Illumination – With polarizer
Reexamination Certificate
1998-10-27
2001-02-20
Sikder, Mohammad Y. (Department: 2872)
Illumination
With polarizer
C359S484010, C359S485050, C359S486010
Reexamination Certificate
active
06190016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a polarized light irradiation device for purposes of optical alignment of liquid crystals by irradiation of an alignment layer of a liquid crystal cell element with polarized light.
2. Description of Related Art
A liquid crystal cell element usually consists of two substrates. On one of these substrates a driver system for triggering a liquid crystal (for example, a thin film transistor), electrodes for triggering the liquid crystals which are formed of transparent conductive films, and an alignment layer or the like for alignment of the liquid crystals in a certain direction are formed. On the other of these substrates, a light screening film is formed which is called a black matrix. In a color liquid crystal cell element, a color filter, electrodes for triggering the liquid crystal, and an alignment layer are formed.
The alignment layer is usually produced by subjecting the surface of a thin layer, such as polyimide resin or the like, to treatment which is called rubbing, and by providing it with fine grooves in a certain direction; this is designed to align the molecules of the liquid crystal along these grooves in a certain direction. In this rubbing treatment, a process is commonly used in which the alignment layer is produced by rubbing the substrate with a cloth, which is called the rubbing cloth, and with which a turning roller is wound.
Rubbing formation of the alignment layer is done by rubbing the substrate with a rubbing cloth. In doing so, occurrence of adverse effects such as dust, static electricity, scratches and the like and a decrease of yield cannot therefore be prevented.
Recently, therefore, a technique was proposed in which alignment of the liquid crystals is produced without the alignment layer being subjected to the above described rubbing (the technique of aligning the liquid crystal without rubbing is hereinafter called “nonrubbing”).
The nonrubbing technique is a process using polarized light. In this process, the following is performed.
1) The thin layer, as the alignment layer, such as a polyimide resin or the like, is irradiated with polarized light. The polymer of the thin layer is subjected to polarization and a structural change produced only in a certain direction by a photochemical reaction.
2) In this way, alignment of the molecules of the liquid crystal on the thin layer is produced (hereinafter, this alignment technique is called the “optical alignment technique”).
In this process, UV radiation (ultraviolet radiation) with high energy is often used as the emitted polarized light. Recently, an alignment layer material has also been developed in which polarization or structural change is produced by visible radiation.
FIG. 12
shows, in schematic form, a known arrangement of an irradiation device which emits polarized light and executes optical alignment of the alignment layer of a liquid crystal cell element. The device of U.S. Pat. No. 5,934,780 possesses such an arrangement.
In the figure, an irradiation device
10
has a lamp
1
which emits light which contains UV radiation emitted which is focussed by an oval focusing mirror
2
, reflected by a first planar mirror
3
, and is incident on an integrator lens
4
(which may also be called a fly eye lens). The light emerging from the integrator lens
4
is incident via a shutter
5
and via a second planar mirror
6
on a collimation lens
7
, which converts the light into parallel light, which is incident on a polarization element
8
. The polarized light emerging from the polarization element
8
is incident on a workpiece W, such as a liquid crystal cell element or the like.
However, to produce a liquid crystal cell, a large surface is needed. On the outlet side of the collimation lens, therefore, the light flux spreads. Therefore, a gigantic polarization element is needed to obtain light polarized over the entire region to be irradiated.
SUMMARY OF THE INVENTION
In view of the foregoing, a primary object of the invention is to devise an irradiation device for an alignment layer of a liquid crystal cell element in which the need for a large polarization element can be avoided.
This object is achieved in accordance the invention in an irradiation device for an alignment layer of a liquid crystal cell element by the following sets of features.
(1) A lamp;
a focusing mirror for the light of this lamp;
an integrator lens; and
a polarization element located on the incidence side of the integrator lens.
(2) A lamp;
a focusing mirror for the light of this lamp;
an integrator lens;
an input lens which converts beams in the optical path, which emerge from the middle of the opening of the focusing mirror and which are incident in the respective center of the respective lens element which forms the integrator lens, into parallel beams on the incidence side of the integrator lens and which is located between the focusing mirror and the integrator lens; and
a polarization element which is located in the optical path between the input lens and the integrator lens.
(3) A lamp;
a focusing mirror for the light of this lamp;
an integrator lens;
a first lens which is located on the outlet side of the integrator lens and from which parallel beams emerge;
a second lens which converts the parallel beams emerging from the first lens into nonparallel scattered light; and
a polarization element which is located in the optical path between the first lens and the second lens.
To make the polarization element smaller, it can be located in an area in which the light is focussed (i.e. in the vicinity of the integrator lens). However, one such location at which the light is focussed is hot. Therefore, either a multilayer film (an interference film) or a polarization element in which several glass plates are placed at the Brewster angle relative to one another, or the like, are used.
In these polarization elements, however, uniform polarized light cannot be obtained over the entire area to be irradiated if no parallel light is incident. Nonparallel light is incident on the above described location on which the light is focussed. The angle of the light incident in the center of the polarization element therefore differs from the angle of the light incident in the outside peripheral area.
Here, the term “parallel light” is defined as light in which beams in the optical path which emerge from the center of the light source and which are each incident on any point on the surface to be irradiated are parallel to one another on the light incidence side of the surface to be irradiated. These beams in the optical path which emerge from the center of the light source are hereinafter called “center light beams.”
In the polarization element using the multilayer film (interference film), therefore, the proportion of nonpolarized light is large in the outside peripheral area of the region to be irradiated.
In the polarization element using the Brewster angle, in the outside peripheral area the illuminance of a given portion of the polarized light decreases and the polarization direction also changes.
However, the inventors as a result of extensive research have ascertained the following and devised the invention:
(1) When the extinction ratio of the polarized light with which the alignment layer is irradiated, i.e., the portion of polarized light in a given direction in all the emitted light, has a certain value, optical alignment of the alignment layer can be done. That is, the liquid crystal molecules on the alignment layer can be aligned.
(2) The distribution of the portion of unpolarized light (the location-dependent magnitude of the portion of unpolarized light) or the distribution of the illuminance of the polarized light in a certain direction and the distribution of the polarization direction (the location-dependent difference of the polarization direction) can be made uniform by the integrator lens.
(3) If on the incidence side of the polarization element, there is a lens which allows the focussed light or the scattered light to be incident an
Mizuno Osamu
Suzuki Shinji
Nixon & Peabody LLP
Safran David S.
Sikd-er Mohammad Y.
Ushiodenki Kabushiki Kaisha
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