3/ “'3
`
`10/49 6147‘
`
`DT‘lS Rec’d PCT/PTO 2 5 MAR 2004
`
`ANTLFOULING FILM COATED AR
`
`LE
`
`DESCRIPTION
`
`TECHNICAL FIELD
`
`The present invention relates to an antifouling film coated article having the
`
`capability of providing good antifouling property over an extended time period
`
`regardless of the amount of rainfall falling thereon.
`
`BACKGROUND ART
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`In the past, a film containing a photocatalytic semiconductor material such
`
`as TiOZ, ZnO and SnO2 is proposed as antifouling film (for example, Japanese
`
`Patent Publications No. 2756474 and No. 2924902).
`The film containing the photocatalytic semiconductor material exhibits a
`
`self-cleaning effect of decomposing carbon-based contaminants (for example,
`carbon, components included in exhaust gas of diesel cars or tar of cigarette)
`adhered to its film surface, odor eliminating effect of decomposing bad-smell
`
`components such as amine compounds or aldehyde compounds, antibacterial
`effect of preventing the propagation of bacteria such_ as E.coli bacteria and
`Staphylococcus aureus, and mildew-proof effect.
`It is thought that when light
`(ultraviolet light) having an excitation wavelength (for example, 400 nm) is
`
`irradiated to the film containing the photocatalytic semiconductor material, active
`
`oxygen is generated to result in oxidation decomposition of organic materials.
`
`In addition, when the ultraviolet light is irradiated to the film containing the
`photocatalytic semiconductor material, moisture adhered to the film surface or
`
`the moisture in the air are changed to hydroxy radicals by the photocatalysis, so
`that the hydroxy radicals decompose water-repellent organic materials. As a
`result, since a contact angle of water on the film surface decreases, an effect of
`
`improving wettability (hydrophilicity) of water on the film surface can be obtained.
`
`By this improvement of hydrophilicity, when the coated article is used as an
`
`indoor member, a defogging effect of preventing fogging of glass or mirror is
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`expected. On the other hand, when the coated article is used as an outdoor
`
`member, the antifouling effect of allowing rain water to wash away contamination
`
`is expected.
`
`In addition,
`
`the photocatalytic semiconductor material has the
`
`antistatic function, which is useful to improve the antifouling property.
`
`It has been thought
`
`that since the film containing the photocatalytic
`
`semiconductor material has a hydrophilic surface with 5° or less of the contact
`
`angle of water thereon, the antifouling effect is obtained by, for example, rain
`
`water falling thereon. However, when the water amount falling on the film
`
`surface decreases, theantifouling effects is not obtained sufficiently.
`
`In addition,
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`there is a case that contamination appears along flows of rain water on the film
`
`surface, so that noticeable contamination remains on the film surface.
`
`In these
`
`viewpoints, the conventional antifouling film coated articles still have plenty of
`
`room for improvement.
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`15
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`SUMMARY OF THE INVENTION
`
`Therefore, in view of the above problems, a concern of the present invention
`
`is to provide an antifouling film coated article having the capability of maintaining
`
`good antifouling property regardless of the amount of rainfall falling thereon.
`
`That is, the antifouling film coated article of the present invention has a film
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`20
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`of a silicone resin material on a. substrate, which is characterized in that a contact
`
`angle of water on the filmis in a range of 5 to 30°, preferably 8 to 25°, and an
`
`average surface roughness of the film is 5 nm or less. Thereby, excellent
`
`antifouling property is achieved regardless of the amount of water adhered to the
`
`film surface.
`
`In particular, when the coated article is used outside, good
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`25
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`antifouling property is obtained.
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`‘
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`In the antifouling film coated article according to a preferred embodiment
`
`of the present invention, the silicone resin material.of the film is a composition
`
`containing colloidal silica and a silicone resin that is at least one of a partial
`
`In
`hydrolysate and full hydrolysate of 4 functional hydrolyzable organosilane.
`this case, since hydrophilicity of the film is maintained by the colloidal silica, it is
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`

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`easy to stably keep the contact angle of water in the above range over an extended
`
`time period.
`
`In particular, it is preferred that the above composition contains
`
`the colloidal silica such that a weight ratio of a solid content of silica to the solid
`
`content 1 in terms of condensate of the silicone resin is in a range of 0.01 to 9.
`
`In the antifouling film coated article of the present invention, it is also
`
`preferred that the above composition further contains an organic zirconium.
`
`this case, the contact angle of water on the film can be easily controlled.
`
`In
`
`In
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`particular, it is preferred that the composition contains 0.1 to 10 parts by weight
`
`of the organic zirconium in terms of ZrOz with respect to 100 parts by weight of
`
`the entire solid contents of the composition.
`
`In this case, an effeCt of
`
`maintaining the contact angle of water is further improved.
`
`In addition, gelation
`
`or agglomeration of the composition can be prevented during the film formation.
`
`As a result, the film formation becomes easy. -
`
`In the antifouling film coated article of the present invention, it is further
`
`preferred that the composition contains an optical semiconductor material.
`In
`this case,
`since water-repellent organic materials are decomposed by the
`
`photocatalysis of the optical semiconductor material,
`
`it
`
`is possible to stably
`
`maintain the contact angle of water on the film surface over the extended time
`
`period. Moreover, in the case of using the antifouling film coated article at the
`
`outdoors, an antifouling effect can be obtained by the photocatalysis when rain
`
`water adheres to the surface of the coated article.
`
`In particular, when the composition described above contains the optical
`
`semiconductor material, it is preferred that a compounding ratio by weight of the
`
`optical semiconductor material to the total weight 1 of the solid content in the
`
`terms of condensate of the silicone resin and silica as the solid content of the
`
`colloidal silica is 0.01 or more and less than 0.4.
`
`In this case, it is possible to
`
`obtain sufficient photocatalysis effect, and stably maintain the contact angle of
`
`water on the film surface. Furthermore, good transparency and strength of the
`
`film can be realized.
`
`In the antifouling film coated article of the present invention, it is also
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`preferred that the composition contains the optical semiconductor material such
`
`that a compounding ratio by weight of the optical semiconductor material to the
`
`solid content 1 in terms of condensate of the silicone resin is 0.01 or more and
`
`less than 0.4, and further contains 0.1 to 10 parts by weight of the organic
`
`zirconium in terms of ZrO2 with respect to 100 parts by weight of the entire solid
`
`contents of the composition.
`
`In this case,
`
`it is possible to obtain excellent
`
`photocatalysis as well as increased film strength.
`
`It becomes easy to maintain the
`
`contact angle of water. Moreover, gelation or agglomeration of the composition
`
`can be prevented during the film formation, so that the film formation becomes
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`easy.
`
`In the antifouling film coated article of the present invention, it is preferred
`
`that the substrate is made of glass.
`
`In this case, the coated article having good
`
`antifouling property can be provided.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.
`
`1 is a photograph showing an appearance of an antifouling film coated
`
`article of Example 1 according to the present invention, which was observed after
`being exposed to outdoor environment for 12 months;
`
`FIG. 2 is a photograph showing an appearance of an antifouling film coated
`
`article of Comparative Example 3, which was observed after being exposed to
`
`outdoor environment for 12 months; and
`
`FIG. 3 is a photograph showing an appearance of an antifouling film coated
`
`article of Comparative Example 1, which was observed after being exposed to
`
`outdoor environment for 12 months.
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`BEST MODE FOR CARRYING OUT THE INVENTION
`
`An antifouling film coated article of the present invention has a film of a
`
`silicone resin material on a substrate, wherein a contact angle of water on the film
`
`is in a range of 5 to 30°, preferably 8 to 25°, and an average surface roughness of
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`
`the film is 5 nm or less.
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`

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`In a case that the contact angle is less than 5°, even when a small amount of
`
`water adheres to the film, drops of water spread to the film surface. When the
`
`water drops do not run off therefrom, relatively large scale-like contamination
`
`remains on the film surface, as shown in FIG. 2. On the other hand, when the
`
`water drops run off, the contamination remains along flows of water on the film
`
`surface, as shown in FIG. 3.
`
`Since contaminants localize at outer edges of the
`
`water drops, a difference in the amounts of contaminants between the interior
`
`and the outer edge of the respective water drop is recognized as a contrast of
`
`contamination.
`
`In the case that the contact angle of water exceeds 30°, even
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`
`when a large amount of water adheres to the film, a layer of water is not formed
`on the film surface.
`In this case, the contaminants adhered to the film surface
`
`are hard to run off, so that they are pooled on the film surface to cause the
`
`contamination.
`
`In the present invention, when the contact angle of water is in
`
`the range of 8 to 25°,
`
`it is possible to obtain further improved antifouling
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`15
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`property.
`
`At a substantially initial condition that the coated article is used for an
`
`intended purpose, the film has the contact angle of 5 to 30°.
`
`In particular, when
`
`an optical semiconductor material described later is compounded, the “initial
`
`condition” means a condition that it is initially used under light irradiation.
`
`In
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`
`the present invention, it is. also preferred that the contact angle of water on the
`
`film surface is kept in the range of 5 to 30° for a long time period (preferably 6
`months or more) from first use.
`
`On the other hand, when the average surface roughness of the film exceeds
`
`5 nm, contaminants are easy to adhere to the film surface. That is, even when a
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`25
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`layer of water is formed on the film surface, the contaminants are caught by the
`
`bumpy surface of the film, so that they are hard to run off. As a result, the
`
`contaminants included in the water easily remain on the film surface. A lower
`
`limit of the average surface roughness is not specifically limited. When the
`
`contact angle of water is kept
`
`in the above range, smaller average surface
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`roughness is favorable.
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`

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`It is preferred that the silicone resin material constructing the antifouling
`
`film of the antifouling film coated article of the present invention is a composition
`
`containing colloidal silica and a silicone resin that is at least one of a partial
`
`hydrolysate and full hydrolysate of 4-functional hydrolyzable organosilane. A
`
`state of the silicone resin in this composition is not specifically limited. For
`
`example, it may be in a solution state or a dispersed (colloidal) state.
`
`By using the 4-functional hydrolyzable organosilane with four
`
`reactive
`
`substituents
`
`(hydrolyzable substituents) on silicon atom,
`
`it
`
`is possible to
`
`moderately give hydrophilicity to the film, stably keep the contact angle of water
`
`on the film surface, and also provide sufficient hardness to the film. As the 4-
`
`functional
`
`hydrolyzable
`
`organosilane,
`
`for
`
`example,
`
`a
`
`4-functional
`
`organoalkoxysilane shown by the following chemical formula (1) is available.
`Si (OR1 )4
`(1)
`
`In the above formula, the functional group “R1” of the alkoxyl group “OR”
`
`is a monovalent hydrocarbon group, preferably a monovalent hydrocarbon group
`
`having the carbon number of 1 to 8, for example, an alkyl group such as methyl
`
`group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl
`
`group and octyl group.
`
`In these hydrocarbon groups, when the carbon number
`
`is 3 or more, it is possible to use a group having straight chain such as n-propyl
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`20 ,7
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`group and n-butyl group, or a group having branched chain such as isopropyl _.
`
`group, isobutyl group and t-butyl group.
`
`In addition, different kinds of the '
`
`alkoxyl group “0R1” may be bonded to the silicon atom in one molecule.
`
`Moreover, an organoalkoxysilane obtained by partial hydrolysis of the 4—'
`
`functional organoalkoxysilane described above may be compounded.
`
`If necessary,
`
`as
`
`shown by the following chemical
`
`formula (2),
`
`an
`
`organoalkoxysilane not having four functional groups may be used in addition to
`
`the 4-functional hydrolyzable organosilane described above.
`R24'" Si (0R1 )"
`(2)
`(“n” is an integer of 1 to 3.)
`
`In the above formula, the functional group “R1” of the alkoxyl group “OR”
`
`is
`
`the same as the 4—functional organoalkoxysilane described above.
`
`The
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`

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`functional group “R2” may be the same as
`
`the functional group’
`
`“R1”.
`
`Alternatively, it may have a structure shown by the following chemical formula (3)
`
`r‘-’(5). Different kinds of the functional group “R” may be bonded to the silicon
`
`atom in one molecule.
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`5
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`CH2-CH-CH2—CH2-O-(CH2)3-
`\o/
`
`(3)
`
`CH2%CHCH2—O-(CH2)3—
`
`(4)
`
`CH3
`
`CH2=Cl3-fi-O-(CH2)3-
`
`(5)
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`‘
`
`0
`
`Specifically,
`
`as
`
`the hydrolyzable organosilane,
`
`it
`
`is possible to use
`
`y-
`
`glycidoxypropyl trimethoxysilane shown by the following chemical formula (6), y—
`
`glycidoxypropyl methyldimethoxysilane shown the following chemical formula (7),
`
`y-metacryloxypropyl trimethoxysilane shown by the following chemical formula
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`15
`
`(8), and y-metacryloxypropyl- methyldimethoxysilane shown by the following
`
`chemical formula (9).
`
`i
`
`‘
`
`CH2-CH-CH2-CH2-O-(CH2)3-Si(OCH3)3
`\/
`0
`
`(6)
`
`CH3
`
`(i-lr/CH-CHz-CHz-O-(CHz)3-Si(OCH3)2
`
`(7)
`
`20
`
`O
`
`

`

`CH3
`
`CH2=C-fi-O-(CH2)3-Si(OCH3)3
`
`(8)
`
`0
`
`CH3
`
`CH3
`
`CH2=C-C-O-(CH2)3-Si(OCH3)2
`
`(9)
`
`H 0
`
`By mixing the above—described hydrolyzable organosilane with water, and
`
`hydrolyzing a resultant mixture, the silicone resin of the partial hydrolysate or the
`
`full hydrolysate is obtained. The amount of water to be added to hydrolyze the
`hydrolyzable organosilane can be determined such that a mole equivalent
`
`(HzO/ORZ) of water
`
`(H20)
`
`to the hydrolyzable group (in the case of
`
`organoalkoxysilane, it is alkoxyl group (ORZ)) of the hydrolyzable organosilane is
`
`Within a range of 0.3 to 5.0, preferably 0.35 to 4.0, and more preferably 0.4 to 3.5.
`
`When this value is less than 0.3, there is a fear that the progression of hydrolysis
`
`becomes insufficient, so that a reduction in toughness of the cured film occurs.
`
`On thecother hand, when this value is more than 5.0, there is a tendency that
`
`gelation of the obtained silicone resin proceeds in a short time.
`
`In this case, the
`
`storage stability may deteriorate.
`If necessary, a catalyst may-be used at the hydrolysis. As the catalyst, it is
`
`preferred to use an acidic catalyst to reduce the production time. For example,
`
`the acidic catalyst comprises an organic acid such as acetic acid, monochloroacetic
`
`acid, citric acid, benzoic acid, dimethylmalonic acid, formic acid, propionic acid,
`
`glutaric acid, glycolic acid, maleic acid, malonic acid, toluenesulfonic acid and
`
`oxalic acid, an inorganic acid such as silane halide, nitric acid and hydrochloric
`
`acid, and an acidic sol filler such as acidic titania sol and acidic colloidal silica.
`
`At least one of these acidic catalysts can be used.
`
`If necessary, this hydrolysis
`
`may be performed at a heating temperature of 40 to 100 °C.
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`In addition, the hydrolysis of organoalkoxysilane may be performed in the
`
`presence of a diluent solvent in addition to water. As the diluent solvent, for
`
`example, it is possible to use a lower aliphatic alcohol such as methanol, ethanol,
`
`isopropanol, n-butanol, and isobutanol, ethylene glycol derivative such as ethylene
`
`glycol, ethylene glycol monobutyl ether, acetic ethyl glycol monoethyl ether,
`
`diethylene glycol derivative such as diethylene glycol and diethylene glycol
`
`monobutyl ether, and a hydrophilic organic solvent such as diacetone alcohol.
`
`At least one of these diluent solvents can be used.
`
`In addition, as the diluent solvent, at least one of toluene, xylene, hexane,
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`10,
`
`heptane, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone,
`
`methyl ethyl ketone oxime may be used together with the hydrophilic organic
`
`solvent described above.
`
`It is preferred that a weight-average molecular weight of the silicone resin
`
`composed of the partial hydrolysate or the full hydrolysate of organoalkoxysilane
`
`15
`
`is within a range of 500 to 1000 in terms of polystyrene. When the weight-
`
`average molecular weight is less than this range, the hydrolysate may be unstable.
`
`On the other hand, when the weight-average molecular weight exceeds the above
`
`range, there is a fear that sufficient film hardness can not be maintained.
`
`On the other hand, as the colloidal silica, for example, it is possible to use a
`
`‘
`
`.20
`
`water-dispersible colloidal silica or a colloidal silica dispersible in hydrOphilic -
`
`organic solvent such as alcohol. Generally, such a colloidal silica contains 20‘to
`
`50 wt% of silica as the solid content. From this value, the compounding amount
`
`of silica can be determined. The water-dispersible colloidal silica is usually
`
`obtained from water glass. A marketed production thereof is available. On the
`
`other hand, the colloidal silica dispersible in hydrophilic organic solvent can be
`
`readily prepared by substituting water of the water dispersible colloidal silica with
`an organic solvent. A marketed production thereof is also available.
`
`In the organic-solvent dispersible colloidal silica, as the organic solvent in
`
`which the colloidal silica is dispersed, for example, it is possible to use a lower
`
`aliphatic alcohol
`
`such as methanol, ethanol,
`
`isopropanol, n-butanol, and
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`10
`
`isobutanol, ethylene glycol derivative such as ethylene glycol, ethylene glycol
`
`monobutyl ether, acetic ethylene glycol monoethyl ether, diethylene glycol
`
`derivative such as diethylene glycol and diethylene glycol monobutyl ether, or a
`
`hydrophilic organic solvent such as diacetone alcohol. One of these organic
`
`solvents or a mixture of thereof may be used.
`
`In addition to the hydrophilic
`
`organic solvent, at least one selected from toluene, xylene, hexane, heptane, ethyl
`
`acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl
`ketone oxime can be used.
`
`It is preferred that a compounding amount of the colloidal silica in the
`
`composition for film formation is determined such that a weight ratio of a solid
`
`content of silica to the solid content (1) in terms of condensate of the silicone
`
`resin is in a range of 0.01 to 9. When the compounding amount is less than this
`
`range, the effect of maintaining moderate hydrophilicity of the film may lower.
`
`On the other hand, when the compounding amount exceeds the above range,
`
`there is a tendency of reducing the film strength.
`
`In the case of using the composition containing the silicone resin and the
`
`colloidal
`
`silica described above,
`
`the hydrophilicity of the film surface is
`
`maintained by the colloidal silica having good hydrophilicity, so that the contact
`angle of water on the film can be favorably kept over the extended time period.
`
`In addition, the film hardness can be increased, and improvements in surface
`
`smoothness and crack resistance can be obtained.
`
`When-using the water dispersible colloidal silica, it is possible to use water
`
`existing as disperse medium in the water dispersible colloidal silica for the
`
`hydrolysis of the hydrolyzable organosilane. That is, when the hydrolyzable
`
`organosilane and the water dispersible colloidal silica are compounded at the
`
`preparation of the composition for film formation, water of the disperse medium
`
`is used to hydrolyze the hydrolyzable organosilane and generate the silicone resin.
`
`As a result, the composition containing the silicone resin can be obtained.
`
`In
`
`addition, the colloidal silica works as acidic catalyst at the hydrolysis.
`
`In the case of using the organic-solvent dispersible colloidal silica, when it is
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`11
`
`added at the hydrolysis of the hydrolyzable organosilane, the colloidal silica works
`
`as the acidic catalyst.
`
`If necessary, another inorganic filler may be used.
`
`For example,
`
`it is
`
`possible to use a powder-like silica such as aero gel or an inorganic filler such as
`
`inorganic oxides of the optical semiconductor. These are favorable from the
`
`viewpoints of chemical stability such as resistance to solvent and acid resistance,
`
`and dispersibility in the silicone resin. One of these fillers may be used by itself.
`
`Alternatively, two or more of them may be used.
`
`It is preferred that the composition for forming the film of the antifouling
`
`10
`
`film coated article of the present
`
`invention further contains an optical
`
`semiconductor material.
`
`That
`
`is, when the film containing the optical
`
`semiconductor material
`
`receives light having an excitation wavelength (for
`
`example, ultraviolet having the wavelength of 400 nm), active oxygen such as
`
`superoxide ions or hydroxy radicals is generated from the moisture in the air or
`
`'15
`
`the moisture adhered to the film surface.
`
`Since this active oxygen results in
`
`oxidation decomposition of organic materials,
`
`it is possible to obtain a self-
`
`cleaning effect of decomposing carbon-based contaminants (for example, carbon
`
`components includedin exhaust gas of diesel cars or tar of cigarette) adhered to
`
`the film surface, odor eliminating effect of decomposing bad-smell components
`
`such as amine compounds or aldehyde compounds, antibacterial effect of
`
`preventing thefloccurrence of bacteria such as E.coli bacteria and Staphylococcus
`
`aureus, and mildew proof effect.
`
`In addition, since water-repellent organic
`
`materials adhered to the film surface or included in the film are decomposed by
`
`the photocatalysis, the contact angle of water on the film surface can be stably
`
`maintained over the extended time period.
`
`In particular, when the coated article
`
`of the present invention is used as an outdoor member, the above-described
`
`photocatalysis is, brought by rain water falling on the coated article, so that the
`
`antifouling effect is obtained. Moreover, amounts of OH groups on the film
`
`surface are increased by the photocatalysis of the optical semiconductor, thereby
`
`maintaining the hydrophilicity of the film surface. By allowing the film surface
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`

`

`12
`
`to have hydrophilicity, a surface resistance value of the film becomes small.
`
`Therefore, the film possesses the antistatic property.
`
`As the optical semiconductor material, it is possible to use a single metal
`
`oxide such as titanium oxide, zinc oxide, tin oxide, iron oxide, zirconium oxide,
`
`tungsten oxide,
`
`chromium oxide, molybdenum oxide,
`
`ruthenium oxide,
`
`germanium oxide, lead oxide, cadmium oxide, copper oxide, vanadium oxide,
`
`niobium oxide, tantalum oxide, manganese oxide, cobalt oxide, rhodium oxide,
`
`nickel oxide and rhenium oxide, and strontium titanate.
`
`In these compounds, it
`
`is preferred to use the single metal oxide from the viewpoint of the practical use.
`
`In those single metal oxides, it is particularly preferred to use titanium oxide
`because there are advantages in photocatalyst performance,
`safety,
`ready
`
`availability and cost performance. By the way, titanium oxide having the crystal
`
`form of anatase type exhibits excellent photocatalyst performance and an effect of
`
`accelerating the curing of the film.
`
`In addition, the contact angle of water on the
`
`film can be maintained for
`
`a
`
`longer
`
`time period, and the photocatalyst
`
`performance such as decomposition appears in a short time. One of these
`
`optical semiconductor materials may be used by itself. Alternatively,
`
`two or
`
`more of them may be used. Additionally, it is preferred to dope a metal element
`
`such as silver, copper, iron and nickel of accelerating charge separation of the
`
`optical semiconductor into the optical semiconductor material. A raw material
`
`that can finally be converted into a compound having the optical semiconductor
`
`property, or a derivative of the compound such as titanium alkoxide may be
`
`added.
`
`When adding the optical semiconductor material to the composition for film
`
`formation, the optical semiconductor material can be in a state dispersible in the
`
`composition, for example, power, fine powder, or $01 particles dispersed in
`
`solution. When selecting a sol state such as the sol particles dispersed in solution,
`and particularly the sol state having a pH value of 7 or less, it is possible to further
`
`accelerate the curing of the film, and therefore improve the convenience in use.
`
`When using the optical semiconductor material in the sol state, the dispersion
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`13
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`medium is not specifically limited, but it has the capability of uniformly dispersing
`
`fine particles of the optical semiconductor material therein. For example, water
`
`or an organic solvent may be used by itself. Alternatively, a mixed dispersion
`
`medium of water and the organic solvent may be used.
`
`As the mixed dispersion medium of water and the organic solvent, it is
`
`possible to use a mixed dispersion medium of water and one or more of
`
`hydrophilic organic solvents, for example, a lower aliphatic alcohol such as
`
`methanol, ethanol,
`
`isopropanol, n-butanol, and isobutanol, ethylene glycol
`
`derivative such as ethylene glycol, ethylene glycol monobutyl ether, acetic ethylene
`
`glycol monobutyl ether, diethylene glycol derivative such as diethylene glycol and
`
`diethylene glycol monobutyl ether, and diacetone alcohol.
`
`In the case of using
`
`the mixed dispersion medium of water and methanol, there are advantages in
`
`dispersion stability of optical
`
`semiconductor
`
`fine particles
`
`and drying
`
`characteristics of the dispersion medium at the film formation.
`
`When a sol-like optical semiconductor material having acid stability is used
`
`in the presence of only water or the mixed dispersion medium of water and the
`
`organic solvent, the sol-like optical semiconductor material works as the acid
`
`catalyst for hydrolyzing the hydrolyzable organosilane, and water existing as the
`
`dispersion medium is used for the hydrolysis of the hydrolyzable organosilane.
`
`That
`
`is, when the hydrolyzable organosilane
`
`and the
`
`sol—like optical
`
`semiconductor material are compoundedat the preparation of the compound for
`
`film formation, water of the dispersion medium is used to hydrolyze the
`
`hydrolyzable organosilane, and this hydrolysis is accelerated by the sol-like optical
`
`semiconductor material as the acid catalyst. As a result, the partial hydrolysate
`
`or the full hydrolysate of the hydrolyzable organosilane is generated.
`
`In the case of adding the sol-like optical semiconductor material using only
`
`the organic solvent, the kind of the organic solvent as the dispersion medium is
`
`not specifically limited. For example, it is possible to use at least one hydrophilic
`
`organic solvent used in the mixed dispersion medium of water and the organic
`
`solvent, or at least one hydrophobic organic solvent such as toluene and xylene.
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`In these organic solvents, it is preferred to use methanol.
`
`In this case, there are
`
`advantages in dispersion stability of optical semiconductor fine particles, and
`
`drying characteristics of the dispersion medium at the film formation.
`
`It is preferred that a compounding weight ratio of the optical semiconductor
`
`material to the total weight (1) of the solid content in the terms of condensate of
`
`the silicone resin and silica that is the solid content in the colloidal silica is 0.01 or
`
`more and less than 0.4. When the ratio is less than this range, sufficient
`
`photocatalyst performance may not be obtained. On the other hand, when the
`
`ratio exceeds this range, there is a tendency of decreasing the film strength.
`
`In
`
`the above range, excellent film strength is obtained.
`
`It is also preferred that the composition for film formation further contains
`
`an organic zirconium. When the organic zirconium is included in the film, the
`
`contact angle of water on the film can be easily controlled within the range of 5 to
`
`30°, and more preferably 8 to 25°.
`
`In addition, a condensation reaction of the
`
`silicone resin can be accelerated at the film formation. As a result, there are
`
`advantages that a crosslinking density in the film increases, and the adhesion
`
`between the film and the substrate is improved. Moreover, effects of providing
`
`hydrophobicity, water-proof and alkali-proof to the film can be achieved.
`
`As the organic zirconium, for example, a compound shown in the following
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`chemical formula (10) can be used.
`
`-_
`
`Zr on R3rn (0R1 )p
`
`(10)
`
`))
`((
`(K D
`m , p are an integer of 0 to 4, and “n” is O or 1.
`
`In the case of “n”=0,
`
`“m+p”=4.
`
`In the case of “n”= 1, “m+p”=2.)
`
`In the above formula, the functional group “R” of the alkoxyl group “OR”
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`
`“R3”»in the formula comprises, for example,
`is the same as the formula (1), (2).
`C5H7O2 (acetylacetonate complex) or CGI-I9O3 (ethyl acetoacetate complex).
`In
`
`addition, different kinds of “OR1 ”and “K” may be included in one molecule.
`
`particular,
`
`as
`
`the
`
`organic
`
`zirconium, when
`
`using
`
`at
`
`least
`
`one
`
`In
`
`of
`
`Zr(OC4H9)3(C5H7OZ) and Zr(OC4H9)2(C5H7OZ)(C6H903),
`
`it
`
`is possible to
`
`further improve the film strength. For example, even when the film is formed at
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`15
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`a relatively low temperature of 100 °C, it is possible to obtain a film strength
`
`corresponding to the film formed at the high temperature of 300 °C.
`
`It is
`
`preferred that an additive amount of the organic zirconium is 0.1 to 10 weight %
`
`in terms of ZrOz with respect to the entire solid contents of the composition for
`
`film formation.
`
`In the case of using the composition for film formation, which contains both
`
`of the optical semiconductor material and the organic zirconium, it is preferred
`
`that a compounding weight ratio of a solid content of the optical semiconductor
`
`material to a total weight (1) of the solid content in terms of condensate of the
`
`silicone resin and silica as the solid content in the colloidal silica is 0.01 or more
`
`and less than 0.4, although it changes in response to the composition of silicone
`
`resin. When the ratio is
`
`less
`
`than this
`
`range,
`
`sufficient photocatalyst
`
`performance may not be obtained. On the other hand, when the ratio exceeds
`
`this range, the contact angle of water on the film surface may become less than 5°.
`
`Moreover, there is a fear that transparency of the film is lost, or a reduction in
`film strength occurs.
`
`In the case of using the composition containing the optical semiconductor
`
`material and the organic zirconium, it is also preferred that an additive amount of
`
`the organic zirconium is in a range of 0.1 to 10 weight % in terms of ZrOz with
`
`respect to the entire solid contents of the composition for film formation».
`
`In this
`
`case, it is possible to further improve the effect of maintaining the-contact angle.
`When the additive amount is less than the above range, the above effect may not
`
`be sufficiently obtained. On the other hand, when the additive amount is
`exceeds the above range, the film formation may be difficult because of the
`
`occurrence of gelation or agglomeration of the composition.
`
`To obtain the composition for film formation, in which the above described
`
`components are uniformly dispersed,
`
`it
`
`is possible to use a conventional
`
`dispersing technique, for example, homogenizer, disper, paint shaker or bead mill.
`
`The antifouling property brought by the film formation is
`
`remarkably
`
`achieved in the case of forming the film on a translucent substrate.
`
`In particular,
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`when using a glass substrate, a temperature range available for the film formation
`
`becomes wider, so that the film strength can be easily improved.
`
`In addition to
`
`the glass substrate, for example, a substrate made of polycarbonate, acrylic resin
`
`or polyethylene terephthalate resin may be used.
`
`Prior to the film formation on the substrate, it is preferred to perform a
`
`pretreatment (preliminary washing) for increasing the adhesion between the film
`
`and the substrate or making uniform painting of the film possible.
`
`This
`
`pretreatment comprises alkali cleaning, ammonium fluoride cleaning, plasma
`
`cleaning, UV cleaning and cerium oxide cleaning.
`
`A method of forming the film is not specifically limited. For example, it is
`
`possible to choiceappropriate one from conventional methods such as brush
`
`painting, spray coating