron beam, gas, or the like as a heat source to evaporate the antireflection function component and the conductive component together, and then quenches the raw material component to quench it. An apparatus that can be produced as ultrafine particles in a form of being mixed with each other is exemplified.

In the method for producing ultrafine particles by an arc used in the present invention, the gas atmosphere in the system is an oxygen gas or a mixed gas atmosphere of oxygen gas and an inert gas (helium gas, argon gas, etc.), and the raw material of ultrafine particles and the raw material An arc is generated between the discharge electrodes that are oriented in the direction or at right angles to each other to generate oxide-mixed ultrafine particles of a raw material.

More specifically, an ultrafine particle producing apparatus using a laser described in U.S. Pat. No. 4,619,691 and an ultrafine particle generating apparatus using an arc described in U.S. Pat. Nos. 4,610,718 and 4,732,369.

These devices may be operated according to a conventional method, and the ultrafine particles according to the present invention can be produced by using these devices without any difficulty.

The use of an ultrafine particle material in which at least two or more materials are mixed can produce oxide-mixed ultrafine particles of the raw material. In this case, by mixing materials having substantially equal evaporation rates, the composition ratio of the mixed raw material can be increased. It is possible to produce oxide concentration ultrafine particles close to the above.

In addition, the same ultrafine oxide particles are produced regardless of whether the raw material is a metal or a metal oxide. At this time, when the mixed metal materials are apt to be combined, compound ultrafine particles tend to be produced, and when the mixed metal materials are difficult to be combined, respective oxide ultrafine particles tend to be produced. Since the oxide having conductivity and the oxide having an antireflection function are not usually compared with each other, ultrafine particles in which each oxide is mixed are generated.

(Thin Film) The thin film used in the present invention 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, but two layers may be used if desired. The thickness of this thin film is preferably from 0.1 to 0.2 μm. The total film thickness of one layer, two layers or more is preferably 0.3 μm or less on average.

When the mixed ultrafine particles are used, the optimum ratio between the conductive component in the thin film and the anti-reflection function English is the same as the optimum ratio described in the section of the ultrafine particles. The mixed ultrafine particles of the conductive component and the antireflection function component can be made into a thin film by coating an appropriate amount of ultrafine particles on a substrate, and further coating is ideal from the viewpoint of workability and diameter. . The depth of the valley formed between the ultrafine particles is preferably 0.05 to 0.2 μm. The distance between the conductive components of the contacting ultrafine particles is
Preferably it is 0.05 μm or less.

The method for forming a thin film includes dispersing 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 dispersing this solution on a translucent image display panel. After application, heat (fire) this application surface
To the Si (OR) ₄ SiO ₂ ultrafine particles film was hydrolyzed
Will be formed. Since SiO _{2, which} is a decomposition product of Si (OR) ₄ , enters the gap between the ultrafine particles and the substrate, it also serves as an adhesive.

In general, R of the above Si (OR) ₄ is preferably an alkyl group having 1 to 8 carbon atoms, especially 5 alkyl groups. Alcohol for dissolving Si (OR) ₄ increases the number of carbon atoms of R as described above.
Since the viscosity of the Si (OR) ₄ alcohol solution increases, the alcohol may be appropriately selected in consideration of workability so that the viscosity does not become too high. Generally, alcohols having 1 to 5 carbon atoms are used as home alcohols.

Further, a salt of a metal of Group II or III of the periodic table may be added to the thin film for imparting an antistatic effect. Representative examples include aluminum hydrochloride, nitrate, sulfate and carboxylate.

Further, water may be added to promote the hydrolysis of Si (OR) ₄ and a mineral acid such as nitric acid may be added as a solvent to prepare a thin film coating solution.

As a method of applying the alcohol solution on the substrate,
It is practical to use a coating method comprising a spinning method, a dipping method, a spray method or a combination thereof, and to heat the coated surface at 50 to 200 ° C.

It is practical to further laminate a transparent conductive film on the antireflection film. In this case, the transparent conductive film serves as a base of the anti-reflection film, but the film thickness is practically preferably 2,000 mm or less, more preferably 50 to 500 mm, depending on the material constituting the film. is there. Typical examples of the transparent conductive film include a conductive metal oxide film made of at least one of SnO ₂ , In ₂ O ₃ and Sb ₂ O _3. It may be a thin film provided with conductivity by incorporating at least one kind of a conductive metal oxide and a metal salt having hygroscopicity into the SiO ₂ thin film.

The metal salt having hygroscopicity contained in the SiO ₂ thin film,
It may be an inorganic acid salt such as hydrochloride, nitrate or sulfate, or an organic acid salt such as carabonate. Preferable 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, a conductive metal bowl is more preferable than a metal salt in order to lower the electric resistance of the panel surface because it has conductivity itself. The amount of the metal oxide and the metal salt imparting such conductivity contained in the SiO ₂ thin film is small, and a certain effect is recognized.
O ₂ per unit area 0.01 to 1.0 mg / cm ² of the thin film, and more preferably from 0.15~0.3mg / 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 a thickness and characteristics that have little effect on the performance of the antireflection film formed thereon, and the film of the present invention described above is It satisfies the condition.

The step of forming the transparent conductive film will be described in detail. In terms of forming on the panel (image display surface plate) of the cathode ray tube, the transparent conductive film is formed at a temperature (about 500 ° C. or lower) at which the glass plate constituting the panel is not strained It is preferable to use any method as long as it satisfies this. Hereinafter, a typical method for forming a transparent conductive film will be described.

i) A method of 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 includes (1) a method in which a sputter device is used with each metal oxide as a target. And a method of forming a metal oxide film on the panel surface by sputtering, and (1) well-known CVD using an organometallic compound as a raw material.
There is a method of forming on a panel surface by a method. Examples of the organometallic compound in the case of the above (2) include tin,
M for indium or antimony, m for its valence,
When an alkyl group is represented by R (where R = CnH _{2n + 1}
And, practically, n = 1 to 5), the alkyl metal compound M
(R) m or an alkoxy metal compound M (OR) m. A concrete example is Sn (CH
₃ ) ₄ , Sn (OC ₂ H ₅ ) ₄ and the like.

ii) Next, a method of forming a transparent conductive film by adding a conductive substance to 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, practically easily obtained by hydrolyzing n = 1 to 5). In the present invention,
The transparent conductive metal oxide and the metal having hygroscopicity described in detail in the invention of the cathode ray tube for achieving the first object in order to impart conductivity to the alcohol solution of Si (OR) ₄ At least one additive of a liquid is added, the solution is applied to the panel surface, and the applied surface is heated to form a Si (O
R) Decompose ₄ to form a SiO ₂ thin film. The amount of the above additives is practically 0.05 to
It is preferably 7 wt%, more preferably 1.0 to 2.0 wt%.

Among the additives, the transparent conductive metal oxide is merely dispersed without dissolving in the alcohol solution,
In the case of a metal salt, part or all dissolves. 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, and from this point, as a dispersion medium in the solution,
For example, it is more preferable to add a ketone such as acetylacetone or ethyl cellosolve and to add water and an inorganic acid such as nitric acid as a catalyst in order to facilitate hydrolysis of Si (OR) ₄ .

The alcohol solvent for dissolving the Si (OR) ₄ is desirably an alcohol in which the alkyl group R is a constituent. As the most practical example, tetraethoxysilane Si (OC _{2) in} which R is an n = 2 ethyl group H ₅ ) _4, where the solvent is ethyl alcohol.

As a method of applying the alcohol solution to the panel, a spinning method, a dipping method, a spray method, or a combination method of these methods is used.

Heat treatment conditions for heating the coated surface to decompose Si (OR) ₄ to form a SiO ₂ thin film are preferably 50 to 200 ° C., and more preferably 160 to 180 ° C. This method of forming a conductive SiO ₂ thin film is more advantageous than the above-mentioned method i) because of the treatment at such a relatively low temperature. 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 of obtaining an antireflection film by providing irregularities on the glass surface, it is desirable that the irregularities have a size of about 0.1 μm and that the volume continuously changes in the depth direction. Thereby, the refractive index changes continuously, and an antireflection effect is obtained. In this case, when ultrafine particles of SiO ₂ having a uniform particle size without a particle size distribution are used, they adhere orderly, so that a film whose volume continuously changes in the depth direction cannot be obtained. The prevention effect is very small.

However, when ultrafine particles having a particle size distribution are used, appropriate pores can be provided, so that the volume increases effectively continuously in the depth direction and an antireflection effect can be obtained. In addition, by using a Si (OR) ₄ alcohol solution as the solution, at around 150 ° C., the substance values other than Si in the Si (OR) ₄ alcohol solution sublimate, Si precipitates to form a film, and the glass and SiO ₂ This has the effect of firmly adhering the fine particles. On the other hand, Si
(OR) ₄ acetylacetone to mix the alcoholic solution, acetone, ethyl alcohol and dilute the Si (OR) ₄ alcohol solution, the effect of controlling the thickness of the Si to be precipitated.

The present invention can naturally be applied to a normal chemical ultrafine particle manufacturing method, but in this case, the particles become uniform, and therefore, in order to positively impart a particle size distribution, a physical method such as an arc method is used. It is effective to devise to obtain ultra fine particles. It is to be noted that a mixed diameter of conductive particles (such as InO ₂ and SnO ₂ ) and antireflection particles (such as SiO ₂ ) is effective as ultrafine particles. If particles that have both characteristics can be obtained (e.g., Si-In
-O-based particles) There is no decrease in conductivity, and antireflection is effectively achieved.

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

First, the method of dissolving and adjusting alkoxysilane Si (OR) ₄ in alcohol is described.
₄ and all of the alcohol as the solvent are the same as the method of forming the SiO ₂ thin film described in the section ii) for forming the underlayer of the transparent conductive film, and a detailed description thereof will be omitted.

In the same manner as in the above item ii), SiO ₂ fine particles having a particle size of 100 to 10,000 ° are dispersed in an alcohol solution in which Si (OR) ₄ is dissolved, and the amount of dispersion is in terms of antireflection effect and image resolution. Therefore, practically, it is preferably 0.1 to 10% by weight, more preferably 1 to 3% by weight. Then, in order to improve the dispersibility of the SiO ₂ fine particles and the hydrolyzability of Si (OR) ₄ , a ketone such as acetylacetone or ethyl cellosolve is further added to the above solution as a dispersion medium, and the hydrolysis is facilitated. It is more preferable to add an inorganic acid such as, for example, nitric acid as the water and catalyst for this purpose.

The above Si (OR) ₄ undergoes hydrolysis to form a SiO ₂ thin film and plays a role of fixing the SiO ₂ fine particles on the panel surface. The above alkyl group R is represented by the general formula CnH _{2n + 1.} Then, practical n is 1 to 5, preferably n = 2
Is an ethyl group. The alcohol of the solvent for dissolving the Si (OR) ₄ is desirably an alcohol having an alkyl group R. The most practical example is an alkoxysilane Si (OR)
_This is the case where R of ₄ is an ethyl group where n = 2 and the solvent is ethyl alcohol.

The method of applying the alcohol solution of Si (OR) ₄ in which the SiO ₂ fine particles are dispersed on the panel on which the underlying transparent conductive film is formed includes the method of forming the conductive SiO ₂ thin film described in the above item ii). Similarly to the above, a coating method comprising a spinning method, a dipping method, a spray method or a combination thereof is used.

Furthermore, by decomposing Si (OR) ₄ by heating the coated surface to form a SiO ₂ thin film, dispersed SiO ₂ particles to the SiO ₂
The above heat treatment conditions when coating and fixing with a thin film are 50
The temperature is preferably from 200 to 200 ° C, more preferably from 160 to 180 ° C.

Although a thin film as an anti-reflection film material is formed by each of the above methods, the heat treatment temperature can be formed at a relatively low temperature in the same manner as the above-mentioned method of forming the base film ii). It is convenient to form it on the panel surface.

As described above, the antireflection film may have a fine (submicron order) surface, but it is difficult to form such a concavo-convex surface in the case of particles of uniform size such as ultrafine particles by a chemical manufacturing method. The inventor of the present invention has decided to perform an etching process after forming the thin film in order to surely provide fine irregularities on the surface.

In this case, if a binder having an etching speed higher than that of the ultrafine particles is used, the binder will be more gradually removed from the surface in the etching liquid than the ultrafine particles. An ultra-fine particle film having irregularities is obtained. The etching solution is an aqueous solution of sodium hydroxide or an aqueous solution of hydrogen fluoride depending on various etching conditions. However, since hydrogen fluoride easily removes even ultra-fine particles such as SiO _{2 in a} short time and the process control becomes difficult, the method of sodium hydroxide (for example, a 5% aqueous solution) is preferable. Even if SiO ₂ is contained in the binder fired decomposition product using an aqueous sodium hydroxide solution, the binder will be dissolved and removed more aggressively than the SiO ₂ ultrafine particles.

(Ultrafine Particle Film Utilizing Apparatus) An apparatus in which the thin film according to the present invention exhibits the most effect is an image display face plate formed on a light-transmitting substrate such as the above-mentioned thin glass substrate, and further a cathode ray tube incorporating the image display face plate It is.

[Action]

When thinning is performed with the mixed ultrafine particles, the function of the small component continues to be used as the function of the main (large component) ultrafine particle.
The function of the remaining ultrafine particles (mixed components) is exhibited by the tunnel effect because there is a distance between the 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. You.

In this case, the function of the component formed from the small amount of components and mixed in the form of ultrafine particles in the ultrafine particles is that the distance between the ultrafine particles present in the adjacent ultrafine particles is large, but the size of the ultrafine particles Since the distance is extremely short, the tunnel effect is exhibited in terms of conductivity. In this case, the major component necessarily achieves low reflectivity due to its surface roughness, which is inevitably formed from its viscosity. The conductive component exhibits conductivity by a tunnel effect. Accordingly, the film strength is improved by reducing the number of peeled portions as compared with the laminate of each functional component. In addition, the tunnel effect can be used as compared with the case where ultrafine particles are formed and mixed for each functional component, so that both functions can be continuously improved.

If the main ultrafine particles are used as the anti-reflection function component, the surface roughness is mainly effective to achieve the low reflection function. The conductive component exhibits conductivity by a tunnel effect. Therefore, the film strength is improved by reducing the number of peeled portions (potential) as compared with the laminate of each functional component. In addition, both functions can be maintained because the tunnel effect can be utilized as compared with the case where ultrafine particles are formed and mixed for each functional component.

The gas atmosphere in the system is an oxygen gas or a mixed gas atmosphere of an oxygen gas and an inert gas, and an arc is generated between the ultrafine particle raw material and the discharge electrode. It reacts with oxygen in the oxidized atmosphere gas to generate ultrafine oxide particles.

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

In addition, the same ultrafine oxide particles are produced regardless of whether the raw material is a metal or a metal oxide. At this time, when the mixed materials are apt to be combined, compound ultrafine particles tend to be generated, and when the mixed materials are difficult to be compounded, respective oxide ultrafine particles tend to be generated. Among them, the oxide having conductivity and the oxide having an antireflection function may not be combined, and in that case, ultrafine particles in which each oxide is mixed are generated.

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

Thus, a conductive anti-reflection film can be formed on the surface of the display tube at a low temperature.

As another method, in the case of a single anti-reflection function film (meaning no conductive film and no conductive particles mixed), a SiO ₂ thin film formed by hydrolysis of Si (OR) ₄ is uniformly dispersed in Si.
O ₂ fine particles are coated and fixed on the surface of the glass body (substrate). This film is subjected to an etching process as described above. The anti-reflection effect and high resolution of the displayed image are maintained by the uniformly dispersed SiO ₂ fine particles. Further, the SiO ₂ thin film contains an additive, that is, at least one of a metal salt having hygroscopicity and a conductive metal oxide. The former is a heat treatment at the time of hydrolysis of Si (OR) ₄ (this heat treatment is a film strength). This also has the effect of reducing the resistance value of the substrate surface without losing its performance even after passing through.

The function by the conductive treatment is as follows. That is, the conductive metal oxide exhibits a decrease in surface resistance based on the same principle as a so-called transparent conductive film, and the antistatic function is maintained due to the small surface resistance. As described above, the additive of the present invention exhibits an antistatic effect, but the conductive metal oxide is superior to the metal salt in terms of lowering the surface resistance 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 resolution of an image 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 following function is exhibited when a conductive film is used as a base film.

The base transparent conductive film adheres to the panel surface,
It has the effect of reducing the electrical resistance of the panel surface.
A film composed of a metal bowl having conductivity itself or a film in which conductive metal oxide is dispersed in a SiO ₂ thin film has a decrease in surface resistance based on the same principle as a so-called transparent conductive film. Thereby, 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 a SiO ₂ thin film, conductivity is imparted by absorbing and holding moisture by the metal salt, and hydrolysis of Si (OR) ₄ is performed. Even after heat treatment (this heat treatment also improves the film strength), moisture absorption is maintained, and has the effect of reducing the resistance value of the panel surface without losing its performance.

The additive contained in the SiO ₂ thin film is superior to the metal salt in the conductive metal oxide method 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 resolution of an image can be maintained 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 surface plate) of a cathode ray tube such as a cathode ray tube is charged is that a thin and uniform aluminum film 4 is deposited on a phosphor coated on the inner surface of the cathode ray tube. When a high voltage is applied to the film, a charging phenomenon is caused by electrostatic induction on the front panel of the cathode ray tube when the voltage is applied and when the film is cut off.

Ultrafine particles (mainly those having an antireflection function such as SiO ₂ ) are dispersed in an alcohol solution in which Si (OR) ₄ (where R is an alkyl group) is dissolved, and after applying this solution on a substrate,
The coated surface is heated (fired) to decompose the Si (OR) ₄ to form a film in which the ultrafine particle film is covered with SiO ₂ . SiO _{2, which} is a decomposition product of Si (OR) ₄ , enters the gaps between the ultrafine particles and the gap between the ultrafine particles and the substrate to serve as an adhesive.

When the thin film formed by the above method is etched for a very short time (several seconds to several tens seconds) by dry or wet,
A layer of SiO ₂ rich as a binder decomposed substance on the film surface is etched, and a minute etching groove is formed between the ultrafine particles. Thus, fine irregularities at the level of ultrafine particles are formed on the front surface of the film, and exhibit an antireflection function.

As a method of applying the alcohol solution on the substrate,
If a spin coating method, a dipping method, or a spray method is used, large-area processing can be easily performed and can be performed at low cost. Furthermore, when the etching after firing is performed by immersing in a NaOH aqueous solution, large-area processing is easy and the cost is low. Therefore, since the film is formed by the ultrafine particles, minute irregularities are generated on the surface of the coating film, and a further antireflection effect is obtained. Further, since the reflection film is formed by the coating method, an expensive vacuum deposition apparatus is not required, and the area can be easily increased, and the cost can be reduced.

Light reflection occurs at the interface where the refractive index changes abruptly. Conversely, if the refractive index changes gradually at the interface, no reflection occurs. A film having a refractive index distribution in the film thickness direction based on the above principle is the above-mentioned heterogeneous film.

If the substrate has irregularities smaller than the wavelength of light on the substrate, the individual irregularities cannot be regarded as interfaces, but can be regarded as surfaces having an average refractive index corresponding to the volume fraction of the substrate and air. That is, the average refractive indices n _x at the position of the thickness direction depth x is the volume fraction occupied by the substrate v _(x), a n _s the refractive index of the substrate, and the refractive index of air and n _a, n _{x = n s · v (x)} + n a (1-v (x))
It is expressed as Accordingly, 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 the film becomes an inhomogeneous film, thereby preventing 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 prior art, and becomes an effective antireflection film.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First on the front panel surface (glass face plate) of the CRT
A base transparent conductive film is formed as in Examples 1 to 4 shown in the table.

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

Applicable equipment: Normal pressure CVD equipment Raw material organotin 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, the transparent conductive fine particles are contained in the SiO ₂ thin film. The powder contains SnO ₂ fine powder as a powder, and the method of forming the film is as follows.

(1) Alcohol silane Si (OR) ₄ alcohol solution composition: ethyl alcohol (C ₂ H ₅ OH) 88 cc Etraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) 6 cc SnO ₂ transparent conductive fine powder 1.2 g Water (H ₂ O) 6cc (2) Solution coating on glass face plate: Spinner 500rpm (3) Coating film baking: 160 ° C, 30 minutes As transparent conductive powder, use In instead of SnO ₂ as above.
Similar trials were carried out for those in which ₂ O ₃ , Sb ₂ O _3, etc. were added alone or in combination, but the results were almost the same. Therefore, here, SnO ₂ powder was used as a representative example as described above.

In the case of Example 3, a composite target of In ₂ O ₃ and SnO ₂ (5 wt%) was prepared, and a mixture of In ₂ O ₃ and SnO ₂ was deposited on the glass surface by high frequency sputtering. By the sputter method.

In the case of Example 4, the SiO ₂ thin film contains aluminum nitrate Al (NO ₃ ) ₃ .9H ₂ O as a metal salt having hygroscopicity, and the method of forming the film is as follows.

(1) Composition of alcohol solution of alkoxysilane Si (OR) ₄ : 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 on glass face plate: Spinner 500rpm (3) Coating film baking: 160 ° C, 30 minutes The metal salt is AlCl instead of aluminum nitrate. ₃ , Ca (NO ₃ ) ₂ , Mg (NO ₃ ) ₂ , ZnCl _2, etc. singly or compositely added were tried in the same manner, but the results were almost the same. Aluminum was used as a representative example.

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

Tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] is dissolved in ethanol, and a solution is prepared by adding water (H ₂ O) for hydrolysis and nitric acid (HNO ₃ ) as a catalyst. To this alcohol solution, 1% by weight (wt)% of SiO ₂ particles (particle diameter is substantially spherical), sized to 500 to 1000 °. At this time, an appropriate amount of acetylacetone is added as a dispersion medium so that the particles are sufficiently dispersed.

The compounding solution shown in Table 1 was dropped on the underlying conductive film on the glass face plate, and further uniformly applied with a spinner.

Thereafter, the mixture is calcined at 150 ° C. for about 30 minutes in the air to decompose Etraethoxysilane [Si (OC ₂ H ₅ ) ₄ ]. SiO ₂ particles of SiO ₂ were added to the alcohol solution, which Deki by decomposition
Is firmly fixed by a continuous and uniform thin film.

Next, it was immersed in a 5 wt% NaOH aqueous solution for about 15 seconds to perform an etching treatment, washed with water and dried, and subjected to various tests.

Light having a wavelength of 500 nm is incident on the glass face plate on which the antireflection film is formed at an incident angle of 5 °, and its reflectance (direct opposite light intensity) is measured.
As a result, as shown in Table 1, 0.4%
Hereinafter, the reflectance was 1% or less in the visible light range of wavelength 450 to 650 nm. The spectrophotometer is U-34 manufactured by Hitachi, Ltd.
00 is used (the same applies hereinafter). This value sufficiently satisfies the conditions required for a VDT (visual display terminal).

Next, the surface of the glass face plate on which the underlying conductive film and the anti-reflection film are laminated is strongly erased (Lion 50-50, a product name of Lion Office Equipment Co., Ltd.) and strongly applied (printing pressure 1 kgf, cross-sectional area of the eraser is After rubbing 50 times uniformly (approximately 18 × 10 mm), the reflectance only shifted by about 0.1% to 0.2%, and there was no problem in quality.

In the rubber erasing test, a 60-degree specular gloss (see JIS, K5400) before and after rubbing 50 times is measured.

Next, the reason why the reflectance can be reduced in the glass face plate having the above-described anti-reflection film formed thereon will be described.

FIG. 2 shows a cross section of the antireflection film. The outermost surface layer as shown in FIG. The refractive index at the position indicated by A is the refractive index of air.
At n ₀ , its value is about 1. On the other hand, at the position shown in B, Si
With the O ₂ ultrafine particles 1 packed, the refractive index is almost equal to the refractive index of glass (SiO ₂ ) n _g = 1.48. In the concave and convex portion sandwiched between A and B, the refractive index is the volume fraction of SiO ₂ , that is, the entire volume of the plate when imagining a plate with a small thickness cut by a plane parallel to the A and B planes. Changes continuously according to the ratio of the volume of the SiO ₂ portion to the total. Assuming that the refractive index at a position C slightly inside from A is n ₁ and the refractive index at a position D slightly outside from B is n ₂ , the refractive index at the glass surface on which this antireflection film is formed is n ₁ . The condition under which the reflectance R becomes minimum is: And from now on, When the above condition is satisfied, antireflection performance can be obtained.

Here, the value of n ₂ / n ₁ is determined by the shape of the irregularities on the film surface, but since the binder in the surface layer is removed by etching as described above, the irregularities due to the ultrafine particles in the surface layer are calculated by the above equation. Can be approximately satisfied, and a low reflectance of 1% or less can be obtained.

Next, the reason that the antireflection film of the present invention has high mechanical strength is that an SiO ₂ film formed by hydrolyzing Si (OR) ₄ exists as follows, and this serves as a protective film. It is thought that it is.

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH → SiO ₂ + 2H ₂ O Next, a description will be given of the antistatic function that wets the bottom row of Table 1. FIG. 3 shows the relationship between the surface charge decay time and the charge amount of the television receiver after the switch is turned off.
Corresponds to Example No. in Table 1. The comparative example shown for comparison does not become 1 kV or less even after 200 seconds, and has no antistatic function. In such a thing, dust in the air,
Since the dust is absorbed and not released, the screen becomes dirty and the image becomes very difficult to see.

Further, as a process for forming such an anti-reflection film, a completed sphere on which an underlying conductive film is formed is added to an existing Si.
(OR) It is only necessary to add commercially available SiO ₂ ultrafine particles to a ₄ alcohol solution, apply and bake it. There is no use of harmful chemicals such as hydrofluoric acid, and it can be manufactured safely and at low cost. It is safe. The SiO ₂ ultrafine particles are not limited to a spherical shape, but may be an irregular shape.

The method of applying the SiO (OR) ₄ alcohol solution to which the SiO ₂ ultrafine particles are added is not limited to the spinning method described in the above embodiment, but may be a dipping method, a coating method, a spray method, or a combination thereof.

The firing temperature after application is suitably about 50 to 200 ° C.

Further, Sn (CH ₃ ) ₄ was used as a raw material for CVD at the time of forming the underlying conductive film in Example 1 above, but other alkyl tin compounds Sn (R) ₄ or alkoxy tin compounds Sn were used.
(OR) ₄ may be used, and it is needless to say that the same organic compounds as tin can be used for indium and antimony in addition to tin. Also, the metal salt to be added is not limited to aluminum, calcium, magnesium, and zinc salts.
Any material may be used as long as it has hygroscopicity. It is particularly preferable to add the transparent conductive powder such as tin, indium, and antimony of Example 2 because a SiO ₂ thin film having good conductivity can be formed at a relatively low temperature (50 to 500 ° C.).

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

The fifth embodiment will be described below. In this example, a viscosity distribution is given.

FIG. 4 shows the particle size distribution of the SiO ₂ ultrafine particles used in this example. The average particle size is 450 nm, the particle size distribution is fairly wide, and the specific surface area is 70 to 80 m ² / g. . These ultrafine particles were dispersed in a 1 wt% Si (OR) ₄ alcohol solution + 50% acetylacetone solution, applied on a glass substrate by spin coating, and then baked at 160 ° C. for 30 minutes.

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

By using the ultrafine particles having a particle size distribution as in this example, a film having an appropriate pore was obtained. The reflection characteristic of this film measured after performing the above-mentioned etching treatment is 0.06 to 0.3% in the visible region (400 to 700 nm). Further, 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.

Before forming the anti-reflection film, clean the surface of the glass substrate.
It is preferable to preheat to about ° C.

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

In this example, a single ultrafine particle thin film 5 is formed on a 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 function component 6. The conductive component 7 is, as it were, ultrafine particles and may be present outside the ultrafine particles 1. In this example, the ultrafine particles is not covered with SiO ₂ film by a surface layer portion binder removal by etching, that is, summer ultrafine particles in exposed remain without coated with SiO ₂ film. An SiO ₂ filling portion (binder) 2 is formed in a gap between the ultrafine particles and the glass substrate 3. The SiO ₂ thin film 2 serving as a binder is a product obtained by firing and decomposing Si (OR) ₄ .

In this example, SnO ₂ is used as the conductive component 7, and SiO ₂ is used as the antireflection function component 6. SnO ₂ / S during film formation
The volume ratio of iO ₂ is 0.1 (10%) or more and 0.5 (50%) or less. In this case, the ratio of the conductive functional component during film formation in the ultrafine particles is 1% or more and 50% by weight%. Is the following,
In that case, the calculation is performed excluding the SiO ₂ thin film 4.

In addition, the distance between the ultrafine particles needs to be an interval at which the distance between the conductive components contained in the adjacent ultrafine particles is maintained at such a length that a so-called tunnel effect appears. Such a distance is preferably 0.05 μm or less.

The average particle size of the ultrafine particles (the thickness of one thin film) is 0.1
μm or less, the thickness of the thin film is 0.1 μm
0.2 μm is acceptable, in which case the valley depth of the thin film formed between the particles is usually 0.05
μm to 0.2 μm. FIG. 2 illustrates these relationships, wherein 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.

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

By using the apparatus schematically shown in FIG. 5, 80% by weight and 20% by weight of SnO ₂ and Sb (SnO ₂ ;
% And Sb; 10 wt%) as a compressed powder, argon gas + 30% oxygen gas as a gas atmosphere in the system, argon 3 / min as a shielding gas, and argon + as an atmosphere introducing gas.
Ultrafine oxide-mixed particles were produced under an arc condition of 150 A-30 V using 30% oxygen gas 20 / min. The generated ultrafine particles were oxide mixed ultrafine particles of SiO ₂ + SnO ₂ + Sb ₂ O ₃ , and the composition ratio was 40: 9: 1, which was almost the same as the raw material.
The specific surface area is 60 to 70 m ² / g, and the amount of production is 15 to ²⁰ g / hour, and the production amount is about 6 times as large as the value when SiO ₂ ultrafine particles are produced using Si as the ultrafine particle raw material. Microscopic observation revealed that Sn was uniformly dispersed and that the SnO ₂ + Sb ₂ O ₃ ultrafine particles were finely dispersed in and around the amorphous SiO ₂ ultrafine particles.

As described above, according to the present embodiment, at least two or more kinds of oxide ultrafine particles can be produced in a form almost uniformly mixed using the arc heat source.

Ar + is used as a heat source for generating oxide-mixed ultrafine particles.
Similar oxide mixed ultrafine particles can be obtained by using O ₂ induction plasma or arc plasma and adding the mixed powder to the plasma. The ultrafine mixed oxide particles were dispersed in a solvent and applied to a glass substrate to form a conductive antireflection film.

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.

A solution is prepared by dissolving tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] in ethanol, and further adding water (H ₂ O) for the field of water addition and nitric acid (HNO ₃ ) as a dissolving agent. To the alcohol solution, 1 g of ultrafine particles (grain size is substantially spherical) 1 sized in the same manner as in Example 1 is added. At this time, an appropriate amount of acetylacetone is added as a dispersion medium so that the particles are sufficiently dispersed.

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

The compounding solution shown in Table 2 was dropped on a glass face plate and further uniformly applied with a spinner.

Then, it is calcined at 150 ° C. for about 30 minutes in the air to decompose tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ]. The ultrafine particles added to the alcohol solution are firmly fixed by a continuous and uniform thin film of SiO ₂ formed by decomposition. 5wt% NaO
Etching treatment is performed by immersion in H aqueous solution for about 15 seconds, followed by washing and drying to form irregularities on the glass face plate. Observation of the cross-section of the antireflection film formed in this way with a scanning electron microscope revealed that the outermost surface had a depth of 1,000Å ± 200Å,
An antireflection film 13 having a uniform pitch of 500 mm was formed. The binder 2 is an SiO ₂ portion formed by decomposition of tetraethoxysilane, and contains an antistatic component as an additive.

Light was incident on the glass face plate on which the antireflection film was formed at an incident angle of 5 °, and the reflectance was measured. As a result, as shown in Table 2, at a wavelength of 500 nm, 0.5% or less, the curve I in FIG. As shown, the reflectance was 1% or less in the wavelength range of 450 to 650 nm. This value sufficiently satisfies the conditions as a VDT (Visual Display Terminal).

Next, the surface of the glass face plate on which the antireflection film was formed was erased [Lion office equipment, trade name: Lion 50-
50], rubbing 50 times evenly under a pressure of 1 kg, the reflectivity increased only by about 0.1 to 0.2% as shown in the intensity of Table 2 and the curve II of FIG. Above was no problem at all. For comparison, when a similar test was performed on a glass face plate having irregularities formed by conventional etching, the reflectance increased by 2% with one rubbing of the eraser.
After five rubs, the reflectance was exactly the same as the untreated glass face plate shown in curve III in FIG.

 Next, a seventh embodiment will be described.

0.2 g of the ultrafine particles of the oxide obtained in Example 6 was dispersed in 1 g of nitric acid, and 5 g of a silicate alcohol solution, 5 g of acetylacetone, and 0.1 g of dicarboxylic acid were added to this solution, followed by stirring and dispersion. This solution was dropped on a glass substrate, and 600 rpm
, And baked at 160 ° C. for 30 minutes, and then subjected to an etching treatment according to Example 6. The ゜ specular reflectance of the formed film is 0.06 in the visible region of 400 to 700 nm.
%, And the surface resistance was 0.5 to 1 × 10 ⁷ Ω / □.

The surface resistance when a film was formed in the same manner as in the above example using a mixture of materials separately formed of ultrafine SiO ₂ particles and ultrafine SnO ₂ + Sb ₂ O ₃ particles was several 10 GΩ / □.

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

Ar-O ₂ is used as a heat source for generating oxide mixed fine particles.
Similar oxide mixed ultrafine particles can also be obtained by using induction plasma or arc plasma described above and adding the mixed powder to the plasma.

The eleventh embodiment will be described below. FIG. 8 is a cross-sectional view when an ultrafine particle film is formed on a glass substrate according to the present example, and FIG. 9 is a cross-sectional view after etching the ultrafine particle film to form a fine uneven surface.

The binder composition used was 74.07 wt% ethanol, 7.66 wt% water, 8.43 wt% isopropyl alcohol, 7.51 wt% ethyl silicate, and 1.39 wt% methyl ethyl ketone.
% And nitric acid are 0.89 wt%, for a total of 99.95 wt%. 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 acetylacetone 50 wt%, ethanol 37.04 wt%, water 3.83 w
t%, isopropyl alcohol 4.22 wt%, 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 ] was dissolved in ethanol, and then water and nitric acid (HN
O ₃ ), isopropyl alcohol and acetylacetone are added as a drying speed adjusting agent for film formation to form a solvent. This is Si
O ₂ ultrafine particles (average particle size of 40 to 50 nm) were added and sufficiently dispersed by ultrasonic vibration. The amount of ultrafine particles is the above solvent 1
To 25 g.

After dispersing the ultrafine particles, citraconic acid was further added to decompose sufficiently. 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 of the solvent. Thereafter, ultrasonic vibration was further applied to sufficiently disperse the ultrafine particles and sufficiently mix each component.

Next, this blended liquid was dropped onto a pretreated and washed soda glass plate surface (1100 × 100 mm, thickness 1 mm), and further uniformly coated with a spinner.

Thereafter, the mixture was calcined in the air at about 160 ° C. for about 45 minutes to decompose ethyl silicate to form SiO ₂ . Generated by this pyrolysis
The aforementioned citraconic acid and the like remain in SiO ₂ . The ultrafine SiO ₂ particles are firmly fixed on the glass substrate by a continuous thin film of SiO ₂ generated by thermal decomposition.

When the cross section of the ultrafine particle film thus formed was observed with an electron microscope, as shown in FIG.
μm, and a film in which SiO ₂ ultrafine particles were densely deposited was observed.

A glass plate with an ultrafine particle film formed as described above, 5w
It is immersed in an aqueous solution of t% conversion soda (NaOH) for about 15 seconds.
Then, from the surface of the ultrafine particle film, first, ethyl silicate is thermally decomposed, and the SiO ₂ compound generated (in which the binder is changed) is dissolved. Then, in the case of ultrafine particles, fine irregularities are generated between the ultrafine particles as shown in FIG. 8, and an effective antireflection function is exhibited. Under this condition, the SiO ₂ ultrafine particles themselves are not etched.

After forming this ultrafine particle film, the wavelength of 400 to 7 was applied to the etched glass plate and the untreated glass plate at an incident angle of 5 °.
The result of measuring the reflectivity of the light having a wavelength of
This is shown in curve IV of the figure.

In the entire wavelength region, the antireflection film of this embodiment has a reflectance of about half or less of the untreated glass plate and other embodiments of the present invention. Furthermore, if it shows by the integral value between wavelength 400-700nm,
Reduces the reflectance to about 1/3. Also, wavelength 400-700n
The transmittance between m is about 92% for the untreated glass plate
%, And about 87% of the glass plate on which the antireflection film of the present invention is formed. Since it has low reflection and high transmittance, it is suitable as an antireflection film for VDT. In particular, the effect of maintaining a high transmittance and reducing the reflectance is great.

In the above description, ultrafine particles are mainly used by a physical process. However, the present invention is naturally suitable for using ultrafine particles having a substantially uniform particle size manufactured by a chemical process.

〔The invention's effect〕

According to the present invention, fine irregularities can be formed by a simple method of coating and dipping, so that an antireflection film can be manufactured at low cost. Further, there is an effect that a large-area antireflection film can be easily formed. It is to be noted that the present invention is of course a low-temperature process and the immersion and coating processes are simple, so that the present invention is applied to the front surface of the cathode-ray tube after assembling the cathode-ray tube. Applying the above process is not a problem.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a cathode ray tube to which the present invention is applied, FIG. 2 is an enlarged sectional view of an antireflection film according to an example of the present invention, FIG. 3 is a characteristic diagram showing an antistatic effect, and FIG. Is a particle size distribution diagram of ultrafine particles applied to an example of the present invention, FIG. 5 is an explanatory view of an apparatus configuration showing an example of a process for producing ultrafine particles, and FIG. 6 is a reflection of an example of the present invention and a comparative example. Rate characteristic diagram,
FIG. 7 is a schematic cross-sectional view of a thin film before etching according to an example of the present invention, and FIG. 8 is a schematic cross-sectional view of a thin film similarly after etching. 1 ... ultra fine particles, 2 ... binder, 3 ... glass substrate.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Hirohiro Kawamura 3300, Hayano, Mobara-shi, Chiba Inside the Mobara Plant, Hitachi, Ltd. In-plant (56) References JP-A-64-76001 (JP, A) JP-A-62-289801 (JP, A) JP-A-57-204002 (JP, A) (58) Fields investigated (Int. . ^6, DB name) G02B 1/10 H01J 29/88 H01J 9/20 H01J 5/08

Claims (7)

(57) [Claims] An anti-reflection film for preventing reflection of external light by an ultra-fine particle film comprising an ultra-fine particle group and a binder filling each ultra-fine particle constituting the ultra-fine particle group. An antireflection film, characterized in that a fine uneven surface is formed on the outer surface and the exposed area of the ultrafine particles occupies 70% or more of the outer surface area of the ultrafine film. 2. An alcohol solution of Si (OR) ₄ (R is an alkyl group) to which ultrafine particles having an antireflection function are added on the surface of a glass body, followed by baking, and firing on the surface of the glass body. And in an antireflection film formed by adhering an SiO ₂ based thin film covering the same,
An antireflection film characterized in that it occupies 70% or more of the total film area including the SiO ₂ based thin film. 3. Ultrafine particles composed of two or more types of inorganic oxides, wherein the ultrafine particles are composed of the two or more types of inorganic oxides mixed alternately, or
One of the two or more inorganic oxides has a granular structure in which one of the inorganic oxides contains another inorganic oxide, and the average particle diameter of the ultrafine particles is a thin film mainly composed of ultrafine particles of 0.1 μm or less. Wherein the exposed area of the ultrafine particles in the thin film occupies 70% or more. 4. A method for forming an antireflection film, comprising: forming a thin film mainly composed of ultrafine particles on a substrate; and performing etching treatment to form fine irregularities on the surface of the thin film. 5. A reflection method comprising: forming a thin film mainly composed of ultrafine particles and a binder having a higher etching rate than the ultrafine particles on a substrate, and forming fine irregularities on the surface of the thin film by etching. A method for forming the prevention film. 6. A method for forming an anti-reflection film, comprising: forming an anti-reflection film on a surface of an image display plate by the method for forming an anti-reflection film according to claim 4. 7. An image display plate comprising the anti-reflection film according to claim 1 formed on a surface thereof.