Optical lens and mold for molding the same

An optical lens press-molded so that within at least the optically effective diameter thereof, the thickness thereof may become greater from the center of the optical axis thereof toward the marginal portion of the lens, characterized in that at least one of the both lens surfaces thereof is a spherical or aspherical concave lens continuous from a transferred surface formed so that in the area outside the optically effective diameter thereof, the thickness of the lens may be limited away from the extension of a curved surface of a radius of curvature setting the optically effective diameter toward the outer diameter of the lens, and forming the transferred surface up to at least the required outer diameter of the lens, and a free surface portion is left outside the outer diameter of the lens during molding.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an optical lens press-molded so that within at 
least the optically effective diameter thereof, the thickness thereof may 
become greater from the center of the optical axis thereof toward the 
marginal portion of the lens, for example, an optical lens having a 
spherical or aspherical concave lens surface, such as a concave lens, a 
meniscus lens or a toric lens, and to a mold for molding the same. 
2. Related Background Art 
In recent years, there has been adopted a system in which by the use of 
upper and lower mold members having a molding surfaces formed with 
predetermined surface accuracy, a glass blank, for example, a glass blank 
pre-molded into a certain degree of shape and surface accuracy, is 
contained between those molding surfaces to thereby press-mold an optical 
lens under-heating. Thereby, it is contrived to make post-working such as 
grinding and polishing unnecessary and to improve the productivity of 
optical elements during the manufacture thereof. 
Many methods of manufacturing optical elements as described above are 
disclosed in considerable number of patent publications, but almost all of 
them are concerned with the molding of convex lenses, and regarding 
concave lenses, an embodiment thereof is only disclosed in Japanese 
Laid-Open Patent Application No. 59-116137, Japanese Laid-Open Patent 
Application No. 59-121124, Japanese Laid-Open Patent Application No. 
59-121126, Japanese Laid-Open Patent Application No. 59-123629 and 
Japanese Laid-Open Patent Application No. 60-118642. 
The optical lenses disclosed in these publications are of simple concave 
lens shape or are molded with an escape portion for surplus glass left 
outside the optical effective diameter thereof, and in these publications, 
there is no description as to how the partial shape of the optical lens in 
the outside of the above-mentioned optical effective diameter affects the 
quality of the lens. 
Generally, a problem in the molding of a concave lens is that the shape 
transferability of the optically functioning surface thereof is bad. 
Conceivable factors which govern that shape transferability are pressing 
pressure, temperature, cooling condition, mold material, glass material, 
etc., but besides these, the shape of the cavity of the mold, particularly 
the shape of the portion outside the optical effective diameter which 
constitutes the optically functioning surface, is greatly influential. 
Usually, to transfer the shape of the cavities in the upper and lower mold 
members of a mold for molding to an optical lens blank, it is necessary 
that during press molding, the glass and the molding surfaces of the mold 
members be reliably in contact with each other. A concave lens is such 
that as a feature of its shape, the thickness of the lens becomes 
gradually greater from the center of the optical axis thereof toward the 
outer periphery thereof and therefore, in the press molding process, 
pressure applied to the mold for molding is dispersed and it is difficult 
for this pressure to be transmitted to the outer peripheral portion of the 
optical lens blank. 
Therefore, near the required outer diameter of the optical lens, the 
optical lens blank and the molding surfaces of the mold do not contact 
with each other, and the shape transfer within a necessary range (at least 
within the required outer diameter of the optical lens to be molded) is 
impossible, or even if tentative shape transfer to the optical lens blank 
is brought about by the contact of the optical lens blank with the molding 
surfaces, the transfer pressure within the necessary range will not be 
secured sufficiently and shape transfer of required accuracy will not be 
done even within the optical effective diameter. 
In order to cope with this, there is a method of pressing down the outer 
peripheral portion of a molded article by the inner peripheral portion of 
a drum mold surrounding upper and lower mold members to thereby regulate 
the outer diameter of the lens and secure the transfer pressure of the 
outer peripheral portion thereof, but in this case, glass comes into the 
sliding gap between the upper and lower mold members and the drum mold, 
and this leads to the adverse effect that when the molded optical lens is 
taken out of the mold, a part thereof breaks and broken pieces resulting 
therefrom injure the molding surfaces to thereby shorten the life of the 
mold. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above-noted 
circumstances and the object thereof is to provide an optical lens in 
which sufficient shape transferability within a necessary range is secured 
when the optical lens is to be obtained by directly press molding without 
post-processing such as polishing being done, and to provide a mold for 
molding the optical lens which can display such shape transferability and 
moreover is free of burrs in the molded article and in which any partial 
injury is avoided and the inconvenience of injuring the molding surfaces 
of mold members is avoided. 
To achieve the above object, according to the present invention, an optical 
lens press-molded so that at least within the optically effective diameter 
thereof, the thickness thereof may become greater from the center of the 
optical axis thereof toward the marginal portion of the lens is 
characterized in that at least one of the two lens surfaces thereof is a 
spherical or aspherical concave lens surface which is continuous from a 
transferred surface formed so that in the area outside the optically 
effective diameter thereof, the thickness of the lens may be limited away 
from the extension of a curved surface of a radius of curvature setting 
the optically effective diameter toward the outer diameter of the lens and 
forms said transferred surface up to at least the required outer diameter 
of the lens, and a free surface portion is left outside said outer 
diameter of the lens during molding. 
Also, a mold for molding the optical lens of the present invention 
comprises an upper mold member and a lower mold member having their 
molding surfaces opposed to each other, and is characterized in that the 
molding surface of at least one of the mold members is comprised of a 
first transfer surface corresponding to a curved surface of a radius of 
curvature setting the optically effective diameter of the spherical or 
aspherical concave lens surface of the optical lens molded by the two mold 
members, and a second transfer surface formed so that in the transfer area 
outside said optically effective diameter, the thickness of the lens may 
be limited away from the extension of said curved surface toward the outer 
diameter of the lens, continuous from the first transfer surface and 
formed up to at least the required outer diameter of the lens, the shape 
of the second transfer surface is set such that in the press-molded state, 
the outer peripheral portion of the blank of said optical lens forms a 
free surface portion at a location beyond the second transfer surface, and 
a required clearance is provided on the outer peripheral side of said 
molding surface. 
Accordingly, in the present invention, shape transferability of high 
accuracy is secured up to the required area (at least the predetermined 
outer diameter of the lens) outside the optically effective diameter of 
the optical lens, and an optical lens having an excellent concave lens 
surface is obtained. Also, in the mold for molding such optical lens, such 
regulation that gives transfer pressure to the blank of the optical lens 
is done by the second transfer surface during press molding and 
accordingly, sufficient shape transfer ability is displayed and moreover, 
the creation of burrs is avoided and therefore, when the molded article is 
to be taken out of the mold, there is no partial damage to the optical 
lens and there is no possibility of injuring the molding surfaces of the 
mold members and thus, the life of the mold can be kept long.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Some embodiments of the present invention will hereinafter be described in 
detail with reference to the drawings. In FIG. 1, an optical lens 100 made 
of glass according to the present invention is specifically shown with 
respect to the cross-sectional shape thereof. The optical lens 100 is one 
press-molded so that the thickness thereof may become greater from the 
center of the optical axis thereof toward the marginal portion of the 
lens, and in this embodiment, it is a concave lens formed with two concave 
lens surfaces 102 and 104 having an optically effective diameter P about 
the optical axis thereof. 
The concave lens surfaces 102 and 104 are spherical (or aspherical) concave 
lens surfaces continuous from transferred surfaces 106 and 108 formed so 
that in the area outside the optically effective diameter P, the thickness 
of the lens may be limited away from the extension of a curved surface of 
a radius of curvature setting the optically effective diameter P toward 
the outer diameter of the lens, and forming the transferred surfaces 106 
and 108 up to at least the required outer diameter of the lens, and 
outside the outer diameter of the lens, free surface portions 114 are left 
during molding. That is, the shapes of the transferred surfaces 106 and 
108 are designed such that at least the spacing r at a location outside 
the outer diameter of the lens is smaller than the spacing Q between the 
extensions 110 and 112 of curved surfaces of a radius of curvature forming 
the concave lens surfaces 102 and 104. For this reason, in the present 
invention, the transferred surfaces 106 and 108 in the area outside the 
optically effective diameter P are comprised of flat surfaces or curved 
surfaces smoothly continuous from curved surfaces of a radius of curvature 
setting the optically effective diameter P, or a combination thereof. 
FIG. 2 shows an embodiment of a mold for molding the concave lens of the 
above-described embodiment. In FIG. 2, an upper mold member 122 and a 
lower mold member 124 are fitted in a drum mold 120 so as to be vertically 
slidable, and a cavity 126 can be formed by molding surfaces 128 and 130 
opposed to each other. These molding surfaces 128 and 130 are provided 
with first transfer surfaces 128A and 130A and second transfer surfaces 
128B and 130B for forming the optically functioning surface (including the 
above-described optically effective diameter P and transferred surfaces 
106, 108) of an optical lens to be molded. 
The first transfer surfaces 128A and 130A correspond to curved surfaces 136 
and 138 of a radius of curvature setting the optically effective diameter 
P of the concave lens surface, and the second transfer surfaces 128B and 
130B are smoothly continuous from the first transfer surfaces as by arcs 
as shown so that in the transfer area outside the optically effective 
diameter P, the thickness of the lens may be limited away from the 
extensions of said curved surfaces toward the outer diameter of the lens, 
and are formed up to at least the required outer diameter of the lens (in 
the present embodiment, beyond it). 
As a result, in a press molding state (see FIG. 3), the outer peripheral 
portion of the blank (glass gob) 139 of the optical lens has its movement 
regulated by the second transfer surfaces 128B and 130B so as to form free 
surface portions 114 at locations beyond the second transfer surfaces 128B 
and 130B. Therefore, in this mold, required transfer pressure is secured 
in the transfer area (from the center of the optical axis to a location 
beyond at least the outer diameter of the lens). Moreover, in this case, a 
required clearance S is provided on the outer peripheral side of the 
aforementioned molding surfaces, whereby even when press molding is 
completed, there is no possibility of the glass blank 139 coming into the 
sliding gap between the upper and lower mold members and the drum mold to 
form so-called burrs. The optical lens 100 formed in this manner is used 
intactly or with the marginal portion thereof cut from the state of FIG. 4 
to the state of FIG. 5 in accordance with the outer diameter of the lens. 
The clearance S is set to such a degree of size that when in the press 
molding state by the upper mold member 122 and the lower mold member 124, 
the outer peripheral portion of the glass blank 139 moves toward the inner 
peripheral surface 140 of the drum mold 120, the glass blank 139 does not 
come into the sliding gap between the upper and lower mold members and the 
drum mold, and may preferably be set to such a degree that as shown in 
FIG. 3, for example, the free surface portions of the glass blank 139 do 
not contact with the inner peripheral surface 140. 
(Embodiment 1) 
A mode of practice based on specific numerical values will now be described 
in detail with respect to the above-described embodiment of the present 
invention. Here, as the glass blank for forming the optical lens, use is 
made of SK12 (n.sub.d =1.58313, .nu..sub.d =59.4, Tg=550.degree. C., 
At=588.degree. C.), and this is worked in advance into a disc-like shape 
having an outer diameter of .phi.18 mm and a thickness of 9.2 mm. An 
optical lens as described above having a radius of curvature R.sub.1 
=R.sub.2 =30 mm, an optically effective diameter P=.phi.20 mm and a center 
thickness=2 mm and the both surfaces of which are concave is molded from 
this glass blank. 
The mold for molding this optical lens has the molding surface 128 of its 
upper mold member 122 and the molding surface 130 of its lower mold member 
124 worked into mirror surfaces, and those molding surfaces are of a 
convex shape in which the portion of a diameter=.phi.20 mm about the 
optical axis is at least the area corresponding to the optically effective 
diameter P of the optical lens 100, i.e., the first transfer surfaces 128A 
and 130A and the radius of curvature R.perspectiveto.30 mm. Also, the area 
outside the optically effective diameter to the area of an outer 
diameter=.phi.30 mm, i.e., the second transfer surfaces 128B and 130B, are 
formed by toric surfaces of a shorter radius R=4.5 so that the thickness 
of the lens may be limited away from the extension of curved surfaces of a 
curvature forming the first transfer surfaces toward the outer diameter of 
the lens, and are smoothly continuous. 
Thus, the mold is heated to e.g. 630.degree. C. by suitable heating means 
(not shown) with the glass blank 139 placed on the molding surface 130 of 
the lower mold member 124, as shown in FIG. 2, and after the glass blank 
sufficiently rises in temperature, the upper mold member 122 is lowered to 
thereby effect press molding. FIG. 3 shows the state in which press 
molding has been completed as described above, and here, the cooling of 
the mold members is continued until the temperature of the mold falls to 
550.degree. C. (Tg). Thereafter, the upper mold member 122 is raised and 
the optical lens molded into the shape shown in FIG. 2 is taken out. 
Therefore, in this mold, required transfer pressure is secured in the 
transfer area thereof (from the center of the optical axis to at least a 
location beyond the outer diameter of the lens). Moreover, in this case, a 
required clearance is provided on the outer peripheral side of the 
above-described molding surfaces, whereby even when press molding has been 
completed, there is no possibility of the glass blank coming into the 
sliding gap between the upper and lower mold members and the drum mold to 
form so-called burrs. 
The optical lens 100 molded in this manner was of a good quality in which 
the outer diameter=.phi.26 mm, the center thickness=2 mm and the accuracy 
of the optically functioning surface in the area of the optically 
effective diameter was N : 2 and contour map of the surface: 0.5. 
Particularly, the transferred surface 106 outside the optically effective 
diameter R is sufficient in the transferability during molding and molded 
highly accurately and therefore, when it is adsorbed by a vacuum adsorbing 
mechanism 17 having a flat adsorbing surface as shown in FIG. 6 when the 
molded optical lens 100 is taken out of the mold, the airtightness between 
the contact portion 18 thereof and the above-mentioned adsorbing surface 
is good and the work of taking out the optical lens can be done reliably. 
(Embodiment 2) 
A second embodiment of the present invention will now be specifically and 
numerically described with reference to FIG. 7. As a glass blank for 
forming an optical lens, SK12 is used as in Embodiment 1, and this is 
worked in advance into a disc-like shape having an outer diameter of 
.phi.18 mm and a thickness of 7.65 mm. As in Embodiment 1, an optical lens 
200 having a radius of curvature R.sub.1 =R.sub.2 =30 mm, an optically 
effective diameter P=.phi.20 mm and a center thickness=2 mm and the both 
surfaces of which are concave is molded from this glass blank. 
A mold used here is comprised of an upper mold member 222 and a lower mold 
member 224, and a drum mold 220 in which these are slidably fitted as 
shown in FIG. 7, and the molding surfaces 228 and 230 of the respective 
mold members are finished into mirror surfaces. Each molding surface is of 
a convex shape having a radius of curvature R.perspectiveto.30 with the 
portion of .phi.20 mm from the center of the optical axis as the area 
228A, 230A of the optically effective diameter. Also, transfer areas 228B 
and 230B extending from the outside of the optically effective diameter 
P=.phi.20 mm to at least the lens outer diameter=.phi.30 mm are formed by 
a conical surface having a vertical angle 120.degree., and outside the 
optically effective diameter P, there is formed a circumscribed circle of 
a small diameter which smoothly links the two together (in FIG. 7, the 
circumscribed circle is omitted to make the portion of continuation with 
the conical surface clear, and that portion is indicated by C). 
The mold is heated to 630.degree. C. by suitable heating means with the 
disc-shaped glass blank placed on the molding surface 230 of the lower 
mold member 224, and after the glass blank sufficiently rises in 
temperature, the upper mold member 222 is lowered to thereby effect press 
molding. In the state shown in FIG. 7, the cooling of the mold is 
continued until the temperature of the mold falls to 550.degree. C. (Tg), 
whereafter the upper mold member is raised and the molded optical lens 200 
is taken out. 
Therefore, in this mold, required transfer pressure is secured in the 
transfer area thereof (from the center of the optical axis to at least a 
location beyond the outer diameter of the lens). Moreover, in this case, a 
required clearance is provided on the outer peripheral side of the 
above-mentioned molding surface, whereby even when press molding has been 
completed, there is no possibility of the glass blank coming into the 
sliding gap between the upper and lower mold members and the drum mold to 
form so-called burrs. The optical lens 200 molded in this manner was of a 
good quality in which the outer diameter=.phi.26 mm, the center 
thickness=2 mm and the surface accuracy of the transfer surface was N: 2 
and contour map of the surface: 0.5. 
(Embodiment 3) 
In this embodiment, there is adopted a preparatory molding system in which 
Lak12 (n.sub.d =1.67790, .nu..sub.d =55.3, Tg=554.degree. C., 
At=596.degree. C.) is molten as a glass blank for forming an optical lens 
and a predetermined quantity of it is flowed out into a receiving mold to 
thereby obtain a glass blank (glass gob) and by the use of it, an optical 
lens is molded. The optical lens molded here is a concave meniscus lens in 
which the radius of curvature of the concave surface side is R.sub.1 =30 
mm, the radius of curvature of the convex surface side is R.sub.2 =80 mm, 
the optically effective diameter P=.phi.20 mm and the center thickness=2 
mm. 
(Third Embodiment) 
FIGS. 8 and 9 show a mold according to a third embodiment of the present 
invention for molding an optical lens from the above-described glass 
blank. In this embodiment, the mold is comprised of an upper mold member 
322, a lower mold member 324 and a drum mold 320, and a glass blank 339 is 
placed on the molding surface of the lower mold member 324. The molding 
surface 328 of the upper mold member 322, as in the aforedescribed 
Embodiment 1, is of a convex shape in which the portion of .phi.20 mm from 
the center of the optical axis has a radius of curvature 
R.perspectiveto.30 mm as a transfer area 328A of the optically effective 
diameter, and a transfer area 328B extending from the outside of the 
optically effective diameter=.phi.20 mm to the lens outer diameter=.phi.30 
mm is formed by a concave surface smoothly continuous from the transfer 
area 328A by a circumscribed are of a radius R=30 mm. On the other hand, 
the molding surface 330 of the lower mold member 324 is worked into a 
concave surface of a radius of curvature R.perspectiveto.80 mm. 
Thus, the mold is heated to 620.degree. C. by suitable heating means with 
the glass blank 339 of a weight 4.95 g placed on the molding surface of 
the lower mold member 324, as shown in FIG. 8, and after the glass blank 
339 sufficiently rises in temperature, the upper mold member 322 is 
lowered to thereby effect press molding. 
FIG. 9 shows a state in which press molding has been completed, and in this 
state, the mold was cooled down until the temperature of the mold fell to 
554.degree. C. (Tg), whereafter the upper mold member 322 was raised and 
the molded optical lens 300 was taken out. Therefore, in this mold, 
required transfer pressure is secured in the transfer area thereof (from 
the center of the optical axis to at least a location beyond the outer 
diameter of the lens). Moreover, in this case, a required clearance is 
provided on the outer peripheral side of the above-mentioned molding 
surface, whereby even when press molding has been completed, there is no 
possibility of the glass blank coming into the sliding gap between the 
upper and lower mold members and the drum mold to form so-called burrs. 
The optical lens 300 molded in this manner was of a good quality in which 
the outer diameter=.phi.26 mm, the center thickness=2 mm and the accuracy 
of the transfer surface within the optically effective diameter was N: 3 
and contour map of the surface: 0.5. 
(Embodiment 4) 
In a fourth embodiment shown in FIG. 10, upper and lower mold members 422 
and 424 are provided with molding surfaces in which first transfer 
surfaces 428A, 430A in which both surfaces of an optically effective 
diameter P=.phi.15 mm are convexly curved surfaces of a radius of 
curvature R=35 mm and second transfer surfaces 428B, 430B therefrom to a 
diameter=.phi.30 mm larger than the outer diameter are smoothly continuous 
to each other, and the second transfer surfaces each are a toric surface 
of a shorter radius R=200. Therefore, in this mold, required transfer 
pressure is secured in the transfer area thereof (from the center of the 
optical axis to at least a location beyond the outer diameter of the 
lens). Moreover, in this case, a required clearance is provided on the 
outer peripheral side of the above-mentioned molding surface, whereby even 
when press molding has been completed, there is no possibility of the 
glass blank coming into the sliding gap between the upper and lower mold 
members and the drum mold to form so-called burrs. The optical lens 
(biconcave lens) 400 molded by such a mold has a free surface portion on 
the outer periphery thereof immediately after the molding. 
(Embodiment 5) 
In a fifth embodiment shown in FIG. 11, an upper mold member 522 is 
provided with a molding surface in which a convexly curved first transfer 
surface 528A in which an area of an optically effective diameter P=.phi.18 
mm is a convexly curved surface of a radius of curvature R=10 mm and a 
second transfer surface 528B therefrom to a diameter=.phi.30 mm larger 
than the outer diameter of the lens are smoothly continuous to each other 
as by a circumscribed arc of a small diameter (in FIG. 11, only the 
location thereof being indicated by a point C), and a second transfer 
surface is such that the portion thereof from the outside of the optically 
effective diameter to a diameter=.phi.24 mm is formed by a flat surface 
continuous from the above-mentioned circumscribed are and the portion from 
the diameter=.phi.24 mm to a diameter=.phi.30 mm is formed by a toric 
surface of a shorter radius R=7. At least the transfer area of the molding 
surface 530 of a lower mold member 524 is comprised of the concavely 
curved surface of the optical lens having a required diameter. Therefore, 
in this mold, required transfer pressure is secured in the transfer area 
thereof (from the center of the optical axis to at least a location beyond 
the outer diameter of the lens). Moreover, in this case, a required 
clearance is provided on the outer peripheral side of the above-mentioned 
molding surface, whereby even when press molding has been completed, there 
is no possibility of the glass blank coming into the sliding gap between 
the upper and lower mold members and the drum mold to form so-called 
burrs. An optical lens (a lens of which one surface is concave) 500 molded 
by such a mold has a free surface portion on the outer periphery thereof 
immediately after the molding. 
(Embodiment 6) 
In a sixth embodiment shown in FIG. 12, upper and lower mold members 622 
and 624 are provided with molding surfaces in which first transfer 
surfaces 628A, 630A in which both surfaces of an optically effective 
diameter P=.phi.15 mm are convexly curved surfaces of a radius of 
curvature R=15 mm and second transfer surfaces 628B, 630B therefrom to a 
diameter =.phi.30 mm larger than the outer diameter of the lens are 
smoothly continuous to each other, and the second transfer surfaces are 
flat surfaces continuous from the first transfer surfaces through a 
circumscribed arc of a small diameter (not shown). Therefore, in this 
mold, required transfer pressure is secured in the transfer area thereof 
(from the center of the optical axis to at least a location beyond the 
outer diameter of the lens). Moreover, in this case, a required clearance 
is provided on the outer peripheral side of the above-described molding 
surfaces, whereby even when press molding has been completed, there is no 
possibility of the glass blank coming into the sliding gap between the 
upper and lower mold members and the drum mold to form so-called burrs. An 
optical lens (a lens of which the both surfaces are concave) 600 molded by 
such a mold has a free surface portion on the outer periphery thereof 
immediately after the molding. 
(Embodiment 7) 
In a seventh embodiment shown in FIG. 13, upper and lower mold members 722 
and 724 are provided with molding surfaces in which first transfer 
surfaces 728A, 730A in which both surfaces of an optically effective 
diameter P=.phi.15 mm are convexly curved surfaces of a radius of 
curvature R=30 mm and second transfer surfaces 728B, 730B of a 
diameter=.phi.30 mm larger than the outer diameter of the lens are 
smoothly continuous to each other, and the second transfer surfaces are 
such that the portion thereof from the outside of the optically effective 
diameter to a diameter=.phi.27 mm is formed by a toric surface of a 
shorter radius R=10 circumscribed to the transfer surface 728A and the 
portion thereof from the diameter =.phi.27 mm to a diameter=.phi.30 mm is 
formed by a flat surface continuous from the toric surface through a 
circumscribed arc of a small diameter (in FIG. 13, the location thereof 
being indicated by C). Therefore, in this mold, required transfer pressure 
is secured in the transfer area thereof (from the center of the optical 
axis to at least a location beyond the outer diameter of the lens). 
Moreover, in this case, a required clearance is provided on the outer 
peripheral side of the above-described molding surfaces, whereby even when 
press molding has been completed, there is no possibility of the glass 
blank coming into the sliding gap between the upper and lower mold members 
and the drum mold to form so-called burrs. An optical lens (a lens of 
which the both surfaces are convex) molded by such a mold has a free 
surface portion on the outer periphery thereof immediately after the 
molding. 
(Comparative Example 1) 
FIG. 14 shows the manner of molding a prior-art concave lens mentioned as a 
comparative example in order to make the features of the present invention 
clear. In FIG. 14, the reference numeral 14 designates an upper mold 
member having a molding surface formed with a predetermined radius of 
curvature R.congruent.30, and the reference numeral 15 denotes a lower 
mold member having the same molding surface as that of the upper mold 
member, the reference numeral 16 designates a drum mold, and the reference 
numeral 10 denotes a molded lens. When the optically functioning surfaces 
are transferred to a glass blank by such simple molding surfaces, the 
following disadvantages occur. The same material as that in Embodiment 1 
is used as the glass blank, and the optically effective diameter of the 
molded lens 10 is also set to the same as that in Embodiment 1. 
Thus, the glass blank was placed on the molding surface of the lower mold 
member 15, the mold was heated to 630.degree. C. by suitable heating 
means, and after the glass sufficiently rose in temperature, the upper 
mold member 14 was lowered to thereby effect press molding. In a state in 
which press molding was completed, the mold was cooled down until the 
temperature of the mold fell to 550.degree. C. (Tg), whereafter the upper 
mold member was raised and the optical lens 10 was taken out. As a result, 
the optical lens 10 formed an extreme contour map of the surface on the 
marginal portion thereof and the shapes of the optically functioning 
surfaces were not sufficiently transferred. Therefore, the accuracy of the 
transfer surfaces within the optically effective diameter was bad, and 
when the optical lens was taken out of the mold, adsorption was attempted 
by the use of the vacuum adsorbing mechanism 17 of FIG. 6 as in Embodiment 
1, but the airtightness of the contact portion 18 was bad and adsorption 
and taking-out were impossible. This is considered to be because even 
within the required outer diameter of the lens, transfer pressure is not 
sufficiently applied and therefore the contact portion 18 becomes a free 
surface portion and does not maintain a predetermined shape. 
The shape of the first transfer surface within the optically effective 
diameter of the optical lens of the present invention may be spherical or 
aspherical, and the shape of the second transfer surface outside the 
optically effective diameter may be spherical, toric, conical or the like, 
but of course, may be other smooth surface shape such as an amorphous 
continuous surface if it is such a shape that can maintain the transfer 
pressure to at least the outer diameter of the lens by the viscoelasticity 
of glass during molding and suppress the movement of the outer peripheral 
portion of the glass blank within the mold. 
According to the present invention, as described above in detail, in an 
optical lens press-molded so that within at least the optically effective 
diameter, the thickness may become greater from the center of the optical 
axis toward the marginal portion of the lens, at least one of the two lens 
surfaces thereof is a spherical or aspherical concave lens surface 
continuous from a transferred surface formed so that in the area outside 
the optically effective diameter thereof, the thickness of the lens may be 
limited away from the extension of a curved surface of a radius of 
curvature setting the optically effective diameter toward the outer 
diameter of the lens, and forming said transferred surface to at least the 
required outer diameter of the lens, and since a free surface portion is 
left outside the outer diameter of the lens during molding, sufficient 
shape transferability within a necessary range can be secured when the 
optical lens is directly obtained by press molding without any 
post-treatment such as polishing being done. 
Also, the mold of the present invention comprises an upper mold member and 
a lower mold member having their molding surfaces opposed to each other, 
and the molding surface of at least one of the mold members is comprised 
of a first transfer surface corresponding to a curved surface of a radius 
of curvature setting the optically effective diameter of the spherical or 
aspherical concave lens surface of an optical lens press-molded by the two 
mold members, and a second transfer surface formed so that in the transfer 
area outside said optically effective diameter, the thickness of the lens 
may be limited away from the extension of said curved surface toward the 
outer diameter of the lens, continuous from the first transfer surface and 
formed up to at least the required outer diameter of the lens, and the 
shape of the second transfer surface is set such that in the press-molded 
state, the outer peripheral portion of the blank of said optical lens 
forms a free surface portion at a location beyond the second transfer 
surface, and a 5 required clearance is provided on the outer peripheral 
side of said molding surface. Therefore, the shape transferability to the 
molded blank can be displayed during molding and moreover, the molded 
article is free of burrs, and partial damage is avoided when the 10 molded 
article is taken out of the mold and also, it is possible to avoid the 
inconvenience that the molding surfaces of the mold members are injured.