Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1998-03-11
2001-02-27
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C445S052000, C430S024000
Reexamination Certificate
active
06194826
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to processes for preparing a phosphor pattern, the phosphor pattern prepared by the same and a back plate for a plasma display panel.
In the prior art, as one of flat plate displays, there has been known a plasma display panel (hereinafter referred to as “PDP”) which enables multicolor display by providing a phosphor which emits light by plasma discharge.
In PDP, flat front plate and back plate comprising glass are arranged in parallel with each other and facing to each other, both of the plates are retained at a certain interval by a barrier rib provided therebetween, and PDP has a structure that discharge is effected in a space surrounded with the front plate, the back plate and the barrier rib.
In such a space, a phosphor is coated for display, and by discharge, the phosphor emits light by UV ray generated from filler gas, and the light can be recognized by an observer.
In the prior art, as a method for providing the phosphor, a method of coating a slurry solution or paste in which phosphors of the respective colors are dispersed, by a printing method such as screen printing has been proposed and disclosed in Japanese Provisional Patent Publications No. 115027/1989, No. 124929/1989, No. 124930/1989 and No. 155142/1990.
However, the above phosphor-dispersed slurry solution is liquid so that dispersion failure due to precipitation of the phosphors occurs easily, and the slurry solution also has a drawback that when a liquid photosensitive resist is used in the slurry solution, storage stability is poor due to acceleration of a dark reaction or the like. Further, the printing method such as screen printing is inferior in printing precision so that there are problems that it is difficult to cope with enlargement of a screen of PDP in the future, and others.
In order to solve these problems, there has been proposed a method of using a photosensitive element (which is also called as a photosensitive film) containing a phosphor (Japanese Provisional Patent Publication No. 273925/1994).
In the method of using a photosensitive element, only a phosphor-containing photosensitive resin layer of a photosensitive element comprising a photosensitive resin layer containing a phosphor and a support film is embedded in the space of the above substrate for PDP by contact bonding (lamination) under heating, the layer is subjected to imagewise exposure with active light such as UV ray by a photographic method using a negative film, an unexposed portion is removed by a developing solution such as an alkaline aqueous solution, and further unnecessary organic components are removed by calcination to form a phosphor pattern only at a necessary portion.
In the method using such a photosensitive element, the photographic method is used so that a phosphor pattern can be formed with good precision.
However, when a phosphor-containing photosensitive resin layer is formed on the above-mentioned substrate for PDP by using the photosensitive element, then imagewisely exposing active light through a photomask, and subjecting to development and calcination according to the conventional method, it is difficult to form a phosphor pattern with uniform thickness and shape over the surface of a concave portion surrounded by the wall surface of a barrier rib and the bottom of the space since the photocurability at the wall surface portion of the barrier rib which is inside surface of the concave portion which space becomes a discharging space is lower than that of the bottom of the substrate so that the photosensitive resin layer containing the phosphor at the wall portion of the barrier rib is liable to be eroded at development.
SUMMARY OF THE INVENTION
The present invention is to provide a process for preparing a phosphor pattern, in which a phosphor pattern can be formed in a space of a substrate having unevenness such as a substrate for PDP on the whole inner surface of the concave portion with good yield, uniform film thickness with good flexibility.
The present invention is further to provide a process for preparing a phosphor pattern which is more excellent in simplicity and easiness, more excellent in pattern precision, operatability, more excellent in process flexibility, productivity, and excellent in suppressing decrease of a film thickness in addition to the effects as mentioned above.
The present invention is to provide a phosphor pattern which is high precision, uniform shape and excellent in luminance.
The present invention is to provide a back plate for a plasma display panel provided with a phosphor pattern which is high precision, uniform shape and excellent in luminance.
A process for preparing a phosphor pattern of the present invention comprises the steps of
(I) forming a phosphor-containing photosensitive resin composition layer (A) on a substrate having unevenness,
(II) irradiating a scattered light to the phosphor-containing photosensitive resin composition layer (A) imagewisely,
(III) developing the phosphor-containing photosensitive resin composition layer (A) by removing the portion to which the scattered light is imagewisely irradiated to form a pattern, and
(IV) calcinating the formed pattern to remove an unnecessary portion from the pattern formed in the step (III) to form a phosphor pattern.
In the present invention, the above step (I) preferably I comprises a step of laminating a photosensitive element which has the phosphor-containing photosensitive resin composition layer (A) having a support so as to oppose the substrate having unevenness to the photosensitive resin composition layer (A) of the photosensitive element.
The above step (II) preferably comprises (IIa) irradiating active light to the phosphor-containing photosensitive resin composition layer (A) through a photomask provided on the photosensitive resin composition layer and a sheet having a light scattering function provided on the photomask.
Also, the above step (II) preferably comprises (IIb) irradiating active light to the phosphor-containing photosensitive resin composition layer (A) through a sheet having a light scattering function provided on the photosensitive resin composition layer and a photomask provided on the sheet.
Also, the above step (II) preferably comprises (IIc) irradiating active light to the phosphor-containing photosensitive resin composition layer (A) through a photomask in which the light transmission portion has a light scattering function provided on the photosensitive resin composition layer.
In the present invention, the width of the photomask at the light transmission portion is narrower than that of an opening at the concave portion of the substrate.
The present invention also relates to the phosphor pattern which comprises repeating the above steps (I) to (III) to form a multi-colored pattern comprising photosensitive resin composition layers containing phosphors which form colors of red, green and blue, and then subjecting the above step (IV) to form a multi-colored phosphor pattern.
The present invention further relates to the phosphor pattern which comprises repeating the above steps (I) to (IV) to form a multi-colored phosphor pattern which forms colors of red, green and blue.
The present invention further relates to the process mentioned above, wherein the phosphor-containing photosensitive resin composition layer (A) contains:
(a) a “film property-imparting polymer”,
(b) a photopolymerizable unsaturated compound having an ethylenically unsaturated group,
(c) a photopolymerization initiator which forms free radical by irradiation of the active light, and
(d) a phosphor.
The present invention further relates to the phosphor pattern produced by the above-mentioned processes for preparing the phosphor pattern.
The present invention further relates to a back plate for the plasma display panel provided with the above-mentioned phosphor patterns on the substrate for plasma display panel.
REFERENCES:
patent: 5698268 (1997-12-01), Takagi
patent: 5858616 (1999-01-01), Tanaka et al .
patent: 0768573A1 (1997-04-01), None
patent: 0785565A1 (
Ashizawa Toranosuke
Kimura Naoki
Mukai Ikuo
Nojiri Takeshi
Satou Kazuya
Antonelli Terry Stout & Kraus LLP
Gerike Matthew J.
Hitachi Chemical Co. Ltd.
Patel Nimeshkumar D.
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