Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2003-08-22
2004-11-09
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S619000, C359S621000, C359S622000, C359S455000, C359S456000, C359S626000, C257S432000, C257S435000
Reexamination Certificate
active
06816312
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a lenticular lens sheet for use in a rear projection screen. More particularly, it relates to a lenticular lens sheet including on its light-emerging surface side a light-shielding layer, and to a process of producing the same.
BACKGROUND ART
A so-called projection-type television, which an image is projected from the rear and the projected image is viewed from the front, is known as a large-screen television. Such a projection-type television includes an imaging light source and a rear projection screen for displaying thereon an image projected from the imaging light source. Currently used for the imaging light source are CRT's (cathode-ray tubes) for projection, characterized by higher luminance than that of ordinary CRT's, as well as liquid crystal display (LCD) projectors, digital light processing (DLP) projectors using digital micro-mirror devices (DMD's), and the like.
FIG. 7
is a view showing an example of a rear projection screen for use in a projection-type television. As shown in this figure, a rear projection screen
10
is composed of a Fresnel lens sheet (Fresnel convex lens)
11
and a lenticular lens sheet
12
, where an image projected from an imaging light source (not shown in the figure) located at the rear of the rear projection screen
10
(upside in the figure) is viewed by a viewer who is in front of the rear projection screen
10
(downside in the figure). In the rear projection screen
10
shown in
FIG. 7
, when light
20
emitted by the imaging light source (not shown in the figure) located at the rear of the rear projection screen
10
(upside in the figure), the rays of the light
20
spreading to a certain extent, enters the rear projection screen
10
, this incident light
20
is converged by the Fresnel lens sheet
11
to become, for example, parallel rays
21
. These parallel rays
21
are converged by lenticular lenses
13
that are provided on the lenticular lens sheet
12
on its light-entering surface side, and go out as emergent light
22
from the light-emerging surface side of the lenticular lens sheet
12
at an angle in the range &thgr;. This angle range &thgr; is the range in which the projected image is visible.
As shown in
FIG. 7
, the lenticular lens sheet
12
for use in such a rear projection screen
10
contains, on its light-emerging surface side, a light-shielding layer
14
in order to prevent reflection of extraneous light (light that enters from the downside in
FIG. 7
) to improve image contrast. The light-shielding layer
14
has light-shielding areas (black stripes)
14
a
that correspond to the non-light-converging parts of the lenticular lenses
13
. The light-shielding areas
14
a
in the light-shielding layer
14
can be created by coating, with a material capable of shielding light, those parts with a certain width of the light-emerging surface of the lenticular lens sheet
12
that correspond to the non-light-converging parts of the lenticular lenses
13
.
It is necessary to create the light-shielding areas
14
a
in the light-shielding layer
14
as large as possible in such positions that the incident light
20
projected from the rear does not go out, with high positional accuracy relative to the lenticular lenses
13
having the function of converging the incident light
20
. There is therefore a heavy demand for a method of accurately creating the light-shielding areas
14
a
in the light-shielding layer
14
.
In recent years, an LCD or DLP projector, or the like has come to be used, instead of a CRT, in a projection-type television as an imaging light source. An image projected from such a light source is composed of dot matrixes and has sharper definition. For this reason, a so-called fine-pitch lenticular lens sheet
12
with a lens pitch smaller than that required for the magnifying projection of an image on a CRT has come to be demanded. Specifically, as long as a CRT is used, it is enough for the lenticular lenses to have a pitch between 0.5 mm and 2.0 mm, but when an LCD or DLP projector, or the like is used, the lenticular lenses are required to have a fine pitch between 0.05 mm and 0.3 mm.
The method described in Japanese Laid-Open Patent Publication No. 120102/1997, for example, has been known as a method of creating light-shielding areas
14
a
in a light-shielding layer
14
that is used in a fine-pitch lenticular lens sheet
12
of the above-described type. In this method, an ionizing-radiation-curing resin layer is formed on the flat surface of a lenticular lens sheet opposite to the lens-provided surface (the surface on which lenticular lenses are formed), and ultraviolet light is applied to the lenticular lens sheet from the lens-provided surface side to expose the ionizing-radiation-curing resin layer, thereby curing those parts of the resin layer that are in the positions corresponding to the light-converging parts of the lenticular lenses. Making use of the stickiness of the surfaces of those parts of the resin layer other than the cured parts, a toner or transfer ink layer (black in color) is adhered to the surfaces of those parts of the resin layer that are in the positions corresponding to the non-light-converging parts of the lenticular lenses. A light-shielding layer having therein a predetermined light-shielding pattern is thus formed on the lenticular lens sheet on its light-emerging surface side.
However, the lenticular lens sheet produced by the method described in the above publication is at a disadvantage in that the light-shielding pattern in the light-shielding layer is poor in positional accuracy. Another drawback is as follows: the light-shielding effect of the light-shielding layer is insufficient, so that when this lenticular lens sheet is combined with a light-converging lens means such as a Fresnel lens sheet to make a rear projection screen, sufficiently high optical efficiency cannot be obtained, and, in addition, it is highly possible that high image contrast cannot be obtained.
Further, in the method described in the above publication, the process of creating the light-shielding areas requires the step of forming an ionizing-radiation-curing resin layer; the step of curing, by exposure, those parts of the resin layer that are in the positions corresponding to the light-converging parts of the lenticular lenses, leaving the surfaces of the other parts of the resin layer sticky; the step of adhering a toner or transfer ink layer to the non-light-converging parts; and so forth. This method thus requires a large number of steps, so that it is poor in efficiency.
DISCLOSURE OF THE INVENTION
The present invention was accomplished in the light of the aforementioned drawbacks in the background art. An object of the present invention is therefore to provide a lenticular lens sheet that comprises a light-shielding layer having a light-shielding pattern formed with high positional accuracy and that ensures sufficiently high image contrast even when it is combined with a light-converging lens means such as a Fresnel lens sheet to make a rear projection screen, and a process of producing such a lenticular lens sheet.
Another object of the present invention is to provide a lenticular lens sheet for use in a rear projection screen, that comprises a light-shielding layer and that can be produced with higher efficiency, and a process of producing such a lenticular lens sheet.
The main feature of the present invention is that: the light-shielding layer that is formed on the lenticular lens sheet on its light-emerging surface side is made from a silver salt emulsion (a silver salt photosensitive material) which is widely used in the fields of photography and medical service. With the use of a silver salt photosensitive film or the like, a silver salt emulsion layer is laminated to the light-emerging surface of the lenticular lens sheet opposite to its lens-provided surface (the surface on which lenticular lenses are formed). Exposure light is applied to the lenticular lens sheet from its lens-provided surface side to expos
Handa Shinichi
Nishiyama Masashi
Oda Kumpei
Yamashita Yoshiyuki
Dai Nippon Printing Co. Ltd.
Dinh Jack
Epps Georgia
Parkhurst & Wendel L.L.P.
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