U.S. patent application number 10/934425 was filed with the patent office on 2005-02-03 for optical element and optical equipment incorporating the same.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Ukuda, Hideo.
Application Number | 20050024727 10/934425 |
Document ID | / |
Family ID | 26620352 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050024727 |
Kind Code |
A1 |
Ukuda, Hideo |
February 3, 2005 |
Optical element and optical equipment incorporating the same
Abstract
In order to provide an optical element which prevents fogging of
a surface and has an antireflection characteristic and
morphological stability, an optical element of the present
invention includes: a substrate; and a first water absorption layer
containing a water-absorbing polymer and inorganic particles, a
high refractive layer, and a second water absorption layer which
are formed on a substrate in this order, in which the water
absorption layer is made of a material containing a mixture of a
water-absorbing polymer and an inorganic substance.
Inventors: |
Ukuda, Hideo; (Kanagawa,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
TOKYO
JP
|
Family ID: |
26620352 |
Appl. No.: |
10/934425 |
Filed: |
September 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10934425 |
Sep 7, 2004 |
|
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10216195 |
Aug 12, 2002 |
|
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6830346 |
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Current U.S.
Class: |
359/507 |
Current CPC
Class: |
G02B 1/11 20130101 |
Class at
Publication: |
359/507 |
International
Class: |
G02B 001/00; G02B
005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2001 |
JP |
243546/2001 (PAT. |
Jul 31, 2002 |
JP |
223128/2002 (PAT. |
Claims
What is claimed is:
1. An optical element having an antifog characteristic, comprising:
an optical component; and a first water absorption layer containing
a water-absorbing polymer, which is formed on the optical
component, wherein the first water absorption layer contains a
mixture of a water-absorbing polymer and an inorganic substance,
and wherein the inorganic substance is inorganic particles, which
are mixed in the first water absorption layer in particulate
form.
2. The optical element according to claim 1, wherein a rate of the
inorganic substance mixed in the first water absorption layer is 5
to 60 w %.
3. The optical element according to claim 1, wherein a rate of the
inorganic substance mixed in the first water absorption layer is 15
to 50 w %.
4. The optical element according to claim 1, wherein the inorganic
substance is SiO.sub.2.
5. The optical element according to claim 1, wherein the inorganic
particles are contained in the first water absorption layer as
particles having a diameter of 5 nm to 20 nm.
6. The optical element according to claim 1, wherein a thickness of
the first water absorption layer is 1 .mu.m to 20 .mu.m.
7. The optical element according to claim 1, wherein the optical
element is one selected from the group consisting of a filter for a
photographic lens or a projection lens, a mirror, and a lens.
8. The optical element according to claim 1, further having an
antireflection characteristic.
9. An optical equipment comprising an optical element as set forth
in claim 1.
10. The optical equipment according to claim 9, wherein the optical
element is exposed to the outside.
11. The optical equipment according to claim 9, wherein the optical
equipment is an image pickup apparatus including an image pickup
optical system and a finder optical system, the finder optical
system including the optical element.
12. The optical equipment according to claim 11, wherein the
optical element is an eyepiece of the finder optical system.
Description
[0001] This application is a division of application Ser. No.
10/216,195, filed Aug. 12, 2002, which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an antifog and
antireflection optical element. In particular, the present
invention relates to an optical element such as a photographic
lens, a projection lens, a filter, and a mirror which is excellent
in antifog, antireflection, and weather resistance, or optical
equipment such as electrophotographic equipment incorporating such
an optical element.
[0004] 2. Related Background Art
[0005] Conventionally, for preventing fog of a lens, a filter, a
mirror, and the like, a method of coating a surface with a
surfactant is generally conducted. Recently, it is also known that
fog is prevented by coating a base such as a lens, a filter, a
mirror, or the like with a water-absorbing material instead of a
surfactant. Furthermore, conventionally, natural polymers are known
as a water-absorbing materials, e.g., starch-based polymers such as
a starch acrylonitrile graft polymer hydrolysate; and
cellulose-based polymers such as cellulose acrylonitrile graft
polymer. Also known as water-absorbing material are synthetic
polymers, e.g., polyvinyl alcohol-based polymers such as a
polyvinyl alcohol cross-linked polymer; acrylic polymers such as a
sodium polyacrylate cross-linked substance; polyether-based
polymers such as a polyethylene glycol/diacrylate cross-linked
polymer, etc.
[0006] However, the above-mentioned conventional antifog optical
elements have the following problems. First, in the case where a
surfactant is used for preventing fog, duration of its effect is
very short, and unless the surfactant is applied again within
several hours or days, its effect cannot be maintained.
Furthermore, in the case where dirt on the surface of an optical
element is wiped off with water or the like, a surfactant film is
removed, and its effect is lost.
[0007] Furthermore, in the case where various water-absorbing
materials are applied to form an antifog film for preventing fog,
the duration of its effect is remarkably enhanced as compared with
the case of using a surfactant. However, according to the study by
the inventors of the present invention, the following was found: in
the case where the water-absorbing material is used for an antifog
film, when a low refractive material layer is coated onto the
antifog film so as to obtain an antireflection effect, the antifog
characteristic of the antifog film itself tends to be lost.
Furthermore, in the case where the thickness of the water
absorption film is reduced, and the thickness of an optical film is
adjusted to an odd multiple of one-quarter of the wavelength of an
antireflection target to obtain an antireflection film, the
thickness of the water-absorbing film becomes too small, and
sufficient antifog characteristic cannot be obtained.
[0008] In order to solve the above-mentioned problem, the inventors
of the present invention have proposed in Japanese Patent
Application Laid-Open No. 11-109105 that a film having a different
refractive index is formed on a water absorption film to form an
antireflection film. However, in the above-mentioned antifog and
antireflection optical element, the following phenomenon is
observed sometimes: when the state of containing water continues, a
material in the water absorption film moves, resulting in poor
surface precision.
SUMMARY OF THE INVENTION
[0009] Therefore, with the foregoing in mind, it is an object of
the present invention to provide an optical element having both an
antifog effect and antireflection characteristic as well as
morphological stability, or to provide optical equipment in which
moisture condensation or the like does not occur when incorporating
the optical element therein.
[0010] These and other advantages of the present invention will
become apparent to those skilled in the art upon reading and
understanding the following detailed description with reference to
the accompanying figures.
[0011] In order to solve the above-mentioned problems, according to
a first aspect of the present invention, there is provided an
optical element having an antifog characteristic, characterized by
comprising: an optical component (including a simple glass
substrate etc); and a first water absorption layer containing a
water-absorbing polymer which is formed on the optical component,
in which the first water absorption layer contains a mixture of a
water-absorbing polymer and an inorganic substance.
[0012] Also, in the optical element, a rate of the inorganic
substance mixed in the first water absorption layer is 5 to 60 w %
(% by weight).
[0013] Also, a rate of the inorganic substance mixed in the first
water absorption layer is 15 to 50 w % (% by weight).
[0014] Also, the inorganic substance is inorganic particles.
[0015] Also, the inorganic substance is SiO.sub.2.
[0016] Also, the inorganic particles are mixed in the first water
absorption layer as they are, that is, in the form of
particles.
[0017] Also, the inorganic particles are contained in the first
water absorption layer as particles having a diameter of 5 nm to 20
nm.
[0018] Also, a thickness of the first water absorption layer is 1
.mu.m to 20 .mu.m.
[0019] Also, there is provided an optical element characterized by
further comprising a high refractive layer formed on the first
water absorption layer, and a second water absorption layer
containing a water-absorbing polymer which is formed on the high
refractive layer.
[0020] Also, the second water absorption layer contains the
inorganic substance.
[0021] Also, a thickness of the second water absorption layer is
less than 1 .mu.m.
[0022] Also, a thickness of the second water absorption layer is
less than 200 .mu.m.
[0023] Also, a plurality of antireflection layers, each consisting
of the high refractive layer and the second water absorption layer
that are integrally formed, may be stacked to constitute an optical
element.
[0024] Also, a water-absorbing polymer in at least one of the first
water absorption layer and the second water absorption layer is a
polyacrylic acid or polyvinyl alcohol.
[0025] Also, an optical element is one selected from the group
consisting of a filter for a photographic lens or a projection
lens, a mirror, and a lens.
[0026] Also, the optical element has antireflection
characteristic.
[0027] Also, the optical equipment has the above optical
component.
[0028] Also, the optical element is exposed to the outside.
[0029] Also, the optical equipment is an image pickup apparatus
including an image pickup optical system and a finder optical
system, the finder optical system including the optical
element.
[0030] Also, the optical element is an eyepiece of the finder
optical system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is comprised of FIGS. 1A and 1B showing tables for
evaluation of optical elements produced in Examples 1 to 4 and
Comparative Examples 1 and 2.
[0032] FIG. 2 is a schematic view of a camera in Example 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] In an embodiment of the present invention, the
above-mentioned configuration is adopted, in which inorganic
particles are mixed in a water-absorbing polymer of the first water
absorption layer so as to suppress movement of a material in the
water absorption layer, whereby surface precision is prevented from
being degraded. More specifically, by using a mixture of a
water-absorbing polymer and inorganic particles in the first water
absorption layer, it becomes possible to enhance morphological
stability. At this time, when the rate of the inorganic particles
is from 10 w % to 60 w %, antireflection, water absorption (water
permeability), and morphological stability are not lost. Therefore,
an optical element having both an antifog effect and antireflection
characteristic as well as morphological stability can be provided.
Furthermore, optical equipment in which moisture condensation or
the like does not occur when incorporating the above-mentioned
optical element therein can be provided.
[0034] In the above-mentioned composition of the present invention,
as the water-absorbing polymer to be a material for the water
absorption film, various conventionally known polymers shown below
can be used. That is, as natural polymer derivatives, there are:
starch-based polymers such as a starch acrylonitrile graft polymer
hydrolysate; and cellulose-based polymers such as cellulose
acrylonitrile graft polymer. Examples of synthetic polymers
include: polyvinyl alcohol based polymers such as a polyvinyl
alcohol cross-linked polymer; acrylic polymers such as a sodium
polyacrylate cross-linked substance; and polyether-based polymers
such as a polyethylene glycol/diacrylate cross-linked polymer.
Among them, highly water-absorptive materials such as polyacrylic
acids, polyvinyl alcohols, and the like are preferably used.
[0035] Examples of polyacrylic acids used here include polyacrylic
acid, polymethacrylic acid, polyacrylamide, and salts thereof
(potassium polyacrylate, sodium polyacrylate). Polyacrylic acid and
polymethacrylic acid are preferably used.
[0036] It is preferable that inorganic particles are mixed in an
amount of 5 to 60 w % into a material for the water absorption
film. In the case where the rate of the inorganic particles is 5 w
% or less, durability is degraded. In the case where the rate of
the inorganic particles is 60 w % or more, water absorption is
degraded rapidly, resulting in loss of antifog characteristic. When
the rate of the inorganic particles is set to be in a range of 15
to 50 w %, a film with good balance having both durability and
water absorption characteristic can be formed.
[0037] Herein, the inorganic particles are preferably present in
the film as they are, that is, in the form of particles. The
inorganic particles are present as particles preferably having a
diameter of 3 nm to 30 nm, and more preferably having a diameter of
5 nm to 20 nm.
[0038] Herein, it is preferable that the thickness of the first
water absorption film formed on a substrate is set to be 1 m or
more so as to increase the amount of its water absorption and
enhance the antifog characteristic. Furthermore, a thickness of 20
m or less is preferable so as to prevent the water absorption film
from excessively expanding due to excessive water absorption. The
thickness is more preferably set to be 2 m to 8 m.
[0039] Furthermore, the high refractive layer is obtained by
soaking a base including a water absorption film in a solution
containing a metal alkoxide as a main component of a dissolved
substance, and pulling up the base to coat the base with the
solution, followed by sintering.
[0040] Examples of the metal alkoxide include compounds represented
by the following formulae (1) and (2):
M(OR)a (1)
and
M(OR)n(X)a-n (2)
[0041] where "M" is an atom selected from the group consisting of
Si, Al, Ti, Zr, Ca, Fe, V, Sn, Li, Be, B, and P; "R" is an alkyl
group, an alkyl group having a functional group, or a halogen; "a"
is a valence of "M", and "n" is an integer of 1 to "a".
[0042] In the above, an alkyl group containing a carbonyl,
carboxyl, amino, vinyl, or epoxy group is preferable as "X".
[0043] Examples of particularly preferable inorganic alkoxide
include Si(OC.sub.2H.sub.5).sub.4, Al(O-iso-C.sub.3H.sub.7).sub.3,
Ti(O-iso-C.sub.3H7).sub.4, Zr(O-t-C.sub.4H9).sub.4,
Zr(O-n-C.sub.4H9).sub.4, Ca(OC.sub.2H5).sub.2,
Fe(OC.sub.2H.sub.5).sub.3, V(O-iso-C.sub.3H.sub.7).sub.4,
Sn(O-t-C.sub.4H.sub.9).sub.4, Li(OC.sub.2H.sub.5),
Be(OC.sub.2H.sub.5).sub.2, B(OC.sub.2H.sub.5).sub.3,
P(OC.sub.2H.sub.5).sub.2, and P(OCH.sub.3).sub.3. In order to
decrease the reflectance of the antifog and antireflection optical
element, the refractive index of the high refractive thin film is
preferably 1.68 or more. For this purpose, in particular,
Al(O-iso-C.sub.3H.sub.7).sub.3, Ti(O-iso-C.sub.3H.sub.7).sub.4,
Zr(O-t-C.sub.4H.sub.9), Zr(O-n-C.sub.4H.sub.9).sub.4, and
Sn(O-t-C.sub.4H.sub.9).sub.4 are preferable.
[0044] A second water absorption layer is formed on the
above-mentioned first water absorption layer with a high refractive
layer interposed therebetween, whereby antireflection
characteristics can be exhibited. Herein, the second water
absorption layer can be obtained by forming a water-absorbing
polymer with an optical film thickness.
[0045] Herein, although it is preferable that the second water
absorption layer contains an inorganic substance, the second water
absorption layer may not contain it. The thickness of the second
water absorption layer is less than 1 m. In particular, the
thickness of the second water absorption layer is more desirably
less than 200 nm. Furthermore, it may also be possible to stack a
plurality of antireflection layers each consisting of the high
refractive layer and the second water absorption layer that are
integrally formed, to thereby form the optical element of the
present invention.
[0046] The antifog and antireflection optical element produced by
using such a procedure has an antifog characteristic, as well as an
enhanced antireflection characteristic and abrasion resistance.
[0047] Furthermore, the antifog and antireflection optical element
of the present invention has antifog characteristic and excellent
light transmittance, and is applicable to various optical elements
in which fogging occurs due to condensation of moisture.
[0048] Furthermore, the first water absorption layer may be formed
on an optical component on which another film has already been
formed, instead of being formed directly on a substrate such as a
glass substrate and a plastic substrate. In the following Examples,
the above-mentioned water absorption layer (water absorption film)
is to be formed on a glass substrate, a plastic substrate, and an
optical component on which another film is formed.
[0049] Hereinafter, the present invention will be described based
on the following Examples.
EXAMPLE 1
[0050] In Example 1, 10 parts by weight of polyvinyl alcohol
(number-average polymerization: 2000; saponification: 88 mol %) was
dissolved by heating in 100 parts by weight of water to prepare a
solution. To this solution, a solution in which 0.5 parts by weight
of hexamethoxymethylol melamine, 0.05 parts by weight of ammonium
paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 100 parts by
weight of methanol was added. The resultant mixture was stirred at
room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, 2.5 parts by weight of a methanol solution
containing 20 w % of SiO.sub.2 particles was mixed in the antifog
coating solution, and the rate of the inorganic particles with
respect to the concentration of a total solid content was set to be
5 w %.
[0051] The solution thus obtained was applied to a filter
(substrate) of glass (white plate glass) having a thickness of 1 mm
by dip coating, dried, and cured at 150.degree. C. for 15 minutes,
whereby a water absorption layer (thickness: 4 .mu.m) was formed on
both surfaces of the glass.
[0052] Thereafter, a first solution, in which 7.5 g of titanium
tetraisopropoxide (Ti(O-iso-Pr).sub.4Pr: C.sub.3H.sub.7) is
dissolved in 130 g of isobutyl acetate, was prepared. Then, a
solution, in which 0.50 g of 2-normal HCl (2 mol/l Hydrochloric
Acid) and 0.25 g of water are dissolved in 10 g of i-propanol, was
mixed with 100 g of isobutyl acetate to prepare a second solution.
The second solution was added to the first solution, and the
resultant mixture was stirred at room temperature for 24 hours to
set a hydrolysis ratio to be 0.75 to obtain a high refractive layer
forming solution. The above-mentioned water absorption layer was
soaked in the high refractive layer forming solution, pulled up by
dip coating at 30 mm/min so as to coat the water absorption layer
with the high refractive layer forming solution, and sintered at
150.degree. C. for 5 minutes, whereby a high refractive layer was
formed.
[0053] A layer (top layer) to be formed on the high refractive
layer was obtained as follows: the antifog coating solution
containing the above-mentioned inorganic particles was diluted with
a mixture containing methanol and water at a ratio of 1:1 so that
the viscosity became 14 cp to obtain a solution; and the solution
thus obtained was applied onto the high refractive layer by dip
coating, and sintered at 150.degree. C. for 15 minutes, thereby
adjusting the film thickness to 130 nm.
[0054] The antifog characteristics of the antifog film thus formed
were evaluated by a method (Evaluation method 1) in which the
breath is applied over the antifog film in an atmosphere of room
temperature (temperature: 30.degree. C., humidity: 80%) and whether
fogging occurs is examined, and by a method (Evaluation method 2)
in which the antifog film is transferred from a place at 5.degree.
C. to a place at room temperature (temperature 30.degree. C.;
humidity 80%) to observe whether fog develops on the film.
[0055] As a result, the antifog film produced in Example 1 was "not
changed" according to both Evaluation methods 1 and 2.
[0056] Regarding the antireflection performance, the reflectance
becomes about 0.035 with respect to light in the vicinity of a
wavelength of 500 nm at which the reflectance becomes the lowest
(FIGS. 1A and 1B).
[0057] The durability of the antifog film thus formed was evaluated
by a method (Evaluation method 3) in which a sample is wiped thirty
times with wiping paper (Dusper; produced by OZU Co., Ltd. Tokyo)
while applying a load of 300 g and a change appearing on a lens
surface is observed, and by a method (Evaluation method 4) in which
a sample is wiped thirty times with wiping paper (Dusper; produced
by OZU Co. Ltd. Tokyo) containing water while applying a load of
300 g and a change appearing on a lens surface is observed.
[0058] In both Evaluation methods 3 and 4, the result "there is no
change" was obtained.
[0059] Furthermore, regarding the morphological stability, a filter
was soaked in water, allowed to stand at a temperature of
60.degree. C. and a humidity of 90% for 48 hours, and dried.
Thereafter, the surface precision was observed by an optical
interferometer. As a result, an increase of three neutron lines was
observed as shown in FIGS. 1A and 1B.
COMPARATIVE EXAMPLE 1
[0060] In Comparative Example 1, 10 parts by weight of polyvinyl
alcohol (number-average polymerization: 2000; saponification: 88
mol %) was dissolved by heating in 100 parts by weight of water to
prepare a solution. To this solution, a solution in which 0.5 parts
by weight of hexamethoxymethylol melamine, 0.05 parts by weight of
ammonium paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 100 parts by
weight of methanol were added. The resultant mixture was stirred at
room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, unlike in Example 1, the antifog coating
solution is not mixed with the inorganic particles.
[0061] The solution thus obtained was applied to a filter
(substrate) of glass (white plate glass) with a thickness of 1 mm
by dip coating, and then was dried and cured at 150.degree. C. for
15 minutes, whereby a water absorption layer (thickness: 4 .mu.m)
was formed on both surfaces of the glass.
[0062] Thereafter, a first solution, in which 7.5 g of titanium
tetraisopropoxide (Ti(O-iso-Pr).sub.4Pr:C.sub.3H.sub.7) is
dissolved in 130 g of isobutyl acetate, was prepared. Then, a
solution, in which 0.50 g of 2-normal HCl and 0.25 g of water are
dissolved in 10 g of i-propanol, was mixed with 100 g of isobutyl
acetate to prepare a second solution. The second solution was added
to the first solution, and the resultant mixture was stirred at
room temperature for 24 hours to set a hydrolysis ratio to be 0.75
to obtain a high refractive layer forming solution. The
above-mentioned water absorption layer was soaked in the high
refractive layer forming solution, pulled up by dip coating at 30
mm/min so as to coat the water absorption layer with the high
refractive layer forming solution, and sintered at 150.degree. C.
for 5 minutes, whereby a high refractive layer was formed.
[0063] A layer (top layer) to be formed on the high refractive
layer was obtained as follows: the antifog coating solution was
diluted with a mixture containing methanol and water at a ratio of
1:1 to obtain a solution having the viscosity adjusted to 14 cp;
the solution thus obtained was applied to the high refractive layer
by dip coating, and sintered at 150.degree. C. for 15 minutes,
thereby adjusting the film thickness to 130 nm.
[0064] The antifog characteristics of the antifog film thus formed
were evaluated according to a method (Evaluation method 1) in which
the breath is applied over the antifog film in an atmosphere of
room temperature (temperature: 30.degree. C., humidity: 80%) to
examine whether fogging occurs, and by a method (Evaluation method
2) in which the antifog film was transferred from a place at
5.degree. C. to a place at room temperature (temperature 30.degree.
C.; humidity 80%) to observe whether fogging occurs.
[0065] The result of Evaluation method 1 with respect to the
antifog film formed in Example 1 was that "there is no particular
change in antifog characteristics when the breath is applied at
room temperature". The result of Evaluation method 2 was that
"there is no particular change even when the antifog film is
transferred from a place at 5.degree. C. to a place at room
temperature".
[0066] Regarding the antireflection performance, the reflectance
becomes about 0.035 with respect to light in the vicinity of a
wavelength of 500 nm at which the reflectance becomes the lowest
(FIGS. 1A and 1B).
[0067] The durability of the antifog film thus formed was evaluated
by a method (Evaluation method 3) in which a sample is wiped thirty
times with wiping paper (Dusper; produced by OZU Co., Ltd. Tokyo)
while applying a load of 300 g and a change appearing on a lens
surface is observed, and by a method (Evaluation method 4) in which
a sample is wiped thirty times with wiping paper (Dusper; produced
by OZU Co. Ltd. Tokyo) containing water while applying a load of
300 g and a change appearing on a lens surface is observed.
[0068] In both Evaluation methods 3 and 4, the result "there is no
change" was obtained.
[0069] Furthermore, regarding the morphological stability, a filter
was soaked in water, allowed to stand at a temperature of
60.degree. C. and a humidity of 90% for 48 hours, and dried.
Thereafter, the surface precision was observed by an optical
interferometer. Consequently, an increase of five neutron lines was
observed as shown in FIGS. 1A and 1B.
EXAMPLE 2
[0070] In Example 2, 10 parts by weight of polyvinyl alcohol
(number-average polymerization: 2000; saponification: 88 mol %) was
dissolved by heating in 100 parts by weight of water to prepare a
solution. To this solution, a solution in which 0.5 parts by weight
of hexamethoxymethylol melamine, 0.05 parts by weight of ammonium
paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 90 parts by
weight of methanol was added. The resultant mixture was stirred at
room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, 12.5 parts by weight of a methanol solution
containing 20 w % of SiO.sub.2 particles was mixed in the antifog
coating solution, and the rate of the inorganic particles with
respect to the concentration of a total solid content was set to be
20 w %.
[0071] Hereinafter, an antifog film was produced by the same
procedure as that in Example 1. The antifog film produced in
Example 2 was evaluated by Evaluation methods 1 to 4.
[0072] The results of Evaluation methods 1 and 2 were both that
"there is no particular change". The results of Evaluation methods
3 and 4 were also both that "there is no particular change".
[0073] Regarding the antireflection performance of the antifog film
produced in Example 2, the reflectance becomes about 0.035 with
respect to light in the vicinity of a wavelength of 500 nm at which
the reflectance becomes the lowest (FIGS. 1A and 1B).
[0074] Furthermore, regarding the morphological stability, an
antifog film (filter) was soaked in water, allowed to stand at a
temperature of 60.degree. C. and a humidity of 90% for 48 hours,
and dried. Thereafter, the surface precision was observed by an
optical interferometer. Consequently, an increase of two neutron
lines was observed as shown in FIGS. 1A and 1B.
EXAMPLE 3
[0075] In Example 3, 10 parts by weight of polyvinyl alcohol
(number-average polymerization: 2000; saponification: 88 mol %) was
dissolved by heating in 100 parts by weight of water to prepare a
solution. To this solution, a solution in which 0.5 parts by weight
of hexamethoxymethylol melamine, 0.05 parts by weight of ammonium
paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 73.6 parts
by weight of methanol was added. The resultant mixture was stirred
at room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, 33 parts by weight of a methanol solution
containing 20 w % of SiO.sub.2 particles was mixed in the antifog
coating solution, and the rate of the inorganic particles with
respect to the concentration of a total solid content was set to be
40 w %.
[0076] Hereinafter, an antifog film was produced by the same
procedure as that in Example 1. The antifog film produced in
Example 2 was evaluated by Evaluation methods 1 to 4.
[0077] The results of Evaluation methods 1 and 2 were that "there
is no particular change". The results of Evaluation methods 3 and 4
were also that "there is no particular change".
[0078] Regarding the antireflection performance of the antifog film
produced in Example 2, the reflectance becomes about 0.035 with
respect to light in the vicinity of a wavelength of 500 nm at which
the reflectance becomes the lowest (FIGS. 1A and 1B).
[0079] Furthermore, regarding the morphological stability, an
antifog film (filter) was soaked in water, allowed to stand at a
temperature of 60.degree. C. and a humidity of 90% for 48 hours,
and dried. Thereafter, the surface precision was observed by an
optical interferometer. Consequently, an increase of one neutron
line was observed as shown in FIGS. 1A and 1B.
COMPARATIVE EXAMPLE 2
[0080] In Comparative Example 2, 10 parts by weight of polyvinyl
alcohol (number-average polymerization: 2000; saponification: 88
mol %) was dissolved by heating in 100 parts by weight of water to
prepare a solution. To this solution, a solution in which 0.5 parts
by weight of hexamethoxymethylol melamine, 0.05 parts by weight of
ammonium paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 45.4 parts
by weight of methanol was added. The resultant mixture was stirred
at room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, 78 parts by weight of a methanol solution
containing 30 w % of SiO.sub.2 particles was mixed in the antifog
coating solution, and the rate of the inorganic particles with
respect to the concentration of a total solid content was set to be
70 w %.
[0081] Hereinafter, an antifog film was produced by the same
procedure as that in Example 1. The antifog film produced in
Comparative Example 2 was evaluated by Evaluation methods 1 to
4.
[0082] The results of Evaluation methods 1 and 2 were both that
"there is no particular change". Furthermore, the result of
Evaluation method 3 was that "fogging is observed", and the result
of Evaluation method 4 was that "fogging is observed after 5
seconds."
[0083] Regarding the antireflection performance of the antifog film
produced in Example 2, the reflectance becomes about 0.035 with
respect to light in the vicinity of a wavelength of 500 nm at which
the reflectance becomes the lowest (FIGS. 1A and 1B).
[0084] Furthermore, regarding the morphological stability, an
antifog film (filter) was soaked in water, allowed to stand at a
temperature of 60.degree. C. and a humidity of 90% for 48 hours,
and dried. Thereafter, the surface precision was observed by an
optical interferometer. Consequently, an increase of neutron lines
was not observed.
EXAMPLE 4
[0085] In Example 4, 10 parts by weight of polyvinyl alcohol
(number-average polymerization: 2000; saponification: 88 mol %) was
dissolved by heating in 100 parts by weight of water to prepare a
solution. To this solution, a solution in which 0.5 parts by weight
of hexamethoxymethylol melamine, 0.05 parts by weight of ammonium
paratoluenesulfonate, and 0.3 parts by weight of
2,2',4,4'-tetrahydroxybe- nzophenone were dissolved in 90 parts by
weight of methanol was added. The resultant mixture was stirred at
room temperature for 30 minutes, thereby preparing an antifog
coating solution. Then, 12.5 parts by weight of a methanol solution
containing 20 w % of SiO.sub.2 particles was mixed in the antifog
coating solution, and the rate of the inorganic particles with
respect to the concentration of a total solid content was set to be
20 w %.
[0086] The solution thus obtained was applied to a filter of glass
(white plate glass) with a thickness of 1 mm by dip coating, dried,
and cured at 150.degree. C. for 15 minutes, whereby a water
absorption layer (thickness: 4 .mu.m) was formed on both surfaces
of the glass.
[0087] Thereafter, a first solution, in which 7.5 g of titanium
tetraisopropoxide (Ti(O-iso-Pr).sub.4Pr:C.sub.3H.sub.7) is
dissolved in 130 g of isobutyl acetate, was prepared. Then, a
solution, in which 0.50 g of 2-normal HCl and 0.25 g of water are
dissolved in 10 g of i-propanol, was mixed with 100 g of isobutyl
acetate to prepare a second solution. The second solution was added
to the first solution, and the resultant mixture was stirred at
room temperature for 24 hours to set a hydrolysis ratio to be 0.75
to obtain a high refractive layer forming solution. The
above-mentioned water absorption layer was soaked in the high
refractive layer forming solution, pulled up by dip coating at 30
mm/min so as to coat the water absorption layer with the high
refractive layer forming solution, and sintered at 150.degree. C.
for 5 minutes, whereby a first high refractive layer was
formed.
[0088] The antifog coating solution containing the above-mentioned
inorganic particles was diluted with a solution, in which a mixture
containing a water-absorbing polymer and SiO.sub.2 particles at a
weight ratio of 1:1 (50 w %) is mixed with methanol and water at a
ratio of 1:1, to obtain a solution having the viscosity adjusted to
14 cp. The solution thus obtained was applied to the first high
refractive layer by dip coating, and sintered at 150.degree. C. for
5 minutes, thereby adjusting the film thickness to 10 nm.
Furthermore, the water absorption layer was soaked in the high
refractive layer forming solution, pulled up at 30 mm/min by dip
coating, and sintered at 150.degree. C. for 5 minutes to form a
second high refractive layer.
[0089] A top layer was obtained as follows: the antifog coating
solution containing the above-mentioned inorganic particles was
diluted with a solution in which a mixture containing a
water-absorbing polymer and SiO.sub.2 particles at a weight ratio
of 1:1 (50 w %) is mixed with methanol and water at a ratio of 1:1,
to obtain a solution having its viscosity adjusted to 14 cp; the
solution thus obtained was applied to the high refractive layer by
dip coating, and sintered at 150.degree. C. for 15 minutes, thereby
adjusting the film thickness to 130 nm.
[0090] The antifog film produced in Example 4 was evaluated by
Evaluation methods 1 to 4. The results of Evaluation methods 1 and
2 were both that "there is no particular change", as shown in FIGS.
1A and 1B. The results of Evaluation methods 3 and 4 were also both
that "there is no change".
[0091] The reflectance becomes about 0.02 with respect to light in
the vicinity of a wavelength of 500 nm at which the reflectance
becomes the lowest (FIGS. 1A and 1B).
[0092] Furthermore, regarding the morphological stability, an
antifog film (filter) was soaked in water, allowed to stand at a
temperature of 60.degree. C. and a humidity of 90% for 48 hours,
and dried. Thereafter, the surface precision was observed by an
optical interferometer. Consequently, an increase of two neutron
lines was observed as shown in FIGS. 1A and 1B.
[0093] FIGS. 1A and 1B show tables summarizing film compositions,
antifog characteristics, reflection characteristics, and the like
of antifog and antireflection optical elements in Examples 1 to 4
and Comparative Examples 1 to 2.
EXAMPLE 5
[0094] FIG. 2 shows a camera (image pickup apparatus) including an
optical element with the antifog film produced in Example 5. In
FIG. 2, reference numeral 101 denotes a lens (zoom lens) body. The
lens body includes: an image pickup optical system 102 which has
one or a plurality of lens groups inside and is capable of changing
a focal length by moving all or a part of the lens groups; a lens
state detection unit 137 for detecting the focal length (i.e., zoom
state) of the image pickup optical system 2; a driving unit 103 for
adjusting a focal state by moving all or a part of the lens groups
constituting the image pickup optical system 102; a storage means
104 such as a ROM; and a lens control unit 105 for controlling
these components.
[0095] The lens state detection unit 137 detects a movement state
of a lens that moves to change the focal length (zoom state) of the
image pickup optical system 102 and the amount characterizing the
movement state, by a known method, for example by using an
electrode for an encoder provided in a lens-barrel that is rotated
or moved for changing the focal length of the image pickup optical
system 102, a detection electrode that is in contact therewith, and
the like.
[0096] Reference numeral 106 denotes a camera body. The camera body
106 includes a main mirror 107, a focusing glass 108 on which an
object image is formed, a pentaprism 109 for inverting an image,
and an eyepiece 110, which constitute a finder system. The camera
body 106 further includes a sub-mirror 111, a focal point detection
unit 112, an operation unit 113, a camera control unit 114, and a
film as an image-forming medium placed on an image-forming surface
115. Reference numeral 116 denotes a contact point provided in the
lens body 101 and the camera body 106. When the lens body 101 and
the cameral body 106 are mounted, various pieces of information are
communicated and an electric power is supplied via the contact
point 116.
[0097] It is preferable that an optical element with an antifog
film of the present invention is provided in a finder optical
system including the image pickup optical system 102, the
pentaprism 109, and the eyepiece 110, because the fogging of the
optical element can be prevented. In particular, among lenses
(optical components) of the camera, the eyepiece 110 is a lens that
is most frequently physically approached by a person. Therefore,
the eyepiece 110 conventionally suffered from a problem that it is
highly likely to fog. However, by adopting the optical element with
the antifog film of the present invention for the eyepiece 110,
such a problem has been solved.
[0098] Like in the above-mentioned camera, regarding a lens, a
mirror, and the like that a person frequently approaches physically
(i.e., a lens and a mirror exposed to the outside of the
apparatus), by preferably applying the antifog film of the present
example to the surface of the lens and the mirror, that is, by
using the optical element of the present example for the lens,
mirror, and the like that is frequently approached by a person), an
antifog effect as well as an antireflection effect can be obtained.
Therefore, even if a person approaches the lens, mirror, and the
like, the surface of the optical element does not fog, and
reflection and/or transmittance with good efficiency can be
advantageously obtained.
[0099] As described above, it is appreciated that the present
invention is applicable to not only an optical element (e.g., a
lens, a mirror, a prism, a transparent parallel plate, etc.)
provided with the antifog film, but also to optical equipment
provided with the optical element of the present invention, such as
a camera (an image pickup optical system, a finder optical system,
etc.), a liquid crystal projector (an illumination optical system,
a projection optical system, a polarizing plate, a liquid crystal
panel substrate, etc.), and other various optical equipment.
[0100] As described above, according to the present example, it is
possible to realize an optical element having both an antifog
effect and antireflection characteristic as well as morphological
stability, and optical equipment in which moisture condensation or
the like does not occur when incorporating the optical element
therein.
[0101] Various other modifications will be apparent to and can be
readily made by those skilled in the art without departing from the
scope and spirit of this invention. Accordingly, it is not intended
that the scope of the claims appended hereto be limited to the
description as set forth herein, but rather that the claims be
broadly construed.
* * * * *