Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
2000-06-23
2002-10-29
Kim, Robert H. (Department: 2882)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S479000, C313S474000
Reexamination Certificate
active
06472810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light source device incorporated in an exposure apparatus for usc in the manufacture of a panel of a cathode ray tube (referred to hereinafter as a “CRT”). More particularly, the invention relates to a light source device capable of intercepting light such as reflected or scattered light which results in uneven exposure to reduce uneven exposure, thereby achieving high-quality exposure.
2. Description of the Background Art
A phosphor screen on the inner surface of a panel of a CRT for use as a display monitor and the like has a black matrix (referred to hereinafter as a “BM”) produced using resist exposure, and a three-color phosphor pattern produced using direct exposure.
FIG. 11
is a plane view (with a vertical section taken along the line I-II of an enlarged part) for illustrating a structure of the phosphor screen formed on a CRT panel
70
by using an exposure apparatus. In
FIG. 11
, the reference numeral
701
designates a BM for providing clear separation between phosphors to enhance an image quality; and
702
,
703
and
704
designate red-emitting (R), green-emitting (G) and blue-emitting (CB) phosphors, respectively, which are formed in stripe-shaped configuration in predetermined positions of openings of the BM
701
.
The phosphor screen shown in
FIG. 11
is formed in the steps of forming the BM
701
by a lift-off method using resist exposure, and repeating for R, G and B in any order the process of applying a photosensitive phosphor material, e.g., for G to the inner surface of the panel on which the BM
701
is formed to leave phosphor stripes, e.g. green-emitting phosphor stripes, in the predetermined positions of the openings of the BM
701
by direct exposure and development processes.
FIG. 12
is a cross-sectional view of an exposure apparatus for use in the manufacture of the CRT panel
70
shown in FIG.
11
. In
FIG. 12
, the reference numeral
1
designates a light source device;
20
designates a light control filter;
40
designates a wedge lens;
50
designates a correction lens; and
60
designates a mask. Light emitted from the light source device
1
passes through the light control filter
20
, the wedge lens
40
and the connection lens
50
onto the mask
60
. The resultant shadow of the mask
60
is projected onto the inner surface of the CRT panel
70
, whereby a predetermined pattern is exposed to light.
FIG. 13
is a enlarged view of a portion indicated by the arc C
1
of
FIG. 12
, and illustrates paths of light beams passing through the mask
60
in detail. With reference to
FIG. 13
, light of a predetermined color or predetermined wavelength which is emitted from the light source device
1
impinges upon the inner surface of the CRT panel
70
in stripe-shaped configuration conforming to the openings of the mask
60
.
FIG. 14
is a vertical sectional view of the conventional light source device
1
for use in the exposure apparatus shown in
FIG. 12
In
FIG. 14
, the reference numeral
11
designates a rod-shaped mercury light source having a light emitting region extending linearly in the x-direction;
12
designates a light source slit for partially intercepting light emitted from the mercury light source
11
to restrict an apparent light source configuration, and having a centrally located opening for allowing light to pass therethrough; and
13
designates a Light source housing for holding the mercury light source
11
in its interior space by using O-rings
16
. The interior space of the light source housing
13
(having an opening in its upper surface part) in the vicinity of the light emitting region of the mercury light source
11
is filled with a coolant
17
for cooling the mercury light source
11
. The reference numeral
14
designates an optical window having a lower surface for contact with the upper surface part of the light source housing
13
having the opening, with one of the O-rings
16
therebetween, to confine the coolant
17
within the interior space of the housing
13
and to direct the light from the mercury light source
11
through an upper surface thereof into the atmosphere. Additionally, the light source housing
13
includes an inlet and an outlet both not shown of the coolant
17
, and discharges the coolant
17
through the outlet while feeding the coolant
17
through the inlet into the interior space of the housing
13
at a pressure not less than atmospheric pressure, thereby maintaining constant the temperature of the coolant
17
in the light source housing
13
. Thus, since the pressure in the interior space of the light source housing
13
filled with the coolant
17
is always higher than the atmospheric pressure, the optical window
14
is held by an optical window retainer
15
applying a pressure from the atmosphere toward the upper surface part of the light source housing
13
, with the O-ring
16
therebetween. The optical window retainer
15
has a centrally located opening
15
H which is circular in cross section (which is a section parallel to an xy plane), and is screw-held to the housing
13
by means of a threaded groove not shown formed in the light source housing
13
.
In the conventional light source device constructed as above described, it is essential that the optical window retainer is provided on the atmosphere side of the optical window. This presents a problem to be described below.
Detailed consideration of one light profile on the inner surface of the CRT panel being exposed to exposure light emitted from the light source device provides a distribution as shown in FIG.
15
. It will be understood from
FIG. 15
that a pattern width changes depending on the level of illuminance. In other words, when a component other than a predetermined light distribution is superimposed on the illuminance distribution of the exposure light, the distribution of the pattern width within the panel surface shows unevenness corresponding to the superimposed component.
Tracking a light beam emitted from the mercury light source
11
of FIG.
14
and passing through the inside of the coolant
17
and the optical window
14
into the atmosphere provides a light path as shown in FIG.
16
. As illustrated in
FIG. 16
, a light beam
91
generated in a linear light emitting region
111
of the mercury light source
11
and travailing in the region
111
at an angle &thgr;
i
passes through the wall of a synthetic quartz tube
112
surrounding the light emitting region
111
at an angle &thgr;
j
and then through the coolant
17
and the optical window
14
at angles &thgr;
0
and &thgr;
1
respectively, and emerges into the atmosphere at an outgoing angle &thgr;. The ranges of the angles &thgr;
i
, &thgr;
j
, &thgr;
0
, &thgr;
1
and &thgr; of the respective light beams
91
to
95
are calculated below. The angle &thgr;
i
of the light beam
91
emitted from the light emitting region
111
is less than a maximum of ±90° (See Expression (1)) since a light beam having an angular component ranging from 0° to less than 90° can pass through the synthetic quartz tube
112
. The maximum value of the angle &thgr;
j
of the light beam
92
in the synthetic quart tube is ±42.70° (See Expression (2)), and the maximum value of the angle &thgr;
0
of the light beam
93
in the coolant
17
is ±48.28° (See Expression (3)). The maximum value of the angle &thgr;
1
of the light beam
94
in the optical window
14
is ±42.70° (See Expression (4)). The maximum value of the angle &thgr; of the light beam
95
in the atmosphere outside the optical window
14
, which equals the angle &thgr;
i
in the light emitting region
111
as a result of calculation, is less than ±90° (See Expression (1)). That is, the light beam
93
emitted from the mercury light source
11
at the angle of ±48.28° at the maximum spreads out up to an approximately ±90° outgoing angle &thgr; in the atmosphere outside the optical window
14
.
0≦|&thgr;|=|&thgr;
i
&verb
Nishimoto Shigeru
Teramoto Hiroshi
Zumoto Nobuyuki
Mitsubishi Denki & Kabushiki Kaisha
Yun Jurie
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