U.S. patent application number 10/059374 was filed with the patent office on 2002-05-30 for article having uneven surface, production process for the article, and composition for the process.
Invention is credited to Nakama, Kenichi, Shinmo, Katsuhide.
Application Number | 20020064666 10/059374 |
Document ID | / |
Family ID | 12140610 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020064666 |
Kind Code |
A1 |
Shinmo, Katsuhide ; et
al. |
May 30, 2002 |
Article having uneven surface, production process for the article,
and composition for the process
Abstract
A process for producing an article having a finely uneven
surface coated with a film, which has high heat resistance and
which neither cracks nor peels off from a substrate, by forming a
film of a sol material between a substrate and a mold in such a
manner that the film is in close contact with them and applying
heat to form a gelled film, which has a surface configuration that
is the inversion of the surface configuration of the mold, on the
surface of the substrate, wherein the sol material contains (A)
R.sub.2SiX.sub.2 (R is an alkyl group and X is an alkoxyl group or
halogen atom) and (B) R'SiX'.sub.3 (R' is an aryl group or
substituted aryl group and X' is an alkoxyl group or halogen
atom).
Inventors: |
Shinmo, Katsuhide;
(Osaka-shi, JP) ; Nakama, Kenichi; (Osaka-shi,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
12140610 |
Appl. No.: |
10/059374 |
Filed: |
January 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10059374 |
Jan 31, 2002 |
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09411224 |
Oct 4, 1999 |
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09411224 |
Oct 4, 1999 |
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PCT/JP99/00460 |
Feb 3, 1999 |
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Current U.S.
Class: |
428/447 |
Current CPC
Class: |
B29C 33/424 20130101;
B29K 2083/005 20130101; B23K 2103/50 20180801; B23K 2103/52
20180801; C03C 17/30 20130101; B29C 39/148 20130101; C03C 2218/335
20130101; C03C 2217/77 20130101; B29C 39/18 20130101; C09D 183/04
20130101; B23K 26/40 20130101; Y10T 428/31663 20150401; B23K 26/364
20151001; B29D 11/00365 20130101; B23K 2103/34 20180801; B29C 41/12
20130101; B23K 2103/42 20180801; B29L 2011/0016 20130101; B29D
11/00278 20130101; B29C 41/20 20130101 |
Class at
Publication: |
428/447 |
International
Class: |
B32B 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 1998 |
JP |
10-024526 |
Claims
What is claimed:
1. An article having an uneven surface produced by the process
comprising forming a film of a sol material between the substrate
of the article and a mold in such a manner that the film is in
close contact with these and heating the film to form a gelled
film, which has a surface configuration that is the inversion of
the surface configuration of the mold, on the surface of the
substrate of the article, wherein the sol material contains (A) a
silane compound represented by the following formula (1):
R.sub.2SiX.sub.2 (1) wherein R is an alkyl group and X is an
alkoxyl group or a halogen atom, and (B) a silane compound
represented by the following formula (2): R'SiX'.sub.3 (2) wherein
R' is a substituted or unsubstituted aryl group and X' is an
alkoxyl group or a halogen atom, wherein an organopolysiloxane film
having an uneven surface is formed to a thickness of 1 .mu.m to 1
mm on the surface of the substrate of the article and the film
contains 5 to 25 wt % of an alkyl group and 5 to 40 wt % of an aryl
group.
Description
TECHNICAL FIELD
[0001] The present invention relates to articles having a finely
uneven surface (small dents and small projections) and,
particularly, to micro optical elements and information recording
medium substrates as well as a production process and composition
for the same.
BACKGROUND ART
[0002] Optical parts such as CD-ROMs, other information recording
media, plate microlenses (an array of a large number of microlenses
arranged in parallel on a plate), Fresnel lenses and diffraction
grating elements must have fine irregularities (small dents and
small projections) on the surface. The fine irregularities on the
surface function as a pit or tracking guide in an information
recording medium or as a microlens or diffraction grating to focus
or diffuse light in an optical part.
[0003] To form irregularities on the surface, there is known a
process which comprises spreading an ultraviolet curable resin over
a substrate uniformly and exposing the resin to ultraviolet
radiation with the resin pressed with a mold having irregularities
(JP-A 63-49702).
[0004] JP-A 62-102445 discloses a process for producing an article
having irregularities on the surface by means of a so-called
"sol-gel process" which comprises coating a solution containing
silicon alkoxide on a glass substrate and heating the substrate
with the substrate pressed with a mold having irregularities to
form irregularities. JP-A 6-242303 discloses a process for forming
a plurality of layers on a substrate when a film having a thickness
of several micrometers or more is formed by means of the sol-gel
process. In this case, a solution or sol containing the
constituents of each layer is poured over a completely solidified
layer, which is formed by coating the solution or sol on the
existing layer and heating the layer with the layer pressed with a
mold, to form an upper layer.
[0005] However, the above prior art technologies have the following
problems. Firstly, the ultraviolet curable resin has such low heat
resistance that it decomposes or yellows at temperatures of
250.degree. C. or above. Therefore, a substrate having
irregularities which is made of an ultraviolet curable resin cannot
be subjected to a heat treatment such as soldering and is difficult
to be mounted on a device.
[0006] In contrast to this, irregularities made of silicon alkoxide
by the sol-gel process has high heat resistance and can be
soldered. However, the sol-gel process has such a problem that a
thick film cannot be formed. In fact, when a silicon alkoxide layer
of several tens of micrometers is formed by the sol-gel process,
fine cracks emerge on the surface of the layer. This is because
large stress is produced on the surface due to a difference in the
progress of a polycondensation reaction between the surface and the
interior of this layer when a silicon alkoxide solution is gelled
and solidified. Further, this stress sometimes causes the layer to
peel off from the substrate.
[0007] An organopolysiloxane layer having irregularities and a
thickness of several tens of micrometers can be formed by molding a
plurality of organopolysiloxane layers sequentially. However, the
production process is long, thereby boosting costs. In addition,
since a solution for the next layer is poured after an under layer
is completely cured, undesirable air easily enters in a space
between the mold and the solution or sol, thereby reducing the
dimensional accuracy of the irregularities.
DISCLOSURE OF THE INVENTION
[0008] The present invention has been made in view of the above
problems of the prior art. It is an object of the present invention
to provide a process for producing an article which has a finely
uneven surface and high dimensional accuracy and whose surface film
has high heat resistance, does not crack even if it is a
single-layer film having a thickness of several tens to several
thousands of micrometers and does not peel off from a
substrate.
[0009] It is another object of the present invention to provide a
composition for forming the above film.
[0010] It is still another object of the present invention to
provide an article having an uneven surface which is produced by
the process of the present invention.
[0011] Other objects and advantages of the present invention will
become apparent from the following description.
[0012] According to the present invention, firstly, the above
objects and advantages of the present invention are attained by a
process for producing an article having an uneven surface,
comprising forming a film of a sol material between the substrate
of the article and a mold in such a manner that the film is in
close contact with these and heating the film to form a gelled
film, which has a surface configuration that is the inversion of
the surface configuration of the mold, on the surface of the
substrate of the article, wherein
[0013] the sol material contains (A) a silane compound represented
by the following formula (1):
R.sub.2SiX.sub.2 (1)
[0014] wherein R is an alkyl group and X is an alkoxyl group or a
halogen atom, and
[0015] (B) a silane compound represented by the following formula
(2):
R'SiX'.sub.3 (2)
[0016] wherein R' is a substituted or unsubstituted aryl group and
X' is an alkoxyl group or a halogen atom.
[0017] According to the present invention, secondly, the above
objects and advantages of the present invention are attained by an
article having an uneven surface which is produced by the process
of the present invention, wherein an organopolysiloxane film having
irregularities is formed to a thickness of 1 .mu.m to 1 mm on the
surface of the substrate of the article and contains 5 to 25 wt %
of an alkyl group and 5 to 40 wt % of an aryl group.
[0018] According to the present invention, finally, the above
objects and advantages of the present invention are attained by a
composition for forming a film for producing an article having an
uneven surface, which contains:
[0019] (A) a dialkyldialkoxysilane in an amount of 1 mol,
[0020] (B) a trialkoxysilane having an aryl group or substituted
aryl group in an amount of 0.2 to 4 mol,
[0021] (C) an alcohol in an amount 0.3 to 3 times the total number
of moles of the components (A) and (B),
[0022] (D) an acid catalyst in an amount 3 to 20 times the total
number of moles of the components (A) and (B), and
[0023] (E) water in an amount 2 to 20 times the total number of
moles of the components (A) and (B).
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a sectional view of a mold according to one
embodiment of the present invention;
[0025] FIG. 2 is a sectional view showing that a sol material is
coated on the mold of FIG. 1;
[0026] FIG. 3 is a sectional view showing that a substrate is
brought into contact with the sol material of FIG. 2;
[0027] FIG. 4 is a sectional view of a substrate having fine
irregularities after it is removed from the mold shown in FIG.
3;
[0028] FIG. 5 is a sectional view showing that a sol material is
coated on a substrate according to another embodiment of the
present invention;
[0029] FIG. 6 is a sectional view showing that a mold is pressed
against the sol material of FIG. 5; and
[0030] FIG. 7 is a sectional view showing a substrate having fine
irregularities after it is removed from the mold shown in FIG.
6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] In the present invention, a sol material contains both a
silane compound represented by the above formula (1) and a silane
compound represented by the above formula (2).
[0032] In the above formula (1), R is an alkyl group and X is an
alkoxyl group or halogen atom.
[0033] The alkyl group represented by R may be either
straight-chain or branched-chain and is preferably an alkyl group
having 1 to 3 carbon atoms.
[0034] The alkoxyl group represented by X may be either
straight-chain or branched-chain and is preferably an alkoxyl group
having 1 to 4 carbon atoms. The halogen atom represented by X is,
for example, fluorine, chlorine or bromine.
[0035] Preferred examples of the silane compound represented by the
formula (1) include dialkyldialkoxysilanes such as
dimethyldiethoxysilane, dimethyldimethoxysilane,
diethyldiethoxysilane and diethyldimethoxysilane; and
dialkyldichlorosilanes such as dimethyldichlorosilane and
diethyldichlorosilane.
[0036] In the above formula (2), R' is a substituted or
unsubstituted aryl group and X' is an alkoxyl group or halogen
atom. The unsubstituted aryl group is preferably an aryl group
having 6 to 13 carbon atoms such as phenyl, biphenyl or naphthyl.
The substituent of the aryl group is preferably an alkyl group
having 1 to 3 carbon atoms or halogen atom. The aryl group
substituted by the above substituent is preferably a tolyl group,
xylyl group, chlorophenyl group or the like.
[0037] Illustrative examples of the alkoxyl group and the halogen
atom represented by X' are the same as those listed for X in the
formula (1).
[0038] Illustrative examples of the compound represented by the
above formula (2) include trialkoxysilanes having a phenyl group or
substituted phenyl group such as phenyltriethoxysilane,
phenyltrimethoxysilane, triethoxysilane having a substituted phenyl
group obtained by substituting part of the hydrogens of a phenyl
group by a halogen atom such as a chlorine atom, and
trimethoxysilane having the same substituted phenyl group as
described above; phenyltrichlorosilane, and trichlorosilane having
a substituted phenyl group obtained by substituting part of the
hydrogens of a phenyl group by a halogen atom such as a chlorine
atom; tolyltrimethoxysilane and tolyltriethoxysilane;
tolyltrichlorosilane; xylyltrimethoxysilane and
xylyltriethoxysilane; xylyltrichlorosialane;
biphenyltrimethoxysilane and biphenyltriethoxysilane;
biphenyltrichlorosilane; and the like.
[0039] An alkoxysilane such as methoxysilane or ethoxysilane is
preferably used as the component (A) represented by the above
formula (1) and the component (B) represented by the above formula
(2) because an alcohol generated by a hydrolytic reaction easily
volatilizes. A preferred combination of the component (A) and the
component (B) as the raw materials of the sol material is
dimethyldialkoxysilane and phenyltrialkoxysilane.
[0040] In the present invention, the components (A) and (B) are
used as the raw materials of the sol material. The alkyl group and
the aryl group remain in large quantities in the film that is
eventually obtained by coating the sol material on the substrate of
the article. The alkyl group and the aryl group serve to reduce the
fragility of the film and to provide elasticity to the film,
thereby making it possible to suppress thermal stress generated in
the interior of the film and to prevent the film from cracking and
peeling off from the substrate of the article.
[0041] A case where a dialkyldialkoxysilane is used as the
component (A) and a trialkoxysilane having an aryl group or
substituted aryl group is used as the component (B) will be
described hereunder.
[0042] As for the film structure of the present invention, the
terminal of the straight-chain dialkoxysilane extending like a
fiber is retained by the trialkoxysilane three-dimensionally
through the mixing of the dialkoxysilane and the trialkoxysilane,
whereby allowance is generated in the three-dimensional skeleton,
which provides elasticity to the film and reduces the fragility of
the film, thereby making it possible to form a thick film.
[0043] The significance of the aryl group or substituted aryl group
contained in the film of the present invention containing is that
these groups are bulky enough to provide elasticity to the skeleton
structure of an oxide contained in the film while suppressing the
fragility of the film and that they have stability at high
temperatures because of their conjugated system, as compared with
other organic groups. For example, a film containing
cyclohexyltrialkoxysilane, which is obtained by substituting an
aryl group or substituted aryl group by a cyclohexyl group having
no conjugated system, and dialkyldialkoxysilane discolors at 200 to
300.degree. C. and cracks.
[0044] It is preferable that the sol material contain the component
(A) and the component (B) in a molar ratio of 1:0.2 to 1:4 as raw
materials. When the amount of the component (B) is smaller than 0.2
mol, the film is hardly cured, most of the components volatilize
during final heating, and the film is hardly formed in the end.
When the amount of the component (B) is larger than 4 mol, the
flexibility of a film is impaired, and a film of 20 .mu.m or more
in thickness readily cracks during final heating or cooling after
the final heating. It is more preferable that the film contain the
component (A) and the component (B) in a molar ratio of 1:0.4 to
1:1.
[0045] When alkoxysilanes having an organic group other than the
above, for example, a mixture of dimethyldimethoxysilane and
vinyltriethoxysilane is used as the raw materials of the sol
material, the obtained film has such low heat resistance that it
thermally decomposes at 300.degree. C. or less. When only
tetraalkoxysilanes are used as the raw materials, when only
alkyltrialkoxysilanes are used as the raw materials and when a
mixture of a dialkyldialkoxysilane and an alkyltrialkoxysilane is
used as the raw materials, film stress increases after final
heating and a film of 20 .mu.m or more in thickness cracks.
[0046] As another raw material of the sol material in the present
invention, an alcohol solvent is added to a mixture solution of the
component (A) and the component (B). The alcohol to be added is
preferably a lower alcohol having 1 to 4 carbon atoms, particularly
preferably methanol or ethanol having a low boiling point. The
reason for this is that the alcohol can be removed from the
solution swiftly by a heat treatment at a relatively low
temperature after hydrolysis. The amount of the alcohol is
preferably 0.3 to 3 times, more preferably 0.5 to 1.5 times the
total number of moles of the components (A) and (B).
[0047] A catalyst for hydrolyzing alkoxysilanes is added to this
solution. The catalyst is preferably an acid catalyst. An aqueous
solution of at least one acid catalyst selected from formic acid,
hydrochloric acid, nitric acid and sulfuric acid is preferably used
as the acid catalyst. The amount of the acid catalyst is preferably
3 to 20 times, more preferably 5 to 15 times the total number of
moles of the components (A) and (B). Water is preferably added in
an amount larger than the stoichiometric amount required for
hydrolysis. When the amount of water is smaller than the
stoichiometric amount, unreacted alkoxysilanes are liable to
volatilize during a heat treatment for gelation. The amount of
water including the water of the aqueous catalyst solution is
generally 1.1 to 3 times the required stoichiometric amount, or
preferably 2 to 20 times, more preferably 4 to 10 times the total
number of moles of the components (A) and (B).
[0048] In the present invention, the sol material is prepared by
hydrolyzing both alkoxysilanes while a solution consisting of the
component (A), the component (B), the alcohol solvent, water and
the catalyst is stirred at room temperature for 90 to 120 minutes
and is maintained.
[0049] Thereafter, it is preferred to proceed with a
dehydration/polycondensation reaction by maintaining the resulting
solution at room temperature to 140.degree. C., preferably 70 to
100.degree. C., for 6 to 30 hours and to vaporize or dissipate the
solvent and water contained in the solution and an alcohol, which
is the dehydration/polycondensation reaction product. As a result,
the mass and volume of the solution are reduced to 25 to 35% by
weight and volume of the original mass and volume of the solution
at the time of preparation. Thus, the cracking of the formed film
is prevented by suppressing the shrinkage of the film as much as
possible, and a cured film can be formed without forming air
bubbles in the film during final heating. When this
dehydration/polycondensation reaction proceeds too far, the
viscosity of the solution becomes too high, thereby making it
difficult to coat the solution on the mold or on the surface of the
substrate. On the contrary, when the dehydration/polycondensation
reaction proceeds insufficiently, it is impossible to prevent the
formation of air bubbles in the film during final heating. It is
preferred to control the progress of the
dehydration/polycondensation reaction by selecting the temperature
and the retention time to ensure that the viscosity of the solution
becomes about 10.sup.3 poise or less.
[0050] In the present invention, a tetraalkoxysilane, an
alkyltrialkoxysilane, an alkyl hydrogen dialkoxysilane, a silane
halide obtained by substituting part or all of the alkoxyl groups
of a tetraalkoxysilane by a halogen such as chlorine, a silane
halide obtained by substituting part or all of the alkoxyl groups
of the alkyltrialkoxysilane by a halogen such as chlorine, or a
silane halide obtained by substituting part or all of the alkoxyl
groups of the alkyl hydrogen dialkoxysilane by a halogen such as
chlorine is newly added to the solution which has undergone the
above dehydration/polycondensation reaction in an amount of 10% or
less, preferably 0.001 to 10%, more preferably 0.001 to 0.1%, based
on the total number of moles of the components (A) and (B). The
resulting mixture is maintained at room temperature to 140.degree.
C., preferably 70 to 100.degree. C., for 6 to 30 hours. Since the
terminal of an oligomer having elasticity can be activated by the
addition of the above component and the above solution becomes a
solution which is readily gelled, the heating temperature for
curing a film having an uneven surface molded by a mold can be
reduced. As a result, the heating temperature for curing the film
having an uneven surface molded by a mold can be reduced and the
heating time can be shortened, so that work efficiency can be
improved, the life of the mold can be extended, and dimensional
differences in the plane direction of the substrate between the
uneven surface of the mold and the uneven surface of the final film
formed on the substrate become extremely small. When the addition
amount of the above alkoxysilane or the like is larger than 10%,
the obtained film easily cracks.
[0051] The alkyl hydrogen dialkoxysilane is preferably a compound
represented by the following formula:
R.sup.1HSi(OR.sup.2).sub.2
[0052] wherein R.sup.1 is an alkyl group, preferably a methyl group
or ethyl group and R.sup.2 is an alkyl group, preferably an alkyl
group having 1 to 4 carbon atoms.
[0053] Before the solution in which both alkoxysilanes have been
hydrolyzed under agitation is subjected to the above
dehydration/polycondensation reaction, the above tetraalkoxysilane,
alkyltrialkoxysilane, alkylhydrogen dialkoxysilane or the like is
preferably added likewise in an amount of 10% or less, preferably
0.001 to 10-based on the total number of moles of the components
(A) and (B). Thereby, molding becomes easy and dimensional
differences in the plane direction of the substrate between the
uneven surface of the mold and the uneven surface of the film
formed on the substrate become extremely small. When the hydrolysis
and the dehydration/polycondensation reaction are carried out in
succession at room temperature, the alkoxysilane may be added at
any time after the agitation of hydrolysis ends and the
polymerization proceeds to some extent and before an oligomer is
formed.
[0054] Formamide can be added as a polymerization catalyst to the
solution which has undergone the above dehydration/polycondensation
reaction. Since formamide has a high boiling point of 210.degree.
C., it works effectively without being vaporized when heated at
high temperatures to cure a film. Further, since it also serves as
adehydration catalyst, it can improve reactivity when the solution
is cured, work effectively at the time of final heating and make it
possible to form a film devoid of air bubbles by suppressing the
formation of air bubbles caused by dehydration. The amount of
formamide is preferably 1 to 10% based on the total number of moles
of the components (A) and (B).
[0055] An article having an uneven surface is produced by forming a
film of the sol material obtained as described above between the
substrate of the article and the mold in such a manner that the
film is in close contact with them, heating the film and forming a
gelled film, which has a surface configuration that is the
inversion of the surface configuration of the mold, on the surface
of the substrate of the article. There are two typical processes
for molding the film having a finely uneven surface.
[0056] The first process (to be referred to as "mold pouring
process" hereinafter) comprises pouring the solution of the sol
material over the mold, applying heat, bringing the substrate of
the article into contact with the molded film, further applying
heat to bond the molded film to the substrate of the article,
releasing the bonded product from the mold and final-heating the
product. That is, a mold having a finely uneven surface is held
horizontally, and the liquid sol material having a viscosity of
10.sup.3 poise or less is poured over the mold so that every recess
of the mold is filled with the sol material. Alternatively, the
mold may be immersed in a bath of the sol material or coated with
the liquid sol material by a brush. In this state, the sol material
on the mold is maintained at 140 to 180.degree. C. for 20 to 120
minutes to proceed with a dehydration/polycondensation reaction
until the viscosity thereof preferably becomes 10.sup.4 to 10.sup.8
poise. Thereafter, the substrate of the article is placed upon the
mold in such a manner that it is in close contact with the mold,
and the sol material is brought into contact with the surface of
the substrate in such a manner that no space is formed
therebetween, maintained at 140 to 180.degree. C. for 10 to 120
minutes and gelled by nearly completing the
dehydration/polycondensation reaction of the sol material.
Thereafter, the mold is removed from the substrate to form a
polysiloxane film, which is a soft gelled film having an uneven
surface that is the inversion of the uneven surface of the mold, on
the surface of the substrate in such a manner that the polysiloxane
film is bonded to the substrate. When the mold is removed too
early, the polysiloxane film is so soft that the uneven surface of
the film is deformed by its own weight. Therefore, the above
application of heat is carried out until this deformation does not
occur. By final-heating the polysiloxane film at 180 to 350.degree.
C. for 10 to 150 minutes, the residual silanol group of the
polysiloxane film is polycondensed and water generated by the
polycondensation is vaporized, whereby a fine film whose volume is
slightly reduced in a thickness direction is obtained. Thus, an
article having an uneven surface is obtained that is coated with a
film having a surface configuration which is the inversion of the
surface configuration of the mold.
[0057] The second molding process (to be referred to as "substrate
pouring process" hereinafter) comprises pouring the sol material
solution over the surface of the substrate directly, applying heat,
pressing the mold against the surface of the substrate of the
article when the liquid film acquires plasticity (or when the
viscosity of the solution becomes about 10.sup.4 to 10.sup.8
poise), heating the substrate in this state, removing the mold
after transfer-molding and final-heating the substrate. That is,
the surface to be coated of the substrate of the article is held
horizontally, the liquid sol material having a viscosity of about
10.sup.3 poise or less is poured and spread over the substrate of
the article in the form of a film having a predetermined thickness.
In this state, the poured sol material is maintained, for example,
at 140 to 180.degree. C. for 20 to 120 minutes to proceed with a
dehydration/polycondensation reaction until the viscosity of the
sol material becomes 10.sup.4 to 10.sup.8 poise. Then, the mold
having a finely uneven surface is pressed against the film of the
sol material and maintained, for example, at a pressure of 0.5 to
120 kg/cm.sup.2 and a temperature of 160 to 350.degree. C. for 60
seconds to 60 minutes to nearly complete the
dehydration/polycondensation reaction to gel the sol material. By
removing the mold, a polysiloxane film, which is a gelled film
having an uneven surface that is the inversion of the uneven
surface of the mold, is formed on the surface of the substrate in
such a manner that it is bonded to the substrate. Then, this
polysiloxane film is final-heated at 180 to 350.degree. C. for 10
to 150 minutes not only to polycondense the residual silanol group
of the polysiloxane film but also to vaporize water generated by
the polycondensation so as to obtain a fine film whose volume is
reduced slightly in a thickness direction. Thus, an article having
an uneven surface coated with a film having a surface configuration
which is the inversion of the surface configuration of the mold is
obtained.
[0058] As for the above mold, for example, a female mold having a
target shape is formed by accurately etching the surface of a glass
substrate having a flat surface. Using this mold as a master mold,
a male metal matrix can be produced by an electroless and
electrolytic plating method. A female metal matrix can be produced
by the above plating method from a male metal master mold which is
formed by the above plating method using the above female mold as a
matrix. The male or female matrix can be used as a mold. A metal
such as nickel or chromium is preferably used in the above plating
method.
[0059] Using the master mold produced by the above method, a resin
matrix is fabricated from an ultraviolet curable resin by a 2P
molding method. This can be used as a mold.
[0060] The section of the polysiloxane film which is a gelled film
in the present invention has such a shape as one or a plurality of
circular arcs, oval arcs or mountains. By changing the shape of
this projecting portion, various functions can be provided to the
substrate. For example, the function of a plate microlens array,
the function of a grating or the function of a prism array can be
provided by changing the above shapes to a finely uneven shape.
[0061] The thickness of this polysiloxane film (after final
heating) is preferably 1 .mu.m to 1 mm in terms of average height
between a projecting portion and a recessed portion of the film.
When the film thickness is 20 .mu.m or more, the ratio of the
minimum value (height of the surface of the recessed portion of the
film) to the maximum value (height of the surface of the projecting
portion of the film) of the film thickness is desirably 0.25 or
more, that is, minimum value/maximum value .gtoreq.0.25, to prevent
the film from peeling off from the substrate of the article and
from cracking. When the ratio of the minimum value to the maximum
value of film thickness (minimum value/maximum value) is smaller
than 0.25, the film easily peels off from the substrate at a
portion having the minimum thickness or easily cracks in a film
molding step.
[0062] According to the present invention, a finely uneven
single-layer film of organopolysiloxane having a high heat
resistance of 350.degree. C., a thickness of 1 .mu.m to 1 mm and a
refractive index of 1.50 to 1.54, which is close to that of
ordinary glass, is formed on the substrate of the article. The
organopolysiloxane forming the film preferably contains 5 to 25 wt
%, more preferably 15 to 22 wt %, of an alkyl group such as a
methyl group and also preferably contains 5 to 40 wt %, more
preferably 26 to 37 wt %, of an aryl group such as a phenyl group.
The film is very elastic (less fragile), has high strength and
hardly cracks. Bubbles are not observed in the interior of the film
at the time of molding, and excellent transferability can be
achieved with the result of the extremely high dimensional accuracy
of the fine unevenness of the film surface. Stated more
specifically, when a large number of projecting portions having a
height of 20 to 100 .mu.m are formed, differences in the height of
projecting portions on the surface of the film are 1 .mu.m or less.
A difference between the interval between projecting portions on
the surf ace of the film and the interval between recessed portions
of the mold is smaller than measurement accuracy (0.2 .mu.m).
[0063] The substrate of the article used in the present invention
may have any shape such as a plate-like, curved plate-like or
rod-like shape. The surface of the substrate preferably has a warp
(the length of thermal deformation in a direction perpendicular to
the surface of the substrate per unit length in the surface
direction of the substrate) at 200.degree. C. and 20.degree. C. of
.+-.5 .mu.m or less per cm. When the warp is beyond this range, the
film may peel off from the substrate or crack at the interface in
the film-molding step. It is preferable to select the material,
size and shape of the substrate.
[0064] The substrate preferably has a linear expansion coefficient
of 1.5.times.10.sup.-5/.degree. C. or less. When the linear
expansion coefficient of the substrate is larger than
1.5.times.10.sup.-5/.degree. C., in the case of a plastic substrate
having a high thermal expansion coefficient such as polypropylene
(9 to 15.times.10.sup.-5/.degree. C.), the film peels off from the
substrate or cracks at the interface in the step of molding an
organopolysiloxane film. Ordinary inorganic glass has a linear
expansion coefficient of 1.5.times.10.sup.-5/.degree. C. or less.
At least the surface of the substrate is preferably made from an
oxide. If the surface of the substrate which is in contact with the
organopolysiloxane film is not made from an oxide, adhesion
strength lowers in the film-molding step, and the film may peel off
from the substrate at the interface as the case may be. Preferred
examples of the material of the substrate include oxide glass such
as silicate-based glass, boric acid-based glass, phosphoric
acid-based glass, quartz, ceramics, metals, epoxy resins, glass
fiber-reinforced polystyrene and the like. Although metals are not
bonded to the organopolysiloxane film as they are, they can be
advantageously used as a substrate if their surfaces are treated
with an oxidant in advance.
[0065] When a transparent material, which transmits light having
desired wavelength such as visible, ultraviolet or infrared light,
is used as the substrate in the present invention, the article
having an uneven surface of the present invention can serve as a
transmission optical element such as a lens, diffraction grating or
prism. When a transparent or opaque material is used as the
substrate, a metal (such as aluminum or silver) or dielectric film
(such as magnesium fluoride or titanium oxide) is formed on the
organopolysiloxane film to be suitably used as a reflective
diffraction grating, reflective optical element such as a Fresnel
reflector or other information recording medium such as a
CD-ROM.
EXAMPLES
[0066] An embodiment of the present invention will be described in
detail hereunder.
[0067] Roughly speaking, the process for producing an article whose
surface is finely uneven is carried out by the following steps.
[0068] (1) preparation of an organopolysiloxane solution,
[0069] (2) coating of the solution on a mold or a substrate and
heating of the coating film,
[0070] (3) bonding, heat treatment and releasing, and
[0071] (4) final heating.
[0072] [Preparation of Organopolysiloxane Solutions (Solutions A
and B)]
[0073] There were charged 0.1 mol of phenyltriethoxysilane and 0.15
mol of dimethyldiethoxysilane into a beaker and stirred. Then, 0.25
mol of ethanol was added to this solution and stirred. Thereafter,
an aqueous solution of 0.1 wt % of formic acid dissolved in 1.75
mol (31.5 g) of water was further added and stirred for 2 hours. At
the beginning of agitation, the solution was separated into two
layers but after 2 hours of agitation, a transparent homogeneous
solution was obtained. When this solution was heated in an oven at
80.degree. C. for 12 hours, ethanol, the aqueous solution of formic
acid and the water produced by a polycondensation reaction
volatilized. As a result, the weight and volume of the solution,
whose weight and volume were initially about 91.2 g and about 100
cm.sup.3, were reduced by about 30% to about 27 g and about 30
cm.sup.3, respectively. The thus obtained solution is taken as
solution A. The solution A barely contained ethanol and water, and
about 50% of the ethoxy groups, which were initially contained in
phenyltriethoxysilane and dimethyldiethoxysilane, remained as OH
groups. Further, 0.001 mol of methyl hydrogen diethoxysilane was
added to this solution A and stirred. The obtained solution is
taken as solution B.
[0074] [Coating of Solution to Mold or Substrate and Heat Treatment
of Coating Film]
[0075] The above solution A or B was poured onto the surface of a
mold 2 by the mold pouring process as typically shown in FIG. 1 and
FIG. 2 and onto the surface of a substrate 7 by the substrate
pouring process as typically shown in FIG. 5 to form a layer 1
(FIG. 1) and layer 5 (FIG. 5) having a thickness of 50 .mu.m to 1
mm, and the layers were heated at a temperature of 140 to
180.degree. C. for 20 to 120 minutes. The heat treatment
temperature varied according to the type of the solution. The
solution A was initially heated at 140 to 160.degree. C., and the
temperature was gradually raised to 180.degree. C. over 20 minutes
and maintained at that temperature for 40 minutes. The solution B
was heated at 160.degree. C. for 20 minutes. A gelled film
(viscosity: 10.sup.4 to 10.sup.8 poise) which was plastically
deformable could be formed on the mold 2 or the substrate 7 by
these heat treatments.
[0076] [Bonding, Heat Treatment and Releasing]
[0077] In the case of the mold pouring process, the coated surface
(gelled film) was brought into contact with the surface of the
substrate 3 as shown in FIG. 3 and heated at 160 to 250.degree. C.
for 20 to 60 minutes in this state to be bonded to the substrate.
After the coating film was completely gelled, the mold 2 was
removed from the substrate 3. As a result, a finely uneven plate 4
having a film, which has the shape of the mold transferred as shown
in FIG. 4, bonded thereto was obtained.
[0078] In the case of the substrate pouring process, the mold 6 was
held against the gelled film 5 as shown in FIG. 6 and heated at
250.degree. C. for 20 minutes while pressed with a pressure of 2
kg/cm.sup.2. Thereafter, the film was removed from the mold. As a
result, a finely uneven plate 8 having the shape of the mold
transferred as shown in FIG. 7 was obtained.
[0079] [Final Heating]
[0080] The finely uneven plates 4 and 8 which had been released
from the mold were heated at 350.degree. C. for 15 minutes to
obtain articles having an uneven surface.
[0081] The performance and characteristic properties of the
obtained articles having an uneven surface were evaluated.
[0082] [Measurement of Differences in Height of Projecting
Portions]
[0083] The differences in the height of projecting portions of the
outermost layer were measured by the measurement of height with a
laser microscope.
[0084] [Measurement of Heat Resistance and Optical
Characteristics]
[0085] A heat resistance test was made on articles having an uneven
surface produced in Examples and Comparative Examples as follows.
In the test, the articles were maintained at 300.degree. C. for 2
hours and returned to room temperature to observe the emergence of
cracks for the purpose of evaluating heat resistance. A He--Ne
laser was used to measure and evaluate the diffraction pattern of a
diffraction grating, the converging performance of a microlens and
the amount of reflection from the interior of a substrate at an
incident angle on the surface of the substrate of about 6.degree.
before and after the heat resistance test. The d-ray refractive
index of a film portion was measured using an Abbe
refractometer.
Example 1
[0086] A 10-cm.sup.2 soda lime glass substrate having a thickness
of 1.1 mm (coefficient of linear expansion:
1.0.times.10.sup.-5/.degree. C.) was prepared as a glass substrate.
A nickel (Ni) mold having 80,000 straight V-shaped grooves (groove
width: 1 .mu.m, groove depth: 1 .mu.m, groove section: regular
triangle, groove length: 9 cm, interval between adjacent grooves
(measured at the center of groove): about 2 .mu.m) (to be referred
to as "V-shaped groove Ni mold" hereinafter), which were parallel
to one another, was prepared as a mold. A finely uneven plate,
which was a diffraction grating, was formed in accordance with the
substrate pouring process using the above substrate, mold and
solution A so that the thickness of a flat area (devoid of linear
projections) of the film became about 40 .mu.m. The thickness of
the coated solution was about 60 .mu.m, and the heat treatment
after coating was carried out by first heating at 160.degree. C.,
raising the temperature gradually to 180.degree. C. over 20 minutes
and maintaining that temperature for 40 minutes. The pressure was 2
kg/cm.sup.2, the heating conditions comprised a temperature of
250.degree. C. and a time of 20 minutes, and the final heating
conditions comprised a temperature of 350.degree. C. and a time of
15 minutes.
[0087] The thus formed organopolysiloxane film was transparent and
had a thickness in its flat portion of about 40 .mu.m and a
refractive index of 1.51. The film contained 18 wt % of a methyl
group and 31 wt % of a phenyl group. When the heights of 100 points
of 10 linear projecting portions selected at random from 80,000
projecting portions at intervals in a lengthwise direction of 9 mm
were measured, the average height of linear projecting portions of
this substrate was 1.0 .mu.m and the standard deviation was 0.05
.mu.m. When the heat resistance of the substrate was evaluated, the
film did not crack, and the outer appearance, the height of each
projecting portion of the film, its standard deviation and
diffraction pattern were not changed from those before the heat
resistance test.
Comparative Example 1
[0088] Methyltriethoxysilane, ethanol and water were mixed together
in a molar ratio of 1:1:4, and 0.01 mol of hydrochloric acid was
added as a catalyst to the resulting mixture and stirred at room
temperature for about 30 minutes to prepare a sol solution.
[0089] A finely uneven substrate was formed using the same
substrate and mold as used in Example 1 in the same manner as in
Example 1 except that the above sol solution was used in place of
the solution A of Example 1. However, the film cracked during
cooling after the final heating conducted at 350.degree. C., part
of the film peeled off and the evaluation of size could not be
carried out. When the evaluation of heat resistance was made on
this substrate, a crack in the film enlarged, whereby the film
further peeled off partly. Therefore, the height of each projecting
portion of the film and its standard deviation after the heat
resistance test could not be measured and there was a great change
in diffraction pattern as compared with that before the heat
resistance test.
Comparative Example 2
[0090] Phenyltriethoxysilane, ethanol and water were mixed together
in a molar ratio of 1:1:4, and 0.01 mol of hydrochloric acid was
added as a catalyst to the resulting mixture and stirred at room
temperature for about 30 minutes to prepare a sol solution.
[0091] A finely uneven substrate was formed using the same
substrate and mold as used in Example 1 in the same manner as in
Example 1 except that the above sol solution was used in place of
the solution A of Example 1. However, the film cracked during
cooling after the final heating conducted at 350.degree. C., and
part of the film peeled off like methyltriethoxysilane of
Comparative Example 1, so that the film could not be evaluated.
There was a great change in the diffraction pattern of the
substrate as compared with that before the heat resistance
test.
Example 2
[0092] A finely uneven substrate was formed using the solution A
and the same glass substrate as used in Example 1 in accordance
with the mold pouring process. A Nickel (Ni) mold, which had about
22,500 substantially hemispherically concave portions with a
curvature radius of 30 .mu.m, which comprise about 150 of such
contiguous portions in a longitudinal direction and about 150 of
such contiguous portions in a transverse direction, was used as a
mold. A finely uneven substrate, which was a microlens, was formed
to ensure that the thickness of a flat area of the film after final
heating was about 15 .mu.m and the maximum thickness from the top
of the hemisphere of the film was 40 .mu.m. The thickness of the
coating film of the solution on the Ni mold was about 60 .mu.m. As
for the heat treatment conditions after coating, the temperature
was initially set to 160.degree. C., raised to 180.degree. C. over
20 minutes and maintained at that temperature for 40 minutes. The
heating conditions after bonding the substrate comprised a
temperature of 250.degree. C. and a time of 20 minutes and the
final heating conditions comprised a temperature of 350.degree. C.
and a time of 15 minutes.
[0093] The thus formed organopolysiloxane film was transparent and
had a maximum thickness of about 40 .mu.m and a refractive index of
1.51. This organopolysiloxane film was bonded to the surface of the
glass substrate. The focusing distance of the fabricated microlens
was 95 to 98 .mu.m. The film contained 18 wt % of a methyl group
and 31 wt % of a phenyl group. As for the height of each projecting
portion of the substrate (measured from the flat surface (surface
opposite to the projecting portion) of the film), when 100
hemispherical projecting portions were randomly selected and
measured, the average height of the projecting portions was 40.0
.mu.m and the standard deviation was 0.12 .mu.m. When the
evaluation of heat resistance was made on this substrate, the film
neither cracked or peeled off and the focusing distances of all the
projecting portions were in the range of 95 to 98 .mu.m and
remained unchanged from values before the heat resistance test.
When the diameter of a convergent spot obtained by inputting
parallel rays perpendicularly from the opposite side of the film
was measured, the diameters of the convergent spots of all the
convex lenses were 3 .mu.m or less and remained unchanged from
values before the heat resistance test.
Example 3
[0094] A finely uneven substrate was formed using a quartz
substrate as a glass substrate, a V-shaped Ni mold used in Example
1 and solution B in accordance with the substrate pouring process
so that the thickness of a flat area of the film became about 100
.mu.m. A heat treatment after the coating of the solution was
carried out at 160.degree. C. for 20 minutes. The pressure was 2
kg/cm.sup.2, the heating conditions comprised a temperature of
250.degree. C. and a time of 20 minutes and the final heating
conditions comprised a temperature of 350.degree. C. and a time of
15 minutes.
[0095] The thus formed organopolysiloxane film was transparent and
had a maximum thickness of about 100 .mu.m and a refractive index
of 1.50. The film contained 18 wt % of a methyl group and 31 wt %
of a phenyl group. When the evaluation of heat resistance was made
on this substrate, the film did not crack and there was no change
in the appearance and diffraction pattern of the film.
[0096] It is understood from the results of Examples and
Comparative Examples that the organopolysiloxane layer of the
present invention has high heat resistance and does not either
discolor or peel off.
Example 4
[0097] A 25-mm.sup.2 soda lime glass substrate having a thickness
of 3 mm was prepared as a glass substrate. A release coating-coated
glass mold, which has 50 semi-cylindrical recessed portions of each
cylinder having a curvature radius of 20 .mu.m arranged in parallel
on the surface, was used as a mold. A solution C, prepared by
adding formamide to solution A in an amount of 5% based on metal
alkoxide contained in the solution A and stirring for 30 minutes,
was poured onto the substrate to a thickness of about 50 .mu.m in
accordance with the substrate pouring process to form a lenticular
lens. A heat treatment after coating was carried out at 160.degree.
C. for 60 minutes. The film was pressed at a pressure of 2
kg/cm.sup.2, released from the mold and finally heated at
350.degree. C. for 15 minutes. The thus formed organopolysiloxane
film was transparent. When 20 cylindrical projecting portions of
the substrate were randomly selected and the heights thereof were
measured, the average height of the projecting portions from the
surface of the substrate was 30 .mu.m and the standard deviation
was 0.10 .mu.m. When the evaluation of heat resistance was made on
this substrate, the film did not crack and there was no change in
appearance, the height of each projecting portion of the film, its
standard deviation and the pitch of the projecting portions.
[0098] According to the present invention, the volume shrinkage of
the polysiloxane film was small at the time of curing and the film
is very elastic (less fragile) due to large amounts of an alkyl
group such as a methyl group and an aryl group such as a phenyl
group remaining in the film. Therefore, the film has high strength
and hardly cracks. Accordingly, an optical element or other article
having a thick organopolysiloxane film and high heat resistance can
be obtained at a low cost.
* * * * *