Radiation imagery chemistry: process – composition – or product th – Producing cathode-ray tube or element thereof – Using specific control or specific modification of exposure,...
Reexamination Certificate
2001-01-03
2004-01-27
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Producing cathode-ray tube or element thereof
Using specific control or specific modification of exposure,...
Reexamination Certificate
active
06682864
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a bulb for a color cathode ray tube and a color cathode ray tube, and also relates to methods for the production thereof.
For example, in a bulb for a color cathode ray tube having a color selection member of aperture grille type, generally, an inner surface of a face plate has, for example, stripe-shaped fluorescent material layers for red, green and blue and a black-matrix (stripe-shaped light absorption black layer) present between one of the fluorescent material layers and another. And, an electron gun is incorporated into the above bulb, and the inside of the bulb is vacuumed, whereby a color cathode ray tube is completed. The method of forming the above stripe-shaped color fluorescent layer will be explained with reference to schematic partial end views of the face plate, etc., shown in
FIGS. 47A
to
47
C and
FIGS. 48A and 48B
. The above stripe-shaped color fluorescent layer is formed by means of an opening portion, more specifically, by means of a face plate
11
to which a color selection member
13
of aperture grille type having stripe-shaped slits
14
extending in parallel with the perpendicular direction of the face plate
11
is attached.
FIG. 47B
alone shows the color selection member
13
.
First, a light sensitive film
20
is applied to the inner surface of the face plate
11
and dried (see FIG.
47
A), and then, a stripe-shaped exposed region
21
is formed in the light sensitive film
20
with an ultraviolet light which is emitted from an exposure light source (not shown) and passes through the stripe-shaped slit
14
formed in the color selection member
13
(see FIG.
47
B). For forming fluorescent material layers for red, green and blue, the above exposure is carried out three times by changing the exposure light source in position for each time. Then, the light sensitive film
20
is developed and selectively removed, to retain a remaining portion (exposed and developed light sensitive film)
22
on the inner surface of the face plate
11
(see FIG.
47
C). Then, a carbon agent is applied to the entire surface, and the remaining portion
22
of the light sensitive film and the carbon agent thereon are removed by a lift-off method, to form a stripe-shaped black-matrix
23
composed of the carbon agent (see FIG.
48
A). Then, fluorescent material layers
24
for red, green and blue are formed on the exposed inner surfaces of the face plate (portion
11
B of exposed inner surface of the face plate
11
, the portion
11
B being present between one black-matrix
23
and another black-matrix
23
) (see FIG.
48
B). Specifically, for example, a photosensitive fluorescent material slurry for red is applied to the entire surface, exposed to a light and developed, then, a photosensitive fluorescent material slurry for green is applied to the entire surface, exposed to a light and developed, and further, a photosensitive fluorescent material slurry for blue is applied, exposed to a light and developed.
In the above exposure method, an ultraviolet light emitted from one exposure light source is used. In some optical dimensions of a bulb for a color cathode ray tube, an exposure intensity of a transmitted light (exposure dosage on the light sensitive film
20
) of an ultraviolet light through the slit
14
which is an opening portion formed in the color selection member
13
, has a distribution of a Fresnel diffraction wave as is schematically shown in FIG.
52
A. The above Fresnel diffraction is known as near-field diffraction, and generally is obtained when an observation screen is located in a finite distance from a diffraction aperture. In the graph of the exposure intensity of the transmitted light in
FIG. 52A
, the axis of abscissas shows the horizontal direction of the face plate and the axis of ordinates show the exposure intensity of the transmitted light. Further, the origin is the center of the stripe-shaped exposed region of the light sensitive film.
When the above light sensitive film
20
is exposed to a light, developed and selectively removed, heavy convexo-concave shapes are formed in edge portions of the remaining portion
22
of the light sensitive film (see FIG.
52
B). The above phenomenon is caused by the formation of stripe-shaped edge portions of the exposed region
21
on the basis of an area of a transmitted-light strength in which area the derivative of the first order (∂I/∂x) of the transmitted-light strength on the light sensitive film
20
has an extremely small value. In the above expression, “I” stands for a transmitted-light intensity (in other words, exposure dosage on the light sensitive film
20
) and “x” stands for an electron beam sweep direction, specifically, the horizontal direction of the face plate
11
. If the derivative of the first order (∂I/∂x) of the transmitted-light strength on the light sensitive film
20
comes to be an extremely small value, the value of the derivative of the first order of crosslinking degree distribution of the light sensitive film
20
comes to be small (that is, the crosslinking degree distribution of the light sensitive film
20
in the horizontal direction of the face plate
11
loses steepness), so that the heavy convexo-concave shapes are formed in the edge portions of the remaining portion
22
of the light sensitive film. As a result, the edge portions of the stripe-shaped fluorescent material layer
24
cause heavy convexo-concave shapes, macroscopically, an image display non-uniformity is caused in a color cathode ray tube, and the color cathode ray tube is extremely deteriorated in quality.
JP-A-60-84738 discloses a method for avoiding the above phenomenon. In the method disclosed in the above Laid-Open publication, a plurality of exposure light sources are arranged in different positions along the horizontal direction of the face plate, and a light sensitive film formed on an inner surface of a face plate is exposed to a predetermined stripe width using a transmitted-light strength distribution of superposed Fresnel diffraction waves. And, a correction lens system for correcting Fresnel diffraction conditions of each is selected depending upon an exposure light in the position of each exposure light source, and a plurality of exposure lights emitted from a plurality of the exposure light sources are adjusted such that Fresnel diffraction waves are superposed on the light sensitive film through the correction lens system and the color selection member for one stripe having a predetermined width. Further, a plurality of the exposure lights are adjusted such that the transmitted-light strength distribution is nearly constant on the entire surface of the light sensitive film formed on the inner surface of the face plate, and further that exposure is effected in a state where a differential value (∂i/∂x) of the transmitted-light strength distribution on a position corresponding to the edge of the stripe width is a value near a peak of the distribution of the differential value (∂i/∂x) or a value that has a certain level sufficient for preventing an edge non-uniformity of the stripe width.
The method disclosed in the above Laid-Open publication is effective for preventing the heavy convexo-concave shapes which occur in the edges of the remaining portion of the light sensitive film. It is remarkably suitable for producing a so-called commercial color cathode ray tube in which slits of a color selection member in a central portion of a bulb for a color cathode ray tube have a rough pitch or a color cathode ray tube for a computer display in which slits have a fine pitch. However, slits of a color selection member in a central portion of a bulb for a color cathode ray tube for digital broadcasting have a semi-fine pitch, and the semi-fine pitch is in an intermediate range between the pitch of slits of the color selection member in the commercial color cathode ray tube and the pitch of slits of the color selection member in the high-resolution color cathode ray
Tsunoda Seiichi
Uesugi Masanao
Maioli Jay H.
McPherson John A.
Sony Corporation
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