Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-10-29
2004-08-31
Berman, Susan (Department: 1711)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C522S025000, C522S015000, C522S129000, C522S146000, C522S168000, C522S170000, C430S280100, C528S406000, C528S417000
Reexamination Certificate
active
06783840
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resist ink composition for use in the process of producing a printed circuit board, and a method for obtaining a cured film using the composition. More specifically, the present invention relates to a resist ink composition capable of forming an image under exposure to an ultraviolet light, having high sensitivity and capable of being cured by a short heat curing treatment following the formation of a pattern; as well as to a cured film using the composition; and to a method for producing the cured film.
BACKGROUND ART
In recent years, with the progress of techniques for forming a finer pattern for a printed wiring board circuit to cope with the downsizing and higher performance of electrical instruments, the material used for a solder resist is required to have processability in a micro-order. The solder resist is used to provide a film on the front surface portion of a circuit conductor except the portions for soldering, and prevents the solder from attaching to undesirable portions when soldering electric parts to a printed wiring board, and also functions as a protective film to prevent the circuit conductor from being exposed directly to air and being corroded by oxidation or moisture. The solder resist is heretofore mainly applied to a printed board by a screen printing method to form a pattern and then cured by ultraviolet light or heat. However, due to the requirements of higher resolution and higher precision, attention is being focused on a liquid photosolder resist method, irrespective of either for a civil board or for an industrial board.
This photosolder resist is generally formed into a pattern using a photosensitive resin comprising a radical polymerization initiator and a resin having a (meth)acrylate group. However, printed boards are moving toward finer patterns and higher functions and, with this tendency, as described in JPP-61-243869 (the term “JPP” as used herein means an “Japanese Unexamined Patent Publication (Kokai)”), a composition prepared by mixing an epoxy resin having low curing shrinkage and excellent electrical properties with a composition comprising a photo-radical polymerization initiator and a resin having a (meth)acrylate group is becoming the main photosensitive resin composition.
However, in view of forming a pattern under light irradiation within a short time, there is a limit in reducing the blending amount of the resin having a (meth)acrylate group, and therefore, this method of adding an epoxy resin fails to satisfy both productivity and resistance against water or hydrolysis requirements at the same time.
On the other hand, from the standpoint of providing a high-density printed board, studies have been made to develop a multilayer laminate board. In conventional techniques, a printed board is produced by contact bonding printed wiring boards together, making holes therein using a drill, and then laminating these boards. However, to meet the requirement for further higher density, printed boards are produced by a method where a heat-curable epoxy resin is used as the insulating layer, and after punching holes by a carbonic acid gas laser, the boards are subjected to laminated plating. This method, including punching holes by a laser, has a problem in that the size of the via hole cannot be reduced and the equipment is very expensive. Thus, an alternative method is being demanded. To satisfy this requirement, investigations have been made for a method where a fine pattern can be formed and an inexpensive photosensitive resin is used.
JPP-10-186656 discloses a photosensitive resin composition for use in the production of a multilayer wiring board, which mainly comprises a (meth)acrylate resin similar to the solder resist. However, an interlayer insulation film requires a higher water resistance, a higher hydrolysis resistance and a lower curing shrinkage in comparison with the solder resist, and therefore, it is difficult to simultaneously satisfy the requirements for both the productivity and the physical properties. To overcome this problem, a method using an epoxy resin as the main component, which provides a cured product having good physical properties, wherein a pattern is formed by photocationic curing, has been proposed (see, JPP-8-211610 and JPP-10-97068). However, the photocationic curing reaction of the epoxy resin proceeds slowly, and therefor a fine pattern cannot be formed by exposure to light in a short time.
As such, conventional photosensitive resins comprising a resin having a (meth)acrylate group as the main component and a photo-radical polymerization initiator cannot satisfy the requirement for highly functional cured product, whereas photosensitive resins comprising an epoxy resin as the main component which can be cured by cationic curing have a problem in that the photosensitivity is poor and a fine pattern cannot be formed, even though the cured product thereof has good physical properties.
In recent years, a radiation-sensitive resin composition for use in the insulating layer-forming material has become known (see, JPP-11-60683 and JPP-11-65116), in which a compound having an oxetane ring is used. However, this resin still cannot satisfy the productivity and the profitability requirements because an extended high-temperature treatment is necessary for obtaining a cured product, and also a heat cationic polymerization initiator must be used in a large amount.
U.S. Pat. No. 3,388,105 describes a technique of curing a compound having an oxetanyl group and an epoxy group within the same molecule by addition-reacting this compound with a carboxyl group-containing compound under heat. However, it is not known that this compound having an oxetanyl group and an epoxy group within the same molecule exhibits very high activity (curability) in the cationic ring-opening polymerization nor is it particularly suitable as a constituent component of a resist material which can be heat-treated within a short time and ensure excellent various properties.
DISCLOSURE OF THE INVENTION
The present invention has been made under these circumstances, and the object of the present invention is to provide a resist ink composition which can form an image by exposing it to an ultraviolet light for a short time, followed by development with an organic solvent or a dilute alkali aqueous solution. By a short time-heat treatment following the formation of a pattern, this composition can provide a solder resist or an interlayer insulation material excellent in various properties such as adhesive property, soldering resistance, pressure cooker test (PCT) durability and low water absorptivity.
As a result of extensive investigations to solve the above-described problems, the present inventors have found that these problems can be overcome by a specific photosensitive resin composition comprising a compound (a) having at least one oxetanyl group and at least one epoxy group within the same molecule. The present invention has been accomplished based on this finding.
More specifically, the present invention relates to a resist ink composition, a cured product thereof and a method for producing the cured product, as described in the following items [1] to [20].
[1] A resist ink composition comprising a compound (a) having at least one oxetanyl group and at least one epoxy group within the same molecule.
[2] A resist ink composition comprising a compound (a) having at least one oxetanyl group and at least one epoxy group within the same molecule, wherein said compound (a) is a compound represented by formula (1):
wherein R represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, and n is 2 when m is 0, and otherwise n is 1.
[3] A resist ink composition comprising a compound (a) having at least one oxetanyl group and at least one epoxy group within the same molecule, wherein said compound (a) is 7,8-epoxy-2-oxa-5-methylspiro[3.5]nonane and/or 6,7-epoxy-2-oxaspiro[3.5]nonane.
[4] The resist ink c
Sato Takashi
Tagoshi Hirotaka
Watanabe Takeo
Berman Susan
Showa Denko K.K.
Sughrue & Mion, PLLC
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