U.S. patent application number 09/939668 was filed with the patent office on 2002-04-25 for optical element having antireflection film.
This patent application is currently assigned to HOYA CORPORATION. Invention is credited to Mitsuishi, Takeshi, Shinde, Kenichi.
Application Number | 20020048087 09/939668 |
Document ID | / |
Family ID | 18746915 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048087 |
Kind Code |
A1 |
Mitsuishi, Takeshi ; et
al. |
April 25, 2002 |
Optical element having antireflection film
Abstract
An optical element having a plastic substrate and an
antireflection film provided on the plastic substrate,
characterized in that the optical element has a basic layer
comprising Nb between the plastic substrate and the antireflection
film. The optical element has high adhesiveness between the plastic
substrate and the antireflection film and is characterized by
excellent resistance to heat, impact, alkali, and abrasion.
Inventors: |
Mitsuishi, Takeshi; (Tokyo,
JP) ; Shinde, Kenichi; (Tokyo, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
HOYA CORPORATION
|
Family ID: |
18746915 |
Appl. No.: |
09/939668 |
Filed: |
August 28, 2001 |
Current U.S.
Class: |
359/580 ;
359/586 |
Current CPC
Class: |
G02B 1/115 20130101 |
Class at
Publication: |
359/580 ;
359/586 |
International
Class: |
G02B 001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2000 |
JP |
2000-258628 |
Claims
In the claims:
1. An optical element comprising a plastic substrate, an
antireflection film, and a basic layer comprising niobium (Nb)
between the plastic substrate and the antireflection film.
2. An optical element according to claim 1 wherein the basic layer
consists of niobium.
3. An optical element according to claim 1 wherein the basic layer
has a thickness of 1-5 nm.
4. An optical element according to claim 1 wherein the
antireflective film comprises a low-refractive layer and a
high-refractive layer.
5. An optical element according to claim 4 wherein the
low-refractive layer comprises SiO.sub.2.
6. An optical element according to claim 4 wherein the
high-refractive layer comprises TiO.sub.2.
7. An optical element according to claim 1 comprising a cured film
provided between the plastic substrate and the basic layer.
8. An optical element according to claim 7 wherein the cured film
is made from a mixture of metal oxide colloid particles and at
least one organosilicon compound of the formula
(1):(R.sup.1).sub.a(R.sup.2).sub.bS- i(OR.sup.3).sub.4-(a+b)
(1)wherein R.sup.1 and R.sup.2 each independently represents an
organic group selected from an C.sub.1-8 alkyl group, an C.sub.2-8
alkenyl group, an aryl group, a phenyl group, a 5-or 6-membered
heteroaryl group having at least one heteroatom selected from
sulfur and nitrogen which may optionally be substituted by one or
more C.sub.1-3 alkyl group (s), an C.sub.1-8 acyl group, a halogen
atom, a glycidoxy group, an epoxy group, an amino group, a phenyl
group, a mercapto group, a methacryloxy group, and a cyano group;
R.sup.3 represents an organic group selected from an alkyl group
having from 1 to 8 carbon atoms, an C.sub.1-8 acyl group, and a
phenyl group; and a and b each independently indicates an integer
of 0 or 1.
9. An optical element according to claim 1 wherein the
antireflection film is one having the following layers successively
from the plastic substrate side: SiO.sub.2 layer, TiO.sub.2 layer,
SiO.sub.2 layer, TiO.sub.2 layer SiO.sub.2 layer, TiO.sub.2 layer,
and SiO.sub.2 layer.
10. An optical element according to claim 1 having an
antireflection film having the following layers successively from
the plastic substrate side: SiO.sub.2 layer, Nb layer, SiO.sub.2
layer, TiO.sub.2 layer, SiO.sub.2 layer, TiO.sub.2 layer, and
SiO.sub.2 layer.
11. An optical element according to any one of claims 1-10 wherein
at least one layer is obtainable by an ion-assisted process.
12. An optical element according to any one of claims 1-10 wherein
each layer is formed by an ion-assisted process.
Description
[0001] The present invention relates to an optical element having
an antireflection film. It relates to an optical element having an
antireflection film that has excellent adhesiveness between a
plastic substrate and the antireflection film, abrasion resistance,
heat resistance, alkali resistance and impact resistance.
[0002] Heretofore known are optical elements having an
antireflection film provided on a plastic substrate. Also known are
optical elements having a thin metal film layer provided on the
surface of a plastic substrate for enhancing the adhesiveness
between the plastic substrate and the antireflection film. For
example, Japanese Patent Laid-Open No. 186202/1987 discloses an
antireflection film for an optical element having a thin metal film
layer provided on the surface of a plastic substrate, in which the
metal layer is made of a metal selected from the group consisting
of copper (Cu), aluminum (Al), nickel (Ni), gold (Au), chromium
(Cr), palladium (Pd) and tin (Sn).
[0003] However, these optical elements having an antireflection
film are unsatisfactory with respect to their heat resistance and
impact resistance. Therefore, it is desirable to provide optical
elements having an antireflection film that have improved physical
properties such as heat resistance, abrasion resistance, alkali
resistance and impact resistance.
[0004] Heretofore, in general, a basic layer made of SiO.sub.2 has
been provided in a plastic lens for enhancing the strength of
coating films. However, the basic layer made of SiO.sub.2 has a
drawback of lowering the heat resistance of the plastic lens.
[0005] The present invention provides an optical element having an
antireflection film having excellent adhesiveness between a plastic
substrate and the antireflection film, heat resistance, abrasion
resistance, alkali resistance and impact resistance.
[0006] The present invention addresses the problems noted above.
The inventors have determined that when a layer made of niobium
(Nb) is provided between a plastic substrate and an antireflection
film to form an optical element, the adhesiveness between the
plastic substrate and the antireflection film, the heat resistance,
abrasive resistance, alkali resistance and the impact resistance of
the optical element are improved.
[0007] The optical element of the invention has a basic layer made
of Nb, and therefore, has not only excellent adhesiveness between
the plastic substrate and the antireflection film, heat resistance
and impact resistance, but also excellent alkali and abrasion
resistance and properties such that an absorbance index inherent to
metals is low.
[0008] The basic layer may consist of Nb (that is 100% by weight of
Nb), or may comprise a mixture of niobium and up to 50% by weight,
preferably 25% by weight of other elements such as aluminum(Al),
chromium(Cr), tantalum(Ta) and mixtures of two or more thereof. The
antireflection film may also be comprised of multi-layers, and at
least one of the layers is obtainable by an ion-assisted process.
The basic layer comprising Nb may also be formed by an ion-assisted
process.
[0009] The "ion-assisted process" referred to herein is a well
known process also called "ion beam assisted vapor deposition
process". According to this process, a material is deposited on a
substrate, such as a lens substrate, by vapor deposition using an
ion plasma in a gas atmosphere, such as argon (Ar) and/or oxygen.
In a common apparatus suitable to perform this process, preferred
vapor deposition conditions are an accelerating voltage of
100-250V, and an accelerating current of 50-150 mA. A detailed
description is given in e.g. U.S. Pat. No. 5,268,781. Further
details can be derived from M. Fliedner et al., Society of Vacuum
Coaters, Albuquerque, N.M., USA. p237-241, 1995 as well as from the
references cited therein.
[0010] In the ion-assisted process, argon (Ar) may be used as the
ionizing gas for preventing oxidation of films being formed.
Although argon is preferred, other ionizing gases such as oxygen
and nitrogen, or mixtures of these gases could also be used. This
stabilizes the quality of the films formed and enables easy control
of the thickness of the films by the use of an optical film
thickness meter.
[0011] For ensuring good adhesiveness between the plastic substrate
and the basic layer and for ensuring good uniformity of the initial
film morphology in vapor deposition in the ion-assisted process,
the plastic substrate may be subjected to ion gun pretreatment
before the basic layer is formed thereon. The ionizing gas in the
ion gun pretreatment may be any of oxygen, nitrogen, Ar, or
mixtures thereof. For the preferred power range, the accelerating
voltage is from 50 V to 200 V, and the accelerating current is from
50 mA to 150 mA. If the accelerating voltage is lower than 50 V, or
the accelerating current is lower than 50 mA, an effect for
improving the adhesiveness between the plastic substrate and the
basic layer formed thereon may not be sufficient. However, if the
accelerating voltage exceeds 200 V, or the accelerating current
exceeds 150 mA, the plastic substrate and also the cured film and
the hard coat layer thereon may possibly be yellowed, or the
abrasion resistance of the optical element may possibly be
lowered.
[0012] In the invention, after the basic layer comprising Nb has
been formed on the substrate, an antireflection layer is formed by
any suitable process. For example, it may be formed by vapor
deposition, such as chemical vapor deposition (CVD) or physical
vapor deposition (PVD), or by other methods such as ion plating
vapor deposition.
[0013] In one embodiment, the antireflection film has at least one
SiO.sub.2 layer as a low-refraction layer and at least one
TiO.sub.2 layer as a high-refraction layer. If desired, the
antireflection film may have a metal layer comprising Nb.
[0014] For relieving the stress within the low-refraction layer
such as an SiO.sub.2 layer, when the SiO.sub.2 layer is formed in
an ion-assisted process in which Ar is used for the ionizing gas
for SiO.sub.2 deposition, the abrasion resistance can be improved.
Regarding the ion-assisting condition for obtaining the result, the
ion current density on the dome in the vapor deposition device is
from 15 to 35 .mu.A, and the accelerating voltage is from 400 to
700 V. If the ion current density is lower than 15 .mu.A or the
accelerating voltage is lower than 400 V, both an effect for
relieving the stress and an effect for improving the abrasion
resistance may be hardly obtained. If, however, the ion current
density exceeds 35 .mu.A or the accelerating voltage exceeds 700 V,
the plastic substrate may possibly be yellowed, or the optical
performance may possibly be adversely affected.
[0015] The high-refraction layer such as a TiO.sub.2 layer may also
be formed in an ion-assisted process. For the ionizing gas in the
ion-assisted process for forming the high-refraction layer, a mixed
gas of O.sub.2 and Ar is used. The mixing ratio of O.sub.2 to Ar
based on the volume of flowing gases preferably ranges from
1:0.5-2. It is possible to improve the refractive index of the
high-refraction layer formed and to promote the improvement of the
abrasion resistance by using an ion-assisted process. Materials for
forming the high-refraction layer are TiO.sub.2, Nb.sub.2O.sub.5,
Ta.sub.2O.sub.5, ZrO.sub.2, Y.sub.2O.sub.3, and mixtures thereof.
Preferred examples include TiO.sub.2, Nb.sub.2O.sub.5,
Ta.sub.2O.sub.5 and mixtures thereof.
[0016] As a suitable ion-assisting condition for using TiO.sub.2,
Nb.sub.2O.sub.5 or their mixtures as the metal oxide, the ion
current density on the dome in the vapor deposition device is from
8 to 15 .mu.A, and the accelerating voltage is from 300 to 700 V.
The volume ratio of O.sub.2 to Ar in the ionizing gas mixture is
from 1/0.7 to 1/1.0. If the ion current density, the accelerating
voltage and the ionizing gas ratio overstep the defined ranges, the
intended refractive index may not be obtained, and, in addition,
its absorbance index may likely increase, and its abrasion
resistance may possibly be lowered.
[0017] As a suitable ion-assisting condition for using
Ta.sub.2O.sub.5 or its mixtures as the metal oxide, the ion current
density on the dome in the vapor deposition device is from 12 to 20
.mu.A, and the accelerating voltage is from 400 to 700 V. The
volume ratio of O.sub.2 to Ar in the ionizing gas mixture is from
1/0.5 to 1/2.0. If the ion current density, the accelerating
voltage and the ionizing gas ratio overstep the defined ranges, the
intended refractive index may not be obtained, and, in addition,
its absorbance index may likely increase, and its abrasion
resistance may possibly be lowered.
[0018] A suitable thickness of the basic layer of the optical
element of the invention is from 1.0 to 5.0 nm. If its thickness
oversteps the defined range, the basic layer may possibly present a
problem of absorbance within the film.
[0019] One embodiment of the layer constitution of the basic layer
and the antireflection film formed on the plastic substrate is
described below. Herein, the laminate of the 1st to 7th layers
serves as the antireflection film.
[0020] Basic layer: Nb layer (film thickness: 1 to 5 nm)
[0021] 1st layer: SiO.sub.2 layer (film thickness: 5 to 50 nm)
[0022] 2nd layer: TiO.sub.2 layer (film thickness: 1 to 15 nm)
[0023] 3rd layer: SiO.sub.2 layer (film thickness: 20 to 360
nm)
[0024] 4th layer: TiO.sub.2 layer (film thickness: 5 to 55 nm)
[0025] 5th layer: SiO.sub.2 layer (film thickness: 5 to 55 nm)
[0026] 6th layer: TiO.sub.2 layer (film thickness: 5 to 130 nm)
[0027] 7th layer: SiO.sub.2 layer (film thickness: 70 to 100
nm)
[0028] The ranges of the film thickness mentioned above are the
most preferred ones for the adhesiveness between the plastic
substrate and the antireflection film and for the heat resistance
and impact resistance of the optical element.
[0029] Another embodiment of the layer constitution of the basic
layer and the antireflection film is mentioned below. Herein, the
laminate of the 1st to 7th layers serves as the antireflection
film.
[0030] Basic layer: Nb layer (film thickness: 1 to 5 nm)
[0031] 1st layer: SiO.sub.2 layer (film thickness: 20 to 100
nm)
[0032] 2nd layer: Nb layer (film thickness: 1 to 5 nm)
[0033] 3rd layer: SiO.sub.2 layer (film thickness: 20 to 100
nm)
[0034] 4th layer: TiO.sub.2 layer (film thickness: 5 to 55 nm)
[0035] 5th layer: SiO.sub.2 layer (film thickness: 5 to 50 nm)
[0036] 6th layer: TiO.sub.2 layer (film thickness: 5 to 130 nm)
[0037] 7th layer: SiO.sub.2 layer (film thickness: 70 to 100
nm)
[0038] The ranges of the film thickness mentioned above are the
most preferred ones for the adhesiveness between the plastic
substrate and the antireflection film and for the heat resistance
and impact resistance of the optical element.
[0039] The material for the plastic substrate for use in the
invention is not specifically limited. Suitable materials include,
for example, methyl methacrylate homopolymers, copolymers of methyl
methacrylate and one or more other monomers such as diethylene
glycol bisallyl carbonate or benzyl methacrylate, diethylene glycol
bisallyl carbonate homopolymers, copolymers of diethylene glycol
bisallyl carbonate and one or more other monomers such as methyl
methacrylate and benzyl methacrylate, sulfur-containing copolymers,
halogen copolymers, polycarbonates, polystyrenes, polyvinyl
chlorides, unsaturated polyesters, polyethylene terephthalates,
polyurethanes, and polythiourethanes. Preferred examples include
polythiourethane, diethylene glycol bisallyl carbonate
homopolymers, and sulfur-containing copolymers.
[0040] If desired, the optical element of the invention may have a
cured film between the plastic substrate and the basic layer.
[0041] For the cured film, in general, a coating composition is
used that comprises metal oxide colloid particles and one or more
organosilicon compounds represented by the following general
formula (1):
(R.sup.1).sub.a(R.sup.2).sub.bSi(OR.sup.3).sub.4-(a+b) (1)
[0042] wherein R.sup.1 and R.sup.2each independently represents an
organic group selected from an C.sub.1-8 alkyl group, an C.sub.2-8
alkenyl group, an aryl group, a phenyl group, a 5-or 6-membered
heteroaryl group having at least one heteroatom selected from
sulfur and nitrogen which may optionally be substituted by one or
more C.sub.1-3 alkyl group (s), an C.sub.1-8 acyl group, a halogen
atom, a glycidoxy group, an epoxy group, an amino group, a phenyl
group, a mercapto group, a methacryloxy group, and a cyano group;
R.sup.3represents an organic group selected from an alkyl group
having from 1 to 8 carbon atoms, an C.sub.1-8 acyl group, and a
phenyl group; and a and b each independently indicates an integer
of 0 or 1. For applying the coating composition onto the surface of
a plastic lens substrate, any ordinary method of dip coating, spin
coating, or spraying may be employed. In view of the smoothness of
the coated film, especially preferred is dip coating or spin
coating. Having been applied to lens substrates, the composition is
cured by drying it in hot air or by exposing it to active energy
rays. Preferably, it is cured in hot air at 70 to 200.degree. C.,
and more preferably at 90 to 150.degree. C. For the active energy
rays, preferred are far-infrared rays as not damaging the film by
heat.
[0043] The metal oxide colloid particles generally are fine metal
oxide particles having a particle size of 1-500 nm. Preferred
examples thereof are colloid particles of tungsten oxide
(WO.sub.3), zinc oxide (ZnO), silicon oxide (SiO.sub.2), aluminum
oxide (Al.sub.2O.sub.3), titanium oxide (TiO.sub.2), zirconium
oxide (ZrO.sub.2), tin oxide (SnO.sub.2), beryllium oxide (BeO)
orantimony oxide (Sb.sub.2O.sub.5) These metal oxides may be used
either singly or in admixture of two or more thereof.
[0044] The organosilicon compound of the general formula (1)
includes, for example, methyl silicate, ethyl silicate, n-propyl
silicate, isopropyl silicate, n-butyl silicate, sec-butyl silicate,
tert-butyl silicate, tetraacetoxysilane, methyltrimethoxysilane,
methyltriethoxysilane, methyltripropoxysilane,
methyltriacetoxysilane, methyltributoxysilane,
methyltripropoxysilane, methyltriamyloxysilane,
methyltriphenoxysilane, methyltribenzyloxysilane,
methyltriphenethyloxysilane, glycidoxymethyltrimethoxysilane,
glycidoxymethyltriethoxysilane,
.alpha.-glycidoxyethyltriethoxysilane,
.beta.-glycidoxyethyltrimethoxysil- ane,
.beta.-glycidoxyethyltriethoxysilane,
.alpha.-glycidoxypropyltrimetho- xysilane,
.alpha.-glycidoxypropyltriethoxysilane, .beta.-glycidoxypropyltr-
imethoxysilane, .beta.-glycidoxypropyltriethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxypropyltriethoxy- silane,
.gamma.-glycidoxypropyltripropoxysilane, .gamma.-glycidoxypropyltr-
ibutoxysilane, .gamma.-glycidoxypropyltriphenoxysilane,
.alpha.-glycidoxybutyltrimrethoxysilane,
.alpha.-glycidoxybutyltriethoxys- iane,
.beta.-glycidoxybutyltrimethoxysilane,
.beta.-glycidoxybutyltriethox- ysilane,
.gamma.-glycidoxybutyltrimethoxysialne, .gamma.-glycidoxybutyltri-
ethoxysilane, .delta.-glycidoxybutyltrimethoxysiane,
.delta.-glycidoxybutyltriethoxysilane,
(3,4-epoxycyclohexyl)methyltrimeth- oxysilane,
(3,4-epoxycyclohexyl)methyltriethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
.beta.-(3,4-epoxycycloh- exyl)ethyltripropoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltributoxysila- ne,
.beta.-(3,4-epoxycyclohexyl)ethyltriphenoxysilane,
.gamma.-(3,4-epoxycyclohexyl)propyltrimethoxysilane,
.gamma.-(3,4-epoxycyclohexyl)propyltriethoxysilane,
.delta.-(3,4-epoxycyclohexyl)butyltrimethoxysilane,
.delta.-(3,4-epoxycyclohexyl)butyltriethoxysilane,
glycidoxymethylmethyldimethoxysilane,
glycidoxymethylmethyldiethoxysilane- ,
.alpha.-glycidoxyethylmethyldimethoxysilane,
.alpha.-glycidoxyethylmethy- ldiethoxysilane,
.beta.-glycidoxyethylmethyldimethoxysilane,
.beta.-glycidoxyethylmethyldiethoxysilane,
.alpha.-glycidoxypropylmethyld- imethoxysilane,
.alpha.-glycidoxypropylmethyldiethoxysilane,
.beta.-glycidoxypropylmethyldimethoxysilane,
.beta.-glycidoxypropylmethyl- diethoxysilane,
.gamma.-glycidoxypropylmethyldimethoxysilane,
.gamma.-glycidoxypropylmethyldiethoxysilane,
.gamma.-glycidoxypropylmethy- ldipropoxysilane,
.gamma.-glycidoxypropylmethyldibutoxysilane,
.gamma.-glycidoxypropylmethyldiphenoxysilane,
.gamma.-glycidoxypropylethy- ldimethoxysilane,
.gamma.-glycidoxypropylethyldiethoxysilane,
.gamma.-glycidoxypropylvinyldimethoxysilane,
.gamma.-glycidoxypropylvinyl- diethoxysilane,
.gamma.-glycidoxypropylphenyldimethoxysilane,
.gamma.-glycidoxypropylphenyldiethoxysilane, ethyltrimethoxysilane,
ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane,
vinyltrimethoxyethoxysilane, phenyltrimethoxysilane,
phenyltriethoxysilane, phenyltriacetoxysilane,
.gamma.-chloropropyltrimet- hoxysilane,
.gamma.-chloropropyltriethoxysilane, .gamma.-chloropropyltriac-
etoxysilane, 3,3,3-trifluoropropyltrimethoxysilane,
.gamma.-methacryloxypropyltrimethoxysilane,
.gamma.-mercaptopropyltrimeth- oxysilane,
.gamma.-mercaptopropyltriethoxysilane, .beta.-cyanoethyltrietho-
xysilane, chloromethyltrimethoxysilane,
chloromethyltriethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-aminopropylmethyldimethoxysilane,
.gamma.-aminopropylmethyldimethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-a- minopropyltriethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-aminopropylmethyl- diethoxysilane,
dimethyldimethoxysilane, phenylmethyldimethoxysilane,
dimethyldiethoxysilane, phenylmethyldiethoxysilane,
.gamma.-chloropropylmethyldimethoxysilane,
.gamma.-chloropropylmethyldiet- hoxysilane,
dimethyldiacetoxysilane, .gamma.-methacryloxypropylmethyldimet-
hoxysilane, .gamma.-methacryloxypropylmethyldiethoxysilane,
.gamma.-mercaptopropylmethyldimethoxysilane,
.gamma.-mercaptopropylmethyl- diethoxysilane,
methylvinyldimethoxysilane, and methylvinyldiethoxysilane.
EXAMPLES
[0045] The invention is described in more detail with reference to
the following Examples, which, however, are not intended to
restrict the scope of the invention.
[0046] The physical properties of the optical elements obtained in
the following Examples and Comparative Examples were evaluated
according to the methods mentioned below.
[0047] (1) Luminous Transmittance:
[0048] Using a spectrophotometer, U-3410 made by Hitachi, Ltd., the
luminous transmittance, Y of a plastic lens as a sample, having an
antireflection film on both surfaces, was measured.
[0049] (2) Luminous Reflectance:
[0050] Using a spectrophotometer, U-3410 made by Hitachi, Ltd., the
luminous reflectance, Y of a plastic lens as a sample, having an
antireflection film on both surfaces, was measured.
[0051] (3) Film Adhesiveness:
[0052] Using a cutting tool, the surface of a plastic lens was cut
to have 100 cross-cuts of 1 mm.times.1 mm each. An adhesive tape,
Cellotape was stuck on its cross-cut area, and peeled off at a
stroke. The number of remained cross-cuts was counted and shown in
the following Tables, in which (number of cross-cuts remained)/100
indicates the film adhesiveness.
[0053] (4) Abrasion Resistance:
[0054] The surface of a plastic lens was rubbed with steel wool
under a load of 1 kgf/cm.sup.2 applied thereto. After 20 strokes of
rubbing, the surface condition of the plastic lens was evaluated
according to the following criteria:
[0055] UA: Scratched little.
[0056] A: A few thin scratch marks found.
[0057] B: Many thin scratch marks and a few thick scratch marks
found.
[0058] C: Many thin and thick scratch marks found.
[0059] D: Almost completely peeled.
[0060] (5) Heat Resistance:
[0061] A plastic lens was put into an oven preheated to a selected
temperature, and was left there for 1 hour. This experiment was
performed at different temperatures, starting from 60.degree. C.
with increments of 5.degree.. The temperature was measured, at
which the lens could not withstand the heat treatment and was
cracked after 1 hour. This temperature is given as heat resistance
in the Tables below.
[0062] (6) Alkali Resistance:
[0063] A plastic lens was dipped in an aqueous 10% NaOH solution
for 1 hour, and its surface condition was evaluated according to
the following criteria:
[0064] UA: Changed little.
[0065] A: A few peeled dots found.
[0066] B: Many peeled dots found everywhere on the surface.
[0067] C: Many peeled dots found everywhere on the surface, and a
few peeled squares found.
[0068] D: Almost completely peeled.
[0069] (7) Impact Resistance:
[0070] A plastic lens having a center thickness of 2.0 mm and a
power of lens of 0.00 was prepared and subjected to a drop ball
test as defined by the Food and Drug Administration. "O" indicates
a good sample; and "x" indicates a rejected sample.
Examples 1 to 12
[0071] 90 parts by weight of colloidal silica (Snowtex-40,
available from Nissan Chemical Industries, ltd.), 81.6 parts by
weight of methyltrimethoxysilane and 176 parts by weight of
.gamma.-glycidoxypropyl- trimethoxysilane as organosilicon
compounds, 2.0 parts by weight of 0.5 N hydrochloric acid, 20 parts
by weight of acetic acid, and 90 parts by weight of water were
charged into a glass container, and the solution was stirred at
room temperature for 8 hours. Then, the resulting solution was left
at room temperature for 16 hours to obtain a hydrolyzed solution.
To this solution were added 120 parts by weight of isopropyl
alcohol, 120 parts by weight of n-butyl alcohol, 16 parts by weight
of aluminum acetylacetone, 0.2 parts by weight of a silicone
surfactant, and 0.1 part by weight of a UV absorbent. The mixture
was stirred at room temperature for 8 hours, and then aged at room
temperature for 24 hours to obtain a coating solution.
[0072] A plastic lens substrate (made from diethylene glycol
bisallyl carbonate, and having a refractive index of 1.50, a center
thickness of 2.0 mm and a power of lens of 0.00), which had been
pretreated with an aqueous alkaline solution, was dipped in the
coating solution. After completion of dipping, the plastic lens was
taken out at a pulling rate of 20 cm/min. Then, the plastic lens
was heated at 120.degree. C. for 2 hours to form a cured film.
Next, the resulting plastic lens was subjected to an ion gun
treatment according to an ion-assisted process using an Ar gas
under the condition of the ion acceleration voltage and exposure
time as shown in Tables 1 to 6, thereby making it have a cured hard
coat layer (hereinafter referred to as layer A).
[0073] Next, a basic layer and a functional film composed of the
1st to 7th layers shown in Tables 1 to 6 were formed on the hard
coat layer A, according to an ion-assisted process under the
condition shown in Tables 1 to 6, thereby obtaining plastic
lenses.
[0074] The plastic lenses were evaluated according to the methods
(1) to (7) mentioned above, and the results are shown in Tables 1
to 6. In the Tables, the wavelength of measurement for measuring
optical thickness of the film is 500 nm.
Comparative Examples 1 to 4
[0075] Plastic lenses were obtained in the same manner as in
Examples 1 to 12, except that the basic layer was not formed and
that the hard coat layer and the functional film composed of the
1st to 7th layers were formed not in the ion-assisted process but
in the vapor deposition.
[0076] The plastic lenses were evaluated according to the methods
(1) to (7) mentioned above, and the results are shown in Tables 7
and 8.
1TABLE 1 Example 1 Example 2 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 60 sec
60 sec Gas used Ar Ar Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer Nb 4.0 nm 150 V 100 mA Nb 4.0 nm
150 V 100 mA 1st layer SiO.sub.2 31.5 nm 450 V 160 mA SiO.sub.2
22.0 nm 450 V 160 mA 2nd layer TiO.sub.2 3.5 nm 360 V 105 mA
TiO.sub.2 29.0 nm 360 V 105 mA 3rd layer SiO.sub.2 235.0 nm 450 V
160 mA SiO.sub.2 48.5 nm 450 V 160 mA 4th layer TiO.sub.2 23.5 nm
360 V 105 mA TiO.sub.2 98.0 nm 360 V 105 mA 5th layer SiO.sub.2
42.5 nm 450 V 160 mA SiO.sub.2 23.5 nm 450 V 160 mA 6th layer
TiO.sub.2 251.5 nm 360 V 105 mA TiO.sub.2 88.0 nm 360 V 105 mA 7th
layer SiO.sub.2 118.0 nm 450 V 160 mA SiO.sub.2 130.0 nm 450 V 160
mA Evaluation of performance of plastic lens Ar gas for Nb and
SiO.sub.2 Ar gas for Nb and SiO.sub.2 Gas used for ion assistance
Mixture of O.sub.2 and Ar (1:1) for TiO.sub.2 Mixture of O.sub.2
and Ar (1:1) for TiO.sub.2 Luminous reflectance (Y.sub.R), % 0.82%
0.82% Luminous transmittance (Y.sub.T), % 99.0% 99.0% Film
adhesiveness 100/100 100/100 Abrasion resistance UA UA to A Heat
resistance 95.degree. C. 100.degree. C. Alkali resistance UA UA to
A Impact resistance 0 0
[0077]
2TABLE 2 Example 3 Example 4 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 60 sec
40 sec Gas used Ar Ar Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer Nb 3.5 nm 150 V 100 mA Nb 4.0 nm
150 V 100 mA 1st layer SiO.sub.2 94.0 nm 450 V 160 mA SiO.sub.2
108.0 nm 450 V 160 mA 2nd layer Nb 3.5 nm 360 V 105 mA TiO.sub.2
52.5 nm 360 V 105 mA 3rd layer SiO.sub.2 94.0 nm 150 V 100 mA
SiO.sub.2 271.8 nm 450 V 160 mA 4th layer TiO.sub.2 225.5 nm 360 V
105 mA TiO.sub.2 38.6 nm 360 V 105 mA 5th layer SiO.sub.2 42.6 nm
450 V 160 mA SiO.sub.2 38.6 nm 450 V 160 mA 6th layer TiO.sub.2
249.0 nm 360 V 105 mA TiO.sub.2 242.8 nm 360 V 105 mA 7th layer
SiO.sub.2 117.0 nm 450 V 160 mA SiO.sub.2 119.0 nm 450 V 160 mA
Evaluation of performance of plastic lens Ar gas for Nb and
SiO.sub.2 Ar gas for Nb and SiO.sub.2 Gas used for ion assistance
Mixture of O.sub.2 and Ar (1:1) for TiO.sub.2 Mixture of O.sub.2
and Ar (1:1) for TiO.sub.2 Luminous reflectance (Y.sub.R), % 0.82%
0.68% Luminous transmittance (Y.sub.T), % 99.0% 99.3% Film
adhesiveness 100/100 100/100 Abrasion resistance UA UA to A Heat
resistance 95.degree. C. 100.degree. C. Alkali resistance UA UA
Impact resistance 0 0
[0078]
3TABLE 3 Example 5 Example 6 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 40 sec
40 sec Gas used Ar Ar Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer Nb 4.0 nm 150 V 100 mA Nb 3.5 nm
150 V 100 mA 1st layer SiO.sub.2 7.9 nm 450 V 160 mA SiO.sub.2
111.9 nm 450 V 160 mA 2nd layer TiO.sub.2 28.4 nm 360 V 105 mA Nb
3.5 nm 150 V 100 mA 3rd layer SiO.sub.2 49.0 nm 450 V 160 mA
SiO.sub.2 111.9 nm 450 V 160 mA 4th layer TiO.sub.2 116.5 nm 360 V
105 mA TiO.sub.2 25.2 nm 360 V 105 mA 5th layer SiO.sub.2 10.9 nm
450 V 160 mA SiO.sub.2 41.2 nm 450 V 160 mA 6th layer TiO.sub.2
110.8 nm 360 V 105 mA TiO.sub.2 245.0 nm 360 V 105 mA 7th layer
SiO.sub.2 125.5 nm 450 V 160 mA SiO.sub.2 119.3 nm 450 V 160 mA
Evaluation of performance of plastic lens Ar gas for Nb and
SiO.sub.2 Ar gas for Nb and SiO.sub.2 Gas used for ion assistance
Mixture of O.sub.2 and Ar (1:1) for TiO.sub.2 Mixture of O.sub.2
and Ar (1:1) for TiO.sub.2 Luminous reflectance (Y.sub.R), % 0.68%
0.68% Luminous transmittance (Y.sub.T), % 99.3% 99.3% Film
adhesiveness 100/100 100/100 Abrasion resistance UA to A UA Heat
resistance 100.degree. C. 95.degree. C. Alkali resistance UA to A
UA Impact resistance 0 0
[0079]
4TABLE 4 Example 7 Example 8 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 60 sec
60 sec Gas used Ar Ar Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer Nb 4.0 nm 150 V 100 mA Nb 4.0 nm
150 V 100 mA 1st layer SiO.sub.2 14.6 nm 450 V 160 mA SiO.sub.2
10.5 nm 450 V 160 mA 2nd layer Ta.sub.2O.sub.5 9.5 nm 420 V 120 mA
Ta.sub.2O.sub.5 26.0 nm 420 V 120 mA 3rd layer SiO.sub.2 292.0 nm
450 V 160 mA SiO.sub.2 54.2 nm 450 V 160 mA 4th layer
Ta.sub.2O.sub.5 66.8 nm 420 V 120 mA Ta.sub.2O.sub.5 94.0 nm 420 V
120 mA 5th layer SiO.sub.2 29.7 nm 450 V 160 mA SiO.sub.2 24.2 nm
450 V 160 mA 6th layer Ta.sub.2O.sub.5 124.9 nm 420 V 120 mA
Ta.sub.2O.sub.5 91.0 nm 420 V 120 mA 7th layer SiO.sub.2 131.2 nm
450 V 160 mA SiO.sub.2 134.1 nm 450 V 160 mA Evaluation of
performance of plastic lens Ar gas for Nb and SiO.sub.2 Ar gas for
Nb and SiO.sub.2 Gas used for ion assistance Mixture of O.sub.2 and
Ar (1:0.25) for Ta.sub.2O.sub.5 Mixture of O.sub.2 and Ar (1:0.25)
for Ta.sub.2O.sub.5 Luminous reflectance (Y.sub.R), % 0.80% 0.80%
Luminous transmittance (Y.sub.T), % 99.1% 99.1% Film adhesiveness
100/100 100/100 Abrasion resistance UA UA Heat resistance
95.degree. C. 95.degree. C. Alkali resistance UA UA Impact
resistance 0 0
[0080]
5TABLE 5 Example 9 Example 10 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 60 sec
60 sec Gas used Ar Ar Optical Film Setting values Optical Film Type
of film thickness for ion gun Type of film thickness for ion gun
Basic layer Nb 4.0 nm 150 V 100 mA Nb 4.0 nm 150 V 100 mA 1st layer
SiO.sub.2 33.5 nm 450 V 160 mA SiO.sub.2 10.5 nm 450 V 160 mA 2nd
layer Nb.sub.2O.sub.5 4.5 nm 360 V 105 mA Nb.sub.2O.sub.5 26.4 nm
360 V 105 mA 3rd layer SiO.sub.2 292.0 nm 450 V 160 mA SiO.sub.2
54.2 nm 450 V 160 mA 4th layer Nb.sub.2O.sub.5 23.9 nm 360 V 105 mA
Nb.sub.2O.sub.5 94.0 nm 360 V 105 mA 5th layer SiO.sub.2 46.2 nm
450 V 160 mA SiO.sub.2 24.2 nm 450 V 160 mA 6th layer
Nb.sub.2O.sub.5 243.8 nm 360 V 105 mA Nb.sub.2O.sub.5 91.0 nm 360 V
105 mA 7th layer SiO.sub.2 121.2 nm 450 V 160 mA SiO.sub.2 134.1 nm
450 V 160 mA Evaluation of performance of plastic lens Ar gas for
Nb and SiO.sub.2 Ar gas for Nb and SiO.sub.2 Gas used for ion
assistance Mixture of O.sub.2 and Ar (1:0.11) for Nb.sub.2O.sub.5
Mixture of O.sub.2 and Ar (1:0.11) for Nb.sub.2O.sub.5 Luminous
reflectance (Y.sub.R), % 0.68% 0.68% Luminous transmittance
(Y.sub.T), % 99.3% 99.3% Film adhesiveness 100/100 100/100 Abrasion
resistance UA UA to A Heat resistance 95.degree. C. 100.degree. C.
Alkali resistance UA UA to A Impact resistance 0 0
[0081]
6TABLE 6 Example 11 Example 12 Plastic lens substrate Diethylene
glycol bisallyl carbonate Diethylene glycol bisallyl carbonate Hard
coat layer Layer A Layer A Ion Acceleration Voltage for
Pretreatment 150 V 150 V Current 100 mA 100 mA Exposure time 40 sec
40 sec Gas used Ar Ar Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer Nb 3.5 nm 150 V 100 mA Nb 4.0 nm
150 V 100 mA 1st layer SiO.sub.2 111.6 nm 450 V 160 mA SiO.sub.2
10.5 nm 450 V 160 mA 2nd layer Nb 3.5 nm 150 V 100 mA
Nb.sub.2O.sub.5 26.4 nm 360 V 105 mA 3rd layer SiO.sub.2 111.6 nm
450 V 160 mA SiO.sub.2 54.2 nm 450 V 160 mA 4th layer
Nb.sub.2O.sub.5 24.9 nm 360 V 105 mA Nb.sub.2O.sub.5 94.0 nm 360 V
105 mA 5th layer SiO.sub.2 39.5 nm 450 V 160 mA SiO.sub.2 24.2 nm
450 V 160 mA 6th layer Nb.sub.2O.sub.5 236.3 nm 360 V 105 mA
Nb.sub.2O.sub.5 91.0 nm 360 V 105 mA 7th layer SiO.sub.2 120.2 nm
450 V 160 mA SiO.sub.2 134.5 nm 450 V 160 mA Evaluation of
performance of plastic lens Ar gas for Nb and SiO.sub.2 Ar gas for
Nb and SiO.sub.2 Gas used for ion assistance Mixture of O.sub.2 and
Ar (1:0.11) for Nb.sub.2O.sub.5 Mixture of O.sub.2 and Ar (1:0.11)
for Nb.sub.2O.sub.5 Luminous reflectance (Y.sub.R), % 0.68% 0.68%
Luminous transmittance (Y.sub.T), % 99.3% 99.3% Film adhesiveness
100/100 100/100 Abrasion resistance UA UA to A Heat resistance
95.degree. C. 100.degree. C. Alkali resistance UA UA to A Impact
resistance 0 0
[0082]
7TABLE 7 Comparative Example 1 Comparative Example 2 Plastic lens
substrate Diethylene glycol bisallyl carbonate Diethylene glycol
bisallyl carbonate Hard coat layer Layer A Layer A Ion Acceleration
Voltage for Pretreatment no pretreatment no pretreatment Current
Exposure time Gas used Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer -- -- -- -- -- -- -- -- 1st layer
SiO.sub.2 31.5 nm -- -- SiO.sub.2 22.0 nm -- -- 2nd layer TiO.sub.2
3.5 nm -- -- TiO.sub.2 29.0 nm -- -- 3rd layer SiO.sub.2 238.0 nm
-- -- SiO.sub.2 48.5 nm -- -- 4th layer Nb.sub.2O.sub.5 23.5 nm --
-- TiO.sub.2 98.0 nm -- -- 5th layer SiO.sub.2 425.0 nm -- --
SiO.sub.2 23.5 nm -- -- 6th layer Nb.sub.2O.sub.5 251.5 nm -- --
TiO.sub.2 88.0 nm -- -- 7th layer SiO.sub.2 118.0 nm -- --
SiO.sub.2 130.0 nm -- -- Evaluation of performance of plastic lens
Luminous reflectance (Y.sub.R), % 1.1% 1.1% Luminous transmittance
(Y.sub.T), % 98.7% 98.7% Film adhesiveness 95/100 95/100 Abrasion
resistance B B to C Heat resistance 70.degree. C. 70.degree. C.
Alkali resistance B B to C Impact resistance x 0
[0083]
8TABLE 8 Comparative Example 3 Comparative Example 4 Plastic lens
substrate Diethylene glycol bisallyl carbonate Diethylene glycol
bisallyl carbonate Hard coat layer Layer A Layer A Ion Acceleration
Voltage for Pretreatment no pretreatment no pretreatment Current
Exposure time Gas used Optical Film Setting values Optical Film
Setting values Type of film thickness for ion gun Type of film
thickness for ion gun Basic layer -- -- -- -- -- -- -- -- 1st layer
SiO.sub.2 14.6 nm -- -- SiO.sub.2 10.5 nm -- -- 2nd layer
Ta.sub.2O.sub.5 9.5 nm -- -- Ta.sub.2O.sub.5 26.4 nm -- -- 3rd
layer SiO.sub.2 292.0 nm -- -- SiO.sub.2 54.2 nm -- -- 4th layer
Ta.sub.2O.sub.5 66.8 nm -- -- Ta.sub.2O.sub.5 94.0 nm -- -- 5th
layer SiO.sub.2 29.7 nm -- -- SiO.sub.2 24.2 nm -- -- 6th layer
Ta.sub.2O.sub.5 124.9 nm -- -- Ta.sub.2O.sub.5 91.0 nm -- -- 7th
layer SiO.sub.2 131.2 nm -- -- SiO.sub.2 134.1 nm -- -- Evaluation
of performance of plastic lens Luminous reflectance (Y.sub.R), %
1.2% 1.2% Luminous transmittance (Y.sub.T), % 98.6% 98.6% Film
adhesiveness 95/100 95/100 Abrasion resistance B B to C Heat
resistance 70.degree. C. 75.degree. C. Alkali resistance B B Impact
resistance x x
[0084] As shown in Tables 1 to 6, the plastic lenses of Examples 1
to 12 had an extremely small luminous reflectance of from 0.68 to
0.82% and had a high luminance transmittance of from 99.0 to 99.3%.
In addition, their film adhesiveness, abrasion resistance, heat
resistance, alkali resistance and impact resistance were good.
[0085] In contrast, the plastic lenses of Comparative Examples 1 to
4 had a high luminous reflectance of from 1.1 to 1.2% and had a low
luminance transmittance of from 98.6 to 98.7%, as shown in Tables 7
and 8. In addition, their film adhesiveness, abrasion resistance,
heat resistance, alkali resistance and impact resistance were
inferior to those in Examples 1 to 12.
[0086] As described in detail hereinabove, the optical element of
the invention has an antireflection film, in which the reflectance
is small, and the transmittance is high, and, in addition, it has
excellent adhesiveness between the plastic substrate and the
antireflection film, abrasion resistance, heat resistance, alkali
resistance and impact resistance.
* * * * *