Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2001-11-21
2004-04-20
Zanda, David A. (Department: 2829)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S754120
Reexamination Certificate
active
06724215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a method of evaluating a liquid crystal panel, and an evaluating device. More particularly, the present invention relates to a suitable manufacturing technology for finding out the thickness of or the presence or absence of dust in a liquid crystal layer of a reflective liquid crystal panel having a reflective layer formed at the inside surface thereof.
2. Description of the Related Art
In general, a liquid crystal panel is formed by bonding two substrates and injecting liquid crystals between both of these substrates. Electrode patterns for applying a voltage to the liquid crystal layer are formed on the two substrates, respectively. When constructing a liquid crystal display device using this liquid crystal panel, the thickness (the cell gap) of the liquid crystal layer greatly affects the display properties, so that it is very important to set the thickness of the liquid crystal layer with high precision, and to form the liquid crystal layer with uniform thickness throughout the entire panel.
For this reason, in a conventional method of manufacturing a liquid crystal display device, examinations are carried out to evaluate the thickness and the uniformity of the thickness of the liquid crystal layer after forming the liquid crystal panel. Since a display defect occurs when dust contaminates the inside of the liquid crystal layer, an examination as to whether or not there is any dust inside the liquid crystal layer is sometimes carried out.
Here, the above-described examination may, for example, be carried out only to find out whether the manufactured liquid crystal panels are good or defective panels and to eliminate the defective panels, or to obtain the thicknesses and other characteristics values of the liquid crystal layers of the manufactured liquid crystal panels in order to specify the quality level of the liquid crystal panels for classifying them, or to obtain control data for finely adjusting the manufacturing conditions of a manufacturing line as a result of feeding back results. Accordingly, the examination is widely utilized as a way of evaluating liquid crystal panels.
In the conventional method of manufacturing a liquid crystal device, when, as shown in FIG.
7
(
a
), a liquid crystal panel
10
including a liquid crystal layer
10
a
is examined, a method may be used in which zonal illumination is carried out using an annular light source
11
, light emitted from the light source
11
is converted into linearly polarized light by a polarizer
12
, the liquid crystal panel
10
is illuminated by the linearly polarized light, and, through a polarizer
13
, reflected light, formed by the reflection of the linearly polarized light, is eventually analyzed by a color photometer
14
(which may be a CCD camera, a photomultiplier, or a spectrometer).
As shown in FIG.
7
(
b
), there is another method in which light emitted from a light source
15
, which can be considered as a point light source, irradiates the liquid crystal panel
10
through a polarizer
16
, and reflected light, formed by the reflection of the emitted light, is detected by an obliquely disposed color photometer
18
through a polarizer
17
.
In the methods shown in
FIG. 7
, when the optical axes serve as references, by appropriately setting the relationships between the directions of the polarized-light polarization axes of the light-incident-side polarizers
12
and
16
and the corresponding directions of the polarized-light polarization axes of the light-detection-side polarizers
13
and
17
so that the corresponding directions have angular differences of, for example, 20 to 60 degrees, the hues of the detected light vary in accordance with the thickness of the liquid crystal layer, so that the thickness of and the presence or absence of dust are examined based on the hues of images photographed using the color photometers
14
and
18
.
Here, when specularly reflected light, formed by the reflection of the illuminating light incident upon the liquid crystal panel
10
, enters these color photometers, specularly reflected light from the interface between the substrates
10
b
and
10
c
of the liquid crystal panel
10
reduces the quantity of a reflected-light component of the light obtained after the passage of the light through the liquid crystal layer
10
a
, so that the precision of detection is reduced. Therefore, as shown in FIGS.
7
(
a
) and
7
(
b
), while the incident angle of the illuminating light with respect to the liquid crystal panel
10
and the exiting angle of the detection light to be detected by the color photometers
14
and
18
are set differently, reflected light that is not specularly reflected light, that is, diffused light is only detected in order to examine the liquid crystal panel.
However, in the conventional methods of examining a liquid crystal panel, light emitted from the light sources
11
and
15
irradiate the liquid crystal panel
10
after passing through the corresponding polarizers
12
and
16
, and the color photometers
14
and
18
receive only diffused light and avoid receiving specularly reflected light, so that the quantity of light incident upon the color photometers
14
and
18
is decreased, and the S/N ratio (signal-to-noise ratio) of the detection signal is low, resulting in the problem that it is difficult to examine the liquid crystal panel with high precision.
In addition, since the reflected light to be detected by the color photometers
14
and
18
is diffused light instead of specularly reflected light, it is thought that the light component of the reflected light obtained as a result of the passage of light through the liquid crystal layer
10
a
does not necessarily precisely reflect the state of the liquid crystal layer
10
a
, so that, also due to this, the problem that accurate information regarding the liquid crystal layer
10
a
cannot be detected arises.
Accordingly, in order to overcome the above-described problems, it is an object of the present invention to provide a novel method of evaluating a liquid crystal panel and evaluating device, which make it possible to precisely obtain information regarding a liquid crystal layer other than by the conventional methods.
SUMMARY OF THE INVENTION
In order to overcome the above-described problems, according to the present invention, there is provided a liquid-crystal-panel evaluating method for optically evaluating a liquid crystal panel, wherein polarized light in a predetermined state is made to be incident upon the liquid crystal panel, and a ratio of a polarized component of specularly reflected light, formed as a result of the reflection of the incident light, transmitted through a liquid crystal layer of the liquid crystal panel is increased to form detection light in order to evaluate the panel based on the detection light.
According to the present invention, by causing polarized light in a predetermined state to be incident upon the liquid crystal panel, and increasing the ratio of the polarized component of the specularly reflected light, formed by the reflection of the incident light, transmitted through the liquid crystal layer in order to form detection light, the panel is evaluated based on the detection light. Therefore, by using specularly reflected light, the quantity of the detection light can be increased compared to that provided by the conventional panel evaluating methods, so that it is possible to increase the precision of the detection. In addition, by increasing the polarized component of the specularly reflected light transmitted through the liquid crystal layer, it is possible to reduce the ratio of the specularly reflected light that has exited without passage of the light through the liquid crystal layer, similarly to, for example, the light reflected at the surface of a substrate of the liquid crystal panel, so that a reduction in the detection precision can be restricted.
Here, in the specification of the application, specularly reflected light refer
Harness & Dickey & Pierce P.L.C.
Nguyen Tung X.
Seiko Epson Corporation
Zanda David A.
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