JP6094308B2 - Silica porous membrane - Google Patents

Description

  The present invention relates to a porous silica film having high wear resistance and excellent low refractive index property, antifouling property and the like.

  Patent Documents 1 to 4 are known as known techniques related to a silica film having wear resistance, low refractive index property, and antifouling property.

  In Patent Document 1, an antifouling layer-forming paint containing fluorine is top-coated on an optical film such as silica to form an antifouling layer. In this method, the lower layer and the antifouling layer are formed. It is considered that the adhesion of the antifouling layer is low and the wear resistance is low because the formation of chemical bonds between them is insufficient. As far as the examples of Patent Document 1 are seen, scratches have been confirmed in the case of applying to a silica film coated by the sol-gel method, although it is slight in a test of steel wool 100 g and 10 reciprocations. Therefore, it is considered that there is no practical wear as an optical material. Further, since the surface layer is coated with the fluorine-containing material as a separate process after the antireflection processing, a plurality of coating processes are required, and the productivity is poor in terms of yield and cost.

  In order to solve this problem, in Patent Documents 2 to 4, a condensate of a silane having a perfluoro group and an alkylsilane and / or tetraalkoxysilane, silica particles, metal (mainly aluminum) alkoxide and / or metal A method of forming a silica film having not only antifouling properties but also abrasion resistance and low refractive index by using a coating material containing a (mainly aluminum) chelate compound is disclosed. In this method, since the fluorine compound is contained in the low refractive index layer material, a silica film having low refractive index properties, abrasion resistance and antifouling properties can be provided by a single coating.

  However, in the silica films described in Patent Documents 2 to 4, since a fluorine compound (fluoroalkyl group-containing compound) having a small intermolecular cohesive energy exists in the silica film, the silane condensate in the silica film and As a result of reducing the cohesive energy between the silica particles, the strength of the silica film is impaired and the wear resistance is reduced.

  As described above, the conventional technique has not provided a practical low-refractive index and antifouling silica film having wear resistance.

JP 2004-258348 A JP 2006-265530 A JP 2007-9127 A JP 2007-182511 A

  An object of the present invention is to provide a porous silica film having high abrasion resistance and excellent low refractive index property, antifouling property and the like.

  As a result of intensive studies to solve the above problems, the present inventors have found that a porous silica film satisfying the following conditions (1) and (2) has high wear resistance and antifouling properties, and has a low refractive index. The present invention was completed.

That is, the gist of the present invention is to satisfy the following (1) and (2), consists in the silica porous membrane, wherein the refractive index of 1.20 to 1.45.
(1) Carbon atom, oxygen atom, fluorine atom and silicon atom calculated by elemental analysis by X-ray photoelectron spectroscopy (XPS) in the region from the surface of the porous silica membrane to the position of 10 nm in the depth direction The ratio of the number of fluorine atoms to the total number of is 3 to 35 atomic%.
(2) Carbon atoms calculated by elemental analysis by XPS analysis in the depth direction in a region from the position of 10 nm in the depth direction from the surface of the porous silica membrane to a position in the depth direction of 40 nm from the surface The ratio of the number of fluorine atoms to the total number of oxygen atoms, fluorine atoms and silicon atoms is 0.8 atomic% or less.

  Furthermore, the silica porous membrane of the present invention is a carbon atom, oxygen atom, calculated by elemental analysis by XPS in the depth direction in the region from the surface of the silica porous membrane to the position in the depth direction of 10 nm. The ratio of the number of oxygen atoms to the total number of fluorine atoms and silicon atoms is preferably 30 to 70 atomic%.

  Furthermore, the porous silica film of the present invention preferably has a surface roughness (Ra) of 0.2 to 6 nm.

  ADVANTAGE OF THE INVENTION According to this invention, the porous silica membrane which has high abrasion resistance, and was excellent in low refractive index property, antifouling property, etc. is provided.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[Silica porous membrane]
The porous silica membrane of the present invention satisfies the following (1) and (2), preferably further satisfies the following (3), has a refractive index of 1.20 to 1.45, and a surface roughness ( Ra) is 1 to 6 nm.
(1) Carbon atom, oxygen atom, fluorine atom and silicon atom calculated by elemental analysis by X-ray photoelectron spectroscopy (XPS) in the region from the surface of the porous silica membrane to the position of 10 nm in the depth direction The ratio of the number of fluorine atoms to the total number of is 3 to 35 atomic%.
(2) Carbon atoms calculated by elemental analysis by XPS analysis in the depth direction in a region from the position of 10 nm in the depth direction from the surface of the porous silica membrane to a position in the depth direction of 40 nm from the surface The ratio of the number of fluorine atoms to the total number of oxygen atoms, fluorine atoms and silicon atoms is 0.8 atomic% or less.
(3) The number of oxygen atoms relative to the total number of carbon atoms, oxygen atoms, fluorine atoms and silicon atoms, calculated by elemental analysis by XPS in the region from the surface of the porous silica membrane to the position of 10 nm in the depth direction Is 30 to 70 atomic%.

In the following, in the present invention, in the region from the surface of the porous silica film to the position in the depth direction of 10 nm, elemental analysis (hereinafter referred to as “surface elemental analysis”) is performed by X-ray photoelectron spectroscopy (XPS). The ratio of the number of fluorine atoms to the total number of carbon atoms, oxygen atoms, fluorine atoms, and silicon atoms, calculated as “the amount of fluorine on the outermost layer”, is calculated from the surface of the porous silica membrane. In the region from the position of 10 nm in the depth direction to the position of 40 nm in the depth direction from the surface, elemental analysis is carried out by XPS analysis in the depth direction (hereinafter, this analysis may be referred to as “depth elemental analysis”). ), The ratio of the number of fluorine atoms to the total number of carbon atoms, oxygen atoms, fluorine atoms and silicon atoms may be referred to as “second surface layer fluorine amount”. That.
The number of oxygen atoms relative to the total number of carbon atoms, oxygen atoms, fluorine atoms, and silicon atoms calculated by surface elemental analysis by XPS in the region from the surface of the porous silica membrane to a position in the depth direction of 10 nm. Is sometimes referred to as the “outermost surface oxygen amount”.

<XPS elemental analysis>
In the present invention, the elemental analysis in the surface and depth direction by X-ray photoelectron spectroscopy (XPS) of the porous silica film is measured under the following conditions using an XPS apparatus (model name Quantum 2000) manufactured by ULVAC-PHI. The value analyzed.

(Surface element analysis)
As the X-ray source, a monochromatic Al-Kα ray was used, and the output was 16 kV-34 W. X-rays were scanned in a 300 μm × 300 μm region on the sample surface, and the generated photoelectrons were dispersed. The XPS measurement scheduled by irradiating an electron beam and Ar ions were simultaneously neutralize the charge of the sample.

(Depth direction analysis)
In the depth direction analysis, Ar ions accelerated to 2 kV were used, and Ar ion sputtering and XPS measurement were alternately performed to track the composition change in the depth direction. For the conversion of the depth (nm), a sputtering rate obtained by actually measuring a thermally oxidized Si wafer (oxide film thickness: 100 nm) was used.

(Analysis of measurement results)
About the photoelectron peak of each element obtained by XPS measurement, the area intensity | strength after performing a background removal process based on the Shirley method was calculated | required, and atomic concentration was computed using the relative sensitivity correction coefficient provided from the apparatus manufacturer.

<Outermost layer fluorine content>
The outermost layer fluorine content of the porous silica membrane of the present invention is 3 atomic% or more, preferably 8 atomic% or more, and more preferably 11 atomic% or more. Moreover, it is 35 atomic% or less, 30 atomic% or less is preferable and it is more preferable that it is 25 atomic% or less.

  If the amount of fluorine on the outermost layer of the porous silica membrane is too small, the surface free energy of the membrane will not be reduced, and a sufficient reduction in the surface friction coefficient will not be obtained. As a result, sufficient wear resistance may not be obtained. There is sex. Moreover, aggregation of fluorine atoms occurs, and there is a possibility that performance unevenness in the surface direction occurs. Since the unevenness of performance has a part where the film strength is locally weak, the film causes cohesive failure of the film starting from such a part against wear. As a result, the wear resistance is remarkably reduced, but when the outermost layer fluorine content is to form a film that exceeds the above upper limit, the surface free energy of the solute in the composition described later used for forming the porous silica film is the surface of the solvent. Compared to free energy, it is greatly reduced. As a result, the film-forming property of the composition is greatly reduced, and the uniformity of the porous silica film obtained after film formation may be impaired. In addition, the fluorine compound (fluorine-containing silane) in the composition cannot be dissolved and separated, which may impair the uniformity of the composition. As described above, the reduction in film uniformity causes local defects in the film, which adversely affects the wear resistance. Further, more fluorine atoms than necessary may be collected in the outermost layer of the porous silica membrane, which may form a low strength layer, thereby impairing the strength of the membrane.

<Second surface layer fluorine content>
The second surface layer fluorine content of the porous silica membrane of the present invention is 0.8 atomic% or less, preferably 0.5 atomic% or less, and more preferably 0.2 atomic% or less.
It was found that the physical properties of the outermost layer alone are not sufficient to improve the abrasion resistance of the film, and the physical properties of the second surface layer, which is the underlying layer, play an important role in expressing the performance of the outermost layer. . Fluorine atoms present in the depth direction of the porous silica film, that is, inside the porous silica film, cause a deterioration in the wear resistance of the porous silica film. This is because the fluorine atoms have a small surface energy but also a small intermolecular cohesive energy, so the fluorine atoms inside the membrane reduce the cohesive force between the silane condensates in the silica porous membrane, resulting in a porous silica membrane. This is to reduce the strength of the.

In the abrasion resistance and scratch resistance of the porous silica membrane, not only the physical properties of the outermost surface of the porous silica membrane but also the physical properties of a certain depth (interface layer bonded to the surface) are greatly affected. In the present invention, by defining the outermost surface layer fluorine amount and the second surface layer fluorine amount of the porous silica membrane as described above, the film strength in the region of 40 nm in the depth direction from the surface is controlled while controlling the surface energy of the outermost surface. By controlling the above, it becomes possible to remarkably improve the abrasion resistance of the film.
The lower limit of the amount of fluorine on the second surface layer of the porous silica membrane of the present invention is preferably below the XPS elemental analysis detection limit.

<Outermost layer oxygen content>
The silica porous membrane of the present invention preferably has an outermost layer oxygen content of 30 atomic% or more. Among them, the outermost layer oxygen amount is preferably 35 atomic% or more, and particularly preferably 40 atomic% or more. Moreover, the outermost layer oxygen content of the porous silica membrane of the present invention is preferably 70 atomic% or less, more preferably 65 atomic% or less, and particularly preferably 63 atomic% or less.

  In particular, in the porous silica membrane of the present invention, the oxygen atoms present in the surface layer function to link the fluorine-containing silane and the silica skeleton localized on the surface via, for example, a siloxane bond (Si—O—Si). Have The fact that the amount of oxygen on the outermost layer is small means that the bond between the fluorine-containing silane and the silica skeleton is weak, and the fluorine-containing silyl groups localized on the surface are easily cleaved by abrasion or hydrolysis, and the film strength is significantly reduced. . As a result, wear resistance may be reduced. When the amount of oxygen on the outermost layer is too large, there are many unreacted functional groups, and impurities such as water and alcohol may be present in a large amount on the surface and in the vicinity thereof. Not only the wear resistance but also the antifouling property may be lowered. Furthermore, hydrolysis and solvolysis proceed due to impurities such as water and alcohol, and the siloxane bond is cut, thereby reducing the film strength. As a result, wear resistance may be reduced.

<Porous structure>
The silica porous membrane of the present invention has a porous structure having pores in order to keep the refractive index low. The structure is not particularly limited, and the hole is usually a connecting hole in which tunnels or independent holes are connected, but the detailed structure of the hole is not particularly limited. However, the pore structure is preferably a porous structure in which small pores are discontinuously present from the viewpoint of wear resistance.

  The pore diameter of the porous silica membrane of the present invention is not particularly limited, but the average pore diameter is preferably 0.2 to 100 nm, more preferably 0.4 to 80 nm, and further preferably 0.8 to 60 nm. If the pore diameter of the porous silica membrane is too small, the refractive index will not be low, and sufficient optical properties may not be obtained. On the other hand, if it is too large, there is a risk that the surface is defective, the surface property is deteriorated, and haze such as scattering occurs. In addition, the strength of the film may be significantly reduced, and the wear resistance may be impaired.

  Although there is no restriction | limiting in particular in the porosity of the silica porous membrane of this invention, 5-90% is preferable, 10-85% is more preferable, and 20-80% is more preferable. If the porosity of the silica porous membrane is too small, the refractive index will not be low, and sufficient optical properties may not be obtained. On the other hand, if it is too large, there is a risk that the surface is defective, the surface property is deteriorated, and haze such as scattering occurs. In addition, the strength of the film may be significantly reduced, and the wear resistance may be impaired.

The average pore diameter and average porosity of the porous silica membrane of the present invention can be calculated from the measurement results of gas (N ₂ , Ar, etc.) adsorption isotherms. The average porosity can also be estimated from the value of the refractive index of the porous silica film.

<Thickness>
Although there is no restriction | limiting in particular in the thickness of the silica porous membrane of this invention which is a film | membrane form, in order to use as an optical function layer, 0.02-5 micrometers is preferable, 0.03-4 micrometers is more preferable, 0.03. 04-3 μm is more preferable, and 0.05-2 μm is most preferable. If the thickness of the porous silica film is less than 0.05 μm, it may be necessary to improve the flatness of the base material for forming the porous silica film of the present invention described later. From the viewpoint, the film forming process may be difficult. On the other hand, when the thickness of the porous silica membrane exceeds 10 μm, the progress of the sol-gel reaction at the silica-based precursor membrane-substrate interface is inhomogeneous in the heating process described later in the production of the porous silica membrane of the present invention. Thus, there is a possibility that strain is likely to remain in the obtained silica porous membrane.

  The film thickness of the porous silica film can be calculated from the reflectance measurement result.

<Refractive index>
The refractive index of the porous silica film of the present invention is usually 1.45 or less, preferably 1.42 or less, more preferably 1.40 or less, particularly preferably 1.38 or less, and particularly preferably 1.36 or less. If the refractive index is too large, the strain in the porous silica film of the present invention is increased and may be weak against external force. On the other hand, the lower limit of the refractive index is usually 1.20 or more, preferably 1.22 or more. If the refractive index is too small, the mechanical strength of the porous silica film of the present invention may be significantly reduced.

  In the present invention, the refractive index of the porous silica film refers to a value at a wavelength of 400 nm to 700 nm measured by an optical technique such as a spectroscopic ellipsometer method, a reflectance measurement, a reflection spectral spectrum measurement, or a prism coupler, preferably a spectral This is measured with an ellipsometer. When measuring with a spectroscopic ellipsometer, the refractive index can be estimated by fitting the measured value with a Cauchy model or a Tauc-Lorentz model. Moreover, when measuring by reflectance measurement, a refractive index can be estimated by using a Fresnel formula from a measurement result.

<Surface roughness (Ra)>
The silica porous membrane of the present invention preferably has a surface roughness (Ra) of 6 nm or less, more preferably 5 nm or less, still more preferably 4 nm or less, still more preferably 3 nm or less, particularly preferably 2 nm or less, particularly preferably. Is 1 nm or less. If the surface roughness (Ra) is too large, the stress is received at the convex portion during wear, and the stress concentrates on the convex portion and local cohesive failure occurs, which may reduce the wear resistance. There is. Moreover, the homogeneity of the porous silica membrane may be reduced. On the other hand, the lower limit of the surface roughness (Ra) is not limited, but is usually 0.2 nm or more, preferably 0.3 nm or more. If the surface roughness (Ra) is too small, there is a possibility that the distortion of the porous silica membrane will become extremely large. Further, the stress remaining in the film is extremely weak against external force, and there is a risk of adversely affecting the wear resistance.

  The surface roughness (Ra) of the porous silica membrane of the present invention is based on a standard specified in JIS B0601: 2001, using a P-15 type contact surface roughness meter manufactured by KLA Tencor. Thus, an average value can be calculated from a value measured several times under the condition of one scanning distance of 0.5 μm.

[Method for producing silica porous membrane]
There is no restriction | limiting in particular in the manufacturing method of the silica porous membrane of this invention.
Although an example of the manufacturing method of the silica porous membrane of this invention is demonstrated below, the manufacturing method of the silica porous membrane of this invention is not limited to the following method.

  The porous silica membrane of the present invention is produced using, for example, a composition containing a fluorine-containing silane, a fluorine-free alkoxysilane, water, and an organic solvent.

In order to produce the porous silica membrane of the present invention, first, a composition as a raw material is prepared, and after this is formed into a membrane, it is heated to obtain the porous silica membrane of the present invention.
Usually, a fluorine-containing silane, a fluorine-free alkoxysilane, water, an organic solvent, and if necessary, a composition containing an organic polymer as a template material is applied on a substrate (film formation process) to form a silica-based precursor film. The laminated body which has a silica porous membrane is formed through the extraction process of an organic polymer as needed.
In the production of the porous silica membrane of the present invention, other operations may be performed as necessary. That is, as long as the effects of the present invention are not significantly impaired, an arbitrary process may be performed before, during and after each process described below. For example, aging may be performed during or after the preparation of the composition used for the production of the porous silica membrane of the present invention, and the cured porous silica membrane of the present invention may be cooled and post-treated.

{Composition used for production of porous silica membrane of the present invention}
First, about the composition used for manufacture of the silica porous membrane of this invention, the compounding component and the preparation method are demonstrated.

<Fluorine-containing silane>
There is no restriction | limiting in the kind of fluorine-containing silane. Examples of suitable ones include trifluorosilane, fluorotrimethoxysilane, fluorotriethoxysilane, trifluoromethyltrimethoxysilane, trifluoromethyltriethylsilane, trifluoromethyltrimethylsilane, trifluoromethyltrimethoxysilane, (3 , 3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trifluoropropyl) triethoxysilane, (3,3,3-trifluoropropyl) dimethylchlorosilane, 3- (3,3,3 -Trifluoropropyl) heptaethyltrisiloxane, (3,3,3-trifluoropropyl) methylcyclotrisiloxane, (3,3,3-trifluoropropyl) methylcyclotetrasiloxane, (3-heptafluoroisopropyl) propyl Torik Rosilane, pentafluoroethyltrimethoxysilane, nonafluorohexyltriethoxysilane, nonafluorohexyltrimethoxysilane, nonafluorohexyltrichlorosilane, nonafluorohexyldimethylchlorosilane, nonafluorohexylmethyldichlorosilane, nonafluorohexyltris (dimethylamino) Silane, nonafluorohexyldimethyl (dimethylamino) silane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) trimethoxysilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) trichlorosilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) methyldichlorosilane, (Trideca Fluoro-1H, 1H, 2H, 2H-octyl) dimethylchlorosilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) silane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) dimethylchlorosilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) silane, (Heptadecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, (Heptadecafluoro-1H, 1H, 2H, 2H-octyl) ) Trimethoxysilane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) trichlorosilane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) methyldichlorosilane, (heptadecafluoro-1H, 1H) 2H, 2H-octyl) dimethylchlorosilane, (heptadecafluoro -1H, 1H, 2H, 2H-octyl) silane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) dimethylchlorosilane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) silane, (par Fluorodecyl) ethyltrichlorosilane, bis ((tridecafluoro-1,1,2,2-tetrahydrooctyl) -dimethylsiloxy) methylchlorosilane, bis ((tridecafluoro-1,1,2,2-tetrahydrooctyl) -Dimethylsiloxy) methylsilane, bis ((tridecafluoro-1,1,2,2-tetrahydrooctyl) -dimethylsiloxy) tetramethyldisiloxane, 5,5,6,6,7,7,8,8,9 , 9,10,10,10-Tridecafluoro-2- (tridecafluorohexyl) decyltriclo Silane, heptadecatrifluorodecyltrimethoxysilane, pentafluorophenyltrimethoxysilane, pentafluorophenyltriethoxysilane, hexadecafluorododec-11-en-1-yltrimethoxysilane, hexadecafluorododec-11-ene-1- Yltrichlorosilane, 1,8-bis (trichlorosilylethyl) hexadecafluorooctane, m- (trifluoromethyl) phenyltrimethoxysilane, p-trifluoromethyltetrafluorophenyltriethoxysilane, pentafluorophenyldimethylchlorosilane, penta Fluorophenylpropyldimethylchlorosilane, pentafluorophenylpropylmethyldichlorosilane, pentafluorophenylpropyltrichlorosilane, pentafluoro E cycloalkenyl silane, such as perfluorooctyl phenyl trichlorosilane and the like.
These may be used alone or in combination of two or more.

  Among the above fluorine-containing silanes, a silane having a linear fluoroalkyl group having 6 to 10 carbon atoms is preferable for sufficient antifouling properties and wear resistance. Among these, nonafluorohexyltriethoxysilane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, and (heptadecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane are preferable. If the carbon chain of the fluorine-containing silane is too short, the friction reducing effect due to the fluoroalkyl group may be too low, and if the carbon chain is too long, the film-forming property of the composition described later is greatly reduced, and the film after film formation There is a possibility that the uniformity of the above is impaired.

  The ratio of fluorine-containing silane to silicon atoms derived from all alkoxysilanes in the composition used for producing the porous silica membrane of the present invention is preferably 0.10 to 0.004 (mol / mol), and 0.05 to 0 0.005 (mol / mol) is more preferable, and 0.02 to 0.006 (mol / mol) is more preferable. If the proportion of the fluorine-containing silane is too small, the friction reducing effect due to the fluoroalkyl group may be too low. If it is too large, the film-forming property of the composition described later will be greatly reduced, and the uniformity of the film after film formation will be reduced. It can be damaged.

<Alkoxysilane containing no fluorine>
Examples of alkoxysilanes not containing fluorine (hereinafter sometimes simply referred to as “alkoxysilanes”) include tetraalkoxysilanes, monoalkyltrialkoxysilanes, dialkyldialkoxysilanes, trialkylalkoxysilanes, hydrolysates thereof, and the like. Examples include partial condensates (oligomers and the like).

  Two or more alkoxysilanes are preferably used in combination, and preferably contain a hydrolyzate and partial condensate of these alkoxysilanes. By using two or more alkoxysilanes in combination, there is an advantage that the strength and refractive index of the silica skeleton formed can be controlled by controlling the blending ratio.

(Tetraalkoxysilane)
There is no restriction | limiting in the kind of tetraalkoxysilane. Examples of suitable ones include tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane, tetraisopropoxysilane, tetra (n-butoxy) silane, tetra (t-butoxy) silane, tetra (n-pentoxy). ) Silane, tetra (isopentoxy) silane, and the like.

  From the viewpoint of the stability of the silica-based precursor film in the rough drying step described later, tetramethoxysilane and tetraethoxysilane and partial condensates thereof are preferable, and tetraethoxysilane is more preferable. However, since tetraalkoxysilane tends to undergo hydrolysis and partial condensation over time, even when only tetraalkoxysilane is prepared, the hydrolyzate and partial condensate of tetraalkoxysilane usually coexists with tetraalkoxysilane. There are many cases.

(Monoalkyltrialkoxysilane)
There is no restriction | limiting in the kind of monoalkyl trialkoxysilane. Examples of suitable ones include trimethoxysilane, triethoxysilane, tri-n-propoxysilane, triisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltriisopropoxysilane Ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltriisopropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri-n-propoxysilane, isopropyltri Methoxysilane, isopropyltriethoxysilane, isopropyltri-n-propoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyl Such as isopropoxycarbonyl silane. In addition, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, in which an alkyl group substituted on a silicon atom has a reactive functional group, 3 -Triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-carboxypropyltrimethoxysilane, 3-trihydroxysilyl -1- Propane - such as sulfonic acid can also be used.

(Dialkyl dialkoxysilane)
There is no restriction | limiting in the kind of dialkyl dialkoxysilane. Examples of suitable ones are methyldimethoxysilane, methyldiethoxysilane, methyldi-n-propoxysilane, methyldiisopropoxysilane, ethyldimethoxysilane, ethyldiethoxysilane, ethyldi-n-propoxysilane, ethyldiisopropoxy. Silane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldiisopropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldi-n-propoxysilane, diethyldiisopropoxysilane, di-n- Propyldimethoxysilane, di-n-propylethoxysilane, di-n-propyldi-n-propoxysilane, di-n-propyldiisopropoxysilane, diisopropyldimethoxysilane, dii Propylethoxysilane, diisopropyldi-n-propoxysilane, diisopropyldiisopropoxysilane, di-n-butyldimethoxysilane, di-n-butylethoxysilane, di-n-butyldi-n-propoxysilane, di-n-butyl Diisopropoxysilane, di-sec-butyldimethoxysilane, di-sec-butylethoxysilane, di-sec-butyldi-sec-propoxysilane, di-sec-butyldiisopropoxysilane, di-tert-butyldimethoxysilane, Di-tert-butylethoxysilane, di-tert-butyldi-n-propoxysilane, di-tert-butyldiisopropoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi-n-propoxysilane, diphe Such distearate isopropoxycarbonyl silane. Further, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane or the like in which an alkyl group substituted on a silicon atom has a reactive functional group can also be used.

(Trialkylalkoxysilane)
There is no limitation on the type of trialkylalkoxysilane. Examples of suitable ones include trimethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, tri-n-propylmethoxysilane, tri-n-propylethoxysilane and the like.

(Other alkoxysilanes)
As alkoxysilanes not containing fluorine, in addition to the above, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (tri 2 organic residues such as ethoxysilyl) ethane, 1,4-bis (trimethoxysilyl) benzene, 1,4-bis (triethoxysilyl) benzene, 1,3,5-tris (trimethoxysilyl) benzene What combined the above trialkoxysilyl groups etc. can also be used.

  Among the above alkoxysilanes, tetraalkoxysilane, monoalkyltrialkoxysilane, and dialkyldialkoxysilane are preferable, and tetraalkoxysilane is more preferable in order to strengthen the skeleton of the porous structure. Furthermore, from the viewpoint of environmental resistance of the porous membrane, monoalkyltrialkoxysilanes and dialkyldialkoxysilanes having an aromatic hydrocarbon group or an aliphatic hydrocarbon group are preferred. Specifically, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethylsilane and the like are preferable.

(Preferred combination of alkoxysilane)
When two or more kinds of alkoxysilanes not containing fluorine are used in combination, from the viewpoint of controlling the sol-gel reaction, the combination is preferably tetraalkoxysilane, monoalkyltrialkoxysilane, or monoalkyltrialkoxysilane, A combination of tetraalkoxysilane and monoalkyltrialkoxysilane is more preferable. Tetraalkoxysilane strengthens the silica skeleton, and monoalkyltrialkoxysilane can lower the refractive index. That is, the silica skeleton strength and the refractive index can be controlled by controlling the blending ratio of the two. From the viewpoint of wettability to the substrate, tetraalkoxysilane and dialkyl dialkoxysilane, monoalkyltrialkoxysilane and dialkyl dialkoxysilane are preferable.

(Ratio of alkoxysilane)
When using together the 2 or more types of fluorine-free alkoxysilane, the compounding ratio will not have a restriction | limiting in particular unless the effect of this invention is impaired remarkably. When two types of fluorine-free alkoxysilanes are used in combination, for example, from the viewpoint of water resistance of the formed silica body, 0.5: 9.5 to 5: 5 is preferable in terms of silicon atoms of alkoxysilane, 2: 8 to 5: 5 is more preferable, and 2.5: 7.5 to 5: 5 is most preferable.

  Further, from the viewpoint of strengthening the skeleton of the porous structure, it is effective to contain tetraalkoxysilane, and the ratio of silicon atoms derived from tetraalkoxysilane to silicon atoms of all alkoxysilanes is usually 0.15 (mol / mol) or more, preferably 0.3 (mol / mol) or more, more preferably 0.35 (mol / mol) or more, and usually 0.95 (mol / mol) or less, preferably 0.90 (mol / mol). mol / mol) or less, more preferably 0.8 (mol / mol) or less.

  Here, the silicon atoms of all alkoxysilanes refer to the total number of silicon atoms possessed by all alkoxysilanes contained in the composition. Therefore, even if the composition contains a compound having a silicon atom in addition to alkoxysilane, the silicon atom that the compound has does not participate in the calculation of the ratio. In addition, the ratio of the silicon atom of the alkoxysilane can be measured by Si-NMR.

  In the composition used for the production of the porous silica membrane of the present invention, a compound containing silicon (silicon atom-containing compound), including the fluorine-containing silane and the alkoxysilane not containing fluorine, is usually 0.01. % By weight or more, preferably 0.1% by weight or more, more preferably 0.5% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30% by weight. The content is preferably 20% by weight or less, more preferably 15% by weight or less. When the content of the silicon atom-containing compound in the composition is less than 0.01% by weight, the surface property of the porous film may be deteriorated in the heating step, and the appearance may be poor. On the other hand, if it exceeds 50% by weight, it tends to be affected by the flatness of the substrate, and the sol-gel reaction in the film forming process may become non-uniform in the surface direction.

  In addition, from the viewpoint of controlling the film thickness of the resulting porous silica membrane, the silicon atom-containing compound in the composition used for producing the porous silica membrane of the present invention, an organic polymer as a template material described below, and the like are included. The solid content concentration is usually 0.02% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more. Further, it is usually preferably 50% by weight or less, more preferably 40% by weight or less, and further preferably 35% by weight or less.

<Water>
The composition used for producing the porous silica membrane of the present invention contains water. Although water is essential in the sol-gel reaction, in the present invention, it plays an important role in controlling the surface tension of the composition and forming a high-quality silica-based precursor film in the film-forming process. Although there is no restriction | limiting in particular in the purity of the water to be used, Usually, the water which performed any one or both processing among ion exchange and distillation should just be used. However, when the obtained porous silica membrane is used in an application field that particularly dislikes micro-impurities such as laminates for optical applications, a higher purity silica porous membrane is desirable. It is preferable to use ultrapure water. Further, among impurities, contamination of 100 nm or more may affect the progress of the sol-gel reaction. Therefore, for example, it is preferable to use water that has passed through a filter having a pore size of 0.01 μm to 0.5 μm.

  The amount of water used is such that the ratio of water to silicon atoms of all alkoxysilanes in the composition is usually 1 (mol / mol) or more, preferably 3 (mol / mol) or more, more preferably 5 (mol / mol). That's it. Further, it is usually 30 (mol / mol) or less, preferably 20 (mol / mol) or less. If the ratio of water to silicon atoms in the total alkoxysilane is smaller than the above range, it is difficult to control the sol-gel reaction, the pot life is short, a film is formed in a non-homogeneous state, the surface is rough, and the Abrasion may be inferior. On the other hand, if it is larger than the above range, the sol-gel reaction becomes difficult to proceed, and the reaction takes time, so that the water resistance may be lowered. The amount of water can be calculated by the Karl Fischer method (coulometric titration method).

<Organic solvent>
The composition used for producing the porous silica membrane of the present invention contains an organic solvent. Alcohols are most suitable as the organic solvent. Alcohols have an affinity for the alkoxysilane, its hydrolyzate, and further a partial condensate, and therefore are preferable for making the sol-gel reaction during the silica porous film formation proceed homogeneously. Furthermore, it is effective for forming a high-quality silica-based precursor film by maintaining a stable state at the gas-liquid (composition) interface and the solid (base material) -liquid (composition) interface generated in the film forming process. is there.

  There is no restriction on the type of alcohol. Examples of suitable ones include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl -1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol, 1-hexanol Monohydric alcohols such as 2-hexanol, 3-hexanol, ethylene glycol monomethyl ether, 2-ethoxyethanol, propylene glycol monomethyl ether, dihydric alcohols such as ethylene glycol and diethylene glycol, trihydric alcohols such as glycerin, cyclohexanol, etc. Alicyclic Alcohol, and other aromatic alcohols such as benzyl alcohol. In addition, these 1 type may be used independently and 2 or more types may be used together by arbitrary combinations and a ratio.

  Among these, monohydric alcohols and dihydric alcohols are preferable from the viewpoint of the hydrolysis reaction of the alkoxysilane contained, and monohydric alcohols are more preferable. Further, from the viewpoint of the surface properties of the obtained porous silica membrane, methanol, ethanol, 1-propanol, t-butanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 1-pentanol, ethyl acetate , Methyl acetate, isobutyl acetate and the like are preferable. Therefore, it is preferable to use at least one selected from these.

  Further, from the viewpoint of facilitating the structure formation of the silica-based precursor film in the film-forming step and improving the wettability with the base material, the boiling point of the organic solvent used is preferably 110 ° C. or less, more preferably 100 ° C. or less, and 90 ° C. The following is more preferable. As such a thing, methanol, ethanol, 1-propanol, t-butanol, 2-propanol etc. are preferable, for example. On the other hand, from the viewpoint of suppressing deformation of the porous structure in the heating step, the boiling point of the organic solvent is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. For example, 2-methyl-1-propanol, 1-butanol, and 1-pentanol are preferable.

  Furthermore, alcohols having different boiling points may be used as a mixture. In this case, in order to suppress azeotropy in each step, the difference in boiling points of the combined alcohols is preferably 5 ° C. or more, preferably 10 ° C. The above is more preferable, and 20 ° C. or higher is more preferable. Further, the ratio of alcohols on the high boiling point side to the total alcohols is usually 5% by weight or more, preferably 10% by weight or more, more preferably 40% by weight or more, further preferably 60% by weight or more, particularly preferably. 80% by weight or more. In addition, the upper limit of the said ratio is 98 weight% normally. If this upper limit is exceeded, the surface properties of the resulting silica porous membrane may be lowered, and if it is less than the lower limit, there is a risk that sufficient effects cannot be obtained.

  The composition used for the production of the porous silica membrane of the present invention may contain an organic solvent other than the alcohols. For example, an organic solvent other than alcohols can be used in order to further improve the wettability with the substrate described later and the film forming property in the film forming process.

  Examples of suitable organic solvents include ethers or esters such as methyl acetate, ethyl acetate, isobutyl acetate, ethylene glycol dimethyl ether, propylene glycol methyl ether acetate; ketones such as acetone and methyl ethyl ketone; formamide, N-methylformamide N-ethylformamide, N, N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylpyrrolidone, N -Formylmorpholine, N-acetylmorpholine, N-formylpiperidine, N-acetylpiperidine, N-formylpyrrolidine, N-acetylpyrrolidine, N, N'-diformylpiperazine, N, '- diformyl piperazine, N, N'- amides such as diacetyl piperazine; lactones γ- butyrolactone; tetramethylurea, N, ureas such as N'- dimethyl imidazolidine; and dimethyl sulfoxide.

  The amount of the organic solvent used is arbitrary as long as the effects of the present invention are not significantly impaired, but the content in the composition used for producing the porous silica membrane of the present invention is usually 0.05% by weight or more, especially 0. 1% by weight or more is preferable, 1% by weight or more is more preferable, and 10% by weight or more is more preferable. Further, it is usually 50% by weight or less, particularly 40% by weight or less, and more preferably 30% by weight or less. If the amount of the organic solvent used is too small or too large, there is a possibility that a sufficient effect cannot be obtained.

<Catalyst>
The composition used for the production of the porous silica membrane of the present invention may contain a catalyst, and as the catalyst, for example, a substance that promotes the hydrolysis and dehydration condensation reaction of the alkoxysilane described above may be arbitrarily used. it can.

  Examples include hydrofluoric acid, phosphoric acid, boric acid, hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, maleic acid, methylmalonic acid, stearic acid, linolenic acid, benzoic acid, phthalic acid, citric acid, succinic acid. Acids such as lactic acid, malic acid, mandelic acid, pyruvic acid, malonic acid, adipic acid, glutaric acid, salicylic acid, aconitic acid; amines such as ammonia, butylamine, dibutylamine, triethylamine; tetramethylammonium hydroxide, water Basic ammonium salts such as tetraethylammonium oxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; bases such as pyridine; Lewis acids such as acetylacetone complex of aluminum; and other acidic and basic amino acids .

  Moreover, a metal chelate compound is also mentioned as an example of a catalyst. Examples of the metal species of the metal chelate compound include titanium, aluminum, zirconium, tin, and antimony. Specific examples of the metal chelate compound include the following.

  Examples of the aluminum complex include di-ethoxy mono (acetylacetonato) aluminum, di-n-propoxy mono (acetylacetonato) aluminum, di-isopropoxy mono (acetylacetonato) aluminum, di-n- Butoxy mono (acetylacetonato) aluminum, di-sec-butoxy mono (acetylacetonato) aluminum, di-tert-butoxy mono (acetylacetonato) aluminum, monoethoxy bis (acetylacetonato) aluminum, mono -N-propoxy bis (acetylacetonato) aluminum, monoisopropoxy bis (acetylacetonato) aluminum, mono-n-butoxy bis (acetylacetonato) aluminum, mono-sec-but Si-bis (acetylacetonato) aluminum, mono-tert-butoxy bis (acetylacetonato) aluminum, tris (acetylacetonato) aluminum, diethoxy mono (ethylacetoacetate) aluminum, di-n-propoxy mono ( Ethyl acetoacetate) aluminum, diisopropoxy mono (ethyl acetoacetate) aluminum, di-n-butoxy mono (ethyl acetoacetate) aluminum, di-sec-butoxy mono (ethyl acetoacetate) aluminum, di-tert- Butoxy mono (ethyl acetoacetate) aluminum, monoethoxy bis (ethyl acetoacetate) aluminum, mono-n-propoxy bis (ethyl acetoacetate) aluminum, mono Sopropoxy bis (ethyl acetoacetate) aluminum, mono-n-butoxy bis (ethyl acetoacetate) aluminum, mono-sec-butoxy bis (ethyl acetoacetate) aluminum, mono-tert-butoxy bis (ethyl acetoacetate) Examples thereof include aluminum chelate compounds such as aluminum and tris (ethylacetoacetate) aluminum.

  Titanium complexes include triethoxy mono (acetylacetonato) titanium, tri-n-propoxy mono (acetylacetonato) titanium, triisopropoxy mono (acetylacetonato) titanium, tri-n-butoxy mono (acetyl). Acetonato) titanium, tri-sec-butoxy mono (acetylacetonato) titanium, tri-tert-butoxy mono (acetylacetonato) titanium, diethoxy bis (acetylacetonato) titanium, di-n-propoxy bis (Acetylacetonato) titanium, diisopropoxy bis (acetylacetonato) titanium, di-n-butoxy bis (acetylacetonato) titanium, di-sec-butoxy bis (acetylacetonato) titanium, di-tert -Butoxy bis (ace Ruacetonate) titanium, monoethoxy tris (acetylacetonato) titanium, mono-n-propoxy tris (acetylacetonato) titanium, monoisopropoxy tris (acetylacetonato) titanium, mono-n-butoxy tris (acetyl) Acetonato) titanium, mono-sec-butoxy-tris (acetylacetonato) titanium, mono-tert-butoxy-tris (acetylacetonato) titanium, tetrakis (acetylacetonato) titanium, triethoxy mono (ethylacetoacetate) titanium , Tri-n-propoxy mono (ethyl acetoacetate) titanium, triisopropoxy mono (ethyl acetoacetate) titanium, tri-n-butoxy mono (ethyl acetoacetate) titanium, tri-sec-butyl Xy mono (ethyl acetoacetate) titanium, tri-tert-butoxy mono (ethyl acetoacetate) titanium, diethoxy bis (ethyl acetoacetate) titanium, di-n-propoxy bis (ethyl acetoacetate) titanium, diiso Propoxy bis (ethyl acetoacetate) titanium, di-n-butoxy bis (ethyl acetoacetate) titanium, di-sec-butoxy bis (ethyl acetoacetate) titanium, di-tert-butoxy bis (ethyl acetoacetate) Titanium, monoethoxy tris (ethyl acetoacetate) titanium, mono-n-propoxy tris (ethyl acetoacetate) titanium, monoisopropoxy tris (ethyl acetoacetate) titanium, mono-n-butoxy tris (ethyl acetoacetate) Acetate) titanium, mono-sec-butoxy tris (ethyl acetoacetate) titanium, mono-tert-butoxy tris (ethyl acetoacetate) titanium, tetrakis (ethyl acetoacetate) titanium, mono (acetylacetonate) tris (ethyl aceto) Acetate) titanium, bis (acetylacetonato) bis (ethylacetoacetate) titanium, tris (acetylacetonato) mono (ethylacetoacetate) titanium and the like.

  Among those described above, acids or metal chelate compounds are preferable, and acids are more preferable in order to more easily control the hydrolysis and dehydration condensation reaction of the alkoxysilane compound. In addition, a catalyst may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The amount of the catalyst used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the amount is usually 0.001 mol times or more with respect to the alkoxysilane in the composition used for the production of the porous silica membrane of the present invention. It is preferably 003 mol times or more, particularly preferably 0.005 mol times or more, and usually 0.8 mol times or less, particularly 0.5 mol times or less, and particularly preferably 0.1 mol times or less. If the amount of catalyst used is too small, the hydrolysis reaction will not proceed moderately, and active groups such as silanol groups will remain in the porous silica membrane after production, which may reduce the water resistance of the porous silica membrane. In addition, if the amount is too large, it becomes difficult to control the reaction, and the surface concentration of the porous silica membrane may be deteriorated by further increasing the catalyst concentration during the production.

<PH>
The composition used for producing the porous silica membrane of the present invention preferably has a pH of 6 or less from the viewpoint of film forming properties. The pH of the composition is more preferably 5.5 or less, further preferably 5.0 or less, and particularly preferably 4.5 or less. By making it into this range, the surface modification of the base material described later can be simultaneously performed during the production of the porous silica membrane of the present invention, and the film forming property tends to be further improved.

<Others>
The composition used for the production of the porous silica membrane of the present invention may contain components other than the above-described fluorine-containing silane, fluorine-free alkoxysilane, water, organic solvent, and catalyst. Moreover, the said component may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(Organic polymer)
The composition used for producing the porous silica membrane of the present invention may contain an organic polymer as a template material, and a silica-based precursor membrane was formed by applying a composition containing an organic polymer to a substrate. Thereafter, a silica porous membrane having a higher porosity can be obtained by removing all or part of the organic polymer in the extraction step.

  From the viewpoint of forming a porous structure, the weight average molecular weight of the organic polymer to be used is usually 500 or more, preferably 1,000 or more, more preferably 2,000 or more, and particularly preferably 5,000 or more. If the weight average molecular weight is too small, it may be difficult to maintain high porosity of the resulting silica porous membrane, and it may not be possible to stably produce a low refractive index silica porous membrane. . On the other hand, although there is no restriction | limiting in the upper limit of the weight average molecular weight of an organic polymer, Usually, 100,000 or less, Preferably it is 70,000 or less, More preferably, it is 40,000 or less. If the weight average molecular weight is too large, the composition thickens and the film-forming property may be lowered.

  The type of the organic polymer is not particularly limited as long as the effects of the present invention are not significantly impaired. For example, (meth) acrylate polymer, polyanhydride polymer, polyether polymer, polycarbonate polymer, polyester polymer Examples thereof include organic polymers such as molecules.

  The (meth) acrylate polymer is composed of acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, and derivatives thereof. Specific examples include diethylene glycol acrylate, dipropylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, acrylamide, vinyl pyridine, N-methyl acrylamide, N, N-dimethyl acrylamide, diethylene glycol methacrylate, dipropylene glycol methacrylate, methoxy. Diethylene glycol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methacrylamide, N-methylmethacrylamide, N, N-dimethylmethacrylamide, methyl acrylate, ethyl acrylate, isopropyl acrylate, amyl acrylate, 2-methoxypropyl acrylate, 2-Ethoxypropyl acrylate , 2-ethylhexyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, amyl methacrylate, 2-methoxypropyl methacrylate, 2-ethoxyethyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate and the like. These may be used alone or in combination of two or more.

  The polyanhydride polymer is obtained from an aliphatic dicarboxylic acid having 2 or more carbon atoms. Specific examples include polymalonic anhydride, polysuccinic anhydride, polyoxalic anhydride, polyglutaric anhydride, and the like, methyl ester, ethyl ester, propyl ester, and the like. These may be used alone or in combination of two or more.

  The polyether polymer is composed of a polyalkylene glycol compound having 2 or more carbon atoms. Specific examples include polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyethylene glycol-polypropylene glycol block copolymer, polyethylene glycol-polytetramethylene glycol block copolymer, polyethylene glycol- Polypropylene glycol-polyethylene glycol block copolymer, etc., methyl ether, ethyl ether thereof; polyethylene glycol mono-p-methylphenyl ether, polyethylene glycol mono-p-ethylphenyl ether, polyethylene glycol mono-p-propylphenyl ether, them Methyl ether, ethyl ether; polyethylene glycol monopentanoic acid Ester, polyethylene glycol mono-hexanoic acid ester, polyethylene glycol mono-heptanoic acid esters, their methyl ether, ethyl ether, and the like. These may be used alone or in combination of two or more.

  The polycarbonate polymer is an aliphatic polycarbonate having 2 or more carbon atoms, and specific examples thereof include polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, polypentamethylene carbonate, their methyl ether, and ethyl ether. These may be used alone or in combination of two or more.

  The polyester polymer is composed of a compound comprising an aliphatic chain having 2 or more carbon atoms and an ester bond. Specific examples include polyethylene oxalate, polyethylene malonate, polyethylene succinate, polyethylene glutarate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polypropylene glutarate, their methyl ether, ethyl ether, propyl ether and the like. Can be mentioned. These may be used alone or in combination of two or more.

  From the viewpoint of the pot life of the composition used for the production of the porous silica membrane of the present invention and the stability of the silica-based precursor membrane in the film-forming process, the organic polymer includes (meth) acrylic polymers, polyether-based polymers. Molecules are preferred, and polyether polymers are more preferred. Among these, from the viewpoint of affinity with the hydrolyzable group-containing silane, the alkylene glycol compound of the repeating unit constituting the polyether polymer preferably has 2 to 4 carbon atoms, and more preferably 2 or 3 carbon atoms.

  Furthermore, in order to stably maintain the structure of the silica-based precursor film from the film forming process to the heating process, the organic polymer is preferably a copolymer in which alkylene glycol compounds having different carbon numbers are combined. At this time, the content of the alkylene glycol compound having a small number of carbons in the total of the alkylene glycol compound, that is, having a high affinity with the silanol group of the hydrolyzable group-containing silane is arbitrary as long as the effect of the present invention is not significantly impaired. However, it is usually 20% by weight or more, preferably 23% by weight or more, more preferably 25% by weight or more, and usually 100% by weight or less, preferably 90% by weight or less, more preferably 85% by weight or less. By staying within the above range, the organic polymer as a template material exists more stably than the hydrolyzate or condensate of hydrolyzable group-containing silane formed during the sol-gel reaction of hydrolyzable group-containing silane. can do.

  When the organic polymer is used, the content of the organic polymer in the composition used for producing the porous silica membrane of the present invention is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. Preferably, 1.2% by weight or more is more preferable, and 1.4% by weight or more is particularly preferable. If content of the organic polymer in a composition is more than this minimum, the sol-gel reaction of the hydrolyzable group containing silane in a film forming process can be stabilized. Although there is no restriction | limiting in the upper limit of content of the organic polymer in a composition, 50 weight% or less is preferable, 40 weight% or less is more preferable, and 30 weight% or less is especially preferable. If this upper limit is exceeded, the composition may thicken and the film-forming property may deteriorate.

(Surfactant)
The composition used for the production of the porous silica membrane of the present invention may contain a surfactant as long as the effects of the present invention are not significantly impaired. In some cases, the film forming property is remarkably improved. As the surfactant, any known surfactant can be used, and the type, combination, and ratio thereof are not particularly limited, and the following two or more surfactants may be used.

  Specific examples of surfactants include nonionic surfactants such as polyethylene glycol, polypropylene glycol and polyisobutylene glycol, anionic surfactants, cationic surfactants, amphoteric surfactants, and lipophilic groups that are fluorinated. Examples thereof include a fluorine-based surfactant having a carbon group, a silicone-based surfactant having a siloxane chain as a lipophilic group, and a surfactant having an alkyl group as a lipophilic group. Two or more of these surfactants are preferably selected from the viewpoint of film-forming properties of the composition, and among them, nonionic surfactants and fluorosurfactants (especially containing perfluoroalkyl groups). And a combination of a nonionic surfactant and a silicone surfactant (especially those containing a siloxane bond). The hydrophilic group of these surfactants is preferably, for example, a hydroxyl group, a carbonyl group, a carboxyl group or the like. Polyether, polyglycerin and the like are also preferable.

  Examples of the fluorosurfactant include hexaethylene glycol (1,1,2,2,3,3-hexafluoropentyl) ether, 1,1,2,2-tetrafluorooctyl (1,1,2,2). , -Tetrafluoropropyl) ether, sodium perfluorododecyl sulfonate, and the like.

  Examples of the silicone surfactant include SH21 series and SH28 series (Toray Dow Corning Co., Ltd.).

  The content of the surfactant in the composition used for producing the porous silica membrane of the present invention is the ratio of the surfactant to the silicon atom of the total hydrolyzable group-containing silane in the composition, and the resulting porous silica membrane From the viewpoint of the surface property, it is usually 0.001 (mol / mol) or more, preferably 0.002 (mol / mol) or more, more preferably 0.003 (mol / mol) or more, and usually 0. 05 (mol / mol) or less, preferably 0.04 (mol / mol) or less, more preferably 0.03 (mol / mol) or less.

<Composition of composition>
The components used in the composition described above are mixed to prepare a composition used for producing the porous silica membrane of the present invention. At this time, there is no limitation on the order of mixing the components. In addition, each component may be mixed all at once, or may be mixed continuously or intermittently in two or more times.

  However, in order to control the sol-gel reaction, which has heretofore been difficult to control, and to make the composition more industrially advantageous, it is preferable to mix in the following manner. That is, alkoxysilane containing no fluorine, water, solvent, catalyst, and fluorine-containing silane as necessary are mixed, and the mixture (hereinafter sometimes referred to as “alkoxysilane mixture”) is a certain sol-gel reaction. (Aging) causes the alkoxysilane to be hydrolyzed and dehydrated polycondensed to some extent. On the other hand, fluorine-containing silane, water, solvent, and catalyst can be mixed, and the mixture (hereinafter sometimes referred to as “fluorine-containing silane mixture”) can be hydrolyzed and dehydrated and polycondensed to some extent as described above. . And when using an organic polymer as a casting_mold | template material, an organic polymer is mixed with an alkoxysilane mixture and / or a fluorine-containing silane mixture, and a composition is prepared. Thereby, the affinity of silane and the organic polymer as a template material can be maintained under sol-gel reaction conditions. The aging may be performed after mixing the mixture and the organic polymer. Finally, a fluorine-containing silane mixture can be mixed with an alkoxysilane mixture to prepare a composition used for producing the porous silica membrane of the present invention.

<Aging>
(Aging of alkoxysilane mixture and / or fluorine-containing silane mixture)
In the ripening, heating is preferably performed in order to advance hydrolysis / dehydration polycondensation reaction of alkoxysilane and fluorine-containing silane. The heating condition is not particularly limited as long as it does not exceed the boiling point of the solvent to be used, but is usually 5 ° C. or higher, more preferably 10 ° C. or higher, 20 ° C. or higher, and most preferably 30 ° C. or higher. When the heating temperature is too low, sufficient sol-gel reaction does not proceed, and the growth of the condensate of alkoxysilane and fluorine-containing silane is insufficient, so that the strength of the formed film may be lowered. Moreover, if sufficient sol-gel reaction does not advance, when using an organic polymer as a casting | molding material, affinity with an organic polymer may not be acquired. On the other hand, the upper limit of the heating temperature is preferably 90 ° C. or less, and more preferably 80 ° C. or less. If the heating temperature is too high, the condensation reaction of the alkoxysilane proceeds too much, the condensate may form a precipitate, and the alkoxysilane mixture and the fluorine-containing silane mixture may become non-uniform. If the reaction temperature is too high, the molecular motion of the organic polymer, which is the template material in the silane mixture, becomes intense, and the affinity between the silane and the organic polymer may not be controlled.

  The aging time with heating is not limited, but is usually 0 minutes or more, preferably 10 minutes or more, more preferably 20 minutes or more, more preferably 30 minutes or more, and usually 20 hours or less, preferably 15 hours or less. More preferably, it is 8 hours or less, More preferably, it is 4 hours or less. If the aging time is too short, it may be difficult to proceed the reaction uniformly. If the aging time is too long, the aging temperature needs to be lowered, and the sol-gel reaction does not proceed sufficiently. ) May not be obtained.

  Furthermore, although there is no restriction | limiting in the pressure conditions at the time of ageing | curing | ripening of an alkoxysilane mixture and a fluorine-containing silane mixture, Usually, it is preferable to age | cure | ripen by a normal pressure. When the pressure changes, the boiling point of the solvent also changes, and the solvent during aging volatilizes (evaporates), which may change the composition ratio and lower the stability of the mixture.

  Moreover, it is preferable that the composition used after the aging and before the film forming step is further mixed with an organic solvent and diluted. Thereby, the sol-gel reaction rate in a composition can be reduced, and it becomes possible to maintain the pot life of a composition long. Further, from the viewpoint of yield in the production of the silica porous membrane, it is preferable to perform aging without heating. Aging without heating may be performed after the preparation of the composition. From the viewpoint of the pot life of the composition, a neutralization step or a catalyst removal step may be performed.

{Film forming process}
In the film forming step, a silica-based precursor film is manufactured by applying and spreading a composition used for manufacturing the above-described porous silica film of the present invention on a substrate.

  The film forming process may be performed once, but may be performed twice or more. For example, a porous silica film having a laminated structure can be formed by performing the film forming process twice or more through a rough drying process described later. This is useful, for example, when it is desired to form a porous silica film having different refractive indexes.

<Base material>
Any substrate can be used for forming the silica-based precursor film depending on the application. Among these, it is preferable to use a transparent base material (translucent base material) made of a general-purpose material.

  Examples of base materials include silicate glass, high silicate glass, alkali silicate glass, lead alkali glass, soda lime glass, potash lime glass, barium glass and other silicate glasses, borosilicate glass, alumina silicate glass, phosphoric acid Glass such as salt glass and tempered glass thereof; acrylic resin such as polymethyl methacrylate and cross-linked acrylate; aromatic polycarbonate resin such as bisphenol A polycarbonate; polyester resin such as polyethylene terephthalate; amorphous polyolefin resin such as polycycloolefin , Epoxy resins, styrene resins such as polystyrene, polysulfone resins such as polyethersulfone, polyetherimide resins, and synthetic resins such as tetrafluoroethylene-ethylene copolymer (ETFE).

  Among these, glass, polyetherimide resin, and polysulfone resin are preferable from the viewpoint of dimensional stability, and soda lime glass is preferable in terms of price. Furthermore, it is also preferable to use tempered glass from the viewpoint of impact resistance. In addition, the cover glass used for solar cells capable of photoelectric conversion even in the near-infrared light, such as single crystal solar cells and other crystal solar cells, is near red due to the divalent iron ions contained in ordinary soda-lime glass. Since it has absorption in the outer region, it is more preferable to use white plate tempered glass having improved light transmittance by reducing the iron ion content and having excellent impact strength.

  In addition, these may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

The dimensions of the substrate used in the present invention are arbitrary. However, when a plate-like substrate is used as the translucent substrate, the thickness of the substrate is preferably 0.01 mm or more, more preferably 0.05 mm or more, from the viewpoint of mechanical strength and gas barrier properties. 0.1 mm or more is more preferable. The thickness is preferably 80 mm or less, more preferably 50 mm or less, more preferably 30 mm or less, more preferably 10 mm or less, and particularly preferably 3 mm or less from the viewpoint of weight reduction and light transmittance. Further, the size (area) of the translucent substrate is preferably 0.1 m ² or more, more preferably 0.5 m ² or more, and particularly preferably 1 m ² or more from the viewpoint of obtaining an optical effect. Although there is no restriction | limiting in particular in an upper limit, Usually, 100 m < ² > or less is preferable and 50 m < ² > or less is more preferable.

In particular, when the porous silica film of the present invention is used as an optical functional layer, the porous silica film is preferably formed on a substrate having a certain size or more. That is, the area of the substrate is preferably 0.0025M ² or more, more preferably 0.05 m ² or more, more preferably 0.1 m ² or more, 1 m ² or more is most preferred. If it is smaller than this size, there is a possibility that the optical characteristics do not sufficiently appear.

Moreover, the center line average roughness of the silica porous film forming surface of the substrate is also arbitrary. However, from the viewpoint of the film forming property of the porous silica membrane to be formed, the center line average roughness is preferably 10 nm or less, more preferably 8 nm or less, still more preferably 5 nm or less, and particularly preferably 3 nm or less. In addition, the maximum height R _max of the surface roughness of the substrate is preferably 100 μm or less, particularly preferably 10 μm or less, from the viewpoint of the film forming property of the silica porous film to be formed.
The maximum height _{R max} of the central line average roughness and surface roughness, JIS-B0601: universal surface roughness tester in accordance with the 1994 (e.g., Ltd. Tokyo Seimitsu Co. Surfcom 570A) is measured by.

<Film forming method>
In the present invention, there is no particular limitation on the film forming method of the composition used for the production of the silica porous film of the present invention on the substrate, for example, spin coater, spray coater, die coater, bar coater, table coater, applicator, Examples thereof include a coating method using a doctor blade coater, a dip coating method, an ink jet method, a screen printing method, a gravure printing method, a flexographic printing method, and the like.

  In the dip coating method, the substrate may be pulled up by dipping in the composition used for producing the porous silica membrane of the present invention at an arbitrary speed. The pulling speed at this time is not limited, but is usually 0.01 mm / second or more, preferably 0.05 mm / second or more, more preferably 0.1 mm / second or more, and usually 50 mm / second or less, preferably 30 mm / second. Second or less, more preferably 20 mm / second or less. If the pulling speed is too slow or too fast, the film thickness may be uneven. On the other hand, although there is no restriction | limiting in the speed | rate which immerses a base material in a composition, Usually, it is preferable to immerse a base material in a composition at a speed | rate comparable as a raising speed | rate. Further, the immersion may be continued for an appropriate time from when the substrate is immersed in the composition to when the substrate is pulled up. There is no limitation on the duration of this immersion, but it is usually 1 second or more, preferably 3 seconds or more, more preferably 5 seconds or more, and usually 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less. is there. If this time is too short, the adhesion to the substrate may be low, and if it is too long, a film may be formed during the immersion and the smoothness may be low.

  Furthermore, when the composition used for producing the porous silica film of the present invention is applied by spin coating, the rotation speed is usually 10 revolutions / minute or more, preferably 50 revolutions / minute or more, more preferably 100 revolutions / minute. Min. Or more, and usually 100,000 revolutions / minute or less, preferably 50,000 revolutions / minute or less, more preferably 10,000 revolutions / minute or less. If the rotational speed is too slow, the film thickness may be uneven. If the rotational speed is too fast, the vaporization of the solvent tends to proceed and the reaction such as hydrolysis of alkoxysilanes does not proceed sufficiently and the water resistance may be low.

  In particular, in order to obtain a silica-based precursor film in a stable state regardless of the composition of the sol-gel reaction during film formation, the distance between the discharge part of the composition and the substrate is controlled, It is preferable to cast the composition. By forming a film in a limited space formed from the discharge part and the base material, the sol-gel reaction can be advanced in a certain environment, and a homogeneous silica-based precursor film can be formed. Specifically, the distance between the discharge part of the composition and the substrate is preferably 100 μm or less, more preferably 80 μm or less, further preferably 70 μm or less, and most preferably 50 μm or less. When this distance exceeds 100 μm, a difference in the progress of the sol-gel reaction occurs around the discharge part and around the substrate, and convection occurs in the film in a wet state, so that a porous silica film can be stably obtained. There is a tendency not to. On the other hand, the lower limit of this distance is preferably 0.1 μm or more, more preferably 0.3 μm or more, further preferably 0.5 μm or more, and most preferably 0.8 μm or more. If it is less than 0.1 μm, the share at the time of casting into the composition increases, and the sol-gel reaction may not proceed stably.

  Furthermore, in order to realize reliable film thickness control over a wide range (large area) as an optical functional layer, a method using a die coater, bar coater, table coater, applicator, doctor blade coater, etc. is preferable. The method used is more preferable.

  In the die coating method, the composition used for producing the porous silica membrane of the present invention is supplied at a constant flow rate from the solution supply point, and the silica-based precursor membrane is formed on the substrate surface by discharging it from the die lip through the slit. In this case, the target silica porous film can be formed by conveying the substrate at a constant speed.

The width of the slit is not particularly limited, but is usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and usually 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less. If the width of the slit is less than the lower limit, there is a risk of clogging due to contamination, and if it exceeds the upper limit, a uniform film may not be formed.
The gap (distance) between the die lip (slit) and the substrate is not particularly limited, but is usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, more preferably 30 μm or more, and usually By setting the thickness within a range of 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, a high-quality silica-based precursor film can be obtained.

  The discharge flow rate from the die lip is not particularly limited, but is usually 1 to 100 cc / min, preferably 1 to 50 cc / min, more preferably 1 to 20 cc / min, further preferably 2 to 10 cc / min, most preferably 3 ~ 6cc / min. If the discharge flow rate is lower than the lower limit value, the slit speed accuracy at the time of casting must be strict, so that it is difficult to increase the area of the substrate. On the other hand, when the above upper limit is exceeded, convection may occur in the discharged composition, and a stable wet film may not be formed.

  The coating speed is not particularly limited, but is usually 5 to 300 mm / second, preferably 10 to 200 mm / second, more preferably 20 to 100 mm / second, further preferably 30 to 80 mm / second, and most preferably 40 to 60 mm. / Sec. If the coating speed is lower than the lower limit, the casting conditions of the silica-based precursor film in the film forming process must be precisely controlled, which may impair productivity. If the upper limit is exceeded, the film forming process In this case, shear stress is applied to the silica-based precursor film, and the structure composed of the organic polymer as a template material and the silica component may be destroyed.

  The coating stop time is not particularly limited, but is usually 0.1 to 3 seconds, preferably 0.1 to 2 seconds, more preferably 0.2 to 1 second, and further preferably 0.2 to 0.8 seconds. Most preferably, it is 0.3 to 0.6 seconds. If the coating stop time is less than the above lower limit value, the interface state between the base material and the silica-based precursor film is not stable, the adhesion with the base material is lowered, the leveling of the film surface does not progress, and the appearance of the film is not improved. If the above upper limit is exceeded, the sol-gel reaction at the interface between the base material and the silica-based precursor film may proceed excessively and local defects may occur during casting.

  Although there is no restriction | limiting in particular in coating distance, Usually, 0.05-500m, Preferably it is 0.1-300m, More preferably, it is 0.5-100m, More preferably, it is 0.8-50m, Most preferably, it is 1-5m. It is. If the coating distance is less than the above lower limit value, there is a fear that the unstable state in the initial stage of casting in the film forming process may be exerted on the entire silica-based precursor film, and if the above upper limit value is exceeded, local non-uniformity in the composition There is a possibility of affecting the surface properties of the porous silica membrane from which the structure is obtained.

The leveling accuracy of the die lip and the substrate support is usually ± 5 μm or less, preferably ± 2 μm or less, more preferably ± 1 μm or less, so that the coating can be performed with good reproducibility.
The shape of the die that can be used is not particularly limited as long as the solution can be uniformly distributed in the lateral direction. Examples include a T-die shape, a fishtail die shape, or a coat hanger die shape that is used during general film casting. Furthermore, it is desirable to have a die lip interval adjustment mechanism in order to make the distribution in the die lateral direction more uniform.

  Although there is no restriction | limiting in particular in the wet film thickness at the time of film forming, Usually, it is 0.1-100 micrometers, 0.5-80 micrometers is preferable, 1-55 micrometers is more preferable, 5-40 micrometers is more preferable, 10-25 micrometers Is most preferred. If this range is exceeded, it will be difficult to control the progress of the sol-gel reaction of the composition in the film-forming process, and the film will be easily affected by the wettability with the base material. The appearance may deteriorate.

  For example, in the case of die coating, a mechanism in which the wet film thickness is controlled by the discharge liquid amount and the moving speed of the substrate is preferable, usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and usually 60 μm or less, preferably 50 μm. In the following, a uniform silica porous film with less coating unevenness can be obtained by setting the thickness to 40 μm or less.

<Film forming environment>
Although there is no restriction | limiting in particular in the relative humidity at the time of performing a film forming process, The more stable continuous coating is attained by controlling a relative humidity.

  For example, the relative humidity is usually 5% RH or more, preferably 10% RH or more, more preferably 15% RH or more, more preferably 20% RH or more, and usually 85% RH or less, preferably 80% RH or less, more Preferably, the silica-based precursor film is formed in an environment of 75% or less RH.

  Although there is no restriction | limiting in the temperature at the time of performing a film forming process, Usually, 0 degreeC or more, Preferably it is 10 degreeC or more, More preferably, it is 15 degreeC or more, More preferably, it is 20 degreeC or more, Most preferably, it is 25 degreeC or more. ° C or lower, preferably 80 ° C or lower, more preferably 70 ° C or lower, more preferably 60 ° C or lower, and most preferably 50 ° C or lower. If the temperature at the time of producing the silica-based precursor film is too low, the progress of the sol-gel reaction may be slow and a homogeneous silica-based precursor film may not be obtained. If it is too high, the condensation reaction will occur rapidly. As a result, a large amount of unhydrolyzed alkoxysilane remains, which may affect the durability of the resulting porous silica membrane.

  In addition, the degree of cleanliness when performing the film forming process is not particularly limited, but it is usually from the viewpoint of suppressing the progress of the sol-gel reaction around the film defects and the core around the contamination present on the substrate. The number of dust having a dust diameter of 0.5 μm or more is preferably 3,000,000 or less, more preferably 50,000 or less, and even more preferably 5,000 or less.

  Moreover, there is no restriction | limiting in the atmosphere in a film forming process. For example, the silica-based precursor film may be formed in an air atmosphere, and for example, the silica-based precursor film may be formed in an inert atmosphere such as argon.

<Pretreatment>
In the method for producing a porous silica membrane of the present invention, the wettability of the composition and the silica-based precursor to be produced are formed before forming the composition used for producing the porous silica membrane of the present invention on the substrate. From the viewpoint of film adhesion, the substrate may be subjected to a surface treatment. Examples of such surface treatment of the substrate include silane coupling treatment, corona treatment, UV ozone treatment, and plasma treatment. Such surface treatment may be performed alone or in any combination of two or more.

<Post-processing>
(Coarse drying)
In the method for producing a porous silica membrane of the present invention, after the above-mentioned film formation step, rough drying is carried out by roughly drying the silica precursor membrane for the purpose of removing alcohols or catalysts in the silica precursor membrane. You may perform a process. By performing the coarse drying process, the alcohol, water and catalyst in the silica-based precursor film are removed, so that the organic polymer (template material) and silica component present in the precursor film are in a stable state. And the structure of the silica-based precursor film can be stabilized.

The method of rough drying in the rough drying step is not limited. For example, heating drying, reduced pressure drying, ventilation drying, etc. are mentioned. These may be implemented alone or in combination of two or more.
The means for rough drying is also optional. For example, when rough drying is performed by heat drying, examples of the heat drying means include a hot plate, an oven, infrared irradiation, electromagnetic wave irradiation, and the like. Moreover, as a means of ventilation heating drying, a ventilation drying oven etc. are mentioned, for example. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Although the temperature at the time of rough drying is not limited, it is usually preferably room temperature or higher. In particular, when performing heat drying, the temperature is usually 20 ° C. or higher, preferably 30 ° C. or higher, more preferably 40 ° C. or higher, most preferably 60 ° C. or higher, and usually 200 ° C. or lower, preferably 180 ° C. or lower, more preferably. Is preferably 150 ° C. or lower, most preferably 100 ° C. or lower. In addition, the temperature at the time of heat drying may be constant, but may vary.

The pressure at the time of rough drying is not limited, but particularly when drying under reduced pressure, it is usually not more than normal pressure, preferably not more than 10 kPa, more preferably not more than 1 kPa.
Although the humidity during rough drying is not limited, in order to prevent moisture absorption of the silica-based precursor film, it is usually preferable to be about 60% RH or less, preferably 30% RH or less at normal pressure, or a vacuum state (humidity 0 % RH).

  The atmosphere during rough drying is not limited, and may be an air atmosphere, an inert gas atmosphere such as a nitrogen atmosphere, or a vacuum atmosphere. These may be selected in consideration of the characteristics of the silica-based precursor film. However, it is usually preferable to have a clean atmosphere.

  The rough drying time is not limited, and any alcohol, water, and catalyst in the silica-based precursor film can be removed, but conditions such as temperature, pressure, and humidity during rough drying, and the porous silica film of the present invention It is preferable to determine in consideration of the boiling points of alcohols and solvents contained in the composition used in the production of the above, the process speed, the characteristics of the silica-based precursor film, and the like. The rough drying time is usually 1 second or longer, preferably 1 minute or longer, more preferably 1 hour or longer, and usually 100 hours or shorter, preferably 24 hours or shorter, more preferably 3 hours or shorter.

(Acid / base treatment)
The silica-based precursor film can be brought into contact with an acid or a base after the film forming process described above. This step is preferable because the hydrolysis condensation reaction of alkoxysilanes in the silica-based precursor film can be promoted, and the structure of the silica-based precursor film can be maintained and a stable silica porous film can be formed.

  Preferable acids to be contacted include acids that are easily vaporized such as hydrogen chloride, formic acid, acetic acid, and trifluoroacetic acid. These acids may be used individually by 1 type, and may use 2 or more types together. Preferred bases include ammonia, methylamine, dimethylamine, trimethylamine, acylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, n-butylamine, cyclopentylamine, cyclohexylamine and the like. These bases may be used alone or in combination of two or more.

  Examples of the method for bringing the silica-based precursor film into contact with an acid or a base include a method using an acid or base liquid, solution or vapor. Moreover, an acid or a base can be dissolved in an organic solvent used in the extraction step described later and contacted simultaneously with the extraction step.

  Further, heating may be performed during the acid / base treatment. The heating temperature is usually room temperature or higher, preferably 40 ° C. or higher, more preferably 100 ° C. or higher, preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and particularly preferably 120 ° C. or lower.

  The time for performing the acid / base treatment is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 30 seconds or more, preferably 10 minutes or more, more preferably 30 minutes or more, and usually 5 hours or less, preferably 2 hours or less, more preferably 1 hour or less.

The pressure during the acid / base treatment is arbitrary as long as the effects of the present invention are not significantly impaired, but may be a reduced pressure environment. When heating is performed, the pressure is usually 0.2 MPa or less, preferably 0.15 MPa. Hereinafter, it is more preferably set to 0.1 MPa or less. On the other hand, the lower limit of the pressure is not limited, but is usually 10 ⁻⁴ MPa or more, preferably 10 ⁻³ MPa or more, more preferably 10 ⁻² MPa or more. If the pressure is too low, the volatilization of alcohol proceeds more than the sol-gel reaction of alkoxysilane, and a silica porous film with high hygroscopicity is likely to be formed, which may affect the environmental dependence of optical properties.

<Extraction process>
After the film-forming process described above, the silica-based precursor film is brought into contact with a solvent, if necessary, to perform an organic polymer extraction process as a template material. A porous structure having a higher porosity can be obtained by removing the organic polymer of the template material from the structure formed by the silica component made of alkoxysilane by contact with the solvent. Furthermore, since the obtained porous silica film has a low refractive index, high optical characteristics are realized.

  The solvent used for the extraction is not particularly limited, but a substance having a high affinity with the organic polymer as the template material is preferable. This is because if the solvent has a high affinity, the organic polymer is easily dissolved, and the organic polymer is easily removed from the structure formed by the silica component. As the solvent, a polar solvent is preferable, and among them, monohydric alcohols, polyhydric alcohols, ketones, ethers, esters, amides, or two or more hydrophilic solvents are preferable. When combining two or more kinds of hydrophilic solvents, they may be used in combination or may be combined by treating each solvent alone. Furthermore, the same kind of treatment liquid can be repeatedly acted on.

  The extraction method is not particularly limited. For example, the silica-based precursor film is immersed in a solvent, the surface of the silica-based precursor film is washed with a solvent, the solvent is sprayed on the silica-based precursor film, and the solvent vapor is blown onto the silica-based precursor film. The method is mentioned. It is also possible to extract the organic polymer positively by immersing the silica-based precursor film in a solvent and utilizing ultrasonic waves or stirring the solvent.

  Moreover, you may heat in the case of extraction. In this case, the heating temperature is usually 200 ° C. or lower. Preferably it is 180 degrees C or less, More preferably, it is 120 degrees C or less. Moreover, it is usually room temperature or higher, preferably 40 ° C. or higher, more preferably 60 ° C. or higher.

  As described above, by performing the extraction treatment, it is possible to obtain a laminate in which a porous silica film having a high porosity is formed on a substrate.

<Drying process>
The drying step is a step of removing the solvent used for extraction in the extraction step from the silica-based precursor film.

At this time, the drying temperature is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 200 ° C. or less, preferably 180 ° C. or less, more preferably 120 ° C. or less, further preferably 100 ° C. or less, and usually room temperature or more. The temperature is preferably 40 ° C. or higher, more preferably 60 ° C. or higher.
Moreover, the atmosphere in a drying process is arbitrary unless the effect of this invention is impaired remarkably, For example, a vacuum environment and an inert gas environment may be sufficient.

<Heating process>
After the film forming process described above, a heating process is performed in which the silica-based precursor film formed with the composition of the present invention is heated. By the heating step, the organic solvent and water in the composition of the present invention in the silica-based precursor film are dried and removed, and the film is cured, whereby the porous silica film of the present invention is formed.

  The method of the heat treatment is not particularly limited, but as an example, an in-furnace bake method in which a substrate is placed in a heating furnace (baking furnace) and a silica-based precursor film made of the composition of the present invention is heated, a plate ( A hot plate system in which a base material is mounted on a hot plate and the silica-based precursor film made of the composition of the present invention is heated through the plate, and a heater is disposed on the upper surface side and / or the lower surface side of the base material. And a method of heating a silica-based precursor film made of the composition of the present invention by irradiating an electromagnetic wave (for example, infrared rays) from a heater.

  There is no restriction on the heating temperature, and it is optional as long as the silica-based precursor film made of the composition of the present invention can be cured, but it is usually 80 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher, and further preferably 150 ° C. As described above, it is most preferably 200 ° C. or higher, usually 600 ° C. or lower, preferably 550 ° C. or lower, more preferably 500 ° C. or lower, and most preferably 450 ° C. or lower. If the heating temperature is too low, there is a possibility that the refractive index of the resulting film (that is, the porous silica film of the present invention) will not be lowered or colored. On the other hand, if the heating temperature is too high, the adhesion between the substrate and the porous silica film of the present invention may be reduced. In the heating step, the heating may be performed continuously at the heating temperature, but the heating may be performed intermittently.

  When heating, the rate of temperature increase is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 ° C./min or more, preferably 10 ° C./min or more, and usually 500 ° C./min or less, preferably 300. The temperature is raised at a temperature of ℃ / min or less. If the rate of temperature increase is too slow, the film may become dense, resulting in increased film strain and low water resistance. If the rate of temperature increase is too high, the film strain will increase and the water resistance will be low. There is a possibility of causing cracks, breakage, etc. of the porous membrane and the substrate.

  The heating time is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 30 seconds or more, preferably 1 minute or more, more preferably 2 minutes or more, and usually 5 hours or less, preferably 2 hours or less, More preferably, it is 1 hour or less. If the heating time is too short, the silica porous film may not be sufficiently cured, and if it is too long, the silica porous film and the substrate may be cracked or damaged.

The pressure at the time of heating is arbitrary as long as the effect of the present invention is not significantly impaired, but a reduced pressure environment is preferable. This is because, at a pressure equal to or higher than normal pressure, the vaporization of the solvent proceeds more than the reaction of alkoxysilane, and there is a possibility that the film has low water resistance. From this viewpoint, in the heating step, the pressure is usually 0.2 MPa or less, preferably 0.15 MPa or less, more preferably 0.1 MPa or less. On the other hand, the lower limit of the pressure is not limited, but is usually 10 ⁻⁴ MPa or more, preferably 10 ⁻³ MPa or more, more preferably 10 ⁻² MPa or more. If the pressure is too low, the vaporization of the solvent proceeds more than the reaction of alkoxysilane, which may result in a film with low water resistance.

  The atmosphere during heating is arbitrary as long as the effects of the present invention are not significantly impaired. Among them, an environment in which drying unevenness is unlikely to occur is preferable. Among these, it is preferable to perform heating in an air atmosphere. It is also possible to perform an inert gas treatment and perform heating in an inert atmosphere.

  As described above, by performing the heat treatment, the silica precursor film made of the composition of the present invention can be cured to obtain the porous silica film of the present invention.

<Surface treatment>
Surface treatment can be applied to the surface of the porous silica membrane of the present invention. This step makes it possible to further improve or impart hydrophobicity, lipophilicity, antifouling properties, antifogging properties, moisture resistance, fingerprint resistance, antistatic properties, and abrasion resistance.

  The composition for surface treatment is produced using, for example, a composition containing a fluorine-containing silane, an alkoxysilane not containing fluorine, water, an organic solvent, and, if necessary, a catalyst.

In order to perform the surface treatment, first, a composition as a raw material is prepared, applied to the surface of the porous silica film, and then heated.
Usually, a fluorine-containing silane, a fluorine-free alkoxysilane, water, an organic solvent, and if necessary, a composition further containing a catalyst is applied onto the silica porous membrane and reacted with silanol groups on the surface of the silica porous membrane, Immobilize silane on the surface.

  About the composition for surface treatment, the compounding component and the preparation method are demonstrated below.

  The material for the surface treatment is not particularly limited, and examples thereof include alkoxysilane and fluorine-containing silane. These materials are immobilized on the surface by dehydration condensation reaction with silanol groups on the surface of the porous silica film of the present invention, so that silanol groups that cause moisture absorption are removed, and the types of functional groups that silane has Depending on the, specific properties can be imparted to the surface.

(Alkoxysilane)
Examples of the alkoxysilane include trialkoxysilanes such as monoalkyltrialkoxysilane, dialkoxysilanes such as dialkyldialkoxysilane, and trialkylmonoalkoxysilanes. By performing the surface treatment with alkoxysilane, the hydrophobicity and moisture resistance can be improved.

<Trialkoxysilane>
There is no limitation on the type of trialkoxysilane. Examples of suitable ones include trialkoxysilanes such as trimethoxysilane, triethoxysilane, tri-n-propoxysilane, triisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, Methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltriisopropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri-n- Monoalkyltrialkoxysilanes such as propoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, isopropyltri-n-propoxysilane, phenyltrimethoxysilane, phenyltrie Kishishiran, phenyl tri -n- propoxysilane, phenyl trialkoxy silane such as phenyl triisopropoxy silane. In addition, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, in which an alkyl group substituted on a silicon atom has a reactive functional group, 3 -Triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-carboxypropyltrimethoxysilane, 3-trihydroxysilyl -1- Propane - such as sulfonic acid can also be used.

<Dialkoxysilane>
There is no restriction on the type of dialkoxysilane. Examples of suitable ones are methyldimethoxysilane, methyldiethoxysilane, methyldi-n-propoxysilane, methyldiisopropoxysilane, ethyldimethoxysilane, ethyldiethoxysilane, ethyldi-n-propoxysilane, ethyldiisopropoxy. Monoalkyl dialkoxysilanes such as silane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldiisopropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldi-n-propoxysilane, diethyldiiso Propoxysilane, di-n-propyldimethoxysilane, di-n-propylethoxysilane, di-n-propyldi-n-propoxysilane, di-n-propyldiisopropoxysilane, di Sopropyldimethoxysilane, diisopropylethoxysilane, diisopropyldi-n-propoxysilane, diisopropyldiisopropoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n-butyldi-n-propoxysilane Di-n-butyldiisopropoxysilane, di-sec-butyldimethoxysilane, di-sec-butyldiethoxysilane, di-sec-butyldi-sec-propoxysilane, di-sec-butyldiisopropoxysilane, di Dialkyl dialkoxysilanes such as tert-butyldimethoxysilane, di-tert-butyldiethoxysilane, di-tert-butyldi-n-propoxysilane, di-tert-butyldiisopropoxysilane, and diphenyldimethoxysilane Diphenyl diethoxy silane, diphenyl di -n- propoxysilane, diphenyl dialkoxysilane such as diphenyl diisopropoxy silane. Further, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane or the like in which an alkyl group substituted on a silicon atom has a reactive functional group can also be used.

<Trialkylmonoalkoxysilane>
There is no restriction | limiting in the kind of trialkylmonoalkoxysilane. Examples of suitable ones include trimethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, tri-n-propylmethoxysilane, tri-n-propylethoxysilane and the like.

<Other alkoxysilanes>
In addition to the above, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (triethoxysilyl) ethane, 1,4- Organic residues such as bis (trimethoxysilyl) benzene, 1,4-bis (triethoxysilyl) benzene, 1,3,5-tris (trimethoxysilyl) benzene bound two or more trialkoxysilyl groups Things can also be used.

  These alkoxysilanes may be used alone or in combination of two or more.

Among the above alkoxysilanes, a trialkylmonoalkoxysilane having 1 to 3 carbon atoms of an alkyl group is preferable for sufficiently improving hydrophobicity. Of these, trimethylmethoxysilane and trimethylethoxysilane are preferable. If the carbon chain of the alkyl group is too long, dehydration condensation reaction with the silanol group on the porous membrane surface cannot be performed due to steric hindrance and / or the alkyl group has antifouling property and abrasion resistance due to fluorine on the silica porous membrane surface of the present invention. There is a possibility of damage.

(Fluorine-containing silane)
By performing the surface treatment with the fluorine-containing silane, the amount of surface fluorine on the surface of the porous silica film can be further improved, and the hydrophobicity, antifouling property, moisture resistance, fingerprint resistance, and abrasion resistance can be improved.
There is no restriction | limiting in the kind of fluorine-containing silane. Examples of suitable ones include trifluorosilane, fluorotrimethoxysilane, fluorotriethoxysilane, trifluoromethyltrimethoxysilane, trifluoromethyltriethylsilane, trifluoromethyltrimethylsilane, trifluoromethyltrimethoxysilane, (3 , 3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trifluoropropyl) triethoxysilane, (3,3,3-trifluoropropyl) dimethylchlorosilane, 3- (3,3,3 -Trifluoropropyl) heptaethyltrisiloxane, (3,3,3-trifluoropropyl) methylcyclotrisiloxane, (3,3,3-trifluoropropyl) methylcyclotetrasiloxane, (3-heptafluoroisopropyl) propyl Torik Rosilane, pentafluoroethyltrimethoxysilane, nonafluorohexyltriethoxysilane, nonafluorohexyltrimethoxysilane, nonafluorohexyltrichlorosilane, nonafluorohexyldimethylchlorosilane, nonafluorohexylmethyldichlorosilane, nonafluorohexyltris (dimethylamino) Silane, nonafluorohexyldimethyl (dimethylamino) silane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) trimethoxysilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) trichlorosilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) methyldichlorosilane, (Trideca (Luolo-1H, 1H, 2H, 2H-octyl) dimethylchlorosilane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) silane, (Tridecafluoro-1H, 1H, 2H, 2H-octyl) silane, ( Heptadecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, (Heptadecafluoro-1H, 1H, 2H, 2H-octyl) trimethoxysilane, (Heptadecafluoro-1H, 1H, 2H, 2H- Octyl) trichlorosilane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) methyldichlorosilane, (heptadecafluoro-1H, 1H, 2H, 2H-octyl) dimethylchlorosilane, (heptadecafluoro-1H, 1H 2H, 2H-octyl) silane, (heptadecafluoro-1H, 1H 2H, 2H-octyl) silane, (perfluorodecyl) ethyltrichlorosilane, bis ((tridecafluoro-1,1,2,2-tetrahydrooctyl) -dimethylsiloxy) methylchlorosilane, bis ((tridecafluoro- 1,1,2,2-tetrahydrooctyl) -dimethylsiloxy) methylsilane, bis ((tridecafluoro-1,1,2,2-tetrahydrooctyl) -dimethylsiloxy) tetramethyldisiloxane, 5,5,6, 6,7,7,8,8,9,9,10,10,10-tridecafluoro-2- (tridecafluorohexyl) decyltrichlorosilane, heptadecatrifluorodecyltrimethoxysilane, pentafluorophenyltrimethoxy Silane, pentafluorophenyltriethoxysilane, hexadecuff Orododec-11-en-1-yltrimethoxysilane, hexadecafluorododec-11-en-1-yltrichlorosilane, 1,8-bis (trichlorosilylethyl) hexadecafluorooctane, m- (trifluoromethyl) phenyltri Methoxysilane, p-trifluoromethyltetrafluorophenyltriethoxysilane, pentafluorophenyldimethylchlorosilane, pentafluorophenylpropyldimethylchlorosilane, pentafluorophenylpropylmethyldichlorosilane, pentafluorophenylpropyltrichlorosilane, pentafluorophenylpropyltrimethoxysilane, perfluorosilane Examples include fluorooctylphenyltrichlorosilane.
These may be used alone or in combination of two or more.

  Among the above fluorine-containing silanes, a silane having a linear fluoroalkyl group having 6 to 10 carbon atoms is preferable for sufficient antifouling properties and wear resistance. Among these, nonafluorohexyltriethoxysilane, (tridecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane, and (heptadecafluoro-1H, 1H, 2H, 2H-octyl) triethoxysilane are preferable. If the carbon chain of the fluorine-containing silane is too short, the friction reduction effect by the fluoroalkyl group may be too low, and if the carbon chain is too long, the dehydration condensation reaction with the silanol group on the porous membrane surface may not be possible due to steric hindrance. is there.

  Although there is no restriction | limiting in particular in content of the alkoxysilane in the composition for surface treatment, Usually, 0.001 weight% or more, Especially 0.005 weight% or more is preferable, 0.01 weight% or more is more preferable, and 0.1%. More preferably, it is at least 05% by weight. Further, it is usually 10% by weight or less, particularly 5% by weight or less, and more preferably 3% by weight or less. If the alkoxysilane content in the surface treatment composition is too high, the silane concentration in the surface treatment composition may increase, and the polycondensation reaction between silanes may proceed. There is a possibility that the concentration becomes low and a sufficient surface treatment effect cannot be obtained.

(Organic solvent)
The composition used for the surface treatment contains an organic solvent. As the organic solvent, alcohols are most suitable when the material is only alkoxysilanes or alkylalkoxysilanes. Alcohols are preferred because they have an affinity for the alkoxysilanes or alkylalkoxysilanes, their hydrolysates, and partial condensates.

  There is no restriction on the type of alcohol. Examples of suitable ones include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl -1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol, 1-hexanol Monohydric alcohols such as 2-hexanol, 3-hexanol, ethylene glycol monomethyl ether, 2-ethoxyethanol, propylene glycol monomethyl ether, dihydric alcohols such as ethylene glycol and diethylene glycol, trihydric alcohols such as glycerin, cyclohexanol, etc. Alicyclic Alcohol, and other aromatic alcohols such as benzyl alcohol. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and ratios.

  Among these, monohydric alcohols and dihydric alcohols are preferable from the viewpoint of the hydrolysis reaction of the alkoxysilane contained, and monohydric alcohols are more preferable. Further, from the viewpoint of the surface properties of the obtained porous silica membrane, methanol, ethanol, 1-propanol, t-butanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 1-pentanol and the like are preferable. . Therefore, it is preferable to use at least one selected from these.

  In addition, from the viewpoint of facilitating the formation of the surface treatment structure and improving the wettability with the porous silica film, the boiling point of the organic solvent used is preferably 110 ° C. or less, more preferably 100 ° C. or less, and even more preferably 90 ° C. or less. As such a thing, methanol, ethanol, 1-propanol, t-butanol, 2-propanol etc. are preferable, for example. On the other hand, from the viewpoint of suppressing deformation of the porous structure in the heating step, the boiling point of the organic solvent is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. For example, 2-methyl-1-propanol, 1-butanol, and 1-pentanol are preferable.

  Furthermore, alcohols having different boiling points may be used as a mixture. In this case, in order to suppress azeotropy in each step, the difference in boiling points of the combined alcohols is preferably 5 ° C. or more, preferably 10 ° C. The above is more preferable, and 20 ° C. or higher is more preferable. Further, the ratio of alcohols on the high boiling point side to the total alcohols is usually 5% by weight or more, preferably 10% by weight or more, more preferably 40% by weight or more, further preferably 60% by weight or more, particularly preferably. 80% by weight or more. In addition, the upper limit of the said ratio is 98 weight% normally. If this upper limit is exceeded, the surface properties of the resulting silica porous membrane may be lowered, and if it is less than the lower limit, there is a risk that sufficient effects cannot be obtained.

  The composition used for the surface treatment of the porous silica membrane of the present invention may contain an organic solvent other than the alcohols. For example, an organic solvent other than alcohols can be used in order to further improve the wettability with the silica porous membrane and the film forming property in the surface treatment process.

  Examples of suitable organic solvents include ethers or esters such as methyl acetate, ethyl acetate, isobutyl acetate, ethylene glycol dimethyl ether, propylene glycol methyl ether acetate; ketones such as acetone and methyl ethyl ketone; formamide, N-methylformamide N-ethylformamide, N, N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylpyrrolidone, N -Formylmorpholine, N-acetylmorpholine, N-formylpiperidine, N-acetylpiperidine, N-formylpyrrolidine, N-acetylpyrrolidine, N, N'-diformylpiperazine, N, '- diformyl piperazine, N, N'- amides such as diacetyl piperazine; lactones γ- butyrolactone; tetramethylurea, N, ureas such as N'- dimethyl imidazolidine; and dimethyl sulfoxide.

  When the material contains fluorine-containing silane, it is preferable to use a fluorine-based solvent in addition to the alcohol. Fluoroalkyl groups of fluorine-containing silanes have low affinity for alcohol and other solvents, so the composition may not be uniform and phase separation may occur. However, fluorine-based solvents have an affinity for fluoroalkyl groups. Because of its high properties, phase separation can be prevented and the composition can be kept in a uniform liquid.

  Examples of suitable organic solvents include perfluorohexane, perfluorooctane, trifluoroxylene, 1H, 1H-trifluoroethanol, 1H, 1H-pentafluoropropanol, 6- (perfluoroethyl) hexanol, 1H, 1H. -Heptafluorobutanol, 2- (perfluorobutyl) ethanol, 3- (perfluorobutyl) propanol, 6- (perfluorobutyl) hexanol, 2-perfluoropropoxy-2,3,3,3-tetrafluoropropanol, 2- (perfluorohexyl) ethanol, 3- (perfluorohexyl) propanol, 6- (perfluorohexyl) hexanol, 2- (perfluorooctyl) ethanol, 3- (perfluorooctyl) propanol, 6- (perfluorooxy) Chill) hexanol, 2- (such as perfluorodecyl) ethanol.

  The amount of the organic solvent used is arbitrary as long as the effect of the surface treatment is not significantly impaired, but the content in the surface treatment composition is usually 10% by weight or more, preferably 20% by weight or more, and preferably 30% by weight or more. Is more preferable, and 40% by weight or more is more preferable. Also, it is usually 99.99% by weight or less, preferably 99.9% by weight or less, and more preferably 99% by weight or less. If the amount of the organic solvent used is too small, the silane concentration in the composition for surface treatment will increase, and the polycondensation reaction between silanes may proceed. If it is too large, the silane concentration will be low and sufficient. There is a possibility that the surface treatment effect cannot be obtained.

(water)
The content of water in the surface treatment composition is not particularly limited, but the ratio of water to silicon atoms of all alkoxysilanes in the surface treatment composition is usually 1 (mol / mol) or more, preferably 3 (Mol / mol) or more, more preferably 5 (mol / mol) or more. Further, it is usually 30 (mol / mol) or less, preferably 20 (mol / mol) or less. If the ratio of water to silicon atoms in all alkoxysilanes is smaller or larger than the above range, it may be difficult to control the hydrolysis reaction of silane. The amount of water can be calculated by the Karl Fischer method (coulometric titration method).

(catalyst)
The composition for surface treatment may contain a catalyst, and as the catalyst, for example, a substance that promotes the hydrolysis and dehydration condensation reaction of alkoxysilane described above can be arbitrarily used.

  Examples include hydrofluoric acid, phosphoric acid, boric acid, hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, maleic acid, methylmalonic acid, stearic acid, linolenic acid, benzoic acid, phthalic acid, citric acid, succinic acid. Acids such as lactic acid, malic acid, mandelic acid, pyruvic acid, malonic acid, adipic acid, glutaric acid, salicylic acid, aconitic acid; amines such as ammonia, butylamine, dibutylamine, triethylamine; tetramethylammonium hydroxide, water Basic ammonium salts such as tetraethylammonium oxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide; bases such as pyridine; Lewis acids such as acetylacetone complex of aluminum; and other acidic and basic amino acids .

  Moreover, a metal chelate compound is also mentioned as an example of a catalyst. Examples of the metal species of the metal chelate compound include titanium, aluminum, zirconium, tin, and antimony. Specific examples of the metal chelate compound include the following.

  Examples of the aluminum complex include di-ethoxy mono (acetylacetonato) aluminum, di-n-propoxy mono (acetylacetonato) aluminum, di-isopropoxy mono (acetylacetonato) aluminum, di-n- Butoxy mono (acetylacetonato) aluminum, di-sec-butoxy mono (acetylacetonato) aluminum, di-tert-butoxy mono (acetylacetonato) aluminum, monoethoxy bis (acetylacetonato) aluminum, mono -N-propoxy bis (acetylacetonato) aluminum, monoisopropoxy bis (acetylacetonato) aluminum, mono-n-butoxy bis (acetylacetonato) aluminum, mono-sec-but Si-bis (acetylacetonato) aluminum, mono-tert-butoxy bis (acetylacetonato) aluminum, tris (acetylacetonato) aluminum, diethoxy mono (ethylacetoacetate) aluminum, di-n-propoxy mono ( Ethyl acetoacetate) aluminum, diisopropoxy mono (ethyl acetoacetate) aluminum, di-n-butoxy mono (ethyl acetoacetate) aluminum, di-sec-butoxy mono (ethyl acetoacetate) aluminum, di-tert- Butoxy mono (ethyl acetoacetate) aluminum, monoethoxy bis (ethyl acetoacetate) aluminum, mono-n-propoxy bis (ethyl acetoacetate) aluminum, mono Sopropoxy bis (ethyl acetoacetate) aluminum, mono-n-butoxy bis (ethyl acetoacetate) aluminum, mono-sec-butoxy bis (ethyl acetoacetate) aluminum, mono-tert-butoxy bis (ethyl acetoacetate) Examples thereof include aluminum chelate compounds such as aluminum and tris (ethylacetoacetate) aluminum.

  Titanium complexes include triethoxy mono (acetylacetonato) titanium, tri-n-propoxy mono (acetylacetonato) titanium, triisopropoxy mono (acetylacetonato) titanium, tri-n-butoxy mono (acetyl). Acetonato) titanium, tri-sec-butoxy mono (acetylacetonato) titanium, tri-tert-butoxy mono (acetylacetonato) titanium, diethoxy bis (acetylacetonato) titanium, di-n-propoxy bis (Acetylacetonato) titanium, diisopropoxy bis (acetylacetonato) titanium, di-n-butoxy bis (acetylacetonato) titanium, di-sec-butoxy bis (acetylacetonato) titanium, di-tert -Butoxy bis (ace Ruacetonate) titanium, monoethoxy tris (acetylacetonato) titanium, mono-n-propoxy tris (acetylacetonato) titanium, monoisopropoxy tris (acetylacetonato) titanium, mono-n-butoxy tris (acetyl) Acetonato) titanium, mono-sec-butoxy-tris (acetylacetonato) titanium, mono-tert-butoxy-tris (acetylacetonato) titanium, tetrakis (acetylacetonato) titanium, triethoxy mono (ethylacetoacetate) titanium , Tri-n-propoxy mono (ethyl acetoacetate) titanium, triisopropoxy mono (ethyl acetoacetate) titanium, tri-n-butoxy mono (ethyl acetoacetate) titanium, tri-sec-butyl Xy mono (ethyl acetoacetate) titanium, tri-tert-butoxy mono (ethyl acetoacetate) titanium, diethoxy bis (ethyl acetoacetate) titanium, di-n-propoxy bis (ethyl acetoacetate) titanium, diiso Propoxy bis (ethyl acetoacetate) titanium, di-n-butoxy bis (ethyl acetoacetate) titanium, di-sec-butoxy bis (ethyl acetoacetate) titanium, di-tert-butoxy bis (ethyl acetoacetate) Titanium, monoethoxy tris (ethyl acetoacetate) titanium, mono-n-propoxy tris (ethyl acetoacetate) titanium, monoisopropoxy tris (ethyl acetoacetate) titanium, mono-n-butoxy tris (ethyl acetoacetate) Acetate) titanium, mono-sec-butoxy tris (ethyl acetoacetate) titanium, mono-tert-butoxy tris (ethyl acetoacetate) titanium, tetrakis (ethyl acetoacetate) titanium, mono (acetylacetonate) tris (ethyl aceto) Acetate) titanium, bis (acetylacetonato) bis (ethylacetoacetate) titanium, tris (acetylacetonato) mono (ethylacetoacetate) titanium and the like.

  Among those described above, acids or metal chelate compounds are preferable, and acids are more preferable in order to more easily control the hydrolysis and dehydration condensation reaction of the alkoxysilane compound. In addition, a catalyst may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The amount of the catalyst used is arbitrary as long as the effect of the surface treatment is not significantly impaired, but is usually 0.0001 mol times or more, particularly 0.0003 mol times or more, particularly preferably 0.001 mol times or more with respect to the alkoxysilane in the surface treatment composition. 0005 mol times or more is preferable, and usually 0.2 mol times or less, particularly 0.1 mol times or less, and particularly preferably 0.05 mol times or less. If the amount of catalyst used is too small, the hydrolysis reaction of silane will not proceed moderately and may not react with the silanol groups on the surface of the porous silica membrane. May produce a silica-based solid material that does not undergo surface treatment.

(PH)
The surface treatment composition preferably has a pH of 6 or less from the viewpoint of rapid surface treatment reaction. The pH of the composition is more preferably 5.5 or less, further preferably 5.0 or less, and particularly preferably 4.5 or less. By setting it within this range, the reaction between the silanol group on the surface of the porous silica membrane and the silane in the surface treatment composition can be rapidly advanced.

(Coating process)
There is no particular limitation on the method of distributing the surface treatment composition to the porous silica film. For example, a method of applying using a spin coater, spray coater, die coater, bar coater, table coater, applicator, doctor blade coater, etc. And a dip coating method, an ink jet method, a screen printing method, a gravure printing method, a flexographic printing method, and the like. In addition, there is a method in which the porous silica film is wiped with a cloth soaked with the surface treatment composition.

  In the dip coating method, the base material on which the porous silica film is formed may be dipped in the surface treatment composition and pulled up at an arbitrary speed. The pulling speed at this time is not limited, but is usually 0.01 mm / second or more, preferably 0.05 mm / second or more, more preferably 0.1 mm / second or more, and usually 100 mm / second or less, preferably 80 mm / second. Second or less, more preferably 50 mm / second or less. If the pulling speed is too slow or too fast, the film thickness may be uneven. On the other hand, although there is no restriction | limiting in the speed | rate which immerses a base material in a composition, Usually, it is preferable to immerse a base material in a composition at a speed | rate comparable as a raising speed | rate. Further, the immersion may be continued for an appropriate time from when the substrate is immersed in the composition to when the substrate is pulled up. There is no limitation on the duration of this immersion, but it is usually 1 second or more, preferably 3 seconds or more, more preferably 5 seconds or more, and usually 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less. is there. If this time is too short, it may be pulled up before the liquid level becomes stable, and it may not be distributed uniformly. If it is too long, a film may be formed during immersion and the smoothness may be lowered.

  Further, when the surface treatment composition is applied by spin coating, the rotation speed is usually 10 revolutions / minute or more, preferably 50 revolutions / minute or more, more preferably 100 revolutions / minute or more, and usually 30000 revolutions. / Min or less, preferably 10,000 revolutions / minute or less, more preferably 7000 revolutions / minute or less. If the rotational speed is too slow, there is a possibility that it cannot be distributed uniformly. If the rotational speed is too fast, the vaporization of the solvent tends to proceed, the reaction such as hydrolysis of silanes does not proceed sufficiently, and the reaction with the surface silanol does not proceed sufficiently. there is a possibility.

  Furthermore, in order to realize reliable film thickness control over a wide range (large area) as an optical functional layer, a method using a die coater, bar coater, table coater, applicator, doctor blade coater, etc. is preferable. The method used is more preferable.

  In the die coating method, the surface treatment composition is supplied on the surface of the porous silica film by supplying the surface treatment composition at a constant flow rate from the solution supply point and discharging it from the die lip through the slit. In this case, the surface treatment composition can be uniformly distributed by conveying the porous silica film-forming substrate at a constant speed.

The width of the slit is not particularly limited, but is usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and usually 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less. If the width of the slit is below the lower limit, there is a risk of clogging due to contamination, and if the slit width exceeds the upper limit, the surface treatment composition may not be uniformly distributed.
The gap (distance) between the die lip (slit) and the porous silica film is not particularly limited, but is usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more. Moreover, effective surface treatment can be performed by making it into the range of 100 micrometers or less normally, Preferably it is 80 micrometers or less, More preferably, it is 50 micrometers or less.

  The discharge flow rate from the die lip is not particularly limited, but is usually 1 to 100 cc / min, preferably 1 to 50 cc / min, more preferably 1 to 20 cc / min, further preferably 2 to 10 cc / min, most preferably 3 ~ 6cc / min. If the discharge flow rate is below the lower limit value, the slit speed accuracy during casting must be strict, and surface treatment in a large area tends to be difficult. On the other hand, when the above upper limit is exceeded, convection occurs in the discharged composition, and it may not be possible to distribute the surface treatment composition uniformly.

  The coating speed is not particularly limited, but is usually 5 to 300 mm / second, preferably 10 to 200 mm / second, more preferably 20 to 100 mm / second, further preferably 30 to 80 mm / second, and most preferably 40 to 60 mm. / Sec. If the coating speed is below or above the lower limit, the surface treatment composition may not be distributed uniformly.

  Although there is no restriction | limiting in particular in coating distance, Usually, 0.05-500m, Preferably it is 0.1-300m, More preferably, it is 0.5-100m, More preferably, it is 0.8-50m, Most preferably, it is 1-5m. It is. If the coating distance is less than the above lower limit value, there is a risk of affecting the entire treated surface in an unstable state at the initial stage of casting in the spreading step, and if the upper limit value is exceeded, local unevenness in the composition for surface treatment The structure may hinder the uniformity of the surface treatment.

The leveling accuracy of the support of the die lip and the porous silica film-forming substrate is usually ± 5 μm or less, preferably ± 2 μm or less, more preferably ± 1 μm or less, so that the coating can be applied with good reproducibility.
The shape of the die that can be used is not particularly limited as long as the solution can be uniformly distributed in the lateral direction. Examples include a T-die shape, a fishtail die shape, or a coat hanger die shape that is used during general film casting. Furthermore, it is desirable to have a die lip interval adjustment mechanism in order to make the distribution in the die lateral direction more uniform.

  Although there is no restriction | limiting in particular in the wet film thickness at the time of the composition for surface treatments, it is 0.1-100 micrometers normally, 0.5-80 micrometers is preferable, 1-55 micrometers is more preferable, and 5-40 micrometers is further. Preferably, 10 to 25 μm is most preferable. If it exceeds this range, the leveling effect is inferior, and the uniformity of the surface treatment may be deteriorated.

  For example, in the case of die coating, a mechanism in which the wet film thickness is controlled by the discharge liquid amount and the moving speed of the porous silica film-forming substrate is preferably 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and usually By setting the thickness within a range of 60 μm or less, preferably 50 μm or less, more preferably 40 μm or less, uniform surface treatment with less unevenness can be performed.

  Although there is no restriction | limiting in particular in the relative humidity at the time of performing the composition distribution process for surface treatments, further stable continuous surface treatment is attained by controlling a relative humidity.

  For example, the relative humidity is usually 5% RH or more, preferably 10% RH or more, more preferably 15% RH or more, more preferably 20% RH or more, and usually 85% RH or less, preferably 80% RH or less, more Preferably, the step of distributing the surface treatment composition is performed in an environment of 75% RH or less.

  Although there is no restriction | limiting in the temperature at the time of performing the composition distribution process for surface treatment, Usually, 0 degreeC or more, Preferably it is 10 degreeC or more, More preferably, it is 15 degreeC or more, More preferably, it is 20 degreeC or more, Most preferably, 25 degreeC or more Also, it is usually 100 ° C. or lower, preferably 80 ° C. or lower, more preferably 70 ° C. or lower, more preferably 60 ° C. or lower, and most preferably 50 ° C. or lower. If the temperature at which the surface treatment composition is distributed is too low, the progress of the reaction between the silane and the silanol groups on the surface of the porous silica membrane may be delayed, and a sufficient surface treatment effect may not be obtained. If it is too high, the dehydration (poly) condensation reaction between silanes becomes more dominant than the reaction between silane and silanol groups on the surface of the porous silica membrane, and the surface treatment may be insufficient.

  Further, the degree of cleanliness when performing the surface treatment composition distribution step is not particularly limited. However, from the viewpoint of suppressing the inhibition of the appearance of the film surface due to the adhesion of contaminants existing on the substrate, the dust diameter is usually 0. The number of dusts of 0.5 μm or more is preferably 3,000,000 or less, more preferably 50,000 or less, and even more preferably 5,000 or less.

  Moreover, there is no restriction | limiting in the atmosphere in the composition distribution process for surface treatment. For example, surface treatment may be performed in an air atmosphere, or may be performed in an inert atmosphere such as argon.

(Heating process)
After the above-described surface treatment composition distribution step, a heating step of heating the porous silica film on which the surface treatment composition is distributed is performed. By the heating step, the organic solvent and water in the surface treatment composition are dried and removed, and the silanol group on the surface of the porous silica membrane and the silane in the surface treatment composition undergo a dehydration condensation reaction, whereby the surface treatment is performed. Complete.

  The heat treatment method is not particularly limited. For example, an in-furnace bake method for heating a porous silica film in which a surface treatment composition is distributed in a heating furnace (baking furnace), on a plate (hot plate) A hot plate system for heating a porous silica film on which a porous silica film-forming substrate is mounted and a surface treatment composition is distributed through the plate, a heater on the upper surface side and / or lower surface side of the substrate And a method of heating the porous silica film on which the surface treatment composition is spread by irradiating an electromagnetic wave (for example, infrared rays) from a heater.

  There is no limitation on the heating temperature, and it is optional as long as the silanol group on the surface of the porous silica membrane and the silane in the composition for surface treatment can sufficiently proceed with the dehydration condensation reaction, but usually 40 ° C or higher, preferably 60 ° C. Above, more preferably 80 ° C. or more, further preferably 100 ° C. or more, and usually 500 ° C. or less, preferably 350 ° C. or less, more preferably 250 ° C. or less. If the heating temperature is too low, the dehydration condensation reaction between the silanol groups on the surface of the porous silica membrane and the silane in the composition for surface treatment may not proceed sufficiently. On the other hand, if the heating temperature is too high, the organic group of the silane in the surface treatment composition may cause a decomposition reaction. In the heating step, the heating may be performed continuously at the heating temperature, but the heating may be performed intermittently.

  When heating, the rate of temperature rise is arbitrary as long as the effect of the surface treatment is not significantly impaired, but is usually 1 ° C./min or more, preferably 10 ° C./min or more, and usually 500 ° C./min or less, preferably 300 The temperature is raised at a temperature of ℃ / min or less. If the rate of temperature rise is too slow, the porous silica membrane becomes dense with the progress of the dehydration condensation reaction between the silanol groups on the surface of the porous silica membrane and the silane in the surface treatment composition, resulting in increased membrane strain and water resistance. If the temperature elevation rate is too high, the silane in the surface treatment composition will evaporate, and sufficient surface treatment may not be performed.

  The heating time is arbitrary as long as the effect of the surface treatment is not significantly impaired, but is usually 30 seconds or more, preferably 1 minute or more, more preferably 2 minutes or more, and usually 5 hours or less, preferably 2 hours or less, More preferably, it is 1 hour or less. If the heating time is too short, there is a possibility that the dehydration condensation reaction between the silanol groups on the surface of the porous silica membrane and the silane in the composition for surface treatment will not proceed, and if it is too long, the silica porous membrane and the substrate will crack. May cause damage.

  The atmosphere for heating is arbitrary as long as the effect of the surface treatment is not significantly impaired, and among them, an environment in which drying unevenness is unlikely to occur is preferable. Among these, it is preferable to perform heating in an air atmosphere. It is also possible to perform an inert gas treatment and perform heating in an inert atmosphere.

  As described above, by performing the heat treatment, a dehydration condensation reaction between the silane in the surface treatment composition and the silanol group on the surface of the silica porous membrane proceeds, and a surface-treated silica porous membrane can be obtained. it can.

  The number of surface treatments may be repeated not only once but multiple times. Further, after a certain surface treatment, a different surface treatment may be performed.

[Laminate]
The porous silica membrane of the present invention produced by the above-described production method is formed in a film shape on a substrate directly or via another layer, and becomes a laminate of the porous silica membrane and the substrate.

  Such a porous silica membrane of the present invention can also be used in combination with other layers. In this case, the layer to be combined is appropriately selected depending on the application, and in combination with other layers, in addition to the surface antireflection film, the ultraviolet reflection film, the near infrared reflection film, the infrared reflection film, etc. When applied to a light emitting device, it can also be used as a light extraction film (or brightness enhancement film). Specific examples of other layers to be combined include a high refractive index layer, a scattering layer, a metal layer, a polarizing layer, a heat ray blocking layer, an ultraviolet deterioration preventing layer, a hydrophilic layer, an antifouling layer, an antifogging layer, a moisture proof layer, and an antifogging layer. Examples include a layer, a photocatalyst layer, a corrosion-resistant layer, a fingerprint-resistant layer, an adhesive layer, a hard layer, a gas barrier layer, a conductive layer, an antiglare layer, and a diffusion layer. These layers may be formed on any surface of the substrate, and may be laminated on the porous silica membrane. In addition, these layers may be used individually by 1 type, and may use 2 or more types by arbitrary combinations. Further, as long as the characteristics are not affected, there may be other layers between the above layers.

  Moreover, you may equip the laminated body of the silica porous membrane of this invention and a base material with another optical function layer and a protective film, for example. Other optical functional layers can be appropriately selected depending on the application to be used. Further, these layers may be provided with only one layer, or may be provided with an arbitrary combination of two or more layers.

  Since the laminated body of the porous silica film and the base material of the present invention includes the porous silica film of the present invention having a low refractive index and excellent wear resistance, the antireflection ability and the wear resistance are excellent. The porous silica film of the present invention and the laminate of the porous silica film of the present invention and a substrate are a lens, a display or touch panel such as LCD or OLED, a single crystal silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell. Silicon solar cells such as batteries, CIS solar cells, CIGS solar cells, compound solar cells such as GaAs solar cells, dye-sensitized solar cells, organic thin film solar cells, multi-junction solar cells, HIT solar cells, Optical functional layers such as optical devices such as concentrating solar cells and solar water heaters, building materials such as show windows, and interior and exterior of automobiles such as instrument panels and windshields, antireflection layers and light control layers It can be suitably used for stationery items such as whiteboards.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

  Below, evaluation of the manufactured silica porous membrane was performed by the following method.

<Outermost layer fluorine amount, second outer layer fluorine amount, outermost layer oxygen amount>
XPS elemental analysis was performed under the above-described measurement conditions and analysis methods, respectively, to determine the outermost surface layer fluorine amount, the second outer layer fluorine amount, and the outermost layer oxygen amount.

<Refractive index and film thickness calculation>
The minimum reflectance of the porous silica film formed on the glass substrate was measured with a spectral film thickness meter (FE-3000 manufactured by Otsuka Electronics Co., Ltd.), and the refractive index was calculated using the Fresnel equation. The film thickness was calculated from the calculated refractive index and the minimum reflectance wavelength.

<Abrasion resistance test>
A load of 300 g / cm ² was applied to the surface of the porous silica membrane using bonster # 0000 steel wool, and was reciprocated 10 times. Then, the presence or absence of a flaw was confirmed by the following two methods (a) and (b), and the following evaluation criteria were used.
(A) The presence or absence of scratches was confirmed visually under a fluorescent lamp.
(B) A black tape (manufactured by Yamato Co., Ltd., vinyl tape, black) was attached to the back side of the area where the above test was performed so that no bubbles were mixed, and the presence or absence of scratches was confirmed visually under a fluorescent lamp. By sticking the black tape in this way, even a shallow flaw that cannot be visually confirmed can be easily confirmed.
(Evaluation criteria for scratch resistance)
○: Scratches cannot be confirmed in (b).
Δ: Although scratches can be confirmed in (b), scratches cannot be confirmed in (a).
X: Scratches can be confirmed in (a).

[Example 1]
<Alcoxisilane mixture>
In a 100 ml vial, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), ethanol (EtOH), water (H ₂ O), and hydrochloric acid (HCl) were added at 1.00: 0.372: 0. The mixture was mixed at a molar ratio of 995: 21.0: 0.0218, stirred at 63 ° C. for 30 minutes in a warm water bath, and then allowed to cool at room temperature to obtain an alkoxysilane mixture (A).

<Fluorine-containing silane mixture>
In a 5 ml vial (tridecafluoro-1H, 1H, 2H, 2H-n-octyl) triethoxysilane (FTES), EtOH, H ₂ O, HCl, 1.00: 33.8: 63.3: After mixing at a molar ratio of 0.0658 and stirring at 63 ° C. for 5 minutes in a warm water bath, the mixture was allowed to cool at room temperature to obtain a fluorine-containing silane mixture (B).

<Mixed>
The molar ratio of TEOS, MTES, FTES, EtOH, H ₂ O, HCl to the fluorine-containing silane mixture (B) and the alkoxysilane mixture (A) is 1.00: 0.372: 0.0113: 1.38: 21. .7: 0.0226 was mixed and stirred to obtain a composition (C).

<Solvent dilution>
10 ml of this composition (C) was diluted with 40 ml of EtOH and stirred at room temperature for 30 minutes to obtain a composition (D) (pH 4.5).

<Manufacture of porous silica membrane>
The composition (D) was filtered through a 0.45 μm filter (PVDF), and a 75 mm square glass substrate (center line average roughness = 0.01 μm, maximum height of surface roughness R _max = 0.13 μm). 1.5 ml) was added dropwise to a thickness of 1.0 to 1.5 mm. Then, a thin film was produced by rotating for 2 minutes at 700 rpm with a Mikasa spin coater in an environment with a relative humidity of 26%.
After heating the obtained thin film-formed substrate at a pressure of 0.1 MPa from room temperature to 150 ° C. at 20 ° C./min and from 150 ° C. to 450 ° C. at 7.5 ° C./min using a perfect oven manufactured by ESPEC , Heated at 450 ° C. for 2 minutes, and then allowed to cool to 100 ° C. or lower in an oven.
The obtained porous silica membrane was evaluated as described above, and the results are shown in Table 1.

[Example 2]
In Example 1, after preparing composition (C), 0.0505 g of polyethylene glycol-polypropylene glycol-polyethylene glycol (20:70:20) triblock copolymer (Pluronic® P123) and 0.779 g of EtOH. In the same procedure as in Example 1 except that the spin coater was rotated at a rotation speed of 1000 rpm and the relative humidity during spin coating was 37%. A membrane was produced and evaluated in the same manner, and the results are shown in Table 1.

[Comparative Example 1]
The composition ratio of the alkoxysilane mixture (A) is a molar ratio of TEOS, MTES, EtOH, H ₂ O, HCl = 1.00: 1.12: 1.49: 31.2: 0.0324, and fluorine-containing silane Silica was prepared in the same procedure as in Example 1 except that the mixture (B) was not mixed, the spin coater was rotated at 1000 rpm, and the relative humidity during spin coating was 31%. A porous membrane was produced and evaluated in the same manner, and the results are shown in Table 1.

[Comparative Example 2]
Except that the fluorine-containing silane mixture (B) was not mixed, and the relative humidity at the time of spin coating was 25%, a porous silica membrane was produced in the same procedure as in Example 1, Evaluation was performed in the same manner, and the results are shown in Table 1.

  From Table 1, it can be seen that the porous silica film of the present invention has a low refractive index and excellent wear resistance (abrasion resistance). The porous silica membrane of the present invention is excellent in antifouling property due to the presence of fluorine atoms in the surface layer.

Claims (3)

Meets the following (1) and (2), porous silica film having a refractive index, characterized in that a 1.20 to 1.45.
(1) Carbon atom, oxygen atom, fluorine atom and silicon atom calculated by elemental analysis by X-ray photoelectron spectroscopy (XPS) in the region from the surface of the porous silica membrane to the position of 10 nm in the depth direction The ratio of the number of fluorine atoms to the total number of is 3 to 35 atomic%.
(2) Carbon atoms calculated by elemental analysis by XPS analysis in the depth direction in a region from the position of 10 nm in the depth direction from the surface of the porous silica membrane to a position in the depth direction of 40 nm from the surface The ratio of the number of fluorine atoms to the total number of oxygen atoms, fluorine atoms and silicon atoms is 0.8 atomic% or less. The ratio of the number of oxygen atoms to the total number of carbon atoms, oxygen atoms, fluorine atoms and silicon atoms calculated by elemental analysis by XPS in the region from the surface of the porous silica membrane to the position of 10 nm in the depth direction is porous silica film according to claim 1, characterized in that 30 to 70 atomic%. The porous silica membrane according to claim 1 or 2 , wherein the surface roughness (Ra) is 0.2 to 6 nm.