Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1999-11-24
2003-01-14
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C445S024000, C501S032000, C313S292000
Reexamination Certificate
active
06507148
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel photosensitive paste, a plasma display produced thereof, and a production method thereof.
The photosensitive paste of the present invention is used for pattern formation for various displays, including plasma display and matrix-addressed plasma liquid crystal display, and circuit materials. Such a plasma display can be used in large-size TV sets and computer displays.
BACKGROUND TECHNOLOGY
In the fields of display and circuit material, demands are recently very high for techniques for highly accurate pattern formation with inorganic materials.
As increasingly small, fine-definition products have been developed in the field of display, demands are very high for advanced techniques for accurate pattern formation. For the production of a barrier rib that divides the pixels on the plasma display panel, for example, it has been hoped to develop a material that serves for pattern formation with an inorganic material, such as glass, with a high level of accuracy and a high aspect ratio.
In the field of circuit material, on the other hand, useful techniques have been needed for accurate processing of ceramic substrates on which IC's are to be mounted. Screen printing and punching are currently used for the pattern formation, but more advanced techniques are needed for highly accurate pattern formation as smaller circuit devices are developed.
Conventionally, pattern formation with inorganic material has been frequently performed by screen printing using a paste consisting of inorganic particles and an organic binder, followed by firing. Screen printing, however, is disadvantageous in forming accurate patterns. Another disadvantage is that the formation of a pattern with a high aspect ratio requires many processing steps since multiple-layer printing is necessary.
To solve this problem, U.S. Pat. No. 4,885,963, U.S. Pat. No. 5,209,688, and JP-A-05-342992 have proposed to perform photolithography using a photosensitive paste. Since the photosensitive paste is low in sensitivity and resolution, however, it is impossible to produce a high-definition barrier rib with a high aspect ratio, and therefore, a long process consisting of several steps (coating, exposure, development, etc.) is required to form a pattern on a barrier rib up to a large thickness of, for example, 80 &mgr;m or more.
U.S. Pat. 5,209,688 has also proposed a method in which transfer paper is coated with a photosensitive paste, followed by transferring transfer film onto a glass substrate, and JP-A-03-57138 has proposed a method in which grooves on a photoresist layer are filled with a dielectric paste to form a barrier rib. Also, U.S. Pat. No. 5,116,271 has proposed the use of photosensitive organic film to form a barrier rib. These methods, however, have disadvantages arising from the use of transfer film, photoresist, or organic film which require additional manufacturing processes. It should also be noted that a high-definition barrier rib with a high aspect ratio has not been obtained with these methods.
Furthermore, manufacturing of plasma displays sometimes requires pattern formation of the insulator layer or dielectric layer in addition to the barrier rib, and results in problems similar to those with the barrier rib processing.
SUMMARY OF THE INVENTION
The object of the invention is to provide a photosensitive paste that permits pattern formation with high accuracy and a high aspect ratio, which is made possible by controlling the refractive index of the organic and inorganic components in the photosensitive paste in order to reduce the reflection and scattering at the interface between the organic and inorganic components. Another object of the invention is to provide a high-definition plasma display and a method for the production thereof.
The objects of the invention are achieved by a photosensitive paste comprising, as essential components, inorganic particles and an organic component that contains a photosensitive compound, wherein the average refractive index of the inorganic particles, N1, and the average refractive index of the photosensitive organic component, N2, meet the following equation:
−0.1
≦N
1
−N
2≦0.2
The objects of the invention are also achieved by a photosensitive paste comprising, as essential components, inorganic particles and an organic component that contains a photosensitive compound, wherein the average refractive index of the inorganic particles is in the range of 1.5-1.7.
Furthermore, the objects of the invention are also achieved by a plasma display and its production method wherein the barrier rib is produced by coating a glass substrate with the paste, followed by exposure, development, and firing.
BEST MODE FOR CARRYING OUT THE INVENTION
The photosensitive paste of the invention comprises inorganic particles and an organic component containing a photosensitive compound, and forms an inorganic pattern when sintered after a pattern is formed by photolithography with the photosensitive organic component.
The content of the inorganic particles in the paste should be in the range of 50-98 wt. %, preferably more preferably 70-95 wt. %, in order to reduce the shrinkage in the firing process to minimize the deformation caused by the firing.
The present inventors have carried out detailed studies and found that a pattern with a high aspect ratio can be produced easily by reducing the difference between the average refractive index of the organic component and the average refractive index of the inorganic particles to 0.1 or less, more preferably 0.07 or less.
Also, a pattern with a high aspect ratio can be produced accurately by allowing the average refractive index of the inorganic particles in the photosensitive paste, N1, and the average refractive index of the photosensitive organic component, N2, meet the following equation:
−0.05
≦N
1
−N
2≦0.1
more preferably,
−0.01
≦N
1
−N
2≦0.07
Also, since the organic component can increase in refractive index when polymerized, a pattern with a higher aspect ratio is produced when the following equation is met.
0
≦N
1
−N
2≦0.07
A pattern with a higher aspect ratio can be produced when the refractive index of the organic component polymerized by light irradiation, N3, and the refractive index of the inorganic particles, N1, meet the following equation:
−0.03
≦N
1
−N
3≦0.03
Any ordinary inorganic material can be used as the inorganic particles. Preferred ones include glass, ceramics (alumina, cordylite, etc.), and metals (gold, platinum, silver, copper, nickel, palladium, tungsten, ruthenium oxide, and alloys thereof). Glass and ceramics containing, as an essential component, an oxide of silicon, an oxide of boron, or an oxide of aluminum are particularly preferred. Being insulators, they can be effectively used for producing patterned Insulation materials, Including barrier ribs for plasma displays and matrix-addressed plasma liquid crystal displays.
For the diameter of the inorganic particles, a suitable value is selected by considering the shape of the pattern to be formed. For effective pattern formation, however, it is preferable to use inorganic particles with a 50 wt. % particle diameter of 0.1-10 &mgr;m, a 10 wt. % particle diameter of 0.4-2 &mgr;m, and a 90 wt. % particle diameter of 4-10 &mgr;m, and with a specific surface of 0.2-3 m
2
/g.
The use of spherical inorganic particles permits patterning with a high aspect ratio. Specifically, the sphericity coefficient should preferably be 80% or more. It is more preferred that the average particle diameter, the specific surface, and the sphericity coefficient be 1.5-4 &mgr;m, 0.5-1.5 m
2
/g, and 90% or more, respectively.
The sphericity coefficient to defined as the proportion of those particles which look spherical or ellipsoidal under a microscope. That is, they are observed as round or elliptical objects under an optical microscope.
A pattern with a more accurate shape can be obtained by using glass particles that are produced by crushing glass
Iguchi Yuichiro
Iwanaga Keiji
Masaki Takaki
Morrison & Foerster / LLP
Patel Vip
Toray Industries Inc.
Williams Joseph
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