Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-01-28
2002-10-29
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S275700, C156S279000, C156S305000, C156S345420, C156S276000
Reexamination Certificate
active
06471814
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a piano lens particularly, suitable for use in a screen of a back projection type projector.
In recent years, as a large screen display used for a high definition television or a theater, a back projection type projector using a liquid crystal light bulb or a CRT has been actively developed.
FIG. 30
shows a schematic configuration of a related art back projection type projector.
Referring to
FIG. 30
, there is shown a box type projector in which image light L projected from an image projecting unit
101
is reflected by a reflecting mirror
102
to be introduced to a transmission screen
105
. The transmission screen
105
is composed of a Fresnel lens
103
which is generally combined with a vertically extending lenticular lens
104
. Image light L incident on the backface of the transmission screen
105
is substantially collimated through the Fresnel lens
103
, and the parallel rays of image light L are diffused mainly in the horizontal direction through the lenticular lens
104
.
As shown in
FIGS. 31A and 31B
, the lenticular lens
104
has on its back side (light outgoing side) vertically extending projections
104
a
on which are provided black stripes
104
b
for absorbing external light thereby improving the screen contrast. For example, an acrylic resin is extrusion-molded into the shape of the lenticular lens
104
including the projections
104
a
, followed by printing of only the projections
104
a
with a black color, to form the black stripes
104
b.
As shown in
FIG. 31B
, a width “w” of each black stripe
104
b
is, generally, set at a value being 0.3 to 0.4 time an arrangement pitch “p” of the projections
104
a
of the lenticular lens
104
.
The transmission screen using the above lenticular lens has a disadvantage that it allows diffusion of rays of light in a wide range in the horizontal direction, leading to a wide viewing angle in the horizontal direction; however, it allows diffusion of rays of light only in a narrow range in the vertical direction, leading to a narrow viewing angle in the vertical direction. To solve such a disadvantage, there has been known a structure having a vertically extending lenticular lens combined with a horizontally extending lenticular lens. Such a structure, however, has problems that the increased number of the parts raises the parts cost and manufacturing cost, the increased number of the stacked lenticular lens layers of the screen thickens the screen, and the influence of multiple reflection between the lenticular lens layers becomes larger.
The transmission screen using the lenticular lens has another disadvantage. To provide the black stripes for improving contrast as described above, the projections for printing a black color must be formed on the light outgoing side of the lenticular lens, and in this case, the width of each projection must be set at such a value as not to interfere with rays of outgoing light. Consequently the area ratio of an external light absorbing unit composed of the black stripes is generally set at about 30 to 40%, and thereby the effect of improving contrast is relatively poor.
To cope with the above disadvantage, attention has been given to a transmission screen using a plano lens with minute transparent balls two-dimensionally arranged in place of the above lenticular lens (for example, disclosed in U.S.P. Nos. 2,378,252 and 3,552,822, and Japanese Utility Model Registration No. 2513508). Such a transmission screen using a plano lens has been studied to be practically used for a high definition large screen display.
A configuration of the above transmission screen using a piano lens, having been proposed by the present applicant in Japanese Patent Laid-open No. Hei 9-100590 (filed on Apr. 17, 1997), will be described with reference to
FIGS. 32
to
34
.
FIG. 32
shows a main configuration of a back projection type projector of an open type in which rays of image light L projected from an image projecting unit
21
are diffused forward via a transmission screen
10
composed of a Fresnel lens
22
and a plano lens
23
. As shown in the figure, the plano lens
23
is configured such that minute transparent balls
2
are two-dimensionally disposed in a closet packing array. Accordingly, only one layer of the minute transparent balls
2
allows rays of the image light L to be diffused in a wide range in each of the horizontal and vertical directions.
FIG. 33
shows a back projection type projector of a box type in which image light L projected from an image projecting unit
21
disposed in a housing
25
is reflected by a reflecting mirror
24
and is diffused forward via a transmission screen
10
having a Fresnel lens
22
and a plano lens
23
composed of minute transparent balls
2
.
FIG. 34
shows one example of a configuration of the above plano lens
23
.
The plano lens
23
is configured such that a number of minute transparent balls
2
such as glass beads are held in a transparent adhesive layer
5
formed on a light incoming side transparent substrate
4
with about 50% of the diameter of each minute transparent ball
2
buried in the transparent adhesive layer
5
. A light absorbing layer (coloring layer)
3
made from carbon toner is formed such that gaps between respective adjacent ones of the minute transparent balls
2
are filled with the light absorbing layer
3
and the top and its neighborhood of each minute transparent ball
2
on the light outgoing side are exposed from the light absorbing layer
3
. on the minute transparent balls
2
on the light outgoing side is stacked a transparent substrate
1
via a transparent adhesive layer in order to protect the minute transparent balls
2
and the light absorbing layer
3
from the external environment.
Rays of incoming light L
in
, which have been made incident on the plano lens
23
via the Fresnel lens (not shown), pass through the transparent substrate
4
and the transparent adhesive layer
5
on the light incoming side and are converged through each minute transparent ball
2
, as shown in
FIG. 34
; and the converged rays of light pass through the top and its neighborhood of each minute transparent ball
2
on the light outgoing side and also pass through the transparent adhesive layer
6
and the transparent substrate
1
on the light outgoing side, and go out of the plano lens
23
as diffused rays of outgoing light L
out
. On the other hand, rays of external light L
ex
, having been made incident on the plano lens
23
from the transparent substrate
1
side are almost absorbed by the light absorbing layer
3
, to thereby reduce lowering of contrast due to reflectance of the rays of external light L
ex
.
At this time, in the plano lens
23
, the area ratio of the light absorbing layer
3
on the light outgoing side can be set at about 80% or more, so that lowering of the contrast due to reflectance of the external light L
ex
can be significantly reduced. Thus a screen having a high contrast, being less affected by external light, can be realized.
The piano lens
23
is manufactured, for example, as follows.
The transparent adhesive layer
5
, is formed on the transparent substrate
4
on the light incoming side and a number of the minute transparent balls are scattered-on the transparent adhesive layer
5
. The minute transparent balls
2
are pressed down such that about a half of the diameter of each minute transparent ball
2
is buried in the transparent adhesive layer
5
. A powdery light absorbing material such as carbon toner is scattered over the surface of the minutes transparent balls and is pressed thereon by, for example, a pressing roll to fill gaps between respective adjacent ones of the minute transparent balls
2
, to form a light absorbing layer
3
. Then, part of the light absorbing-material present;on the tops and their neighborhoods of the minute transparent balls
2
on the light outgoing side is wiped off, to form light outgoing portions of the minute transparent balls
2
. After that, a transparent s
Ito Tomotaka
Watanabe Hidetoshi
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Yao Sam Chuan
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