U.S. patent application number 11/201141 was filed with the patent office on 2006-03-23 for mesostructured thin film, mesoporous thin film, and process for production thereof.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Hirokatsu Miyata.
Application Number | 20060062909 11/201141 |
Document ID | / |
Family ID | 26543171 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060062909 |
Kind Code |
A1 |
Miyata; Hirokatsu |
March 23, 2006 |
Mesostructured thin film, mesoporous thin film, and process for
production thereof
Abstract
An excellent mesostructured thin film, and a process for
producing the mesostructured thin film are provided. In the
process, the mesostructured thin film having an oriented rod-like
pore structure is formed on a surface of a polymer compound
containing a sequence of two or more adjacent methylene groups in
the repeating unit of the molecule.
Inventors: |
Miyata; Hirokatsu;
(Hadano-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
26543171 |
Appl. No.: |
11/201141 |
Filed: |
August 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10670256 |
Sep 26, 2003 |
6984414 |
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11201141 |
Aug 11, 2005 |
|
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09657616 |
Sep 8, 2000 |
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11201141 |
Aug 11, 2005 |
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Current U.S.
Class: |
427/226 ;
427/243 |
Current CPC
Class: |
B01J 20/28033 20130101;
B01J 37/0219 20130101; C03C 17/006 20130101; C03C 17/009 20130101;
C03C 17/007 20130101; B01J 37/0217 20130101; B01J 29/0308 20130101;
C01B 37/02 20130101; C03C 17/34 20130101; B01J 2229/64 20130101;
C03C 2217/213 20130101; B01J 20/28083 20130101; B01J 37/0215
20130101; C03C 2217/425 20130101; B01J 20/28035 20130101 |
Class at
Publication: |
427/226 ;
427/243 |
International
Class: |
B05D 3/02 20060101
B05D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 1999 |
JP |
11-257351 |
Sep 5, 2000 |
JP |
2000-268617 |
Claims
1. A process for producing a mesostructured film having an
uniaxially oriented rod-shaped pore structure, comprising the step
of forming the mesostructured film on a polymer compound containing
a sequence of two or more adjacent methylene groups in a molecular
structure of the repeating unit of the polymer compound, wherein
the surface of the polymer compound is uniaxially oriented.
2. The process for producing a mesostructured film according to
claim 1, wherein the process comprises the step of preparing the
polymer compound.
3. The process for producing a mesostructured film according to
claim 2, wherein the step of preparing the polymer compound is the
step of forming a film of the polymer compound on a base plate.
4. The process for producing a mesostructured film according to
claim 2, wherein the step of preparing the polymer compound is the
step of forming a Langmuir-Blodgett film as the film of the polymer
compound.
5. The process for producing a mesostructured film according to
claim 1, wherein the mesostructured film contains silicon.
6. The process for producing a mesostructured film according to
claim 5, wherein the mesostructured film contains silica.
7. The process for producing a mesostructured film according to
claim 1, wherein the mesostructured film is formed by hydrolyzing a
silicon alkoxide.
8. The process for producing a mesostructured film according to
claim 1, wherein the mesostructured film is formed by hydrolysis
reaction in the presence of a surfactant.
9. The process for producing a mesostructured film according to
claim 8, wherein the surfactant is a quaternary alkylammonium
salt.
10. The process for producing a mesostructured film according to
claim 8, wherein the surfactant contains a polyethylene oxide as
the hydrophilic group.
11. The process for producing a mesostructured film according to
claim 8, further comprising the step of removing the surfactant
after forming the mesostructured film.
12. The process for producing a mesostructured film according to
claim 11, wherein the step of removing the surfactant is the step
of baking the mesostructured film.
13. The process for producing a mesostructured film according to
claim 11, wherein the step of removing the surfactant is the step
of removing the surfactant by solvent-extraction.
14. The process for producing a mesostructured film according to
claim 1, wherein the mesostructured film is formed by hydrolysis
reaction under an acidic condition.
15. The process for producing a mesostructured film according to
claim 1, wherein the mesostructured film is formed by bringing a
solution containing a material for the mesostructured film into
contact with a surface of the polymer compound.
16. The process for producing a mesostructured film according to
claim 1, wherein the number of a sequence of adjacent methylene
groups in the repeating unit of the polymer compound ranges from 2
to 20.
17. The process for producing a mesostructured film according to
claim 1, wherein the sequence of adjacent methylene groups in the
repeating unit of the polymer compound is contained in the main
chain of the polymer compound.
18. The process for producing a mesostructured film according to
claim 1, wherein the sequence of adjacent methylene groups in the
repeating unit of the polymer compound is contained in the side
chain of the polymer compound.
Description
[0001] This application is a division of copending application Ser.
No. 10/670,256, filed Sep. 26, 2003, which, in turn, is a division
of copending application Ser. No. 09/657,616, filed Sep. 8,
2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a mesostructured thin film,
and a process for producing the mesostructured thin film. In
particular, the present invention relates to a mesostructured
silica thin film, a mesoporous silica thin film, a process for
producing the mesostructured silica thin film, and a process for
producing the mesoporous silica thin film.
[0004] 2. Related Background Art
[0005] Porous materials are used in various fields such as
adsorption, and separation. According to IUPAC, the porous
materials are classified into micorporous materials having a pore
diameter of less than 2 nm, mesoporous materials having a pore
diameter of 2 to 50 nm, and macroporous materials having a pore
diameter of more than 50 nm. Known microporous materials include
zeolites such as natural aluminosilicates and synthetic
aluminosilicates, and metal phosphates. These porous materials are
employed for selective adsorption, shape-selective catalytic
reactions, molecular-sized reactors, and so forth by utilizing the
fine pore size.
[0006] Known microporous crystalline materials have pore diameters
of not more than about 1.5 nm. A solid having a larger pore
diameter is demanded for adsorption and reaction of bulkier
compounds not adsorbable by the micropore. As the materials having
the larger pores, there are known silica gels, pillared clays, and
the like. However, these materials have a broad pore size
distribution, and the pore size cannot readily be controlled.
[0007] With such a background, two methods have been disclosed at
about the same time for synthesizing mesoporous silica having
mesopores of a uniform size arranged in a honeycomb shape. The one
method synthesizes a material called MCM-41 by hydrolysis of a
silicon alkoxide in the presence of a surfactant (Nature, vol. 359,
p. 710). The other method synthesizes a material called FSM-16 by
intercalation of an alkylammonium in interlaminar spaces of
kanemite, a kind of layered polysilicate (Journal of Chemical
Society, Chemical Communications, vol. 1993, p. 680). In both
methods, it is considered that surfactant assembly acts as
structure-directing agent of mesostructured silica. These
substances are useful as a catalyst for bulky molecules which
cannot enter the pores of zeolite, and are promising in application
as a functional material such as optical materials and electronic
materials.
[0008] In application of such a mesoporous material having a
regular porous structure as a functional material other than
catalysts, the technique for uniformly holding the material on a
substrate is important. The method for forming a uniform mesoporous
thin film on a substrate includes a spin coating method as shown in
Chemical Communications, vol. 1996, p. 1149, and a dip coating
method as shown in Nature, vol. 389, p. 364, and a deposition
method of forming a film on the surface of a solid material by
deposition as shown in Nature, vol. 379, p. 703.
SUMMARY OF THE INVENTION
[0009] The present invention intends to provide an improved
mesostructured thin film. The present invention intends also to
provide a process for producing the improved mesostructured thin
film.
[0010] The process for producing a mesostructured thin film having
an oriented rod-like pore structure of the present invention
comprises the step of forming the mesostructured thin film on a
surface of a polymer compound containing a sequence of two or more
adjacent methylene groups in a molecular structure of the repeating
unit of the polymer compound.
[0011] The process may comprise the step of preparing the surface
of the polymer compound, preferably forming a polymer compound film
having the polymer compound surface on a base plate.
[0012] The step of forming the polymer compound surface may be the
formation of a Langmuir-Blodgett film.
[0013] The mesostructured thin film is formed on the surface of the
polymer compound which has orientation. The orientation is
preferably uniaxial.
[0014] The mesostructured thin film contains silicon, more
specifically silica. Preferably the mesostructured silica thin film
is formed by hydrolyzing a silicon alkoxide.
[0015] The mesostructured thin film may be formed by hydrolyzing a
material for the mesostructured thin film in the presence of a
surfactant. The surfactant may be a quaternary alkylammonium, or a
surfactant containing a polyethylene oxide as the hydrophilic
group.
[0016] The process may comprise the step of removing the surfactant
after the formation of the mesostructured thin film. By the removal
of the surfactant, the mesostructured thin film can readily be made
porous to produce an excellent mesoporous thin film.
[0017] The removal of the surfactant may be conducted by baking the
mesostructured thin film, or by solvent-extraction of the
surfactant.
[0018] The mesostructured thin film is formed by hydrolyzing a
material for the mesostructured thin film, preferably in an acidic
condition.
[0019] The mesostructured thin film is formed by bringing a
solution containing a material for the mesostructured thin film
into contact with a surface of the polymer compound, specifically
by holding the substrate having a polymer compound surface in a
solution.
[0020] The surface of the polymer compound is preferably subjected
to rubbing treatment before the formation of the mesostructured
thin film. Preferably the rubbing treatment is conducted to have
orientation, especially uniaxial orientation, to the polymer
compound surface. The rubbing treatment is conducted in a direction
perpendicular to the mesochannel of the mesostructured thin film to
be formed.
[0021] The number of a sequence of adjacent methylene groups in the
repeating unit of the polymer compound preferably ranges from 2 to
20.
[0022] The sequence of the adjacent methylene groups in the
repeating unit of the polymer compound may be contained either in
the main chain or the side chain of the polymer compound.
[0023] The mesostructure preferably has a pore structure, and more
preferably the pores in the mesostructure are oriented.
[0024] The above constitutions may be combined.
[0025] In another embodiment of the present invention, a
mesostructured thin film having an oriented rod-like pore structure
is provided which is formed on a polymer compound containing a
sequence of two or more adjacent methylene groups in a molecular
structure of the repeating unit of the polymer compound.
[0026] The surface of the polymer compound may be a surface of a
Langmuir-Blodgett film of the polymer compound.
[0027] The polymer compound is preferably oriented, more preferably
uniaxially oriented.
[0028] The mesostructured thin film contains silicon, specifically
silica. The mesostructured thin film is formed preferably by
hydrolyzing a silicon alkoxide.
[0029] The mesostructured thin film is formed preferably by
hydrolysis reaction in the presence of a surfactant.
[0030] The mesostructured thin film preferably has a hollow
structure.
[0031] The surface of the polymer compound is subjected preferably
to rubbing treatment before the formation of the mesostructured
thin film.
[0032] The rubbing treatment is conducted preferably in a direction
perpendicular to mesochannels of the mesostructured thin film to be
formed.
[0033] The number of a sequence of adjacent methylene groups in the
repeating unit of the polymer compound preferably ranges from 2 to
20.
[0034] The sequence of adjacent methylene groups in the repeating
unit of the polymer compound may be contained either in the main
chain or the side chain of the polymer compound.
[0035] The mesostructure preferably has a pore structure, and more
preferably the pores are oriented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic drawing of a TEM image of an oriented
silica mesocomplex thin film or a mesoporous thin film prepared in
Example 1 of the present invention.
[0037] FIG. 2 is an explanatory drawing of a reactor for forming a
silica mesocomplex thin film of the present invention.
[0038] FIGS. 3A and 3B are respectively an explanatory drawing
showing the method of holding the substrate in a reaction
solution.
[0039] FIG. 4 is a schematic drawing of an LB film forming system
employed in the present invention.
[0040] FIG. 5 is a schematic drawing of a microscopic image of a
thin film formed by the reaction for 24 hours in Example 1 of the
present invention.
[0041] FIG. 6 is a drawing showing dependency of diffraction
intensity at (110) plane on the in-plane rotation angle in the
in-plane X-ray diffraction analysis of the silica mesostructured
thin film formed in Example 1 of the present invention.
[0042] FIG. 7 is a schematic drawing of a microscope image of a
thin film formed by the reaction for 24 hours in Comparative
Example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] Conventional methods for producing a mesoporous thin film
have disadvantages below. The mesostructure of a film formed by
spin coating does not have a directional configuration throughout
the entire film, so that the pore can not be oriented. The
mesostructure of a film formed by deposition on a substrate depends
greatly on the properties of the substrate. For the formation of an
oriented film by deposition, the substrate is limited to those
having order at an atomic level like a cleavage plane of mica or
graphite.
[0044] There has been required a technique for the formation of the
oriented mesoporous thin film on any substrate. A method to satisfy
this requirement is disclosed in Chemistry of Materials, vol. 11,
p. 1609. In this method, a substrate is coated with a thin film of
a polymer compound on the surface thereof and the thin film is
subjected to rubbing treatment.
[0045] The examples below show mesostructured thin films and
mesoporous thin films, formed on a substrate with a simple process,
which are oriented, and highly continuous and uniform, and a
process for producing the thin films.
[0046] The present invention is described below in detail.
[0047] As an embodiment of the present invention, a process for
producing a mesostructured silica thin film, and a silica
mesostructure produced by this process are explained below. In the
process, using a substrate comprising a polymer compound film that
has been subjected to a rubbing treatment formed on the surface
thereof, a mesostructured silica thin film is formed on the
substrate held in a solution by hydrolysis of a silicon alkoxide
under acidic conditions in the presence of a surfactant, wherein
the polymer compound has a repeating unit containing a sequence of
two or more adjacent methylene groups.
[0048] As another embodiment of the present invention, a process
for producing a mesostructured silica thin film and a silica
mesostructure produced by this process are explained below. In the
process, using a substrate comprising a Langmuir-Blodgett film of a
polymer compound formed on the surface thereof, a mesostructured
silica thin film is formed on the substrate held in a solution by
hydrolysis of a silicon alkoxide under acidic conditions in the
presence of a surfactant, wherein the polymer compound has a
repeating unit containing a sequence of two or more adjacent
methylene groups.
[0049] In the aforementioned two processes, a mesostructured silica
thin film excellent in uniformity, continuity, and uniaxial
orientation can be obtained when the polymer compound has a
sequence of adjacent methylene groups the number of which ranges
from 2 to 20 in the repeating unit. The adjacent methylene groups
in the repeating unit of the polymer compound may be contained
either in the main chain or in the side chain of the polymer
compound. The methylene groups contained in the main chain of the
polymer compound tend to improve uniaxial orientation, whereas the
methylene groups in the side chain tend to improve the continuity
of the thin film formed thereon.
[0050] In a second invention of the present application, one
embodiment provides a process for producing a hollow mesoporous
silica thin film by removing the surfactant from the mesostructured
silica thin film formed as described above, and the mesoporous
silica thin film produced by the process. The removal of the
surfactant is usually conducted by baking, or solvent extraction.
However, the method of the removal is not limited thereto, provided
that the surfactant can be removed without destroying the
mesostructure of the fine pores.
[0051] The embodiments of the present invention are explained
below.
[0052] FIG. 2 is an explanatory drawing of an example of the
reactor for forming a silica mesostructured thin film of the
present invention. The material consisting of the reactor 21 is not
specially limited, provided that the material is resistant against
chemicals, especially acids, including polypropylene and
polyfluoroethylene (commercial name: TEFLON). As shown in FIG. 2,
for example, an acid-resistant substrate holder 23 is placed in the
reactor 21 to hold a substrate 25. A lid 22 made of TEFLON
polyfluorethylene or a like material seals the reactor with a seal
24 like an O-ring. In FIG. 2, the substrate 25 is held
horizontally, but is not limited thereto.
[0053] FIGS. 3A and 3B show the method of holding the substrate in
a reaction solution. Generally, as shown in FIG. 3A, the substrate
32 is held in a reaction solution 31. However, the substrate 32 may
be held on the surface of the reaction solution with the face 33
having been treated for orientation brought into contact with the
surface of the reaction solution to form a similar film. The
reactor may be protected by a closed vessel made of a material of
high rigidity against destruction by the pressure during the
reaction.
[0054] For use in FIG. 2 and FIGS. 3A and 3B, the reaction solution
is an aqueous mixture solution of an alkoxide of silicon such as
tetraethoxysilane and a surfactant of which pH is adjusted to lower
than 2 (the isoelectric point of SiO.sub.2) by mixing an acid such
as hydrochloric acid. The surfactant is suitably selected from
cationic surfactants such as quaternary alkylammonium salts, and
nonionic surfactants having a hydrophilic group such as alkylamine
and polyethylene oxide. The length of the molecule of the
surfactant is selected suitably depending on the intended pore
diameter of the mesostructure. An additive such as mesitylene may
be added for increasing the micelle diameter of the surfactant.
[0055] The SiO.sub.2 precipitate is formed at a lower rate under
acidic conditions, especially near the isoelectric point thereof,
although the precipitate is formed instantaneously under basic
conditions on addition of the alkoxide.
[0056] The substrate employed in the present invention has a thin
film of a polymer compound formed thereon and subjected to rubbing
treatment. The base material for the substrate for forming the
polymeric film is not specially limited, the material including
silica glass, ceramics, and resins.
[0057] The rubbing treatment is conducted by rubbing with cloth the
polymer coat having been formed on a substrate by spin coating or a
like coating method. Usually, the rubbing cloth is wound on a
roller, and the rotating roller is pushed against the surface of
the substrate.
[0058] The polymer compound for forming the thin film on the
surface of the substrate has the repeating unit containing a
sequence of two or more adjacent methylene groups. When the
repeating unit has the adjacent methylene groups the number of
which ranges from 2 to 20, the film formed will give a
mesostructured silica thin film of excellent uniaxial orientation.
It is considered that, within this range of the number of the
methylene groups, the orientation of the polymer compound imparted
by the rubbing is not lost by the elevated reaction temperature in
deposition of the mesostructured silica thin film mentioned
later.
[0059] The specific examples of the polymer compound suitable for
the rubbing treatment are polyimides.
[0060] The thickness of the polymer compound thin film is
preferably in the range of from 1 to 20 nm, more preferably from 3
to 10 nm.
[0061] According to the present invention, the uniaxial orientation
of the silica mesostructure can be obtained also by using a
Langmuir-Blodgett film (LB film) of a polymer compound in place of
the rubbing-treated polymer compound thin film. The LB film is
prepared by transferring a monomolecular film spread on a water
surface onto a substrate. A desired number of layers of the film
can be obtained by repeating the layer formation. The LB film in
the present invention includes built-up monomolecular films formed
on a substrate and heat-treated to change the chemical structure
thereof with the built-up structure maintained.
[0062] The LB film may be formed by a conventional method. FIG. 4
shows schematically a conventional LB film formation system. In
FIG. 4, a water tank 41 is filled with pure water 42. The water
tank has a fixed barrier 43 equipped with a surface pressure sensor
not shown in the drawing. A monomolecular layer 46 is formed by
dropping a solution containing the objective substance or the
precursor thereof onto the water surface region between the fixed
barrier 43 and a movable barrier 44. A surface pressure is applied
by moving the movable barrier 44. The movable barrier 44 is
controlled positionally by the surface pressure sensor to apply a
prescribed surface pressure during the film formation on the
substrate. The fresh pure water is incessantly fed by a water
supply apparatus and a water discharge apparatus not shown in the
drawing. A cavity is provided in a portion of the water tank 41,
where a base plate 45 is held. The base plate 45 is driven upward
and downward at a constant speed by a driving mechanism not shown
in the drawing. The film on the water surface is transferred onto
the base plate during the downward movement of the base plate into
water and during the upward movement from the water.
[0063] The LB film employed in the present invention is formed,
layer by layer, on the base plate with such a system by
transferring the monomolecular layer formed on the water surface by
the downward and upward movement of the base plate with application
of a surface pressure. The condition and the properties of the film
are controlled by the surface pressure, the rate of downward and
upward movement of the base plate, and the number of the layers.
The surface pressure during the film formation is selected to be
optimum from the surface area/surface pressure curve, generally
ranging from several mN/m to several ten mN/m. The rate of movement
of the substrate generally ranges from several mm/min to several
hundred mm/min. The LB film is generally formed by the method
described above. However, the LB film in the present invention is
not limited thereto, and may be prepared by utilizing flow of the
subphase water.
[0064] The base plate for the LB film is not specially limited in
its material, but is preferably stable against an acid. The useful
material for the base plate includes silica glass, ceramics, and
resins.
[0065] The polymer compound for the LB film in the present
invention contains a sequence of two or more adjacent methylene
groups in the repeating unit similarly as the compound for the
rubbing-treated polymer compound thin film. The LB film formed from
the compound having 2 to 20 adjacent methylene groups will give a
mesostructured silica thin film of excellent uniaxial orientation.
The polymer compound having a sequence of more than 20 adjacent
methylene groups in the repeating unit has a lower uniaxial
orientation. It is considered that, with a larger number of the
methylene groups, the orientation of the polymer compound of the LB
film is lost at the elevated reaction temperature in deposition of
the mesostructured silica thin film.
[0066] The polymer-compound suitable for formation of the LB film
is exemplified by an alkylamine salt of a polyamic acid, which is
heated to form a polyimide LB film on the base plate.
[0067] The thickness of the LB film ranges preferably from 1 to 20
nm, more preferably from 2 to 10 nm.
[0068] The mesostructured silica can be deposited on a substrate on
the aforementioned conditions. The deposition temperature is not
specially limited, but is selected preferably in the temperature
range from room temperature to about 100.degree. C. The reaction
time ranges from several hours to several months. The shorter the
reaction time, the thinner will be the formed film.
[0069] The film formed in such a manner on a substrate is washed
with pure water and is air-dried to obtain a silica mesocomplex
thin film.
[0070] From this silica mesocomplex thin film, a mesoporous silica
thin film is prepared by removing the template surfactant micelle.
The removal of the surfactant can be conducted by baking or solvent
extraction. For example, the surfactant can be removed completely
by baking the mesostructured thin film at 550.degree. C. in the air
for 10 hours almost without destroying the mesostructure and the
uniaxial orientation thereof. Otherwise, solvent extraction is
employed for formation of a mesoporous thin film on a substrate
material nonresistant to baking, although the surfactant cannot be
removed completely by the solvent extraction.
[0071] The gist of the present invention as described above is as
follows. Firstly, the continuity of the film can be improved by
increasing the hydrophobicity of the polymer compound formed on the
base plate and increasing the deposition density of the mesoporous
silica particles on the rubbing-treated polymer compound thin film
or on the LB film. Secondly, a film of highly uniaxial orientation
can be prepared by strengthening the interaction between the alkyl
groups on the substrate surface and the alkyl groups of the
surfactant molecules.
[0072] The present invention is described below in more detail by
reference to Examples.
EXAMPLE 1
[0073] In this Example, a silica mesocomplex thin film and a
mesoporous silica thin film were formed on a substrate having a
coat of a polymer compound thin film containing a sequence of six
adjacent methylene groups in the repeating unit in the main chain
of the polymer compound and having been subjected to rubbing
treatment.
[0074] A silica glass plate for the substrate was washed with
acetone, isopropyl alcohol, and pure water successively, and was
cleaned with the surface in an ozone generating apparatus. On this
plate, a solution of polyamic acid A in NMP was applied by spin
coating, and the coated matter was baked at 200.degree. C. for one
hour to form a polyimide A having the structure below: ##STR1##
[0075] The thin film was treated with rubbing under the condition
shown in Table 1 to prepare the substrate for the mesocomplex
silica thin film. TABLE-US-00001 TABLE 1 Rubbing Condition of
Polyimide A Cloth material Nylon Roller diameter (mm) 24 Pushing
depth (mm) 0.4 Rotation rate (rpm) 1000 Stage speed (mm/min) 600
Rotation repetition 2
[0076] In 108 mL of pure water, was dissolved 2.82 g of
cetyltrimethylammonium chloride. Thereto, 48.1 mL of 36%
hydrochloric acid was added. The mixture was stirred for two hours
to prepare an acidic surfactant solution. To this solution, 1.78 mL
of tetraethoxysilane (TEOS) was added, and the solution was stirred
for 2 minutes and 30 seconds. This solution was transferred into a
teflon vessel containing the aforementioned substrate as shown in
FIG. 2 to hold the substrate in the solution. This solution
contained totally H.sub.2O, HCl, cetyltrimethylammonium chloride,
and TEOS at a molar ratio of 100:7:0.11:0.10. This vessel was
closed with a lid, and the vessel was placed in a stainless
container. The container was placed in an oven kept at 80.degree.
C. for 24 hours.
[0077] Then the substrate that had been in contact with the
reaction solution for a predetermined time period was taken out
from the vessel, washed sufficiently with pure water, and air-dried
at room temperature.
[0078] The dried substrate after contact with the reaction solution
for 24 hours was examined by an optical microscopy. FIG. 5 shows
schematically the observed morphology. As shown in FIG. 5, on the
substrate having an oriented polyimide film A that has been
subjected to rubbing treatment, an almost continuous film was
formed which has a structure 52 of long and narrow domains oriented
uniaxially perpendicularly to the rubbing direction. On this
polyimide, the film formed under the conditions of this Example had
a few defects 51 in a streak shape parallel to the rubbing
direction as shown in FIG. 5.
[0079] This mesostructured silica thin film was observed by X-ray
diffraction analysis to confirm a major diffraction peak assigned
to the (100) plane of a hexagonal structure having an interplanar
spacing of 3.60 nm. Thereby this thin film was confirmed to have a
hexagonal pore structure. The absence of diffraction peak in the
wide angle region shows that the silica constituting the wall is
amorphous.
[0080] The uniaxial orientation of the mesochannel of the
mesostructured silica thin film was evaluated quantitatively by
in-plane X-ray diffraction analysis. The direction of the
mesochannel signifies the direction of depth of the pores, and the
distribution baking, no diffraction peak was observed in the wide
angle region, which shows that the silica of the wall was kept
amorphous. The sample after the baking was confirmed not to contain
organic components coming from the surfactant by infrared
absorption spectrum.
[0081] The mesoporous silica thin film after the baking was
subjected to in-plane X-ray diffraction analysis to determine the
dependency of the (110) plane diffraction intensity on the in-plane
rotation angle. As the result, a profile similar to that shown in
FIG. 6 was obtained with the half width of about 12.degree.. This
shows that the uniaxial orientation of the mesochannel was kept
unchanged after the baking.
[0082] The thin film before the baking and the thin film after the
baking were cut in the direction parallel to the rubbing direction
by means of focused ion beam (FIB), and the sectional faces were
observed by transmission type electron microscopy. In both of the
films, the presence of pores of the hexagonal structure was
observed, and the orientation of the mesopores were confirmed to be
oriented perpendicularly to the rubbing direction. FIG. 1 shows
schematically the cross section of the silica mesocomplex thin film
taken in the direction perpendicular to the rubbing direction. In
FIG. 1, the numeral 11 denotes a silica glass base plate; 12, a
rubbing-treated oriented film; 13, micelles of a surfactant in a
rod shape, or pores; and 14, silica.
[0083] The baking treatment improves the adhesion of the mesoporous
thin film to the substrate. Thereby, after the baking, the
mesoporous silica film was not exfoliated even by hard rubbing of
the surface with cloth. This is considered to be due to the
formation of partial bonding of the mesoporous silica layer to the
underlaying silica by dehydration condensation of silanol.
EXAMPLE 2
[0084] In this Example, mesoporous silica was prepared by removing
a surfactant from a silica mesocomplex formed on a substrate.
[0085] On a silica glass base plate, polyimide A was formed, and
the polyimide A was subjected to rubbing treatment in the same
manner as in Example 1. Thereon, a mesostructured silica thin film
was formed with the solution of the same composition and in the
same procedure as in Example 1.
[0086] This mesostructured silica thin film was immersed in ethanol
at 70.degree. C. for 24 hours for extraction. With this one
extraction treatment, 90% or more of the surfactant was removed
from the synthesized silica mesostructure. The same extraction
treatment was repeated twice, thereby 95% or more of the surfactant
being removed. The thin film after the extraction was dried to
remove the ethanol to obtain mesoporous silica.
[0087] The solvent extraction for the removal of surfactant
micelles employed in this Example is effective for removing the
surfactant from a silica mesocomplex thin film formed on a
substrate having less resistance to heat treatment in an oxidative
atmosphere, although the solvent extraction is not suitable for
complete removal of the surfactant.
[0088] The formed mesoporous silica thin film was subjected to
in-plane X-ray diffraction analysis as in Example 1 to determine
the uniaxial orientation of the mesochannel in the thin film from
the in-plane rotation dependency of (110) plane diffraction
intensity. The obtained profile had the same half width as that
before the surfactant extraction. This shows that the mesoporous
silica thin film could be obtained also by the solvent extraction
with the uniaxial orientation retained.
EXAMPLE 3
[0089] In this Example, a silica mesocomplex thin film, and a
mesoporous silica thin film were formed on a substrate having a
coat of a polymer compound thin film containing a sequence of 17
adjacent methylene groups in the repeating unit in the side chain
of the polymer compound and having been subjected to rubbing
treatment.
[0090] On a silica glass plate having been preliminarily treated as
in Example 1, a solution of polyamic acid B in NMP was applied by
spin coating, and the coated matter was baked at 180.degree. C. for
one hour to form a polyimide B having the structure below:
##STR2##
[0091] The thin film was subjected to rubbing treatment under the
condition shown in Table 2. TABLE-US-00002 TABLE 2 Rubbing
Condition of Polyimide B Cloth material Nylon Roller diameter (mm)
24 Pushing depth (mm) 0.6 Rotation rate (rpm) 1000 Stage speed
(mm/min) 600 Rotation repetition 2
[0092] This substrate was put into a reaction solution having the
same composition as in Example 1, and the reaction vessel was
placed in an oven kept at 80.degree. C. for 24 hours. Then the
substrate was taken out from the vessel, washed sufficiently with
pure water, and air-dried at room temperature.
[0093] The dried substrate after contact with the reaction solution
for 24 hours was observed by optical microscopy to confirm
orientation of the texture. However, the orientation of the texture
was unclear in comparison with that observed in Example 1. The
orientation direction of the texture in the mesostructured silica
prepared in this Example was parallel to the rubbing direction,
being different from that in Example 1. The mesostructured silica
thin film prepared in this Example was completely continuous, and
does not have defects like that in Example 1.
[0094] This mesostructured silica thin film was observed by X-ray
diffraction analysis to find a major diffraction peak assigned to
the (100) plane of a hexagonal structure having an interplanar
spacing of 3.58 nm. Thereby this thin film was confirmed to have a
hexagonal pore structure. The absence of diffraction peak in the
wide angle region shows that the silica constituting the wall is
amorphous.
[0095] The uniaxial orientation of the mesochannel of the
mesostructured silica thin film was evaluated quantitatively by
in-plane X-ray diffraction analysis as in Example 1. Thereby the
dependency of the (110) plane diffraction intensity on the in-plane
rotation angle was measured. Taking the rubbing direction as the
in-plane rotation angle 0.degree., the profile is of Gaussian type
with the center at 0.degree. with the half width of about
35.degree.. This shows that, in the mesostructured silica thin film
prepared in this Example, the mesochannel is oriented nearly
parallel to the rubbing direction.
[0096] The substrate having the mesostructured silica thin film was
baked under the same condition as in Example 1. The baking caused
no significant change of the surface condition of the substrate.
The X-ray diffraction analysis of the baked thin film gave an
intense diffraction peak at the interplanar spacing of 3.44 nm,
showing the retention of the hexagonal pore structure. After the
baking, no diffraction peak was observed in the wide angle region,
which shows that the silica of the wall was kept amorphous. The
sample after the baking was confirmed not to contain organic
components coming from the surfactant by infrared absorption
spectrum.
[0097] The mesoporous silica thin film given by the baking was
subjected to in-plane X-ray diffraction analysis to determine the
dependency of the (110) plane diffraction intensity on the in-plane
rotation angle. As the result, a profile was of a Gaussian curve
with the half width of about 340. This shows that the
mesostructured silica prepared in this Example retained the
uniaxial orientation of the mesochannel after the baking. The
baking improves the adhesion of the mesostructured thin film to the
substrate in this Example.
COMPARATIVE EXAMPLE 1
[0098] In this Comparative Example, a silica mesocomplex thin film,
and a mesopourous silica thin film were formed on a substrate
having a coat of a polymer compound thin film having no methylene
group in the repeating unit of the polymer compound and having been
subjected to rubbing treatment.
[0099] On a silica glass plate having been treated in the same
manner as in Example 1, a solution of polyamic acid C in NMP was
applied by spin coating, and the coated matter was baked at
200.degree. C. for one hour to form a polyimide C having the
structure below: ##STR3##
[0100] The thin film was subjected to rubbing treatment under the
condition shown in Table 3. TABLE-US-00003 TABLE 3 Rubbing
Condition of Polyimide C Cloth material Nylon Roller diameter (mm)
24 Pushing depth (mm) 0.4 Rotation rate (rpm) 1000 Stage speed
(mm/min) 600 Rotation repetition 2
[0101] This substrate was put into a reaction solution of the same
composition as in Example 1, and the reaction vessel was placed in
an oven kept at 80.degree. C. for 24 hours. Then the substrate was
taken out from the vessel, washed sufficiently with pure water, and
air-dried at room temperature.
[0102] The mesostructured silica thin film prepared in this
Comparative Example was observed by optical microscopy. Thereby,
long and narrow particles of mesostructured silica were uniaxially
oriented in the rubbing direction. The particles are in most
portions in a scattered state, although distributed continuously in
part to form films. FIG. 7 shows schematically the optical
microscope image of the mesostructured silica formed on the
substrate in this Comparative Example. In FIG. 7, the breadth w of
the individual particle was in the range from about 2 .mu.m to
about 3 .mu.m. The X-ray diffraction pattern of this sample had a
diffraction peak assigned to the (100) plane of the hexagonal
structure at the position corresponding to the interplanar spacing
of 3.60 nm, showing the formation of the same structure as the
mesostructure obtained in Example 1 on the substrate.
[0103] The mesochannel was found to be curved at the end portions
of the individual particles shown in FIG. 7, so that the uniaxial
orientation of the mesostructured silica prepared in the
Comparative Example is inferior as a whole.
EXAMPLE 4
[0104] In this Example, a silica mesocomplex thin film, and a
mesoporous silica thin film were formed on a substrate coated with
an LB film formed from the polyimide A employed in Example 1.
[0105] Polyamic acid A and N,N-dimethylhexadecylamine were mixed at
a molar ratio of 1:2 to form a salt of N,N-dimethylhexadecylamine
salt of the polyamic acid A. This salt was dissolved in
N,N-dimethylacetamide to form a 0.5 mM solution. This solution was
dropped onto a surface of water kept at 20.degree. C. in an LB film
forming apparatus. The monomolecular film formed on the water
surface was transferred onto a base plate with application of a
constant surface pressure of 30 mN/m at a base plate dipping speed
of 5.4 mm/min.
[0106] The employed base plate was a silica glass plate which had
been washed with acetone, isopropyl alcohol, and pure water
successively and subjected to surface cleaning in an ozone
generator for hydrophobicity. An LB film of 30 layers of the
alkylamine salt of the polyamic acid was formed on the base plate.
The LB film was baked in a nitrogen gas flow at 300.degree. C. for
30 minutes to form an LB film of polyimide A. Imidation by
cyclodehydration of polyamic acid and elimination of alkylamine
were checked by infrared spectroscopy.
[0107] This obtained substrate was put into a reaction solution
having the same composition as in Example 1, and the reaction
vessel was placed in an oven kept at 80.degree. C. for 24 hours.
Then the substrate was taken out from the vessel, washed
sufficiently with pure water, and air-dried at room
temperature.
[0108] The mesostructured silica thin film formed in this Example
was observed by optical microscopy. Thereby, it was found that a
continuous film was formed which had the same texture as that of
the thin film prepared in Example 1. The orientation of the texture
was in a direction perpendicular to the base plate pull-up
direction. The formed mesostructured silica thin film has a few
defects in this case also. However, the defects were less than that
in the film prepared in Example 1. The method of this Example could
give a mesostructure silica thin film having high continuity in
comparison with the method in which a substrate is prepared by
forming a film by spin coating on a base plate and the formed film
is rubbed, although the formation of an LB film requires much
labor.
[0109] This mesostructured silica thin film was observed by X-ray
diffraction analysis to find a major diffraction peak assigned to
the (100) plane of a hexagonal structure having an interplanar
spacing of 3.58 nm. Thereby this thin film was confirmed to have a
hexagonal pore structure. The absence of diffraction peak in the
wide angle region shows that the silica constituting the wall is
amorphous.
[0110] The uniaxial orientation of the mesochannel of the
mesostructured silica thin film was evaluated quantitatively by
in-plane X-ray diffraction analysis as in other Examples. Thereby
the dependency of the (110) plane diffraction intensity on the
in-plane rotation angle was measured. Taking the base plate pull-up
direction in the LB film formation as the in-plane rotation angle
0.degree., the profile is of Gaussian type with the center at
90.degree. with the half width of about 12.degree.. This shows
that, in the mesostructured silica thin film formed on the LB film
of polyimide A in this Example, the mesochannel is oriented
perpendicularly to the direction of the movement of the base
plate.
[0111] The substrate having the mesostructured silica thin film was
baked under the same conditions as in Example 1 to remove the
surfactant. The baking caused no significant change in the
morphology of the film. The X-ray diffraction analysis of the baked
thin film gave an intense diffraction peak at the interplanar
spacing of 3.42 nm, showing the retention of the hexagonal pore
structure. After the baking, no diffraction peak was observed in
the wide angle region, which shows that the silica of the wall was
kept amorphous. The sample after the baking was confirmed not to
contain organic components coming from the surfactant by infrared
absorption spectrum.
[0112] The mesoporous silica thin film given by the baking was
subjected to in-plane X-ray diffraction analysis to determine the
dependency of the (110) plane diffraction intensity on the in-plane
rotation angle. As the result, a profile had a half width of about
12.degree.. This shows that the mesostructured silica prepared in
this Example retained the uniaxial orientation of the mesochannel
after the baking.
EXAMPLE 5
[0113] In this Example, a mesostructured silica thin film and a
mesoporous silica thin film having pores of uniaxially oriented
two-dimensional hexagonal structure were formed on a substrate
coated with oriented polyimide A film and subjected to rubbing
treatment as in Example 1, using a surfactant having polyethylene
oxide group as the hydrophilic group.
[0114] On a silica glass plate, a thin film of polyimide A was
formed with the same polyamic acid and in the same manner as in
Example 1. This thin film was subjected to rubbing treatment in the
same manner as in Example 1 under the conditions shown in Table 1
to obtain the substrate for mesostructured silica formation.
[0115] 5.52 g of polyoxyethylene dodecyl ether
(C.sub.12H.sub.25(CH.sub.2CH.sub.2O).sub.10OH, C.sub.12EO.sub.10)
was dissolved in 129 mL of pure water. Thereto, 20.6 mL of
concentrated hydrochloric acid (36%) was added, and further to the
solution, 2.20 mL of tetraethoxysilane (TEOS) was added. The
mixture was stirred for 3 minutes. The total molar ratio of the
constituents in the solution of TEOS, H.sub.2O, HCl, and
C.sub.12EO.sub.10 was 0.1:100:3:0.11.
[0116] The above substrate having the rubbing-treated polyimide A
film was held in the above reaction solution with the film-coated
face directed downward. The vessel containing the reaction solution
was closed tightly. The reaction was allowed to proceed at
80.degree. C. for three days. During the reaction, the surface was
covered via a spacer to obtain an excellent uniaxially oriented
mesostructured silica thin film.
[0117] After the contact of the substrate with the reaction
solution for the prescribed time, the substrate was taken out from
the reaction vessel, washed with pure water sufficiently, and dried
in the air at room temperature. A continuous film of mesostructured
silica was confirmed to be formed on the substrate.
[0118] This film was examined by X-ray diffraction analysis to find
a major diffraction peak corresponding to interplanar spacing of
4.30 nm assigned to the (100) plane of mesostructured silica. This
thin film had a pore structure in which rod-like pores are packed
hexagonally.
[0119] The uniaxial orientation of the mesochannel of the
mesostructured silica thin film was also evaluated quantitatively
by in-plane X-ray diffraction analysis. From the dependency of the
(110) plane diffraction intensity on the in-plane rotation angle,
in the mesostructured silica thin film prepared in this Example,
the mesochannel is oriented perpendicularly to the rubbing
direction with the orientation direction distribution with the half
width of about 20.degree..
[0120] As described above, a uniaxially oriented mesostructured
silica thin film was confirmed to be formed on the substrate even
by use of the nonionic surfactant having polyethylene oxide as the
hydrophilic group.
[0121] The mesostructured silica thin film was immersed in ethanol
and the ethanol was refluxed at 70.degree. C. for 24 hours to
remove the surfactant from the pores in the mesostructured silica.
This operation was repeated twice. Thereby, 96% or more of the
surfactant could be removed from the pores. The thin film after the
removal of the surfactant was analyzed by in-plane X-ray
diffraction to determine the distribution of pore direction. A
mesoporous silica thin film was confirmed to be formed with the
complete retention of the uniaxial orientation with the half width
of about 20.degree..
[0122] The use of a nonionic surfactant having polyethylene oxide
as the hydrophilic group makes it possible to control the pore
diameter in a wide range in comparison with the use of an
alkylammonium type of cationic surfactant.
[0123] As shown in the above Examples, a mesocomplex thin film, and
a mesoporous thin film can be formed with high continuity and high
uniaxial orientation on the substrate which has a thin film of a
polymer compound having a sequence of two or more adjacent
methylene groups in the repeating unit and has been subjected to
rubbing treatment, or on the substrate which has an LB film of a
polymer compound having a sequence of two or more adjacent
methylene groups in the repeating unit.
[0124] According to the present invention, an excellent
mesostructured thin film can be realized and produced.
* * * * *