Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Reexamination Certificate
2001-11-09
2004-12-14
Niebling, John F. (Department: 2812)
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
Reexamination Certificate
active
06831707
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application(s) No(s). P2000-343634 filed Nov. 10, 2000, which application(s) is/are incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display element, and to a projection type liquid crystal display device which displays an image by using the liquid crystal display element.
2. Description of the Related Art
Conventionally, projection type liquid crystal display devices (liquid crystal projectors) which display an image by projecting light optically modulated by a liquid crystal display element (hereinafter referred to as a “liquid crystal panel (LCD)”) are known. The projection type liquid crystal display devices can adopt two image projecting methods, namely, a front projection method (front type) for projecting an image from the front side of a screen, and a rear projection method (rear type) for projecting an image from the rear side of the screen. Projection type liquid crystal display devices which produce color display are divided into a single-panel type using a single liquid crystal panel, and a three-panel type using three liquid crystal panels corresponding to light of three colors, red (R), green (G), and blue (B).
FIG. 9
shows the general configuration of an optical system (primarily, an illumination optical system) of a projection type liquid crystal display device as a related art. The projection type liquid crystal display device includes a light source
101
, a pair of first and second multilens array integrators (hereinafter referred to as “MLAs”)
102
and
103
, a PS beam combiner
104
, a condenser lens
105
, a field lens
106
, a liquid crystal panel
107
, and a projection lens
108
which are arranged in that order along an optical axis
100
. The MLAs
102
and
103
have a plurality of microlenses
102
M and
103
M, respectively, arranged in a two-dimensional form. The PS beam combiner
104
includes a plurality of half-wave plates
104
A arranged corresponding to the boundaries between the adjoining microlenses
103
M of the second MLA
103
.
In the projection type liquid crystal display device, illumination light emitted from the light source
101
passes through the MLAs
102
and
103
, and is divided into a plurality of small beams. The light passed through the MLAs
102
and
103
enters the PS beam combiner
104
as light L
10
including a P-polarized light component and an S-polarized light component which intersect each other in a plane perpendicular to the optical axis
100
. The PS beam combiner
104
separates the light L
10
into two types of polarized light components L
11
and L
12
(a P-polarized light component and an S-polarized light component, respectively). One of the separated polarized light component L
11
emerges from the PS beam combiner
104
while maintaining its direction of polarization (for example, P-polarization direction). The other polarized light component L
12
(for example, the S-polarized light component) emerges therefrom after being converted into another polarized light component (for example the P-polarized light component) by the action of the half-wave plate
104
A. Consequently, the directions of polarization of the two separated polarized light components L
11
and L
12
are unified in a specific direction.
The light emerging from the PS beam combiner
104
passes through the condenser lens
105
and the field lens
106
, and is directed onto the liquid crystal panel
107
. The small beams separated by the MLAs
102
and
103
are enlarged to a magnification which is determined by the focal length fc of the condenser lens
105
and the focal length f
ML2
of the microlenses
103
M in the second MLA
103
, and illuminate the entire incident surface of the liquid crystal panel
107
. Consequently, a plurality of enlarged beams are superimposed on the incident surface of the liquid crystal panel
107
, and the entire incident surface is uniformly illuminated. The liquid crystal panel
107
spatially modulates the incident light according to image signals and emits the light. The light emerging from the liquid crystal panel
107
is projected onto a screen (not shown) by the projection lens
108
, thereby forming an image on the screen.
In the liquid crystal panel, a thin-film transistor (TFT) and the like are formed as a driving device on the substrate, and therefore, a shielded region called a black matrix is formed between adjoining pixels. For this reason, the aperture ratio of the liquid crystal panel does not equal 100%. Conventionally, in order to increase the effective aperture ratio of the liquid crystal panel, for example, one or more light-collecting microlenses per dot (per pixel or per subpixel) are placed in the optical axis direction on a counter substrate disposed on the light incident side. Herein, the “effective aperture ratio” of the liquid crystal panel refers to the ratio of light beams emerging from the liquid crystal panel to all light beams incident on the liquid crystal panel. In a projection type liquid crystal display device, in general, the effective aperture ratio of the liquid crystal panel is defined in consideration not only of the light loss of the liquid crystal panel, but also of the eclipse of light by the projection lens disposed on the downstream side.
FIG. 10
shows an example of a structure of the liquid crystal panel
107
using microlenses. For ease of viewing, a part of
FIG. 10
is not hatched. The liquid crystal panel
107
includes a pixel electrode substrate
140
B, and a counter substrate
140
A placed opposed to the pixel electrode substrate
140
B on the light incident side thereof with a liquid crystal layer
145
therebetween.
The pixel electrode substrate
140
B includes a glass substrate
148
, a plurality of pixel electrode portions
146
, and a plurality of black matrix portions
147
placed on the light incident side of the glass substrate
148
. The pixel electrode portions
146
and the black matrix portions
147
are arranged in a two-dimensional form. Each of the pixel electrode portions
146
is made of a conductive transparent material. Each of the black matrix portions
147
is formed between adjoining pixel electrode portions
146
, and is shielded by, for example, a metal film. A switching element such as a TFT (not shown) is formed in each black matrix portion
147
so as to selectively apply a voltage to the adjoining pixel electrode portion
146
according to an image signal.
The counter substrate
140
A includes a glass substrate
141
, a microlens array
142
, and a cover glass
144
arranged in that order from the light incident side. A resin layer
143
is formed between the glass substrate
141
and the microlens array
142
. Although not shown, counter electrodes are interposed between the cover glass
144
and the liquid crystal layer
145
so as to generate a potential between the counter electrodes and the corresponding pixel electrode portions
146
. The resin layer
143
is made of an optical resin having a refractive index n
1
.
The microlens array
142
includes a plurality of microlenses
142
M made of an optical resin having a refractive index n
2
(>n
1
) arranged in a two-dimensional form corresponding to the pixel electrode portions
146
. Each of the microlenses
142
M is convex on the light incident side, and has a positive refractive power. The microlens
142
M serves to collect light, which is incident thereon via the glass substrate
141
and the resin layer
143
, toward the corresponding pixel electrode portion
146
. As long as the projection lens
108
disposed on the downstream side has a sufficient F-number, light collected by the microlens
142
M and entering an aperture
146
A, of light incident on the liquid crystal panel
107
, is available for image display. Such a microlens
142
M allows more light to enter the aperture
146
A of the pixel electrode portion
146
than in a case in which the microlens
142
is
Sonnenschein Nath & Rosenthal LLP
Sony Corporation
Stevenson Andre′ C.
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