Radiation imagery chemistry: process – composition – or product th – Imaged product – Structurally defined
Reexamination Certificate
2001-04-24
2004-06-29
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaged product
Structurally defined
C430S311000, C430S280100, C430S014000, C430S018000
Reexamination Certificate
active
06756165
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation sensitive resin composition for forming barrier ribs for an EL display element, barrier rib and EL display element. More specifically, it relates to a radiation sensitive resin composition suitable for use as a material for forming barrier ribs for an EL display element, a barrier rib formed therefrom and an EL display element comprising the same.
2. Prior Art
Generally speaking, the micro-patterning of the cathode and organic EL medium layer of an organic EL element is difficult because the heat resistance (generally 100° C. or lower), solvent resistance and moisture resistance of an organic EL medium used in a charge injection layer and light emitting layer are low. For example, when photolithography generally used for the patterning of a thin film is used for an organic EL element, deterioration in the characteristic properties of the organic EL element are caused by the permeation of a solvent contained in a photoresist into the organic EL element, high-temperature atmosphere during the baking of the photoresist, the permeation of a photoresist developer or etching solution into the organic EL element, or the damage of the organic EL element by plasma during dry etching.
Patterning may be carried out using a deposition mask. However, a fine pattern cannot be formed due to such problems that a short circuit occurs between an anode and a cathode made from indium tin oxide (to be abbreviated as ITO hereinafter) by the entry of a deposited product between a substrate and a mask caused by poor adhesion between the substrate and the deposition mask or the organic EL medium layer scratched by its contact with the mask when the substrate and deposition mask are forcedly brought into close contact with each other and that the mask bends due to its insufficient strength when the openings of a striped pattern for the cathode are large and the mask portion is a fine pattern.
To solve the above problems, for example, JP-A 2-66873 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method for patterning a photoresist comprising a solvent which does not dissolve an organic EL medium on the organic EL element and etching a cathode using dilute sulfuric acid. However, the organic EL medium is damaged by diluted sulfuric acid during etching.
JP-A 5-275172, JP-A 5-258859 and JP-A 5-258860 disclose a patterning method in which having a sectional shape of normally tapered barrier ribs and having a height of several to several tens of micrometers which are arranged on a substrate in parallel to one another are formed after ITO patterning and an organic EL medium and a cathode material are deposited on the substrate from a direction perpendicular to the barrier ribs and an oblique direction with respect to the surface of the substrate for patterning. That is, there is used a method such that a first electrode line and an thin film of the organic EL medium are selectively formed by oblique vacuum deposition by intercepting a predetermined gas stream with high barrier ribs at boundaries formed on the substrate to prevent spaces defined by the barrier ribs from being polluted during deposition. However, this oblique deposition method has such a defect that the brightness of a display element becomes insufficient due to the formation of an organic EL medium free portion in an opening between barrier ribs. JP-A 8-315981 overcomes the above defect of oblique deposition by using barrier ribs having an overhung sectional form (trapezoidal form having a shorter bottom side than a top side) to make possible vacuum deposition from above. However, as the formed barrier ribs are transparent, light emitted from the organic EL element passes through the barrier ribs, thereby making it difficult to prevent a reduction in the contrast of emitted light. General resist materials may have such problems that they cannot retain an inversely tapered form due to softening at the time of curing because they have low heat resistance and that when a volatile component from the material of the barrier ribs is contained in the EL layer as an impurity, the light emission area of the EL emission element reduces or a lighting failure occurs.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention which has been made in view of the above situation to provide a radiation sensitive resin composition for forming barrier ribs for an EL display element which have required heat resistance, adhesion and an inversely tapered form.
It is another object of the present invention to provide a radiation sensitive resin composition for forming barrier ribs for an EL display element which further have light screening properties to prevent a reduction in contrast, required heat resistance, adhesion and an inversely tapered form.
It is still another object of the present invention to provide barrier ribs formed from the above radiation sensitive resin composition and an EL display element comprising the barrier ribs.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a radiation sensitive resin composition for forming barrier ribs for an EL display element, comprising:
(A) an alkali soluble resin;
(B) a polymerizable compound having an ethylenically unsaturated bond; and
(C) a radiation sensitive polymerization initiator.
Secondly, the above objects and advantages of the present invention are attained by barrier ribs for an EL display element which are formed from the radiation sensitive resin composition of the present invention.
Thirdly, the above objects and advantages of the present invention are attained by an EL display element comprising the barrier ribs of the present invention.
The EL display element of the present invention includes an organic EL display element and inorganic EL display element, out of which an organic EL display element is preferred.
Each component of the radiation sensitive resin composition of the present invention will be described in detail hereinbelow.
Alkali Soluble Resin (A)
Any alkali soluble resin may be used as the alkali soluble resin used in the present invention if it is alkali-soluble.
The alkali soluble resin is preferably a novolak resin, a homopolymer of a radical polymerizable monomer having a phenolic hydroxyl group or carboxyl group, a copolymer of the radical polymerizable monomer and another radical polymerizable monomer, or a copolymer of at least one selected from the group consisting of an unsaturated carboxylic acid and unsaturated carboxylic anhydride, an epoxy group-containing unsaturated compound and another olefinic unsaturated compound other than these unsaturated compounds.
The novolak resin is alkali-soluble and obtained by polycondensing a phenol, preferably a phenol including m-cresol with an aldehyde. Examples of the phenol other than m-cresol used in the production of the novolak resin (to be simply referred to as “phenolic monomer” hereinafter) include phenol, p-cresol, o-cresol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, catechol, resorcinol, hydroquinone, methylhydroquinone, pyrogallol and phloroglucinol. These phenolic monomers may be used alone or in combination of two or more, preferably in combination with m-cresol.
The molar ratio of m-cresol/the phenolic monomer is preferably 20/80 to 100/0, more preferably 30/70 to 100/0. When the amount of m-cresol is smaller than 20 mol %, a tendency toward a reduction in the resolution of the composition is seen.
The novolak resin of interest is obtained by polycondensing the above phenol and an aldehyde such as formaldehyde or acetaldehyde in the presence of an acid catalyst such as oxalic acid.
Although water is generally used as a reaction medium for the polycondensation reaction, when the phenol used in the polycondensation reaction does not dissolve in an aque
Endo Masayuki
Nishimura Isao
Suzuki Masayoshi
Hamilton Cynthia
JSR Corporation
LandOfFree
Radiation sensitive resin composition for forming barrier... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation sensitive resin composition for forming barrier..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation sensitive resin composition for forming barrier... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3342396