Co-reporter:Masamitsu Shirai;Haruyuki Okamura
Polymer International 2016 Volume 65( Issue 4) pp:362-370
Publication Date(Web):
DOI:10.1002/pi.5065
Abstract
One of the most interesting application areas of screen printing is the production of microelectronic devices. Although negative photoresists are commonly used for the screen printing plate, their resolution limit is about 30 µm. A higher resolution of resist patterns on the screen plate is essential for microelectronic device applications. This paper describes the novel design of a UV-curable positive photoresist and its application to the screen printing plate. Positive patterns on the screen plate were obtained by conventional photolithography using a photomask and 365 nm light and the patterns were exposed to 254 nm light to enhance the mechanical strength of the resist patterns. It was essential to use photoacid generators sensitive to 365 nm and photoradical generators sensitive to 254 nm. A screen printing plate, which enabled the formation of 6 µm wide conductive lines, was developed. © 2016 Society of Chemical Industry
Co-reporter:Masamitsu Shirai
Polymer Journal 2014 46(12) pp:859-865
Publication Date(Web):September 3, 2014
DOI:10.1038/pj.2014.79
Photocrosslinkable polymers and ultraviolet (UV)-curable resins are significant applications such as coatings, adhesives, photoresists and printing plates. Crosslinked polymers are insoluble and infusible; therefore, it is very difficult to remove crosslinked materials from substrates. Recently, much attention has been paid to the recovery or recycling of crosslinked polymers due to environmental regulations. To this end, photocrosslinkable polymers with degradable properties have been studied. Photocrosslinkable polymers and UV-curable resins with degradable properties are also realized as highly functionalized photopolymers. This article reviews our recent research on photocrosslinkable polymers with degradable properties. Multifunctional methacrylates and epoxides with degradable properties were prepared, and their UV-curing and degradation profiles were studied. Furthermore, polymers with crosslinkable units and degradable side chains were prepared and characterized in a similar manner. Some potential applications of these monomers and polymers were also described.
Co-reporter:Haruyuki Okamura;Minoru Kayanoki;Kohei Takada;Hideyuki Nakajiri;Keiko Muramatsu;Munenori Yamashita
Polymers for Advanced Technologies 2012 Volume 23( Issue 8) pp:1151-1155
Publication Date(Web):
DOI:10.1002/pat.2015
High-resolution screen printing was devised. New resist formulation contains a base polymer, which consists of acid-labile tetrahydropyranyl-protected carboxylic acid, hydroxyl, and methacrylic functions. As crosslinkers, multifunctional acrylates were employed. Photoacid generators were used for pattern formation. A 10-µm feature size of resist on a screen plate was obtained on irradiation at 365 nm and followed by development on a stainless steel screen. Post-exposure curing improved the mechanical characteristics of the resist patterns. A 13-µm feature size silver circuit was successfully printed on poly(ethylene terephthalate) film without defect. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Daisaku Matsukawa, Haruyuki Okamura and Masamitsu Shirai
Journal of Materials Chemistry A 2011 vol. 21(Issue 28) pp:10407-10414
Publication Date(Web):09 Jun 2011
DOI:10.1039/C0JM04386A
Four types of reworkable dimethacrylates bearing hemiacetal ester groups were synthesized and the UV curing and degradation were studied. UV nanoimprint lithography (UV-NIL) using these monomers was performed and fine line/space patterns were obtained. The shrinkage in height of the UV imprinted pattern was studied in relation to the monomer structure and UV imprint conditions such as light intensity and concentrations of photoradical initiator and chain transfer reagent. The effect of UV imprint conditions on the kinetic chain length of UV cured networks was investigated using size exclusion chromatography of the linear polymers obtained from the degradation of the UV imprinted patterns. A relationship between the kinetic chain length and shrinkage of the UV imprinted patterns was discussed.
Co-reporter:Hironori Matsushima, Sukhendu Hait, Qin Li, Hui Zhou, Masamitsu Shirai, Charles E. Hoyle
European Polymer Journal 2010 Volume 46(Issue 6) pp:1278-1287
Publication Date(Web):June 2010
DOI:10.1016/j.eurpolymj.2010.03.003
Non-extractable photoinitiators could be advantageous for use in biological, electronic, and food packaging applications. Therefore, thioxanthone and benzophenone derivatives were synthesized from 1,6-hexane dithiol and chlorinated benzophenone or thioxanthone. The efficiency of thiol-functionalized photoinitiators in combination with amine co-initiators was compared to benzophenone and isopropylthioxanthone with amine co-initiators, and the cleavage of photoinitiator 2,2-dimethoxy-1,2-diphenylethan-1-one in acrylic resins. The reaction kinetics were analyzed using photo-differential scanning calorimetry and real-time FTIR. Coating physical properties were evaluated by pendulum and pencil hardness, steel–wool scratch and mandrel bend tests. The non-extractable photoinitiators had higher absorbance than their benzophenone or isopropylthioxanthone counterparts due to the sulfide substitution on the phenyl ring, and the free thiol groups reacted with the acrylate by either an amine catalyzed Michael addition or a free-radical chain process. The combination of thiol-functionalized photoinitiators with secondary amines provides an efficient photoinitiator system that is locked into the photopolymerized network and cannot be extracted with typical solvents.
Co-reporter:Daisaku Matsukawa;Haruyuki Okamura
Polymer International 2010 Volume 59( Issue 2) pp:263-268
Publication Date(Web):
DOI:10.1002/pi.2719
Abstract
The aim of the study reported in this paper was to develop new di(meth)acrylates having aromatic units and thermally degradable units in their molecules. It was also the aim to clarify the photo-curing and degradation properties of the new monomers. Di(meth)acrylates having aromatic units and thermally degradable units were synthesized. As thermally cleavable linkages, tertiary ester moieties were incorporated into the di(meth)acrylates. Three types of processes for curing and degradation of the cured resins were studied: thermal curing and thermal degradation; thermal curing and photodegradation; and photo-curing and thermal degradation. In the thermal curing and photodegradation process, di(meth)acrylate films containing a thermally induced radical initiator and a photoacid generator (PAG) became insoluble in solvents on heating. The cured films became soluble in solvents after ultraviolet irradiation followed by baking. The re-dissolution behaviors were strongly affected by the structures of the PAGs. A mechanism for the photo- or thermo-curing and photoassisted thermal degradation was studied using Fourier transform infrared, 1H NMR, thermogravimetric, mass spectrometric and size exclusion chromatographic analyses. Copyright © 2009 Society of Chemical Industry
Co-reporter:Daisaku Matsukawa, Hiroyuki Wakayama, Kazuyuki Mitsukura, Haruyuki Okamura, Yoshihiko Hirai and Masamitsu Shirai
Journal of Materials Chemistry A 2009 vol. 19(Issue 24) pp:4085-4087
Publication Date(Web):20 May 2009
DOI:10.1039/B905188K
Difunctional methacrylate monomers having a hemiacetal ester moiety in the molecule were used to prepare a plastic replica of an original mold for imprint lithography. UV curing of the monomers was performed with 365 nm light and photo-induced degradation of the cured resins was performed using 254 nm light.
Co-reporter:Masamitsu Shirai, Haruyuki Okamura
Progress in Organic Coatings 2009 Volume 64(2–3) pp:175-181
Publication Date(Web):February 2009
DOI:10.1016/j.porgcoat.2008.08.026
UV curing systems based on cationic processes are very significant because the systems have several advantages compared to the radical process. Photoacid generator (PAG) is essential for the cationic UV curing system including epoxides and vinyl ethers. Although many types of PAG have been developed, most of them are not sensitive to i-line (365 nm) from a high-pressure mercury lamp. In this study, non-ionic PAG that is thermally stable and highly sensitive to i-line was designed and synthesized. Imino sulfonate and N-hydroxyimide sulfonate compounds were prepared as PAG. Fluorenone, thioxanthone, and thianthrene skeletons were used as chromophores for PAG. Furthermore, photochemistry of the PAG and its applications to photocrosslinking systems based on epoxy-containing polymers were studied.
Co-reporter:Daisaku Matsukawa, Tomoya Mukai, Haruyuki Okamura, Masamitsu Shirai
European Polymer Journal 2009 Volume 45(Issue 7) pp:2087-2095
Publication Date(Web):July 2009
DOI:10.1016/j.eurpolymj.2009.03.015
Two types of oligo(hemiacetal ester)s which have methacrylate units and tertiary ester linkages in the side chains were synthesized by polyaddition of corresponding dicarboxylic acid with divinyl ether. One oligomer has a ortho linked main-chain structure, and the other one has meta and para linked main-chain structure. These oligomers were applied to a photocrosslinking system having photo/thermal degradable properties. On UV irradiation at 365 nm under N2 atmosphere, oligomer films containing methyladamantyl methacrylate (MADMA), 2,2-dimethoxy-2-phenylacetophenone (DMPA), triphenylsulfonium triflate (TPST) became insoluble in acetone. Insolubilization behavior was not influenced by the difference of main-chain structure. When the crosslinked oligomer/MADMA films were irradiated at 254 nm and followed by baking, they became soluble in acetone. The effective baking temperature depended on the oligomer structure. The cleavage of hemiacetal ester and tertiary ester linkages was confirmed by FT-IR spectroscopy.
Co-reporter:Haruyuki Okamura;Toru Terakawa
Research on Chemical Intermediates 2009 Volume 35( Issue 8-9) pp:
Publication Date(Web):2009 November
DOI:10.1007/s11164-009-0070-4
Tri-functional methacrylate (MA3) having thermally degradable tertiary ester linkages was synthesized by a convergent approach. When the MA3 film containing a thermal initiator and a photoacid generator was heated under nitrogen atmosphere, it became insoluble. The thermally cured MA3 became soluble after irradiated and followed by baking at 120 °C. Acid catalyzed decomposition of the tertiary ester linkages of the MA3 moiety occurred at lower temperatures than non-catalyzed one. A mechanism for the photo- or thermal curing and photoassisted-thermal degradation was studied by FT-IR, 1H NMR, TGA, MS, and SEC analyses.
Co-reporter:Masamitsu Shirai, Kazuyuki Mitsukura and Haruyuki Okamura
Chemistry of Materials 2008 Volume 20(Issue 5) pp:1971
Publication Date(Web):January 31, 2008
DOI:10.1021/cm702965e
Novel difunctional (meth)acrylates that are thermally degradable were designed and synthesized to study the kinetic chain length of the UV cured resins. These monomers have both hemiacetal ester moiety as a degradable unit and acrylate or methacrylate unit as a polymerizable unit. The UV curing property of these monomers was studied under N2 atmosphere. A linear polymer, i.e., poly(methacrylic acid) or poly(acrylic acid), was obtained by the thermal degradation of the UV cured resins. Poly(methacrylic acid) and poly(acrylic acid) were converted to poly(methyl methacrylate) and poly(methyl acrylate), respectively, by treating with a diazomethane reagent. To obtain the kinetic chain length for the photopolymerization of difunctional (meth)acrylates, we performed size exclusion chromatography. It was shown that the kinetic chain length of the UV cured resins was affected by the monomer structure, concentration of initiator, exposure dose intensity, and conversion. Furthermore, the kinetic chain length for the UV cured resins was compared with that for the thermally cured resins.
Co-reporter:Masamitsu Shirai
Progress in Organic Coatings 2007 Volume 58(2–3) pp:158-165
Publication Date(Web):1 February 2007
DOI:10.1016/j.porgcoat.2006.08.022
Novel UV curing materials which became soluble in solvents by photo/thermal degradation were studied. Three types of systems were designed and prepared, i.e. (a) base polymer/crosslinker blended system, (b) functionalized polymer system, and (c) multifunctional acrylate monomer system. In the base polymer/crosslinker blended system, as a crosslinker, multifunctional epoxy compounds containing tertiary esters of carboxylic acid or sulfonate ester units were synthesized and used in combination with polyvinylphenol. Functionalized polymers bearing epoxy units and thermally degradable linkages in the side chain were prepared. Furthermore, multifunctional methacrylate or acrylate monomers bearing acetal linkages in a molecule were prepared. Photocrosslinking and thermal decrosslinking of those materials were studied.
Co-reporter:Haruyuki Okamura, Kazuo Shin and Masamitsu Shirai
Polymer Journal 2006 38(12) pp:1237-1244
Publication Date(Web):November 2, 2006
DOI:10.1295/polymj.PJ2006007
Multifunctional crosslinkers having two, three, four and six functionalities were synthesized using a convergent method and were applied to a photocrosslinking system having thermally degradable properties. The multifunctional crosslinkers contained epoxy units and tertiary ester linkages. When the blended films of epoxides/poly(p-vinylphenol) with a photoacid generator were irradiated and followed by baking at relatively lower temperatures (<100 °C), the films became insoluble in solvents. Heating conditions strongly affected the insoluble fraction of the blends. Insoluble fraction of the blended films increased with the number of the epoxy unit of a molecule. The crosslinked films became soluble after prolonged bake at relatively higher treatments (>120 °C). The reaction pathway of the blended system was studied by in situ FT-IR measurements.
Co-reporter:Yeong-Deuk Shin, Akiya Kawaue, Haruyuki Okamura, Masamitsu Shirai
Polymer Degradation and Stability 2004 Volume 86(Issue 1) pp:153-158
Publication Date(Web):October 2004
DOI:10.1016/j.polymdegradstab.2004.04.005
New diepoxy crosslinkers (Cr-1, Cr-2 and Cr-3) containing thermally degradable sulfonate ester linkages were synthesized and characterized. From FT-IR and UV spectroscopic experiments, it was confirmed that Cr-1 and Cr-2 photochemically generated sulfonic acid, while Cr-3 was photochemically stable. Cr-1 and Cr-2 initiated photo-crosslinking reaction with poly(vinylphenol) (PVP), a copolymer of methacrylic acid and ethyl methacrylate (P(MAA-EMA)), and poly(7-oxabicyclo[4.1.0]hept-3-yl)methyl p-styrenesulfonate) (POHMSS). After irradiation at 254 nm, the Cr-1 or Cr-2/polymer blended film became insoluble and the degree of insolubilisation increased with baking at 100–140 °C. Solubilisation due to decrosslinking was observed by baking at higher temperatures (150–200 °C). The crosslinker/POHMSS system showed high efficiency in photo-thermal crosslinking and thermal decrosslinking at high temperatures.
Co-reporter:Haruyuki Okamura;Shogo Toda;Masahiro Tsunooka
Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 17) pp:3055-3062
Publication Date(Web):22 JUL 2002
DOI:10.1002/pola.10394
Photocrosslinkable systems with thermally cleavable properties based on blends of poly(vinyl phenol) (PVP) and diepoxides were investigated. Thermally cleavable diepoxides as crosslinkers were prepared and characterized. As a thermally cleavable linkage, a tertiary ester moiety was incorporated into the crosslinker molecule. PVP/crosslinker blended films containing photoacid generators (PAGs) became insoluble in solvents after UV irradiation and subsequent post-exposure-bake (PEB) treatment. With a rise in the PEB temperature, the insoluble fraction of the irradiated films increased, passed through a maximum value, decreased, and increased again at elevated baking temperatures. The insolubilization profiles of the irradiated films were complicated and strongly dependent on the type of PAG used, the structure of the crosslinkers, and the PVP/crosslinker ratio. A mechanism for the thermal degradation was studied with Fourier transform infrared spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3055–3062, 2002
Co-reporter:Masamitsu Shirai
Progress in Organic Coatings (1 February 2007) Volume 58(2–3) pp:158-165
Publication Date(Web):1 February 2007
DOI:10.1016/j.porgcoat.2006.08.022
Novel UV curing materials which became soluble in solvents by photo/thermal degradation were studied. Three types of systems were designed and prepared, i.e. (a) base polymer/crosslinker blended system, (b) functionalized polymer system, and (c) multifunctional acrylate monomer system. In the base polymer/crosslinker blended system, as a crosslinker, multifunctional epoxy compounds containing tertiary esters of carboxylic acid or sulfonate ester units were synthesized and used in combination with polyvinylphenol. Functionalized polymers bearing epoxy units and thermally degradable linkages in the side chain were prepared. Furthermore, multifunctional methacrylate or acrylate monomers bearing acetal linkages in a molecule were prepared. Photocrosslinking and thermal decrosslinking of those materials were studied.
Co-reporter:Daisaku Matsukawa, Haruyuki Okamura and Masamitsu Shirai
Journal of Materials Chemistry A 2011 - vol. 21(Issue 28) pp:NaN10414-10414
Publication Date(Web):2011/06/09
DOI:10.1039/C0JM04386A
Four types of reworkable dimethacrylates bearing hemiacetal ester groups were synthesized and the UV curing and degradation were studied. UV nanoimprint lithography (UV-NIL) using these monomers was performed and fine line/space patterns were obtained. The shrinkage in height of the UV imprinted pattern was studied in relation to the monomer structure and UV imprint conditions such as light intensity and concentrations of photoradical initiator and chain transfer reagent. The effect of UV imprint conditions on the kinetic chain length of UV cured networks was investigated using size exclusion chromatography of the linear polymers obtained from the degradation of the UV imprinted patterns. A relationship between the kinetic chain length and shrinkage of the UV imprinted patterns was discussed.
Co-reporter:Daisaku Matsukawa, Hiroyuki Wakayama, Kazuyuki Mitsukura, Haruyuki Okamura, Yoshihiko Hirai and Masamitsu Shirai
Journal of Materials Chemistry A 2009 - vol. 19(Issue 24) pp:NaN4087-4087
Publication Date(Web):2009/05/20
DOI:10.1039/B905188K
Difunctional methacrylate monomers having a hemiacetal ester moiety in the molecule were used to prepare a plastic replica of an original mold for imprint lithography. UV curing of the monomers was performed with 365 nm light and photo-induced degradation of the cured resins was performed using 254 nm light.
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