Optical: systems and elements – Polarization without modulation – Polarizarion by dichroism
Reexamination Certificate
2001-07-12
2003-05-20
Dudek, James (Department: 2871)
Optical: systems and elements
Polarization without modulation
Polarizarion by dichroism
C359S488010, C359S506000, C349S124000
Reexamination Certificate
active
06567216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a polarization element of a light irradiation device for optical alignment of liquid crystals in which the alignment layer of a liquid crystal cell element is irradiated with polarized light. The invention relates especially to a polarization element which is suitable for optical alignment of a wide-view film.
2. Description of Related Art
A liquid crystal cell element is produced as follows:
An alignment layer formed on the surface of a transparent substrate is treated for alignment of the liquid crystals in a desired direction (alignment treatment).
Two of these transparent substrates are cemented to one another such that the alignment layers are located on the inside and a gap with a stipulated distance is maintained between the two substrates.
Liquid crystals are injected into this gap. For the above described alignment treatment of the alignment layer of a liquid crystal cell element, there is a technique which is called “optical alignment”. Here, an alignment layer is irradiated with polarized light and exposed.
An irradiation device for polarized light for optical alignment is disclosed, for example, from the Japanese patent disclosure document HEI 10-90684.
Recently the above described irradiation device for polarized light is being used more and more often to produce a wide-view film, besides for production of the above described liquid crystal cell element. A wide-view film is produced as follows:
Liquid crystals which can be cured using UV light are applied to a base film.
Liquid crystal molecules are aligned in a certain direction.
Afterwards the liquid crystals are cured by UV irradiation so that the direction of the liquid crystal molecules is fixed.
By cementing a wide-view film onto a liquid crystal cell, a reduction of the image quality can be equalized, i.e., the field of view of LCDs can be enhanced.
Conventionally, the above described process of “alignment of the liquid crystal molecules in a certain direction” is carried out by rubbing. But recently, it is being done more and more often using the above described irradiation with polarized light and by optical alignment.
FIG. 7
shows the arrangement of an irradiation device for polarized light which optically aligns a wide-view film according to the example. In the figure, a discharge lamp
1
, such as a super high pressure mercury lamp or the like, is located in an oval focusing mirror
2
, and directs light from the lamp to a first planar mirror
3
from which it passes through a polarization element
8
, an integrator lens
4
, and a shutter
5
to a second planar mirror which deflects the light to a collimation lens
7
. These components make up the irradiation device for polarized light.
In the polarization element
8
, several glass plates are inclined by the Brewster angle with respect to the optical axis of the incident light beam and are located parallel to one another at intervals. These glass plates are combined with one another in a V-shape and are arranged such that the light exit side becomes convex.
When a polarization element is used which is made of glass plates which have been combined in a V-shape, the advantages are the following:
The size of the entire polarization element (the size in the lengthwise direction with respect to the optical axis) can be reduced more than in the case in which the glass plates are not combined in a V-shape.
The size of the individual glass plate becomes smaller.
The production costs per glass plate become smaller.
Two directions for the arrangement of the polarization element formed of glass plates which have been combined in a V-shape can be imagined, i.e., the direction in which the exit side is convex, and the direction in which the incidence side is convex.
FIG. 7
shows a polarization element in which the exit side is convex (in which the light is incident from the direction in which the glass plates form a “valley”).
The number of glass plates used for the polarization element is not limited to the number in the drawings, but it can be set suitably according to the desired illuminance on a surface to be irradiated and according to the extinction ratio.
In the figure, the light which is emitted from the discharge lamp
1
and which contains UV radiation is focused by the oval focusing mirror
2
, reflected by the first plane mirror
3
and is incident in the polarization element
8
. The polarization element
8
passes P-polarized light and reflects most of the S-polarized light. The light emerging from the polarization element
8
therefore becomes mainly P-polarized light. The light emerging from the polarization element
8
is incident in the integrator lens
4
.
The light emerging from the integrator lens
4
is reflected via the shutter
5
and by the second plane mirror
6
, is converted into parallel light by means of the collimation lens
7
and is emitted onto a wide-view film
10
to which liquid crystals which can be cured with UV light have been applied. The concept of “wide-view film
10
” is defined below as a film to which liquid crystals which can be cured with UV light have been applied.
The wide-view film
10
is wound in the manner of a roll as an endless workpiece with a great length onto a take-off roller
11
a
. After the wide-view film which has been wound onto the take-off roller
11
a
has been unwound and irradiated with polarized light, it is wound onto the take-up roller
11
b
, as is shown in the drawings. During transport of the film
10
the polarized light is emitted onto the film
10
with a pre-set angle.
It is known that the above described wide-view film is also aligned at a poor extinction ratio of the polarized light (for example, P-polarized light to S-polarized light=3:1 to 2:1). Polarized light with this extinction ratio can also be obtained without using an optical element such as a collimator or the like.
In
FIG. 7
, the polarization element
8
is located between the first plane mirror
3
and the integrator lens
4
. But, as shown in
FIG. 8
, the polarization element
8
can be located on the exit side of the collimation lens
7
.
FIG. 9
shows another example of the arrangement of an irradiation device for polarized light for optical alignment of a wide-view film. In this embodiment, a rod-shaped tube lamp
21
, for example a high pressure mercury lamp or a metal halide lamp is located at the focal point of a trough-like mirror
22
with a cross section which is a parabola. In the polarization element
8
′, as in the polarization element
8
shown in
FIG. 7
, several glass plates are inclined by the Brewster angle with respect to the optical axis of the incident light beam and are arranged parallel to one another at intervals. These glass plates are combined with one another in a V-shape and are arranged such that the light exit side becomes convex.
The wide-view film
10
, as was described above, is an endless workpiece of great length that is wound as a roll onto the take-off roller
11
a
. After the wide-view film which has been wound onto the take-off roller
11
a
has been unrolled and irradiated with polarized light, it is wound onto the take-up roller
11
b
as is shown in the drawings. During transport of the film
10
, the polarized light is emitted onto the film
10
at a pre-set angle.
In the irradiation device for polarized light shown in
FIG. 9
, the directly projected light from the lamp is scattered light. Therefore, light with a non-Brewster angle is incident in the polarization element. Furthermore, there is also light which passes through the polarization element without polarization separation.
However, the light which has been reflected by the trough-shaped mirror
22
is converted essentially into parallel light and is incident with the Brewster angle in the polarization element, by which it is subjected to polarization separation. As a result P-polarized light emerges. Therefore, light emerges from the polarization element which, for the most part, has a large proportion of P-polarized lig
Suzuki Shinji
Yamada Sayu
Dudek James
Duong Tai
Safran David S.
Ushiodenki Kabushiki Kaisha
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