Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-05-24
2004-01-20
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S005000, C349S009000, C349S065000
Reexamination Certificate
active
06680762
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application(s) No(s). P2001-158526 filed May 28, 2001, 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 device and to a projection liquid crystal display apparatus which displays an image by using the liquid crystal display device.
2. Description of the Related Art
Hitherto, projection liquid crystal display apparatuses (liquid crystal projectors) which project light modulated by liquid crystal display devices (hereinafter referred to as liquid crystal panels) on a screen and thereby display an image on the screen are known in the art. There are two types of image-projection methods used in projection liquid crystal display apparatuses: a front projection type (front type) in which an image is projected onto the screen from the front side of a screen, and a rear projection type (rear type) in which an image is projected onto a screen from the rear side of the screen. In addition, there are two types of projection liquid crystal display apparatuses for displaying color images: a single-panel type in which a single liquid crystal panel is used and a three-panel type in which three liquid crystal panels for three colors, that is, red (R), green (G), and blue (B), are used.
FIG. 12
is a schematic diagram showing an optical system (mainly an illuminating optical system) of a projection liquid crystal display apparatus of the known art. In this projection liquid crystal display apparatus, a light source
101
, first and second multi-lens array integrators (hereinafter abbreviated as MLAs)
102
and
103
forming a pair, a PS composite element
104
, a condenser lens
105
, a field lens
106
, a liquid crystal panel
107
, and a projection lens
108
are arranged along an optical axis
100
. The MLAs
102
and
103
include a plurality of small lenses (microlenses)
102
M and
103
M, respectively, which are arranged two-dimensionally. The PS composite element
104
includes a plurality of half-wave plates
104
A at positions corresponding to the positions between adjacent microlenses on the second MLA
103
.
In this projection liquid crystal display apparatus, illuminating light emitted from the light source
101
is divided into a plurality of light beams when it passes through the MLAs
102
and
103
. The light beams emitted from the MLAs
102
and
103
are incident on the PS composite element
104
. Light L
10
, which is incident on the PS composite element
104
includes a P-polarized light component and a S-polarized light component which intersect each other on a plane perpendicular to the optical axis
100
. The PS composite element
104
serves to separate the incident light L
10
into the two kinds of polarized light components (a P-polarized light component and an S-polarized light component) L
11
and L
12
. After the polarized light components L
11
and L
12
are separated from each other, the light component L
11
leaves the PS composite element
104
without changing its polarization direction (for example, the P-polarization). Conversely, the polarization direction of the light component L
12
(for example, the S-polarization) is changed to the other direction (for example, the P-polarization) by the half-wave plate
104
A upon exiting the PS composite element
104
. Accordingly, light having a predetermined polarization direction is emitted from the PS composite element
104
.
The light emitted from the PS composite element
104
passes through the condenser lens
105
and the field lens
106
, and is radiated onto the liquid crystal panel
107
. The divided light beams formed by the MLAs
102
and
103
are magnified at a magnification ratio determined on the basis of the focal length fc of the condenser lens
105
and the focal length f
ML2
of the microlenses
103
M formed on the second MLA
103
, and are radiated onto the entire incident surface of the liquid crystal panel
107
. Accordingly, a plurality of magnified light beams overlap one another on the incident surface of the liquid crystal panel
107
, thereby uniformly illuminating the incident surface of the liquid crystal panel
107
. The liquid crystal panel
107
spatially modulates the light incident thereon in accordance with an image signal, and emits modulated light. The light emitted from the liquid crystal panel
107
is projected onto a screen (not shown) by the projection lens
108
, so that an image is formed on the screen.
In liquid crystal panels, in order to form driving devices such as thin-film transistors (TFTs) on a substrate, a light-shielding area called a black-matrix is formed to separate adjacent pixels. Accordingly, aperture ratios of liquid crystal panels never reach 100%. Therefore, in liquid crystal panels of the known art, in order to increase the effective aperture ratio, one or more microlenses are arranged along an optical axis for each dot (a single pixel or a single sub-pixel), the microlenses being formed on an opposing substrate disposed at the light-incident side and serving as condenser lenses. The “effective aperture ratio” is the ratio of light beams emitted from a liquid crystal panel to light beams incident on the liquid crystal panel. In projection liquid crystal display apparatuses, the effective aperture ratio is generally determined by taking into account not only the light loss caused in the liquid crystal panel but also the shading of light caused by the projection lens.
FIG. 13
is a diagram showing an example of the construction of the liquid crystal panel
107
in which microlenses are formed. In order to make the figure clear, the hatching is partly omitted. The liquid crystal panel
107
includes a pixel electrode substrate
140
B and an opposing substrate
140
A which is disposed at the light-incident side of the pixel electrode substrate
140
B in such a manner that the opposing substrate
140
A and the pixel electrode substrate
140
B oppose each other with a liquid crystal layer
145
therebetween.
The pixel electrode substrate
140
B includes a glass substrate
148
, a plurality of pixel electrodes
146
, and a plurality of black matrix elements
147
. The pixel electrodes
146
and the black matrix elements
147
are arranged two-dimensionally on the glass substrate
148
at the light-incident side thereof. The pixel electrodes
146
are conductive, transparent members, and the black matrix elements
147
are formed between adjacent pixel electrodes
146
. The black matrix elements
147
are shielded from light by, for example, a metal layer, and switching elements (not shown) used for selectively applying a voltage to the adjacent pixel electrodes
146
in accordance with an image signal are formed inside the black matrix elements
147
. TFTs, for example, are used as the switching elements for applying a voltage to the pixel electrodes
146
.
The opposing substrate
140
A includes a glass substrate
141
, a microlens array
142
, and a cover glass
144
in that order from the light-incident side. A resin layer
143
is laminated between the glass substrate
141
and the microlens array
142
. In addition, although not shown in the figure, opposing electrodes for generating a voltage between the pixel electrodes
146
and the opposing electrodes are arranged between the cover glass
144
and the liquid crystal layer
145
. The resin layer
143
is formed of an optical plastic whose refractive index is n1.
The microlens array
142
is formed of an optical plastic whose refractive index is n2(>n1), and includes a plurality of microlenses
142
M arranged two-dimensionally in correspondence with the pixel electrodes
146
. The microlenses
142
M are convex toward the light-incident side thereof and have positive refractive power. Each microlens
142
M serves to condense light incident thereon through the glass substrate
141
and the resin layer
143
on the corresponding pixel electrode unit
146
. When the projectio
Fukuda Toshihiro
Furuya Tomoki
Chowdhury Tarifur R.
Sonnenschein Nath & Rosenthal LLP
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