U.S. patent number 3,895,155 [Application Number 05/336,805] was granted by the patent office on 1975-07-15 for surface protective coating on an article at least surface of which is formed of a synthetic resin.
This patent grant is currently assigned to Nippon Hydron Co. Ltd., Nippon Sheet Glass Co., Ltd.. Invention is credited to Kyoichi Shukuri, Kenzo Sono.
United States Patent |
3,895,155 |
Shukuri , et al. |
July 15, 1975 |
Surface protective coating on an article at least surface of which
is formed of a synthetic resin
Abstract
An inorganic protective coating of a thickness of from 400 A. to
5 microns is applied to a surface of an article at least the
surface of which is formed of a synthetic resin to increase the
surface hardness of the said article without any sacrifice in the
inherent properties of the said article. The protective coating
comprises discrete islets of an inorganic solid each having an area
of at most 7 .times. 10.sup.4 square microns and being firmly
deposited on the synthetic resinous substrate, and being formed by
evaporating an inorganic material through a shadow mask or screen
onto the surface of the said article.
Inventors: |
Shukuri; Kyoichi (Amagasaki,
JA), Sono; Kenzo (Nishinomiya, JA) |
Assignee: |
Nippon Sheet Glass Co., Ltd.
(BOTH OF, JA)
Nippon Hydron Co. Ltd. (BOTH OF, JA)
|
Family
ID: |
27457238 |
Appl.
No.: |
05/336,805 |
Filed: |
February 28, 1973 |
Foreign Application Priority Data
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|
|
|
|
Feb 28, 1972 [JA] |
|
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47-19730 |
Feb 28, 1972 [JA] |
|
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47-19731 |
Apr 11, 1972 [JA] |
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47-35681 |
Jun 26, 1972 [JA] |
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47-63195 |
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Current U.S.
Class: |
428/206;
351/159.57; 427/164; 427/497; 427/593; 428/336; 428/697; 428/702;
351/62; 359/507; 427/165; 427/504; 428/334; 428/696; 428/698 |
Current CPC
Class: |
C23C
14/042 (20130101); Y10T 428/265 (20150115); Y10T
428/24893 (20150115); Y10T 428/263 (20150115) |
Current International
Class: |
C23C
14/04 (20060101); B44d 005/00 (); B32b 003/10 ();
B32b 007/02 () |
Field of
Search: |
;117/37R,38,138.8R,138.8PV,138.8UA,7A,7R,69,72,73,75 ;161/146,71R
;350/61,175 ;351/62,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Martin; William D.
Assistant Examiner: Newsome; John H.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. In an article of which at least the surface is formed of a
synthetic resin, said article having an abrasion and scaling
resistant inorganic film coating of a thickness of from 400A to 5
microns on said surface, the improvement comprising that the
inorganic film is a discontinuous film comprising discrete elements
of such size and spacing that the article retains the abrasion
resistance of a continuous film while avoiding scaling caused by
stresses in a continuous film.
2. The article as defined in claim 1, in which the percentage area
of uncoated areas in the film is from 5 to 99%.
3. The article as defined in claim 1, in which the inorganic film
comprises numerous transparent elements.
4. The article as defined in claim 1 in which each of the discrete
elements is of a transmittance of light of at most 50 %.
5. The article as defined in claim 1 in which each element of the
inorganic film is of a transmittance of light of at most 30%.
6. The article as defined in claim 1 in which each element of
inorganic film consists of multilayers which comprise layers of
transparent substances and/or layers of a transmittance of light of
at most 50%.
7. The article as defined in claim 3 in which the transparent
inorganic film is forced of at least one substance selected from
the group consisting of oxides, nitrides, fluorides and sulfides of
metals.
8. The article as defined in claim 4 in which the inorganic film is
formed of a mixture of at least one substance selected from the
group consisting of silicides, borides, nitrides and carbides and
at least one substance selected from the group consisting of metals
and colored oxides of metals.
9. The article as defined in claim 5 in which the inorganic film is
formed of at least one substance of a transmittance of light of at
most 30% selected from the group consisting of metals and colored
oxides of metals.
10. The article as defined in claim 2 in which elements of the
inorganic film are arranged in a regular pattern.
11. The article as defined in claim 2 in which elements of the
inorganic film are arranged randomly.
12. The article as defined in claim 2 in which the ratio of the
short axis to the long axis of each element of the inorganic film
is from 0.1 to 1.
13. The article as defined in claim 12 in which the shape of each
element of the inorganic film is a circle.
14. The article as defined in claim 12 in which the shape of each
element of the inorganic film is oval or ellipse.
15. The article as defined in claim 12 in which the shape of each
element of the inorganic film is a rectangle.
16. The article as defined in claim 2 in which the synthetic resin
is a hydrophobic polymer.
17. The article as defined in claim 16 in which the percentage area
of uncoated areas is from 5 to 70%.
18. The article as defined in claim 16 in which the area of each
element of the inorganic film is at most 3 .times. 10.sup.4 square
microns.
19. The article as defined in claim 17 in which the hydrophobic
polymer is a member of the group consisting of polycarbonates,
poly(methyl methacrylate), polyvinyl chloride, polystyrene,
polypropylene, polyethylene and unsaturated polyester resins.
20. The article as defined in claim 17 in which the hydrophobic
polymer is a polycarbonate.
21. The article as defined in claim 17 in which the hydrophobic
polymer is poly(methyl methacrylate).
22. The article as defined in claim 17 in which the hydrophobic
polymer is an unsaturated polyester resin.
23. The article as defined in claim 17 comprising a panel for use
as a door.
24. A protective film as defined in claim 17 comprising a sheet for
use in goggles.
25. The article as defined in claim 2 in which the synthetic resin
is a hydrophilic polymer.
26. The article as defined in claim 25 in which the percentage area
of unreacted areas 30 to 99%.
27. The article as defined in claim 25 in which the percentage area
of uncoated areas is 60 to 99%.
28. The article as defined in claim 25 in which the hydrophilic
polymer is a member selected from the group consisting of
hydrophilic acrylic and methacrylic polymers, polyvinyl alcohol,
polyvinyl acetals, polyacrylamides, polyvinyl pyrrolidone,
polyethyleneoxide, polyethyleneimine, hydroxyethylcellulose and
regenerated ceullulose.
29. The article, as defined in claim 25 in which the hydrophilic
polymer is a hydrophilic acrylate or methacrylate polymer.
30. The article as defined in claim 29 in which the hydrophilic
acrylate or methacrylate polymer is a polymer of at least one
hydrophilic acrylate or methacrylate selected from the group
consisting of hydroxy-lower alkyl acrylate, hydroxy-(lower alkyl)
methacrylates, hydroxy-(lower alkoxy-lower alkyl) acrylates and
hydroxy(lower alkoxy-lower alkyl) methacrylates.
31. The article as defined in claim 29 comprising glass coated with
the hydrophilic polymer.
32. The article as defined in claim 29 comprising glass coated with
a hydroxyethyl acrylate or methacrylate polymer.
33. The article as defined in claim 31 comprising an eyeglass
lens.
34. The article as defined in claim 31 comprising a window
glass.
35. The article as defined in claim 31 comprising an automobile
windshield.
36. The article as defined in claim 25 in which the hydrophilic
polymer is polyvinyl alcohol.
37. An article having an abrasion resistant and antifogging surface
comprising a substrate of which at least the surface is formed of a
hydrophilic synthetic resin and a protective discontinuous
inorganic film of a thickness of from 400 A. to 5 microns coated
thereon, said film comprising discrete elements of such size and
spacing that the article retains the abrasion resistance of a
continuous film while presenting a sufficient portion of
hydrophilic surface to the surrounding atmosphere to prevent
fogging by absorbing moisture from the atmosphere.
38. The article of claim 37 having a percentage area of an uncoated
area in the film from 5 to 99%.
39. The article of claim 38 wherein the inorganic film comprises
numerous transparent elements.
40. The article of claim 37 in which each of the inorganic elements
has a transmittance of light of at most 50%.
41. The article of claim 37 in which each element of the inorganic
film has a transmittance of light of at most 30%.
42. The article of claim 37 wherein each element of inorganic film
consists of a multilayer which comprise layers of transparent
substances, layers of a transmittance of light of at most 50% or
mixtures of layers of transparent substances and layers of a
transmittance of light of at most 50%.
43. The article of claim 39 in which the transparent inorganic film
is formed of at least one substance selected from the group
consisting of oxides, nitrides, fluorides and sulfides of
metals.
44. The article of claim 40 in which the inorganic film is formed
of a mixture of at least one substance selected from the group
consisting of silicides, borides, nitrides, and carbides and at
least one substance selected from the group consisting of metals
and colored oxides of metals.
45. The article of claim 41 in which the inorganic film is formed
of at least one substance of a transmittance of light of at most
30% selected from the group consisting of metals and colored oxides
of metals.
46. The article of claim 38 in which the elements of the inorganic
film are arranged in a regular pattern.
47. The article of claim 38 in which the elements of the inorganic
film are arranged randomly.
48. The article of claim 38 in which the ratio of the short axis to
the long axis of each element of the inorganic film is from 0.1 to
1.
49. The article of claim 48 in which the shape of each element of
the inorganic film is a circle.
50. The article of claim 48 in which the shape of each element of
the inorganic film is an oval or ellipse.
51. The article of claim 48 in which the shape of each element of
the inorganic film is a rectangle.
52. The article of claim 38 in which the percentage area of
uncoated area is 30 to 99%.
53. The article of claim 52 in which the percentage area of
uncoated area is 60 to 99%.
54. The article of claim 38 in which the hydrophilic synthetic
resin is a hydrophilic polymer which is a member selected from the
group consisting of hydrophilic acrylic and methacrylic polymers,
polyvinyl alcohol, polyvinyl acetals, polyacrylamides, polyvinyl
pyrrolidone, polyethylene oxide, polyethylenimine, hydroxyethyl
cellulose and regenerated cellulose.
55. The article of claim 38 in which the hydrophilic synthetic
resin is a hydrophilic acrylate or methacrylate polymer.
56. The article of claim 55 in which the hydrophilic acrylate or
methacrylate polymer is a polymer of at least one hydrophilic
acrylate or methacrylate selected from the group consisting of
hydroxy-lower alkyl acrylates, hydroxy lower alkyl methacrylates,
hydroxy lower alkoxy lower alkyl acrylates and hydroxy lower alkoxy
lower alkyl methacrylates.
57. The article of claim 56 in which the hydrophilic acrylate or
methacrylate is hydroxyethyl methacrylate.
58. The article of claim 55 in which the substrate is glass coated
with the hydrophilic synthetic resin.
59. The article of claim 58 comprising an eyeglass lens.
60. The article of claim 58 comprising a window glass.
61. The article of claim 58 comprising an automobile
windshield.
62. The article of claim 38 in which the hydrophilic synthetic
resin is polyvinyl alcohol.
Description
This invention relates to a surface protective coating for shaped
article formed of, at least in their surface portion, synthetic
resins and a method of forming it. In particular, it concerns a
surface protective coating for an article at least a surface of
which is formed of a synthetic resin, particularly of a hydrophilic
polymer, which possesses many desirable characteristics, e.g.
non-fogging property, and increases the surface hardness of the
aforesaid body without sacrifice in inherent desirable physical
properties of the aforesaid article.
Recently, the use of transparent plastics as window glass for
buildings, automobiles, trains or aeroplanes or as doors has been
attempted and in some fields of applications plastic windows or
doors have already been put to practical use. However, the plastic
windows or doors have the drawback of being easy to scratch due to
their poor surface hardness. It has also been attempted to apply a
transparent hydrophilic polymer coating to the surface of an
inorganic window glass of a building, automobile, train or
aeroplane, eyeglasses, goggles or optical lenses to render them
non-fogging through absorption by the coating of water droplets
deposited on their surfaces. However, such coated films of
hydrophilic polymers are easy to scratch even in the dried state as
are ordinary plastics moldings because of poor surface hardness and
this is much more so in the moistened state because a hydrophilic
polymer film is swelled by absorption of water.
It is known to improve the surface hardness of plastic substrates
by application to their surfaces an inorganic protective coating of
a metallic oxide, nitride, fluoride or silicide or other inorganic
solid. However, a continuous film of such an inorganic substance,
even if it has a sufficient initial surface hardness, is cracked or
otherwise injured by internal stress due to difference in the
thermal expansion coefficient between the coating film and the
substrate when put to practical use or subjected to weathering,
boiling, repeated heating and cooling or exposure test. The crack
or other injury results in a decreasing of the surface hardness,
voids in the film and, finally, scaling-off of the film from the
substrate.
At present the problem of the internal stress has been solved at
least partly by applying a protective coating to a substrate heated
to an elevated temperature, by heat treatment in vacuo or in air
treatment just after application of the protective coating to
minimize the internal stress, or by incorporation of one or more
additives in the coating to minimize the difference in thermal
expansion coefficient between the coating and the substrate.
However, it is difficult to eliminate completely the internal
stress by the former method and, in addition, the former method is
inadequate for plastic substrates because of insufficient thermal
resistance of plastic substrates for a sufficient heat treatment.
The latter method has poor practicality because of the necessity of
determining the composition of a coating in each case.
The prior protective coating films are completely continuous
throughout the surface, so that, in the case where the coating
material is opaque, the body coated therewith becomes
non-transmissible. When such an opaque protective coating is
applied to a body consisting of a glass substrate having thereon a
coating layer of a hydrophilic polymer, the body loses its photo
transmissibility and, in addition, the aforesaid hydrophilic
polymer layer cannot exhibit its defogging effect since it is
completely isolated from the air by the continuous protective
coating film.
Accordingly, it is an object of the present invention to provide an
improved protective coating film for an article at least the
surface of which is formed of synthetic resins.
It is another object of the present invention to provide a
protective coating film for a transparent synthetic resin article
which has substantially no adverse effect on the photo
transmissibility of the article.
It is a further object of the present invention to provide a
non-fogging protective coating film for an article of which at
least the surface is formed of a hydrophilic polymer.
It is a still further object of the present invention to provide a
method of enhancing the surface hardness of shaped bodies having a
relatively poor surface hardness.
It is a separate object of the present invention to provide a
surface protective coating film having a reduced haze.
In accordance with the present invention, these objects are
accomplished by an inorganic protective coating film of a thickness
of from 400 angstroms to 5 microns comprising discrete islets of an
inorganic solid each having an area of 7 .times. 10.sup.4 square
microns or less leaving openings therebetween interconnecting the
surface of an article to the air.
Thus, to the surface of a synthetic resin article having a poor
surface hardness there is applied an inorganic film having a
sufficient hardness consisting of discrete islets leaving
therebetween uniformly distributed openings interconnecting with
the air, so that the surface hardness of the aforesaid body is
enhanced without sacrifice in the inherent properties of the body,
such as transparency and the hydrophilic property and there is no
risk of scaling-off of the coating film.
The invention will be readily understood from the following
description, when read together with the accompanying drawings,
wherein;
FIG. 1 is a curve indicating the relationship between the
anti-fogging property and the percentage of opening area of a
protective coating film in accordance with the present invention
formed on the surface of a hydrophilic plastics body,
FIG. 2 to 4 are cross-sectional views of coated articles indicating
the principle of development and reduction of haze,
FIG. 5 is an enlarged cross-sectional view of an article having a
protective coating film in accordance with the present
invention,
FIG. 6 is a plan view of the aforesaid article,
FIG. 7 is a curve indicating the change of quantity of transmitted
light through a specimen of a sheet of a hydrophilic resin having
no protective coating film determined by continuously supplying
steam onto the specimen and then stopping the supply,
FIG. 8 is a curve indicating the similar change in the quantity of
transmitted light obtained on a specimen having a protective
coating film in accordance with the present invention,
FIG. 9 is a diagonal view of a specimen having a protective coating
of the present invention consisting of regularly arranged circular
elements, indicating the anisotropy in abrasion hardness,
FIGS. 10(a) and 10(b) show an example of formation of a pattern on
a shadow mask to be employed in the practice of the method of the
present invention,
FIG. 11 is a microscopic photograph indicating an example of an
evaporating mask or shadow mask,
FIG. 12 is a rough sketch of an apparatus for determination of the
anti-fogging property, and
FIGS. 13 to 15 show examples of patterns on the masks for use in
the formation of the protective coating film in accordance with the
present invention.
The shaped article to which a protective coating is applied in
accordance with the present invention may be formed of any
hydrophilic and hydrophobic polymer. The hydrophobic polymers
includes, e.g., polycarbonates, poly(methyl methacrylate),
polyvinyl chloride, polystyrene, polypropylene, polyethylene and
unsaturated polyester resins. The hydrophilic polymers includes,
e.g., hydrophilic acrylate and methacrylate polymers, polyvinyl
alcohol, polyvinyl acetal, polyacrylamides, polyvinylpyrrolidone,
poly(ethylene oxide), poly(ethylene imine), hydroxyethylcellulose
and regenerated cellulose. These materials may form shaped bodies
by themselves or form the surfaces of shaped bodies of other
plastics, glass, metal, wood, concrete or porcelain. As the
hydrophilic polymer there are preferably used water-insoluble,
hydrophilic acrylate and methacrylate polymers.
The hydrophilic acrylate and methacrylate polymers are exemplified
by, e.g., polymers of hydroxy-lower alkyl acrylates, hydroxy-lower
alkyl methacrylates, hydroxy-lower alkoxy-lower alkyl acrylates and
hydroxy-lower alkoxy-lower alkyl methacrylates, such as of
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
diethyleneglycol monoacrylate, diethyleneglycol monomethacrylate,
triethyleneglycol monoacrylate, triethyleneglycol monomethacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate,
dipropyleneglycol monoacrylate and dipropyleneglycol
methacrylate.
The aforesaid polymer may be crosslinked, if necessary, by
copolymerization of 0.05 to 20, preferably 0.1 to 2.5 % of a
crosslinking agent, such as, e.g., ethyleneglycol diacrylate,
ethyleneglycol dimethacrylate, propyleneglycol diacrylate,
propyleneglycol dimethacrylate, divinylbenzenes and
N,N'-methylene-bis-acrylamide.
The aforesaid polymer may be modified, if necessary, by
copolymerization with, e.g., acrylic acid, methacrylic acid,
itaconic acid, fumaric acid or mono-2-hydroxypropyl itaconate.
As the polyvinyl alcohol there may be used partially saponified
polyvinyl acetate other than the complete saponification product.
The polyvinyl acetals includes polyvinyl formal, polyvinyl
acetoacetal, and polyvinyl butyral. The polyacrylamides includes
polymers of acrylamide, methacrylamide, N-methylol acrylamide,
N-methylol methacrylamide, diacetone acrylamide, diacetone
methacrylamide and like acrylamide and methacrylamide
derivatives.
The protective coating film in accordance with the present
invention formed on a hydrophilic polymer body combines the effect
of enhancing surface hardness and the advantages that there is no
fear of scaling-off and it is air permeable and photo
transmissible. Namely, the protective coating film of the present
invention on an article of which at least the surface is formed of
a hydrophilic polymer has a structure comprising discrete dots or
stripes or otherwise figured islands of an inorganic solid and
openings or interstices therebetween interconnecting the surface of
the substrate with the air; this structure prevents the scaling-off
of the protective coating film and deformation of the film by
thermal stress and allows gaseous molecules to reach the surface of
the hydrophilic polymer body. The discrete structure should be of a
pitch smaller than the diameter of fibers of the cloth to be used
for cleaning the surface or of abrasive grains. This structure is
obtainable by forming an inorganic protective coating film through
a sheet of perforated mask or combination of several sheets of
perforated mask on the surface of a shaped body of which at least
the surface is formed of a plastic by an evaporating method, such
as, e.g., resistance heating method, electron beam method or
sputtering method.
In the resistance heating method, a material to be evaporated is
heated by Joule's heat generated by application of an intensive
electric current to a wire or foil of a high melting point and the
bond between the protective coating and the substrate is
attributable mainly to physical adsorption and van der Waals
forces. In this case, since the bonding strength is not
sufficiently high, it is desirable to preheat the substrate prior
to evaporation or activate it by means of ion bombardment to
enhance adhesion.
In the electron beam method, the material is heated by collision of
a beam of a large number of electrons accelerated to a high speed.
In the sputtering method, the material is bombarded by cations
generated by glow discharge, low pressure glow discharge in a
magnetic field or high frequency electric field, low pressure
plasma, ion beam or like physical or chemical sputtering means. In
the electron beam method and sputtering method, particles of a
metal or metal oxide shot out of a target have a very high level of
energy (10 - 100 eV) compared with particles evaporated in the
resistance heating method (about 0.2 eV), so that they locally heat
the surface of the substrate and form a substantially complete
chemical bond with the surface.
Therefore, through depending on the melting point and decomposition
point of the material being used, in general it is preferred to
process a material of a low melting point in the resistance heating
method and a material of a high melting point in the electron beam
or sputtering method. In all cases, however, the temperature of the
substrate should carefully be controlled to prevent the substrate
from thermal decomposition. A fairly strong bond between the
substrate and protective coating is attained by cleaning the
surface of the substrate by ion bombardment. This is believed to be
attributable to formation of oxygen linkages on the polymer
molecules.
The protective coating film may be formed by a chemical method
other than the above mentioned physical methods.
A protective coating film of a desired percentage area of openings
or interstices and a desired pattern of stripes or islands is made
by use of a mask consisting of one or several sheets of a masking
sheet having numerous through-holes having a desired contour or
numerous slits. The contour of through-holes or stripes and their
arrangement are not critical. It may be of discrete islands or
stripes and arranged regularly or at random. The area of each
preferably is 7 .times. 10.sup.4 square microns, or less, more
desirably 3 .times. 10.sup.4 square microns or less, because if it
exceeds 3 .times. 10.sup.4 square microns transmitted light becomes
nonuniform and there occasionally occurs fluctuation of transmitted
light and the coating film becomes fragile. In particular in case
of hydrophilic polymer bodies, it is preferred the area to be 8
.times. 10.sup.3 square microns or less from the point of view of
non-fogging and hygroscopicity. The thickness of the aforesaid
coating consisting of numerous discrete islands preferably is 400
angstroms to 5 microns, because a film of a thickness of less than
400 angstroms does not have sufficient function and, on the other
hand, one of a thickness exceeding 5 microns has a haze and is poor
in adhesion to the substrate.
The shape or contour of each element of the protective coating film
may be circle, oval or stripe, though it is preferred that the
ratio of its short axis to its long axis ranges between 0.1 and
1.0.
It is preferred that openings or interstices between islands or
stripes be uniformly distributed throughout the surface to be
protected. The percentage area of openings may be varied depending
on desire, though normally is 5 to 99 %. In case of a hydrophilic
polymer body, a percentage area of openings of 30 to 99 % is
preferred to attain the object of surface protection without
sacrifice in the desirable properties of the body, and, in case of
a hydrophobic polymer body, a range from 5 % to 70 % is preferred
because, in the latter case, the protective coating is applied for
the purpose of surface protection only.
The term "percentage area of openings" means the percentage of an
area obtained by subtracting the total area of islands from the
total area of the substrate covered by the protective coating.
Usually, for instance, it is represented by the following equation
in the case of a two-dimensional zig-zag pattern,
S (%) = (1 - 2.pi.r.sup.2 / 3 1.sup.2) .times. 100
where S is the percentage area of openings, r is the diameter of an
island and l is the average distance between two adjacent
islands.
As the result of more detailed experiments, we have found that, in
case of hydrophilic polymer bodies, the anti-fogging property takes
its highest value when the percentage area of openings is in the
range of from 60 to 99 %.
In theoretical point of view, it is believed that, when the
aforesaid protective coating film is applied to the surface of a
hydrophilic polymer, the anti-fogging property deteriorates as the
total area of the islands increases, in other words, the percentage
area of openings decreases, whereas, surprisingly, it has been
found that, as the result of experiments as indicated by FIG. 1, a
coated body having a protective coating film of a percentage area
of opening of 60 to 99 % is superior in anti-fogging property to
one of a percentage area of opening of 100 % (a body having no
protective coating film). The hump of the curve in FIG. 1 indicates
this. The curve in FIG. 1 is obtained by plotting the anti-fogging
property T/T.sub.o vs. the percentage area of openings, as
determined by the method as set forth hereinafter on coated bodies
prepared by evaporating silicon oxide through various masks on to
substrates to form thereon a protective coating film of a thickness
of 1,000 to 1,500 angstroms. The percentage area of openings is
determined by measuring the total area of islands by microscopic
photography, since the pattern of the protective film is not always
identical with that of the mask used because of imperfect contact
between the surface of the substrate and the mask.
Thus, the present invention is based on the discovery contrary to
the ordinary idea that an uncoated hydrophilic plastic body is
superior in non-fogging property to an at least partially coated
one. While the exact mechanism is uncertain, it is believed that
diffusion of water deposited on the surface into the inside of the
hydrophilic plastic body is delayed by the porous protective
coating film and this delay results in an enhancement of the
anti-fogging property.
In the practice of the present invention there may be used various
inorganic substances in the formation of a protective coating film,
and for the formation of a transparent protective coating film
there are used oxides, nitrides, fluorides and sulfides of various
metals. The material may be applied to a substrate in an
appropriate process according to the material used.
For example, the material suitably applied in the resistance
heating method includes, e.g., tin oxide, cadmium oxide, indium
oxide, zinc oxide, bismuth oxide, antimony oxide, silicon monoxide,
cadmium sulfide, zinc sulfide, magnesium fluoride, beryllium
fluoride, calcium fluoride, lithium fluoride, sodium fluoride,
thulium fluoride, cerium fluoride and cryolite.
The material suitably applied in the electron beam or sputtering
method includes, e.g, thorium oxide, beryllium oxide, calcium
oxide, strontium oxide, barium oxide, aluminum oxide, magnesium
oxide zirconium oxide, cerium oxide, silica, niobium oxide,
titanium oxide, tantalum oxide, lanthanum oxide, hafnium oxide,
niobium nitride, boron nitride, aluminum nitride and silicon
nitride.
Both transparent and opaque materials are employed in accordance
with the object to form a protective coating film of the present
invention, but when a transparent protective coating film is formed
on a transparent substrate, there is sometimes observed the
phenomenon of becoming cloudy due to scattering of light, so called
haze. It is desired to avoid development of haze in the case
especially of lenses. The haze is attributable to scattering of
light at the periphery of or center of each element or island of a
protective coating film.
Referring to FIG. 2, discrete elements or islands 2 are fixed to
the surface of a substrate 1 having a relatively low surface
hardness. In rays P incident upon the body, rays P.sub.2 and
P.sub.4 go right on after passed through the body and arrive at
Q.sub.2 and Q.sub.4, respectively, namely unscattered and
developing no haze, while rays P.sub.1 and P.sub.3 arrive at
Q.sub.1 and Q.sub.3, respectively, since they are refracted on the
surface of the body. This is a reason for the development of haze
in the transmitted rays. This results in the drawback that the
visibility through the body is hindered somewhat though the surface
hardness of the body is enhanced to a great extent by application
of a discrete protective coating film thereto which is free from
cracking and scaling-off.
As the result of further investigations, we have discovered that
these drawbacks are eliminated by the following means.
In accordance with the present invention, haze is minimized by use
as the coating material of an inorganic solid having a high
hardness and a relatively low transparency, by first applying a
discrete coating film of an inorganic solid having a high
transparency and a high adhesion to a substrate and applying
thereover a solid having a relatively low transparency or by use of
a blend of such high transparent and low transparent solids.
Illustrating in more detail, for instance, hitherto there has been
used for forming a protective coating film silicon dioxide
SiO.sub.2 as a material having high transparency and hardness and
excellent adhesion to a plastic substrate. In accordance with the
present invention, haze is minimized to a great extent by applying
a mixture of a small amount of a metal and SiO.sub.2 or by applying
a material having a low transmittance, such as, e.g., metallic
aluminum, chromium or like material, over a coating of SiO.sub.2 so
as to reduce transmittance.
Namely, the present invention is characterized by reducing the
quantity of transmitted light thereby to reduce the quantity of
scattered light causing the haze by reducing the transmittance of
the discrete protective coating film applied to a substrate so as
to enhance surface hardness.
Illustrating the present invention referring to FIG. 3 and 4, to a
substrate 1 to be protected there are applied elements 2 of a
protective coating film consisting of a material having a low
transmittance. The quantities of rays of light P.sub.1, P.sub.2 and
P.sub.3 arrived at Q.sub.1, Q.sub.2 and Q.sub.3 are reduced or
minimized to zero by the element, so that rays P.sub.4 predominate
in transmitted light through the body whereby haze is minimized to
a great extent. In the embodiment as illustrated by FIG. 4, to a
substrate 1 there is applied a transparent material 3 and thereover
a opaque material 4 to form elements 2 of a protective coating
film. In this case, in incident rays P.sub.1 to P.sub.4, rays
P.sub.4 only pass through the body whereby haze is reduced to a
great extent.
That is to say, the present invention intends to minimize haze by
cutting off scattered light and allowing straight-forward light
only to pass the body, so that the order of the transparent
material 3 and opaque material 4 in FIG. 4 may be reversed, and the
same result can be obtained by applying the opaque material
annularly only to the peripheral section of each element or island
of the transparent material. It is necessary for eliminating haze
by minimizing or eliminating scattered light to reduce the
transmittance of each element to 50 % or less, preferably to 30 %
or less.
In the practice of the present invention there may be used the
various transparent materials mentioned above for forming elements
of a protective film and, on the other hand, there may be used as
the opaque material to be used in combination with the transparent
material, materials such as chromium, nickel, aluminum, gold,
silver, tantalum, titanium or like metals; iron oxides, chromium
oxide, cobalt oxide and like colored metallic oxides; and niobium
nitride, chromium nitride, titanium nitride and like nitrides and
carbides, silicides, fluorides and like so called refractories.
In the present invention, the protected areas of the surface of a
substrate increase as the density of elements or islets scattered
as to form a protective coating layer increase, while, on the other
hand, the percentage area of openings on the substrate decreases to
hinder the inherent desirable properties of the substrate, such as,
e.g., hygroscopicity and the anti-fogging property in case of a
hydrophilic resin. The present invention is of great value for
enhancing the surface hardness of a shaped body of a hydrophilic
plastic having insufficient surface hardness, so that the present
invention will be illustrated hereinafter in more detail with
respect to such a substrate, but, of course, the present invention
to applicable to any substrate in principle.
As shown in FIGS. 5 and 6, when each element or islet 7 formed on a
substrate 5 and a coating layer 6 of a hydrophilic resin has a
large area, there are formed water droplets 8 on the surface of
each element due to lack of hygroscopicity of the protective
coating itself to yield local fog upon exposure to steam or water
vapour. To avoid this phenomenon it is desirable that each element
has as small an area as possible. This is true of dehumidification
of a hydrophilic plastic body after absorption of water. Namely,
water 10 absorbed by plastic 9 just under an element 7 of a
protective coating film must diffuse in the plastic layer to the
naked section 11 to vaporize into the air. On this occasion, it is
desirable for quick vaporizing of moisture that the area of each
element 7 is as small as possible, because if moisture absorbed by
the plastic just under an element 7 stays there indefinitely the
element gives a faulty dehumidification response. The
dehumidification response will be illustrated in detail with
reference to FIG. 7.
FIG. 7 shows the change in quantity of light transmitted through a
specimen of a hydrophilic or hygroscopic plastic layer having no
protective coating film thereon determined by supplying steam at a
constant flow rate thereto and continuing measurement after stop of
the supply of steam. A laser beam is directed at a point of the
surface of the plastic layer while supplying thereto steam. In the
initial stage of supply of steam, the transmittance of the plastic
layer for the laser beam passing straight through the specimen is
not varied at all because of adsorption of steam by the hygroscopic
resin. During continuous supply of steam for a long time, the resin
is saturated with moisture, annd thereafter there occurs
condensation of a portion of the steam on the surface to form water
droplets which cause fog. With progress of the condensation of
steam, the quantity of light received by a light detector located
on the optical axis of the laser beam is gradually decreased by
scattering with the water droplets. In FIG. 7 the quantity of
transmitted light arrived at the receiver is plotted as ordinate
and the time of supply of steam as abscissa. In the graph, from
point A to B there is no change in the quantity of transmitted
light as steam is absorbed by the specimen so as not to form any
water droplets thereon, while from point B to C the quantity
decreases abruptly because of formation of fog on the surface,
after the resin being saturated by moisture. When the supply of
steam is stopped at point C, the quantity increases gradually
thereafter because of evaporation of the water dloplets into the
air and the specimen reverts to the original transparent state at
point D. The time elapsed from the point A and B is the value
indicating the anti-fogging quality or property and the value
represented by the time elapsed between the point C and D indicates
dehumidifaction response.
In case of a specimen prepared by evaporating silicon dioxide onto
a hydrophilic polymer sheet through a stainless steel mask having
numerous circular through holes each of 100 microns .phi. at
pitches of 200 microns to form a coating of a thickness of 200
angstroms consisting of discrete circular elements each of a
diameter of about 100 microns, the quantity of transmitted light
varies as indicated by the curve a (full line), in FIG. 8 (The
symbol .phi. is used here and throughout the specification as the
standard abbreviation of "diameter.") That is to say, the quantity
somewhat decreases at point Q and reverts to point R and fog is
formed as it decreases from point R to S. When application of steam
is stopped at the point S, the transparency of the specimen reverts
through point T to its original value. In this case, the decrease
at the point Q corresponds to scattering of light caused by water
droplets condensed on each elements of the protective coating and
the reversion to R corresponds to formation of a transparent film
of water resulting from condensation of a sufficient quantity of
moisture. On the other hand, the reversion of the quantity of
transmitted light after the stopping of application of steam takes
a longer time than in case of an uncoated specimen and the quantity
of light at the point T is smaller than that at the point D in FIG.
7. This seems, since the rate of application of steam is identical
in both cases, to be attributable to difficulty in the escape of
the moisture absorbed by the specimen just under the elements, the
dehumidification response being not sufficiently high.
The curve b (dotted line) in FIG. 8, on the other hand, is one
obtained on a specimen having a protective coating consisting of
elements in accordance with the present invention in which each
element has dimensions of 157 microns .times. 50 microns (equal in
area to the aforesaid circular element of 100 microns .phi.) and
the density of the elements is equal to that in the aforesaid
specimen having circular elements. In this case, the decrease in
quantity of transmitted light at point U is smaller than that at
point Q and reversion point V takes mean time and quantity of
transmitted light of those of the point T on the curve a and of the
point D in FIG. 3. It is believed to be a reason why the quantity
of transmitted light at the point V is larger than that at the
point T on the curve a and the time to V is shorter than that to T
that the average distance which the moisture just below each
element passes through until it reaches uncoated areas or openings
is shorter resulting in a high dehumidification response. From this
newly found fact, it will be concluded that, in enhancing the
surface hardness of a surface of a hydrophilic plastic object by
application of a protective coating consisting of numerous
uniformly distributed discrete elements, the shape or contour of
each element should be, if its area is fixed, other than
circle.
Illustrating the abrasion resistance of a specimen having a
protective coating in which elements are arranged in a pattern with
a simple regularity, in FIG. 9 there is shown a pattern of a
diagonal arrangement of elements. Numeral 12 indicates openings or
interstices where the surface of a hydrophilic plastic is directly
exposed to the air and 13 indicates elements of a protective
coating. In this case, the coating film has sufficient hardness
against abrasion in the direction of line l.sub.1 since an abrasive
passes over a number of hard protective elements, but in the
direction of line l.sub.2 and of l.sub.3 it is easy to scratch
since an abrasive passes over openings only. Thus, there is
observed anisotropy in abrasion resistance with respect to patterns
adopted. For assuring a sufficient abrasion resistance it is
necessary to take notice of the pattern of rearrangement of
elements.
The first rule is to arrange protective elements at random.
However, in practical aspect, it is difficult to make a mask having
a completely random pattern, so that it is reasonable to make a
mask by providing a number of unit patterns having one or few
elements in a unit pattern, assembling a plurality of the unit
patterns to form a block pattern and assembling a plurality of the
block patterns in a regular arrangement. In this case, it is
necessary to design the arrangement of the unit patterns and/or the
elements that the elements may not be arranged with a simple
regularity in the unit patterns and/or the block patterns. For
instance, a hexagon as shown in FIG. 10(a) is regarded as a unit
pattern in which few protective elements are arranged at random,
and the unit pattern is turned around Z axis, perpendicular to the
plane of the paper by 60.degree., five times to form a block
pattern as shown in FIG. 10(b) in which elements are also arranged
at random. A mask is made in a simple way by two dimensionally
extending the block pattern by reversion, parallel movement or
other transposition means, in which, in the finished mask, elements
are arranged substantially randomly.
As will be understood from the above description, it also is an
object of the present invention to provide a shape or contour of
the protective element of a protective coating film and a pattern
of arrangement of through-holes in a mask for use in the
preparation of the protective coating film which (1) has not
adverse effect on the inherent desirable characteristics of the
substrate, such as, e.g., hygroscopicity and non-fogging quality,
(2) enhances the moisture absorbing-and-desorbing response of a
hygroscopic plastic and (3) has no anisotropy in abrasion.
Namely, the protecting method for enhancing the surface hardness of
an object in accordance with the present invention is attained by
studding randomly numerous fine, elongated or ellipse islets of an
inorganic solid on a surface of a plastic, especially a
hydrophilic, hygroscopic plastic substrate to form a coating layer
having openings interconnecting the said surface with the air. A
good result is obtainable by carrying out this using a mask formed
of a plurality of block patterns in the manner as fully mentioned
above.
Illustrating the preparation of the coating film in the method of
the present invention in more detail, the percentage area of
openings is appropriately chosen for providing a sufficient area of
opening for the substrate resin as not to inhibit hygroscopicity
and non-fogging quality, i.e. 40 % or more, preferably 70 % or
more. For ensuring a high moisture absorption-and-desorption
response and a high abrasion resistance, the element of protective
coating layer must be of an elongated or elliptical form. And, for
minimizing the isotropicity in abrasion resistance of a protective
coating film, i.e., preventing the substrate being scratched or
injured even if being rubbed in any direction, the elements are
arranged randomly, i.e., arranged in a randomized pattern. Namely,
the present invention is characterized by designing a pattern of a
mask on the basis of the three fundamental rules as mentioned above
as to ensure a sufficient enhancement of the surface hardness of an
object.
An example of a pattern designed on these fundamental rules is
shown in FIG. 11. First there is provided a hexagonal unit pattern
of which the length of a side is 124 microns, the unit pattern
having randomly arranged four through holes each consisting of a
square of a side length of 15 microns and two hemi-circles of a
diameter of 15 microns positioned on the opposite sides of the
square, as shown in FIG. 10(a). The percentage area of openings for
the substrate of the unit pattern is 96 %. The unit pattern is
rotated five times by 60.degree. to form a block pattern as shown
in FIG. 10(b). A mask is formed by arranging alternately the block
pattern and its mirror image. In FIG. 11 there is shown a
microscopic photograph of a portion of a random pattern in the mask
(direct magnification 400 .times. enlarging magnification 3). Thus,
in this way, there is obtained with ease an evaporating mask with a
random pattern which will provide an evaporation coating film
having no isotropy in abrasion resistance.
As set forth above, it is very difficult for grains or particles of
an abrasive to get into the openings between the islets or elements
of a protective coating and, if got thereinto, it is rare that
grains of an abrasive gotten into the openings are dragged over a
long distance by fibers of an abrasive cloth to scratch the surface
of a substrate since the islets or elements of the protective
coating are dotted at very fine pitches on a plastic substrate,
especially a hydrophilic plastic substrate. In fact, it is
ascertained that a shaped body, especially of a hydrophilic
plastic, thus applied with such a coating film has a highly
enhanced surface hardness, is put to practical use without any
trouble. When a specimen of a coated plastic body of the present
invention was rubbed under a more severe rubbing than in practical
use to injure the surface of the substrate for a test, it was
ascertained by microscopic observation that only the surface of the
protective coating film was injured and the surface of the
substrate was not injured. This means that by the discrete coating
film applied to the surface of a substrate defines the surface
hardness of a coated object as a whole.
On the other hand, it is believed that since a protective coating
film in accordance with the present invention is divided into
numerous discrete islets or elements there occurs no local
convergence of internal stress to cause destruction of the coating
film, so that the protective coating film is prevented from
breakage and scaling-off.
The discrete structure of the protective coating film in accordance
with the present invention allows the surface of the substrate to
directly contact the air and, accordingly, penetration into and
evaporation from the surface of moisture. In other words, the
protective coating film makes it possible to enhance the surface
hardness of a plastic body, especially of a hydrophilic plastic
body without sacrifice in its inherent properties, such as, e.g.,
hygroscopicity. A hydrophilic polymer layer is injured or deformed
by lightly wiping it with a cloth when fully swollen by water as a
result of absorption of moisture contained in the air, but the
surface hardness of such a hydrophilic polymer layer is enhanced to
a great extent without any sacrifice in its hygroscopicity by
applying thereto a discrete protective coating film in accordance
with the present invention.
In addition, the protective coating film allows free passage
therethrough of light because it has openings uniformly distributed
throughout its surface. Accordingly, in the case where an opaque
protective film is applied to a transparent substrate, the
transparency of the substrate is substantially not hindered and the
substrate can exhibit its inherent photo transmitting quality.
Thus, in accordance with the present invention, there is obtained a
protective coating film which is free from scaling-off and
enhancement of the surface hardness of a substrate without
sacrifice of the inherent transparency and hygroscopicity of the
substrate firmly bonded to the surface of building, automobile,
train and aeroplane windows, doors, eyeglasses, goggles, optical
lenses, sheet glasses for water tanks and mirrors made out of a
plastic or made out of a glass or plastic coated with a hydrophilic
plastic layer. Similar results are obtained by applying a
protective coating film in accordance with the present invention
to, e.g., window sashes, walls, concrete blocks, hulls and
submarine structures.
The embodiments of the present invention will hereinafter be
illustrated in more detail by the following examples.
The test methods as used in the examples are as follows:
Determination of non-fogging quality
Water 15 contained in a two-necked flask, 14, as shown in FIG. 12,
is heated at (40.degree. .+-. 0.5).degree.C by means of a mantle
heater 16 and air at normal temperature is blown thereinto through
a flow meter (not shown) at a rate of 1,000 ml/min to generate
steam. The steam is introduced through a cock 18 into a thermally
insulated T-pipe 19 one end of which has a through-hole 20 of a
diameter of 10 mm and the other end has a through-hole 21 of a
diameter of 3 mm. On front of the through-hole 20 there is set a
specimen 22 at an interval of 2 mm for escape of steam.
A beam of light emitted from a He-Ne gas laser 23 (6328 A., 1.0mW)
passes through a slit 24, a lens 25, a through-hole 21, a
through-hole 20, (the diameter of the beam is so adjusted that its
diameter at the through-hole 20 is 10 mm), the specimen 22 and an
iris 26 for eliminating scattered light and arrives at a photo cell
27 to yield an electric power. The electric power is read as
voltage by means of a millivolt-meter 28.
First, the transmittance of the specimen before application to the
specimen of steam in the state where the cock 18 is closed is
determined. The measurement of the length of time is started
concurrently with opening of the cock 18 and the length of time
until the reading of the millivoltmeter reaches a value
corresponding to a 10 % decrease of transmittance caused by
deposition of water droplets on the surface of the specimen is
determined. The specimen is, prior to the test, dehydrated by
heating at 80.degree.C for 30 minutes and cooled to room
temperature in a desiccator. The relationship between the
transmittance and the reading of the millivoltmeter employed in
this method was determined by a calibration curve formed by
measuring the transmittances and electromotive forces (milli-volts)
in accordance with this test method on sheet glasses having
different transmittances prepared by grinding separate pieces of a
sheet glass with abrasives of different grain sizes for different
grinding times.
Abrasion test
In Examples 4 to 9, a commercially available gauze is reciprocated
under the load of 2 kg/cm.sup.2 on a surface of a specimen until
noticiable scratches are formed thereon, and the number of
reciprocating cycles is counted.
In Examples 10 to 14, an uncoated specimen is rubbed at the
intensity at which eyeglasses are usually wiped with a commercially
available silicone cloth (Celite) or gauze. On this occasion, the
view through the specimen is noticiably damaged when the specimen
is rubbed about 400 cycles by the Celite or about 100 cycles by the
gauze. The so rubbed uncoated specimen is regarded as a marginal
specimen, and the abrasion resistance of a coated specimen is
indicated by the number of rubbing cycles by rubbing the specimen
with the Celite or gauze until it is scratched on average to the
same extent with the marginal specimen.
Determination of thickness of film
The thickness of a protective coating film is determined by means
of Talysurf (Taylor-Hobson Co.).
EXAMPLE 1
Two polycarbonate plates of 50 mm .times. 50 mm .times. 3 mm were
cleaned in an ultrasonic cleaning process and one of them was, as
it was, and the other was, after being covered by a stainless steel
mask having numerous circular holes of 300 microns .phi. arranged
in a pattern as shown in FIG. 9 at a pitch of 500 microns, put in a
vacuum evaporation apparatus. The vacuum chamber was evacuated to 1
.times. 10.sup..sup.-6 Torr and silicon dioxide was evaporated on
to the plates while heating the plates at about 100.degree.C, in an
electron beam evaporation process (accelerating voltage of 4 KV,
beam current of 30 mA, evaporation time of 10 minutes and distance
between the silicon dioxide source and the substrate of 120 mm) to
form a uniform coating on the unmasked plate (B) and a discrete
coating on the masked plate (C), both coating films being of a
thickness of about 5 microns. The percentage area of openings of
the coating film on (C) was 50 % and the transparency of the coated
plate (C) was substantially identical with that of the plate (B).
There was also provided an uncoated polycarbonate plate (A).
The surface of the specimens A, B and C were lightly brushed by
means of a wire brush consisting of a bundle of 30 copper wires of
0.2 mm .phi. to estimate their surface hardness. There were
observed few scratches on the surface of specimen A after two or
three touches, but on the surface of specimens B and C there was
observed no scratch even after brushing of 100 times or more.
When specimens B and C were immersed in boiling water at
100.degree.C, there occurred scaling-off of the protective coating
film on specimen B after 30 minutes to 1 hour and the protective
coating film almost disappeared after 11/2 hours, while on specimen
C there was observed no change even after boiling test for 3
hours.
EXAMPLE 2
Two poly(methyl methacrylate) plates were cleaned in an ultrasonic
cleaning process and one of them was, at it was, and the other was,
after being covered by a mask as shown in FIG. 13 consisting of two
stainless steel masks each having circular hole 3 of 300 microns
.phi. arranged in a pattern as shown in FIG. 9 at a pitch of 500
microns, said two masks being combined together at an angle of
45.degree.. Each of the poly(methyl methacrylate) plates was then
mounted on a specimen holder provided with a water cooling means in
an RF sputtering apparatus. Since there was a risk of the plate
being exposed to plasma and thermally decomposed, a vacuum grease
was applied to the back of the plate so as to enhance thermal
contact between the plate and the holder. To the cathode in the RF
sputtering apparatus there was mounted a sintered plate of cerium
oxide (CeO.sub.2), the vacuum chamber was then evacuated to 1
.times. 10.sup..sup.-5 Torr and thereafter dried gaseous argon was
introduced thereinto to adjust the inner pressure to 3 .times.
10.sup..sup.-3 Torr.
Sputtering was then carried out for 5 minutes at a RF voltage of
2.5 KV and plate current of 240 mA imposing a voltage from an 1 KW
RF electric generator to deposite a CeO.sub.2 film of a thickness
of about 1,000 A. on the poly(methyl methacrylate) plate. Thus,
there was formed a uniform film on the unmasked plate (B) and a
discrete film having a moire pattern on the masked plate (C). The
percentage area of openings of the protective film on the plate (C)
was 65 % and the coated plate (C) was not different in transparency
from the coated plate (B). There was also provided an uncoated
poly(methyl methacrylate) plate (A).
The specimens A, B and C were subjected to the surface hardness
test using a wire brush as in Example 1. Specimen A was injured by
light brushing touches of only two or three times, while specimens
C and B were scratched scarcely even if brushed 100 times or more.
When specimens B and C were subjected to the boiling test as in
Example 1, there occurred scaling-off of protective film on the
specimen B after boiling for 20 to 30 minutes, while there was
observed no change on specimen C even after boiling for 1 hour.
EXAMPLE 3
Two cast plates of an unsaturated polyester resin each of 50 mm
.times. 50 mm .times. 3 mm were cleaned in an ultrasonic cleaning
process, and one of them was, as it was, and the other was, after
being covered by a stainless steel mask having a pattern as shown
in FIG. 14 consisting of three stainless steel masks each having
circular holes of 300 microns .phi. arranged in a pattern as shown
in FIG. 9 at a pitch of 500 microns, the three unit masks being
stacked one over another at angles of 22.5.degree. and 45.degree.,
mounted in a vacuum chamber. In a molybdenum boat positioned below
the plate in the vacuum chamber there was charged stannic oxide
(SnO.sub.2). The chamber was evacuated to 2 .times. 10.sup..sup.-5
Torr and an electric current was applied to the molybdenum boat to
evaporate SnO.sub.2 on to the plate in a thickness of about 2,000
A. Thus, there was formed a uniform coating on the unmasked cast
plate (B) and a discrete coating of a pattern as shown in FIG. 14
on the masked plate (C). The percentage area of opening of specimen
C was 75 % and there was no difference in transparency between
specimens B and C. At the same time, there was provided an uncoated
cast plate of unsaturated polyester resin (A).
Specimens A, B and C were subjected to the surface hardness test
using a wire brush in a similar manner to Example 1. Few scratches
were formed on specimen A when brushed one or two times, while no
scratch was formed on specimens B and C even if brushed about 100
times. On a boiling test, there occurred scaling-off of the coating
on specimen B after 30 to 40 minutes boiling, while no change was
observed on specimen C even after 2 hours boiling.
EXAMPLE 4
To a commercially available eyeglass lens for shortsightedness of
63 mm .phi. there was applied a hydrophilic acrylic resin, polymer
of 2-hydroxyethyl methacrylate (Hydron, trade name), in a thickness
of about 7 microns and, after drying of the coating, the lens was
covered with a stainless steel mask having circular holes of 300
microns .phi. arranged in a pattern as shown in FIG. 9 at a pitch
of 500 microns and mounted in a vacuum evaporation chamber. A
molybdenum boat was put under the masked lens in the chamber and
there was charged stannic dioxide in the boat. After evacuation of
the chamber to 2 .times. 10.sup..sup.-5 Torr, an electric current
was applied to the molybdenum boat to evaporate stannic oxide on to
the lens to form a discrete coating of a thickness of 500 A. The
lens was then subjected to a test of its non-fogging quality and
the abrasion test. The results obtained are summarized in the
following Table 1 in comparison with those on an uncoated Hydron
surface. The percentage area of openings of the protective film
thus obtained was about 55 %.
Table 1 ______________________________________ Specimen Non-fogging
quality (sec) Abrasion test ______________________________________
Uncoated 20 50 Coated 22 200
______________________________________
As indicated by the above Table, the protective film in accordance
with the present invention enhanced abrasion resistance to a great
extent without sacrifice in the non-fogging quality. The
transparency of the lenses remained unchanged.
EXAMPLE 5
Two glass plates each of 50 mm .times. 50 mm .times. 3 mm were
coated with a 2-hydroxyethyl methacrylate polymer (Hydron)
respectively to form thereon a coating film of a thickness of 23
microns and, after drying, the coated surface of each plate was
covered with a square section mask consisting of an 100 mesh
standard wire netting and set in a vacuum evaporating chamber. An
electric current was applied to a molybdenum boat containing
therein silicon monoxide and located below the plate in the chamber
after evacuation of the chamber to 2 .times. 10.sup..sup.-5 Torr to
form a discrete coating of silicon monoxide of a thickness of 500
A. on one of the plates and of 3,000 A. on the other plate. The
specimens were subjected to determination of the nonfogging quality
and the abrasion test.
The results of the tests were summarized in the following Table 2
in comparison with the properties of an uncoated Hydron surface.
The percentage area of openings of the protective coating on the
two specimens was about 60 %.
Table 2 ______________________________________ Specimen Non-fogging
quality (sec) Abrasion test ______________________________________
Uncoated 160 50 Coated 500 A 150 500 Coated 3,000 A 170 Above 1,000
______________________________________
As indicated by the above Table, the protective films in accordance
with the present invention enhanced the abrasion resistance without
sacrifice in the non-fogging quality and transparency.
EXAMPLE 6
A flat glass plate of 3 mm .times. 50 mm .times. 50 mm was cleaned
and coated with a hydrophilic polymer, polyvinyl alcohol PVA, in a
thickness of about 5 microns. After fully drying the coating, the
plate was set in a vacuum evaporation chamber. In this case, there
was employed a combined mask consisting of three stainless steel
panels each having circular holes of 300 microns .phi. arranged in
a pattern as shown in FIG. 9 at a pitch of 500 microns and stacked
relationship to meet with each other at angles of 22.5.degree. and
45.degree. to form a pattern as shown in FIG. 14. In a molybdenum
boat located in the lower section of the chamber there was charged
bismuth trioxide (Bi.sub.2 O.sub.3). After evacuation of the
chamber to 2 .times. 10.sup..sup.-5 Torr, there was applied an
electric current to the molybdenum boat, to evaporate bismuth
troxide in a thickness of about 500 A. on to the plate. The PVA
film having a protective film was subjected to the non-fogging
quality test and abrasion test together with an unprotected PVA
film for comparison to obtain the results summarized in the
following Table 3. The percentage area of openings of the
protective film was 80%.
Table 3 ______________________________________ Specimen Non-fogging
quality (sec) Abrasion test ______________________________________
Uncoated PVA 20 5 Coated PVA 18 300
______________________________________
EXAMPLE 7
The refractive index of PVA is usually 1.49 to 1.53, that of the
PVA used in the above Example was about 1.51, so that the discrete
protective film could be observed with careful observation because
Bi.sub.2 O.sub.3 has a high refractive index of 2.42. According to
the field of application, it is desirable to make the protective
film invisible, so that, in this Example, there was used a
windshield glass having a substantially identical refractive index
of 1.52. The glass plate was coated with a PVA as used in Example 6
and then coated with a glass film, which is used usually as a
windshield, using a mask as used in Example 6 under a vacuum of 1
.times. 10.sup..sup.-6 Torr with the aid of an electron beam of 20
mA accelerated by a voltage of 4 KV. The distance between the
source and the surface of the substrate was 120 mm and the
evaporating time was about 1 minute. On the PVA surface it was
difficult to confirm the presence of a discrete coating film. The
thickness of the coating film was 1,500 A. and the percentage area
of opening was 80 %. When subjected to the abrasion test, there was
observed no scratch even after brushing 500 times and it was
ascertained that the non-fogging quality is not hindered at all as
indicated by fogging after exposure of about 23 seconds in the
fogging test.
EXAMPLE 8
To a surface of a glass plate of 50 mm .times. 50 mm .times. 3 mm
there was applied a 2-hydroxyethyl methacrylate polymer (Hydron) in
a thickness of 5 microns and, after drying, the Hydron-coated
surface was closely covered by a stainless steel mask having a
number of slits of a width of 500 microns at a pitch of 700
microns. The plate was subjected to evaporation of silicon monoxide
in the same manner as in Example 1 to form thereon a coating film
of a thickness of 3,000 A. and a percentage area of openings of
about 30 %. The results of the non-fogging test and abrasion test
on the specimen were as shown in the Table 4.
Table 4 ______________________________________ Specimen Non-fogging
quality (sec) Abrasion test ______________________________________
Uncoated 18 50 Coated 6 Above 1,000
______________________________________
EXAMPLE 9
A laminated glass plate of 100 mm .times. 100 mm, as usually used
as a safety glass for an automobile windshield, was coated with a
2-hydroxyethyl methacrylate polymer (Hydron) to form a coating film
of a dry thickness of about 7 microns and, after drying, it was set
on an anode of cathode sputtering apparatus. A tin plate was set as
a target on a cathode. Two masks each having holes of 50 microns
.phi. at a pitch of 100 microns and stacked with each other at an
angle of 45.degree. were closely lapped thereover. After evacuation
of the apparatus to 1 .times. 10.sup..sup.-5 Torr, a gaseous
mixture consisting of 95 % of argon and 5 % of oxygen was
introduced therein to adjust the pressure to 2 .times.
10.sup..sup.-2 Torr. A DC sputtering was carried out for about 4
minutes using a DC power source at a DC 5 KV and 200 mA to deposit
on the glass plate a stannic oxide film of a thickness of about
2,000 A. By incorporating gaseous oxygen, not only gaseous argon,
in the inert gas to attain reactive sputtering, vapor of metallic
tin emitted from the target was converted to stannic oxide. The
percentage area of opening of the stannic oxide coating thus
obtained was about 75 %. The properties of the Hydron surface and
of the SnO.sub.2 coated Hydron surface were as follows.
Table 5 ______________________________________ Specimen Non-fogging
quality (sec) Abrasion test ______________________________________
Uncoated 60 50 Coated 55 Above 1,000
______________________________________
EXAMPLE 10
A commercially available eyeglass lens for shortsightedness made of
glass of 63 mm .phi. was coated with a hydrophilic acrylic resin,
2-hydroxyethyl methacrylate polymer (Hydron), in a thickness of
about 16 microns and, after drying, closely covered with a
stainless steel mask having circular holes of 25 microns .phi. in a
pattern as shown in FIG. 9 at a pitch of 110 microns. The lens was
set in a vacuum chamber and a molybdenum boat containing therein
silicon monoxide was placed below it. After the vacuum chamber had
been evacuated to 2 .times. 10.sup..sup.-5 Torr, an electric
current was applied to the molybdenum boat to deposite silicon
monoxide in a thickness of about 1,200 and 3,500 A., on the lens.
The percentage area of the openings was 79 %. The results of
non-fogging quality test and abrasion test were as summarized in
following Table 6.
Table 6 ______________________________________ Specimen Non-fogging
quality Abrasion test ______________________________________ (sec)
Celite Gauge Uncoated 100 400 100 Coated 1,200 A About 140
>5,000 >1,000 Coated 3,500 A About 95 >10,000 >3,000
______________________________________
Thus, as indicated by the above Table, the protective films in
accordance with the present invention enhanced surface hardness to
a great extent and, in addition, the non-fogging quality.
EXAMPLE 11
A mask having circular holes of 15 microns .phi. in an arrangement
as shown in FIG. 9 at a pitch of 80 microns, instead of the mask
25.mu..phi. - 110.mu. pitch prescribed in Example 10, was used. The
percentage area of opening, as determined by microscopic
photographic observation on the resulting protective film, was 92
%. Subjecting the specimen together with a specimen having no
protective film to the non-fogging test and the abrasion test,
there were obtained the results summarized in the following Table
7.
Table 7 ______________________________________ Specimen Non-fogging
test Abrasion test ______________________________________ T/To (%)
Celite Gauze Uncoated 100 400 100 Coated 130 >3,000 >1,000
______________________________________
EXAMPLE 12
A mask having circular holes of 15 microns .phi. in an arrangement
as shown in FIG. 9 at a pitch of 100 microns instead of the mask
25.mu..phi. - 110.mu. pitch prescribed in Example 10, was used, to
deposit a discrete film of stannic oxide of about 1,000 A.
thickness and of a percentage area of openings of 95 %. The results
on the specimen of non-fogging and abrasion tests were as
summarized in the following Table 8.
Table 8 ______________________________________ Specimen Non-fogging
test Abrasion test ______________________________________ T/To (%)
Celite Gauge Uncoated 100 350 80 Coated 105 >1,000 100
______________________________________
EXAMPLE 13
To a 3 mm thick polycarbonate plate of 50 mm .times. 50 mm there
was applied a hydrophilic resin (Hydron) in a thickness of about 7
microns and, after drying, the plate was set in a vacuum
evaporating chamber together with a nickel mask having circular
holes of a raduis of 35 microns arranged in a pattern as shown in
FIG. 9 at a pitch of 110 microns closely applied thereto. In the
vacuum evaporating chamber there was set an electron gun and a
block of an ordinary sheet glass was put in front of the electron
gun as a target. The chamber was evacuated to
5.times.10.sup..sup.-5 Torr and 5 .times. electric current of 4 KV,
30 mA was imposed on the gun to melt and evaporate the block of
glass. During evaporation of about 5 minutes there was formed a
discrete coating film of a thickness of about 1.8 microns and a
percentage area of openings of 61.0 % was formed on the surface of
the substrate plate.
Table 9 ______________________________________ Specimen Non-fogging
quality Abrasion test ______________________________________ T/To
(%) Celite Gauge Uncoated 100 400 100 Coated 113 >50,000
>10,000 ______________________________________
EXAMPLE 14
To a surface of a 5 mm thick glass plate of 80 mm .times. 100 mm
there was applied a hydrophilic resin (Hydron) in a thickness of
about 5 microns and, after drying, the plate was closely covered
with a nickel mask having circular holes of a radius of 40 microns
arranged in a pattern as shown in FIG. 9 at a pitch of 150 microns
and set in a sputtering chamber. The back side of the substrate
plate was closely attached through a thin layer of a silicon grease
to a cooled RF-anode (grounded) to effect cooling. On the opposite
cathode there was set a silicon plate of 150 mm .times. 150
mm.times. 5 mm and the chamber was evacuated to 2 .times.
10.sup..sup.-5 Torr. Gaseous nitrogen was then introduced into the
chamber to adjust the pressure to 3 .times. 10.sup..sup.-3 Torr.
Then sputtering was carried out for 10 minutes at a voltage of 3.0
KV and an anode current of 250 mA to form a coating film of silicon
nitride of a thickness of about 2,000 A. The percentage area of
opening of the film was 90 %.
Table 10 ______________________________________ Specimen
Non-fogging quality Abrasion test
______________________________________ T/To (%) Celite Gauge
Uncoated 100 400 100 Coated 130 >3,000 >1,500
______________________________________
EXAMPLE 15
A cleaned poly(methyl methacrylate) plate of 10 cm .times. 10 cm
.times. 3 mm was set in a vacuum evaporating chamber and metallic
chromium was evaporated onto its surface through a nickel mask
having circular holes of 15 microns .phi. at a pitch of 85 microns
to form an about 1.0 micron coating in thickness. On to a substrate
of the same quality there was evaporated silicon dioxide to form a
coating film of an about 1.0 micron thickness through the same
mask. The percentage area of openings of sample A (chromium coated)
and of sample B (silicon dioxide coated) were both 96.5 %, and the
transmittance of each element itself of specimen A was about 7 %
and of sample B was about 92 %. The haze of sample A, as determined
by ASTM D-1003, was 0.62 % and of B was 2.3 %. The whole
transmittance for visible rays of sample A was 87.6 % and of sample
B was 91.0 %, any difference in transmittance between the two
samples being indiscernible to the naked eye.
EXAMPLE 16
A cleaned polycarbonate plate of 10 cm .times. 10 cm .times. 3 mm
was set in a vacuum evaporating chamber and a 0.8 micron thick film
of silicon monoxide was evaporated onto its surface through a
nickel mask having circular holes of 15 microns .phi. at a pitch of
85 microns and subsequently an about 0.2 micron thick metallic
nickel film was evaporated thereover to form specimen A. An about
1.0 micron thick silicon monoxide film alone was evaporated on to a
polycarbonate plate of the same dimensions to form sample B. The
percentage area of coating of both samples was about 3 %. The
transmittance of each element itself of sample A was about 15 %,
while the haze of sample A was 0.83 % and of sample B was 2.6 % and
the whole transmittance of sample A was 88.5 % and of B was 90.5 %,
this indicating that there was no substantial difference in
transmittance between the two samples.
EXAMPLE 17
To a surface of a cleaned glass plate of 10 cm .times. 10 cm
.times. 3 mm there was applied an about 5 microns thick film of a
hydrophilic resin, 2-hydroxyethyl methacrylate polymer (Hydron)
and, after drying of the coating film, the plate was set in a
vacuum evaporating chamber. On to the coated surface of the plate
there were evaporated concurrently aluminum oxide Al.sub.2 O.sub.3
and metallic aluminum from separate evaporating sources through a
stainless steel mask having circular holes of 30 microns .phi.
distributed uniformly at a pitch of 200 microns to form thereon a
protective film of a thickness of about 0.6 micron (specimen A). In
a similar manner, aluminum oxide alone was evaporated on to a
cleaned glass plate of the same dimensions to form thereon an about
0.6 micron thick aluminum oxide film (specimen B). The percentage
area of coating of specimen A and of B were both about 3 % and the
haze of specimen A was about 0.53 % and of B was about 2.7 %.
EXAMPLE 18
As a substrate there was provided a polarizing plate consisting of
a polarizing frame interposed between two yellow colored
poly(methyl methacrylate) plates and having a transmittance of
about 80 %. After cleaning, the substrate was covered with a mask
having circular holes of 80 microns .phi. arranged in a pattern as
shown in FIG. 9 at a pitch of 250 microns. The assembly was set in
an RF sputtering chamber and subjected to a reactive sputtering in
an atmosphere of gaseous nitrogen to form a discrete protective
film of silicon nitride Si.sub.3 N.sub.4 of a thickness of 3,000 A.
on a surface of the substrate (specimen A). A 3,000 A. thick
chromium-nitride discrete film was formed on another substrate of
the same quality in a similar manner (specimen B). The Si.sub.3
N.sub.4 was highly transparent but the CrN was brown in color. The
transmittance for visible rays of the Si.sub.3 N.sub.4 film itself
(3,000 A. in thickness) was about 90 % and of the CrN was about 25
%. The haze of specimen A was 1.65 % and of specimen B was 0.45
%.
EXAMPLE 19 0.45
An evaporation mask A was prepared by providing a unit pattern
consisting of a regular hexagon having randomly distributed therein
five rectangular holes of 40 microns .times. 12 microns, the length
of a side of said hexagon being 124 microns, forming a block
pattern on the basis of the unit pattern in the manner as fully
discribed above with reference to FIG. 10(b) and rotating the block
pattern two times. There was provided an evaporation mask B having
circular holes of 25 microns .phi. arranged in a regular section
pattern at pitches of 100 microns. On to separate substrates there
was evaporated silicon dioxide through the mask A or B to form a
coating film of a thickness of about 3,400 A. Thus there were
obtained coated specimens A and B, both having a percentage area of
openings of about 92 %. Specimens B and C and a specimen A of an
uncoated substrate were subjected to an abrasion test and moisture
absorption-desorption response test. The abrasion test was made
employing a rotary abrasion tester provided with an abrasion tip
consisting of a silicone rubber covered by a gauge. The abrasion
resistance was determined by measuring the time until there was
formed a distinctive scratch by abrasion under a load of 500
g/cm.sup.2 at a speed of 30 rpm. The moisture absorption-desorption
response was determined by measuring the quantity of transmitted
light using a He-Ne laser beam while applying steam at 40 C to the
surface of a specimen at a flow rate of 1,000 ml./min. The decrease
of the quantity of transmitted light corresponding to the point Q
and U in the curve as shown in FIG. 8 was indicated in relative
value regarding that of specimen B as 1.0. The moisture desorption
(dehumidification) response was expressed by the time until the
transmittance of a specimen reversed to 99 % of its initial value
(before application of steam) after stopping the application of
steam. The application of steam was made for the same time for all
the specimens. The desorption response also was indicated in
relative value to that of specimen C as 1.00.
Table 11 ______________________________________ Specimen Abrasion
test (min) Decrease Desorption response
______________________________________ A 90 - 100 About 0.25 About
1.15 B 30 - 40 1.00 About 1.50 c 5 - 10 -- 1.00
______________________________________
The above Table indicates that specimens A and B both have far
higher surface hardnesses than specimen C has, and specimen A is
harder than specimen B while the former is less in decrease of
transmitted light due to the protective coating film than the
latter and, in addition, superior in desorption response, that is
to say, that the process of the present invention is excellent as a
process for enhancing surface hardness of a substrate.
EXAMPLE 20
A 460 microns square having randomly distributed therein 6
rectangular holes of 50 microns .times. 157 microns as a unit
pattern was rotated by 90.degree. three times to form a block
pattern consisting of 4 unit patterns. The block pattern was
subjected to two turn-over operations to form an enlarged pattern
thereby to form an evaporation mask D. There was provided an
evaporation mask E having circular holes of 100 microns .phi. in a
pattern as shown in FIG. 9 at pitches of 200 microns. On to a
substrate there was evaporated an about 960 A. thick silicon
monoxide film through mask D or E to obtain a specimen D or E, both
having a percentage area of openings of about 92 %. Specimens D and
E and a specimen of an uncoated substrate were subjected to the
same test as in Example 19 to obtain the results summarized in the
following Table 12.
Table 12 ______________________________________ Specimen Abrasion
test (min) Decrease Desorption Response
______________________________________ D About 120 0.30 About 1.50
E About 60 1.00 About 4.50 F 5 - 10 -- 1.00
______________________________________
It is indicated by the above Table that a discrete protective film
consisting of non-circular elements is superior in both surface
hardness and moisture absorption-desorption response to a discrete
protective film having circular elements even if both have the same
percentage area of openings.
* * * * *