Abstract: This invention relates to radiation curable compositions comprising an alkenyl ether functional polyisobutylene, a cationic photoinitiator, and a miscible reactive diluent selected from specified organic vinyl ether compounds, epoxy functional compounds, or compounds having the formula R8Xb, wherein R8 is a non-silicon containing organic group, X is an organic group containing at-least one acrylate functional group, and b has a value of 1-3. The radiation curable compositions exhibit a low cure energy, have a high moisture vapor barrier, high damping characteristics, and a high refractive index, and provide a barrier to corrosive vapors and have maintained or enhanced modulus, tensile strength, and toughness.

Abstract: This invention relates to radiation curable compositions comprising an alkenyl ether functional polyisobutylene, a cationic photoinitiator, and a miscible reactive diluent selected from specified organic vinyl ether compounds or compounds having the formula R8Xb, wherein R8 is a non-silicon containing organic group, X is an organic group containing at-least one acrylate functional group, and b has a value of 1-3. The radiation curable compositions exhibit a low cure energy, have a high moisture vapor barrier, high damping characteristics, and a high refractive index, and provide a barrier to corrosive vapors and have maintained or enhanced modulus, tensile strength, and toughness.

Abstract: An organopolysiloxane composition is provided including: (A) an organopolysiloxane with hydroxyl groups at both terminals of the molecular chain; (B) an organosilicon compound represented by the general formula shown below: wherein, R2 represents a hydrogen atom, a phenyl group or a halogenated phenyl group, R3 represents a hydrogen atom or a methyl group, R4 represents a monovalent hydrocarbon group, X represents a hydrolysable group, Z1 represents —R5—, —R5O— or —R5(CH3)2SiO— (wherein R5 represents a bivalent hydrocarbon group), Z2 represents an oxygen atom or a bivalent hydrocarbon group, m represents 0, 1 or 2, and n represents 0, 1 or 2; (C) a condensation curing catalyst; and (D) a photopolymerization initiator.

Abstract: A photo-patternable perfluorinated silane sol-gel material is presented that exhibits a high refractive index and propagation losses below 1 dB/cm at the telecommunication wavelengths. The sol-gels are produced with general formula [(CH2)n, R′—Si(O)2]x—[Si(O)4]y—[R′—Si(O)3]z—[R″(CH2)n-M(O)3]w—[R′″(CH2)n—Si(O)3]v where O is oxygen, Si is silicon, M is a metal alkoxyde known to form bonds with organic compounds through oxygen donor ligands, and where , R″ and R′″ are photo cross-linkable groups, and where (CH2)n are alkyl spacers with n being an integer ≧0. The sol-gels can be fabricated to produce complex waveguide structures directly onto silica-on-silicon substrates with low bending losses.

Abstract: The present invention provides solid supports (e.g., glass) and polymer hydrogels (particularly polymer hydrogel arrays present on a solid support) comprising one or more reactive sites for the attachment of biomolecules, as well as biomolecules comprising one or more reactive sites for attachment to solid supports and polymer hydrogels. The invention further provides novel compositions and methods for the preparation of biomolecules, solid supports, and polymer hydrogels comprising reactive sites. The invention also provides for preparation of crosslinked solid supports, polymer hydrogels, and hydrogel arrays, wherein one or more biomolecules is attached by means of the reactive sites in a photocycloaddition reaction. Advantageously, according to the invention, crosslinking of the hydrogel and attachment of biomolecules can be done in a single step.

Abstract: A process for making a self-dispersible, radiation curable coating composition involving: (a) providing a cationic oligomer; (b) providing an epoxy functional monomer; (c) providing a surfactant component; (d) providing a transfer agent; (e) providing a photoinitiator; and (f) mixing (a)-(e) to form the coating composition.

Abstract: Disclosed is a photosensitive polymer comprising pentafluoromethylvinyl ether derivative monomer having the formula: 1

Abstract: The invention concerns the field of polymerization and/or cross-linking reaction catalysis by cationic process of monomers, oligomers and/or polymers. In particular, novel polymerization and/or cross-linking initiator systems comprising at least one onium borate and at least one benzophenone are described to satisfy the ever greater exigencies of productivity and manufacture. The initiators are used in particular for preparing resins and/or composite materials based on an organic and/or silicon matrix or optionally a matrix of acrylic monomers, oligomers, or polymers.

Abstract: A photoactive polymer of the general formula I: in which: P is a photoactive group which can photoisomerise and/or photodimerise; B represents an aromatic or alicyclic group, or B further represents a nitrogen atom or —CR2—; A, C, D each independently of the other represents an aromatic or alicyclic group; M represents a repeating monomer unit in a homo- or copolymer; S1, S2, S3, S4, S5 represent a single covalent bond or a spacer unit; n1, n2 are each independently a positive integer up to 2 with the proviso that n1+n2≦2; R1 is a hydrogen atom, or a straight-chain or branched alkyl residue wherein R2 represents a hydrogen atom or lower alkyl. The photoactive polymers may be used as orientation layers for liquid crystals and in the construction of unstructured and structured optical elements and multi-layer systems.

Abstract: An ocular lens material comprising a copolymer prepared by polymerization with heating of a monomer mixture and/or with irradiating a monomer mixture with ultraviolet ray by means of a molding method, the monomer mixture containing a polysiloxane macromonomer A, a Si-containing alkyl methacrylate B, a hydrophilic monomer C comprising NVP as C-1 and another hydrophilic monomer C-2, another monomer D and a crosslinkable monomer E comprising a crosslinkable monomer E-1 containing at least one group selected from acryloyl group, vinyl group and allyl group, and methacryloyl group, and a crosslinkable monomer E-2 containing at least two methacryloyl groups as main components, wherein (A+B)/C (weight ratio) is 30/70 to 70/30, A/B is 25/75 to 75/25, C-1/C-2 is 50/50 to 100/0, the amount of D is 0 to 20% by weight in the monomer mixture, which has high oxygen permeability, high mechanical strength, excellent surface wettability and low surface frictional property.

Abstract: This invention relates to a dual curing silicone composition with an enhanced depth of cure. This composition incorporates an acylphosphine oxide or diacylphosphine oxide, the compatibility of which with the silicone is promoted through the use of a polar carrier. The composition may also include a second photoinitiator that is different than the acylphosphine oxide.

Abstract: An adhesive composition that includes a mixture of a cationically polymerizable component, an acidic component, and an initiator is provided. Preferably, the initiator comprises an iodonium salt, a visible light sensitizer, and an electron donor compound, wherein the initiator has a photoinduced potential greater than or equal to that of N,N-dimethylaniline in a standard solution of 2.9×10−5 moles/g diphenyl iodonium hexafluoroantimonate and 1.5×10−5 moles/g camphorquinone in 2-butanone. This adhesive composition is cationically polymerizable and is able to bond to hard tissue and cationic restorative materials upon curing.

Abstract: A radiation curable composition contains an epoxy-functional silicone polymer, an iodonium photocatalyst and a non-fluorescing polycyclic aromatic compound containing at least one hydroxy, alkoxy or glycidyl ether substituent bonded to an aromatic carbon atom of the compound.

Abstract: This invention provides a method and material compositions for producing objects containing in whole, or in part, biomedical polymers, especially those having dental use. Microwave sensitive material compositions are injected under pressure into a mold, the mold containing a replica of a body tissue or tissues. While hydraulic pressure is maintained on the material, a microwave source emits metered electromagnetic energy for hardening the material in the 3-dimensionally defined space. For dental and other applications, the mold making, injection and hardening are done sequentially to rapidly produce an object which accurately fits the mold.

Abstract: There is provided a radiation-curable coating composition containing oligomers that each have two end groups X1 and X2, wherein the end groups X1 and X2, which may be the same or different, are a photoinitiator group or an adhesion promoter group. The coating composition may exclude the presence of non-reactive photoinitiator groups and non-reactive adhesion promoter groups, each of which would fail to covalently bond itself to an oligomer backbone.

Abstract: The invention provides an organic/inorganic hybrid material with low optical loss at telecommunications wavelengths. Energy curable compositions of the present invention include condensed silica nanoparticles, a fluorinated silane coupling agent, an energy curable silane coupling agent, and a halogenated monomer or oligomer. Polymeric materials of the present invention include condensed silica nanoparticles having a mixture of organosilane coupling agents covalently bound to the exterior surface of the nanoparticles and a halogenated solid polymer matrix, wherein the mixture of organosilane coupling agents includes an at least partially fluorinated coupling agent, and a coupling agent covalently bound to the polymer matrix. The materials of the present invention are useful in making low-loss optical devices for telecommunications applications.

Abstract: Radiation-curing coating systems which contain a silanized silica, where the silane is hexamethyldisilazane, 3-methacryloxypropyltrialkoxysilane and/or glycidyloxypropyltrialkoxysilane as the silanizing agent. The radiation-curing coating systems can be used for coating derived timber boards, solid wood, wood veneers, parquet, decorative papers, decorative films, thermoplastics and thermosetting plastics, mineral and polymeric glasses, metals (for example aluminium, high-grade steel, phosphated, chromated and galvanized steel sheets, copper), lacquered surfaces, printing inks and leather.

Abstract: Enhancement of the rates of cationic polymerizations initiated by onium salts has been achieved through the use of oligomeric and polymeric electron-transfer photosensitizers derived from a polymerizable compound substituted with a polynuclear aromatic group, including epoxides, oxetanes, and ethylenically unsaturated compounds. The polymerizable compound is substituted with residues derived from anthracene, naphthalene, perylene, pyrene, fluorene, carbazole, indole, benzocarbazole, acridone, phenothiazine, and thianthrene, particularly carbazole.

Abstract: By blending novel organosiloxane polymers of the invention with a crosslinking agent and a photoacid generator, photo-curable resin compositions are formulated which can be exposed to radiation in a broad wavelength range and readily form a thin film without oxygen attack. From the compositions, fine patterns having improved dry etching resistance can be formed. Cured coatings of the compositions having improved substrate adhesion, heat resistance, and electrical insulation are suitable as a protective film for electric and electronic parts.

Abstract: The invention concerns a polymerization and/or crosslinking method under electron beam and/or gamma radiation for compositions based on monomers, oligomers and/or polymers with organic functional groups. The invention is characterized in that the crosslinking and/or polymerization is carried out in the presence of an initiator capable of being activated under electron beam and/or gamma radiation comprising a boron derivative of formula (I) M+B(Ar) 4 wherein: M+, a unit bearing a positive charge, is an alkaline metal selected among those of columns IA and IIA of the periodic table; Ar is an aromatic derivative, optionally substituted by at least a substituent selected among a fluorine radical, a chlorine radical, a linear or branched alkyl chain, which itself can be substituted by at least a fluorine atom.

Abstract: An alkylsiloxane-containing epoxy resin composition can suitably be used as water-repellent agent or a water-repellent coating to be advantageously applied to areas that are apt to be brought into contact with solutions and substances containing one or more than one components that can damage the film forming property and the adhesion of an ordinary water-repellent agent. The resin composition comprises at least an alkylsiloxane-containing epoxy resin having two or more than two alkylsiloxane groups and two or more than two cyclic aliphatic epoxy groups in a molecule and a cationic polymerization catalyst.

Abstract: A photo-curable resin composition comprising (A) an organosiloxane-bearing polymer comprising recurring units of formula (1): 1

Abstract: The invention relates to novel cyclic siloxane compounds of the following general formula (I): in which: n=0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 preferably 1, 2, 3, 4, 5; A=H or C1-C15 alk(en)yl, C3-C15 cycloalk(en)yl, C6-C12 aryl, C8-C18 alkaryl, where, in the said radicals, in each case one or more C atoms can be replaced by O, C═O, O(C═O), SiR2 and/or NR, R being an aliphatic radical with 1 to 7 C atoms, in which one or more C atoms can be replaced by O, C═O, and/or O(C═O); B=E or a linear, branched or polycyclic aliphatic- or aromatic-groups-containing hydrocarbon radical which links 2 to 10 of the cyclosiloxane radicals defined above, less B, to one another and contains 2 to 50 C atoms and additionally 0 to 30 other atoms from the group O, N, S, P, Si, Cl, F, Br, I and from which correspondingly 1 to 9, preferably 1 to 4 of the above defined cyclosiloxane radicals, less B, are pending; E=A or a polymerizable group G—Q—L, where o

Abstract: The invention disclosed includes a coating composition for siliceous surfaces. The coating includes at least one component from the group consisting of poly(alkoxy)silane, poly(halo)silane, alkoxysilane, halosilane, and mixtures thereof and a catalyst compound which generates a proton to hydrolyze the component when exposed to radiation. Preferably, the catalyst is a photo-acid. The invention also includes a method of coating the optical fiber. The aforementioned coating is applied to an exterior surface of the fiber. A proton is generated to promote the hydrolysis of the component. The invention further includes a method of accelerating adhesion between the exterior surface of the article and the coating. The inventive coating is applied to the surface of the fiber and the coating is exposed to a radiation source.

Abstract: A radiation-curable release composition comprises: (a) from about 50 to about 100 parts by weight of an organopolysiloxane of the formula (I)  wherein R is CH2═CH—C(O)—O—CH2—CH(OH)—CH2—O—CH2—CH2—CH2—, n is 5 to 15, and p is 50 to 150; (b) from 0 to about 50 parts by weight of one or more organopolysiloxanes comprising organopolysiloxanes selected from the group consisting of those of formulae (II) and (III)  wherein R is CH2═CH—C(O)—O—CH2—CH(OH)—CH2—O—CH2—CH2—CH2—, m is 1 to 10, and q is 151 to 300; and  wherein R is CH2═CH—C(O)—O—CH2—CH(OH)—CH2—O—CH2—CH2—CH2—, and r is 20 to 500; (c) from 0 to about 10 parts by weight of an organopolysiloxane of formula (IV)  wherein R is CH2═CH—C(O)—O—CH2—CH(OH

Abstract: A photosensitive composition for optical waveguides comprising of an organic oligomer, a polymerization initiator and a crosslinking agent, the organic oligomer being a silicone oligomer represented by the following formula (1), wherein X denotes hydrogen, deuterium, halogen, an alkyl group or an alkoxy group; m is an integer from 1 to 5; x and y represent the proportion of respective units, and neither x nor y is 0; and R1 denotes a methyl, ethyl, or isopropyl group; a production method thereof, and a polymer optical waveguide pattern formation method using the same.

Abstract: A radiation-curable composition for an ink base, ink composition, outer primary composition, buffering material or matrix material for fiber optics includes, in the uncured state, a secondary amino or tertiary amino silicone-containing additive.

Abstract: In one aspect the invention provides an energy efficient polymerization method comprising irradiating a polymerizable composition and a photoinitiator with a source of essentially monochromatic radiation where the photoinitiator and the wavelength of the radiation source are selected such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than about 1000 M−1 cm−1 and such that the photoinitiator absorbs at least two percent of the actinic radiation incident on the coating. In another aspect the invention provides energy efficient methods of polymerizing polymerizable compositions and crosslinking crosslinkable compositions by irradiating the respective compositions with a low power source of essentially monochromatic radiation. The low power energy sources have an input power of less than about 10 W/cm.

Abstract: A high energy radiation-curable composition comprising a partial hydrolysis-condensation product of (A) a mixture of an alkoxy containing organopolysiloxane and alkoxysilanes and (B) a multifunctional acrylate, and a resin molding coated with the composition. The composition forms coatings of superior curability, water repellency, water resistance, oil repellency, transparency, flexibility, and scratch resistance, especially on resin moldings.

Abstract: A ceramer composition is provided that comprises a plurality of colloidal inorganic oxide particles and a free-radically curable binder precursor. The free-radically curable binder precursor comprises a fluorochemical component that further comprises at least two free-radically curable moieties and at least one fluorinated moiety. By virtue of the inclusion of the fluorochemical component, the ceramer compositions of the present invention can be used to provide ceramer composites and ceramer composite structures with excellent stain, oil and/or water repellency characteristics as well as a high level of abrasion resistance and hardness.

Abstract: Low solvent and solvent-free silicone release coatings may be prepared with varying COF levels by incorporating a very high molecular weight, substantially non-reactive organopolysiloxane into a conventional curable release coating. By supplying the COF additive in the form of a relatively low viscosity master batch, adjustment of COF may be made by the coating applicator. Very low COF values can be obtained from tin-free, solvent-free coating systems, while at the same time, the coatings have very low extractables.

Abstract: Blends of epoxy-functional silicone polymers with vinyl ether monomers and alkylphenol compounds plus an effective amount of a suitable iodonium photocatalyst provide a radiation-curable silicone release coating composition.

Abstract: The invention relates to &agr;-ammonium alkenes, iminium alkenes and amidinium alkenes in the form of their tetraaryl- or triaryl-alkylborate salts that can be converted photochemically into amines, imines or amidines, and to a process for the preparation thereof. The invention relates also to compositions polymerisable or crosslinkable under basic conditions comprising such &agr;-ammonium alkenes, iminium alkenes or amidinium alkenes in the form of their tetra- or tri-arylalkylborate salts, to a method of carrying out photochemically induced, base-catalysed reactions, and to the use of such compounds as photoinitiators for base-catalysed reactions.

Abstract: Disclosed is a positive photoresist composition comprising an alkali-soluble polysiloxane containing as a copolymerization component at least a structural unit represented by the following formula (I′) and a positive photoresist composition comprising an acid-decomposable polysiloxane containing as a copolymerization component at least a structural unit represented by the following formula (I″): wherein L1 represents at least one divalent linking group selected from —A—OCO—, —A—COO—, —A—NHCO—, —A—NHCOO—, —A—NHCONH—, —A—CONH—, —A—OCONH— and —A—S—, A represents a single bond or an arylene group, X represents a divalent linking group, and n represents an integer of 1 to 6.

Abstract: The invention relates to a crosslinked resin and to its application in the manufacture of ceramic or glass patterns at the surface of a substrate.

Abstract: Cyclopentadienylplatinum (IV) compounds having C7-20 aromatic radical substitution on the cyclopentadienyl ring have been found to impart enhanced cure speed and shelf-life stability to irradiation-curable silicone mixtures.

Abstract: Selectively colorable compositions and a method for forming selectively colored polymeric bodies using such compositions are disclosed. In accordance with the invention, a selectively colorable polymerizable composition comprising a leucobase color former is irradiated with light of a particular wavelength and specific intensity for a specified duration. Exposure to actinic radiation cures the composition and activates the color former. Exposure to higher dosages of actinic radiation can bleach the composition. The irradiation dosage can be varied to selectively color the polymeric body whereby the resultant color of any particular area depends on the exposure dose received at that location. By varying the dose, a polymeric body can be prepared having distinctly colored elements at specific locations.

Abstract: A film suitable for use as the light-modulating unit of an SPD light valve, the film comprising a cross-linked polymer matrix and having droplets of a liquid light valve suspension distributed in the cross-linked polymer matrix, the liquid light valve suspension comprising particles suspended in a liquid suspending medium, wherein the matrix and the droplets each have a refractive index within a range of from about 1.455 to 1.463 and wherein the refractive index of the droplet and the matrix components of the film are preferably matched as closely as possible within RI 0.005 of each other.

Abstract: A coating powder comprising a macrocyclic oligomer and a ring-opening polymerization agent is applied to an article, fused, and converted to a linear polymer at a temperature of from about 160 to about 400° C. The powder has the low melt viscosity and friability of a thermoset powder but is converted at high fusing temperatures to a tough coating having the good impact resistance and good elongation of a thermoplastic powder. The oligomer is a polyester, polycarbonate, polyamide, polyimide, polyamideimide. The article may be coated electrostatically or in a fluidized bed.

Abstract: Tackified compositions comprise a curable polydiorganosiloxane oligourea segmented copolymer which has alternating soft polydiorganosiloxane units and hard diisocyanate residues, the diisocyanate residue being the diisocyanate minus the —NCO groups. The units are connected together by urea linkages and the copolymer has end groups that are reactive under free radical or moisture cure conditions, and silicate resin. Also provided are pressure-sensitive adhesives, hot melt adhesives, and vibration damping composites, vibration damping constrained layer constructions, a bi-directional vibration damping constrained layer constructions, vibration damping shaped articles as well as a method of vibrationally damping an article and processes for producing curable vibration damping material.

Abstract: A curable composition which comprises the following two components: (I) a vinyl polymer having at least one crosslinkable silyl group represented by the general formula (1) given below, and (II) an epoxy resin or a polyether polymer having at least one crosslinkable silyl group; —[Si(R1)2−b(Y)bO]m—Si(R2)3−a(Y)a  (1) {wherein R1 and R2 each represents an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms, or a triorganosiloxy group represented by the formula (R′)3SiO— (in which R′ represents a monovalent hydrocarbon group containing 1 to 20 carbon atoms and the three R's may be the same or different) and, when there are two or more R1 or R2 groups, they may be the same or different; Y represents a hydroxy group or a hydrolyzable group and, when there are two or more Y groups, they may be the same or different; a represents 0, 1, 2 or 3; b represents

Abstract: The present invention relates to iodonium salts containing urethane groups of reduced crystallization tendency, to a process for their preparation, and to their use for the radiation curing of cationically curing compositions.

Abstract: A process for the addition of compounds containing silicon-bonded hydrogen to compounds containing aliphatic unsaturation and compositions suitable for said process. The process is activated by actinic radiation and is conducted in the presence of a platinum complex having one cyclopentadienyl group that is eta-bonded to the platinum atom and three aliphatic groups that are sigma-bonded to the platinum atom and a free-radical photoinitiator that is capable of absorbing actinic radiation such that the hydrosilation reaction is initiated upon exposure to actinic radiation. The invention also provides compositions for use in the aforementioned process.

Abstract: Radiation-crosslinkable elastomeric compositions containing: (a) an elastomeric polymer containing abstractable hydrogen atoms in an amount sufficient to enable the elastomeric polymer to undergo crosslinking in the presence of a suitable radiation-activatable crosslinking agent; and (b) a radiation-activatable crosslinking agent of the formula: wherein: X represents CH3—; phenyl; or substituted-phenyl; or substituted-phenyl with the proviso that any substituents on the substituted-phenyl do not interfere with the light-absorbing capacity of the radiation-activatable crosslinking agent and do not promote intramolecular hydrogen abstraction of the radiation activatable crosslinking agent; W represents —O—, —NH—, or —S—; Z represents an organic spacer selected from the group consisting of aliphatic, aromatic, aralkyl, heteroaromatic, and cycloaliphatic groups free of esters, amides, ketones, urethanes, and also free of ethers, thiols, allylic grou

Abstract: The invention relates to modified cationic photoinitiators which exhibit a reduced tendency to crystallize, to a process for reducing the crystallization tendency of cationic photoinitiators, and to the use of the photoinitiators of the invention for the radiation curing of cationically curing compositions. The inventive cationic photoinitiators have the formula (IV): [R1—I—R2]+X− where R1 is a radical R2 is a radical in which Ar is a monovalent aromatic hydrocarbon radical and D being a radical and the remaining variables are defined herein.

Abstract: The invention relates to a method for producing silicone foams from silicone masses containing ammonium carbonate or ammonium hydrogen or alkali hydrogen carbonates and UHF-active substances, by means of ultra-high frequency waves.

Abstract: A radiation curable composition contains an epoxy-functional silicone polymer, an iodonium photocatalyst and a non-fluorescing polycyclic aromatic compound containing at least one hydroxy, alkoxy or glycidyl ether substituent bonded to an aromatic carbon atom of the compound.

Abstract: The invention relates to a liquid curable resin composition comprising: (A) a polyfunctional (meth)acrylic compound containing at least three (meth)acryloyl groups in the molecule, (B) a reaction product of an alkoxy silane compound having a polymerizable unsaturated group, an urethane bond group, and an organic group represented by the following formula (1), wherein X is NH—, —O—, or —S— and Y is an oxygen atom or a sulfur atom, and when X is —O—, Y is a sulfur atom, with silica particles, (C) a radiation curable acrylic resin comprising a carboxyl group in its molecule, of which the Tg is 50 or higher, (D) a radiation polymerization initiator, and (E) a non reactive solvent. The invention further relates to the coating obtained after evaporation of the solvent, and to the cured coating after irradiation.

Abstract: Enhancement of the rates of cationic polymerizations initiated by onium salts has been achieved through the use of oligomeric and polymeric electron-transfer photosensitizers derived from a polymerizable compound substituted with a polynuclear aromatic group, including epoxides, oxetanes, and ethylenically unsaturated compounds. The polymerizable compound is substituted with residues derived from anthracene, naphthalene, perylene, pyrene, fluorene, carbazole, indole, benzocarbazole, acridone, phenothiazine, and thianthrene, particularly carbazole.

Abstract: A positive type photoresist composition comprising an alkali-soluble or acid-decomposable polysiloxane containing repeating structural units represented by formula (I): wherein L represents at least one divalent connecting group selected from the group consisting of —A—NHCO—, —A—NHCOO— and —A—NHCONH—, wherein A represents a single bond, an alkylene group or an arylene group; X represents a single bond or a divalent connecting group; and Z represents either a group represented by or a group represented by wherein Y represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, an atomic group represented by Y may be straight-chain, branched or cyclic, R represents a hydrogen atom or an acid-decomposable group, l represents an integer of from 1 to 3, and m also represents an integer of from 1 to 3.