Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2002-02-28
2003-09-16
Ben, Loha (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S455000
Reexamination Certificate
active
06621637
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a projection screen technology, and, more particularly, to a method of producing a transmissive screen used as a display screen of, for example, a projection television or a microfilm reader and to the transmissive screen produced by this method.
BACKGROUND ART
In recent years, a rear projector using a liquid crystal light valve or a CRT as a large screen display has been drawing attention. The display displays an image by forming an image on a transmissive screen using image light from an image projecting portion. This type of transmissive screen is bright when an observer observes the image and has predetermined very small lens members formed thereon so as to increase the viewing angle.
As shown in
FIG. 11
, with regard to light distribution property of such a bright screen having a wide viewing angle, a viewing angle
1101
which is wider in the horizontal direction than in the vertical direction is preferred. This is because the viewing angle of a human being is wider in the horizontal direction than in the vertical direction. When the light distribution is made equal in the vertical and horizontal directions, light is also distributed in the vertical direction which is not really necessary with regard to the viewing angle of a human being, so that the brightness as a whole is reduced.
Representative examples of the structures of the transmissive screen include the following:
{circle around (1)} A lenticular sheet including a lens portion formed by providing convex cylindrical lenses (semi-circular cylindrical convex lenses) side by side. As shown in FIG.
9
(
a
), in general, the lenticular sheet has a structure formed by forming both surfaces of the sheet into convex cylindrical lens surfaces
901
, forming protrusions at boundary portions between the respective cylindrical lenses at one of the surfaces of the sheet (the surface from which image light
201
exits), and forming a light-shielding layer (a black stripe having light-absorption property)
902
on the top portion of each of the protrusions.
The lenticular sheet is obtained by carrying out a press-molding operation on a transparent thermoplastic resin sheet or by molding both surfaces of the resin sheet at the same time that molten extrusion is carried out.
{circle around (2)} A planar lens having very small transparent balls arranged two dimensionally (disclosed in, for example, U.S. Pat. Nos. 2,378,252 and 3,552,822, and Japanese Utility Model Registration Gazette No. 2513508). As shown in FIG.
10
(
a
), in the planar lens, each very small transparent ball
1002
has of the order of 50% of its diameter embedded in and held by a light-incident side transparent layer
1001
and the remaining 50% embedded in a light-exiting side light absorption layer
1003
.
The planar lens is obtained by forming a sheet comprising a transparent layer, very small transparent balls, and a light-absorption layer, and, then, bonding it to a transparent substrate
1004
.
However, such conventional transmissive screens have the following problems.
In the lenticular lens, it is difficult to achieve a fine pitch when each of the above-described molding methods is performed on thermoplastic resin, so that, when the lenticular lens is used as a screen of a rear projector, which, in recent years, has been providing increasingly higher definition, there is a problem in that deterioration of image quality occurs due to reduced resolution and production of moiré. In addition, a very small light diffusing material is usually mixed in the inside portion of the lenticular lens in order to increase the viewing angle in the vertical direction (a direction parallel to the lenticular lens, which is represented by reference numeral
903
in FIG.
9
(
b
)) in which the lenticular lens does not have optical power. This gives rise to the problem that image quality is deteriorated because speckles are produced due to the interference of image light caused by the light-diffusing material. Further, both of the molding methods performed on the thermoplastic resin require large molding machines or dies having diagonals equal to or greater than 50 inches, which are of the same size as the screen of the rear projector, giving rise to the problem that production costs become very high.
On the other hand, in the planar lens having very small transparent balls arranged two-dimensionally, as shown in FIG.
10
(
b
) in which the planar lens is viewed from an image light incident side, dead spaces, which do not pass image light, are formed between the individual very small balls
1002
, so that the image light incident thereupon is not transmitted to the observer side. In addition, it is very difficult to perform a minute filling operation completely with respect to the very small balls, so that the dead spaces increase in size. Further, since the thin light absorption layer
1003
remains at the observer-side surfaces of the very small transparent balls, light is absorbed. Due to these three reasons, the problem that light transmittance of the transmissive screen is low arises.
Since the increase in the viewing angle by the very small balls is completely isotropic, light is also diffused in the vertical direction, in which the viewing angle does not normally need to be increased very much, to the same extent as in the horizontal direction. This gives rise to the problem of insufficient brightness when the image is viewed from the front.
In general, the planar lens is produced by the step of forming a sheet comprising a transparent layer, very small transparent balls, and a light absorption layer, and bonding the sheet to a transparent substrate. However, in the step of bonding the sheet to the transparent substrate, unevenness in the bonding occurs, so that the display of the image becomes ununiform, and, by insufficient adhesiveness between the sheet and the transparent substrate, interfacial multiple reflection occurs, thereby giving rise to the problem of reduced resolution.
In order to overcome the above-described problems, it is an object of the present invention to realize a method of producing at a low cost a transmissive screen which is bright, which has high contrast and resolution, and which is capable of displaying a high-quality image without moiré and scintillation.
DISCLOSURE OF INVENTION
In order overcome the above-described problems, according to the present invention, there is provided a first form of a method of producing a transmissive screen having a structure including light-absorption-material patterns formed at locations corresponding to locations of lens members, which are provided side by side on a light-transmissive substrate, and to locations of boundary portions between the corresponding lens members, the method comprising the step of forming the lens members or precursors thereof by causing very small drops of lens compositions to be discharged and to land near a light-transmission area on a surface of the light-transmissive substrate. Means for causing the very small drops of the lens compositions to be discharged and to land is an inkjet recording head. Preferably, the inkjet recording head is a piezo jet recording head.
According to this form, the individual lens members, formed on the surface of the transmissive screen, are formed by the discharging of lens compositions from an inkjet recording head, typified by, for example, a piezo jet recording head, having the excellent feature of forming a very fine form with high precision over a large area. Therefore, very fine lens members can be produced. Consequently, it is possible to provide a transmissive screen which provides excellent resolution and which does not have reduced image quality due to moiré. In addition, this method can be used in producing a transmissive screen by a manufacturing device including a mechanism that scans the piezo jet recording head in the horizontal/vertical directions of the screen. Therefore, expensive manufacturing devices, such as large dies and molding devices, are not required, thereby making it
Hasei Hironori
Kiguchi Hiroshi
Miyashita Satoru
Uchiyama Shoichi
Ben Loha
Choi William
Oliff & Berridge PLC.
Seiko Epson Corporation
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