Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2000-12-13
2001-12-25
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S321000, C445S024000
Reexamination Certificate
active
06333142
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a master for fabricating a mold for transferring barrier ribs and a method for forming barrier ribs of a plasma display panel (PDP) by using the same. More particularly, the present invention relates to a master for fabricating a mold for transferring barrier ribs, the master having convex portions in a barrier rib configuration, and a method for forming barrier ribs of a plasma display panel (PDP) using the transfer mold fabricated with the master.
2. Background Art
The PDP has been given attention as a display panel (low-profile display device) which exhibits an excellent visibility, and its development has been pursued to a high-definition display and a large screen display to foster its versatility in the field of high-definition display in Japan.
The PDP is a display panel of a self-luminous type which has a discharge space defined by a pair of substrates (typically, glass substrates) spaced a minute distance in an opposing relation with the periphery thereof being sealed.
In general, the PDP has partitions (also referred to as barrier ribs) having a height of about 100 &mgr;m to about 200 &mgr;m provided periodically for partitioning the display space. For example, in a PDP of a surface discharge type suitable for fluorescent color display, barrier ribs which are rectilinear as seen in a plan are equidistantly arranged along data electrode lines. The barrier ribs prevent the interference of discharge and the crosstalk of colors.
Various methods for forming barrier ribs have been proposed and carried out. Typical examples include a screen printing method, a sand blasting method, an additive method (a lift-off method) and a photolithographic method.
The screen printing method is a method of forming barrier ribs by laminating a glass paste on a substrate to a predetermined height by screen printing, followed by firing.
The sand blast method is a method for forming barrier ribs by forming a uniform barrier rib material layer on the entire surface of a substrate, forming a mask having a resistance to sandblast on desired portions of the substrate, thereafter, blowing an abrasive material thereon for cutting portions other than the mask, and after the completion of cutting, removing the mask, followed by firing.
The additive method is referred to also as “embedding method” . First, a pattern which is an image of barrier ribs is formed of a photosensitive resist (typically, dry film) on desired sites of a substrate, and a rib material is embedded in gaps between traces of the pattern by using a screen printing method or the like. After the embedding of the rib material, only the photosensitive resist pattern is stripped, and through firing, barrier ribs are formed.
The photolithographic method is a method for forming barrier ribs by coating the entire surface of a substrate with a photosensitive rib paste mixture of a photosensitive resin and a rib material, and exposing and developing a rib pattern. Hitherto, in this method, a thickness of a film which can be exposed at a time is about 20 &mgr;m to about 30 &mgr;m, and therefore exposure and development should be repeated several times to obtain barrier ribs with a desired height.
After the fabrication of a substrate by various methods as mentioned above, the substrate is combined with an opposite substrate and the periphery of the substrates is sealed with a sealing member. A discharge gas is filled in a panel, so that a PDP is completed.
As mentioned hereinabove, various methods have been proposed and performed for the formation of barrier ribs. In any of the methods, however, a large percentage of cost is constituted by indirect materials (a dry film and a rib material to be disposed of) generated in the course of fabrication other than direct materials to form the barrier ribs at a final stage and by consumable items (for example, printing pattern), which prevents the cost reduction.
As a measure for reducing the cost, consideration has been given to a method of forming barrier ribs by transfer. In this method, a model of barrier ribs is produced and, using this model as a master, a mold for barrier ribs is fabricated. Thereafter, a rib material is embedded in the mold and transferred onto a substrate, thereby forming barrier ribs.
If the formation of barrier ribs is intended to be realized by a conventional molding technique, however, it is very difficult to pattern by a machining technique a master for forming barrier ribs (width: 10 &mgr;m-50 &mgr;m, height: 100 &mgr;m-200 &mgr;m, pitch: 100 &mgr;m-400 &mgr;m, area: 0.05 m
2
-0.5 m
2
, arrangement of barrier ribs: parallel or crossing arrangement, etc) required for fabrication of a low-profile display device such as a PDP. It is sometimes extremely difficult at the present level of the technique, depending on a configuration of side walls and an arrangement of the barrier ribs.
Under these circumstances, there has been a demand for a method of easily fabricating a master of barrier ribs for production of a mold of barrier ribs, without using the machining technique.
DISCLOSURE OF INVENTION
The inventors of the present invention have found that the aforementioned problem will readily be solved by fabricating a master of barrier ribs using a photosensitive material, producing a transfer mold (negative-type mold) using the master, and transferring a rib material onto a substrate of a PDP with the mold or pressing the mold against the rib material, thereby forming the barrier ribs.
Furthermore, the inventors have found that in the fabrication of the master of barrier ribs, the utilization of rear-surface exposure and multi-stage exposure ensures the control of a taper angle of the barrier ribs (angle formed by the substrate surface and a barrier rib side face) and the adhesion of the photosensitive material to the substrate, so that a master with a controlled configuration can be produced in an increased yield and with ease.
Thus, the present invention provides a master for a barrier rib transfer mold comprising: a light-transmissive substrate having a predetermined pattern formed of a light-tight material on a surface of the substrate and having a photosensitive material layer formed on the pattern; and convex portions in a desired pattern formed on the substrate by exposing the substrate to light from a rear surface of the substrate, followed by developing.
According to the present invention, a master to be used in a transfer method (including a pressing method), which is an economical and simple method of forming barrier ribs, can easily be fabricated with a good yield. Also, the control of the taper angle of barrier ribs and the formation of a pattern such as a lattice which have been extremely difficult by machining processes can be achieved. In addition, the design of the pattern can readily be modified because the pattern is formed basically by photolithography.
Further, since the photosensitive material layer is exposed to light from the rear surface of the substrate, photopolymerization progresses the most in a contact site of the photosensitive material layer to the substrate. Thereafter, the adhesion between the substrate and the photosensitive material is improved, compared to the case where the exposure is performed from the front surface of the substrate.
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Betsui Keiichi
Otsuka Akihiro
Tokai Akira
Toyoda Osamu
Fujitsu Limited
McPherson John A.
Staas & Halsey , LLP
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